At a little after nine Central Standard Time on the night of Monday, April 13, 1970, there was, high in the western sky, a tiny flare of light that in some respects resembled a star exploding far away in our galaxy. At the Manned Spacecraft Center, near Houston, Texas, the glow was seen by several engineers who were using a rooftop observatory to track the Apollo 13 spacecraft, which had been launched two days before and was now a day away from the moon and two days from a scheduled moon landing. One of the group, Andy Saulietis, had rigged a telescope to a television set in such a way that objects in the telescope’s field of view appeared on the screen. Above, the sky was clear and black, like deep water, with occasional clouds making ripples across it. Saulietis and his companions—who, incidentally, had no operational connection with the Apollo 13 mission but were following it for a related project—had lost sight of the spacecraft, two hundred and five thousand miles away. However, they had been watching the booster rocket that had propelled the spacecraft out of earth orbit and was trailing it to the moon; the booster had appeared as a pinprick of light that pulsed slowly, like a variable star, for it tumbled end over end as the result of dumping its fuel, and the sunlight glinted off it with varying intensity. Shortly before nine, the observers on the rooftop at Houston had lost track of the booster, for the pinprick had been almost at the limit of the resolving power of their equipment. Suddenly, near the middle of the TV screen, a bright spot appeared, and over the next ten minutes it grew to be a white disc the size of a dime. The rooftop watchers had no communications link with the Mission Control Center, about two hundred yards away—a large building consisting of two linked wings, with operations rooms in one, offices in the other—and they had no reason to connect the flaring light with the spacecraft or to be concerned with the safety of its crew—Captain James A. Lovell, Jr., of the United States Navy, who was in command, and the pilots for the command and lunar modules, John L. Swigert, Jr., and Fred W. Haise, Jr., both civilians. It was to be some time before either Mission Control—which had no telescopic means of watching Apollo 13—or the astronauts themselves realized that one of the ship’s two oxygen tanks had burst, spewing into space three hundred pounds of liquid oxygen, which meant the loss of half the craft’s supply of this element for generating electricity and water. The oxygen came out in one big blob, and in gravityless space it formed a sphere that expanded rapidly; the sunlight made it glow. In ten minutes, it was thirty miles in diameter. Then the white disc slowly disappeared—though traces of it were observed an hour later through a more powerful telescope in Canada.
Saulietis and the others assumed the white spot to be a defect in their television set, which had been flickering and blipping badly, so they went home to bed and thought nothing about the incident until the next morning. They were not the only ones who failed to grasp the situation. After two successful lunar landings, which had been preceded by two Apollo flights around the moon, no one at the Space Center was thinking in terms of accidents. Later, some of the first interpretations of what had happened would center on the notion that the spacecraft had been struck by a meteor—a borrowing from science fiction, for Jules Verne’s space capsule in “From the Earth to the Moon” had almost been hit by one while it was approaching the moon. No one believed that there could be any flaw in the craft itself. Yet in the Mission Control Center, where dozens of automatic pens were scribbling data radioed from Apollo 13, at the time of the explosion the pens stopped writing for almost two seconds—a “drop out of data” indicating a major problem with either the electrical system or the system of transmitting data from the craft. No one noticed.
Inside the Mission Control Center’s Operations Wing, a chunky, monolithic three-story structure as white and silent as a block of ice—the geometric representation of an intelligence brooding on far-off space—the flight controllers were at least as thoroughly cut off from the world around them as sailors below decks on a ship at sea. There were no windows, as there are none on the lower decks of a ship—and, in a sense, the Operations Wing really was the lower decks of a ship, the upper deck being a couple of hundred thousand miles away in space. Astronauts are more like officers aboard a large ship than like solitary heroes, and that may account for some of the difficulty many people have in comprehending their roles. In the spacecraft and the Mission Control Center combined, there were about as many astronauts and flight controllers as there are officers aboard a big vessel, and they worked together as closely as officers below decks work with officers on the bridge. In fact, one of the controllers, the Flight Director, in some respects might have been regarded as the real skipper of the spacecraft, for although the relationship between the astronauts and the ground crew was a delicate, interdependent one, the astronauts usually did what he advised, particularly in an emergency. Though the flight controllers were on earth, they had, by means of telemetry—data radioed constantly from the spacecraft—more information about what was happening aboard than the astronauts themselves had. The walls of the Mission Operations Control Room, on the third floor of the Operations Wing, were the same color as the inside of the command module—gray. Five big screens at the front of the room might have been windows looking out into space: the middle screen showed the earth on the left and the moon on the right, with a bright-yellow line representing the spacecraft’s trajectory as it lengthened slowly between them. And some of the consoles at which the flight controllers sat duplicated equipment aboard the spacecraft.
The flight controllers, most of whom were in their twenties and thirties, sat in four rows. At the moment, they were relaxed—even bored. The first fifty-five hours of the flight had gone so smoothly that they had once sent word to the astronauts that they were “putting us to sleep down here.” One team of flight controllers had been reduced to commenting on the number of “thirteens” that cropped up; for example, the time of launch in Houston—the official time for the flight—had been 13:13, or in our terms 1:13 p.m. About the only event requiring the controllers’ close attention since Apollo 13 left earth orbit had been a small rocket burn the day before, called a “hybrid transfer maneuver,” which had aimed the spacecraft for its target on the moon, the Fra Mauro hills—and, incidentally, had taken it off a free-return trajectory, the safe path most previous Apollos had followed so that in the event of trouble the spacecraft would, without navigational adjustment, swing around the moon and head back to earth. Now, a couple of minutes before nine, one of the flight controllers, the Retrofire Officer, whose responsibility it was always to have a plan ready, in case of trouble, for bringing the astronauts home, sent word to the Flight Director that another bridge was about to be burned: via a pneumatic-tube system connecting the consoles, he dispatched a routine memorandum to the effect that the spacecraft was nearing the spot where it could no longer reverse its direction and return directly to earth if anything went wrong.
There were a couple of dozen controllers on duty, of whom only about half were directly involved with the running of the spacecraft at any given time. In the front row, which was called the Trench, sat three Flight Dynamics Engineers, the men responsible for the ship’s trajectory: from right to left, the Guidance Officer, or GUIDO, who was the chief navigation officer; the Flight Dynamics Officer, or FIDO, who plotted the trajectory and made sure the spacecraft followed it; and the Retrofire Officer, or RETRO, who was in charge of the spacecraft’s reëntry into the earth’s atmosphere. Most of the second row, behind the Trench, was taken up by the Systems Operations Engineers, who monitored the equipment inside the spacecraft: in the center, the EECOM, who looked after the electrical, environmental, and other systems in the command module, where the astronauts rode; next to him, the LM Systems Officer, or TELMU, who did the same thing for the lunar module, in which the astronauts would land on the moon; and then two Guidance and Navigation Control Officers—one, the GNC, for the command module, and the other, the CONTROL, for the lunar module—who were in charge not only of the guidance and navigation equipment in the two modules but of the propulsion system as well. To their left was the Spacecraft Communicator, known—from the old Mercury-capsule days—as the CAPCOM, the only man who could talk directly with the astronauts, and to his left was the Flight Surgeon. Behind the Flight Surgeon, in the third row, was the Instrument and Communications Officer, or INCO, who was responsible for the radios and telemetry transmitters aboard the spacecraft. Finally, in the center of the third row—a good vantage point for keeping an eye on everyone else—there was the Flight Director, the ship’s earthbound co-captain. (In the fourth row sat administrators, Public Affairs Officers, and so on.)
There were four shifts, or teams, of flight controllers—White, Black, Maroon, and Gold—and at that moment the White Team was on duty. The controllers talked to each other over an intercom hookup called the loop. To cut down on what they called loop chatter, which had a way of sounding like random thoughts popping up in a single individual’s mind, the controllers referred to each other by their acronyms or abbreviations: FIDO, GUIDO, RETRO, CAPCOM, EECOM, and so on. Apollo 13 was just plain “Thirteen.”
On April 13th, about half an hour before the white spot was seen by Saulietis and his companions, the flight controllers were watching a television show, which the astronauts were broadcasting from the spacecraft, and which was projected on one of the big screens at the front of the room. As it happened, none of the three major networks carried the telecast—though they would show tapes of it later—and it concluded ten minutes before the occurrence of the episode that could have made it as dramatic as any performance in history. As the flight controllers leaned back in their chairs to watch, they thought the astronauts seemed happy. Captain Lovell, the commander, who was forty-two, and who had graduated from Annapolis in 1952, ten years before he became an astronaut, was cameraman and announcer for the show; he first panned the camera around the gray interior of the command module, a cone whose base was almost thirteen feet in diameter and whose height was ten and a half feet. It was about as big as the inside of a small station wagon, though the astronauts, who could float about, found it roomier than a similar space on the ground. Lovell was resting on the center couch. Beneath him was the service module, which contained, among other things, the electrical system, including the two big oxygen tanks. The cylindrical service module, with the conical command module at one end, formed a single pointed unit, in front of which was the lunar module, giving the spacecraft a total length of almost sixty feet. Above Lovell’s head, at the apex of the cone, was a round hatch leading through a short tunnel to the lunar module. Lovell had flown in space three times, and this was the second time he had set out for the moon; he had circled it, in December, 1968, as a member of the Apollo 8 mission. This may have accounted for a certain bland professionalism he displayed as master of ceremonies. He began, “What we plan to do for you today is start out in the spaceship Odyssey and take you on through from Odyssey in through the tunnel into Aquarius.” Odyssey was the code name for the command module, and Aquarius for the LM. (The latter was named for a song in the musical “Hair,” which Lovell—who was Special Consultant to the President’s Council on Physical Fitness and Sports—had not seen. When he caught up with the show later, he walked out.)
Lovell aimed the camera at Haise, the lunar-module pilot, who was hovering by the hatch, ready to lead the way into the LM. Clothed, like the others, in white coveralls, Haise was hard to make out, because the television relay was none too sharp. Haise, a native of Biloxi, Mississippi, is a slight man with dark-brown hair and a square jaw, who speaks with a slight drawl. Although he had become an astronaut only four years before, and this was his first spaceflight, he had made enough of an impression so that Lovell and the other Apollo 8 astronauts had seen fit to name a crater on the moon after him. Haise was not particularly busy at the moment—the LM was not scheduled to be powered up until they were in lunar orbit, a day hence—so Lovell had persuaded him to act as guide for his tour, and now Lovell, holding the TV camera at arm’s length, followed Haise as he swam through the tunnel into the LM. There Haise demonstrated various pieces of equipment to be used on the moon, including a rectangular bag (called the Gunga Din) that he and Lovell would wear inside their helmets, so that they could drink while they walked about the Fra Mauro hills. “So if you hear any funny noises on television during our moon walk, it is probably just the drink bag,” Lovell said. Haise was doing something in the middle of the LM now, but the flight controllers had trouble seeing exactly what it was. The CAPCOM asked if he was opening the food locker, and the flight controllers laughed, because Haise had a well-known penchant for food. Haise said that he was rigging his hammock for sleep, and the CAPCOM replied, “Roger. Sleeping and then eating.”
Leaving Haise in the LM, Lovell went back through the tunnel and, in the command module, sought out the third member of the crew—Swigert, the command-module pilot. “There he is! We see him!” the CAPCOM said, and, sure enough, there he was, seated before the ship’s controls in the middle one of the astronauts’ three seats, surrounded on three sides by nine dashboard panels. Swigert, a sharp-faced, sharp-eyed man, who was born in Denver, Colorado, in 1931, and had become an astronaut with Haise in 1966, was too busy just then to do more than smile at the camera. He did not take a big part in the television show. This was his first spaceflight, as it was Haise’s, but he felt himself to be under more pressure, because he had been merely the backup command-module pilot, and had been officially assigned to the flight only the day before it left, after the prime crew had been exposed to German measles and it was discovered that the prime command-module pilot was susceptible. Lovell had worked with Swigert for two days without letup before agreeing to take him on the flight. (Swigert had been in such a rush that he hadn’t thought about completing his 1969 income-tax return, due in four days, until he was a quarter of the way to the moon.) During the first fifty-five hours of the flight, Swigert had run into a few minor difficulties; for instance, he had been having trouble reading the quantity gauge for one of the oxygen tanks, which had gone off-scale on the high side, and earlier that day the CAPCOM had told him he could expect frequent requests from the ground to turn on the fans in the tank to stir up the oxygen—what is called a “cryogenic stir”—for the purpose of obtaining accurate quantity readings. Now, as the television show continued, Swigert found a moment to hold the camera and trained it on the commander; Lovell appeared on the screen for the first time. A tall, sober-looking man whose face at times breaks into a broad grin, Lovell demonstrated a tape recorder that could play a number of songs, among them “Aquarius” and the Richard Strauss “Thus Spake Zarathustra” theme used in the film “2001: A Space Odyssey.” At length, the CAPCOM broke in to suggest that Lovell conclude the program. The commander replied, “Roger. Sounds good. This is the crew of Apollo 13 wishing everyone there a nice evening, and we’re just about ready to close out our inspection of Aquarius and get back for a pleasant evening in Odyssey. Good night.” It was then 9:00 p.m.
As the show ended, Lovell joined Swigert at the controls in the command module, sitting in the left-hand seat, and helped him copy down an instruction from the CAPCOM for rolling the spacecraft to the right in order to photograph a comet named Bennett. In front of them were two red lights labelled “Master Alarm,” which would flash on if the spacecraft computer detected a serious malfunction, and over their heads was an array of yellow caution lights to indicate minor malfunctions. One of these flashed on at five minutes past nine, and so did a similar one in Houston on the console of the EECOM, who was in charge of monitoring, among other items, the spacecraft’s equipment for generating electricity. The EECOM on duty was Seymour Liebergot, a thirty-four-year-old electrical engineer from California State College at Los Angeles. The yellow light warned of low pressure in a hydrogen tank in the service module, which was crammed with equipment; in addition to the main propulsion system, there was the system for generating water and electricity, of which the balky hydrogen tank was a part. The generating system was simple and efficient: hydrogen and oxygen reacted inside units called fuel cells to generate electricity and, at the same time, to produce most of the spacecraft’s water. Liebergot wasn’t worried by the alarm, because the system was redundant: there were two hydrogen tanks, two oxygen tanks, and three fuel cells, and if anything went wrong gases could be routed from any of the tanks to any of the cells.
Liebergot had been manipulating the hydrogen quantity in the tanks all along, so the hydrogen warning was almost routine. It did, however, preëmpt the circuits of the warning system, so that a problem with the oxygen supply would not turn on a yellow light, as it was supposed to. To make sure he was getting the right information, Liebergot asked the Flight Director, Eugene Kranz, to get the astronauts to stir the hydrogen in both tanks; even though Kranz was only four feet behind him, Liebergot had to get his attention over the loop. Kranz, who was thirty-six, and is a graduate of St. Louis University, had been with NASA since 1960. As the Flight Director on duty, he was in charge of everything that went on in the Control Room and therefore had to approve all requests of this sort before they could be relayed to the spacecraft. Also, as Chief of the Flight Control Division, he was in over-all charge of the controllers. Liebergot now asked that in addition to the hydrogen tanks the oxygen tanks be stirred, for, like Swigert up in the CM, he had been having trouble all day getting an accurate reading on the quantity of Oxygen Tank No. 2.
If Liebergot had been able to look inside the two oxygen tanks, he would not have wanted to risk disturbing them. They, together with the rest of the electrical-generating system, were inside Bay 4 of the service module—one of six compartments that ran the length of the twenty-five-foot module. The interior of Bay 4, a place of silvery insulation and golden wires, was divided into compartments. The three fuel cells were in the forward one; the two hydrogen tanks were in the rear; and in the middle were the oxygen tanks, two silvery spheres, twenty-six inches in diameter and made of a tough nickel-steel alloy called Inconel, which were strong enough to contain the oxygen under nine hundred pounds of pressure per square inch. They had an outer and an inner shell, and the space between was filled with insulation—some of it inflammable. On top of each tank was a capped dome that sealed an opening for pipes and for wires that brought electricity to instruments inside the tank—fans, heaters, and the sensors for the quantity, temperature, and pressure gauges.
What would have alarmed Liebergot if he had been able to look inside the tanks was that the wires in Oxygen Tank No. 2 were largely bare of insulation. This situation, attributable to both imperfect design and human inattention, had existed for more than two weeks—since March, when a ground crew at Cape Kennedy had piped liquid oxygen into the tanks in a countdown demonstration test. The oxygen and the hydrogen were cryogenic, or cooled to a liquid state, in order to keep them at sufficiently low volume so that they could be compactly stored; the temperature of the oxygen at filling time was two hundred and ninety-seven degrees below zero Fahrenheit. When the test was over, the engineers had been unable to get the oxygen out of Tank No. 2. This trouble may have arisen because the cap on top of the tank had been jolted so that pipes and wires inside were loosened—which may also be why Liebergot was now having trouble with his tank readings. In any event, the ground crew had tried to force the oxygen out by turning on the heaters and fans inside the tank; the fans would stir up the oxygen and the heaters would warm it to make it expand, thus forcing it out. The heaters were left on for eight hours—a longer period than such heaters had ever been on before—and during that time nobody was aware that the temperature inside the tank was getting higher and higher. The ground crew was not worried, because they knew there was a thermostatic safety switch in the tank’s interior that was supposed to turn the heaters off if the temperature rose above eighty degrees, the safe limit. So confident were the designers of the equipment that although they provided a thermometer to give a temperature reading from inside the tank, this did not register above eighty-five degrees. What the designers had overlooked, though, was that the switch they specified was built to operate on the twenty-eight-volt current of the spacecraft’s power supply, and that when the tanks were tested at Cape Kennedy they were powered from a sixty-five-volt supply. Consequently, the safety switch on Tank No. 2 failed. (The designers had overlooked the deficiency because they thought the switch would be kept cool during tests by being immersed in the supercooled oxygen.) As was determined much later by experimentation with similar equipment under similar circ*mstances, the switch undoubtedly fused shut under the current overload and couldn’t turn off the heaters. The fact that it had failed could have been discerned had any of those in charge noticed that an electrical gauge on the equipment showed that the heaters were still drawing current for hours after they should have turned off, and thus were still in operation; apparently, no one looked at the gauge. The heat might well have gone up to a thousand degrees—enough to burn the insulation off the wires. After that, if electrical equipment inside the tanks was turned on and the wires happened to come close together, a spark could pass between them.
When Liebergot requested the cryogenic stir, Kranz, the Flight Director, said he would like to hold off awhile on relaying the message, because he wanted to give the astronauts time to settle down after their TV show. Kranz, a big-boned, trim man with fair hair cropped so close that from certain angles it was barely visible, often suggested a tough Marine Corps unit commander. He was wearing a flashy, iridescent white vest, in honor of his team of flight controllers, the White Team. In about an hour, Kranz’s team would be handing over control to the Black Team, and already Black Team controllers had begun to arrive and draw up chairs so that they could look over the shoulders of their White counterparts.
Kranz was delaying action on Liebergot’s request until Haise had returned to the command module. To determine whether he had started back yet, Kranz asked the TELMU, who monitored the data on the LM, whether the LM’s hatch was still open. The TELMU thereupon checked the electrical-power readings for the command module, from which the inert LM was drawing the small amount of power it needed. By pressing a combination of buttons in front of him, each of the flight controllers could throw onto a small television screen in front of him any one of two hundred and fifty charts giving data on the spacecraft’s condition; these were prepared by computers on the ground floor of the Operations Wing, where the telemetry was received. There had been a slight drop in the power output, so the TELMU guessed that the LM’s hatch was closed—since the lights that turned on when it opened were now drawing no electricity—and therefore that Haise was on his way back to the command module. Accordingly, Kranz told the CAPCOM to radio to Swigert, the command-module pilot, the message to stir the tanks. Swigert, looking up into the apex of the command module, could see Haise coming back through the short tunnel, and that was about all he could see, for he was hemmed in by over five hundred dials, buttons, knobs, switches, and thumbwheels. Most of them were guarded by little U-shaped wickets, lest an astronaut bump against one inadvertently. Swigert’s movements were gingerly; as the new crew member, he was especially anxious to perform as he should. When he received Liebergot’s message, he pressed four switches to his right. In the Control Room, Liebergot sat forward to get a better look at the screen on his console, which would now show the pressure, quantity, and temperature readings of the tanks.
Nothing much happened for sixteen seconds. Then, inside Oxygen Tank No. 2, an arc of electricity shot between two naked wires. In the next twenty-four seconds, the arc heated the oxygen, and its pressure rose rapidly. Because the hydrogen-tank low-pressure signal had preëmpted the system, no caution lights flashed, and because Liebergot was concentrating on the readings for the hydrogen tanks, which were on the right side of his television screen, he didn’t notice the rapidly increasing numbers in one of the oxygen-pressure columns, three inches to the left of where he was looking. During the time the pressure in the oxygen tank was increasing, the only person in the Control Room to notice that anything was wrong was William Fenner, the GUIDO, who saw what he called an “event”—an unexpected number—on his console. It signalled what he called a “hardware restart,” which meant that the spacecraft computer had found a problem and was going back over recent events to find out where the trouble lay. It never found out, but the restart provided Kranz with a false trail to follow later.
On the basis of recorded data, of evidence brought back by the astronauts, and of extensive post-mission analyses, it is possible to reconstruct with a fair degree of certainty what happened during this two-minute period. At the end of twenty-four seconds, the oxygen pressure had blown the dome off the top of the tank. The layer of insulation between the inner and outer shells of the tank undoubtedly caught fire, with flames, fanned by the rush of escaping oxygen, spewing as from a blowtorch all over the inside of Bay 4 of the service module. The silvery sheets of Mylar insulation—heat-resistant but nevertheless inflammable—lining the inside of the bay probably caught fire, and the resulting gases blew out the bay’s cover, which was one of six panels making up the service module’s external hull. It was lucky the panel blew out when it did, for if the pressure had been allowed to build up much more, the command module itself, plugging the front end of the service module like a cork, could have blown off instead. Later, in describing what happened, NASA engineers avoided using the word “explosion;” they preferred the more delicate and less dramatic term “tank failure,” and in a sense it was the more accurate expression, inasmuch as the tank did not explode in the way a bomb does but broke open under pressure.
Whether called an explosion or a tank failure, such an event is less noticeable in space than it would be on the ground, where air transmits sound and shock waves. Therefore, none of the astronauts were aware that one of the oxygen tanks had ruptured. Nevertheless, each of them was instantly made aware, in one way or another, that there had been an untoward event. First, Swigert reported over the radio that they seemed to have a problem. His voice was so calm that the CAPCOM, Jack R. Lousma, could not tell which of the astronauts was speaking, and Lousma knew the astronauts well, because he was an astronaut himself. What had disturbed Swigert, as he later recalled it, was not so much the sound of a perceptible bang as the sensation of a sort of shudder that ran through the spacecraft. He could not make a precise distinction, he said, because the borderline between feeling a vibration and hearing it is sometimes imperceptible. What he felt may in fact have been not unlike the disconcerting shudder that first puzzled some of the passengers aboard the Titanic as the ship scraped against an iceberg. Swigert was strapped into his seat, and so was better able to feel the shudder than Lovell, the spacecraft commander. The latter, who was floating just above his seat, said he had not felt the shudder but had heard a distinct bang. Lovell’s first thought was that the bang had been made by Haise opening a valve in the lunar module. At thirty-six, Haise still looked like the youthful, irrepressible sort of person who might make a loud noise without warning. However, Haise was at this moment emerging from the tunnel, and Lovell could tell by the look on his face that he, too, had been jolted by something. Far from causing the bang, he had been startled when the tunnel shook up and down—a motion he thought ominous, for normally when the tunnel shook it was from side to side. He immediately felt that something fundamental was wrong.
Both Lovell and Swigert thought that the bang—or shudder—had come from the lunar module, and as Haise emerged from the tunnel Swigert shot out of his seat and slammed the command-module hatch shut behind him. Haise scrambled to his seat—the right-hand one—for the master alarm was now sounding in his earphones. Swigert had noticed an amber caution light glowing overhead. It didn’t signal trouble in the oxygen tank, because that alarm system was still tied up by the low-pressure warning in the hydrogen tanks; rather, it signified trouble with the electrical system, the controls for which were near Haise. About this time, the Flight Surgeon, Dr. Willard R. Hawkins, noticed that the pulse readings for all three astronauts had shot up from about seventy to over a hundred and thirty.
The first disaster in space had occurred, and no one knew what had happened. On the ground, the flight controllers were not even sure that anything had. One reason for their ignorance was the imperfect nature of the telemetry from the spacecraft, which could not tell them directly that an oxygen tank had blown up. It could only report what the temperatures and pressures were in the tanks, whether certain voltages were within the proper limits, and whether certain equipment was on or off. This information had to be interpreted before the flight controllers could know what was going on, and the flight controllers were slow to make the correct interpretation, because, like everyone else at NASA, they felt secure in the knowledge that the spacecraft was as safe a machine for flying to the moon as it was possible to devise. Obviously, men would not be sent into space in anything less, and inasmuch as men were being sent into space, the pressure around NASA to have confidence in the spacecraft was enormous. Everyone placed particular faith in the spacecraft’s redundancy: there were two or more of almost everything. Even the flight controllers’ own training contributed to their confidence. For three months before the flight, they had flown the mission over and over in rehearsals called simulations. For these, a team of flight controllers took their places at the consoles in the Control Room while the astronauts got inside simulators—working models of the spacecraft, very much like the Link Flight Simulators that student airplane pilots use. Both groups were connected to computers that had been programmed to create problems likely to come up on the mission. The previous moon flights had gone so well that the flight controllers had complained on an earlier occasion to the men planning the simulations that these were too tough to be authentic. Accordingly, the simulations in preparation for Apollo 13 had dealt only with problems that were considered likely to arise; the controllers hadn’t wasted time on what one engineer called “four-point failures—way-out disasters.”
Before the flight controllers could admit the full scope of the present disaster, they went to great lengths to find explanations that would not involve a major failure of the spacecraft. It took them a quarter of an hour to get a rough idea of what had happened, and about an hour more to admit that the spacecraft was damaged beyond repair. At the outset, Liebergot, the EECOM, wasn’t particularly alarmed. Because he had happened to miss seeing the sudden rise in pressure in Oxygen Tank No. 2, it simply didn’t occur to him that the tank had blown out. There was such a cascade of problems that, not having noticed where they started, he didn’t know where to begin to look for their source. Since he had no reason to think in terms of the oxygen tank in the first place, he had to track the trouble backward step by step all the way through the electrical system. The only clue he had to start with was the electrical warning Haise had reported and a similar light flashing on his own console. When he tracked it down, he found that it signalled what he called “a Main Bus B undervolt.” A main bus is like a set of wall plugs. (Electricians also call it a distribution terminal board.) Electricity from the fuel cells—the generators—was fed into the buses, and then power was tapped out of them by the equipment that needed it. For redundancy, there were two main buses, A and B, and what Liebergot had found was that Main Bus B had suffered a significant drop in power, so that the equipment connected to it, which was half the equipment in the spacecraft, was in danger of failing. Up in the command module, Haise already had a sinking feeling, for, according to the mission rules, both buses had to be operating if the astronauts were to get the go-ahead to land on the moon.
Then there was a moment of relief. Haise saw the warning light above his head flicker out, and down in the Control Room the same thing happened on Liebergot’s console. Lovell reported to the CAPCOM that the power in the bus was back to normal. Over the loop, Liebergot suggested to Kranz that the trouble might not have been an undervolt at all but, rather, a problem with the instruments reporting the problem. In the next hour or so, they came back over and over again to this wishful explanation—what flight controllers call an “instrumentation failure.” Following this false trail, they told each other that perhaps everything was all right after all—though Haise now told the CAPCOM that “a pretty large bang” had been associated with the incident. Oddly, Kranz had not heard the astronauts mention a “bang” before. Now a light flickered on one of the panels on his console to indicate that one of the flight controllers—the INCO, who was in charge of the radios aboard the spacecraft—wanted to talk to him.
The INCO told Kranz about a communications “funny”—an aberration that doesn’t clear up immediately, as opposed to a “glitch,” which is a transitory one. At the time of the bang, the INCO reported, there had been an unexplained change in the width of the radio waves transmitted from the spacecraft: they had suddenly switched from a narrow beam to a wide one. Kranz was still not alarmed. The spacecraft radio was transmitting with the high-gain antenna—a sort of stick with reflectors that had to be aimed as precisely as a rifle—and it crossed Kranz’s mind that since the antenna ran on power from Main Bus B, the undervolt might somehow have caused the change; if that was so, then the funny should correct itself now that the undervolt had. Much later, it became apparent that when the side panel of the service module had been torn off and hurtled into space it hit the antenna, causing a change in the nature of the radio signal.
Less than a minute had passed since the accident. A voice from the spacecraft now said that the bang must have affected the gauge that reported the level of Oxygen Tank No. 2—first it had oscillated between twenty and sixty per cent, but now it was off-scale on the high side. This still did not cause Kranz or Liebergot to think that there might be a problem with the oxygen tank. They had been having trouble with the oxygen gauges all along, and they thought that the same trouble had cropped up once more. It was hard for anyone to get rid of the idea that the instruments were lying to them. Just then, Lovell reported that Main Bus B had no power in it at all and Main Bus A was beginning to show an undervolt, too; that is, one main bus had gone dead and the other was losing power. If both buses died, the command and service modules would be without any electrical power except a small amount available from three storage batteries to be used during the return through the earth’s atmosphere. Liebergot was confused. The two main buses, themselves paired for redundancy, were drawing their power from three redundant fuel cells; if one bus died, there was every reason for the other to hold up. While Liebergot pondered, there was a long silence, broken at last by Lovell, who asked, a little anxiously, “O.K., Houston, are you still reading Apollo 13?”
Lousma replied, “That’s affirmative; we’re reading you. We’re still trying to come up with some good ideas here for you.” Then, putting his hand over the microphone, Lousma said hurriedly to Kranz, “Is there any kind of lead we can give them, or are we looking at instrumentation problems, or have we got real problems, or what?”
About six minutes had passed since the accident.
Over the loop, Kranz asked Liebergot for recommendations. Kranz had once said that the hardest part of being a flight controller was being “the last man in the decision chain.” That occurred, Kranz said, when a problem was passed to a flight controller at the last minute and he had to solve it all by himself; if he made a mistake, he did it in front of the whole world, and possibly jeopardized the mission. This was Liebergot’s situation now. On his telemetry screen, he could produce far more information about the spacecraft’s electrical system than the astronauts themselves had; the trouble was that he had no idea where to start looking. Half of the lights before him were amber, and he recalled that the only other time this had happened was shortly after liftoff during the Apollo 12 mission. He also recalled that on that occasion the spacecraft had been hit by lightning—a recollection that did him no good whatever, since there was no lightning two hundred and five thousand miles out in space. He now set about trying to piece together what he knew. The main question he had to answer was why there had been an undervolt in Main Bus B. Spread out before him on the console was a diagram of the spacecraft’s electrical system. It made a sort of chain, leading from the hydrogen and oxygen tanks to the fuel cells and from those to the buses, and ending with the equipment in the spacecraft that was receiving—or was supposed to be receiving—power, At the moment, they were connected like this (the hydrogen tanks are not shown):
Fuel Cells 1 and 2 were supplying electricity to Main Bus A, which was still working. Main Bus B, however, was drawing its electricity from Fuel Cell 3 alone, and it didn’t take Liebergot long to find out that Fuel Cell 3 had stopped generating power. Then he learned that Fuel Cell 1 was generating no power, either. It looked as if the spacecraft had lost two fuel cells—an unprecedented situation. The spacecraft was getting along solely on the electricity that Fuel Cell 2 was supplying to Main Bus A—and, inexplicably, the power put out by the one remaining good fuel cell was beginning to drop, too, though not yet enough for Liebergot to worry about.
The two apparently dead cells, Liebergot knew, drew their oxygen from the same two tanks, but since the good cell drew its oxygen from them as well, he didn’t give the tanks much thought. There was little reason to, for although the two tanks were not, strictly speaking, redundant—they shared the system of pipes leading to the fuel cells—there were so many safety valves that they might as well have been. They were separated by valves that insured that the oxygen would flow only out of them, and, as a further safeguard, each fuel cell could be cut off from the oxygen by a valve of its own, called a reactant valve. The protection afforded by all these valves was critical, because in addition to fuelling the electrical system and producing water, the two tanks provided all the command module’s oxygen for breathing. (In the cabin, there was a small emergency supply in a tank called the surge tank, and in three one-pound bottles, but this had to be conserved for breathing when the command module plunged alone through the earth’s atmosphere.)
The implication of two dead fuel cells was so staggering in itself that Liebergot couldn’t bring himself to believe that such a state of affairs was possible. At NASA, backups don’t fail. Liebergot was encouraged in his disbelief by the flight controllers’ operating procedure, which required them to make presumptions against such failures—partly because of the admittedly imperfect quality of telemetry. According to the standard procedure, before Liebergot could think about such a thing as the oxygen he had to make sure that the fuel cells really were dead. Perhaps there had been an instrumentation failure, or perhaps there was some other simple explanation. Until he was certain, Liebergot didn’t even report the loss of the cells. “You can’t alarm the crew unnecessarily—you’ll look like a big ass unless you’re sure,” he later said.
One simple explanation that occurred to Liebergot was that the jolt or the bang, whatever it was, at eight minutes past nine had disconnected the two fuel cells from the two buses. He therefore suggested to Kranz that Swigert check on whether the cells were in fact hooked up to the buses. Any connecting or disconnecting that the astronauts did was by means of switches at their consoles; the switches for the cells and buses were in front of Haise but within reach of Swigert, and Swigert now flicked them down and back. (Flight controllers call such flicking “cycling the switch.”) Swigert reported no change in the electricity level of the buses. That meant that the trouble did not lie in anything as simple as broken connections. Liebergot couldn’t make any sense out of it. He wished he could be almost anywhere else. He couldn’t, of course, because, among other things, Lousma kept asking Kranz if there were any more recommendations he could pass on to the astronauts, and Kranz kept asking Liebergot. Liebergot felt rather cornered. He was the one on the spot, and all the electrical engineers in the world couldn’t help him. At length, because it was possible to switch circuits among the fuel cells and buses, he suggested that the astronauts switch the lines from the two dead cells so that each fed the other bus. That way, Liebergot figured, something might develop to give him a clearer picture of what was going on. Also, fuel cells, like flashlight batteries, sometimes worked better if they were changed around. Kranz, however, refused to go along with the suggestion. He had to be cautious, because nobody knew what was wrong and he didn’t want to do anything that might make matters worse. At the moment, all the power in the spacecraft was coming from Main Bus A, and he didn’t want to risk disturbing it. For the time being, Kranz planned to be very deliberate and very methodical about authorizing any changes. Less than seven minutes had passed since the bang.
The only other idea that Liebergot could come up with just then was that in order to keep up the power in the good bus—which was continuing to drop—the astronauts might augment it by feeding into it electricity from one of the storage batteries that were supposed to supply power to the spacecraft during its reëntry through the earth’s atmosphere. There was, it seemed, very little choice; in fact, as Liebergot made the suggestion, he could see on his telemetry screen that the astronauts were already hooking the battery to the bus.
Although the brunt of the difficulties fell on the EECOM, all the other flight controllers were having trouble, too. Their voices over the loop were almost unnaturally calm, but one of them said later that he could tell from their tones that “a lot of stomachs were turning over.” At the moment of the bang, the spacecraft began pitching and yawing about like a depth-charged submarine. Two identical balls set in the dashboard, one in front of Lovell and the other in front of Swigert, appeared to spin erratically. They were the flight-director attitude indicators, or F.D.A.I.s—sort of three-dimensional compasses that showed which way the spacecraft was pointing. Appearances to the contrary, the balls were actually still, as the compass card in a ship’s binnacle is; it was the spacecraft that was doing the turning. The guidance computer in the spacecraft, which normally held it steady by automatically firing sixteen small thruster rockets outside the service module whenever necessary to correct its attitude, had been unable to stop the wobbling. Now Lovell was trying to do so by firing the thrusters manually, using a pistol-grip hand control at the end of the armrest on his couch. He wasn’t having much luck, for the spacecraft kept buffeting and yawing as if something was venting from it and imparting an unwanted thrust. Part of Lovell’s difficulties stemmed from the fact that the sixteen thrusters operated electrically; each of the main buses supplied current to fire half of them, and the eight thrusters dependent on Main Bus B weren’t working. The good bus couldn’t accommodate all sixteen, so Buck Willoughby, the Guidance and Navigation Control Officer, who sat on Liebergot’s right, had to figure out which were the best thrusters to keep operating; he had to make sure that one thruster was working in each direction for the three motions of the spacecraft—up and down, left and right, and roll.
The GNC had a special interest in getting Lovell to steady the spacecraft, for once it had been brought to the right attitude Lovell could set up the gentle roll—the passive thermal-control roll—that kept it turning once every twenty minutes, so that the sun would heat it evenly on all sides. The delicate electronic instruments for guidance and navigation, which were the GNC’s responsibility, and some of the spacecraft’s propulsion systems were especially sensitive to extremes of temperature, and without the regular thermal roll the part of the spacecraft left facing the sun could get as hot as two hundred and fifty degrees, and the part left facing away could get as cold as absolute zero. However, even after Lovell had plugged the thrusters into the buses in the way the GNC thought best, he still couldn’t control the spacecraft’s attitude.
The wobbling was causing other problems as well, for if the spacecraft should happen to roll into certain attitudes the guidance system would lock. The heart of the guidance system was the inertial-measurement unit, a spherical structure in the lower equipment bay, at the foot of the center couch, containing the guidance platform. This was a small metal block that swung freely on three gimbals (like those that keep a ship’s compass level), so that a set of gyroscopes could maintain it in the same position in relation to the stars regardless of the attitude of the spacecraft. Its attitude was electrically relayed to the ship’s guidance computer. The platform had been aligned with certain stars before launch, and it was still aligned with them, for whenever the spacecraft rolled, pitched, or yawed the spinning gyroscopes adjusted the gimbals to keep the platform true. The trouble was that if the three gimbals lined up in certain ways, they would lock and the spacecraft would suddenly be without any reference point in space. In effect, the astronauts would be without a compass. Two or three times, the GUIDO broke in on the loop to tell Kranz that the spacecraft was wobbling toward what he called “gimbal lock,” and at the warning Lovell would point the spacecraft in another direction as hastily as a helmsman would steer a ship away from a reef.
A spacecraft is such a welter of interdependent elements that any one problem can set off a whole series of other problems. The erratic spinning threatened radio communications, because it was next to impossible to keep the antennas aimed at the earth. After the accident, the INCO, the radio controller, who sat at Kranz’s left, had advised shifting from the high-gain antenna—the stick that had been jarred at the time of the bang—to the omnidirectional antenna system, which didn’t have to be pointed so precisely. There were four omnidirectional antennas—big scimitars—spotted around the spacecraft, and normally as it rolled the INCO would keep switching on the one that happened to be on the side nearest the earth. However, with the wobbling, there were times when neither the INCO nor the astronauts knew which antenna was facing the earth. Sometimes communications stopped altogether.
The astronauts were so busy avoiding gimbal lock, checking antennas, and transferring thrusters and other equipment from one bus to the other that they didn’t have a chance to worry much about exactly what sort of danger they were in, and most of the flight controllers didn’t, either. However, one person who had a little time on his hands for worrying was the TELMU, Robert Heselmeyer; because he was a lunar-module man, he was somewhat removed from the situation. Although the LM was powered down, it was using a little electricity drawn from the command module to warm some of its equipment. Heselmeyer sat in silence as he watched the current being fed to the LM go down and down. When the current stopped altogether, he reported the fact to Kranz. Kranz asked Heselmeyer to get back to him later, because he had enough on his hands at the moment. Heselmeyer continued to worry, for it had crossed his mind that if anything serious happened to the command module the astronauts might have to use the lunar module as a lifeboat. He rummaged around on his console for instructions on such lifeboat procedures.
Liebergot, who was still trying to come up with some ideas for reviving the two apparently dead fuel cells, suggested to Kranz that they both be unhooked from the buses, in the hope of separating bad equipment from good. Kranz, who was still being cautious and didn’t want to disturb too many things at once, agreed to disconnect only Fuel Cell 1, which was attached to the good bus A. Part of his thinking was that by isolating one section of the system and then another it might be possible to pinpoint the trouble spot.
In the meantime, Liebergot had requested Lovell to read to the ground all the gauges having to do with the electrical system, to see if they bore out the information that the ground was receiving. Lovell at last got as far as the pressure gauges for the oxygen tanks. “Our Oxygen No. 2 Tank is reading zero. Did you get that?’” he said. Now he floated up out of his seat and pressed his face against the window so that he could look backward toward the service module. He saw a thin sheet of vapor, like a cirrus cloud. “It looks to me that we are venting something,” he reported. “We are venting something out into space.” Now he understood why he had been unable to steady the spacecraft: venting imparted motion as surely as firing a rocket. Thirteen minutes had passed since the bang. To Lousma, the CAPCOM, this was the most chilling moment of the flight. Although Lovell’s voice was calm, what he was saying was as alarming as if a ship’s captain had reported seawater rushing in through the hull—only the astronauts wouldn’t be able to jump into anything as hospitable as even an Arctic sea.
Lovell had no doubt that what he had seen venting was a gas, for in space liquids form hard nuggets, not thin sheets of cloud. And he had a pretty good idea that the gas was oxygen, for he now noticed that not only was the pressure in Oxygen Tank No. 2 at zero but the pressure in Tank No. 1 was dropping as well; it was oxygen from this tank that was leaking into space at the moment. Lovell felt that it was just a matter of time before the command module itself would go dead.
The other flight controllers, unlike the CAPCOM, so far had no such forebodings. As the disaster unfolded step by step, they continually seemed to be left incredulous, one step behind. One reason for their incredulity was that they were missing a key fact: they did not know that the original tank failure had been a violent one. Liebergot was thinking in terms of a gentle leak, and he did not suspect that the rupture of Tank No. 2 had been explosive; what had actually happened was that it had ripped out pipes and valves between the two tanks, in an area called the manifold, where several pipes joined, also causing the oxygen in Tank No. 1 to slowly dissipate. And there was something else the flight controllers didn’t know: the jolt had shut the reactant valves on Fuel Cells 1 and 3—the immediate cause of the power failure, as the valves cut off the flow of oxygen to the two cells. The command and service modules’ electricity would last only as long as oxygen from Tank No. 1 continued to reach Fuel Cell 2. As the oxygen in the service module was what the astronauts were breathing, it had already crossed Liebergot’s mind that the astronauts could be what he called “belly up” in a matter of hours. He couldn’t quite believe it, though, because of his trust in the soundness of Tank No. 1. Kranz gave a short talk to the flight controllers over the loop, urging them to keep cool; guessing would just make matters worse, he said. Optimistically, Liebergot checked to make sure that there was no instrumentation problem.
The astronauts, however, by now had no illusions. Haise said later, “The ground may not have believed what it was seeing, but we did. It’s like blowing a fuse in a house—the loss is a lot more real if you’re in it. Things turn off. We believed that the oxygen situation was disastrous, because we could see it venting. The ground may have been hoping there was an instrumentation problem, but on our gauges we could see that the pressure was gone in one tank and going down in the other, and it doesn’t take you long to figure out what happened.”
The chief reason the flight controllers didn’t tumble to the seriousness of the oxygen problem was that the correct answer was also the unthinkable one. In a number of respects, the situation was like the sinking of the Titanic, another craft that was admired as a nation’s greatest technical achievement. The ship had reputedly been unsinkable, because its hull was divided into redundant watertight compartments, but the collision with an iceberg sliced open too many of them, and it sank. A remark made later by a NASA engineer was strongly reminiscent of the worldwide reaction to the earlier accident: “Nobody thought the spacecraft would lose two fuel cells and two oxygen tanks. It couldn’t happen.” Swigert himself wrote afterward, “If somebody had thrown that at us in the simulator, we’d have said, ‘Come on, you’re not being realistic.’”
For some time, the flight controllers, in their pursuit of solutions, attempted to go in two directions at once: they tried to save the moon-landing mission while simultaneously preparing for the worst. About four minutes after the astronauts reported the venting, Liebergot suggested to Kranz that the crew start powering down the command module, to put less strain on the surviving bus, which was continuing to lose power. Liebergot told Kranz he wanted the astronauts to work their way through the first half of page 5 of what was called the Emergency Power-Down Checklist, which told how to turn off equipment in the proper sequence so that an instrument wasn’t switched off before another one that depended on it. For the moment, the procedure should ease the power crisis. In the spacecraft, the astronauts, to find the proper checklist, had to riffle through twenty pounds of instruction sheets before they got the right ones. Kranz still had no intention of giving up the ship; he made sure no equipment was turned off that would preclude landing on the moon—a possibility he had by no means abandoned. Like Kranz, Liebergot was hoping there was still some way of saving the mission, and as he went about selecting more equipment for the astronauts to turn off he was thinking, in another part of his mind, of possible ways to get more oxygen out of Tank No. 1, so that they could power up again.
The power shortage in the command module was now well beyond the help of the reëntry battery, so Liebergot ordered the astronauts to disconnect it. He had suddenly begun to fear that nothing could be done—that it was just a matter of time before the command module lost all its power. In that case, the astronauts would have to use the LM as a lifeboat to bring them back to earth. Then, just before they hit the atmosphere, they would have to abandon the LM and find some way to fly the dead command module, which was the only part of the Apollo spacecraft with a heat shield capable of withstanding the high temperature of reëntry. If they were to do that, they would need every ampere of electricity in the reëntry batteries. For the same reason, Liebergot urged that the astronauts immediately isolate the supply of oxygen in the surge tank, which was normally connected with the service-module supply. Kranz, who was still thinking in terms of conserving the oxygen in Tank No. 1, wanted to know why Liebergot was ordering the change, and the EECOM replied that he was now more worried about conserving the reëntry oxygen. Kranz saw what he was driving at.
As is bound to happen on any ship with a bad leak, a certain amount of confusion arose. Once, the astronauts turned off a switch that incidentally cut out the gauges for the oxygen tanks; Liebergot quickly got them to turn it back on again. As a result of that contretemps, Kranz requested the astronauts to read back to the ground the dials of all the two hundred and fifty instrument gauges on two of their dashboard panels, for it was imperative that the flight controllers who would be figuring out how to bring the dead command module back through the atmosphere know exactly what the situation was. The astronauts began their reading-back at 9:59 P.M., and it went on for ten minutes.
As additional precautions, Kranz requested that a two-hundred-foot radio antenna (called a deep-space dish) in Australia be added to the global network tracking and communicating with the spacecraft, and that additional computers at the Goddard Space Flight Center in Maryland be what he called “cranked up”—made ready for use. He also telephoned the Real Time Computer Complex on the ground floor of the Operations Wing to ask that an additional big I.B.M. computer be brought onto the line. The computer complex gets its name from the fact that it processes data in “real time,” the flight controllers’ term for instantaneously. And since the average Apollo flight transmits fifty-five million bits of data, this takes some doing. Most NASA engineers believe that it was the United States’ superiority in computers, more than anything else, that gave this country the ability to land men on the moon when it did. The figuring for the first Soviet manned orbital flights may well have been done by teams of men using desk calculators. The technicians in the R.T.C.C. have consoles much like the ones in the Control Room upstairs, and, indeed, many of the computer technicians are the counterparts of—or, as they put it, they “interface with”—the flight controllers. (The interfacing is done over an intercom.) Through a glass partition, the technicians overlook a brightly lit room filled with computers; each computer consists of a couple of dozen cabinets arranged in a rectangle, like refrigerators in a showroom, and, like refrigerators, they need to be kept cool for maximum efficiency. There are four big computers, each capable of handling a flight to the moon, and a fifth, smaller one, used for simulations.
During the non-critical periods of a lunar mission—the sleep periods and the trans-lunar and trans-earth coasts—all the work was ordinarily done by just one computer, designated the Mission Operations Computer, while a second, designated the Dynamic Standby Computer, was hooked up during critical periods—launch, moon-landing, and reëntry—and served as a backup, receiving all the telemetry information from the spacecraft that the main computer was getting, in case it suddenly had to take over the running of the mission. On the night of the accident, the standby computer was of course receiving no data from the spacecraft. In fact, like the third and fourth big computers in the room, it had been farmed out for totally unrelated work, because NASA was having budgetary problems and computer time is very expensive. After all, there had been only a few times in the past when anything had gone wrong with the primary computer necessitating a switch to the backup, and, besides, if an emergency should arise the primary computer could load all the data about the flight into the backup in twenty milliseconds, which was a very short time indeed. Of course, if the primary computer was incapacitated, it might not be able to load the backup at all. Now Kranz wanted to rectify the situation; he had had enough trouble with backups that night.
As Kranz and Liebergot went about their preparations for the worst, they clung to their faith in the spacecraft’s recuperative powers. Kranz said later, “We were still hoping to come up with the right configuration of tanks, fuel cells, and buses, and fly out of the woods with the oxygen in Tank No.1.” He held on to this hope in spite of the fact that the pressure in the tank had dropped from nine hundred pounds per square inch, which was normal, to only three hundred. Liebergot at last recommended that the heaters and the fans for Tank No. 1 be turned on, so that the heat could increase the pressure and the flow of oxygen into the fuel cell. Liebergot studied his telemetry screen. He saw a sudden jump in the amount of current leaving the good bus, and knew that the fans and heaters were on. He did not, however, see any compensating jump in the oxygen pressure; in fact, it was continuing to drop at about the same rate. If anything, the drop was a little faster; the heat almost certainly accelerated the leak. As he watched, the pressure dropped three pounds per square inch, and this made Liebergot pessimistic once more. He said to Kranz, “You’d better think about getting into the lunar module and using the LM systems.”
Forty-seven minutes had passed since the accident. Kranz now turned his attention to the lunar module. He told Heselmeyer, the TELMU, to get some men started figuring out the minimum power-up of the LM needed to sustain life. Kranz wasn’t yet through with the command module, however. He asked Liebergot if he had any more suggestions for restoring the oxygen pressure. Liebergot had not, but he canvassed some of his associates—each of the flight controllers was backed up by a team of experts in the Staff Support Rooms, just outside the Control Room—and one of them came up with the idea that the oxygen leak might not be in the tanks at all but, rather, in one of the fuel cells, Fuel Cell 3 seemed like a good candidate, since it had been the first to fail. Liebergot immediately called Kranz and suggested that the astronauts close that cell’s reactant valve, and so cut it off from the tanks. If the associate was right, the leak would stop. It was the last hope for a simple way out. The reason nobody had suggested shutting the reactant valve earlier was that it was an irreversible act: the fuel cell would be permanently out of service, and there would be no possibility of landing on the moon. Kranz had at last stopped thinking about a lunar landing. However, Haise, on whose side of the spacecraft the reactant-valve switches were, had no intention of taking an irrevocable step that would abort a four-hundred-million-dollar mission all by himself—his own pessimistic evaluation of the situation to the contrary—and, accordingly, he asked the CAPCOM to repeat the order, to make sure there was no mistake. It would have saved him some uncertain moments if he had known the valve was already shut—and had been since the bang—but then nobody knew that. Liebergot gazed at his electronic screen to see what effect isolating the fuel cell would have on the oxygen leak. It would take a while to find out. In fact, it took longer than he expected, because Haise, reluctant to perform this irrevocable act, had to be given the instruction a third time before he flicked the switch for the valve. After an interval, Liebergot was able to determine that the oxygen was still going down at the same rate. At last, Kranz and Liebergot were face to face with the possibility that they were dealing not with a leak but with some sort of explosion that had knocked out the entire oxygen system. At last, they were compelled to accept the fact they had resisted for so long—that their main craft’s redundancy had failed them. Fortunately, that craft was better prepared than most sinking vessels. NASA had provided it with the ultimate in redundancy—a whole other craft.
Some time later, when Kranz was asked whether he had ever feared for the lives of the astronauts, he replied, “Yes and no.” Then he added, “I guess the answer is no, because I have worked with the lunar module more than any other Flight Director. I had the utmost confidence in the LM and in the flight controllers. I knew that the life-support system was good, the communications were good, and the guidance system was good, and that it could make long rocket burns. I was sure it would prove to be a reliable spacecraft.”
Once again, Kranz was more confident than his flight controllers, for Heselmeyer, who, as TELMU, was in charge of the LM’s electrical and environmental system, was not at all sure that the LM, which was designed to support two men for about two days, had enough consumables to support all three astronauts during the entire journey back to earth. “Consumables” was NASA’s term for the fuel, water, and power that the spacecraft consumed and the oxygen and water that the astronauts consumed, A less euphemistic term might have been “essentials.” It looked as though the TELMU was going to have to make the LM’s consumables last three men for four days, because the Retrofire Officer, Bobby Spencer, who was in charge of emergency-return plans, and who had sent Kranz the note just before the accident that the spacecraft was close to the point where it could no longer return directly to earth, was talking now more and more in terms of going home around the moon. In the interval since he had sent the note, the spacecraft had travelled about three thousand miles. The moon was now only forty-five thousand miles away, and the earth five times that distance behind the spacecraft. When the spacecraft left the earth, it had been travelling at about twenty thousand miles an hour, to escape the planet’s gravity, but as it rose higher above the earth its speed slowed—like that of a tossed-up ball near the top of its rise—to a little over two thousand miles an hour. Now it was about to pick up speed again as it fell toward the moon. If the direction couldn’t be reversed, the TELMU was going to have to stretch the LM’s human consumables threefold and its power twofold.
Like everyone else at NASA, those who were concerned with the LM’s consumables had never dreamed that a command module would go completely dead, let alone do so at the point where it had the farthest possible distance to travel back to earth. (The only worse time for the accident to have occurred would be when the astronauts were on the moon, in which case the command module would have been without its lifeboat.) One flight controller later made much the same observation as Swigert: “This particular situation was so far down the line that it was exceedingly unlikely, and if anyone had asked us to simulate it ahead of time we would all have said he was being unrealistic.” (For much the same reason, there hadn’t been enough lifeboats aboard the Titanic, and the passengers had had no boat drill and so didn’t know how to use them.) NASA engineers had been relying for some time on the fact that they could use the LM as a lifeboat in an emergency, but they had not paid much attention to what they called “the lifeboat mode.” The few simulations of such a problem they had run had been short-term affairs, because they had always assumed that if anything should happen to the command module the astronauts could repair it and be back inside it in a few hours. Aside from some tests a year earlier at the time of Apollo 9, which didn’t quite cover the present situation, no one had ever experimented to see how long the LM could keep men alive—the first thing one needs to know about a lifeboat.
In fact, the lifeboat mode was considered such an unlikely eventuality that ordinarily during the long coast to the moon, when the lunar module was inactive, the LM’s consoles in the Control Room were not manned. By a lucky chance, a TELMU—Heselmeyer—happened to be present at the time of the bang (he had come in to supervise what was known as a “LM housekeeping”), and a few minutes later Kranz had come on the loop to say that he wanted the LM consoles manned around the clock from then on. Heselmeyer’s initial estimate of the LM’s consumables was so chilling that he called the RETRO and tried to talk him into doing a direct abort—aiming the spacecraft toward the earth and blasting home with the big rocket in the service module. Theoretically, it could still be done. A direct abort could take as little as a day and a half, which would be much better from the TELMU’s point of view than a trip around the moon, which he estimated would take about four days.
This conversation took place over a secondary loop—one of several telephone hookups that the flight controllers could talk on among themselves without interrupting the main loop of the Flight Director. The Retrofire Officers were not happy about the TELMU’s request. There were two RETROs now, for Spencer, the one on duty, had been joined by the Lead Retrofire Officer, Charles Deiterich, who would have the chief responsibility for planning the route back. Deiterich—a tall, laconic man with a droopy mustache, who was a graduate of the University of St. Thomas in Houston and had joined NASA in 1964—told Heselmeyer that at the moment the spacecraft was so close to the moon’s gravitational pull that in order to blast the command module straight home the lunar module would have to be jettisoned, because the main rocket was not strong enough to reverse the direction of the entire spacecraft. Liebergot, who was listening in on this conversation, now said that he could not approve any plan that meant getting rid of the LM. Deiterich added another argument against the direct abort: the spacecraft was getting very close to the point at which a maximum burn of the main service-module rocket not only wouldn’t reverse the spacecraft’s direction but would simply slow it so that it crashed into the moon. And—assuming that point hadn’t been reached quite yet—if for any reason the big rocket couldn’t be brought up to full thrust, the spacecraft would crash into the moon anyway. As Deiterich listened to the conversation from the spacecraft, he wondered if the rocket could be fired at all, in view of the electrical failure. Heselmeyer went back to considering ways of stretching the LM’s consumables over the estimated four days. To get some help, he put in a call to the Spacecraft Analysis Team (SPAN), a group of engineers in a nearby Staff Support Room who were in constant touch with the prime contractors of the spacecraft—for the LM, the Grumman Aerospace Corporation in Bethpage, New York, and for the command and service modules the North American Rockwell Corporation in Downey, California. At Grumman and North American, there were subsidiary SPAN groups in touch with a number of subcontractors; Heselmeyer’s questions were referred to, among others, technicians at the Hamilton Standard Division of the United Aircraft Corporation at Windsor Locks, Connecticut, the subcontractor for the LM’s environmental control subsystem. (Through this cross-country network, the SPAN engineers would get the flight controllers answers to about a hundred and fifty questions; the wires were already humming between the SPAN room in Houston, the SPAN room at North American, and one in Boulder, Colorado, at the Beech Aircraft Corporation, the subcontractor for the hydrogen and oxygen tanks in the service module.)
Before altogether ruling out the direct abort, Deiterich got the technicians downstairs in the R.T.C.C. to run several possible direct-abort trajectories through their computers, and he passed on a list of seven potential landing sites to the Recovery Operation Team, which was in charge of picking up the astronauts when they splashed down. The Recovery Officers, who were in a glassed-off room to the right rear of the Control Room, were even worse prepared for the emergency than the TELMUs. Because of the success of previous spaceflights, NASA had felt justified in sticking to its timetable of gradually lessening the number of rescue ships. During the Mercury and Gemini programs, when astronauts were orbiting the earth, there had been twelve or so recovery ships stationed around the world at such intervals that no matter where the spacecraft came down there would be a ship within a few hundred miles. However, as spacecraft began going all the way to the moon the number of ships had been reduced, on the theory that in the event of trouble there was more chance to guide a spacecraft to a specific landing site, fewer degrees of latitude on which to spread out the ships, and more time to dispatch a recovery force to meet it; airplanes could drop frogmen to open the capsule’s hatch at any point on earth in a matter of hours. No one seriously believed that a crippled spacecraft falling from the moon might need more than frogmen to meet it. By the time Apollo 11 made the first landing on the moon, the number of recovery sites had been cut down to four—what Recovery Officers called the Mid-Pacific Line, the West-Pacific Line, the Atlantic Ocean Line, and the Indian Ocean Line. By the time of Apollo 13, all four of these stations still existed in the minds of Recovery Officers, but only one of them, the Mid-Pacific Line, had any ships at it. When the Recovery Officers were told that they might have to have a rescue force at any one of seven places within as little as thirty-six hours, they swung into action. First, they called the Department of Defense to see if any United States Navy recovery ships happened to be near any of the targets; they also surveyed “non-dedicated” Navy ships and merchant shipping around the world for what they called “ships of opportunity”—a hair-raising idea at NASA, where nothing is supposed to be left to chance. Twelve countries volunteered ships. The nearest ship of opportunity to the Atlantic Ocean Line turned out to be a carrier, the U.S.S. America, which had just left Puerto Rico and couldn’t get to the site until twenty-four hours after a splashdown there.
An hour and nine minutes after the bang, the White Team handed over control of the spacecraft to the Black Team. Some minutes before this, Kranz had announced over the loop that the TELMUs and Recovery Officers who were working on plans for a direct abort back to earth could forget it—they did not know what shape the main rocket in the service module was in, and they had more confidence in the LM’s main rocket, the Descent Propulsion System. The spacecraft would be going around the moon. There was relief in the Recovery Room, if nowhere else.
Kranz had decided to go ahead with the change of shift despite the crisis, because he felt that he had gone as far as he could and that it was time for a fresh team. Flight controllers take great pride in handing over to a new team on time, regardless of the circ*mstances. As Chief of the Flight Control Division, Kranz had spent a lot of time training the controllers to achieve what he called “uniformity of decision” from one shift to the next, so that handovers would be smooth, and so that Mission Control would speak in a consistent way to the astronauts. Each type of flight controller had its leader—a Lead RETRO, a Lead GUIDO, a Lead EECOM, and so forth—who reported directly to Kranz, and Kranz saw to it that the men who performed the same job on different teams shared offices, so that the four RETROs, for example, would come to know each other and each other’s way of doing things extremely well. For the same reason, Kranz encouraged all his flight controllers to be well acquainted, and he believed them to be an even closer group than the astronauts (against whom they sometimes played touch football), for whereas the astronauts were divided into a number of three-man Apollo teams, the flight controllers—more than a hundred of them, including associates—flew all missions together.
One of the most difficult arts for flight controllers to master, Kranz felt, was the ability to turn a problem over to someone else when a fresh approach was called for. As Liebergot handed over his console to the new EECOM, he felt his throat tighten up so that he could barely talk—a reaction he says he is likely to have immediately after an emergency. He thought he was lucky that his voice hadn’t cracked before. He felt like a Jonah, however, as he walked away from his console, reflecting that major electrical problems always seemed to turn up when he was around: he had been on duty when Apollo 10 lost a fuel cell, and he had been present when Apollo 12 was hit by lightning. He would have felt even more like a Jonah if he had known that the routine cryogenic stir he ordered had triggered the tank failure which, of course, was in no way his fault. After he found out, he was heard to remark that if he had just let things be the oxygen tank would have blown up on the next EECOM.
Liebergot followed Kranz and the rest of the White Team down to a meeting room on the second floor, one of the Staff Support Rooms. There Kranz and his men spent the rest of the night going over the events of the last hour to see what more they could learn from them, and planning what to do next to terminate the mission safely. (A Public Affairs Officer at the time referred to this task as “looking toward an alternate mission”—as though the astronauts had just taken it into their heads to go somewhere other than to the moon.) The Black Team picked up so smoothly where the White Team had left off that the astronauts in the spacecraft were unaware of the change of shift. The new Flight Director, Glynn Lunney, continued Kranz’s efforts to power down the command module while simultaneously seeking ways to restore the pressure in the good oxygen tank. On the admittedly unlikely theory that the leak might be in Fuel Cell 1, Lunney ordered its reactant valve closed. (Again, as in the case of Fuel Cell 3, the valve already was shut.) As before, Haise asked to have the order confirmed and reconfirmed. After he had shut the valve and found that it made no difference, Haise decided that the time had come to abandon ship. “Right about then, it was quite apparent to me that it was just a question of time before the command module was going to be dead,” he said later. “So I kind of lost interest in my position there and headed for the lunar module.”
As Haise moved through the tunnel into the lunar module, he felt as if his world were turning over. One reason was that the two craft were joined together top to top, so that the direction that had been toward the floor in the I command module was toward the ceiling in the LM. There were no lights, except for a flashlight he had brought with him. While the inside of the command module was a cone, the interior of the lunar module was a cylinder laid sideways—though almost unrecognizable as such because of consoles and cabinets jutting with sharp angularity from the walls. Since the LM was designed for only two men, its cabin was smaller than the command module’s, and where the third astronaut would fit was hard to figure out. The dashboard panels, much smaller in area than those of the command module, had many of the same instruments, among them the two flight-director attitude indicator balls, a red abort light, and a computer keyboard. There were no seats, and each of the astronauts had to stand, gripping the hand controls for the thruster rockets, like a sailor at the wheel of a ship, Two triangular windows were canted downward and to the side, so that the astronauts could look down at the moon’s surface as they landed, but the windows were placed just wrong to give Haise a view back along the spacecraft toward the damaged service module.
Haise had to get things running in the LM. He found three checklists for powering it up under various circ*mstances, but none of them fitted the present situation, because all three were based on the assumption that the LM would be receiving power from the command module. The Flight Director asked the TELMU if he had any checklists that would help Haise. After a search of several minutes, the TELMU came upon a set of instructions for starting the LM up on its own batteries. Beyond this, however, the routine checklists, compiled in preparation for a lunar landing and based on the assumption that there was plenty of time for each step, were long and complex; following all the steps on the simplest one would take two hours, and the CAPCOM had just broken the ominous news that there was only about fifteen minutes’ worth of power left in the command module. Since there was no checklist that met the particular situation, Haise and the TELMU improvised one. They had not been trained to do such a thing in any prescribed manner, but they found they were so familiar with the spacecraft that they could do it very smoothly—a facility that was about all anyone would have to rely on for the next several days. The TELMU jumped back and forth among the different checklists in front of him, dropping an item here and picking one up there. He told Haise to omit powering up the LM’s main rocket, which wouldn’t be needed for some time, but urged him to get the guidance system started right away, so it would be ready when the coördinate numbers for the guidance-platform alignment were transferred to it from the command module. While the TELMU was juggling all these items in his mind, he received a call from the EECOM, who urged that Haise turn on the LM’s cabin oxygen right away, for the command module’s supply was about to be cut off.
All these preparations for the worst didn’t prevent the Flight Director from taking one final crack at saving the ship. Just as Kranz had looked to Liebergot for encouraging signs, Lunney looked to his EECOM, who similarly kept dashing his hopes. The Flight Director had noticed signs of life in the temperature and pressure gauges for Oxygen Tank No. 2—the one that had ruptured—and he now asked the EECOM whether it was possible that the tank still contained oxygen.
“Not likely, Flight,” the EECOM answered.
A few minutes later, the Flight Director took a new tack: “EECOM, are you satisfied that both of these oxygen tanks are going down and we’re past helping them?... Is it possible that if we got power to Main B we could get Oxygen Tank No. 2 powered up, and up in pressure?”
The EECOM replied, “We don’t think that is a possibility, Flight.”
Nevertheless, the EECOM suggested that the astronauts turn on the fans in Oxygen Tank No. 2—the same action that had precipitated the bang. It made no difference.
“We’ve got to get them into the LM, Flight,” the EECOM said, and the Flight Director said to the CAPCOM, “Get them going into the LM. We’ve got to get the oxygen on in the LM.”
Lovell went to join Haise in the lunar module, leaving Swigert alone in the command module. Swigert turned off most of the command module’s thrusters and the pumps for the fuel cells. Almost the only things that were left on were the cabin lights, the radio, the guidance system, and the heaters and fans inside the remaining oxygen tank. In the Control Room, the Guidance and Navigation Control Officer said to the Flight Director that he hoped the heaters in the command module’s guidance system could be left on even after everything else had been turned off. Those heaters had never been switched off during a flight, and if the electronic components of the guidance system became too cold there was no assurance that they would work in approximately four days’ time, when they would be needed to guide the command module through the atmosphere. The power for the heaters would have to come from the LM. The Flight Director said that he would see what could be done but that he was sure the TELMU would not want to spare the electricity.
The guidance computer was still on, because there was one more service it could perform before the command module went dead—that of lodestone for the guidance system in the lunar module. The platform alignment had to be transferred from one to the other. In the command module, Swigert read off the gimbal angles of the three gyroscopes—the degrees of roll, pitch, and yaw. The command and lunar modules were not perfectly in line with each other, so these numbers had to be revised. Because Lovell was getting bleary, and it was essential to have the numbers right, he asked the GNC in the Control Room to do the figuring for him. When he at last punched the corrected numbers into the LM’s guidance computer, he felt he had passed the first major milestone on the way home. The transfer of the guidance platform alignment brought life to the LM like a fire in a cold hearth.
It was done not a moment too soon, for Swigert reported another amber caution light in the array shining overhead—the Main Bus A undervolt warning. Quickly, Swigert switched off the last of the thrusters and the guidance computer. He even turned off the small platform heaters, for the GNC had just told the Flight Director he was willing to gamble that the cold would not damage the electronic equipment.
The very last item to be shut off was the reactant valve on the remaining fuel cell. When this had been done, Swigert, as pilot of the command module, told the two other astronauts that getting home would be up to them now. The command module was completely dead. The supreme achievement of American technology had broken down utterly. All that was left was a spacecraft whose very complexity made it harder to handle, plus a group of fight controllers and three astronauts who were themselves products of the vast bureaucratic machine that had produced the malfunctioning spacecraft. On the face of it, this might appear to have made it all the more difficult for them to get outside the situation and impose their will on the wayward spacecraft. However, the accident had also demolished most of the technological appurtenances, such as checklists and flight plans, which substitute a sort of delayed time for immediacy, and also much of the automatic equipment aboard the spacecraft which performed tasks that earlier mariners would have performed for themselves. Now the flight controllers and the astronauts were no different from any other sailors facing disaster at sea. They would do a lot better by themselves than their elaborate paraphernalia had done by them.
About three hours had passed since the bang.
To the people flying Apollo 13, the flight after the accident seemed to break into three distinct periods: first, the time until the closing down of the command module; then the twenty-hour period during which the astronauts rounded the moon; and finally the trip back to earth, culminating in the descent through the atmosphere. The second period was one of deep uncertainty, and during it the flight controllers had to decide in the broadest terms what was to be done.
In the Staff Support Room on the second floor, which was equipped with TV screens and headsets for transmitting information from the spacecraft and from the communications loops, Kranz’s team continued to do long-range planning that the Black Team, upstairs, was too busy to do. Astronauts, who like to think that they are the ones who fly spacecraft, afterward called Apollo 13 “a ground show.” The flight controllers themselves were to call it “a RETRO’s mission,” for it was the Retrofire Officer, assisted by the Flight Dynamics Officer, who was in charge of the trajectory home. RETROs and FIDOs, who sit next to each other in the Trench, work together so closely that it is sometimes hard to tell them apart. On the way to the moon, when the FIDO is planning the outward-bound trajectory, the RETRO is supposed always to have a plan ready to bring the spacecraft home in the event of trouble, but on the way home the RETRO takes charge of the trajectory and the FIDO helps him out by keeping track of where the spacecraft is. At the moment, the Apollo 13 spacecraft was on a trajectory that would carry it around the moon and swing it back toward the earth, which it would approach after more than four days, but because the spacecraft had left its free-return trajectory it would miss the earth by some forty thousand miles.
Deiterich, the Lead Retrofire Officer, ran through some of the possible alternatives for correcting the course. The first was that the astronauts could make a small burn with the lunar module rocket to alter the present course just enough to put the spacecraft back on a free-return trajectory, so that after rounding the moon it would hit the earth. However, the TELMUs instantly objected—the Lead TELMU, William Peters, had just joined the meeting—because the burn would not speed up the spacecraft by much and they were averse to any plan that would leave the astronauts dependent on the LM’s consumables for almost four days. The consumables picture had brightened somewhat; the Spacecraft Analysis Team had reported back that there was more than enough oxygen in the LM to last the approximately four days it would take to get back to earth. However, electricity and water were still in doubt.
Deiterich moved on to his next proposal, which was to do nothing now but, rather, wait until about eighteen hours had passed and the spacecraft had rounded the moon, and then blast the LM’s rocket for all it was worth. This scheme delighted the TELMUs, because it would get the astronauts home in about two and a half days, but the Control Officers—the Lead CONTROL, Harold Loden, had just joined the meeting—wouldn’t hear of it. Since each flight controller had his own interest to protect, such discussions (there would be more in the next few days) tended to sound a little like the conflicting voices inside the head of a person with a difficult decision to make. The CONTROLs, who were in charge of the LM’s guidance and propulsion systems, argued that this second proposal would mean burning the LM’s fuel almost to the point of depletion, leaving no margin of safety for mid-course corrections.
Deiterich’s third proposal was a combination of the first two: he suggested making a small burn in the next hour or so to put the spacecraft on a free-return trajectory into the earth’s atmosphere (though it would not be precise enough for a landing) and then making a second burn after the spacecraft had rounded the moon, to refine the craft’s aim and speed it up. Several of the flight controllers opposed this proposal, because it was complicated; nobody liked the idea of doing two burns when one might suffice. The TELMUs, for instance, said that two burns would require twice as much electricity and water as one—every time a burn was made, equipment had to be powered up and kept cool—and, of course, electricity and water were in short supply. Deiterich, however, preferred the third proposal, because it was the most flexible; it left the option of doing a rocket burn after the spacecraft had rounded the moon, and the burn could be a fast one or a slow one, depending on the circ*mstances then. Kranz approved, and the plan was adopted. One part of the plan did make everyone feel better, and that was getting the spacecraft back on something approaching a return trajectory right away. Lovell said later that his main concern at this point was to get at least into the earth’s atmosphere, because he felt that it would be better for the ship to burn up like a meteor than not to come back at all. Deiterich and the other flight officers in the second-floor Control Room wanted to do the first burn at once, but the men in the spacecraft asked for time. The burn was put off for over an hour—until almost three in the morning.
The Black Team, which was now flying the mission, was glad to have the extra time, too, for a rocket burn is a little like coming about in a sailing ship, in that it demands plenty of preparation. Like coming about, a rocket burn is a change in course. Before the RETRO could plan the burn, therefore, the FIDO had to find out precisely where the spacecraft was—for the venting had changed the craft’s speed, knocking it out of the trajectory it was supposed to be following. Radio and radar tracking stations around the globe took readings of the spacecraft’s position every ten seconds, but these in themselves did not show exactly where the craft was, or where it was going. The raw data had to be processed by computer, and the technician down in the R.T.C.C. who was doing this was having trouble, because the radar data were what he called “noisy” (the points of information were scattered and ambiguous), so it was difficult for the computer to work out vectors—a vector being a point in space where the spacecraft was known to have been. Whenever the technician was confident that he had a reliable new vector, he signalled the FIDO, who found it on his electronic screen. The succession of vectors constituted the spacecraft’s actual trajectory. Tonight, the FIDO felt he needed more than the usual number of vectors before he had what he called “a good hack on the trajectory.” The spacecraft, he found, was wandering farther and farther off its original course.
When the FIDO felt he had a good hack on the trajectory, he passed the information on to the RETRO, on his left, and the GUIDO, on his right. The three dynamics engineers in the Trench were so close to the big screens at the front of the Control Room, with their diagrams of the earth and the moon, that they sometimes had the sensation that they were flying the spacecraft themselves. Like pilots, they were a close-knit group, and they lit their cigarettes with matches that had “The Trench” printed on the covers, like those of a private club. They regarded the systems engineers behind them (the TELMUs, the EECOMs, the CONTROLs, and the GNCs) much as pilots regard mechanics, and they referred to the computer engineers downstairs as “electricians.”
The men in the Trench never feel more like pilots than during a rocket burn. As soon as the GUIDO got the trajectory information from the FIDO, he punched the numbers into a white keyboard in front of him, preparatory to loading (or, as GUIDOs say, “uplinking”) the data into the computer aboard the spacecraft. After the information was received aboard the spacecraft, a confirmation copy of it—a sort of return receipt—popped up on the television screen on the GUIDO’s console, and he checked it, then pressed a button ordering the spacecraft computer to accept the data. Meanwhile, the RETRO was writing out the instructions for the burn. On a maneuver pad—a green sheet of paper lined into boxes—he jotted numbers indicating the exact instant the rocket should be turned on, the length of time the rocket should fire, and the attitude of the spacecraft while it was firing. The CAPCOM read these numbers up to Lovell, who jotted them down on an identical maneuver pad, read them back for confirmation, and finally punched them into his computer.
The mechanics in the second row were as busy as the pilots in the Trench. The Control Officer, whose responsibility for the lunar module corresponded to that of the GNC for the command module, had to modify a checklist for the powering up of the LM’s main rocket—the Descent Propulsion System, which Control Officers call DPS (pronounced “dips”). It was at the opposite end of the combined Apollo spacecraft from the big rocket in the service module, and although it wasn’t as powerful as that rocket, it could build up the necessary thrust by being burned for a longer time. There was some question in everyone’s mind, though, whether the DPS would work at all, for nobody yet knew the full extent of the disaster—perhaps the DPS was out of commission, too. The rocket swung on gimbals to facilitate landing on the moon and also to allow for shifts in the center of gravity during firing; at the moment, the gimbals were set for the lunar landing. The coming burn would be what Control Officers called a “docked DPS,” to denote that the LM was docked with the command and service modules and the DPS would be pushing all of them—a tricky setup, because there was some flexibility in the connection between the LM and the command module, and the LM would not necessarily be exactly lined up with what it was pushing. Just before the burn, the CAPCOM radioed up to tell the astronauts that the nozzle of the DPS rocket was not aimed properly, and the astronauts hastily “trimmed the gimbals”—a little the way a seafarer trims his sails. If the error hadn’t been rectified, the spacecraft could have tumbled during the burn and gone off course. Then, as the astronauts were making a last-minute check of their control panels, one of them mentioned that a switch that could have jettisoned the bottom half of the LM—the part ordinarily left behind on the moon, which contained the DPS rocket—was on. The CAPCOM told the astronauts to turn off the switch.
At two-forty-three in the morning, five and a half hours after the accident, Lovell’s left hand pushed a button. For thirty seconds, Lovell felt himself pressed gently toward the floor—the only physical indication he had that the rocket was firing. A planned minor correction later would aim the craft into a narrow corridor through the earth’s atmosphere which would bring the astronauts, in less than four days’ time, to the Indian Ocean. The Recovery Officers had never stationed a ship in the Indian Ocean, and they had to act quickly now. The nearest United States Navy ship was the destroyer Bordelon, which was cruising off Mauritius. They discovered that the Bordelon was one of several Navy ships that had been modified to take a special crane for picking command modules out of the sea. However, the Recovery Officers would have to order the crane flown from Norfolk, Virginia, to Mauritius. They were banking on the fact that the Bordelon would get to port, pick up the crane, and be at the splashdown site, seven hundred miles away, before the astronauts could get there.
The rest of the night was largely a holding action. In particular, the TELMUs were trying to hold on to the LM’s consumables—a task that recurrently brought them into collision with the other flight controllers. As soon as the rocket burn was over, the TELMUs requested that the astronauts begin powering down equipment—especially the guidance computer, since its gyroscopes, which kept the platform steady, were heavy users of electricity and water. The guidance platform wouldn’t be needed until after the astronauts had rounded the moon, some fifteen hours later. Immediately, the GUIDO protested that he didn’t want to lose the platform alignment, which had been transferred so carefully from the command module. The TELMUs replied that before the next burn the astronauts could set up a new platform alignment with the spacecraft’s sextant by taking sightings on stars. The GUIDO wasn’t sure that this was possible; Deiterich, the RETRO, insisted that the platform be kept up all the way through the next burn, too; and, upstairs, Lunney, who often backed the pilots against the more conservative mechanics, agreed, although he permitted the F.D.A.I. balls—the dashboard display for the platform, which also used electricity—to be turned off.
This decision put Peters and Heselmeyer, the two TELMUs downstairs with the White Team, who had been working up what they called a “power profile” for rationing the LM’s electricity, in a tough spot. It was true that if all went well the trip home could take considerably less than four days; even so, the TELMUs had to think in terms of what they called “worst-case planning”—a conservative approach incumbent upon anyone rationing consumables. Even more than electricity, the supply of water for cooling the LM’s electronic gear was a source of worry to the TELMUs. There was a direct relationship between the two; the more electricity the instruments drew, the more water they needed, so cutting down on power consumption was a way of saving water. The cooling system worked like a car radiator, except that the water was not recycled; all the while the LM was powered up, water slowly steamed off into space, boiling away so gently that, as far as anyone could tell, it had never disturbed a trajectory.
Of all the TELMUs’ problems, however, the worst was not conserving a consumable but the reverse: how to get rid of the carbon dioxide that the astronauts were exhaling. Normally, the air in the cabin of either the LM or the command module was constantly passed through pellets of lithium hydroxide—(small white pebbles that have an affinity for carbon dioxide and therefore remove it)—in a process astronauts and flight controllers call “scrubbing the atmosphere.” The pellets were inside canisters that fitted into a sort of ventilating system that sucked dirty air from the cabin and then blew the scrubbed air back. When a canister had absorbed all the carbon dioxide it could hold, it had to be replaced with a fresh one. The trouble was that there weren’t enough canisters in the LM to last until the astronauts got home, the command module’s ventilating system was turned off, and the logical solution, which was to use the command module’s canisters in the lunar module’s air purifying system, wouldn’t work, because they didn’t fit. The problem had never been considered in plans for “the lifeboat mode.” Now the TELMU’s turned it over to another group, the Crew Systems Engineers, who were responsible for all such equipment, and who would have two days to solve the problem before the astronauts were asphyxiated.
Up in the spacecraft, the astronauts were worrying about their consumables. Haise feared that the cautiously optimistic reports from the TELMUs were a coverup for bad news. He kept double-checking the consumables to make sure that what he was being told was true. Like the TELMUs, the astronauts were most worried about their water supply, and, without telling the ground, Lovell decided that they would stringently ration what they drank. He set Swigert to work transferring some of the drinking water from a tank in the command module to the lunar module. The command module’s initially almost unlimited supply of water had stopped, of course, as soon as hydrogen and oxygen were no being combined in the fuel cells. Swigert had a hard time transferring the water, because the hose fittings in the two modules didn’t match—another curious design defect in two craft built for mutual assistance. Swigert had to use plastic juice bags to make the transfer from the command module to the LM, and in doing so he sloshed water into his shoes. Later, the SPAN engineers would get the technicians at Hamilton Standard, in Connecticut, to look into the feasibility of using the astronauts’ backpacks—which have compartments for water—as pails. It would take two days for Swigert’s shoes to dry, because with so much equipment turned off the spacecraft was getting cold. He felt as if he were in a leaky boat. In fact, Swigert, who knew least about the lunar module, was the most worried of the three. He stood by a window in his wet shoes watching the earth recede behind them and had some very deep thoughts about never coming back.
Lovell’s and Haise’s many tasks didn’t give them much time for worrying. If they were to avoid the risk of having one part of the spacecraft become overheated by the sun, they had to regain control of its attitude and then set up the thermal roll. There were still occasional spurts of oxygen from the service module, but the venting was less disruptive now. Lovell took hold of the hand control for the attitude control thruster jets, which in the LM was on the dashboard by his left hand. He ran into trouble right away, because the designers had never intended the lunar module to control the attitude of the entire Apollo spacecraft. The LM was at one end of the combined craft—a bad spot for handling the two other modules—and its thrusters were too weak to handle easily a mass more than twice its own.
As word of the disaster spread, many astronauts had come tumbling into the Control Center to see what they could do to help. One job they could perform was to man the simulators and test maneuvers that hadn’t been tried before. The lunar-module simulator was being run by Charles Duke, the backup LM pilot. The simulator, a replica of the LM’s co*ckpit, was hooked up to the smallest of the five computers in the R.T.C.C., and technicians there had already programmed it with data about the present situation, such as the strength and position of the LM’s thrusters in relation to the rest of the spacecraft, and even the random effects of the venting. Duke experimented to see if the LM could wrestle the entire spacecraft more easily by firing its thrusters steadily or in short burst. Short bursts worked better, and this information was passed on to Lovell.
There was no guarantee that the simulator reproduced the motions of the Spacecraft accurately, and, indeed, Lovell was finding he couldn’t regain control nearly as easily as Duke had done. Because the F.D.A.I. balls had been turned off, Lovell was without a compass, and the only way he could maneuver was by referring to three separate gauges on the dashboard which gave him the angles of roll, pitch, and yaw; it was about as chancy as lining up the three Bell-Fruit bells in a slot machine. Moreover, he was becoming so fatigued that he couldn’t remember whether he should fight the spin by going left or by going right, and once he found himself turning entirely around. To add to his problems, he had been having trouble with communications ever since he had begun using the radio in the LM; it made a continual beeping sound, so that he and the flight controllers could barely hear each other. The trouble was caused by a radio transmitter aboard the third stage of the Saturn rocket that had launched the spacecraft and was now trailing a thousand miles behind it on the way to impact on the moon. ‘The transmitter aboard the rocket booster was beeping so that it could be tracked from the ground, and it was using exactly the same frequency as the LM’s own radio. This arrangement saved money on ground equipment, and NASA justified it by pointing out that the astronauts weren’t supposed to be flying the LM until after the booster had crashed into the moon. On one occasion, Haise told the CAPCOM that he could barely hear him, and the CAPCOM radioed up some emergency instructions for getting home in case communications were lost altogether. Fortunately, the INCO remembered a trick that cut down on the interference. He got the astronauts to turn off their radio for twenty minutes, and during that interval he broadcast a steady signal to the booster on a slightly different frequency, causing its transmitter to shift frequencies. This incident was not the only one in which flight controllers had to play tricks on the overconfidently designed equipment.
Just before dawn in Houston, the spacecraft’s attitude suddenly took a turn for the better. By using the LM’s jets in a translation mode—one that normally moved the craft up, down, and sideways rather than turning it—Lovell finally managed to get it stabilized and pointed in the right direction—sideways to its trajectory and perpendicular to a plane drawn through the earth, moon, and sun. The next step was to set the spacecraft rolling, for thermal protection, and to keep it rolling—something that the LM’s guidance system was not equipped to do, as a LM did not need to roll on its short hop to the moon. Duke had been working on this problem in the simulator, and now the CAPCOM radioed up that Lovell would have to rotate the spacecraft some ninety degrees every hour by hand. The CAPCOM promised to remind him to do this.
Around four in the morning, Lovell sent Haise back to his couch in the command module to get some sleep. The command module, which the astronauts had taken to calling “upstairs,” would be the bedroom for the rest of the trip. Haise had last looked at his wristwatch before the accident, seven hours earlier, and he had lost all track of time. For him, the intervening period, in which he and the others were abruptly confronted with an almost insoluble problem in a strange place—had had a dreamlike quality.
At about eight o’clock in the morning, after Kranz and the White Team had also gone off to get some sleep, some forty men gathered in the glass-enclosed gallery for visitors, at the back of the third-floor Control Room. They included Robert R. Gilruth, the Director of the Manned Spacecraft Center; his deputy, Christopher C. Kraft, Jr.; and James A. McDivitt, the Apollo Spacecraft Program Manager, Occasionally, the flight controllers of the Gold Team, which had taken over from the Black Team an hour earlier, glanced over their shoulders to see what was going on. A FIDO who happened by said later that he had never before seen so much NASA brass in one place at one time. The NASA brass was trying to decide which of three possible types of burn to do after the astronauts had rounded the moon. The burn was scheduled for eight-thirty that evening, which would be two hours after pericynthion—the spacecraft’s closest approach to the back side of the moon—and hence it was called the PC+2 burn. Pericynthion was the point at which the service-module rocket was normally fired to put a spacecraft into lunar orbit, and, in the event that that rocket failed, the point two hours past pericynthion had always been considered the place to do an emergency burn back to earth, because it ordinarily took two hours to power up the LM rocket.
Christopher Kraft, who before he became Deputy Director of the Manned Spacecraft Center had once had Kranz’s job as Chief of the Flight Control Division, outlined the alternative burns that could be made at PC+2. The first was to jettison the service module and blast the LM’s rocket with everything it had, so that the astronauts would arrive in the Atlantic Ocean a day and a half afterward. Nobody liked this idea any better than Kranz’s group had liked a similar proposal the night before. It left virtually no room for error—and out around the moon an error in velocity of a tenth of a foot a second could cause a spacecraft to miss the earth altogether. The reason the RETROs had always achieved astonishing accuracy in splashdowns from the moon was that they could, as they put it, “tweak up” a trajectory anywhere along the line with midcourse corrections, and the fast burn to the Atlantic would leave little fuel for tweaking. Besides, in the Atlantic there were no recovery ships.
Kraft hurried on to the two other alternatives, either of which would avert the emergency landing in the Indian Ocean, where the spacecraft was now headed, and bring the astronauts to the prime landing area in the southwest Pacific—the only spot on earth where there were adequate recovery vessels. One of these alternatives involved a relatively fast burn, which would get the astronauts to the Pacific about a day and a half afterward, and the other involved a slower burn, which would get them there exactly twenty-four hours later than that. The twenty-four-hour difference had to do with the earth’s rotation—the spacecraft always descended to its splashdown from perigee, the closest approach on the side of the earth that was away from the moon, and consequently the splashdown point depended on the time the spacecraft reached perigee. (The RETROs like to say, “Don’t worry—the Pacific will be there!”)
While Kraft spoke, those listening to him could see through the glass behind him the big center screen at the front of the Control Room, where the yellow line representing the trajectory of the Apollo spacecraft was moving closer and closer to the moon. From time to time, they glanced at Dr. Gilruth, the Director of the Manned Spacecraft Center, who had previously been director of the Mercury project, the first American manned-spaceflight program. He was the senior man present, and when NASA people met to make a decision there was no voting; rather, after discussion the top man made the decision.
Kraft threw the meeting open for discussion. The faster of the two burns to the Pacific had an immediate appeal, for everyone shared the fear that something else might go wrong with the spacecraft, in which case the sooner the astronauts got home the better; indeed, this seemed such an obvious choice that some astronauts were already practicing it in the simulators. The fast burn to the Pacific had one serious drawback, however: just as in the case of the even faster burn to the Atlantic, the astronauts would first have to jettison the service module, because the LM was strong enough only to push itself and the command module to the required velocity. Flight engineers have a natural reluctance to do anything as irrevocable as throwing away half a spacecraft. Most important, the service module, fitting snugly over the heat shield—the ceramic bottom of the command module, designed to protect the astronauts from the heat of reëntry through the earth’s atmosphere—insulated the shield, and no one knew what effect a prolonged exposure to the cold of space would have on it. The service module was normally jettisoned only half an hour before splashdown, and no one had thought it necessary to test the heat shield’s resistance to cold for the length of time it would take a spacecraft to come back from the moon.
Kraft wanted to get the advice of the Lead RETRO and the Lead FIDO, both of whom were then on duty with the Gold Team. Deiterich, who had been up all night, arrived at the glassed-in gallery followed by David Reed, the Lead FIDO—a tall man of twenty-eight with light-brown hair, a graduate of the University of Wyoming, who joined NASA in 1964. Reed was more rested, for he had been at home in bed at the time of the accident, and when he turned on his television set and observed Deiterich and several other dynamics officers already in the Trench he had sensibly taken three aspirins and gone back to bed, on the theory that he would be of more use in the morning if he got some sleep. He had had a restless night anyway, and had come in to work at four o’clock in the morning.
Reed and Deiterich, who would be the ones to work out whatever trajectory the meeting settled on, were both opposed to any burn that required jettisoning the service module. Reed pointed out that if they retained the service module and did the slower burn, they would still have the option later, if anything else went wrong, of jettisoning the service module and making a faster burn. NASA engineers tend to favor any alternative that “keeps the options open.” Kraft, who was also in favor of retaining the service module and doing the slower burn, summed up the case for this alternative strongly, and Dr. Gilruth, who had said little during the meeting, nodded assent. The men who had to plan how to bring the crippled spacecraft back through the atmosphere were grateful for the extra twenty-four hours that the slower burn gave them.
Deiterich and Reed went back to their consoles, which were side by side in the Trench. Reed’s had a single orange light that flickered constantly, showing that telemetry was being loaded into the computers downstairs, but Deiterich’s console had no lights whatever. It had two television screens and six clocks. Under the glareproof glass covering the console’s desk there was a map of the earth, centered on the Pacific—the target Deiterich was aiming for. As he began planning the PC+2 burn, he also began to consider some of the problems that would come up at reëntry. The astronauts, back in the command module by then, would have to jettison both the service module and the lunar module before the spacecraft hit the atmosphere, but, with a dead service module, the LM would have to do all the work, including jettisoning itself. Nothing of the sort had ever been tried before. Deiterich had a couple of ideas, which he jotted down.
Many of the flight controllers on duty now would be on duty again three days later during reëntry. Behind Deiterich, at the CAPCOM’s console, Joseph Kerwin, who had succeeded Lousma at seven-thirty that morning, was talking with the astronauts in the spacecraft. Kerwin, a trim, clean-cut man, was a commander in the Navy Medical Corps; born in Oak Park, Illinois, in 1932, he graduated from Northwestern University Medical School in 1957 and became an astronaut in 1965. Kerwin was having a hard time hearing the Apollo’s crew, because the spacecraft’s amplifier bad been turned off to save power. He had the volume on his headset turned up so high that hours after he went off duty he was still deafened. In spite of the crackling in his headset, he managed to catch one unexpected statement. Loud and clear, and apropos of nothing in particular, Lovell said, “Joe, I’m afraid this is going to be the last moon mission for a long time.” That was not the kind of talk that Lovell’s superiors expected to hear from one of their astronauts under any circ*mstances. (This was the only indiscretion, if that is the word for an honest doubt, an astronaut committed during the whole flight.) Lovell’s fears did not come true, though Apollo 13 led to important modifications of equipment used in the four remaining Apollo flights. Before the next mission, some design changes were to be made in the spacecraft to prevent another such accident from happening. All wires inside the cryogenic tanks were to be insulated with stainless steel; a third oxygen tank was to be added to the service module, at some remove from the other two tanks; and a battery capable of powering the command module home from any point in its orbit was to be added. Some alterations were also to be made in the Control Room: the EECOM’s console would be provided with a better warning system, and the philosophy behind the training simulations would change so that, as Reed would say later, “They can throw anything at us they want, and we won’t object.”
When Lovell woke up Haise at about ten o’clock in the morning, he asked him how he had slept. Haise hadn’t slept well at all. Shortly afterward, Lovell and Swigert disappeared upstairs into the command-module bedroom. They didn’t sleep very well, either. The brilliant sun kept streaming in through the windows as the spacecraft rolled about, making disconcerting stabs of light. Lovell suggested pulling the shades on the windows. But without benefit of sunlight the cabin got very cold, and without electrical power it didn’t warm up again. (Although the windows were large enough to admit the light, they didn’t admit much heat.)
The main business Tuesday afternoon was preparing for the PC+2 burn, which was to take place at eight-thirty that evening. First, the astronauts would have to make sure that the alignment of the guidance platform was still accurate, for the gyroscopes that kept the small metal platform stationary could gradually drift out of line, imparting errors. Ordinarily, an astronaut seeking to check the alignment punched into his computer a request that it find a particular guide star. The computer, using the platform as its reference, swung the spacecraft to the right attitude to bring the star into view, and then the astronaut squinted through a telescope—the Alignment Optical Telescope, or A.O.T.—to see if the star was neatly centered in the telescope’s field of vision. If the A.O.T.’s aim was off, he computed the angle of error, which was also the degree of error in the alignment, and punched the correction into the computer. Doing this now was out of the question, because clouds of debris particles from the exploded tank surrounding the spacecraft shone so brightly in the sunlight that they completely obscured the stars. That morning, the Lead GUIDO, Kenneth Russell—a tall, curly-haired man, who sat alongside Deiterich and Reed—had suggested that instead of using the guide stars the astronauts check the platform against the sun, which would be a good deal easier to see in the blizzard of particles. Deiterich had complained that a sun check would not be exact enough; whereas a star is a precise pinpoint of light, the sun’s disc is so big that a check based upon it would be accurate only to within two degrees. However, Russell had nothing better to offer, and Deiterich couldn’t think of anything better himself, so he agreed to accept the two-degree error.
What had made him hesitate at the time was uncertainty whether the error could be corrected later, because the TELMUs had told him that the guidance platform would have to be turned off immediately after the PC+2 burn and kept off all the way back to earth, and Kranz had indicated that there would be no reprieve this time. However, Reed, the Lead FIDO, had found a way out: he had remembered from Apollo 8 a trick for tweaking up the trajectory on the way back to earth without the platform. An alignment involving the earth’s terminator, it was almost as simple as a sailor’s using the North Star to steer by, but without it Deiterich would never have been willing to accept the two-degree error now. So the sun check was duly performed, in the hope that a more accurate star check could be made later.
Though the astronauts had not had much time to think about the moon, they were so close to it now that it overflowed the spacecraft windows, filling the co*ckpit with cold white light. The light, however, lessened and lessened, for they were moving around to the moon’s dark side, and at last the moon and the sun as well suddenly vanished. The spacecraft was going around the moon like a boat rounding a buoy. The nearer to the moon the spacecraft came, the faster it moved; it was travelling at six thousand miles an hour now—three times its speed at the time of the accident. The earth sank nearer and nearer the moon’s horizon, and then it, too, disappeared. The astronauts would be out of touch with Houston for about twenty-five minutes—until they emerged on the other side. The orange light on the upper left of the FIDO’s console stopped its constant flickering, and he knew that the telemetry from the spacecraft was no longer reaching the computers downstairs. The fight controllers stood up, stretched, and began talking to each other face to face, without benefit of the loop. Normally, the first passage of a spacecraft behind the moon was a suspenseful time for those waiting on earth, but the Apollo 13 mission had been so suspenseful already that most of the flight controllers regarded the period of radio silence as a breather.
The astronauts regarded it as a breather, too, for the pass behind the moon gave them their only chance to take a close look at it; at pericynthion, they were only a hundred and thirty miles from its surface. Before that, the sun had popped up into the sky again, so that they could see the ground. In the early dawn, the mountains below cast shadows longer than their own height—the moon itself looked dappled and dark—but as the spacecraft hurtled on, coming ever closer, the shadows shortened and the ground became increasingly bright. The inside of the spacecraft became brighter, too, and the astronauts put away the flashlights they had been using. Lovell had circled the moon ten times on the Apollo 8 mission, but Swigert and Haise were seeing it for the first time. Coming so far to see what others had seen before, and better, was anticlimactic, but although they were not the first to see the moon so close, they had the disquieting feeling that they could well be the last, and this gave their observations a compensating urgency. The back of the moon was a jumble of whitish highlands, with here and there a small black mare nestled among the hills like an alpine lake. Haise clicked away with his camera at one of the black spots, the Crater Tsiolkovsky, until it was lost again in the folds of the mountains. The photographs proved to be the most detailed ever taken of the area, one of the most interesting on the moon’s back side. At pericynthion, Lovell pulled the two other men away from the window, reminding them that they had a burn to do in two hours.
On the ground, Kranz, too, was getting nervous about the PC+2 burn, in part because the FIDO had reported some unexplained changes in the spacecraft’s velocity. The changes were all the more perplexing because the venting from the oxygen tanks had almost certainly stopped by now, and this was the only cause of such aberrations Kranz or the FIDO could think of. Of course, any unpredictable last-minute changes in the spacecraft’s speed—and hence in its trajectory—would further complicate the planning for an accurate burn. Above all else, Kranz was anxious that nothing go wrong with the PC+2 burn and knock the spacecraft off the return trajectory that everybody had worked so hard the night before to achieve. On the radio, the CAPCOM reminded Lovell that he should cut short the burn at the first sign of trouble; the burn could be done again any time in the next several hours. There was a new CAPCOM now; Kerwin had passed on the crackling headset to Vance Brand, a thirty-eight-year-old graduate of the University of Colorado, who had been a test pilot with the Lockheed Aircraft Corporation before becoming an astronaut, in 1966. Brand, a stocky man with light hair, helped out in the command-module simulator between shifts as CAPCOM. The idea now was to speed up the spacecraft so that it would arrive at its perigee about nine hours sooner; not only would this bring the astronauts back earlier but it would move the landing site from the Indian Ocean to the southwest Pacific, a distance of some ten thousand miles. If the burn had to be cut short, the astronauts could come down anywhere between the two points, and, accordingly, the RETRO on duty, Bobby Spencer, drew a line between them on a map and passed the map on to the Recovery Officers, who would have to be prepared to rescue the astronauts anywhere along that line.
The Recovery Officers, who now had to compile a list of all shipping within striking distance of the line, were already nervous, because their meteorologists had announced that a hurricane—Tropical Storm Helen—was heading for approximately the same spot in the Pacific as the astronauts. The Recovery Officers suggested that the astronauts land somewhere else on that longitude—a little east or west. Deiterich, who had been up now for almost twenty-four hours, and who had the plans for the burn all set, strode into the Recovery Room and, as he put it later, “really hounded those guys until I got them to admit that they didn’t have enough of a handle on the weather to say what would happen in two days’ time.” RETROs sometimes were as short with Recovery Officers as they were with mechanics and electricians.
The spacecraft had rounded the moon and was heading back toward the earth. It was still travelling at over five thousand miles an hour, but the higher it rose from the moon the slower it would go, until the next morning, at the crossover point into the earth’s gravity, it would be travelling at less than three thousand miles an hour. At the moment, it was moving so quickly that Haise felt as if he were in a jet plane taking off from a short runway; when he stole a glance out the window, the spacecraft seemed to be rising straight up from the moon. Immediately below, he could see Censorinus, a crater so sharp that it seemed the spacecraft might have just been ejected from it. To the west of Censorinus he could make out Tranquillity Base, where the Apollo 11 astronauts had landed nine months before. He couldn’t see the Fra Mauro hills, where he and Lovell had been supposed to land the next day, nor was he ever able to see the crater that Lovell and the other Apollo 8 astronauts had named for him. Brand’s voice came in over the crackling radio to report that the booster had hit the moon and made a crater that (on the basis of seismic data) was probably a hundred and twenty feet in diameter, but Haise couldn’t see that, either. However, he told Brand he was glad to hear that something had worked right on this flight.
Brand was talking to the astronauts less now, for he knew that they were busy. Ten minutes before the burn, Kranz checked with each flight controller in turn to make sure each was ready. At the back of the Control Room, the visitors’ gallery was filling with people who wanted to be present; there was even more NASA brass than there had been that morning, for Dr. Thomas O. Paine, who was then the NASA Administrator, and Dr. George M. Low, the Associate Administrator, had flown down from Washington. There was a spectator up in the spacecraft as well, for Swigert was in the LM, looking over Haise’s and Lovell’s shoulders. Ordinarily, command-module pilots were not present for lunar-module rocket burns. Swigert, who had nothing to do himself, was feeling like a third wheel. Everyone was tense. Brand, who was supposed to say “Mark!” to inform the astronauts when there were exactly forty seconds to go, said “Mark!” by mistake three minutes ahead of time—an understandable mistake, because there were several electronic clocks at the front of the Control Room counting down the time to different events, and it was easy to look at the wrong one. Fortunately, one of the astronauts caught the error.
At the right moment, Brand called out “Mark!” again, and just forty seconds later Lovell, his hand on the throttle, turned on the LM’s main rocket. Because—like the free-return maneuver—this was a docked burn, Lovell had to do the throttling manually; even though the craft’s computer was what flight controllers called “up and running,” it was not programmed for throttling a docked-DPS burn. It would, however, control the guidance and turn the rocket off when the spacecraft had reached the proper acceleration; one of the guidance instruments could measure increases or decreases in speed. Lovell made the burn in three separate stages, so that it could be stopped more easily in case of trouble. First, he throttled the rocket up to ten per cent of its thrust for five seconds, to warm it up. Then he brought it up to forty percent of its thrust for twenty-one seconds to trim the gimbals, Any problems with the rocket’s firing would show up now. In Houston, the Control Officer, Richard Thorson, studied his telemetry. When the CONTROL was sure the burn was going smoothly, Lovell brought the rocket up to full thrust for almost four minutes. The computer turned off the rocket only thirteen-hundredths of a second after the time predicted to reach the right speed, which Deiterich and Spencer thought was surprisingly accurate for a manual docked firing. Now that the astronauts would not be landing in the Indian Ocean, the Bordelon was called off, and the special crane was taken off “alert” at Norfolk.
As soon as the PC+2 burn was over, Brand expected Kranz to give him the go-ahead to read off the procedures for powering down the spacecraft for the long coast back to earth. Looseleaf notebooks giving the procedures were spread out on Brand’s console, and he was anxious to get on with them, because he realized how tired the astronauts were, and wanted to get them to bed. CAPCOMs sometimes have to represent the crew’s interests on the ground. The go-ahead for the power-down never came, and when Brand turned around to find out why, he saw a number of men standing around Kranz’s console. Kranz was in the middle of what he later called “a long and loud debate” between the TELMUs, on one hand, who were anxious to proceed with the power-down immediately, and a group of design engineers, on the other, who were insisting that a good thermal roll be set up right away; the spacecraft’s attitude in relation to the sun had been so erratic for about a day, they argued, that some part of the craft was likely to overheat and break down. Having the astronauts roll the spacecraft manually every hour had not proved effective, and the design engineers were hoping to set up an automatic roll, monitored by computer. The TELMUs had powerful allies in members of the astronaut corps, for, like Brand, they all wanted to get the spacecraft powered down as soon as possible, to let the crew have some rest. Donald K. Slayton, who, as Director of Flight Crew Operations, was the unofficial chief astronaut, was telling Kranz that it would take a good two hours to set up a roll, and the astronauts in the spacecraft had had almost no sleep for the better part of two days. The TELMUs were saying that keeping the LM powered up for another two hours would knock their power profile out the window, and that that was nothing compared to what would happen to it if they had to keep the guidance system powered up to monitor the roll. Kranz listened, and then, in the NASA tradition of the top man’s making the decision, announced that they would set up the roll anyway—the astronauts, he reasoned, would be better off losing a little more sleep than risking any more breakdowns. They would not, however, keep the guidance equipment powered up all the way back to earth.
Brand put aside the power-down checklist and began reading up the procedures for the roll instead. The LM’s guidance system had never been designed to maintain a roll, and doing so was particularly difficult with the two other modules attached. Each time the astronauts got the spacecraft rolling, it developed a wobble, and the wobble worsened until there was no roll left—the spacecraft was like a top at the end of its spin. While the astronauts continued to wrestle with the roll, the FIDO was plotting vectors to get some idea of how accurately the spacecraft had been placed on its new trajectory. David Reed, the Lead FIDO, was worried because there appeared to be an unexplained error in the trajectory. The spacecraft was about one degree from where it ought to be. Something in the spacecraft had to be venting, but Reed couldn’t think what.
The astronauts were not told that night about the increasing error in their trajectory. While Lovell kept trying to work the wobble out, Haise began powering down parts of the lunar module. What the TELMUs couldn’t win directly, they won by persistence and stealth: they were continually getting Brand to read up small lists of items to turn off. For the two-and-a-half-day coast back to earth, the LM would be almost as inert as the command module. About the only things to be left running would be the radio transmitters and the life-support system.
After an hour and a half, Lovell felt he had set up as good a roll as he could get. Accordingly, when Brand was transmitting some more suggestions from Duke, in the simulator, one of the astronauts in the spacecraft interrupted, “Hey, we’ve gone a hell of a long time without any sleep,” and another voice put in, “I didn’t get hardly any sleep last night at all.” At about ten-thirty—some twenty-four hours after the accident—Brand told the astronauts that they could begin to power themselves down. This was easier said than done, for the astronauts had built up a good deal of nervous energy. They still hadn’t gone to sleep an hour later, and Brand then radioed up instructions from Slayton that they stop fiddling around and get to bed. Swigert, however, who was particularly keyed up, ran through a recapitulation of his impressions of the accident for Brand.
Rounding the moon had given the astronauts’ spirits something of a lift, but now that they were on the quarter-million-mile straightaway back to earth, Swigert was growing increasingly apprehensive. As command-module pilot, reëntry would be up to him. He told Brand he was worried about the command module’s fitness; in particular, he was concerned about Main Bus B, where the failure in the electrical system had first become apparent. During reëntry, along with Main Bus A, it would be providing power drawn from the three reëntry batteries—assuming the bus itself hadn’t been damaged by the accident. “You think Main Bus B is good, don’t you?” Swigert asked anxiously.
Brand answered, “That’s affirm. We think it is, but we want to check it out anyway. We think you guys are in great shape all the way around. Why don’t you quit worrying and go to sleep?”
“Well, I think we just might do that. Or part of us will,” a voice said from the spacecraft. ♦
(This is the first part of a two-part article.)
