thrown accidentally by an errant knee or elbow. The instrument panel readouts were made up primarily of meters, lights, and tiny rectangular windows containing either “gray flags” or “barber poles.” A gray flag was a patch of gray metal that filled the window when a switch was in its ordinary position. A striped flag like a barber pole would take its place when, for whatever reason, that setting had to be changed.
At the astronauts’ backs, behind the heat shield that protected the bottom of the conical command module during re-entry, was the twenty-five-foot, cylindrical service module. Protruding from the back of the service module was the exhaust bell for the ship’s engine. The service module was inaccessible to the astronauts, in much the same way the trailer of a truck is inaccessible to the driver in the cab. (Since the windows of the command module faced forward, the service module was invisible to the astronauts as well). The interior of the service module cylinder was divided into six separate bays, which contained the entrails of the ship – the fuel cells, hydrogen power relay stations, life-support equipment, engine fuel and the guts of the engine itself. It also contained – side by side, on a shelf in bay number four – two oxygen tanks.
At the other end of the command module-service module stack, connected to the top of the command module by an airtight tunnel, was the LEM. The four-legged twenty-three-foot tall craft had an altogether awkward shape that made it look like nothing so much as a gigantic spider. Indeed, during Apollo 9, the lunar module’s maiden flight, the ship was nicknamed “Spider,” and the command module was called by an equally descriptive “Gumdrop.” For Apollo 13, Lovell had opted for names with a little more dignity, selecting “Odyssey” for his command module and “Aquarius” for his LEM. The press had erroneously reported that Aquarius was chosen as a tribute to
“OK,” Lovell said. “Stand by.”
As Lovell prepared for the thruster adjustments and Haise fnished closing down the LEM and drifted through the tunnel back toward Odyssey, Swigert threw the switch to stir all four cryogenic tanks. Back on the ground, Liebergot and his backroom monitored their screens, waiting for the stabilisation in hydrogen pressure that would follow the stir.
Of all the possible disaster scenarios that astronauts and controllers consider in planning a mission, few are more ghastly – or more capricious, or more sudden, or more total, or more feared – than a surprise hit by a rogue meteor. At speeds encountered in Earth orbit, a cosmic sand grain no more than a tenth of an inch across would strike a spacecraft with an energetic wallop equivalent to a bowling ball travelling at 60 miles per hour. The punch that was landed would be an invisible one, but it could be enough to rip a yawning hole in the spacecraft’s skin, releasing in a single sigh the tiny pressure pocket needed to sustain life.
Outside Earth orbit, where speeds could be faster, the danger was even greater. When Apollo astronauts first began travelling to the moon, one thing they dreaded most but spoke of least was the sudden jolt, the sudden tremor, the sudden boot in the bulkhead that indicated their highest of high-tech projectiles and some meandering low-tech projectile had, in a statistically absurd convergence, found each other like the pairs of fused bullets that once littered the battlefields of Gettysburg and Antietam, and had, like the bullets, done each other some serious damage.
In the sixteen seconds following the beginning of the cryostir, the astronauts of Apollo 13 were executing their next maneuvers and awaiting additional commands when a bang-whump-shudder shook the ship. Swigert, strapped in his seat, felt the spacecraft quake beneath him; Lovell, moving about the command module, felt a thunderclap rumble through him; Haise, still in the tunnel, actually saw its walls shift around him. It was nothing that Haise and Swigert had ever experienced before, nor was it anything that Lovell, with his three prior flights and weeks spent in the cosmic deep, had come across either.
Lovell’s first impulse was to be pissed off. Haise! This had to be Haise and his bloody repress valve! Once, maybe, the joke was funny. But twice? Three times? Even allowing for a rookie’s misplaced exuberance, this was pushing things too far. The commander turned toward the tunnel, to find the eyes of his crewman and hold them with an angry glare. But when the two men’s glances locked, it was Lovell who was brought up short. Haise’s eyes were huge, unexpectedly huge, saucer-wide and white on all sides. These weren’t the crinkly, merry eyes of someone who had just gotten off another good one at the expense of the boss and was awaiting a smiley rebuke. Rather, they were the eyes of someone who was frightened – truly, wholly, profoundly frightened.
“It wasn’t me,” Haise croaked out in answer to the commander’s unasked question.
Lovell turned to his left to look at Swigert, but he got nothing. He saw the same confusion here, the same answer here, the same eyes here. Over Swigert’s head, high up in the center section of the command module’s console, an amber warning light flashed on. Simultaneously, an alarm sounded in Haise’s headphone and another warning light, on the right-hand side of the instrument panel where the electrical systems were monitored, began to glow too. Swigert checked the panels and saw that there appeared to be an abrupt and inexplicable loss of power in what the crew called main bus B – one of two main power distribution panels that together provided juice to all of the hardware in the command module. If one bus lost power, it meant that half the systems in the spacecraft could suddenly go dead.
“Hey,” Swigert shouted down to Houston, “we’ve got a problem here.”
“This is Houston, say again please,” Lousma responded.
“Houston, we’ve had a problem,” Lovell repeated for Swigert. “We’ve had a main B bus undervolt.”
“Roger. Main B undervolt. OK, stand by, 13, we’re looking at it.”
Up in the ship, however, the rosy readings that drove these hopes now began to change. Haise, who hadn’t stopped scanning his instruments since the trouble started, caught a glimpse of his bus readouts, and his temporarily high spirits fell. According to Odyssey’s sensors, main bus B, which had appeared to have rallied, had crashed again. Worse, bus A’s readings had begun to fail too. The sick bus, it seemed, was dragging the healthy one down with it. At the same time, Lovell looked over his oxygen tank and fuel cell readings and got even worse news: oxygen tank two, which a moment before had read full to bursting, was reading dry as a bone. Most disturbing, the fuel cell readouts on Odyssey’s instrument panel were the same as they were on Liebergot’s screens, with two of the three cells putting out no juice at all.
At the sight of this last reading, Lovell could have spit. If the fuel cell data were accurate, he could kiss his trip to Fra Mauro goodbye. NASA had a lot of unbreakable rules when it came to lunar landings, and one of the most unbreakable ones was: If you don’t have three in-the-pink fuel you don’t go anywhere. Technically, one cell would probably be enough to do the job safely, but when it came to something as fundamental as power, the Agency liked to have a fluffy cushion, and for NASA even two cells weren’t cushion enough. Lovell caught Swigert’s and Haise’s attention and pointed to the fuel cell readings.
“If these are real,” Lovell said, “the landing’s off.”
Swigert started radioing the bad news down to ground. “We’ve got a main bus A undervolt showing,” he said to Houston. “It’s about twenty-five and a half. Main bus B is reading zip right now.”
“Roger,” Lousma said.
“Fuel cell one and three are both showing gray flags,” Lovell said, “but both are showing zip on the
