Mission Control: Apollo 13’s only hope
Stranded in space, the astronauts were dependant on Mission Control to bring them home. Rod Pyle charts how it wrested success from failure
NASA’s team on the ground worked tirelessly to get Apollo 13’s crew home safely
Amidst the funereal atmosphere at NASA’s Mission Control Center in the days following the Apollo 1 fire in 1967, flight director Gene Kranz gathered his flight controllers and associated personnel in Building 30 to talk to them about the fire. His words, though not recorded, have since been memorialised as “The Kranz Dictum”.
In part, he said: “Spaceflight will never tolerate carelessness, incapacity, and neglect… From this day forward, Flight Control will be known by two words: ‘Tough’ and ‘Competent’. Tough means we are forever accountable for what we do or what we fail to do. We will never again compromise our responsibilities. Every time we walk into Mission Control, we will know what we stand for. Competent means we will never take anything for granted. We will never be found short in our knowledge and in our skills. Mission Control will be perfect.” And he meant it.
On 14 April 1970 at 03:08 UT the personnel of Mission Control were about to earn their ‘Tough’ and ‘Competent’
stripes once again. Just over two days into the mission, Jack Swigert radioed down from the Apollo 13 command module Odyssey, “Okay, Houston, we’ve had a problem here.” The CAPCOM (capsule communicator), fellow astronaut Jack Lousma, asked him to repeat his message. Then Jim Lovell, the commander of the mission, said the words that still send a chill down the spine some 50 years later: “Houston, we’ve had a problem…”
State of emergency
Kranz was just handing off to the next shift of Mission Control personnel, led by fellow flight director Glynn Lunney, when the call came down. As Kranz later wrote, “In the [Mission Control Center], you can’t see, smell, or touch a crisis except through the telemetry and the crew’s voice reports. But you can feel some instinct kicking in when something very wrong is going on.” Something very wrong had just occurred.
After a muffled bang, two of the three fuel cells that powered the command
It took 15 minutes for Mission Control to determine the scope of what was now an in-flight emergency
module had shut down, and the interior of the command module was awash with the blaring of the master alarm and warning lights blazing across the console. What was not yet clear was that one of two large oxygen tanks in the service module – which were critical not just for life support, but also for power via the fuel cells — had exploded due to a spark from a faulty thermostat inside. To make matters worse, the piping from the second tank had been damaged. In less than three hours, both tanks would be empty, the oxygen supply depleted, and the command module dead and cold as a meat freezer.
It took about 15 minutes for Mission Control to determine the scope of what was now an in-flight emergency. The strange numeric readouts that the flight controllers were seeing on their screens had coalesced into an understandable set of problems, and those controllers – whose average age was just 27 – were now working in tight coordination to get their crew home. They were backed by dozens of other experts in the ‘back rooms’ of Building 30 at the Johnson Space Center, and by engineers and experts from the various contractors all over the country.
High stakes
The spacecraft was about 300,000km from Earth, and just 72,000km from the Moon. Decisions would have to be made quickly. Fortunately, Mission Control already had a plan in hand, informally referred to as the ‘lunar module lifeboat’ plan.
Kranz’s White Team (each of the three shifts were colour-coded) gathered up all the data available to them, then turned over the control room to Lunney’s Black Team. “I wanted to get the White Team off-line, get them together in a quiet corner, nail down the cause, and then start on a plan to rescue the crew,” he later said.
At this point, they had two options: a direct abort, which would involve firing up the main engine on the service module and performing a long burn to blunt their velocity and send them back to Earth without flying past the Moon, or allowing the spacecraft to sling past the Moon – an option called ‘free return’ – to hurtle Earthward with the assist of lunar gravity and navigation provided by the lunar module’s smaller descent engine.
While both options were considered, there were concerns about power and worries that the service module’s main engine might have been damaged by the explosion and could in turn blow up if ignited. A direct abort would also necessitate jettisoning the lunar module, an option few were comfortable with. The best option, it seemed, was to allow the spacecraft to loop the Moon. But that would take two additional days in space and oxygen, water (needed for drinking and cooling the hot 1960s electronics), and power (the lunar module ran off
batteries) were in short supply. At least one of these commodities would come up 36 hours short.
Kranz’s White Team relocated to another room to discuss options and find solutions. Controllers carried reams of data printouts, cigarette smoke filled the air, and dozens of voices competed for attention. Kranz commanded the room to silence and asked three engineers to come front and centre — Arnie Aldrich, Bill Peters, and John Aaron.
Rising to the challenge
Kranz declared that the White Team was now offline — they would return to Mission Control only for critical mission events. He assigned Aldrich to build the rescue mission timeline, Peters to oversee the use of the lunar module as a lifeboat, and Aaron to budget life support, water and power. “Whatever any of these three ask of you, you will do,” he told the room.
He then added, “When you leave this room you will pass no uncertainty to our people. They must become believers if we are to succeed.” Strong leadership and a sense of inevitable victory were as critical as the numbers now. “Flight Control will never lose an American in space,” he added with a steely glare.
By the time Kranz returned to Mission Control, he learned that they would have to use the rapidly depleting lunar module batteries keep the powerhungry guidance computer running until their mid-course burn many hours away. John Aaron’s challenge was now a near-impossibility, and he would not return to his console until re-entry days later.
A day after the explosion and two hours after passing the Moon, the crew performed the burn that would put them on a proper return trajectory for Earth. Success was by no means a foregone conclusion — the combined lunar module/command service module ‘stack’ was never designed to be manoeuvred by the lunar module’s main engine. But, as with most contingencies, it had been planned for, simulated and even tested on Apollo 9.
But with one problem solved, another took its place almost immediately. The carbon dioxide levels inside the spacecraft were rising to toxic levels. The CO2 scrubbers on the lunar module were depleted, and the crew would soon need to use the scrubbers from the command module. The lunar module’s filters were round, however, and those on the command module were square — they were not interchangeable. Fortunately, there had been a simulation prior to Apollo 8 that involved a similar problem, and fellow astronaut Joe Kerwin, who was familiar with the procedure, quickly brought everyone up to speed. The crew would fabricate an adaptor using a sock, plastic bags, a sheet of cardboard and duct tape. The fix worked and CO2 levels gradually fell as the adapted scrubber did its work.
There were also astronauts in the command module simulator testing re-entry procedures for the
stricken spacecraft – it would have to be revived from the dead to complete the trip home. This would be touch-and-go, as the crew was dehydrated, sleep deprived and they were enduring near-freezing temperatures – all conditions which could conspire to trip up critical manoeuvres. Their list of procedures was 39 pages long, all 400 steps would have to go right for success. Mission Control, and the many people and organisations that backed them, worked tirelessly to make it as foolproof as possible. As Kranz had predicted after Apollo 1, Mission Control would indeed be perfect.
Final stretch
On 17 April, in the dead of night – not that day or night meant much to any of the sleep-deprived controllers now – Kranz’s White Team took to their consoles for the final stretch. Most of the White Team members
had been working almost continuously for the past 80 hours with short naps to take the edge off. Caffeine and tobacco held them together as the last of the long list of procedures were read up to the exhausted crew by the CAPCOM, who was surrounded by three other astronauts to make sure there were no errors.
Then the service module was ejected, and the crew saw that the damage stretched from its top down across the rocket nozzle. Kranz, and many others, were doubly glad that they had not elected to attempt the direct abort — the service module’s engine might well have exploded.
Kranz polled his team and gave the order: “Go for entry.” Not that there were many alternatives. Apollo 13 was headed into the atmosphere like a freight train going 40,000 km/h. The room grew mostly still until Swigert radioed down, “I know all of us here want to thank all you guys down there for the very fine job you did.” More than one controller was misty-eyed.
Then the crew went silent, as Apollo 13 descended into blackout, the period in which radio communications are obliterated by the fury of re-entry. As Kranz later put it, “Everything was now irreversible.” All Mission Control, and the millions across the nation and the planet who were listening in, could do now was to wait.
Shortly after the countdown timer passed 00:00:00, CAPCOM Joe Kerwin attempted to contact the crew: “Odyssey, Houston. Standing by.” Nothing but static answered him. One minute passed, then another 30 seconds ticked by. Increasingly anxious, Kranz inquired if the clocks were accurate... they were. He slammed his fist on his console, drawing surprised looks from tense controllers.
Finally, after more attempts at contact, they heard “Okay, Joe,” from Swigert. Cheers erupted as three parachutes blossomed into view. In Mission Control and the viewing room, in the support rooms, at the many contractors across the nation, and in public spaces from New York’s Grand Central Station to countless places across the world, people clapped, cheered and exalted in the moment. The emergency of Apollo 13 was over – human ingenuity and spirit had triumphed in space once again.
Completely spent, Kranz slumped in his government-issue chair. The hard-as-nails flight director loosened his grip for a moment and cried. He tried to hold it in, but it was for naught. Days of stress, anxiety and concern spilled out in a warm rush of gratitude.
“Our crew was home,” he recalled. “We – crew, contractors, controllers – had done the impossible. The human factor had carried the day.”