iv The paper did not account for an Apollo astronaut’s hundreds of post-mission banquets with mandatory steak and dessert.
v SCE stood for “signal conditioning equipment.”
13
1972—From Rovers to Regrets
Marlowe Cassetti recalls standing in his yard during an especially stressful Apollo mission. A neighbor had been watching the tense updates on television, and he asked Marlowe, “What are you going to do if this doesn’t work?”
“I tried to keep a positive outlook,” Cassetti says, but he didn’t lie, and NASA had been open with the public about the mission’s peril. He stepped his neighbor through the mission’s status and its narrow path to survival. The neighbor shook his head. “Marlowe, you don’t make it sound too good.”
Apollo 13 was a near tragedy and arguably the most famous of all NASA’s adventures. To a greater extent than most other engineers, Cassetti understood exactly how much oxygen and how much electrical power a wounded spacecraft would need to survive. “When I was looking over the numbers and talked to the flight controllers,” he says now, “it was bewildering. I thought there’s a good chance we’re not going to get these guys home alive. Of course, I never said that out loud.”
For a brief time, the imperiled mission brought American viewers back to Apollo, if only for the drama of three men in space, fighting long odds and relying on round-the-clock problem-solving back home.
In fact, the entire world followed Apollo 13. If America’s enthusiasm had waned after the first landing, interest remained fervent abroad. NASA took Moon rocks, some spacecraft, and astronauts on a world tour, drawing incredible crowds at every stop. At the 1970 World Expo in Japan, people waited up to seven hours, forming a line a half-mile long, just to see a Moon rock behind Plexiglas, along with the Apollo 8 capsule that had trekked half a million miles in space.
At home, NASA set up an Apollo display on wheels, and it embarked on a fifty-state, one-year tour. This extended van raised side wings to display exhibits; by the end of its journey, more than three million Americans had strolled past to view various program artifacts. Yet, even a year after the first landing, Apollo was rocketing to its end. Due to funding cuts, NASA elected to eliminate the last three planned missions, leaving five flights to span 1970–1972. Many engineers were shocked when they heard that mission 17 would be the last.
In preparing for Apollo 13 in early 1970, technicians had assembled the mule-like service module. Among other supplies, it carried two tanks of liquid oxygen. These provided astronauts their breathing sustenance and fed the fuel cells to generate electricity for the Moon missions. After running various tests to make sure the tanks were leakproof, a technician’s grip slipped and one medicine-ball-sized tank dropped to the floor with a loud plunk. It fell just two inches and looked fine, so they continued their work.
Whatever injuries the tank may or may not have suffered, it was definitely cursed. And stepping through its story provides a glimpse into the incredible layers of Apollo’s technical detail, each fraught with potential disasters.
Once snug in the service module at Cape Canaveral, the tank showed itself to be stubborn. Technicians filled it and then emptied it as part of routine preparations. But the tank refused to lose its last few gallons of liquid oxygen. Wasn’t this a bad sign? NASA officials had to make a devil’s choice—one of many. If they started tearing apart the oxygen system, that could delay their launch. But more importantly, extra tinkering with the service module could damage other equipment, including the second oxygen tank. Engineers thought the tank’s problem was probably a slightly loose interior tube, and on its own, that shouldn’t jeopardize a mission. NASA decided to keep this oxygen tank and march onward. To fully empty it, the engineers used an interior heater to simply boil any residual liquid oxygen away.
But now an insidious detail, lurking in deep technical weeds, bit the agency. The Cape had upgraded launch pad electrical lines to triple their original voltage. And while NASA had sent this detail along to the tank manufacturer, the numbers were buried with countless other myopic specs. In short (electrical pun regretted) engineers force-fed the tank’s heater three times the voltage it expected.i As technicians warmed the tank, they let the heater run about eight hours. The tank’s little thermostat couldn’t handle the new excess voltage, and it fused into a permanently “on” position. Without alerting anyone, the tank rose to a temperature of about 800˚ Fahrenheit, melting some of the wires’ insulation. None the wiser, engineers refilled the empty tank before launch, and Apollo 13 carried a broken tank, with newly bared wires immersed in liquid oxygen, into space.1
The astronauts completed their first maneuvers without incident. They pointed themselves on a path to the Moon and twirled barbecue style for the next two days. Eventually, with the Moon growing larger in the capsule windows, an astronaut marched through his checklist and hit a switch to stir the oxygen tank: routine business in the realm of zero gravity. But this jolt of current through the tank’s damaged wires cooked up a small fire. Nearly two hundred thousand miles away from Earth, the astronauts heard a loud bang, like nothing they’d heard before from control thrusters or simulations or anything else. They’d actually heard the oxygen tank explode.
The night shift had started in Houston. Engineers tried to sift through very odd data coming from the Apollo instruments and the reports from confused astronauts. It looked like they were rapidly losing their oxygen supply. “First of all, we thought we’d boil it down to something simple and obvious,” engineer Arnold Aldridge recalled later. “As it went along, it became clear it was more extensive.” He made a phone call to John Aaron, the youngster who’d seen a pattern in the data noise after Apollo 12’s lightning strike.2
Aaron recalls being “at home, shaving . . . after spending a long shift at the Control Center.” The new shift updated him rapid-fire. They thought they were facing an instrument problem or “flaky readouts”—there was no way the disturbing data could be real. Aaron asked to hear the numbers from various systems, one at a time, over the phone. “That’s not an instrumentation problem,” he told them. “It’s a real problem.” Thinking back on it, he saw his distance from the Control Center as good fortune. He could stand there calmly in his bedroom and try to see the entire forest. “Everyone was glued to his own tube, and he was digging into his own area deeper and deeper and deeper.” But Aaron thought Occam’s razor was showing them something sinister in the simplest explanation. “You guys are wasting your time,” he told them. “You really need to understand that the [spacecraft] is dying.”3
Once they believed the readouts, the engineers immediately started thinking through the problems. They’d already lost most of the stored oxygen in the service module. Chris Kraft had moved into more of a managerial role in Apollo, but he returned to the trenches now. Kraft realized that those tanks were connected to the three smaller oxygen tanks in the astronauts’ command module. In happier times, those tanks kept a nice supply of oxygen near the crew, but now it meant the awful opposite: they were surely draining backward through their ruptured sibling. He called out, “Seal ’em off,” and saved precious gallons of oxygen. But the prospects remained grim. In the words of one engineer, if they had seen such a scenario during a practice mission, “we’d have said, ‘Well, you can kiss those guys goodbye.’ ”
As word spread through the ranks by phone, everyone who could possibly help swarmed to the center. Aaron got dressed and drove in. Aldo Bordano, in his early twenties, remembered the phone call. “It was 11:30 or something like that,” he said. He drove the ten or so miles back to the center. “All of a sudden, it was about midnight, it was just a line of cars with their lights on. And that was us. We’d all gotten called in—all three shifts.” He remembers the cars all filing efficiently into the parking lot outside Mission Control and Building 30. “It was a real eerie moment,” he said. “There might have been two hundred of us turning our cars off and walking in at the same pace. Nobody said a wor
d to the guy on the left or the guy on the right. We just went to our stations.”4
The Apollo craft, kicked by the bursting tank, was off course as it approached the Moon. “We decided we had to make a burn real quick because we were going out into space,” Henry Pohl recalled. “And we needed to . . . get on a free return back.” The free return was the ideal figure-eight path. It would glide around the back of the Moon, quicken with the Moon’s extra pull, and sling back toward Earth. “At that time, when we made that decision, [it] didn’t look like it was a very good option to bring the crew back alive,” Pohl said. “But it looked like it was a very good option to bring the crew back. You know, at least if they didn’t make it alive, at least they wouldn’t go off and be lost in space forever.”
Scores of engineers started calculating backward. John Aaron became the czar of electricity. With the fuel cells mostly useless now, the engineers had to conserve every bit of electrical power. They knew how much they would need, at minimum, to get the crew capsule to re-enter Earth’s atmosphere at the proper angle. Aaron meticulously worked from that goal, backward, to every minute of the return path, ruthlessly budgeting electricity, and sometimes saying a firm “no” to engineers more than twice his age who wanted more juice for their particular sub-systems. “So we had to cut our energy consumption in half in order to make it back home,” Pohl recalled. “Well, to do that, you’ve got to turn every heater off that you don’t absolutely have to have.” As dramatized in reenactments, the spacecraft was going to get cold, very cold. But freezing the crew wasn’t the only worry.
Like Aaron, Pohl also now had to work backward. The Apollo’s little thruster rockets were one of his main responsibilities. “I calculated . . . how cold the [thrusters] were going to get, and I gave myself four degrees above freezing on it,” he said, recalling his small margin for error. If the propellants froze, it wouldn’t matter how much electrical power the astronauts had at their disposal, because they wouldn’t be able to maneuver. They would be close enough to see the welcoming Pacific Ocean from space but unable to negotiate re-entry, either burning up or bouncing off the atmosphere and sailing helplessly away. In the end, Pohl says his propellant almost froze—it was only two degrees Fahrenheit away from disaster. “We cut those margins pretty dad-gum close.”5
NASA had the astronauts move into the lander for most of the journey, since it had working batteries and its own oxygen supply. While it was designed for all things lunar, this time it drove the whole bus home. Its main engine (designed for landing) and its various thrusters (used for docking and fine adjustments) were fully functional. Even though it wasn’t designed to move around with the rest of Apollo attached—like an acrobat balancing a stack of plates on his head—it worked well enough. And while this is sometimes portrayed as a brilliant last-minute idea, the engineers had game-planned it in advance. It was one of hundreds of practiced horror stories. The lander’s designers had thought about using it as a “lifeboat” from their first musings in 1961. Allowing such a mode required more fuel and oxygen for the lander. But in turn, that provided a fringe benefit: A healthy mission could linger longer on the Moon. And in 1963, the company building the other modules asked if the lander’s thrusters might be able to maneuver all the modules together, in a worst-case scenario where the command and service modules lost power.
Engineer Cynthia Wells (she who had persevered in those all-male math classes) recalled a 1967 NASA assignment: a lifeboat study. In an emergency, how could the lander basically run an entire mission? “Everybody laughed at it,” she said. “Because everyone thought it was so stupid. . . . The flight controllers thought you’d never need to do that.” But just in case, her group calculated, for instance, how long the lander could fully pressurize air in the command module.6
The unlikely had become the only option, and now little details—some helpful, others alarming—came home to roost like never before. With the lander functioning as a lifeboat, it was greatly increasing its planned occupancy time, and engineers wanted the astronauts to snag some extra carbon dioxide filters from the command module. This wasn’t an optional activity to spruce up the air—too much carbon dioxide would be lethal. But with a slap of their foreheads, engineers realized a mismatch: the two modules featured carbon dioxide filters of incompatible shapes. Using only what was available to the astronauts, engineers in Houston figured out how to make an ugly sort of adapter from cardboard and tape, solving a literal square-peg versus round-hole problem.
One step omitted in most dramatizations, however, involved secretaries volunteering for “duties as assigned.” Engineers were worried about describing improvised solutions to tired, shivering astronauts, with tasks well beyond their training. The astronauts weren’t engineers, they’d have no diagrams to consult, and they might get too confused or frustrated to complete the tasks. Engineers placed a secretary who’d never worked on the modules in a room with a pile of Apollo-like supplies, including filters, cardboard, and tape. And then they relayed instructions, describing the fix via phone. After it worked smoothly in Houston, the engineers decided the directions were clear enough to try on the astronauts.7
With the clock ticking in the lander, mission planners looked for options to hasten the return journey. They decided to burn the lander’s main engine, speeding the whole Apollo chain on the far side of the Moon. Authors Murray and Cox describe having the lander trying to push the other modules as “using a small car to push a limousine, but in three dimensions.” (The weight of the combined command and service modules was eight to ten times that of the lander.) On the back side of the Moon, out of communication with Earth, the astronauts started the requested extra burn of the engine, running it for about four long minutes. Once the mission emerged, engineers felt their hopes rising—the burn looked like it had worked perfectly and the astronauts just might make it home. They’d be miserable and cold, to be sure, but they could have just enough air to breathe.8
An animated Max Faget then made a rare entrance into the Mission Control scrum and sparked an argument: It boiled down to engineering versus human physiology. The astronauts were dog tired, having rested little since the start of the crisis.ii Many engineers wanted them to sleep for a few hours, but Faget was adamant. No, he said, Apollo had to enter barbecue mode as soon as possible, no matter the difficulty. (Normally, they used the command and service module thrusters to set the spin. Using the lander’s thrusters posed a new challenge.) Every hour Apollo sailed home without a good spin meant an hour some component facing the sun could be melting and some fuel line facing the void could be freezing. His argument won the day, and the exhausted astronauts, on their second convoluted attempt, coaxed the lander into spinning the wounded Apollo chain into an acceptable, steady rotation.
With no power to spare for cabin comfort, astronauts, with no blankets, suffered plunging temperatures in the lander. Records show a low of 43˚ Fahrenheit, while the abandoned command module sunk below 40˚ Fahrenheit. In addition, to avoid any nudge off their homeward path, engineers asked the astronauts not to make any waste dumps. So, they struggled to find new ways to contain their urine, filling every spare plastic bag from either module. The discomfort of their cold confines, with floating urine bags, combined with prioritizing water for equipment, meant the astronauts slowly became dehydrated as well. One developed a kidney infection.
The entire planet followed the journey home. A dozen or more foreign governments offered their assistance with the coming ocean recovery. In Mission Control, and at Grumman headquarters, engineers took catnaps on top of desks and conference tables, ignoring their managers’ appeals to please go home.
Approaching Earth, the astronauts crawled from the lander to the command module, where they had to wake every system from a chilly and unplanned sleep. Would Pohl’s thrusters work correctly? Would the computer start up? Were the parachutes frozen stuck? Preparing for re-entry, they jettisoned their plucky lifeboat, the lunar module. The astronauts’ last call to Houston befor
e entering the atmosphere thanked the engineers for their incredible work in getting them this far. After tense minutes of radio silence and the incredible (probably welcome) heat of re-entry, Apollo 13 gently splashed down. When all three astronauts emerged, the delirious engineers shouted in celebration.9
Overall, there was surprisingly little finger pointing in the wake of the mission. A stack of small errors had caused a critical tank to explode in flight. Mainly, everyone at NASA felt fortunate. The tank could have easily blown just two days later, with the lander and two astronauts on the Moon and a lone astronaut left in a quickly expiring, powerless ship in lunar orbit. The mission’s lifeboat would have been too far away to help, and they probably would never have made it back alive. As it was, the engineers had just enough time to work the myriad, entangled problems and get the crew home.
Behind the scenes, one could hear a bit of the inter-center tensions emerge when discussing Apollo 13. Each center had its own culture and its own way of doing things, and sometimes they shook their heads at one another. Engineers in Houston and Huntsville had long arguments with personnel at the Cape about their obsessive pre-launch tests. Guy Thibodaux, a longtime friend of Faget’s, recalled his Houston-based view of the Cape. They “always wanted to run tests on everything,” he said, referring to things like repeatedly filling and emptying the oxygen tanks while the rocket waited on the launch pad. He blamed the tank explosion directly on what he considered a ridiculous testing regimen. While the tests gave engineers confidence in those systems on the ground, the tests simultaneously could be wearing or degrading crucial parts and wires.10
The major television networks had been ignoring the routine transmissions from this, ho-hum, third trip to land on the Moon. But the emergency became a multi-day, high-stakes space drama—something the world had never seen. The mission made for a gripping, life-or-death story, racing the twin clocks of oxygen supply and electrical power, with plummeting cabin temperatures aboard a disabled spaceship. The triumph of Apollo 13 highlighted the work of engineers for the general public like no other mission. With the astronauts mainly just shivering for a few days, broadcasts had to at least attempt covering technical challenges, clever emergency fixes, and the years of careful planning that had paid off.
The Apollo Chronicles Page 29