Milt Windler, a veteran of three Apollo missions, drew the launch flight director’s assignment. He had earned his spurs as a test director in Kraft’s recovery division and not in Mission Control. His transition was smooth. Absolutely unruffled at the console, Milt emulated Charlesworth’s low-key and patient demeanor. He was fully in command of his team when the moment came to light the fire on Apollo 13.
The liftoff occurred at 13:13 Central Daylight Time, and proceeded uneventfully through first-stage flight. The five engines of the second stage of the Saturn V ignited and burned smoothly for five and a half minutes. Then the center engine unexpectedly shut down. Milt’s team quickly reviewed the status of the remaining four engines, ran the computations for the new engine cutoff times, and passed them to the crew. When the second-stage engines shut down, the S-IVB stage ignited and got the spacecraft to orbit. After the CSM orbital check-out and updating of the trajectory parameters, Windler gave the Go for translunar injection. We heaved sighs of relief, thinking we had gotten through what probably would be the one major glitch in the mission.
The crew and control teams rapidly settled into the routine. During the early shifts, we watched and worked with Jack Swigert, calibrating his performance and finding him a very capable stand-in for Ken Mattingly.
During the translunar coast period both crew and controllers prepared for the events scheduled for lunar orbit when things would get quite busy. As the meticulous check-out of spacecraft and trajectory systems continued, the controllers settled into a state of relaxed alertness. The easy banter among flight director, team, and crew would leave a by-stander thinking that none of these guys had a care in the world, when in fact they were maintaining gimlet-eyed focus on the job at hand while gathering their reserves for what lay ahead.
With the exception of the live TV broadcast from Apollo 13, my second shift of the mission was also uneventful. Mattingly had been pestering us for access to the MCC, his medical status still indefinite. I decided that if he was showing symptoms of measles at the time of the EVA, we would put him at the network console on the floor of the control room that was not being used on the mission, directly below us, giving him a chance to listen in but not exposing people to contagion. As the crew concluded its onboard TV broadcast just before 8:00 P.M. Houston time I glanced up to the viewing room, and could see Lovell’s and Haise’s wives and families leaving. Swigert was a bachelor.
Lunney’s Black Team was arriving in the control room and there was a rising hum of conversation as the shift handover process began. After talking to his controllers in the trench, Lunney moved into the seat next to me, reading the flight director log for all events since his last shift. I began preparing my handover summary for him while we were getting the crew and spacecraft configured for the sleep period.
We zipped through the pre-sleep checklist, verifying that each system was set up to enable us to watch over the crew while they slept, monitoring the switch positions and dumping the telemetry records, making sure that once the crew members were asleep we did not have to awaken them. The flight activities officer got a verbal confirmation from the crew for the completion of each checklist page. With little else to do, I was following the checklist closely.
Earlier on the shift we had a worrisome but minor communications glitch. For a brief period, the CSM high- gain antenna did not work in either of two automatic modes and had to be positioned manually. Then when a spacecraft roll maneuver was performed the antenna abruptly locked up. Now, all of a sudden, it was working properly. There was insufficient time to troubleshoot this glitch prior to the crew’s going to sleep. I hated to leave this as an open item for Lunney.
The crew continued the close-out, terminating the command module battery charge. During the previous sleep period, an alarm monitoring pressure in a hydrogen tank had awakened the crew. After considerable debate in the MCC, we did not reset the alarm out of concern that it might inadvertently trigger again and wake up the crew. As a result, a cryo pressure warning indication was illuminated in the spacecraft and also on Sy Liebergot’s console. During the translunar phase we were in continuous voice and data communications, so Sy intended to stand watch over the pressures from the ground during crew sleep.
Liebergot was my EECOM, having moved up to the front line during Apollo 8. Now, after a year’s experience, he was considered a veteran controller. He had a second glitch he was working. The telemetry gauge in oxygen tank 2 had been reading normal at 80 percent through the mission, then during our shift the gauge went through four rapid up-and-down cycles, finally failing and sticking at a constant reading of 100 percent. We no longer had a valid reading from the sensor.
Cryogenic oxygen and hydrogen mixed and reacted in the three fuel cells in the service module to provide electrical power. The reaction also provided pure water used for drinking and for cooling the CSM systems. The only other source of power to the command module was the three reentry batteries, normally used only for the final two hours of the mission. The oxygen and hydrogen, maintained in a liquid state at temperatures below-300 degrees Fahrenheit, were stored as liquids in spherical tanks insulated by a vacuum between the outer and inner walls. As the mission progressed, the oxygen and hydrogen went through a progressive change from a liquid to a gas.
At the time of launch the cryogenics in the service module tanks were a dense super-cold liquid, but now, two days into Apollo 13, the cryos were a thick soupy vapor, part liquid and part gas. Fans were located internal to the cryogenic hydrogen and oxygen tanks. The fans were periodically activated by the crew, at the request of the MCC, to stir up the mixture and allow precise tank quantity measurements. Heaters were located in the tanks to raise the tank pressure. The heaters could be activated either automatically or manually by the crew.
Sy Liebergot, wrestling with the oxygen pressure management problem and hoping to avoid an alarm during the sleep period, decided to request a cryo tank stir prior to sleep. The stir request was passed to the crew, with Swigert acknowledging the request. As Swigert started the stir at 55:53, Liebergot focused his attention on the TV monitors displaying the fuel cell currents to nail down the exact time the stir started.
(What we could not know at this time was that a design flaw existed in the heater circuit of the cryogenic tanks. During pre-launch testing, the heater thermostat switch closed and, due to the design flaw, the Teflon insulation on the wiring internal to the tank was damaged. When the tank was serviced for the mission, the bare copper wires in the tank electrical system were submerged in liquid oxygen. Two days after liftoff two of the three conditions for an explosion existed, gaseous oxygen and damaged tank insulation. All that was required to initiate an explosion was a spark.)
Nothing happened for sixteen seconds after Swigert started the cryo stir. Then, inside tank 2, a spark jumped between the wires of the heater circuit. The pressure in the tank rose rapidly. Preoccupied with moni toring the fuel cell currents, Sy Liebergot did not notice the oxygen flow measurements on all three fuel cells fluctuating slowly for eighteen seconds. Then the pressure in oxygen tank 2 began to rise rapidly, but failed to set off a high- pressure alarm in the command module or at Liebergot’s console because the cryo pressure alarm had been disabled for the crew sleep. The tank pressure continued its upward climb, then dropped rapidly. The temperatures in the spherical tanks began to rise rapidly. One minute and fifty-three seconds after the stir began, there was a three-second telemetry data loss. When the data returned, the tank 2 pressure read 19 psi, temperature +84 degrees Fahrenheit. The normal pressure reading is 865-935 psi.
The time was now 55 hours 55 minutes and 04 seconds from launch.
Like rolling thunder, my voice loops came alive: “Flight, we’ve had a computer restart.” Then in the blink of an eye, Swigert said, “We have a problem.” Then other controllers chimed in with bad news. At this point Lovell uttered the ominous words: “Okay, Houston, we have a problem!” In both the MCC and on board the spacecraft, voices were normal, but heart rates had picked up. Seconds later Haise reported, “Right now, Houston, the voltage is—is looking good. And we had a pretty large bang associated with the Caution and Warning.”
In the MCC, 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. By the time I heard Lovell’s report, three controllers had related problems. I was wondering which problem Lovell was reporting, as he started relaying the long list of warning indications from the spacecraft displays. The reports and our experience indicated an electrical glitch. I believed we would quickly nail the problem and get back on track.
I was wrong.
A crisis had begun. Events followed in rapid succession, escalating and complicating the problems as the crew’s situation became increasingly perilous. It was fifteen minutes before we began to comprehend the full scope of the crisis. Once we understood it, we realized that there was not going to be a lunar mission. The mission had
