The Mammoth Book of Space Exploration and Disasters

“That,” he said, turning to his crewmates, “was the end of our helium problem.”

They re-established the PTC roll.

At 8 pm on Thursday, 16 April the re-entry angle was beginning to decay again. The Atomic Energy Commission was concerned about a fuel rod in the LEM which should have been left behind on the moon, in the descent stage. Although the LEM would be jettisoned in space it would eventually fall to earth, so the Atomic Energy Commission wanted to ensure that it fell into the deepest water possible.

The food supplies in Odyssey had frozen solid. They had to decide the best way to handle the separation of Odyssey and Aquarius.

When the time came to jettison the service module, they decided Jim Lovell and Fred Haise would stay in the LEM, while Jack Swigert would scramble up into the command module. Moments before separation, Lovell would fire the LEM’s thrusters for a single pulse, pushing the whole spacecraft stack forward. Swigert would then press the button that fired the service module’s pyrotechnic bolts, cutting the huge, useless portion of the ship loose. As soon as he did, Lovell would light his thrusters again, this time in the opposite direction, backing the LEM and its attached command module – with Swigert aboard – away from the drifting service module.

Easier, but no less elegant, was the procedure for jettisoning the LEM. Before a lunar module was released on a normal mission, the astronauts would close the hatch in both the lander itself and the command module, sealing off the tunnel from the cockpits of either ship. The commander would then open a vent in the tunnel, bleeding its atmosphere into space and lowering its pressure to a near vacuum. This would allow the twin vehicles to separate without an eruption of air blowing them uncontrollably apart.

During the flight of Apollo 10 last spring, the controllers had experimented with the idea of leaving the tunnel partially pressurized, so that when the clamps that held the vehicles together were released, the LEM would pop free of the mother ship, but in a slower, more controlled way than it would if the passageway between the two spacecraft was fully pressurized. This method, the controllers figured, would come in handy if a service module ever lost its thrusters. Now, a year later, a service module had done just that and the flight dynamics officers were glad they had the maneuver tucked away in the contingency flight-plan books. Yesterday, the procedure had been explained to Jack Lousma, and the Capcom had proudly relayed it up to Lovell.

“When we jettison the LEM,” he had reported, “we’re going to do it like we did in Apollo 10 – just let the beauty go.”

Lovell had radioed back a far more sceptical “OK.”

Finally Odyssey’s guidance system would have to be realigned for reentry. Normally this angle was checked visually against the arc of the horizon. But Odyssey would arrive on the night time side when the planet was only visible as a dim mass.

But Chuck Deiterich, the Gold Team RETRO, had an idea. “Fellows,” he said to the other flight dynamics men in the staff support room, “tomorrow around lunchtime we’re going to have a problem – specifically, we’re going to be trying to check our attitude against a horizon that isn’t there.”

He turned to the blackboard and drew a large downward arc representing the edge of the Earth. “Now while the Earth will be invisible, the stars will always be there” – he tapped a few chalk dots onto the board above his horizon – “but as fast as the ship will be moving, there might not be time to determine which ones we’re looking at.” He eliminated his stars with a sweep of his eraser.

“Of course, what we’ll also have out there,” Deiterich said, “will be the moon.” He drew a neat little moon above his ragged Earth. “As the spacecraft arcs around the planet and gets closer and closer to the atmosphere, the moon will appear to set.” Deiterich drew another moon below his first one, then another and another and another, each moving closer to the chalk horizon, until the last one vanished partially behind it.

“At some point,” he said, “the moon will set behind the Earth and disappear. It will disappear at the same time whether it’s daytime below or nighttime, whether we can see the horizon or can’t see it.” The RETRO touched the corner of his eraser to the blackboard and carefully erased only the long arc that represented the horizon, leaving all his moons behind. He pointed to the one moon that was half obscured by the horizon that was no longer there.

“If we know the exact second the moon is supposed to disappear, and if our command module pilot tells us it indeed disappears, then gentlemen, our entry attitude is on the mark.”

The temperature in the LEM was so low that the astronauts’ breath fogged the windows, cold making sleep almost impossible.

Deke Slayton was chief astronaut and was deeply concerned about the crew. He had been monitoring Apollo’s power consumption and was confident there was enough power left to power up the LEM. He called the flight director on duty, Milt Windler, to ask if the LEM could be brought back on line early if enough power had been saved. This was confirmed.

Windler called Jack Knight at the TELMU console, who in turn contacted his backroom. Knight’s assistants put him on hold, conducted some quick-and-dirty amp projections, and came back with the good word: the crew was free to switch on their ship.

“Jack, they’re go for power-up,” the backroom called to the TELMU.

“Flight, he can power up if he wants,” the TELMU called to Windler.

Windler relayed this to Lousma: “Capcom, tell him to turn on the lights.”

“Aquarius, Houston,” Lousma called.

“Go ahead, Houston,” Lovell answered.

“OK, skipper. We figured out a way for you to keep warm. We decided to start powering up the LEM now. Just the LEM, though, not the command module. So open your LEM prep checklist and turn to the thirty-minute activation. You copy?”

“Uh, copy,” said Lovell. “And you’re sure we have plenty of electrical power to do this?”

Slayton cut in. “Jim, you’ve got 100 percent margins on everything from here on in.”

“That sounds encouraging.”

The commander turned to his crewmates, gestured to the instrument panel, and with the help of Haise, went into a frenzy of switch-throwing, completing the half-hour power-up in just twenty-one minutes. As soon as Aquarius’s systems came online, the crew could feel the temperature in the frigid cockpit begin to climb. And no sooner did the temperature start to climb than Lovell took a step to make sure it climbed even further. Grabbing his attitude controller, now active again, he spun his ship in a half somersault, so that the sun, which had been falling uselessly on the rump of the service module fell across the face of the LEM.

Almost at once, a yellow-white slash of light flowed into the ship. Lovell turned his face up to it, closed his eyes, and smiled.

“Houston, the sun feels wonderful,” he said “It’s shining straight in the windows, and it’s getting a lot warmer in here already. Thank you very much.”

After the mission they came to some conclusions about the causes of the explosion and the erosion of the descent angle:

But it was only when their engineering hunches were put to the test that they were confirmed. In vacuum chambers at the Space Center in Houston, technicians switched on a heater in a sample tank precisely as Apollo 13’s heater had been switched on and found that the thermostat did in fact fuse shut; they then left the heater on just as Apollo 13’s heater had been left on and found that the Teflon on its wires indeed burned away; finally, they stirred up its cryogenics exactly as Apollo 13’s cryos had been stirred and found that a spark indeed flew from a wire, causing the sample tank to rupture at the neck and blow off the side panel of a sample service module with it.

The only other mystery that had yet to be solved was what had caused the shallowing of the trajectory on the way home, and it was left to the TELMUs to dope this one out. Aquarius, so these flight controllers concluded, had been pushing itself steadily off course, not with some undetected leak from a damaged tank or pipe, but from