13 MORE Things That Saved Apollo 13, part 4: Early Entry into the Lander

To celebrate the 45th anniversary of the Apollo 13 mission, Universe Today is featuring “13 MORE Things That Saved Apollo 13,” discussing different turning points of the mission with NASA engineer Jerry Woodfill.

During the first two days of the Apollo 13 mission, it was looking like this was going to be the smoothest flight of the program. As Capcom Joe Kerwin commented at 46:43 Mission Elapsed Time (MET), “The spacecraft is in real good shape as far as we are concerned. We’re bored to tears down here.”

Everything was going well, and in fact the crew was ahead of the timeline. Commander Jim Lovell and Lunar Module Pilot Fred Haise had entered the Aquarius Lunar Module 3 hours earlier than the flight plan had scheduled, wanting to check out the pressure in the helium tank – which had given some erroneous readings in ground tests before the launch. Everything checked out OK.

Opening up Aquarius early may have been one more thing that saved Apollo 13, says NASA engineer Jerry Woodfill.

“The first time the hatches between both vehicles are opened is a time consuming process,” Woodfill told Universe Today. “It’s as though a bank teller is requested to provide a customer access to a safety deposit box behind two locked vault doors.”

The removable hatch in the Odyssey Command Module had to be tied down and stowed before entering the tunnel for access to the second door, the lander’s entry hatch. Time was required for pressure equalization process so that the tunnel, command ship and lander were at one uniform pressure.

Often, there was a putrid, burnt insulation odor when the hatch to the LM was first opened, as previous crews described, so normally time was allowed for the smell to dissipate. All of these tasks were dealt with by about 55 hours MET, much earlier than originally planned. For some reason, the LM Pilot even brought the lander’s activation check list back into the command ship for study, though activation was scheduled hours away.

“Perhaps, this would be Fred Haise’s bedtime book to read preparing himself for sleep,” Woodfill said.

Flight Director Gene Kranz (closest to the camera) watches Fred Haise on a screen in Mission Control during a broadcast back to Earth, just 17 minutes and 42 seconds before the explosion.  Credit: NASA.
Flight Director Gene Kranz (closest to the camera) watches Fred Haise on a screen in Mission Control during a broadcast back to Earth, just 17 minutes and 42 seconds before the explosion. Credit: NASA.

But first, the crew provided a 49-minute TV broadcast showing how easily they moved about in weightlessness in the cramped spacecraft.

Then, it happened. Nine minutes later, at 55:54:56 MET, came the explosion of the oxygen tank in the Service Module. Despite ground and crew efforts to understand the problem, confusion reigned.

13 minutes after the explosion, Lovell looked out one of Odyssey’s windows and reported, “We are venting something out into space,” and quickly the crew and ground controllers knew they were losing oxygen. Without oxygen, the fuel cells that provided all the power to the CM would die. Tank 2, of course, was gone with the explosion and the plumbing on Tank 1 was severed, so the oxygen was bleeding off from that tank, as well.

Capcom Jack Lousma speaks to the crew of Apollo 13 from Mission Control. Credit: NASA.
Capcom Jack Lousma speaks to the crew of Apollo 13 from Mission Control. Credit: NASA.
At one hour, 29 seconds after the explosion, the new Capcom Jack Lousma said after instructions from Flight Director Glynn Lunney, “[The oxygen] is slowly going to zero, and we are starting to think about the LM lifeboat.” From space, astronaut Jack Swigert replied, “That’s what we have been thinking about too.”

At that point, only fifteen minutes of power remained in the Command Module.

“Fifteen minutes more and the entire assemblage might have been a corpse with no radio, no guidance, no oxygen flowing into the cabin to keep Lovell, Haise and Swigert alive,” said Woodfill. “Certainly, it was fortuitous circumstances that led to opening the LM early. Simply consider how much time it would have taken to remove both hatches, stabilize and inspect the tunnel and lander interior. Add to this the time required to power up the lander’s life support systems. As it was, they had an open pathway into a safe haven, a lifeboat, called the lunar lander, crucial to survival.”

If the LM had not been opened, the crew would have likely run out of time before the Command Module’s batteries died, which would have created several problems.

As we discussed five years ago in one of the original “13 Things” articles, all the guidance parameters which would help direct the ailing ship back to Earth were in Odyssey’s computers, and needed to be transferred over to Aquarius. Without power from the fuel cells, they kept the Odyssey alive by using the reentry batteries as an emergency measure. These batteries were designed to be used during reentry when the crew returned to Earth, and were good for limited number of hours during the time the crew would jettison the Service Module and reenter with only the tiny Command Module capsule.

“Those batteries were not ever supposed to be used until they got ready to reenter the Earth’s atmosphere,” said Woodfill. “If those batteries had been depleted, that would have been one of the worst things that could have happened. The crew worked as quickly as they could to transfer the guidance parameters, but any extra time or problem, and we could have been without those batteries. Those batteries were the only way the crew could have survived reentry. This is my take on it, but the time saved by not having to open up the Lunar Module helped those emergency batteries have just enough power in them so they could recharge them and reenter.”

By 58:40 MET, the guidance information from the Command Module computer had been transferred to the LM guidance system, the LM was fully activated and the Command and Service Module systems were turned off.

Mission Control and the crew had successfully managed the first of many “seat of the pant” procedures they would need to do in order to bring the crew of Apollo 13 back home.

Additional articles in this series:

Introduction

Part 1: The Failed Oxygen Quantity Sensor

Part 2: Simultaneous Presence of Kranz and Lunney at the Onset of the Rescue

Part 3: Detuning the Saturn V’s 3rd Stage Radio

Part 4: Early Entry into the Lander

Part 5: The CO2 Partial Pressure Sensor

Part 6: The Mysterious Longer-Than-Expected Communications Blackout

Part 7: Isolating the Surge Tank

Part 8: The Indestructible S-Band/Hi-Gain Antenna

Part 9: Avoiding Gimbal Lock

Part 10: ‘MacGyvering’ with Everyday Items

Part 11: The Caution and Warning System

Part 12: The Trench Band of Brothers

Find all the original “13 Things That Saved Apollo 13″ (published in 2010) at this link.

13 MORE Things That Saved Apollo 13, part 3: Detuning the Saturn V’s 3rd Stage Radio

To celebrate the 45th anniversary of the Apollo 13 mission, Universe Today is featuring “13 MORE Things That Saved Apollo 13,” discussing different turning points of the mission with NASA engineer Jerry Woodfill.

Very quickly after the explosion of Oxygen Tank 2 in Apollo 13’s service module, it became apparent the Odyssey command module was dying. The fuel cells that created power for the Command Module were not working without the oxygen. But over in the Aquarius lunar lander, all the systems were working perfectly. It didn’t take long for Mission Control and the crew to realize the Lunar Module could be used as a lifeboat.

The crew quickly powered up the LM and transferred computer information from Odyssey to Aquarius. But as soon as they brought the LM communications system on line another problem developed.

The Apollo 13 crew couldn’t hear Mission Control.

Screenshot from Apollo footage of Jim Lovell and Jack Swigert. Credit: NASA
Screenshot from Apollo footage of Jim Lovell and Jack Swigert. Credit: NASA

The crew radioed they were getting lots of background static, and at times, they reported communications from the ground were “unreadable.”
Additionally, the Manned Space Flight Network (MSFN) tracking stations around the world were having trouble “hearing” the Apollo 13 spacecraft’s radio broadcasting the tracking data.

“Without reliable knowledge of where the vehicle was or was going might result in disaster,” said NASA engineer Jerry Woodfill.

What was going on?

The dilemma was that two radio systems were using the same frequency. One was the transmitter from the LM’s S-band antenna. The other was the broadcast from the spent third stage of the Saturn V, known as the S-IVB.

The seismic station at the Apollo 12 site. The seismometer monitors the level of ground motion to detect arriving seismic waves. The instrument (left) is protected by metal foil against the varying temperatures on the lunar surface that produce large thermal stresses . Credit: NASA
The seismic station at the Apollo 12 site. The seismometer monitors the level of ground motion to detect arriving seismic waves. The instrument (left) is protected by metal foil against the varying temperatures on the lunar surface that produce large thermal stresses . Credit: NASA

As part of a science experiment, NASA had planned for crashing Apollo 13’s S-IVB into the Moon’s surface. The Apollo 12 mission had left a seismometer on the Moon, and an impact could produce seismic waves that could be registered for hours on these seismometers. This would help scientist to better understand the structure of the Moon’s deep interior.

In Apollo 13’s nominal flight plan, the lander’s communications system would only be turned on once the crew began preparing for the lunar landing. This would have occurred well after the S-IVB had crashed into the Moon. But after the explosion, the flight plan changed dramatically.

The flight profile of an Apollo mission to the Moon, distances not to scale. Note the Saturn V 3rd stage flight path. Credit: NASA.
The flight profile of an Apollo mission to the Moon, distances not to scale. Note the Saturn V 3rd stage flight path. Credit: NASA.

But with both the Saturn IVB and the LM’s transmitters on the same frequency, it was like having two radio stations on the same spot on the dial. Communications systems on both ends were having trouble locking onto the correct signal, and instead were getting static or no signal at all.

The Manned Space Flight Network (MSFN) for the Apollo missions had three 85 foot (26 meter) antennas equally spaced around the world at Goldstone, California, Honeysuckle Creek, Australia and Fresnedillas (near Madrid), Spain.

According to historian Hamish Lindsay at Honeysuckle Creek, there was initial confusion. The technicians at the tracking sites immediately knew what the problem was and how they could fix it, but Mission Control wanted them to try something else.

“The Flight Controllers at Houston wanted us to move the signal from the Lunar Module across to the other side of the Saturn IVB signal to allow for expected doppler changes,” Hamish quoted Bill Wood at the Goldstone Tracking Station. ”Tom Jonas, our receiver-exciter engineer, yelled at me, ‘that’s not going to work! We will end up locking both spacecraft to one up-link and wipe out the telemetry and voice contact with the crew.’”

At that point, without the correct action, Houston lost telemetry with the Saturn IVB and voice contact with the spacecraft crew.

But luckily, the big 64 meter Mars antenna at Goldstone was already being switched over to help with the Apollo emergency and “their narrower beam width managed to discriminate between the two signals and the telemetry and voice links were restored,” said Wood.

That stabilized the communications. But then it was soon time to switch to the tracking station at Honeysuckle Creek.

The Honeysuckle antenna by night. Photo by Hamish Lindsay.
The Honeysuckle antenna by night.
Photo by Hamish Lindsay.

There, Honeysuckle Creek Deputy Director Mike Dinn and John Mitchell, Honeysuckle Shift Supervisor were ready. Both had foreseen a potential problem with the two overlapping frequency systems and before the mission had discussed it with technicians at Goddard Spaceflight Center about what they should do if there was a communication problem of this sort.

When Dinn had been looking for emergency procedures, Mitchell had proposed the theory of getting the LM to switch off and then back on again. Although nothing had been written down, when the emergency arose, Dinn knew what they had to do.

“I advised Houston that the only way out of this mess was to ask the astronauts in the LM to turn off its signal so we could lock on to the Saturn IVB, then turn the LM back on and pull it away from the Saturn signal,” said Dinn.

It took an hour for Mission Control in Houston to agree to the procedure.

“They came back in an hour and told us to go ahead,” said Mitchell, “and Houston transmitted the instructions up to the astronauts ‘in the blind’ hoping the astronauts could hear, as we couldn’t hear them at that moment. The downlink from the spacecraft suddenly disappeared, so we knew they got the message. When we could see the Saturn IV downlink go way out to the prescribed frequency, we put the second uplink on, acquired the LM, put the sidebands on, locked up and tuned away from the Saturn IVB. Then everything worked fine.”

Dinn said they were able to “pull” the frequencies apart by tuning the station transmitters appropriately.

Technicians at the Honeysuckle Creek tracking station near Canberra, Australia work to maintain communications with Apollo 13. Credit: Hamish Lindsay.
Technicians at the Honeysuckle Creek tracking station near Canberra, Australia work to maintain communications with Apollo 13. Credit: Hamish Lindsay.

This action, said Jerry Woodfill, was just one more thing that saved Apollo 13.

“The booster stage’s radio was de-turned sufficiently from the frequency of the LM S-Band so that the NASA Earth Stations recognized the signal required to monitor Apollo 13’s orbit at lunar distances,” explained Woodfill. “This was altogether essential for navigating and monitoring the crucial mid-course correction burn which restored the free-return trajectory as well as the set-up of the subsequent PC+2 burn to speed the trip home needed to conserve water, oxygen and water stores to sustain the crew.”

You can hear some of the garbled communications and Mission Control issuing instructions how to potentially deal with the problem at this link from Honeysuckle Creek’s website.

As for the S-IVB science experiment, the 3rd stage crashed successfully on the Moon, providing some of the first data for understanding the Moon’s interior.

Later, on hearing that the stage had hit the Moon, Apollo 13 Commander Jim Lovell said, “Well, at least one thing worked on this mission!”

(Actually, in spite of the Apollo 13 accident, a total of four science experiments were successfully conducted on Apollo 13.)

In early 2010, NASA’s Lunar Reconnaissance Orbiter spacecraft imaged the crater left by the Apollo 13 S-IVB impact.

On April 14th 1970, the Apollo 13 Saturn IVB upper stage impacted the moon north of Mare Cognitum, at -2.55° latitude, -27.88° East longitude. The impact crater, which is roughly 30 meters in diameter, is clearly visible in the Lunar Reconnaissance Orbiter Camera's (LROC) Narrow Angle Camera image. Credit: NASA/Goddard/Arizona State University.
On April 14th 1970, the Apollo 13 Saturn IVB upper stage impacted the moon north of Mare Cognitum, at -2.55° latitude, -27.88° East longitude. The impact crater, which is roughly 30 meters in diameter, is clearly visible in the Lunar Reconnaissance Orbiter Camera’s (LROC) Narrow Angle Camera image. Credit: NASA/Goddard/Arizona State University.

Thanks to space historian Colin Mackellar from the Honeysuckle Creek website, along with technician Hamish Lindsay and his excellent account of the Honeysuckle Creek Tracking station and their role in the Apollo 13 mission.

You can read a previous article we wrote about Honeysuckle Creek: How We *Really* Watched Television from the Moon.

Additional articles in this series:

Introduction

Part 1: The Failed Oxygen Quantity Sensor

Part 2: Simultaneous Presence of Kranz and Lunney at the Onset of the Rescue

Part 3: Detuning the Saturn V’s 3rd Stage Radio

Part 4: Early Entry into the Lander

Part 5: The CO2 Partial Pressure Sensor

Part 6: The Mysterious Longer-Than-Expected Communications Blackout

Part 7: Isolating the Surge Tank

Part 8: The Indestructible S-Band/Hi-Gain Antenna

Part 9: Avoiding Gimbal Lock

Part 10: ‘MacGyvering’ with Everyday Items

Part 11: The Caution and Warning System

Part 12: The Trench Band of Brothers

Find all the original “13 Things That Saved Apollo 13″ (published in 2010) at this link.

13 MORE Things That Saved Apollo 13, part 2: Simultaneous Presence of Kranz and Lunney at the Onset of the Rescue

To celebrate the 45th anniversary of the Apollo 13 mission, Universe Today is featuring “13 MORE Things That Saved Apollo 13,” discussing different turning points of the mission with NASA engineer Jerry Woodfill.

Understandably, it was chaotic in both Mission Control and in the spacecraft immediately after the oxygen tank exploded in Apollo 13’s Service Module on April 13, 1970.

No one knew what had happened.

“The Apollo 13 failure had occurred so suddenly, so completely with little warning, and affected so many spacecraft systems, that I was overwhelmed,” wrote Sy Liebergot in his book, Apollo EECOM: Journey of a Lifetime. “As I looked at my data and listened to the voice report, nothing seemed to make sense.”

But somehow, within 53 minutes of the explosion, the ship was stabilized and an emergency plan began to evolve.

“Of all of the things that rank at the top of how we got the crew home,” said astronaut Ken Mattingly, who was sidelined from the mission because he might have the measles, “was sound management and leadership.”

Gerry Griffin, Gene Kranz, and Glynn Lunney celebrate the Apollo 13 recovery. Credit: NASA.
Gerry Griffin, Gene Kranz, and Glynn Lunney celebrate the Apollo 13 recovery. Credit: NASA.

By chance, at the time of the explosion, two Flight Directors — Gene Kranz and Glynn Lunney — were present in Mission Control. NASA engineer Jerry Woodfill feels having these two experienced veterans together at the helm at that critical moment was one of the things that helped save the Apollo 13 crew.

“The scenario resulted from the timing,” Woodfill told Universe Today, “with the explosion occurring at 9:08 PM, and Kranz as Flight Director, but with Lunney present to assume the “hand-off” around 10:00 PM. That assured that the expertise of years of flight control leadership was conferring and assessing the situation. The presence of these colleagues, simultaneously, had to be one of the additional thirteen things that saved Apollo 13. With Lunney looking on, the transition was as seamless as a co-pilot taking the helm from a pilot of a 747 passenger jet.”

Woodfill made an additional comparison: “Having the two Flight Directors on hand at that critical moment is like having Michael Jordan and Magic Johnson on a six-man basketball squad and the referee ignoring any fouls their team might make.”

Lunney described the time of the explosion in an oral history project at Johnson Space Center:

“Gene was on the team before me and he had had a long day in terms of hours. …And shortly before his shift was scheduled to end is when the “Houston, we’ve got a problem” report came in. And at first, it was not terribly clear how bad this problem was. And one of the lessons that we had learned was, “Don’t go solving something that you don’t know exists.” You’ve got to be sure … So, it was generally a go slow, let’s not jump to a conclusion, and get going down the wrong path…. We had a number of situations to deal with.”
The “not jumping to conclusions” was equally expressed by Kranz when he told his team, “Let’s solve the problem, but let’s not make it any worse by guessing.”

The presence of Kranz and Lunney, simultaneously, is especially obvious reading Gene Kranz’s book, Failure Is Not an Option.

“Kranz captures the wealth of “brain power” present at the moment of the explosion,” said Woodfill. “Besides both Kranz and Lunney, their entire teams overlapped. Yes, there were two squads on the floor competing with the dire opponents who threatened the crew’s survival.”

The crew’s survival was foremost in the minds of the Flight Directors. “We will never surrender, we will never give up a crew,” Kranz said later.

Apollo astronauts at Mission Control during Apollo 13. Credit: NASA.
Apollo astronauts at Mission Control during Apollo 13. Credit: NASA.

Perhaps, the most obvious evidence of how fortuitous the presence of both Kranz and Lunney was, Kranz recorded on page 316-317 of his book. The pair refuses to accept the more popular but potentially fatal decision (a direct abort) to speed the crew’s return to Earth using the damaged command ship’s engine. The direct abort would have been to jettison the lander and fire the compromised command ship’s engine to potentially quicken the return to Earth by 50 hours.

Mattingly recalled those early minutes in Mission Control after the explosion.

Ken Mattingly in Mission Control. Credit: NASA.
Ken Mattingly in Mission Control. Credit: NASA.

“The philosophy was ‘never get in the way of success,’” said Mattingly, speaking at a 2010 event at the Smithsonian Air and Space Museum. “We had choices, we debated about turning immediately around and coming home or going around the moon. In listening to all of those discussions, we never closed the door about any option of getting home. We didn’t know yet how we were going to get there, but you always make sure you don’t take a step that would jeopardize it.”

And so, with the help of their teams, the two Flight Directors quickly ran through all the options, the pros and cons, and – again – within 53 minutes after the accident they made the decision to have the crew continue their trajectory around the Moon.

Damage to the Apollo 13 spacecraft from the oxygen tank explosion. Credit: NASA
Damage to the Apollo 13 spacecraft from the oxygen tank explosion. Credit: NASA

Later, when Jim Lovell commented on viewing the damaged Service Module when it was jettisoned before the crew re-entered Earth’s atmosphere — “There’s one whole side of that spacecraft missing. Right by the high gain antenna, the whole panel is blown out, almost from the base to the engine,” — it was indeed an ominous look at what might have ensued using it for a quick return to Earth.

Read more about the decision to use the LM for propulsion in an article from the original “13 Things” series here.

By the end of the Lunney team’s shift about ten hours after the explosion, Mission Control had put the vehicle back on an Earth return trajectory, the inertial guidance platform had been transferred to the Lunar Module, and the Lunar Module was stable and powered up for the burn planned the would occur after the crew went around the Moon. “We had a plan for what that maneuver would be, and we had a consumable profile that really left us with reasonable margins at the end,” Lunney said.

Apollo 13's view  from Aquarius as it rounds the Moon, with the Command Module at right. Credit: NASA/Johnson Space Center.
Apollo 13’s view from Aquarius as it rounds the Moon, with the Command Module at right. Credit: NASA/Johnson Space Center.

Kranz described the scene in an interview with historians at the Honeysuckle Creek Tracking Station in Australia:

“We had many problems here – we had a variety of survival problems, we had electrical management, water management, and we had to figure out how to navigate because the stars were occluded by the debris cloud surrounding the spacecraft. Basically we had to turn a two day spacecraft into a four and a half day spacecraft with an extra crewmember to get the crew back home. We were literally working outside the design and test boundaries of the spacecraft so we had to invent everything as we went along.”

A look at the transcripts of the conversations between Flight Controllers, Flight Directors and support engineers in the Mission Evaluation Room reveals the methodical working of the problems by the various teams. Additionally, you can see how seamlessly the teams worked together, and when one shift handed off to another, everything was communicated.

Lunney explains:

“The other thing I would say about it is, and we talked about Flight Directors and teams, equally important was the fact that, during those flights, we had this Operations team that you have seen in the Control Center in the back rooms around it and we sort of had our own way of doing things in our own team, and we were fully prepared to decide whatever had to be decided. But in addition to that, we had the engineering design teams that would follow the flight along and look at various problems that occurred and put their own disposition on them. …That was part of this network of support. People had their certain jobs to do. They knew what it was. They knew how they fit in. And they were anticipating and off doing it.”

Without the leadership of the Flight Directors, keeping the teams focused and on-task, the outcome of the Apollo 13 mission may have been much different.

“It is the experience of these two, Kranz and Lunney, working together which likely saved the crew from what might have been certain death,” said Woodfill.

Additional articles in this series:

Introduction

Part 1: The Failed Oxygen Quantity Sensor

Part 2: Simultaneous Presence of Kranz and Lunney at the Onset of the Rescue

Part 3: Detuning the Saturn V’s 3rd Stage Radio

Part 4: Early Entry into the Lander

Part 5: The CO2 Partial Pressure Sensor

Part 6: The Mysterious Longer-Than-Expected Communications Blackout

Part 7: Isolating the Surge Tank

Part 8: The Indestructible S-Band/Hi-Gain Antenna

Part 9: Avoiding Gimbal Lock

Part 10: ‘MacGyvering’ with Everyday Items

Part 11: The Caution and Warning System

Part 12: The Trench Band of Brothers

Find all the original “13 Things That Saved Apollo 13″ (published in 2010) at this link.

13 MORE Things That Saved Apollo 13, part 1: The Failed Oxygen Quantity Sensor

In our original series 5 years ago on the “13 Things That Saved Apollo 13,” the first item we discussed was the timing of the explosion. As NASA engineer Jerry Woodfill told us, if the tank was going to rupture and the crew was going to survive the ordeal, the explosion couldn’t have happened at a better time.

An explosion earlier in the mission (assuming it would have occurred after Apollo 13 left Earth orbit) would have meant the distance and time to get back to Earth would have been so great that there wouldn’t have been sufficient power, water and oxygen for the crew to survive. An explosion later, perhaps after astronauts Jim Lovell and Fred Haise had already descended to the lunar surface, and all three crew members wouldn’t have been able to use the lunar lander as a lifeboat. Additionally, the two spacecraft likely couldn’t have docked back together, and without the descent stage’s consumables left on the Moon (batteries, oxygen, etc.) that would have been a fruitless endeavor.

Now, for our first article in our subsequent series “13 MORE Things That Saved Apollo 13,” we’re going to revisit that timing, but look more in detail as to WHY the explosion happened when it did, and how it affected the rescue of the crew. The answer lies with the failure of a pressure sensor in Oxygen Tank 2, an issue unrelated to the uninsulated wires in the tank that caused the explosion.

Apollo 13 crew:  Jim Lovell, Jack Swigert and Fred Haise.  Credit: NASA
Apollo 13 crew: Jim Lovell, Jack Swigert and Fred Haise. Credit: NASA

Most who are familiar with the story of Apollo 13 are acquainted with the cause of the explosion, later determined by an accident investigation committee led by Edgar Cortright, Director of the Langley Research Center.

The tank had been dropped five years before the flight of Apollo 13, and no one realized the vent tube on the oxygen tank was jarred out of alignment. After a Count Down Demonstration Test (CDDT) conducted on March 16, 1970 when all systems were tested while the Apollo 13 spacecraft sat atop the Saturn V rocket on the launch-pad, the cold liquid oxygen would not empty out of Oxygen Tank 2 through that flawed vent pipe.

The normal approach was to use gaseous oxygen to push the liquid oxygen out of the tank through the vent pipe. Since that wasn’t working, technicians decided the easiest and quickest way to empty the liquid oxygen would be to boil it off using the heaters in the tank.

A graphic depicting the details of oxygen tank number 2 and the heater and thermostat unit.  Credit: NASA.
A graphic depicting the details of oxygen tank number 2 and the heater and thermostat unit. Credit: NASA.

“In each oxygen tank were heaters and a paddle wheel fan,” Woodfill explained. “The heater and fan (stirrer) device encouraged a portion of the cold liquid 02 to turn into a higher pressure 02 gas and flow into the fuel cells. A fan also known as the cryo-stirrer was powered each time the heater was powered. The fan served to stir the liquid 02 to assure it was uniformly consistent in density.”

To protect the heater from being overly hot, a switch-like device called a relay turned off heater power anytime the temperature exceeded 80 degrees F. Also, there was a temperature gauge which technicians on the ground could monitor if temperature exceeded 80 degree F.

The original Apollo spacecraft worked on 28 volts of electricity, but after the 1967 fire on the Launchpad for Apollo 1, the Apollo spacecraft’s electrical systems had been modified to handle 65 volts from the external ground test equipment. Unfortunately Beech, the tank’s manufacturer failed to change out this tank, and the heater safety switch was still set for 28 volt operation.

“When the heater was powered up to vent the tank, the higher voltage “fused” the relay contacts so that the switch could not turn off power when the temperature of the tank exceeded 80 degrees F (27 C),” said Woodfill.

Additionally, the temperature gauge on the ground test panel only went to 88 degrees F (29.5 C), so no one was aware of this excessive heat.

A graphic of the interior of the Apollo  13 Service Module and the location of the oxygen tanks relative to the other systems. Credit: NASA.
A graphic of the interior of the Apollo 13 Service Module and the location of the oxygen tanks relative to the other systems. Credit: NASA.

“As a result,” said Woodfill, “the heater and the wires which powered it reached estimated temperatures of around 1000 degrees F. (538°C), hot enough to melt the Teflon insulation on the heater wires and leave portions of them bare. Bare wires meant the potential for a short-circuit and an explosion since these wires were immersed in the liquid oxygen.”

Because the tank had been dropped, and because its heater design had not been updated for 65 volt operation, the tank was a virtual bomb, Woodfill said. Anytime power was applied to those heaters to stir the tank’s liquid oxygen, an explosion was possible.

At 55:54:53 Mission Elapsed Time (MET), the crew was asked to conduct a stir of the oxygen tanks. It was then that the damaged wires in Oxygen Tank 2 shorted out and the insulation ignited. The resulting fire rapidly increased pressure beyond its nominal 1,000 psi (7 MPa) limit and either the tank or the tank dome failed.

But back to the quantity sensor on Oxygen Tank 2. For a reason yet to be understood, during the early part of the Apollo 13 flight, the sensor failed. Prior to launch, that Tank 2 quantity sensor was being monitored by the onboard telemetry system, and it apparently worked perfectly.

“The failure of that probe in space is, perhaps, the most important reason Apollo 13’s crew lived,” said Woodfill.

Here’s the explanation of why Woodfill makes that claim.

Cover to the Apollo 13 flight plan. Credit: NASA.
Cover to the Apollo 13 flight plan. Credit: NASA.

Woodfill’s research of Apollo 13 indicated that standard operating procedure (SOP) had Mission Control request a stirring of the cryos approximately every 24 hours. For the Apollo 13 mission, the first stir came about 24 hours into the mission (23:20:23 MET). Ordinarily, the next cryo stir would not be called for until 24 hours later. The heater-cryo stir procedure was done to assure accuracy of the quantity gauge and proper operation of the system through the elimination of O2 stratification. The sensor read more accurately because the stir made the liquid oxygen more uniform and less stratified. After the first stir, 87 % remaining oxygen quantity was indicated, a bit ahead of expectations. The next stir came about a day later, about 46:40 MET.

At the time of this second heater-cryo-stir, Oxygen Tank 2’s quantity sensor failed. Post mission analysis by the investigation committee indicated the failure was not related to the bare heater wires.

The loss of ability to monitor Oxygen Tank 2’s quantity caused mission control to radio to the crew: “(Because the quantity sensor failed,) we’re going to be requesting you stir the cryos every six hours to help gage how much 02 is in tank 2.”

However, Mission Control chose to perform some analysis of the situation in Tank 2 by calling for another stir, not at 53 hours MET but at 47:54:50 MET and still another at 51:07:41 . Because the other oxygen tank, Tank 1, indicated a low pressure, both tanks were stirred at 55:53.

“Count the number of stirs since launch,” Woodfill said. “1. at 23:20:23, 2. at 46:40, 3. at 47:54:50, 4. at 51:07:44 and 5. at 55:53. There were five applications of current to those bare heater wires. The last three occurred over a period of only 8 hours rather than 72 hours. Had it not been for the non-threatening failure of Tank 2’s quantity probe and the low pressure in O2 Tank 1, this would not have been the case.”

Woodfill explained that anyone who has analyzed hardware failures understands that the more frequent and shorter the period between operations of a flawed component hastens ultimate failure. NASA performs stress testing on hundreds of electrical systems using this approach. More frequent power-ups at shorter intervals encourages flawed systems to fail sooner.

The short circuit in Oxygen Tank 2 after the fifth heater-cryo-stir resulted in the explosion of Apollo 13’s Oxygen Tank 2. Had the normal sequence of stirs been performed at 24 hour intervals, and the failure came after the fifth stirring, the explosion would have occurred after the lunar module, the life boat, was no longer available.

“I contend that the quantity sensor malfunction was fortuitous and assured the lander would be present and fully fueled at the time of the disaster,” Woodfill said.

5 heater actuations at 24 hours periods amounts to a MET of 120 hours.

“The lunar lander would have departed for the Moon at 103.5 hours into the mission,” Woodfill said. “At 120 hours into the mission, the crew of Lovell and Haise would have been awakened from their sleep period, having completed their first moon walk eight hours before. They would receive an urgent call from Jack Swigert and/or Mission Control that something was amiss with the Mother ship orbiting the Moon.”

Furthermore, Woodfill surmised, analysis of Swigert’s ship’s problems would likely be clouded by the absence of his two crewmates on the lunar surface. Added problems for Mission Control would have been the interruption of communications each time the command ship went behind the Moon, interrupting the telemetry so crucial to analyzing the failure. When it became evident, the cryogenic system would no longer produce oxygen, water, and electrical power, those command module emergency batteries would have been activated. Likely, Mission Control would have ordered an abort of the lunar lander earlier, but, of course, that would have been futile. Had the tiny lander’s ascent stage rendezvoused and docked with the depleted CM, all the life supporting descent stage consumables would remain on the Moon.

“The nightmare would have the Apollo 13 crew saying their last farewells to their families and friends,” said Woodfill. “One can only speculate how the end might have come.”

And there likely would not have been Apollo 14, 15, 16 and 17 — at least not for a very long time.

Apollo 13 launch. Credit: NASA
Apollo 13 launch. Credit: NASA

Another aspect of the timing of the explosion that Woodfill has considered is, why didn’t the tank explode on the Launchpad?

Following the March 16 CDDT, no additional “power-up” or tests were planned. However, it is not uncommon for pre-launch re-verification to be performed.

“One such re-check might easily have been these heater circuits since they had been used in a non-standard way to empty the oxygen from the cryo tanks after the Countdown Demonstration Test (CDDT) weeks earlier,” Woodfill said. “Such re-do’s often occur for myriad reasons. For Apollo 13, despite the compromised system, none occurred until the craft was safely on its way to the Moon.”

However, such a routine re-test involving cryo stirring would have unknowingly jeopardized the launch vehicle, support persons, or astronaut crew.

Or, if the quantity sensor had failed on the ground, likely the same kind of trouble shooting that was done by Mission Control and the Apollo 13 crew, would have been performed by the KSC ground team.

Had the sensor failed at that time, a series of heater actuations/stirrings would have been executed to trouble-shoot the device.

“Of course, the result would have been the same kind of explosion nearly 55 hours 55 minutes after launch,” Woodfill said. “On the ground, the Apollo 13 explosion could have taken the lives of Lovell and crew if trouble-shooting had been done while the crew awaited launch.”

If the trouble-shooting had been done earlier, with several heater actuations/stirrings during the days before the launch, Woodfill said, “a terrible loss of life would have ensued with, potentially, scores of dedicated Kennedy Space Center aerospace workers bravely attempting to fix the problem. And the towering thirty-six story Saturn 5 would have collapsed earthward in a ball of fire reminiscent of that December 1957 demise of America’s Vanguard rocket.”

“Yes, the fact that the Oxygen Tank 2 quantity sensor did not fail on the launch pad, but failed early in the flight was one of the additional things that saved Apollo 13.”

Read our introduction to this series here.

Additional articles in this series that have now been published:

Introduction

Part 1: The Failed Oxygen Quantity Sensor

Part 2: Simultaneous Presence of Kranz and Lunney at the Onset of the Rescue

Part 3: Detuning the Saturn V’s 3rd Stage Radio

Part 4: Early Entry into the Lander

Part 5: The CO2 Partial Pressure Sensor

Part 6: The Mysterious Longer-Than-Expected Communications Blackout

Part 7: Isolating the Surge Tank

Part 8: The Indestructible S-Band/Hi-Gain Antenna

Part 9: Avoiding Gimbal Lock

Part 10: ‘MacGyvering’ with Everyday Items

Part 11: The Caution and Warning System

Part 12: The Trench Band of Brothers

Find all the original “13 Things That Saved Apollo 13″ (published in 2010) at this link.

13 MORE Things That Saved Apollo 13

“Things had gone real well up to at that point of 55 hours, 54 minutes and 53 seconds (mission elapsed time),” said Apollo 13 astronaut Fred Haise as he recounted the evening of April 13, 1970, the night the Apollo 13’s command module’s oxygen tank exploded, crippling the spacecraft and endangering the three astronauts on board.

“Mission Control had asked for a cryo-stir in the oxygen tank …and Jack threw the switches,” Haise continued. “There was a very loud bang that echoed through the metal hull, and I could hear and see metal popping in the tunnel [between the command module and the lunar lander]… There was a lot of confusion initially because the array of warning lights that were on didn’t resemble anything we have ever thought would represent a credible failure. It wasn’t like anything we were exposed to in the simulations.”

What followed was a four-day ordeal as Haise, Jim Lovell and Jack Swigert struggled to get back to Earth, as thousands of people back on Earth worked around the clock to ensure the astronauts’ safe return.

Jerry Woodfill and Fred Haise at the 40th anniversary celebration of Apollo 13 at JSC.  Image courtesy Jerry Woodfill.
Jerry Woodfill and Fred Haise at the 40th anniversary celebration of Apollo 13 at JSC. Image courtesy Jerry Woodfill.

Haise described the moment of the explosion during an event in 2010 at the Smithsonian Air and Space Museum commemorating the 40th anniversary of the mission that’s been called a successful failure.

In 2010, Universe Today also commemorated the Apollo 13 anniversary with a series of articles titled “13 Things That Saved Apollo 13.” We looked at 13 different items and events that helped turn the failure into success, overcoming the odds to get the crew back home. We interviewed NASA engineer Jerry Woodfill, who helped design the alarm and warning light system for the Apollo program, which Haise described above.

Now, five years later on the 45th anniversary of Apollo 13, Woodfill returns with “13 MORE Things That Saved Apollo 13.” Over the next few weeks, we’ll look at 13 additional things that helped bring the crew home safely.

Jerry Woodfill working in the Apollo Mission Evaluation Room.  Credit:  Jerry Woodfill.
Jerry Woodfill working in the Apollo Mission Evaluation Room. Credit: Jerry Woodfill.

Woodfill has worked for NASA for almost 50 years as an engineer, and is one of 27 people still remaining at Johnson Space Center who were also there for the Apollo program. In the early days of Apollo, Woodfill was the project engineer for the spacecraft switches, gauges, and display and control panels, including the command ship’s warning system.

On that night in April 1970 when the oxygen tank in Apollo 13’s command module exploded, 27-year-old Woodfill sat at his console in the Mission Evaluation Room (MER) at Johnson Space Center, monitoring the caution and warning system.

“It was 9:08 pm, and I looked at the console because it flickered a few times and then I saw a master alarm come on,” Woodfill said. “Initially I thought something was wrong with the alarm system or the instrumentation, but then I heard Jack Swigert in my headset: “Houston, we’ve had a problem,” and then a few moments later, Jim Lovell said the same thing.”

Listen to the audio of communications between the crew and Mission Control at the time of the explosion:

Located in an auxiliary building, the MER housed the engineers who were experts in the spacecrafts’ systems. Should an inexplicable glitch occur, the MER team could be consulted. And when alarms starting ringing, the MER team WAS consulted.

Woodfill has written a webpage detailing the difference between the MER and Misson Control (Mission Operations Control Room, or MOCR).

The Mission Evaluation Room.  Credit: Jerry Woodfill.
The Mission Evaluation Room. Credit: Jerry Woodfill.

The ebullient and endearing Woodfill brings a wealth of knowledge — as well as his love for public outreach for NASA — to everything he does. But also, for the past 45 years he has studied the Apollo 13 mission in intricate detail, examining all the various facets of the rescue by going through flight transcripts, debriefs, and other documents, plus he’s talked to many other people who worked during the mission. Fascinated by the turn of events and individuals involved who turned failure into success, Woodfill has come up with 13 MORE things that saved Apollo 13, in addition to the original 13 he shared with us in 2010.

Woodfill tends to downplay both his role in Apollo 13 and the significance of the MER.

“In the MER, I was never involved or central to the main events which rescued Apollo 13,” Woodfill told Universe Today. “Our group was available for mission support. We weren’t flight controllers, but we were experts. For other missions that were routine we didn’t play that big of a role, but for the Apollo 13 mission, we did play a role.”

But Apollo Flight Director Gene Kranz, also speaking at the 2010 event at the Smithsonian Air and Space Museum, has never forgotten the important role the MER team played.

“The thing that was almost miraculous here [for the rescue], was I think to a great extent, the young controllers, particularly the systems guys who basically invented the discipline of what we now call systems engineering,” Kranz said. “The way these guys all learned their business, … got to know the designs, the people and the spacecraft … and they had to translate all that into useful materials that they could use on console in real time.”

Apollo 13 astronauts Fred Haise, Jim Lovell and Jack Swigert after they splashed down safely. Credit: NASA.
Apollo 13 astronauts Fred Haise, Jim Lovell and Jack Swigert after they splashed down safely. Credit: NASA.

Join Universe Today in celebrating the 45th anniversary of Apollo 13 with Woodfill’s insights as we discuss each of the 13 additional turning points in the mission. And here’s a look back at the original “13 Things That Saved Apollo 13:

Part 1: Timing

Part 2: The Hatch That Wouldn’t Close

Part 3: Charlie Duke’s Measles

Part 4: Using the LM for Propulsion

Part 5: Unexplained Shutdown of the Saturn V Center Engine

Part 6: Navigating by Earth’s Terminator

Part 7: The Apollo 1 Fire

Part 8: The Command Module Wasn’t Severed

Part 9: Position of the Tanks

Part 10: Duct Tape

Part 11: A Hollywood Movie

Part 12: Lunar Orbit Rendezvous

Part 13: The Mission Operations Team

Also:

Your Questions about Apollo 13 Answered by Jerry Woodfill (Part 1)

More Reader Questions about Apollo 13 Answered by Jerry Woodfill (part 2)

Final Round of Apollo 13 Questions Answered by Jerry Woodfill (part 3)

Never Before Published Images of Apollo 13’s Recovery

Final Round of Apollo 13 Questions Answered by Jerry Woodfill

Our readers had questions about our series “13 Things That Saved Apollo 13,” and NASA engineer Jerry Woodfill has graciously answered them. Below is the final round of Q & A with Jerry; but if you missed them, here are part 1 and part 2. Again, our sincere thanks to Jerry Woodfill for not only answering all these questions — in great detail — but for being the impetus and inspiration of the entire series to help us all celebrate the 40th anniversary of Apollo 13.

Question from Dennis Cottle: I am wondering how much information was held back from one division to another in NASA regarding safety aspects of vehicles and for that matter the entire mission . In other words did the left hand have any idea what the right hand was doing in regards to safety?

Jerry Woodfill: One of the greatest achievements of Apollo was the management structure, i.e., how a program involving three main NASA Centers (Manned Spacecraft Center, Marshall Spaceflight Center, and Kennedy Space Center) with dozens of divisions among their civil servants and contractors could achieve a lunar landing. No, I didn’t experience any “holding back of safety information”, but I can vouch for the idea that the right hand DID KNOW what the left hand was doing.

I contend that this is the case because of my experience as the Caution and Warning Project Engineer for both the Command/Service Module and the Lunar Module. Despite Universe Today granting me the unspeakable privilege of explaining Apollo 13, at the time (1965-1972), I was a very-very low level engineer. Yet, when it came to how the management system regarded my opinion and input, I was treated with the same respect and consideration as the Apollo Program Manager. This was the brilliance of the program, intimately involving everyone’s contribution. Such a posture led to ferreting out safety issues. If someone was trying to hide something, another group would relish the opportunity to shine a laser light on the item.

Here are examples: I remember sitting at my desk talking by phone with a Grumman engineer about the status of the lander’s warning electronics. When I looked up, there was Apollo astronaut Jack Lousma standing before me. Jack had a question about one of the caution and warning alarms. On another occasion, the head of the entire Lunar Lander Project at the Manned Spacecraft Center, Owen Morris, called me directly asking how the warning system detected a “run-away” thruster. (Owen was at least five levels above my station at the Manned Spacecraft Center.) Not only do these examples speak to the openness of the Apollo teaming effort, they also reveal how intimately knowledgeable were all levels of workers, from Astronaut to Program Manager. The example of the Apollo 13 team’s fix of the CO2 filter problem, given in the duct tape account, likewise demonstrates the teamwork. Any of us might be consulted to assist. There was nothing hidden from one-another.

I always felt Grumman got a “bad rap” in the movie “Apollo 13” which was altogether undeserved. This regarded the scene about using the descent engine in a novel way for the rescue. Contrary to that scene, the Grumman guys were altogether thorough, cooperative, and excellent engineers…proactive to almost a fault. I’d have treated that scene differently from my experience with the Bethpage GAEC engineers.

Let me cite another example. After the Apollo One tragedy, I was asked to lead a NASA/Grumman team to review what changes need be made to the lander’s warning system. I’d travel to Long Island once a week to meet with the instrumentation group. Earlier, I’d had this thought about one of the Caution and Warning alarms, the Landing Radar Temperature alarm. The way the sensor functioned might cause it to ring a nuisance alarm. This might occur during Armstrong and Aldrin’s moon-walk, leaving the lander unoccupied. My concern was, if the thermal environmental near that sensor behaved “inappropriately”, the alarm would sound, aborting the EVA.

Rushing back to the LM, they’d discover a system no longer used after touchdown had sounded an alarm. This would have wasted, perhaps, an hour of their time. (Can you imagine what an hour of EVA time was worth on Apollo 11’s brief two and one-half hour walk?) I simply mentioned this to Jimmy Riorden, the Grumman manager. He set his guys to work, and they verified my concern. Furthermore, they suggested and implemented a fix, saving the program millions of dollars based on Armstrong and Aldrin’s hourly moonwalk cost. That’s the kind of cooperation that I experienced working with Grumman. This was the norm, not an exception.

Question from ND: To quote from the article, part 5: “While a fix had been planned for Apollo 14, time did not permit its implementation on Apollo 13’s Saturn V.”

But did it really need to be the hindsight of the Apollo 13 launch to know that this was a dangerous thing to do? Was delaying the Apollo 13 launch not an option?

Jerry Woodfill: I’m trying to be generous in giving opinions about those things which proved to be detrimental to Apollo. This is because I wasn’t involved in many of the situations I’ve been asked to discuss. So my answer should be classified as conjecture. In such cases, I’m trying to share examples from my experience where I made a decision which later proved to be the wrong one. The same mechanism which led to Apollo 13’s Oxygen Tank’s explosion probably speaks to your question. Nancy detailed all the series of WRONG THINGS, which, at the time, were considered to be the RIGHT THINGS which led to the explosion.

Yes, in looking back, for sure, the better thing, as you suggest, would be fix the problem and delay the launch. Yet, I’m sure those who made the decision to press forward believed they were justified in moving forward. I have saved most of my notes from day-to-day issues I dealt with on the lander’s warning system from 1966 forward. There are scores of the kinds of decisions I approved. These are like the decision to postpone the pogo fix until Apollo 14.

In fact, the configurations for my warning system differed for LM-1, LM-2, and LM-3 and subsequent landers. LM-5 landed on the Moon. This was the nature of Apollo engineering. I can still review each decision I made with regard to delaying an improvement. Sometimes it was based on meeting a schedule. In other instances, an analysis revealed the problem simply had no impact on the type of mission the LM would have.

Trying to reconstruct my justifications for a system I knew intimately is extremely difficult, even with my notes. So I really can’t confidently address your question other than to say it was probably based on the same kinds of decisions I made, whether good or bad. However, I do recall researching the second stage POGO problem months ago which led to it being included among the “13 Things…” Below is some of what I found:

(For Apollo 13) The four outer engines were run for longer than planned, to compensate for this (POGO). Apollo 14 Launch Operations (comments on Apollo 13 pogo), Moonport: A History of Apollo Launch Facilities and Operations, NASA Engineers later discovered that this was due to dangerous pogo oscillations which might have torn the second stage apart; the engine was experiencing 68g vibrations at 16 hertz, flexing the thrust frame by 3 inches. However, the oscillations caused a sensor to register excessively low average pressure, and the computer shut the engine down automatically.

Pogo, Jim Fenwick, Threshold – Pratt & Whitney Rocketdyne engineering journal of power technology, Spring 1992 : Smaller pogo oscillations had been seen on previous Apollo missions (and had been recognized as a potential problem from the earliest unmanned Titan-Gemini flights), but on Apollo 13 they had been amplified by an unexpected interaction with the cavitation in the turbo-pumps.

Mitigating Pogo on Liquid-Fueled Rockets, Aerospace Corporation Crosslink magazine, Winter 2004 edition : Later missions included anti-pogo modifications, which had been under development since before Apollo 13, that solved the problem. The modifications were the addition of a helium gas reservoir in the center engine liquid oxygen line to dampen pressure oscillations in the line, plus an automatic cutoff for the center engine in case this failed, and simplified propellant valves on all five second-stage engines.

Perhaps, the following sentence in the above summary is the explanation: “…but on Apollo 13 (POGO) had been amplified by an unexpected interaction with the cavitation in the turbo-pumps.”

Question from Cydonia: I always thought, that idea to use SPS and turn 13 around right after explosion was fiction of Apollo 13 movie. Somebody could explain to me, how could SPS be used to do that? They would need to change delta v for some 20 km/s! Doesn’t they?They used whole Saturn V to get half of that. What’s the math to make such maneuver possible?

Jerry Woodfill: Cydonia, recently an excellent paper (referenced in Part 6 of “13 things…) touched briefly on your question. Here is the link to that paper.

Here is information from the paper referring to your question:

B. Direct Return to Earth.

Soon after the incident Mission Control personnel examined direct return to Earth aborts that did not include a lunar fly-by. These burns had to be performed with the SM SPS before ~61 hours GET, when the spacecraft entered the lunar sphere of gravitational influence. Landings in both the Pacific and Atlantic could be made. A direct return to Earth (no lunar fly-by) with a landing at 118 hours GET could only be accomplished by jettisoning the LM and performing a 6,079 foot/second SM SPS burn (Table 2). Abort maneuver data for this burn was already on-board the spacecraft as a part of normal mission procedures. However, this option was unacceptable due to possible damage to the SPS and the necessity of using LM systems and consumables (power, water, oxygen, etc.) for crew survival.

Question from G2309: I’m really enjoying these posts I’ve always found the story fascinating. But what I don’t understand why they didn’t just replace the damaged tank rather than repair it. I understand the tank must be expensive but not compared to the cost of a failed space flight. ‘they couldn’t detect what damage might have occurred on the inside so why take the risk?

Jerry Woodfill: Since Tank 2, despite being “jarred,” exhibited no significant problems in retests, (see the four items below) the consensus was no damage was done. Below are the findings of the NASA Apollo 13 Investigation. I’ve included them as the justification given to your question about “why take the risk?” Indeed, on hindsight, the answer would be in the negative, i.e., don’t take the risk.

1.) It was decided that if the tank could be filled, the leak in the fill line would not be a problem in flight, since it was felt that even a loose tube resulting in an electrical short between the capacitance plates of the quantity gage would result in an energy level too low to cause any other damage.

2.) Replacement of the oxygen shelf in the CM would have been difficult and would have taken at least 45 hours. In addition, shelf replacement would have had the potential of damaging or degrading other elements of the SM in the course of replacement activity. Therefore, the decision was made to test the ability to fill oxygen tank no. 2 on March 30, 1970, twelve days prior to the scheduled Saturday, April 11, launch, so as to be in a position to decide on shelf replacement well before the launch date. Accordingly, flow tests with GOX were run on oxygen tank no. 2 and on oxygen tank no. 1 for comparison. No problems were encountered, and the flow rates in the two tanks were similar. In addition, Beech was asked to test the electrical energy level reached in the event ofa short circuit between plates of the quantity probe capacitance gage. This test showed that very low energy levels would result. On the filling test, oxygen tanks no. 1 and no. 2 were filled with LOX to about 20 percent of capacity on March 30 with no difficulty. Tank no. 1 emptied in the normal manner, but emptying oxygen tank no. 2 again required pressure cycling with the heaters turned on 4-22

3.) As the launch date approached, the oxygen tank no. 2 detanking problem was considered by the Apollo organization. At this point, the “shelf drop” incident on October 21, 1968, at NR was not considered and it was felt that the apparently normal de-tanking which had occurred in 1967 at Beech was not pertinent because it was believed that a different procedure was used by Beech. In fact, however, the last portion of the procedure was quite similar, although a slightly lower GOX pressure was utilized.

4.) Throughout these considerations, which involved technical and management personnel of KSC, MSC, NR, Beech, and NASA Headquarters, emphasis was directed toward the possibility and consequences of a loose fill tube; very little attention was paid to the extended operation of heaters and fans except to note that they apparently operated during and after the detanking sequences. Many of the principals in the discussions were not aware of the extended heater operations. Those that did know the details of the procedure did not consider the possibility of damage due to excessive heat within the tank, and therefore did not advise management officials of any possible consequences of the unusually long heater operations.

Question from Spoodle 58: In your opinion, as you have built the equipment to get man into space, do you think we as a species are being too cautious in our approach to exploring space? Or are we afraid of incidents like Apollo 13 happening again or worse like the shuttle Columbia, or do you think we should just get out there like the explorers of Earth in middle ages, take on space, take on the risk of being in space not just leaving robots and probes doing the work but to get some real people out there?

Jerry Woodfill: I like your question because it is one all of us at NASA continually ask ourselves. This results in a culture which does attempt to learn from past mistakes. It’s like the idea of sins of “omission an commission.” What did I fail to see about Apollo One, Columbia, or Challenger that could have avoided the tragedy? This is a question each of us who worked in any capacity on these vehicles and missions ask ourselves. I know I did.

When we speak of NASA, we are speaking collectively, not of the individuals that comprise the agency. But the thousands of individual employees, (I’m one of them.) are responsible for what you have asked. It’s always easy to hide behind the collective name for us NASA, but actually, it comes down to a single employee or small group who either did something exceptionally beneficial, or, woefully, hurtful. From time-to-time I’ve been in both groups. Over 45 years of NASA employment, I could cite many examples in each category. But most have been satisfactorily reported by the press such that changes have been made for the better.

An example would be the Columbia tragedy. Now, each tile and thermal surface is carefully examined post-launch to insure integrity of the reentry system prior to the orbiter’s return. For Apollo, an extra Oxygen Tank was added independent from the pair which failed. Additionally, a battery with 400 amp hours capacity was added as a backup should the fuel cell system failed. These changes were directly a result of reviewing the mishap so that fixes would be implemented to prevent a recurrence.

On September 12, 1962, I, a Rice junior Electrical Engineering student, listened in Rice Stadium to President John Kennedy. It led to my NASA career. Listen especially carefully about why, as you put it, we should taking on space and taking on the risks:

(This is a video of Jerry Woodfill reciting President Kennedy’s speech at Rice University)

Also, there were several people who had questions about why the damaged Service Module wasn’t jettisoned immediately following the accident (or as soon as it was ascertained that the tank had ruptured).

Jerry Woodfill: I want to congratulate the readers of “13 Things…” Before Nancy suggested I reply to the questions as well as added queries, many of you had already given the right analysis. This was among them: The answer was, “not wanting to expose the heat shield to the severe hot and cold space environment for many days.”

Like the use of the lander’s descent engine, in a new way, the heat shield had not experienced such an extended thermal environment. The thought was, “Why add the risk?” Of course, some would argue that trying to steer the assemblage was extremely difficult with the attached service module. This placed the center of gravity in a cumbersome location for Jim Lovell’s steering via the lander’s thrusters. In fact, at first, Jim had difficulty avoiding what is known as “gimbal-lock”, a condition like a bicycle rider losing balance and falling over. But Jim triumphed over the steering problem faster than most of us can adapt to a new video game joy-stick.

Thanks once again to Jerry Woodfill!

More of Your Apollo 13 Questions Answered by Jerry Woodfill

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Our many thanks to NASA engineer Jerry Woodfill for taking the time to answer questions from our readers about our series on “13 Things That Saved Apollo 13.” Here is part 2 of the questions, and if you missed Part 1, here is the link. That’s Jerry above, in the image with Apollo 13 astronaut Fred Haise. We’ll have one more round of Q & A’s with Jerry in a subsequent post.

Question from Billy Wells: The Apollo astronauts were suffering from being very cold on the way back from the moon – one of them being sick with a fever at that same time. Why didn’t two of them put on the lunar space suits that were on the lunar module ? I would think that would have kept them from being so cold and miserable during that trip home.

Jerry Woodfill: Have you seen the movie “A Christmas Story” about Ralphie and his heart-felt longing for a “Red-Ryder-carbine-action-range-model-lightning-loader-200-shot-air-rifle?” Well the author and I went to the same school, 20 years apart. We even had the same freshman English teacher, Mrs. McCullough. You are wondering what this has to do with cold Apollo 13 astronauts. In the movie, Ralphie’s brother Randy is “space-suited” by his Mom for a walk to school in the frigid northwest Indiana wind-blown environment. (The wind-chill must have made Apollo 13’s cabin feel tropical. I know I experienced it.) Randy’s attire is space-suit-like, bulbous, tight, immobile and wholly uncomfortable. When the lad trips, he is prostrate on his back unable to right himself, his limbs flailing with a dying Texas cockroach.

None of the astronauts, by their comments, enjoyed wearing Apollo spacesuits because of this “Randy-Effect”. In fact, they were only required to don the garments during critical mission phases. During such times, a malfunction-leak in the cabin might cause a loss of pressure and death.

In this series, the replacement of Ken Mattingly by the robust footballer Jack Swigert was discussed earlier. This relates to your question. Yes, the sick Fred Haise needed warming. But the discomfort of the space-suit rather than the comfortable/cooler casual wear was a factor. Besides, as long as Fred remained dry, the casual attire retained his body heat. No breeze was present, and, I’m told, that the actual 98.6 body temperature tended to warm crewmen through radiant body heating. Their inert bodies encapsulated within their casual wear tended to retain radiated body heat. Also, Fred had to record on paper updated procedures. The handicap of a space-suit’s “Randy-Effect” would make writing/printing more difficult.

Someone did a later study about how cold Apollo 13 actually was. I know that 38 degrees F was sort of accepted as the temperature during the rescue. (This was the reported temperature in the far reaches of the dead Command Module quarters where Jack Swigert dwelled.) But other analysis found an environment not nearly as cold, especially in the lander. The customary “barbeque-rotational-solar” heating was always present. Nevertheless, Jim Lovell stated in the 40th Anniversary panel discussion I attended, “I actually did hug Fred to keep him warm as the movie depicts.”

Now back to Randy: My Mom made me wear long-underwear from the same store Ralphie asked Santa Claus for the “Holy Grail of Gifts”, a B-B gun. It was like the multilayered Apollo space-suit underwear. You had to stuff the “long-johns” into your socks so the Lake Michigan wind wouldn’t slice into your ankles like a frozen meat cleaver. Then she insisted on “scratchy” coarse wool pants akin to an astronaut’s outer garment. I think that is why Haise rejected suiting-up in his LEM lander attire. I know I would have rather been a little cold than trussed-up in Mom’s Indiana winter-wear. If I see Fred, I’ll ask him about this. He lives near here. But would you opt for the comfort of what’s pictured below over the more casual astronaut garments worn on Apollo 13?

Question from John McKenna: Are solid rockets affected by POGO as was Apollo 13’s second stage?

Jerry Woodfill: While there is scant evidence of a Pogo-like effect in solid rockets, there is a likewise serious threat of resonant oscillations. It is described as a common shaking problem for solid rocket boosters. The mechanism results from pulses of added acceleration caused by gas vortices. It is akin to the wake generated by a speed-boat. When these vibration vortices resonate with the natural frequencies of the solid rocket motor’s combustion chamber, the combined effect can cause a destructive shaking just as serious as a liquid booster’s POGO threat.

Question from LPScott: Hey Jerry…One of my favorite questions about the Lunar Lander…Why did they end the steps about 3 feet from the surface and make the astronaut leap those last few feet? Why not make the steps go on down to the landing pads? Even if the surface had been softer the last step would just sink in and they would not have had to jump?

Jerry Woodfill: I love this question. Thanks for asking it. The reason I like it is because I was a friend of the NASA engineer responsible for the LM’s landing gear. Unfortunately, I couldn’t locate him for an answer. (I did a Google and Switchboard search. He must have moved away. He retired years ago.) So I’m going to “speculate” slightly from my background with lunar lander engineering. I think, in part, it has to do with the gear’s shock-absorbing design. A “posterior” jarring uneven touch down might be so jolting and uneven as to cause the forward pod to cant significantly. In such an instance, that lower rung of the ladder might jam into a lunar boulder or even an irregular rise in the surface topography. Why chance such a thing? Make the ladder shorter to provide clearance. In one-sixth gravity, that last step is virtually a play ground skip off a children’s playground slide.

But this brings to mind a related account I think Universe Today’s readers will enjoy. Just several months before the July, 1969 landing, Neil Armstrong asked my friend to join him for a meeting with the Apollo Program manager, George Low to discuss the “one small leap (at least, as you said, three feet) for all mankind.” Each lander leg had, of course, landing pods. But what troubled Armstrong were the lunar contact probes extending another 5.6 feet beneath each of them. When they brushed the surface, the display panel lunar contact light would come on. This was the signal that the descent engine could be turned off.

Now, if you’ve watched the video of Buzz Aldrin’s leap backward onto the Moon from that last ladder rung, imagine what would have happened to Armstrong or Aldrin’s air-tight space-suit had the ladder’s leg contact probe bent up saber-style “inappropriately.” That would have spoiled Armstrong’s day. The result of Armstrong, Low, and my friend’s meeting was there would be no contact probe henceforth on any of the LEM’s forward ladder legs, including the Eagle.

Question from Steve Nerlich: Do you know if the scene in the movie “Apollo 13” where the actors all rip their medical telemetry off, in defiance of mission rules, really happened?

Jerry Woodfill: First, let’s review Jim Lovell’s book, renamed Apollo 13 (formerly Lost Moon). BTW, the best answer would come from Fred Haise and Jim Lovell. At times, either man might share what was embellished by Hollywood and what actually happened. For example, at the recent JSC 40th Anniversary panel discussion, Jim said, “That scene where I hugged Fred to warm him really happened.”

I checked the book. Interesting, that I randomly opened to page 269 which answers your question. I won’t quote it here, but I’m sure you have access to a copy. It pretty much answers your question(s) about the med-sensors.

Nevertheless, had I known your question, I’d have asked it at the Q & A at the 40th anniversary celebration. Should I encounter Fred (he lives near JSC.), I’ll ask him the question. But my thought is, “Yes, they removed the uncomfortable sensors, but probably not in the dramatic fashion shown in the film.” I’ve reviewed that cinematic treatment of the rescue dozens of times. Each time, I find something of interest to share with those I give presentations on the topic of the rescue. But generally, the screen play is a reliable recreation of events on board Apollo 13. Perhaps, I should do a “What’s Real/What’s Not” about the movie Apollo 13. While some have already created web-sites listing such, I have many more concerning the displays and caution and warning from my perspective, since I was a project engineer responsible for them. It might be a good way to encourage interest in manned space exploration. So thanks for the question.

Question from Chad: All of the books on Apollo 13 carry a certain tone of absoluteness… When the men of Apollo 13 became stranded, everyone involved seems to recall an attitude of “We Must!” My question is this: Looking back, was that an attitude that was held true at heart, or only projected outwardly. Obviously everyone involved on the ground was going to do EVERYTHING humanly possible to bring those men home safely, but to put it bluntly, failure was most definitely one of the possibilities. How did that weigh on your mind and heart? Did it help you (the plural you) work harder at the problem, or was a hindrance… Kind of a needle in your brain that jabbed at you constantly?

Jerry Woodfill: Chad…I’ll ask you to Google the name “Jerry Bostick”. His comment about how he came to author the phrase “Failure is not an option.” speaks to your question.
Also, I think these accounts kind of speak to what I felt then and still believe about “failure not being an option.”

I’d like to paraphrase and partially quote their content:

A mother and father’s son fell from a tree breaking his spine. The day he broke his spine, doctors said he’d probably be paralyzed for life. His parents said, “no way.” His mother recalled, “One of my comments at that point was from Apollo 13, which was, ‘Failure is not an option.'” Well, with the same resolve exhibited by the movie Apollo 13, the father searched the Internet and found an experimental drug that offered some promise if given within 72 hours of the injury. Like the movie Apollo 13, this was accomplished, but in 76 hours. However, though it seemed like an answer to their prayers, there was no assurance it would work in their son’s case. But it did! And 10 weeks later, he walked out of the hospital. Though doctors could not be sure it was a result of the drug, they admitted it was, as many view the rescue of Apollo 13, something of a miracle.

The second incident deals with the account of a daughter whose father is dying with cancer. She writes in hopes of encouraging others who must care for loved ones on the brink of eternity.

“Well… Apollo 13 has become my role model, my support, my comfort, and my favorite movie at 3 AM when I can’t sleep because I’m so overwhelmed with my own life. I’ve already written a review of Apollo 13 the movie. You can go look it up. I said it was great. I said you should watch it. But this isn’t just a review of the movie. This is about how I have emotionally connected with the movie. This is about how I use the movie as a crutch to get me through the day. This is about how Apollo 13 keeps me sane in an insane time!”

“They say that Apollo 13 was a Successful Failure because of all they learned from the experience. I’m hoping that my experience with cancer will also be a Successful Failure. The doctor has already told us that my dad won’t be cured and any treatments we do won’t change that. So I already know that I’m going to be a failure… Nothing I do can save my father’s life. But maybe I can learn and grow. Just maybe my dad and I can have some more good times together. Maybe we can have some fun and overcome some challenges on this journey. Then I’d say it would be a successful failure for sure. Sometimes I’m surprised at how my life seems to parallel the hardships the astronauts had to endure. I find myself doing things for my dad that I never imaged I would have to do.”

“The one line in Apollo 13 that echoes in my mind is Gene Kranz saying, “Failure is not an option!” I know that he meant they had to bring the astronauts back alive. I also know that my dad is dying and I can’t do anything to change that — except pray for a miracle. I am praying for a miracle, but I also know that I have to be prepared for my dad’s death. However, I still insist that FAILURE IS NOT AN OPTION! So, if death is inevitable — what do I mean? Well, I mean that whatever happens, I have to make sure I don’t give up. I don’t lose sight of the wonderful times we can still have. I don’t lose my humor or my love for life… I have to make sure that I do my best to make every day with my dad as wonderful as possible, that the end of his life is as good as it can be, and we learn something new every day we are together. I also need to remember that no matter how bad things get, I love my daddy and he loves me. If I just remember that… I can’t fail.”

Question from Terry G: With regard to the time constraints placed on the required engineering developments for the Apollo project, what was the greatest of the many engineering breakthrough that kept Apollo on track…which if any of the methods developed for Apollo’s lunar landings could we expect to see reused during the human space flight and landings on an asteroid and Mars?

Jerry Woodfill: The day you submitted this question, Nancy was drafting the best response I can think of – Lunar Orbit Rendezvous. Had America chosen the Direct Ascent Nova Class Rocket technique, I doubt if we would have succeeded in fulfilling President Kennedy’s challenge of reaching the Moon by 1970. Carefully read Account No. 12 in Nancy’s series of essays. It was the number one reason for our triumph!

As far as the second query, I’ll punt on that one, however, Google things like: Hohmann Transfer Orbit, Aldrin Cycler Orbit, and Libration Points. After reading about these techniques, you’ll be an expert on this kind of thing. Each summer, JSC has an event called THE SPACE SETTLEMENT CONTEST. I was one of the technical trainers, in robotics, for the high school students selected to attend. After doing Internet searches using the above search terms, I found a myriad of approaches exist, all having specific merits. Take a look at them. It’s a fascinating study.

Your Questions about Apollo 13 Answered by Jerry Woodfill

Now that our series on “13 Things That Saved Apollo 13” is complete, NASA engineer Jerry Woodfill has graciously agreed to answer questions from our readers. We have a lot of questions, so we will post some of Jerry’s answers today and more over the next few days.

Question from Daniel Roy: Did we ever find out why Apollo 13’s trajectory was too shallow on the way back in spite of TCMs? I have trouble believing that the low impulse/ slow venting/ random pointing from ruptured tanks could explain the delta V.

Jerry Woodfill: The shallowing trajectory resulted from the lunar lander’s cooling system discharging vapor during the coast back to Earth. It was not a result of residual release of remnant gases from service module damage. No Apollo mission returned to Earth with a LM attached except for Apollo 13. For that reason the slight but, nevertheless, noticed contribution to the shallowing entry angle had to be dealt with by the Apollo 13 retro. To this day, I find it remarkable that, though the retro did not know the source of the shallowing, he was certain it would cease after the last corrective compensating burn. And, of course it did, after the LEM was jettisoned.

Question from wjwbudro about how much residual power was provided by the fuel cells after the explosion

Jerry Woodfill: Your question about how much residual power the fuel cells contributed prior to employing the emergency (or some call them reenty batteries) launched me into some research about the chemistry of fuel cell operation. I’ve always shared that the reaction of hydrogen and oxygen produce electricity with two by-products extremely useful to human space exploration, breathable oxygen and water. Both oxygen and hydrogen must be present for the reaction to continue.

For Apollo 13, the sequence of the loss of the ability of the fuel cells to produce power relates to the loss of O2 and H2 entering them. Sy Liebergot has a wonderful CDROM where he deals with “how the data read.” Sy had to contend with analyzing what was going on (IN REAL TIME) with regard to the timing of loss of the O2 cryo-tanks, the fuel cells, etc. Google Sy on the Internet, and you’ll find a wealth of information discussing the issue. My admiration of how Sy dealt with such an overwhelming failure so masterfully continues 40 years after the event. But the bottom line is…no O2 into the cells no water, oxygen, or electrical power out. That was the reason for employing the emergency batteries. The fuel cells weren’t much help after because the rupture of the plumbing caused O2 tank One’s O2 to vent into space after O2 tank 2 exploded (I always say “exploded” though some disagree contending it to be a rapid heating of cryogenic O2 being vented into space, sort of like heating air in an empty sealed container until the vessel ruptures.)

Question from science teacher Christopher Becke from Warhill High School: What were the specs of the onboard computers, both in the LM and the Command Module? What was the clock speed and how much (and what type of) memory did they have? I’m trying to impress upon my students that their graphing calculators are more powerful than the computers that brought astronauts to the moon.

Jerry Woodfill: About a year ago, I felt like comparing Apollo 13’s computer to today’s state of the art. Besides the computers (CSM and LM), the only integrated circuit contained among the millions of spacecraft parts was an octal counter in my lunar lander’s caution and warning system’s brain known as the Caution and Warning Electronic Assembly or C&WEA for short. There was an excellent article I discovered at this link from the Download Squad.

Additionally, a wealth of information is given in the Apollo Experience Report which can be accessed at this link.

These documents are a national treasure for recreating the technical history of Apollo. I authored the warning system portion of the Apollo Experience Report on the lunar lander’s Caution and Warning System.

I recall that the strength of the Apollo computer, though it was a “lightweight” in RAM and Hard-Memory, was its “multi-tasking” ability. (Better than an iPhone, since Apple chose not to include that capability presently in mine.) However, when my warning system began to ring “Program Alarms,” (warnings, five of them to be exact) this multitasking capability proved altogether helpful in making Armstrong the first man on the Moon.

One of the Apollo Computer’s “subtasks” was akin to a kind of low level housekeeping info thing which generated an alarm. But the priority executive routine of providing landing control continued undisturbed. Ignoring the program alarms by Flight Controllers Steve Bales and John Garman was a huge reason Neil Armstrong was first on the Moon, that President Kennedy’s prediction and challenge was fulfilled in that decade, and, most importantly, for me…that I didn’t go down in engineering/aerospace infamy whose warning system sounded a “false-alarm” making Pete Conrad and Allan Bean the first men on the Moon on Apollo 12. Thanks Steve and John!

Question from Greg: Should NASA be spending more time reviewing the Apollo 13 mission and other mishaps in order to better anticipate and respond more effectively to new and unexpected mishaps in future missions?

Jerry Woodfill: The neat thing about every one of these questions is they launch potential investigations which can only help future space travelers. Whether it was Apollo One, Apollo 13, Challenger or Columbia, each tragedy resulted in fixing a later situation which might have been fatal if corrective steps had not been taken to learn from failure. This question is one that I’ve addressed extensively in unpublished books I’ve authored.

Now, regarding failure to fix potentially fatal items; yes, over the course of my 45 year career, it is easy to reflect and study failures after the fact and cite instances where people, groups, circumstances resulted in disaster and tragedy. I’m one of those guilty people. I should have done a better job with regard to the Apollo One warning system. Collectively, and, perhaps, individually, we share the burden of not having done a better job for Gus, Roger, and Ed.

Specifically, I remember the final review at North American of Spacecraft 012 where Ed, Gus, and Roger sat at the front of the conference room. They were included with a NASA review panel determining how to disposition “open items” or “squawks” needing fixing before or after shipment of their Apollo One spacecraft to the Cape.

My warning system was a problem for me because it became sort of the “wolf crying boy” who is always the one to aggravate those who want to ignore a root problem blaming it on the messenger. During the initial factory tests of this, the first of the litter of subsequent Apollo Command modules, there were dozens of times the alarm system sounded Master Alarms.

In summary, virtually none were the fault of the alarm system. But, nevertheless, it was blamed until I could find the actual culprit. Some said, “The electronics are simply too sensitive ringing alarms when all that has happened is a momentary switch actuation causing a brief electrical transient which triggers that Master Alarm.”

After dealing with all the culprits, I had only one unexplained alarm remaining. This was the one I was called to present to the board which included Ed, Gus and Roger. “Next item, O2 FLOW unexplained Caution and Warning Alarm.” It was July of 1966. My wife Betty and I had been married less than a month, and here I was dealing with a life-threatening situation.

To digress here, I think the movie APOLLO 13 would have been better served with this event as the opening scene because all the players in the Apollo program were involved. I remember Apollo 7 crewman Walt Cunningham, one of the Apollo One back-up astronauts along with Wally Schirra and Donn Eisele, rooting around in the Spacecraft 012 mockup. Walt emerged with some kind of handle he had accidentally severed from the ship’s interior. Amazed and disgusted, Walt held it up for all to see. Perhaps, that was a precursor for what was to follow?

My explanation was that the O2 Hi alarm was another of those momentary transient things. I shared that nonthreatening events like a routine turning on of the cyclic accumulator demanded added O2 flow into the cabin actuating the alarm. In fact, in route to the Moon, even a urine-dump would cause the O2 flow to increase ringing the alarm. (Later, that was one of my jobs, to indicate in Apollo 11’s check-list that an O2 Hi master alarm could be expected for that reason.) If it was a problem, it would surface once more during Cape testing and be dealt with then. My assessment was accepted by the board.

On January 27th, 1967, Ed, Gus, and Roger were hours into what was called a “plugs-out” test simulating a voyage to the Moon. Suddenly came the call, “We’ve got a fire in here!” In seconds three men perished. When Deke Slayton arrived later and surveyed the interior of Spacecraft 012, he looked up at the alarm panel. The O2 flow hi light was still on. Likely, the ECS (Environmental Control System) should have called for the high flow of Oxygen feeding the fire, but I will never know if it came on before the fire to warn the astronauts to take action. So that is why I cannot “white-wash” this question because it is simply these kinds of events that result in the failures we have experienced over the course of human space flight. Whenever one happens, it is because of people like me who should have done a better job.

Question from Dirk Alan: My question is about the free return trajectory. After rounding the moon, could a spacecraft head back to earth – travel round the earth and head back to the moon? Could it round the moon and head back to earth again and again ? I’m asking if a space station would be feasible in a circumlunar orbit re-supplied now and again with fuel for course corrections to shuttle between the earth and moon?

Jerry Woodfill: The short answer is yes to all of the above. For Apollo 13, the free return trajectory has been much discussed. I’ve often reflected about it, as well. In fact, the first consideration in the rescue was to return to the free return trajectory after the explosion. (BTW, I think I erred in my No. 12 submittal of the “13 Things..” in suggesting that a lander-less-Apollo 13 would have resulted in cremating the crew days later if the explosion had occurred in the circumstance at 55 hours 54 minutes 54 seconds. They were not in the free return mode at that time having departed from it by an earlier burn.)

In actuality, the crew, shortly after the explosion, used the lander’s descent engine to return to free-return. Recently, in conjunction with Apollo 13’s 40th anniversary, added study has been done. The investigation sought to determine how close Apollo 13 would have come to Earth based on its free-return orbit. Here is the link to a YouTube video summarizing the effort. It’s really neat!

Hey, I just listened once more and watched this again. Apparently, I was right predicting the crew without the lander would have been cremated after all, five weeks later in May of 1970. Don’t ascribe this to any talent I have. It’s just lucky. But watching the video will do much to answer every question you have above about space stations, etc. You might Google other terms like Hohmann Transfer Orbit, Aldrin Cycler Orbit, Libration Points, and Sling-Shot orbits. These are strategies in orbital mechanics considered when planning planetary exploration, manned and unmanned.

Questions from Gadi Eidelheit, Quasy and Tom Nicolaides about the Hatch That Would Not Close

Jerry Woodfill: I’ve shared the account of “the hatch that would not close” virtually every time I’ve shared the Apollo 13 story. ( This is approaching a 1000 talks. Do the math. Simply telling the story once a month for nearly 40 years adds up to nearly 500 times.) One man believed the inability to make the hatch close resulted from differential pressure between the vehicles. I tend to discount that because the hatch had been open for some time stabilizing the interior atmospheric pressure throughout the assemblage.

Others who have considered the problem, think that Jack Swigert and Jim Lovell’s belief that a meteor had punctured the LM caused Jack and Jim’s hasty efforts to be flawed and inexact. The misalignment in the hurried closing was responsible. This was addressed in one of the crew debriefs I reviewed several years ago.

Now, I just had the thought, “The Apollo 13 capsule is available at the Kansas Cosmosphere.” To my knowledge, no one since the rescue has actually tried to reproduce the hatch closing problem. But, again, I simply don’t know if that has been the case. (As we press on, I’m going to be honest about what I know and don’t know. This is one of those things I really can’t answer satisfactorily.)

From Hans-Peter Dollhopf: Question about Why an Apollo 13 Movie and not an Apollo 11 Movie:

Jerry Woodfill: Another question I wanted to address among those left at the close of each of the “13 Things…” articles concerns why a movie was made about Apollo 13 and not about Apollo 11. My thought is because of the circumstance of how the movie came into production. I have a close friend named Jerry Bostick. Jerry was the lead FIDO for Apollo 13. We knew one another through the local Methodist Church, too. Jerry’s son Mike was in one of the Sunday school class sessions I taught.

Well, Mike went on to work for Ron Howard as a producer for Universal Studios. Being familiar with the Apollo 13 rescue because his dad, Jerry Bostick, had played a key role, Mike suggested to Ron Howard that Universal buy the rights to Jim Lovell’s book LOST MOON, for a movie. Incidentally, Jerry Bostick is the source of the quote, “Failure is not an option.”

Google Jerry Bostick’s name, and you’ll be able to read the story. Now had Neil Armstrong’s child worked for Ron Howard, and, if Neil had written a book focused on Apollo 11, it might have competed for an academy award like Apollo 13. Incidentally, there are moments in Apollo 11’s mission just as perilous and potentially fatal as the Apollo 11 mission. Perhaps, Nancy will let me address them in another Universe Today series! I can count a half dozen so it won’t be “11 Things That Saved Apollo 11.”

Question: Didn’t the Soviets Plan also use LOR?

Jerry Woodfill: About the Soviet Direct Ascent approach. Prior to the dismantling of the “iron curtain” and the cooling of the “Cold War”, information about Soviet Manned Space endeavors was sketchy. I found, in 1977, that a Soviet rocket scientist had proposed a lunar orbit rendezvous technique in the early days of rocketry, even before Sputnik. Unfortunately, or fortunately, with regard to America’s efforts, his approach was not accepted initially. Earliest Soviet approaches, like America’s, tended toward the Direct Ascent scheme. Probably the same debate ongoing with American lunar planners existed in the Soviet Union.

The simplicity of a single vehicle based on a NOVA class booster led at the onset. Ultimately, perhaps, as Soviets studied America’s choice of LOR, and its LEM offspring, an approach similar to America’s was pursued. Nevertheless, the ultimate Soviet booster N-1 was much more powerful than the Saturn V. (10,000,000 pounds of first stage thrust versus approximately, 7,500,000.)

I was altogether astounded to discover the evolution of the Soviet approach when sketches, and even videos, were released with the collapse of the Soviet Union and its posture of manned space secrecy. But, I still contend, that the early focused efforts by NASA championed by Dr. Houbolt on the LOR lunar architecture won out over, I believe, tardy acceptance by the same in the Soviet Union. One of the finest compliments one receives is the adoption of a competitor’s approach. Simply comparing BURAN to the Space Shuttle tends to make this case as well.

Check back tomorrow for more answers from NASA engineer Jerry Woodfill.

13 Things That Saved Apollo 13, Part 13: The Mission Operations Team

The phrase “last but not least” was likely never more appropriate. Though this is the last article of our “13 Things That Saved Apollo 13” series, it might be the most important. “Each time I’ve heard Jim Lovell or Fred Haise speak of the rescue,” said NASA engineer Jerry Woodfill, “they have always expressed their gratitude to the folks on the ground who contributed to saving their lives.”

And it wasn’t just the astronauts who were grateful. As a testament to the appreciation the rest of the country felt, the Mission Operations Team for Apollo 13 — those who worked in the Mission Operation Control Room (MOCR – more commonly called Mission Control) and the Mission Evaluation Room (MER) — were awarded a Presidential Medal of Freedom.

“We fulfilled the latter part of President Kennedy’s mandate,” said Woodfill, “by returning them safely to Earth.”

The Presidential Medal of Freedom awarded to the Mission Operations Team of Apollo 13. Image courtesy Jerry Woodfill.

In previous articles in this series, we’ve highlighted just a few people who made significant – and some unsung – contributions to the Apollo 13 rescue. But likely every person who was part of the mission operations team made a contribution.

The words of President Richard Nixon as he presented the medal on April 18, 1970, perhaps say it best:

“We often speak of scientific ‘miracles’ – forgetting that these are not miraculous happenings at all, but rather the product of hard work, long hours and disciplined intelligence.

The men and Women of the Apollo XIII mission operations team performed such a miracle, transforming potential tragedy into one of the most dramatic rescues of all time. Years of intense preparation made this rescue possible. The skill coordination and performance under pressure of the mission operations team made it happen. Three brave astronauts are alive and on Earth because of their dedication and because at the critical moments the people of that team were wise enough and self-possessed enough to make the right decisions. Their extraordinary feat is a tribute to man’s ingenuity, to his resourcefulness and to his courage.”

Certificate given to Woodfill for the Congressional Medal of Freedom. Image courtesy Jerry Woodfill.

But, says Woodfill, it wasn’t just those whose names are listed on the initial award.

“There were a thousand more who never were named though their contribution was huge. I could write another hundred accounts of specific acts which, had they not been done, could have resulted in disaster. There was an unseen “cloud of helpers” whom I now know helped just as much as I did though they were never recognized. These folks weren’t even NASA employees or affiliated with the supporting contractors, Grumman (GAEC) or North American Aviation (NAA). Universe Today could go on for months, on a daily basis if I could add all these accounts. Studying something for 40 years brings forth this kind of thing.”

Employees at Johnson Space Center witnessing the President presenting the Presidential Medal of Freedom to the Apollo 13 Mission Operations Team (April 1970). Image courtesy Jerry Woodfill.

But since Apollo 13 happened 40 years ago, many of those involved are no longer alive. Woodfill said astronaut Jack Swigert is an example. A 40th anniversary celebration of the Apollo 13 mission at Johnson Space Center in April included a panel discussion with Jim Lovell, Fred Haise, Gene Kranz, Glenn Lunney, John Aaron, and was moderated by Jeffrey Kluger, co-author with Lovell of the book Lost Moon.

Read Woodfill’s account of the celebration on his website.

40th anniversary celebration of Apollo 13 at Johnson Space Center. Image courtesy Jerry Woodfill.

“During that two hour exchange, I added a half dozen more insights of unique things that saved Apollo 13,” said Woodfill. “But when the Q&A launched, I all but ran to the microphone to ask the first question: ‘Jim and Fred, could you comment on Jack Swigert’s contribution?’ Their remarks were gracious and appreciative, remembering their friend and crewmate. Neither they nor the country has forgotten Jack. He is the only astronaut to be honored by a statue in Congress, as he became an elected representative in Congress from the State of Colorado. Sadly, cancer took Jack’s life before he could serve. But I think if Jack could speak to us about his experience on Apollo 13, he might select the Mission Operations Team as well. In a sense, he represents all those no longer with us. They helped make it possible for Jim and Fred to have blessed us for the past 40 years with the altogether inspirational story of the rescue of Apollo 13.”

A plaque from the three Apollo 13 astronauts thanking the mission support teams. Note the panels of the caution and warning system above the signatures. 'That was my system,' said Woodfill. 'The alarm system personified what the team’s role was providing caution, warning, and assistance for the crew’s safety.' Image Courtesy Jerry Woodfill

So, while we have only scratched the surface among the many stories of Apollo 13’s rescue, surely there are thousands more tales of people being in the right place at the right time, decisions made years earlier that led to working at NASA, and chance meetings or discussions that opened up opportunities or jogged ideas for the rescue.

Jerry Woodfill and Fred Haise at the 40th anniversary celebration of Apollo 13 at JSC. Image courtesy Jerry Woodfill.

Jerry Woodfill is an example of such a story. He was attending Rice University on a basketball scholarship, a dream that inexplicably came true.

“However, my career as a college basketball player was as dismal as America’s early endeavors in space,” Woodfill admitted. “Sadly, I hold the record of the lowest shooting percentage in Rice University history…one out of eighteen shots! And the one shot I made at Baylor University with seconds left in the first half was a desperate 35 foot pass to our center under the basket. It sailed too high and went through the hoop. My only basket was actually a bad pass! In truth, I was zero for eighteen.”

He wasn’t doing very well in his classes, either. But then President John Kennedy came to Rice University to give a speech, a speech which helped launch the US to the Moon:

“But why, some say, the moon? Why choose this as our goal? And they may well ask why climb the highest mountain? Why, 35 years ago, fly the Atlantic? Why does Rice play Texas? We choose to go to the moon in this decade and do the other things, not because they are easy, but because they are hard, because that goal will serve to organize and measure the best of our energies and skills, because that challenge is one that we are unwilling to postpone, and one which we intend to win, and the others, too.”
John F. Kennedy, in his speech at Rice University, September 12, 1962

Inspired by Kennedy’s speech, Woodfill turned in his basketball shoes and focused on his studies of electrical engineering, hoping to become part of the space program to send people to the Moon – and return them safely to the Earth.

Yes, Woodfill become one of the half million Americans teaming up together to put the first men on the Moon.

And the rest is history.

Our extreme thanks to Jerry Woodfill for sharing his story, insights, and expertise as well as his warmth, humor and passion for NASA’s mission. “Godspeed to all you Apollo 13 rescuers, past and present, known and unknown!”

The “13 Things That Saved Apollo 13” series:

Introduction

Part 1: Timing

Part 2: The Hatch That Wouldn’t Close

Part 3: Charlie Duke’s Measles

Part 4: Using the LM for Propulsion

Part 5: Unexplained Shutdown of the Saturn V Center Engine

Part 6: Navigating by Earth’s Terminator

Part 7: The Apollo 1 Fire

Part 8: The Command Module Wasn’t Severed

Part 9: Position of the Tanks

Part 10: Duct Tape

Part 11: A Hollywood Movie

Part 12: Lunar Orbit Rendezvous

Part 13: The Mission Operations Team

Also:

Your Questions about Apollo 13 Answered by Jerry Woodfill (Part 1)

More Reader Questions about Apollo 13 Answered by Jerry Woodfill (part 2)

Final Round of Apollo 13 Questions Answered by Jerry Woodfill (part 3)

Never Before Published Images of Apollo 13’s Recovery

Listen to an interview of Jerry Woodfill on the 365 Days of Astronomy podcast.

13 Things That Saved Apollo 13, Part 12: Lunar Orbit Rendezvous

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Note: To celebrate the 40th anniversary of the Apollo 13 mission, for 13 days, Universe Today will feature “13 Things That Saved Apollo 13,” discussing different turning points of the mission with NASA engineer Jerry Woodfill.

Going to the Moon was big. It was a giant stride in doing what had once been thought impossible. Initially many scientists and engineers had big plans for huge rockets akin to the ships imagined in science fiction: one piece vehicles that took off from Earth, landed intact bottom down on the Moon and had the ability to launch again from the lunar surface. But other rocket engineers had different ideas, and this caused some big arguments. The method of going to the Moon that eventually won out used — in part — a little lunar lander. This decision ended up being instrumental in saving the crew of Apollo 13. And that was big.

The three different Apollo flight modes. Credit: NASA

There were three different methods to choose from in reaching the Moon. One, called the Direct Ascent Mode, would have used the big Flash Gordon-like enormous rocket – which was known as a Nova class rocket –to fly straight to the Moon, land and return. Second, the Earth Orbital Rendezvous technique called for two not-quite-as big Saturn V boosters to launch and rendezvous in Earth orbit. In this mode, one rocket would carry a single Apollo vehicle and its crew, and the other, more fuel, which would be transferred to Apollo in Earth orbit, and then the spacecraft would head off to the Moon. The third option was Lunar Orbit Rendezvous which used only one three-stage Saturn V booster, and split the Apollo vehicle into two separate vehicles – a combined Command and Service Module (CSM), and a Lunar Module (LM).

Those familiar with NASA history know that Lunar Orbit Rendezvous was the final choice.

But this mode wasn’t an obvious choice, said NASA engineer Jerry Woodfill.

“At first, Werner Von Braun wanted to use the Nova class rocket Direct Ascent approach, and so did President Kennedy’s science advisor, ” Woodfill said. “But a group at Langley Research Center led by Dr. John Houbolt came up with the Lunar Orbit Rendezvous design. And most everyone ignored them at first.”

NASA engineer John C. Houbolt describes the Lunar Orbit Rendezvous concept at the chalkboard in July 1962. Image Credit: NASA

But Houbolt insisted the one-rocket system was not feasible. In a NASA interview Houbolt said, “It can not be done. I said you must include rendezvous in your thinking — to simplify, to manage your energy much better.”

Houbolt said it turned into a two-and-a-half year fight to convince people, but he and his team had the facts and figures to back up their claims.

Woodfill said one of his colleagues, former NASA engineer Bob Lacy was part of the discussions on which plan to use. “He said it was unbelievable,” Woodfill recalled. “They were debating in a meeting room at Langley about the best way to go to the Moon. One side was for sending a single vehicle requiring a huge booster to get it there. The other group wanted a two spaceship method. No one seemed agreeable to the other side’s approach. Tempers were starting to flare. To ease the situation someone said, ‘Let’s flip a coin to settle the score.’ Can you believe that?”

No one flipped a coin, but the story demonstrates the intensity of the debate.

In the race to get to the Moon, the Soviet Union had embraced the Nova rocket concept. “The Soviets pressed forward with the direct assent approach to use a Nova class booster,” said Woodfill. “Designated N-1, it clustered 30 engines on its first stage. The design achieved a Herculean thrust of 10-12 millions pounds. Additionally, this uncomplicated direct ascent launch would be less complex was thought to take less time to accomplish. Designing, building, testing and launching two separate spaceships might not win the race to the Moon.”

Woodfill said the Nova rocket may have proved to be the best choice except for the failure of just one of those 30 engines at launch. “This would unbalance the entire assemblage,” Woodfill said.

And twice in 1969 – one occurring just weeks before the scheduled launch of Apollo 11 — the Soviet N-1 booster exploded at liftoff. The huge rocket proved to be too complicated, while the Lunar Orbit Rendezvous method had a simple elegance that was also more economical.

A diagram of the lunar-orbit rendezvous used on Apollo by John Houbolt. Credit: NASA

In November 1961, Houbolt boldly wrote a letter to NASA associate administrator Robert C. Seamans, “Do we want to go to the Moon or not?” he wrote. “Why is Nova, with its ponderous size simply just accepted, and why is a much less grandiose scheme involving rendezvous ostracized or put on the defensive? I fully realize that contacting you in this manner is somewhat unorthodox,” Houbolt admitted, “but the issues at stake are crucial enough to us all that an unusual course is warranted.”

The bold move paid off, and Seamans saw to it that NASA took a closer look at Houbolt’s design, and surprisingly, it soon became the favored approach – after a little debate..

Houbolt’s design separated the spacecraft into two specialized vehicles. This allowed the spacecraft to take advantage of the Moon’s low gravity. The lunar lander could be made quite small and lightweight, reducing bulk, fuel, and thrust requirements.

The Lunar Module Aquarius, after it was jettisoned from the CSM. Farewell Aquarius, we thank you, the crew radioed. Credit: NASA

When the oxygen tank in Apollo 13’s Service Module exploded, the Lunar Module “Aquarius” played an unexpected role in saving the lives of the three astronauts, serving as a lifeboat to return the astronauts safely back to Earth. Additionally, its descent stage engine was used for propulsion, and its batteries supplied power for the trip home while recharging the Command Module’s batteries critical for re-entry. And with ingenuity of Mission Control the LM’s life support system – which was originally designed to support two astronauts for 45 hours, — was stretched to support three astronauts for 90 hours.

Imagine, Woodfill said, if Apollo 13 had been a single vehicle employing the Direct Ascent approach. “After the explosion and subsequent loss of the fuel cells, only those entry batteries would have been available to sustain life. Their life, even if all systems except life support, were turned off would be less than 24 hours. And Lovell, Swigert and Haise along with Apollo 13 would return to Earth on that “free-return-trajectory” being cremated in the fiery heat of reentry. But for the clever Lunar Orbit Rendezvous approach, Apollo 13 would have been a casket. Instead, its lunar lander became a wonderful lifeboat” Woodfill said.

Next: Part 13: Houston

Earlier articles from the “13 Things That Saved Apollo 13” series:

Introduction

Part 1: Timing

Part 2: The Hatch That Wouldn’t Close

Part 3: Charlie Duke’s Measles

Part 4: Using the LM for Propulsion

Part 5: Unexplained Shutdown of the Saturn V Center Engine

Part 6: Navigating by Earth’s Terminator

Part 7: The Apollo 1 Fire

Part 8: The Command Module Wasn’t Severed

Part 9: Position of the Tanks

Part 10: Duct Tape

Part 11: A Hollywood Movie

Part 12: Lunar Orbit Rendezvous

Part 13: The Mission Operations Team

Also:

Your Questions about Apollo 13 Answered by Jerry Woodfill (Part 1)

More Reader Questions about Apollo 13 Answered by Jerry Woodfill (part 2)

Final Round of Apollo 13 Questions Answered by Jerry Woodfill (part 3)

Never Before Published Images of Apollo 13’s Recovery

Listen to an interview of Jerry Woodfill on the 365 Days of Astronomy podcast.