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!