Sy Liebergot was a NASA flight controller on EECOM (originally standing for Electrical, Environmental, Communications but after Apollo 10 became Electrical, Environmental and Consumables Manager) during the Apollo 8 – 15 missions, Skylab and the Apollo-Soyuz Test Program.  He has also contributed to the Shuttle program and ISS.  Most notably, he was the EECOM flight controller, when on the last hour of his shift, the Oxygen tank aboard Apollo 13 exploded placing the crew in jeopardy.  Today, I’ve heard his his talk, Apollo 13 The Longest Hour, and his actions during this crisis and differences from the Ron Howard film.

Organised by, the talk was held in Sheffield and prior to the main talk, was able to have a chat with spaceflight historian Phill Parker and look at some genuine Apollo hardware on display including a prototype Lunar boot, comms headset and a Mission Control Centre console, have a photo with Sy and buy raffle tickets for some fantastic prizes signed by NASA veterans Gene Kranz and Chris Kraft.  A nice little touch was the ticket as a replica of the mission control pass.

Sy Liebergot at Mission Control.
Sy Liebergot at Mission Control.

The following is my attempt at writing down his talk:  A Flight Controller can be considered as ground astronauts, that’s what we considered, our astronaut colleagues didn’t consider that at all. My mission experience I worked from the very beginning of Apollo right through to the very end, all of Skylab, ASTP (Apollo Soyuz Test Project) when we first met the Russians in space, which I felt was a stunt at that time and early shuttle.  I discovered I didn’t have another mission in me to watch the data from a  spacecraft just boring holes in the sky as NASA found out when they had a high attrition rate after that.  But I get a chance to talk to you guys about what it was like back in those golden days.  I’m starting with a shameless promotion for my book and what it was like to be a flight controller and what we went through, tell you some anecdotes you will not have seen.  There is a tendency to gloss over, especially in NASA, certain occurrences that may be embarrassing.  This is not a tell all book, the things I experienced, the pranks I performed and the kind of things NASA hates, they can’t hurt me I’m now retired (recalls a memory of Apollo 14 when Bruce McCandless being a bit of a screw up on CapCom).

I call this talk “The Longest Hour” because it all occurred on the last hour of my eight-hour shift.  I will assume that most of you have seen the Apollo 13 movie, most of us were thankful to Ron Howard for re-energising interest in space.  The movie was not a documentary, not obliged to be accurate, it was a drama.  They can take artistic licenses with effects and I’ll point out some of those.  What I’m going to do now is show you how much artistic licence he took when he had his brother Clint Howard portray me in the movie.  Boy, I gotta tell you, that’s brutal. What he did do though was strive for authenticity for the props, so it’s a pretty much exact depiction of my EECOM console.

A shameless promotion of Sy Liebergot's book.
A shameless promotion of Sy Liebergot’s book.

The first Saturn 5 launch, an unmanned mission called Apollo 4, the first time we flew Saturn 5 all up.  Walter Kronkite from CBS wanted to be there and wanted to be within a mile of the launchpad.  well, the blast radius if it exploded on the pad was 3 miles.  So he said maybe he better not do that.  instead they built him a  shack about 3 and half miles away, made of plywood and big sheet glass or an observation window so he could observe and report on it (plays audio recording of Saturn 5 launch and Walter Kronkite “my god the building shaking, the floor is shaking, the roar is terrific, part of our roof is coming down”…)

Back then, we were young, fearless and ready to go to the moon.  Nobody had ever told us young engineers that we couldn’t successfully land humans on another planet.  Guess what we would do today, today we have a phrase that’s crept in on our modern-day lexicon after we killed the astronauts on Apollo, on Shuttle’s Challenger and Columbia and that phrase is Risk Aversion. There are too many people out there who will tell you that you can’t do this. I’ve been asked if I think we’ll go back to the moon and my opinion is no, it’ll never happen again to the United States.  It may happen to the Chinese with their borrowed/stolen/copied hardware/software.  Just stay away from the Apollo 11 landing site and don’t bring back souvenirs.  It’ll happen.

Sy Liebergot at the EECOM console.
Sy Liebergot at the EECOM console.

Mission Control is where it all happens, the original building. The 2nd and 3rd floors were identical control centres where you could run missions.  The 3rd floor is where we ran all the lunar landing missions. 2nd floor was mainly low earth orbit missions, like ASTP and Gemini. The only constraint was that we didn’t have enough people, I guess that’s how I became a flight controller.  It’s a tiered structure, the more important you were, the higher up the level.  Youve got the lower level which is the flight dynamics level and the booster guys.  The next level, flight surgeons, who were worthless, then there’s CapCom and my console.

The Flight Surgeons, never came to training, non operations didn’t know anything about the mission except that they had 3 crew members going to the moon.  During Gemini, Chris Kraft decided he would test the flight surgeons and they were doing a simulated earth orbit mission and they played a tape of an actual heart attack onto their monitor.  he called down to the Flight Surgeon “Hey how’s the crew looking?”  The guy is looking straight at the monitor while the heart attack is occurring and he said “they look fine Flight.”

The head flight controller is charge is our Flight Director, he orchestrated all of our inputs, had 26 of us working directly under him and we would report to him.  You’d tell him the problem, tell him the impact and that way he can then direct the rest of us to take action.  In addition, I had people working in the back room who had greater analytical ability, greater knowledge so they reported to me, it was hierarchical.  I was on EECOM, a radio call sign that dates from Mercury – Electrical, Environmental and Consumables which is the breathing oxygen the crew used, the oxygen and hydrogen in the fuels cells consumed that produced electricity and water, all critical life support systems.  That’s roughly half of all the systems on the spacecraft.  We EECOM’s became very good system engineers learning how the other systems worked so when there was a problem we could appreciate the effect it would have on the spacecraft.  If nobody would speak up for a the problem, the Flight Director would say “that’s yours isn’t it EECOM?”

Apollo era headset comms provided by space historian Phil Parker.
Apollo era headset comms provided by space historian Phil Parker.

Apollo 13 launched April 11 1971. the third lunar landing mission. Commanded by Jim Lovell who had already been around the moon on Apollo 8, hoping to land it this time, Fred Haise was the lunar module pilot who was to land with Jim Lovell and Jack Swigert was the Command Module Pilot.  In the film, Jack Swigert was depicted to be a bumbling ill trained astronaut that couldn’t even dock his thumb in a bottle of beer.  That was so far from the truth, he knew more about the CSM spacecraft than Ken Mattingly.  That depiction was not fair to the memory of Jack Swigert.

It was about 9 o’clock at night central standard time in the US, just over 200,000 miles away on the way to the moon.  On the screen is the television transmission, Fred Haise is doing his first entry into the Lunar Module.  There are no extra people in Mission Control.  The first 7 hours of my 8 hour shift rolled by uneventfully, the last hour of our shift was to put the crew to bed.  Certain things had to be done in the last hour, then they began their 8 hour sleep period, the relief EECOM would come in and relieve us and babysit the spacecraft while the crew slept.  The last hour of the crews sleep period where they woke up and the last hour of the new teams activity was to go through the post sleep checklist.  One of the things they did was to stir the cryotanks, the phrase is stir cryo’s.  The reason for this is because the cryo material is like slush and in zero gravity top used to stratify in layers of density. So once a day stir these tanks, using the little fans in the tanks.

Gene Kranz was my Flight Director, nicknamed General Savage.  I had a couple of simple housekeeping things I needed to get done before they began their sleep period. We had 3 NiCAD batteries which self discharge to power the spacecraft, so we had to keep them topped up and rotate the batteries.  We had a problem with the fuel readout for Oxygen tank 2.  At about 47 hours into the mission, the oxygen readout on that tank failed but we didn’t worry about that because both tanks were stirred simultaneously, so if the readout from one tank failed, you could go off the reading off the other tank.  We stirred the cryo’s again at 49 hours, though we could knock something loose but nothing happened.  We got to my shift at 55.5 hours I decided I wanted more data and wanted it stirring now and requested an extra stir (plays audio recording).  Kranz never requested why or questioned my request, he knew that If I was asking for it, I needed it.

Mission Control during the television transmission from Apollo 13 shortly before the explosion.
Mission Control during the television transmission from Apollo 13 shortly before the explosion.

Jack Swigert the Command Module Pilot, threw those four switches for about a minute. Unfortunately in this case the O2 tank blew up.  A spark occurred and the side of the spacecraft was blow off, shock was so great it slammed the mechanical feed cells, we didn’t have any telemetry readout on the position of these valves, we didn’t know what had happened to them except that they had looked like they had died but we weren’t willing to accept that.  We went through a ton of troubleshooting to figure out what happened.  The side of the spacecraft blew off, the panel impacted  the high gain antennae which cut our data rate down and it also probably damaged the service propulsion engine.

At 55 and 53 minutes we had a problem.  Swigert reported “OK Houston we’ve had a problem here” followed by Jim Lovell saying “Houston we’ve had a problem.”  Past tense – different to the film, present tense sounds more dramatic for film.  Flight Director Kranz asked me if what I was seeing was most of the data on my console looked unreliable or static.  It looked to me like an instrumentation problem, who would think that a tank made of beryllium with 100% reliability had blown up – it just didn’t happen.  I said “we’ve got some instrumentation Flight, let me add ’em up.”  Within a minute, other flight controllers began to report their problems, jet firings, valves were closed, computer hardware restart, onboard warning Klaxons sounding.  A giant cascading multiple failure (plays audio from Mission Control).

Turns out me saying we may have an instrumentation problem is the greatest understatement in the history of spaceflight.  It couldn’t have been any further from this, a deadly situation.  My peers to this day kid me about that.  Kranz being a great leader decided he needed to settle the team down “lets work the problem and not make it worse by guessing.”  As I looked out on my data screens and listened to the other reports, the fuels cells were being starved and we were looking at irreversible failure within a minute.  The single remaining fuel cell number 2 was still operating but the oxygen it required was rapidly leaking away. So now 2/3 of the electrical power generation system was dead would soon learn that  we only had 3 hours remaining if life.

Apollo 13 Service Module after separation showing the damage from the oxygen tank explosion.
Apollo 13 Service Module after separation showing the damage from the oxygen tank explosion.

It was a very tense time once the failure occurred and I had no quick answers which I was expected to have.  As EECOM I felt very much the spotlight and could feel the pressure well up.  I firmed my grip on the security handles of my console.  As it dawned on me we were in a life threatening situation, I started thinking we might want to get the crew in the lunar module which was still unpowered.  We were very fortunate in having the option of using the lunar module as a lifeboat.  Two minutes seemed like two hours, time dilation under great stress.  I said to Flight “I’ve got a feeling we’ve lost the two fuel cells, I hate to put it that way, I don’t why we’ve lost them, it doesn’t all tag up, it’s not an instrumentation problem, that the best I can tell right now.”  We didn’t have any data to tell us what was going wrong.

This was the news the astronauts dreaded to hear, the possibility of a lunar landing was definitely gone because we only had one fuel cell, we always wanted redundancy.  I believed that fuel cell 3 was the likely source of the oxygen leak with all our troubleshooting and need to isolate it.  i explained this to Kranz and recommended both oxygen and nitrogen feed valves to fuel cell 3 be closed.  Fred Haise knowing the consequences of closing the valves repeated the request and stating “did I hear you right?”  Finally at 46 minutes into the emergency, I controlled the tone of my voice so it didn’t betray my growing despair, informed Kranz that the pressure in O2 tank has dropped down to 297 psi and we’d better think about getting in the LEM.  The normal pressure for oxygen tank was about 900 psi.  I wasn’t a LEM guy but I knew enough that we needed to take action very quickly (plays audio).

Sy Liebergot gripping the handle on the EECOM console. He states that this was due to the pressure he was under from the situation after the explosion.
Sy Liebergot gripping the handle on the EECOM console. He states that this was due to the pressure he was under from the situation after the explosion.

Kranz realised at this point the best thing to do was get off the console and let Flight Director Glynn Lunney and his relief team who were already there, overlapping shifts by 30 minutes so my relief EECOM was already up to speed.  Kranz was very disciplined and handed over to a fresh team.  We got off console and went to look at the data.  Turns out my estimate for that stir probably couldn’t have occurred at a better time.  If it had occurred earlier before we pulled the lunar module out, they wouldn’t have been able to access that and would have died.  The tank blew up at 55 hours and 53 minutes.  if I hadn’t done that it wouldn’t necessarily have blown up when the crew woke up 8 hours later, there’s nothing to say it would have occurred when we turned on the lunar module and went down to the lunar surface.

The next 4 days were filled with technical details on living in the lunar module and creating crew procedures for the trip home, how to control the carbon dioxide build up while the astronauts lived in miserable conditions for 4 days, like living in your refrigerator, had to do a propulsive maneuver otherwise would have missed the Earth.  Finally the astronauts would soon r-enter the earths atmosphere and the final high drama was about to begin.  We held our collective breath as the power systems were turned on one by one, it was frozen, the batteries were frozen and by golly it worked.  About and hour and half before splashdown, we jettisoned the lunar module with Joe Kerwin who was CAPCOM saying “Farewell Aquarius and we thank you.”

We watched the telemetry data become static as the plasma built up around the spacecraft from heating an entered communications black out.  It was expected to come out of blackout at around 3 minutes but it didn’t.  3 minutes became 4 minutes, at 5 minutes we thought we’d lost them after all that.  At about 6 minutes, they reported on the chutes.  We didn’t cheer, that wasn’t what we do. Never celebrated until the crew stepped out on to the deck of the recovery carrier, that was our tradition.  We were sat here watching it, happy, the mission was a success – not a successful failure. Our job was to bring them back alive.

In the Houston Post, in the horoscope page, it said for Aquarius: Do surprises turn you on, then this is the day for the unexpected.

Related Links:

Sy Liebergot homepage

Ken Mattingly – The Spirit and Triumph of Apollo 13

Meeting the Moonwalker Alan Bean


Nick Cook. Amateur astronomer, space, history, nerd, extreme dog walker, cat slave, severe tinnitus sufferer. 13.7 billion years in the making - not that much better for it.

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