Richard Lawrence - The Mammoth Book of Space Exploration and Disaster

“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 wisps of steam wafting from its cooling system. The tendrils of vapor that the water-based sublimator emitted as it carried excess heat off into space had never disturbed a LEM’s trajectory, but only because the lander was typically not powered up until it was already in lunar orbit, ready to separate from the mother ship and descend to the surface. For such a short haul trip, the invisible plume of steam would not be strong enough to nudge the lander in any one direction. Over the course of a slow 240,000-mile glide back to Earth, however, the almost unmeasurable thrust would be more than enough to alter the spacecraft’s flight path, pushing it out of its reentry corridor altogether.

On Friday, 17 July at 10.43 am it was time for separation from the damaged service module.

“Aquarius, Houston,” Joe Kerwin called from the Capcom station.

“Go, Joe,” Fred Haise answered.

“I have attitudes and angles for service module separation if you want to copy. You don’t need a pad for it, just any old blank sheet of paper will do.”

In the spacecraft, Lovell, Haise and Swigert were in their accustomed positions, all awake and all feeling reasonably alert. Lovell had decided against the Dexedrine tablets Slayton had prescribed for his crew last night, knowing that the lift from the stimulants would be only fleeting, and the subsequent letdown would leave them feeling even worse than they did now. For the time being, the commander had decided that the astronauts would get by on adrenaline alone. Haise, his cheeks still flushed by fever, needed the adrenaline rush more than his crewmates, and at the moment he appeared to be getting it.

“Go ahead Houston,” he said, tearing a piece of paper from a flight plan and producing his pen.

“OK, the procedure reads as follows: First, maneuver the LEM to the following attitude: roll, 000 degrees: pitch, 91.3 degrees; yaw, 000 degrees.” Haise scribbled quickly and did not immediately respond. “Do you want those attitudes repeated, Fred?”