Thirteen: The Apollo Flight That Failed

by Henry S. F. Cooper Jr.

  Reed took the matter up with Kranz.

  “How far off are we?” Kranz asked.

  Reed told him, and added that the error should be corrected.

  Kranz replied that any correction would be difficult now, because the lunar module had been closed up and it would take too much time to open it again. Kranz asked Reed exactly how the attitude error changed the situation, and Reed told him it would alter the point where the spacecraft hit the atmosphere.

  Kranz thought that Reed was talking about the point where the LM would hit the atmosphere, and asked him if the radioactive-fuel cask was what he was worried about.

  Reed said no—that he was concerned about where the command module would hit the atmosphere, for if the LM went off course to the north, the command module would go off course to the south. It would, in fact, go farther off course than the LM, for it was lighter and so would get a harder push when the two modules were blown apart by the air in the tunnel. Reed said that this error could affect the astronauts’ passage through the corridor and where they landed, but Kranz disagreed. He told Reed he felt that the error in the command module’s trajectory could be corrected later, so he was inclined to leave things alone now. However, he wanted to hear what Deiterich had to say.

  Deiterich was still worrying about the fuel cask, possibly because he felt the gaze of the A.E.C. man on the back of his neck. He rapidly figured out where the cask would come down under the new circumstances, and he was able to assure the A.E.C. representative that it would still come down in deep water. If there were any chance of getting into the LM easily, it would still be better to make the correction now, but, like Kranz, he was worried about the time it would take to reopen the LM and bring the spacecraft to the correct attitude. He knew the chances of doing this were slim, so he said to Kranz, “Lookit, if he’s closed out in the LM, let’s let him alone. He’ll be behind.”

  Kranz said that Lovell was closed out in the LM.

  “O.K., we’ll just buy it,” Deiterich said. He was not particularly pleased with what he was buying. He had already had enough problems with the trajectory, and it wasn’t out of the question that he would have some more.

  Lovell, who knew nothing about his attitude error, was working on another problem: checking the integrity of the command module’s hatch—a matter that had come up the day before, when Lovell rejected the idea that he and the others wear their space suits during reëntry. To make a complete check, the hatch had to be shut and air had to be vented from the tunnel, which would be closed off at both ends. If there was a leak, Aaron would detect it through an increase in the oxygen flowing from the surge tank to compensate for the outflow. The check would be complicated by Deiterich’s plan to blow the two craft apart with the air in the tunnel; he wouldn’t be able to do this if Swigert vented much air. The RETRO and the EECOM had discussed the problem, and Deiterich had agreed to let Swigert vent half the air; that would still leave enough pressure for a good jettison.

  After Swigert opened the valve to let the air out of the tunnel, it took ten minutes for the tunnel pressure to drop the right amount. Aaron waited a couple of minutes longer before checking, so that any leak would have time to show its effects. Then, however, he found that the surge tank was pumping more oxygen into the cabin than it ought to be. Was the hatch leaking, then? He made no mention of the possibility at that moment, for he didn’t want to put everyone in what he called a “worry mode” until he had checked out a couple of other explanations. Swigert noticed the extra oxygen flow himself, though.

  Within a minute, Aaron found out what the trouble was. Until recently, the lunar module had been providing the command module’s oxygen, and the LM’s oxygen was set to a slightly lower pressure than was usual in the command module. Consequently, it would take an extra surge of oxygen to bring the command module’s pressure up to normal. It was this extra surge that Aaron had mistaken for evidence of a leak. Three minutes later, the excess oxygen flow stopped, and Aaron relaxed.

  Almost as soon as the oxygen flow had steadied, Willoughby, the Lead GNC, came on the loop to tell Kranz of a new difficulty: the command module’s guidance platform was once again in danger of gimbal lock. There was almost nothing the astronauts could do about it this time, since the spacecraft’s attitude was being controlled automatically by the LM, which was inaccessible. Shortly, Loden, the CONTROL, warned Kranz that the spacecraft’s wobble was going beyond the limits of what the LM’s guidance system could handle.

  Kranz decided that the astronauts had better get rid of the LM as soon as possible. First, however, he had to make sure of a few things. He asked Aaron how the command module’s cabin pressure was doing. Aaron said it was fine. The LM was not needed to plug a leaky hatch. Next, Kranz turned to Willoughby, who had been afraid earlier that all the command module’s thrusters might not fire, and asked him whether he still wanted to test-fire them before the LM was jettisoned. Willoughby replied that the thrusters looked warmer now, so he didn’t think there would be a problem. The LM would not be needed to spin the command module into the corridor. Then Kranz turned to Loden and asked if there were any other problems with the LM that he should know about. There weren’t. “O.K., let’s punch off the LM,” Kranz said. But before he could give the order, he had to check with each flight controller in turn—an exercise he called “going around the horn,” which he was required to do before ordering any irreversible action. He ticked off the names rapidly—RETRO, FIDO, GUIDO, CONTROL, TELMU, GNC, EECOM, Surgeon, and INCO—and the answers came back just as fast: “Go,” “Go,” “Go.”

  The entire roll call took about ten seconds, and when it was finished Kranz told the CAPCOM to tell Lovell he could separate the LM as soon as he was ready. In spite of all the “Go”s, there was still a problem; Apollo 13 would be iffy until the end. When the umbilicals that had been supplying power from the LM to the command module were disconnected, a short circuit might cut the LM’s power supply, turn off its guidance system, and allow it to collide with the command module or go far off course with its radioactive cargo. But discussion among the EECOMs, the TELMUs, and the Grumman engineers had convinced the controllers that the risk would have to be taken, and the order was given for the pyros to be fired. It was agreed that when the jettison was done, the LM’s guidance system should insure that the two craft would not come together again, and that the fuel cask would land in deep water.

  At length, Lovell reported that the LM was gone. The LM Systems Officers felt a momentary pang; it would have been nice, they thought, if the LM could be brought back to earth. It had proved a better lifeboat than anyone had had a right to expect. Much later, a TELMU drew a cartoon—which he presented to the CM systems engineers—showing a jaunty lunar module prancing through the sky, dragging on a stretcher a sick-looking command module swathed in bandages, its tongue hanging out, a transfusion bottle dangling from its antenna. (Grumman also submitted to North American Rockwell towing charges for the approximately three hundred thousand mile trip.) Now, as the actual LM spun off into the distance, its golden legs kicking in space and the sunlight glinting on its silvery hatch, Haise, its pilot, snapped photographs until it became an iridescent speck in the distance. The separation had rocked the command module slightly, and Kerwin radioed up that the astronauts had better watch out for gimbal lock. Kranz’s attention returned to the command module’s hatch, now that there was no longer a lunar module to protect it. “How’s your pressure doing, EECOM?” he asked. Aaron said it still looked all right.

  The command module was flying alone now, the way it would have been if no accident had occurred. The astronauts were back on the original timeline for the mission, though they were four days ahead of their original schedule, and though heavy equipment from the LM was stowed where moon rocks should have been. Entry interface was an hour away. The astronauts, travelling at about fifteen thousand miles an hour, were only about eleven thousand miles from their target on earth, and considerably less than that from the earth itse
lf, which was big enough now so that it looked like a sea of blue outside a ship’s porthole. Clouds scudded across it like waves. In the next half hour, the spacecraft’s trajectory would curve around it like a cable winding onto a winch, and at a point immediately opposite the moon the spacecraft would drop like an anchor through the air and into the ocean, splashing down near the aircraft carrier Iwo Jima. That is, the spacecraft would do this if all went well.

  Deiterich was sitting at his console preparing the final reëntry PAD. The rest of the flight controllers had all had their moments of worry since the preparations for reëntry began: Russell, the GUIDO, over the command module’s alignment; Reed, the FIDO, over the attitude for separating the LM; Willoughby, the GNC, over the heating of the thrusters; and especially Aaron, the EECOM, over both the hatch’s integrity and the extra two-amp drain. So far, Deiterich had seemed almost as cool and impassive as Kranz.

  In order for the spacecraft to get through the narrow corridor that was its only safe passage to earth, it had to hit the atmosphere at an angle no steeper than 7.3° to the horizon and no shallower than 5.5°. Deiterich had assumed, for the reëntry PAD he was working up, that the spacecraft would hit the atmosphere at an angle of 6.51°, which had been the forecast the last time he checked the spacecraft’s trajectory. That was steep enough so that Deiterich had stipulated in the reëntry PAD that the spacecraft should reënter the atmosphere at an attitude called “lift vector up;” that is, the command module’s flat heat shield would tilt slightly upward, to make the spacecraft plane a little. Now Reed handed him the latest vector information, and Deiterich saw that the angle predicted for reëntry had shallowed out to 6.2°. It was the same unpredictable shallowing they had been seeing all along, and the new figure threw all Deiterich’s calculations off. “I don’t believe you, FIDO!” he said to Reed. Reed said later that Deiterich had almost scared him to death—just as Reed had frightened him.

  Deiterich was in a very tight spot. In shallowing, the trajectory was approaching the angle 6.08°, at which the spacecraft, instead of coming in lift vector up, would have to come in lift vector down, to make the spacecraft dig into the atmosphere and so counteract the shallowing. Coming in with the wrong lift vector would affect the landing site—if, indeed, it didn’t knock the spacecraft out of the corridor altogether—but Deiterich had no way of knowing whether the shallowing would continue at a rate fast enough to require a change in the lift vector from up to down. It had only a little over a tenth of a degree to go, and so far that morning it had already shallowed three-tenths of a degree. But there was no guarantee that the trajectory would continue to shallow at the same rate. “That’s the kind of thing that really splits a RETRO,” Deiterich said later.

  Kranz kept asking Deiterich how he was coming with the reëntry PAD, since it was high time the contents of the PAD were transmitted to the spacecraft. Kranz, being one step removed, was exhibiting an almost unnerving cool, but it was his job to mesh all the last-minute details for reëntry, and the reëntry PAD was the only missing one. Deiterich, for his part, wanted to hold off on the PAD until the last possible minute; among other reasons, the PAD contained the exact times for automatically deploying the parachutes, and these times would be different depending upon which lift vector was used. Having the parachutes open at the wrong altitude could be as disastrous as any of the dangers that had been avoided thus far.

  Up in the spacecraft, Swigert, too, was asking for the PAD, but Kerwin managed to put him off, saying that it would be a few minutes before they got it right up to speed. Deiterich, who felt he was beginning to run out of time, passed to Russell, the GUIDO, some of the reëntry information that would have to be up-linked to the spacecraft computer; however, he asked Russell to hold off sending it, because some of the data might have to be changed. Russell punched the information into his keyboard, so that the up-link was set up on his electronic screen, all ready.

  Then Deiterich checked with Reed to see how the trajectory was doing. It did not seem to be shallowing as fast as it had been before, so Deiterich decided to gamble on a reëntry with the lift vector up, and he advised Kranz and Russell to transmit the reëntry PAD and the up-link the way they were.

  Deiterich made the right choice. It was later learned that the cause of the shallowing had been the constant boiling off of water into space from the LM’s cooling system, and now that the LM was gone the shallowing had slowed down. The more the LM had been powered up, the greater had been the venting, and that was why the shallowing of the trajectory was unusually strong that morning. No one knew this at the time, even though everyone had been constantly aware of the continuous drain on the LM’s water and the blizzard of ice crystals that the water made outside the window. The venting was on such a small scale that it had never caused trouble during the short hops of previous LMs down to the moon and back, so no one had realized that the negligible thrust it imparted to the spacecraft would build up appreciably during the LM’s long flight back to earth. (Earlier, there may have been some venting from the service module’s hydrogen tanks as well.)

  Deiterich, who did not know that his troubles had flown off with the LM, determined privately to go ahead with the reëntry PAD and the up-links, and that he would not make the final decision about whether to change the lift vector until just before the time of the moonset check, which the astronauts would carry out two minutes before reëntry. In the meantime, he began figuring out the changes that would have to be made in the timing for the parachutes if the shallowing increased at the last minute.

  The spacecraft was swinging behind the earth now, like a ship turning to enter port. The earth had long since ceased to be a ball in space, or even a sea of blue, and was now “land,” in the sense that sailors returning to shore after a long voyage would use the word. Now that the final preparations had been made, the flight controllers had less to do and more time to think about what lay just ahead, so their conversation became increasingly terse. Kranz decided to take an informal trip around the horn. The EECOM, the GNC, the FIDO, and the GUIDO all said that things were “looking good.” When Kranz called on the RETRO, there was no answer; Deiterich was totally absorbed in the trajectory.

  Up in the spacecraft, the planet on which the astronauts were about to land had virtually vanished, because they were well around on its dark side now, away from the sun. Though the landing would take place close to noon Houston time, it was early morning in the mid-Pacific. In the dark, it was almost impossible to discern the earth’s horizon, and this meant that the astronauts couldn’t make the usual last-minute check of their trajectory by clocking the instant a given point on the horizon cut across the reticle etched in the spacecraft window. Instead, they would have to make a moonset check—the one Deiterich had thought up a couple of days earlier—and it was this that he was relying on for his final decision about the lift vector. The moonset check was a variation on the horizon check, and Deiterich liked it even better, because it “synched in” the movements of the earth and moon with the positions of the stars, and so fixed the trajectory even more precisely. Earlier, Swigert had brought the spacecraft to the best attitude for watching the moon, and now he had the moon lined up on the reticle in the window. As the spacecraft swung farther and farther around the earth, the moon gradually sank lower in the sky, until at last it set, revealing for an instant where the earth’s horizon was. Just at the predicted time, the horizon bit a black arc out of the hard-white moon. It was not the fuzzy, diffuse sort of moonset that is seen through the earth’s atmosphere. Swigert said later that the moon sort of blinked out. For the first time in six days, the astronauts were out of sight of the moon.

  They now had less than a quarter of the earth to round. They were traveling at twenty-one thousand miles an hour, and they would be going twenty-four thousand miles an hour in ten minutes’ time, when they reached entry interface, four hundred thousand feet above the ground. There the friction from the atmosphere would begin to heat up the spacecraft’s heat shield.
Nineteen seconds later, the resulting flames would make radio contact impossible. The heat would reach five thousand degrees, and for at least three minutes—until the spacecraft’s speed had slowed and the temperature had dropped enough for communications to be reestablished—no one would know how the astronauts were faring. As the time for interface approached, Deiterich and the other flight controllers, in view of what they had recently learned about the violence of the tank failure in the service module, were getting increasingly apprehensive about the condition of the heat shield. Up in the spacecraft, Haise worried, too—he regretted that he couldn’t go out and take a look at it. Things had held together thus far; he hoped they would hold together a little longer. The flight controllers and the astronauts talked about inconsequential matters, among them the splashdown party that the flight controllers always have after a flight. Swigert told Kerwin he wished he could be there for it, and Kerwin said it would be a wild one. They talked a bit about the lunar module, too, for the TELMU had just reported that the LM’s telemetry, which he had been monitoring, had suddenly stopped. Presumably, the LM had burned up in the atmosphere—the fate of any craft without a heat shield.

  “Where did she go?” one of the three astronauts asked.

  “Oh, I don’t know. She’s up there somewhere,” said Kerwin. The astronauts and the flight controllers were all a little sentimental about the LM.