Apollo: The Race to the Moon (63 page)

In October 1968, when the O2 Tank 2 used in Apollo 13 was at North American, it was dropped. It was only a two-inch drop, and no one could detect any damage, but it seems likely that the jolt loosened the fill tube that put liquid oxygen into the tank.

In March 1970, three weeks before the flight, Apollo 13 underwent its Countdown Demonstration Test that, like all C.D.D.T.s, involved loading all the cryos. When the test was over, O2 Tank 2 was still 92 percent full, and it wouldn’t detank normally—probably because of the loose fill tube. Because a problem in the fill tube would have no effect on the tank’s operation during flight, the malfunction was not thought to be relevant to flight safety.

After three unsuccessful attempts to empty the tank, it was decided to boil off the oxygen by using the internal heater and fan. This was considered to be the best procedure because it reproduced the way the system would work during flight: heating the liquid oxygen, raising its pressure, converting it to gas, and expelling it through the valves and pipes into the fuel cells where, in flight, it would react with the hydrogen. So they turned on the tank’s heater.

A technician working the night shift on Pad 39A was assigned to keep an eye on the tank temperature gauge and make sure that it did not go over 85 degrees Fahrenheit. It was not really necessary that a human serve this function, because a safety switch inside the tank would cut off the heaters if the temperature went beyond the safety limit. And, in reality, the safety margin built into the system meant that the temperatures could go considerably higher than 85 degrees without doing any damage. But the precautions were part of NASA’s way of ensuring that nothing would go wrong.

After some time, the technician noticed that the temperature had risen to 85 degrees, but all he had been told was that anything in excess of 85 degrees was a problem, so he let the heater run—about eight hours, in all. No one had told him that the gauge’s limit was 85 degrees. That’s as high as it could measure. Thus the technician could not tell that temperatures inside the tank were actually rising toward a peak of approximately 1,000 degrees Fahrenheit, because the safety switch had failed.

It had failed because of one small but crucial lapse in communication. Eight years earlier, in 1962, North American had awarded Beech Aircraft a subcontract to build the cryo tanks for the service module. The subcontract specified that the assembly was to use 28-volt D.C. power. Beech Aircraft in turn gave a small switch manufacturer a subcontract to supply the thermostatic safety switches, similarly specifying 28 volts. In 1965, North American instructed Beech to change the tank so that it could use a 65-volt D.C. power supply, the type that would be used at K.S.C. during checkout. Beech did so, neglecting, however, to inform its subcontractor to change the power specification for their thermostatic safety switches. No one from Beech, North American, or NASA ever noticed this omission.

On all the Apollo flights up through Twelve, the switches had not had to open. When the tanks were pressurized with cryogens hundreds of degrees below zero, the switches remained cool and closed. When, for the first time in the history of the cryo tanks, the temperature in the tanks rose high enough to trigger the switch—as O2 Tank 2 emptied—the switch was instantaneously fused shut by the 65-volt surge of power that it had not been designed to handle. For the eight hours that the heaters remained on, the Teflon insulation on the wires inside the cryo tank baked and cracked open, exposing bare wires.

On the evening of April 13, when Liebergot ordered the cryo stir, some minute shift in the position of two of those bare wires resulted in an electrical short circuit, which in turn ignited the Teflon, heating the liquid oxygen. About sixteen seconds later, the pressure in O2 Tank 2 began to rise. The Teflon materials burned up toward the dome of the tank, where a larger amount of Teflon was concentrated, and the fire within the tank, fed by the liquid oxygen it was heating, grew fierce. In the final four seconds of this sequence, the pressure exceeded the limits of the tank and blew its dome off, jarring the shelf above it with a force of 86 g’s for about eleven microseconds, and slamming shut the reactant valves on Fuel Cell 1 and Fuel Cell 3. Then the Teflon insulation between the inner and outer shells of the tank caught fire, as did the Mylar lining in the interior of the service module.

The resulting gases blew out one of the panels in the service module. That explosion also probably broke a small line that fed a pressure sensor on the outside of O2 Tank 1, opening a small leak.

Once the service module panel blew out, the vacuum of space extinguished the fire. All the crew knew was that something had made a loud bang and jolted the spacecraft. Actually, the crew of Thirteen was exceedingly lucky. The explosive force could have broken the tension ties holding the command module to the service module, depriving Odyssey of the precious few hours the remaining fuel cell gave them. It could have cracked the heat shield. Or the wiring in the tank could have short-circuited later in the mission, after the LEM had already been used for the lunar landing. If the explosion had occurred while the LEM was on the lunar surface, the result would have been especially ghoulish, with two healthy astronauts stranded on the moon while the command module and its pilot died overhead.

The rise in pressure in O2 Tank 2 that preceded the explosion had been deceptively normal. First the pressure rose for twenty-four seconds, then it stabilized. Even if Liebergot, Sheaks, or Bliss had noticed the rise in O2 pressure during this period, it would not necessarily have caught their attention. A rise in pressure was, in and of itself, part of a normal fluctuation. For the next fifteen seconds, the pressure held steady. Then it rose again for another thirty seconds. Liebergot, Sheaks, and Bliss were still concentrating on the quantities shown in the tanks of hydrogen—the readings for which they had requested the cryo stir in the first place. The readings for the O2 tanks were also at the bottom of the screen, just to the left of the ones for the hydrogen.

At this moment, there was no light to blink on and alert the controllers to the changing pressure. The EECOMs had set up a yellow warning light on the EECOM console to indicate a change in pressure in the cryo tanks, but it was a pay-attention light that went on whenever the pressures were moving markedly up or down, which they did frequently, and on this occasion the warning light was already lit because of changing pressure in the hydrogen tank.

So none of the three noticed the numbers for O2 Tank 2 during four particularly crucial seconds. At 55 hours, 54 minutes, and 44 seconds into the mission, the pressure stood at 996 p.s.i.—high, but still within the accepted limits. One second later, it peaked at 1,008 p.s.i. By 55:54:48, it had fallen to 19 p.s.i. During those same four seconds, the temperature in the tank went from –329 to +84 degrees Fahrenheit. If one of them had seen the pressure continue on through the outer limits, then plunge, he would have been able to deduce that O2 Tank 2 had exploded. It would have been a comparatively small leap to hypothesize that the explosion had damaged the piping from the second O2 tank as well. And once they had been able to conceive of something having occurred that disabled both oxygen tanks, then the problems reported in the electrical system would have made sense.

Sy Liebergot had, in his estimation, failed to live up to the controller’s code. Two numbers among the fifty-four parameters on his CRYO TAB screen had silently changed—or more precisely, many of the numbers had silently changed, but two of them had changed anomalously—and, at a time when he had reason to be looking elsewhere, Liebergot had not noticed. His two E.C.S. men in the back room hadn’t noticed either, but that didn’t make Liebergot feel any better. Every night for the two weeks after the accident, he was awakened by a nightmare. In the dream, he was in the MOCR, the Odyssey’s crew reported that they had a problem, he looked at the screen only to see a mass of meaningless numbers, and then he relived the next anguishing hour.

After two weeks of the nightmare, the dream changed. In the new dream, which he had only once, Liebergot looked at the screen before the bang and saw the pressure rising. He realized that the rise was abnormally fast. “Flight,” he called to Kranz, “pressure’s going up in O2 Tank 2. Think we have a failed-on heater. Tell the crew to turn off the heater.”

The crew turned off the heater, and the pressure kept going up. Liebergot said, “Flight, have them pull the breakers on panel 226.” The crew pulled the breakers. Then the tank blew, and Liebergot saw the pressure drop and told Flight exactly what had happened. And then everything else occurred just as it had in reality—for noticing would have saved some time in figuring out what had gone wrong, but it could not have prevented the crippling of Apollo 13.

The nightmares stopped. Except for that, however, Sy Liebergot didn’t feel much better. A flight controller was supposed to notice everything, all the time.

Chapter 28. “You don’t have time to worry”

Glynn Lunney had been in the Control Center even before the explosion, reading the flight log in the MOCR and poking around the back rooms, as was his custom before taking a shift. Fourteen minutes into the crisis, when Lovell reported that something was venting, Kranz told his assistant flight director to get hold of Lunney and let him know what was going on. From then until the time he took over, Lunney watched from a seat beside Kranz, just as the rest of the Black Team’s controllers watched from chairs pulled up next to their counterparts. “Sort of a dawning was going on,” Lunney said, “as Gene worked the problem with the guys and I sat there and listened to it… . It wasn’t a thing where immediately you knew, ‘Boy, we’ve blown the tanks and we gotta get this thing back from the moon and power up the LEM.’” The Control Center reacted cautiously, Lunney said, “and properly so. You don’t want to jump off the deep end.”

When Lunney took the console at sixty-nine minutes after the explosion, he was determined to keep the C.S.M. alive. Odyssey was partially powered down, but all its crucial life-support systems were still operating off the one remaining fuel cell. If one of the oxygen tanks and one of the fuel cells could be kept on line, they could sustain that configuration all the way back to earth. For the first minutes of his shift, Lunney concentrated on that possibility. Repeatedly, he pushed Clint Burton, the Black Team’s EECOM, to come up with new ways of dealing with the failing fuel cells and the dropping oxygen pressure. First of all, was Burton sure that the dropping pressure in O2 Tank 2 was legitimate? Yes, Burton was. What confirming information did he have? The temperature was rising, as it would if the pressure was falling.

Lunney was persistent because the next step they were contemplating was shutting off the reactant valve in Fuel Cell 1, as they had done already in Fuel Cell 3. If they shut it off and then came up with an Aaron-like solution that suddenly got the O2 pressures back up, the door would still be closed on two-thirds of the C.S.M.’s power supply. It was like shooting a lame horse if you were stranded in the middle of a desert. It might be the smart thing to do, but it was awfully final. Lunney, like Kranz before him, had no way of knowing that the explosion had instantaneously closed the reactant valves on both Fuel Cell 1 and Fuel Cell 3.

At ten minutes into his shift, seventy-nine minutes after the explosion, Lunney was close to exhausting the alternatives.

“You’re ready for that now, sure, absolutely, EECOM?” Lunney asked.

“That’s it, Flight.”

“It [the oxygen pressure] is still going down and it’s not possible that the thing is sorta bottoming out, is it?”

“Well, the rate is slower, but we have less pressure too, so we would expect it to be a little bit slower.”

“You are sure then, you want to close it?”

“Seems to me we have no choice, Flight.”

“Well…”

Burton, under this onslaught, polled his back room one last time. They all agreed.

“We’re go on that, Flight.”

“Okay, that’s your best judgment, we think we ought to close that off, huh?”

“That’s affirmative.”

Lunney finally acquiesced. “Okay. Fuel Cell 1 reactants coming off.”

It was uncharacteristic behavior by Lunney—“stalling,” he would later call it. “Just to be sure. Because it was clear that we were at the ragged edge of being able to get this thing back… . That whole night, I had a sense of containing events as best we could so as not to make a serious mistake and let it get worse.”

Throughout the long evening, Swigert’s voice never sounded so despondent as it did a minute later when he reported from Odyssey: “Fuel Cell 1 is closed.”

Though he continued to seek a way to hold on to the C.S.M., Lunney was now thinking about the LEM, Aquarius, with its independent guidance, control, and environmental systems. He called TELMU on the loop.

“TELMU, Flight.”

“Go, Flight.”

“Is there anything simple that we can refer the crew to, to get them thinking about using the LEM here?” Lunney asked. “Or have you got anything in the checklist paperwork to describe to them what your intentions are?”

“Negative,” TELMU replied. “There is nothing documented in [the crew’s contingency procedures]. We’re thinking about using the LEM as a lifeboat. We have some procedures here on the ground, though.”

“I’m sure you do,” said Lunney. “What do they amount to? Flying with the tunnel open?”

“Rog. Just a LEM low-power load supplying power to the C.S.M.”

At this point, the MOCR’s thinking about the lifeboat procedure was still collectively confused. Theoretically, there were two ways to do it: Either the crew could power up the LEM and live in it, or the LEM’s batteries could be used to keep the C.S.M.’s systems going. Instinctively, TELMU and some others in the MOCR had thought first that evening about using Aquarius to power Odyssey. When Lunney asked, TELMU was still off on that tangent. But using Aquarius for that purpose wasn’t really feasible. The C.S.M. was set up to supply power to the LEM, not the other way around. The MER would soon figure out how to reverse the process, but there was no off-the-shelf procedure. Furthermore, Odyssey’s systems were power-hungry. Aquarius’s batteries couldn’t possibly feed them for long enough. Lunney had not thought through all of this in detail, but he was suspicious.