Jerry Woodfill, an engineer who worked diligently behind the scenes during NASA’s Apollo program, has passed away at age 79. Jerry was still employed by the Johnson Space Center (JSC) at the time of his death, working there for over 57 years. Most notably, Jerry worked as the lead engineer behind the Caution and Warning System on the Apollo spacecraft, which alerted astronauts to issues such as Apollo 11’s computer problems during the first Moon landing, and the explosion of Apollo 13’s oxygen tanks.
While continuing his work as an engineer at JSC, Jerry’s infectious enthusiasm for spaceflight led him to also be part of NASA’s public and educational outreach, where he spearheaded programs for children, teachers and adults about science and space flight. He routinely gave over 40 lectures a year, both in person and online to listeners around the world. His unique sense of humor and sometimes unabashed showmanship could hold even the shortest of young attention spans. Jerry usually had his audiences either in stitches or fully captivated by his stories.
NASA engineer Jerry Woodfill at a presentation to students. Image courtesy Jerry Woodfill.
To celebrate the 45th anniversary of the Apollo 13 mission, Universe Today has been featuring “13 MORE Things That Saved Apollo 13,” discussing different turning points of the mission with NASA engineer Jerry Woodfill. Today, we let Jerry have the final word as he talks about a different aspect of the Apollo 13 mission.
Written By Jerry Woodfill:
I hesitated to include this among the “Things That Saved Apollo 13” because it is sort of intangible, i.e., not related to actual hardware, software, mission operations, and all things STEM. Nevertheless, in my mind, it is, perhaps, most responsible for the ultimate success of the rescue. I think it might override all the original “13 Things” as well as the “13 More Things that saved Apollo 13.”
Adding it came to me on New Year’s Eve of 2014. For a number of years, Apollo Flight Director Gene Kranz has presented a wonderful motivational program entitled and based on this concept, this motto, this creed — that failure is not an option. Five years ago, I borrowed the title for annual programs presented to high school and college students visiting the Johnson Space Center, such as in the picture above and below.
Jerry Woodfill speaking to students. Image via the NASA National Community College Aerospace Scholars Website.
Universe Today writer Nancy Atkinson discussed in part 11 the origin of the saying “Failure is Not an Option,” which actually came from one of the “Trench” team members, Jerry Bostick.
Of course, there are those who consider the phrase “pie in the sky,” altogether “over-the-top” and “Pollyanna.” They assert that such is unrealistic when faced with obviously insurmountable challenges. For me, the best argument to counter that view came years ago from comments I’ve found on the internet. Below are a couple of paraphrased examples:
“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. 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 imagined I would have to do.”
In like fashion, the heroism of Jim Lovell, Fred Haise, and Jack Swigert along with the resolve, perseverance, and herculean efforts of all involved would always be revered. “Failure Is Not an Option” is not naïve whatsoever. It is a guiding principle for whatever challenge we face.
I’ve also received emails, like the one below from people who have come across my off-the-job internet site:
Dear Mr. Woodfill:
I just watched the movie Apollo 13 and started researching the quote “failure is not an option”. In doing so I came across an article you had written, and I wanted to thank you for it.
I appreciated everything you wrote, but I was especially touched by the following: “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.”
Finding your article was such a blessing because today they just told me my father would have to go on hospice, and I have been praying to God for strength and peace for my father and for myself. After all, what could I possibly say or do that could help him? But after I read this I knew. I just have to love him. So thank you for that.
You wrote the article many years ago, and I know chances are small that you will ever receive this email. But I just wanted you to know how much peace I received from what you had written. Because, as you said, no matter how bad things get, if I just love him, I can’t fail.
Bless you for reminding me of that.
Sandra
+ + + + +
Finally, Nancy asked me to explain how the phrase “Failure Is Not an Option” affected me. So how did that tagline affect me? Experiencing the “13 Things” and “the 13 More Things, at first in real time, and later in 100s of hours of reflection wholly changed the course of my life. I simply could not ignore the overwhelming evidence of so many things that saved Apollo 13 being fortuitous. In both series, I’ve done my best to “de-spiritualize” the accounts, knowing this series is a secular assessment. Actually, the genesis of every one of the now “26 things,” for me, was altogether providence or answered prayer. How this ensued is recorded on my off-the-job website if you are interested, as Paul Harvey used to say, in “the rest of the story.”
But I wanted to reach out to a much broader audience by sharing a factual secular account. I’m grateful to Nancy and “Universe Today” for making that possible.
In an off-hand way, many who have followed the series may have concluded what I discovered – that a person or power above had intervened as another of “the things that saved Apollo 13.” So I am always encouraged by the tagline “failure is not an option.” Now, it is, for me, another way of saying what I discovered through Apollo 13’s rescue that “all things work together for good,” as the above email says.
Thank you!
Sincerely,
Jerry Woodfill
Jerry Woodfill with students from the Community College Aerospace Scholars, with the ‘Failure Is Not an Option’ pledge in the background. Image courtesy Jerry Woodfill.
Apollo astronaut photo of a SNAP-27 RTG on the Moon. Credit: NASA.
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.
For our final installment of this series of “13 More Things That Saved Apollo 13,” we’ll look at an event that has not been widely addressed, but it may have been one of the most crucial scenarios which might have ended in disaster and death for the crew in the final minutes of the rescue.
It starts with an atomic electrical power generator called SNAP-27.
These devises enabled the Apollo Lunar Surface Experiment Package (ALSEP) to operate on the Moon for years after astronauts returned to Earth. They were deployed on Apollo 12, 14, 15, 16 and 17 and included seismometers, and devices to detect lunar dust and charged particles in the lunar environment.
SNAP stands for Systems Nuclear Auxiliary Power and its fuel was plutonium-238 (Pu-238). It was a type of Radioisotope Thermoelectric Generator (RTG) that provides electrical power for spacecraft by converting the heat generated by the decay of plutonium-238 fuel into electricity. Approximately 8 lbs of plutonium was used for each mission and it was it was transported to the Moon in a thermally insulated cask attached to the side of the Lunar Module.
“The cask was so strong and impervious that firing the container with a cannon into a solid brick wall would not break it,” said NASA engineer Jerry Woodfill.
Unfortunately, Woodfill added, as the political climate for anything atomic has grown acrimonious, the application of atomic energy to space exploration has been thwarted.
“Despite a remarkable atomic safety record, a small but powerful political coalition has successfully opposed such harmless devices as NASA’s Apollo SNAP-27 generator,” said Woodfill. “The scare-factor attributed to NASA’s Apollo atomic power generator was based on the threat of a launch pad explosion or exaggerated claims that an accident would contaminate Earth’s atmosphere and ultimately bring death to many. It is amazing that such groups can ignore obvious day-to-day deaths in automobiles yet alarm the public with false atomic threats.”
Apollo 13 Commander Jim Lovell carrying a plutonium battery and scientific equipment during training. Credit: NASA.
Woodfill said that the opposition to RTGs has been most unfortunate for the sake of human and robotic exploration of the solar system.
“The limitation of traditional rocket fuels handicaps improvement in propulsion,” he said, “and for the past five decades, little progress has been made in rocket engine specific impulse improvement known as the ISP.”
Additionally, for several years NASA has been facing a shortage of RTGs for powering robotic spacecraft limiting the scope and lifetime of missions going to the far reaches of our Solar System.
For Apollo 13, the SNAP-27 device should have ended up staying on the Moon, but of course, the lander did not land so it, along with the atomic generator, was going to reenter Earth’s atmosphere and end up somewhere on our planet.
It wasn’t long after the accident on Apollo 13 that NASA was contacted by the Atomic Energy Commission (AEC) about where the LM would be reentering and burning up in Earth’s atmosphere.
However, as Apollo 13 approached Earth, their flight path kept deteriorating, despite the crew’s efforts. As we discussed in Part 9 of this series about the potentially fatal gimbal lock, without the Command Modules thrusters and computer navigation system to steer, only the lander’s were available, and manually flying the crippled Apollo 13 spacecraft stack and keeping it on the right trajectory was a huge challenge.
Woodfill said that any ‘tinkering’ with the reentry geometry was altogether ill-advised considering how very ‘iffy” the angle and entry path had become, but AEC officials were pressuring the retro officers about the orientation required for the LM’s reentry to put it into a deep trench in the Pacific Ocean.
Woodfill said that from his perspective of decades of study about the mission, the need to “deep-six” the SNAP-27 generator was almost responsible for having the Apollo 13 rescue end in tragedy. There was confusion among those in Mission Control as well as the crew about the orientation the spacecraft at reentry. However, Woodfill said, an inadvertent ‘mistake’ by Lovell may have actually saved the crew.
“There was a significant debate between the two most knowledgeable retro officers about jettisoning of the lunar lander,” he said. “So uncertain was the scenario of positioning the command ship for LM jettison that the men held exactly opposite views of the result of selecting the position wanted by the AEC scientists. Added to the peril was Lovell’s brush with ‘running the ship aground’, i.e., into gimbal-lock trying to please the AEC.”
A 2009 research paper for AIAA adds insight into the danger of these moments prior to LM jettison and Lovell’s error. “Attempts to perform rapid analysis in a high pressure, time critical spacecraft emergency can lead to errors in analysis and faulty conclusions,” the paper reads. “For example, the spacecraft was maneuvered to the wrong LM/CM separation attitude, ~45 degrees on the north side of the CM ground track rather than the desired 45 degrees on the south side of the CM ground track. This attitude was close to CM IMU gimbal lock and complicated manual piloting.”
Mission transcripts reveal the confusion and the difficulty the crew faced. As Lovell was trying to maneuver the stack into the correct orientation for LM jettison he radioed:
Lovell: We’re having trouble maneuvering, Joe, without getting it in gimbal lock… You picked a lousy attitude, though, to separate.
Capcom: Well, we apologize. Just take your time. Jim, we’ve got time now.
Lovell continued to struggle as the ship continually approached gimbal lock and he questioned the procedure:
Lovell: Houston, why can’t I stay in PGNS ATT HOLD for the LM attitude hold?
Capcom: Stand by on that, Jim.
Lovell: I want to get way over here, Joe, to prevent going into gimbal lock. I have the yaw at about – I’d say about almost 50 degrees.
Capcom: Roger that. Just stay out of gimbal lock and that 45-degree isn’t critical – the out of plane, that is.
Nonetheless, an Apollo 13 post-mission report reveals that shortly before LM jettison the Retro Officer Chuck Deiterich advised the Flight Director that the LM was not in the correct orientation for separation. “The telemetry indicated that we were yawed 45 degrees North instead of 45 degree South,” the report says, so the ship was 90 degrees out of yaw attitude prior to LM jettison.
However, the LM closeout was underway, and there was no chance to use the thrusters to change attitude. The report continues, “No correction action was taken, because the separation was a minimum of 4,000 feet at entry interface, and more likely was going to be 8000 feet or greater. Therefore, no attempt was made to change the attitude.”
“Because the LM’s guidance computer was maintaining the jettison attitude, the crew could no longer steer the assemblage until the LM release,” explained Woodfill. “And then a terribly threatening event arose. In order to preserve the desired attitude to assure that the SNAP-27 plutonium landed in the ocean, the LM’s computer was moving the command ship’s platform into gimbal lock. It was too late to re-enter the LM. The time to unlatch the hatches would be too great.”
But despite the likely loss of control, somehow the LM was jettisoned just prior to the Command Module reaching gimbal lock.
“Had not, it was later discovered, Jim Lovell actually have mistakenly placed the attitude 90 degrees from the desired jettison position, a potentially fatal gimbal lock would have happened,” Woodfill said. “It was as though despite the disagreement between the retro experts and the resulting confusion between Mission Control and the crew, and then Lovell’s error, neither of the miscues of the entire scenario resulted in the dreaded gimbal-lock. Plus, the SNAP-27 ended up in an optimum location in the Pacific Ocean. Indeed, two mistakes made a right. The entry capsule’s guidance platform became stable and ready for reentry.”
However, Deiterich told Universe Today that with respect to the LM jett attitude, the landing point was not greatly affected by north or south. But to assure maximum separation during entry, the southerly direction was actually opposite the northerly direction the crew would fly.
“When I realized they were closing out, I told Kranz we would buy the current attitude,” Deiterich said via email. “The inplane separation velocity was enough to assure reasonable down range separation. We were just being thorough. Knowing is why we accepted the jettison attitude. I remembered the A10 Ascent stage jett and how the pressure between the CM and ASC pushed the ASC away so I picked this as a way to jett the LM on A13.”
Both during the mission and the crew debriefing the puzzling topic of that SNAP-27 disposal caused confusion. Days later during the debriefing, the crew seemed at a loss to understand what was going on with regard to ground control’s insistence on assuming such a particular jettison orientation for the lunar module. Somehow, they didn’t seem aware of the issues with the SNAP-27 atomic generator, an issue that likely would not threaten Earth but in every way threaten the lives of Lovell, Swigert and Haise.
“We were very close to gimbal lock,” Lovell said in the mission debrief. “I questioned whether the LM SEP attitude was that critical. Was it so critical to be at that attitude, or would it have been better to stay away from gimbal lock in the CM?”
Lovell was worried that they didn’t have any backup help of navigating — the Body Mounted Attitude Gyros, or BMAGs. “We didn’t have the BMAGs powered up,” Lovell said in the debrief. “If we had gone into gimbal lock, we would have had to start from scratch again.”
Deiterich agreed, especially since the crew was pressed for time as time for reentry was rapidly approaching. “Maneuvering the LM with the CSM attached was not easy,” Deitrich said via email, “thus Jim tried to keep any maneuvering out of plane to a minimum, once there he was reluctant to move away and also the whole process was brand new and time could then become a factor.”
The crew of Apollo 13 after they splashed down safely. Credit: NASA
Woodfill said the entire team in Mission Control helped save the crew – the EECOM (Emergency, Environmental, and Consumables Management) and the lander’s TELMU (Telemetry, Electrical, EVA Mobility Unit Officer) dealing with the spacecraft environmental and power systems, and the ‘Trench’ team of the FIDO flight dynamics officer who was responsible for the trajectory, the GUIDO guidance and navigation officer who was charged with assessing the crafts’ ability to steer itself under astronaut control, and finally, the RETRO whose responsibility was entering Earth’s atmosphere via retro-rocket firing.
“Considering Apollo 13’s myriad of challenges, it would be a toss-up between the groups if a vote were taken akin to voting for the outstanding “player” in a Monday Night Football game,” he said. “But there is no doubt with regard to the final minutes of the contest who would win the vote. It would be the latter group dealing with guidance and reentry. This is especially so considering the number of times the group thwarted loss of guidance. Without them, Apollo 13 would have lost the game to the formidable adversary gimbal-lock.”
And what happened to Apollo 13’s SNAP-27? In the book “Thirteen: The Flight that Failed”, Henry S.F. Cooper said that the plutonium apparently survived reentry and landed in the Tonga Trench south of Fiji in the Pacific Ocean, approximately 6-9 kilometers underwater. It exact location is unknown but monitoring of the areas has shown that no radiation escaped.
Apollo 13 images via NASA. Montage by Judy Schmidt.
A look at the Mission Operations Control Center (MOCR) or Mission Control during the Apollo era. In this image, 2 is the Retrofire officer, 3 is the Flight Dynamics Officer and 4 is the Guidance Officer. Credit: NASA.
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.
In the original Mission Operations Control Room (MOCR) at the Manned Spacecraft Center in Houston, a group of NASA flight controllers sat in the front row of the consoles, aligned nearest to the enormous front wall displays of the MOCR, or Mission Control. They sat in a ‘trench-like’ lower level with respect to the remaining flight controllers and this group came to be known as “The Trench.”
“The teamwork of the Apollo 13 band of Trench ‘brothers’ coordinating navigational challenges in a fashion that was never accomplished before or after in the annals of lunar flight was certainly one of the additional things that saved Apollo 13,” said NASA engineer Jerry Woodfill. “Failure to reach a consensus quickly in performance of the restoration of free return trajectory, the PC+2 and other crucial ‘burns’ would have been detrimental to rescue.”
Overall view showing some of the activity in the Mission Operations Control Room during the final 24 hours of the Apollo 13 mission. From left to right are Shift 4 Flight Director Glynn Lunney, Shift 2 Flight Director Gerald Griffin, Astronaut and Apollo Spacecraft Program Manager James McDivitt, Director of Flight Crew Operations Deke Slayton and Shift 1 Flight Surgeon Dr. Willard Hawkins. Credit: NASA.
Woodfill said that like the Parachute Infantry Regiment described in Stephen E. Ambrose’s popular book and subsequent mini-series “Band of Brothers” – which told of the teamwork and perils of combat during World War II — the men of The Trench served like a platoon of soldiers defending 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 Jerry 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.
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.
The air to ground transcript from the time of the explosion on Apollo 13 demonstrates the confusion of what was happening:
Jim Lovell: Houston, we’ve had a problem. We’ve had a MAIN B BUS undervolt.
Capcom: Roger. MAIN B undervolt. Okay, stand by, 13. We’re looking at it.
Fred Haise: Okay. Right now, Houston, the voltage is – is looking good. And we had a pretty large bang associated with the Caution and Warning there.
Lovell then started to name all the Caution and Warning lights that were illuminating, including the Guidance and Navigation light, a computer restart, and indicators that there might be a problem with the oxygen and helium tanks.
The Apollo spacecraft Caution and Warning System had one intended function: alert the astronauts and Mission Control to a potential system failure. Plainly put, the Caution and Warning System allowed the spacecraft to tell the story of what was going wrong.
Location of Caution And Warning System lights in the Command Module. Credit: Project Apollo.
In all our discussions so far with NASA engineer Jerry Woodfill, we’re finally letting him talk about the system he was responsible for: the Caution and Warning System (C&WS).
Jerry Woodfill working in the Apollo Mission Evaluation Room. Credit: Jerry Woodfill.Woodfill’s role in the Apollo program was unique in the sense that he held the position and responsibility of Apollo Spacecraft Warning System Engineer. He was responsible for fixing, redesigning, and analyzing warning system performance during testing and early flights. During Apollo 11 and Apollo 13 he was responsible for monitoring the C&WS at his station adjacent to Apollo Mission Control in the engineering Mission Evaluation Room.
Of the image above of the plaque from the Apollo 13 astronauts thanking the mission support teams, Woodfill said, “That was my system. The alarm system personified what the team’s role was providing caution, warning, and assistance for the crew’s safety.”
From an official NASA report on the Apollo spacecraft systems:
“Critical conditions of most spacecraft systems are monitored by a caution and warning system. A malfunction or out-of-tolerance condition results in illumination of a status light that identifies the abnormality. It also activates the master alarm circuit, which illuminates two master alarm lights on the MDS and one in the lower equipment bay and sends an alarm tone to the astronauts’ headsets. The master alarm light and tone continue until a crewman resets the master alarm circuit. This can be done before the crewmen deal with the problem indicated. The caution and warning system also contains equipment to sense its own malfunctions.”
One of Woodfill’s responsibilities was to enter into the Apollo 13 Crew’s Operational Checklist when ”nuisance alarms” might be expected as a result of momentary switching modes. But mainly, he was responsible for setting the thresholds for when the alarms would be activated. The myriad of alarms sounding for Apollo 13 made it obvious that something serious was happening.
“The first alert that Apollo 13 was direly threatened came from the Caution and Warning system’s Master Alarm issued as a result of a Main Bus B under-voltage,” explained Woodfill. “It was because the warning system’s threshold for low voltage was established that the crew and mission control had an instant awareness of the dire situation. This saved valuable time in analyzing the source of Apollo 13’s malfunction.”
Likewise, as we discussed in Part 5 of this series, it was the setting of the threshold of the CO2 caution light ringing a Master Alarm which alerted the crew to the need for changing out the lithium hydroxide canisters to filter out the danger carbon dioxide that was accumulating in the Lunar Module.
“The component caution CO2 light’s illumination, while backed-up by a gauge, nevertheless, made the need for a solution all the more apparent,” said Woodfill.
And, of course, when the Oxygen Tank 2 Quantity sensor failed, a Master Alarm sounded from the Caution and Warning System as an alert, along with the quantity gauge reading, that trouble shooting should be undertaken.
Woodfill noted that because multiple inputs from the tanks were “OR-gated” (electronic logic system disjunction) into the alarm system, the actual explosion of Oxygen Tank 2 did not set off the Master Alarm, via the oxygen tank inputs to the C&WS, but rather the resulting secondary sensing by the C&WS of the Main Bus B undervolt input which did. But he does believe the failure of the Tank 2 sensor did earlier set off the Master Alarm to initiate the trouble shooting, not being masked by “OR-gating” of other items.
Apollo 1 astronauts (from left) Virgil “Gus” Grissom, Edward White and Roger Chaffee stand near Cape Kennedy’s Launch Pad 34 during training. Credit: NASA
In our original series of “13 Things That Saved Apollo 13” Woodfill explained how the Apollo 1 fire – as tragic as it was – contributed to the success of future Apollo flights and the saving of Apollo 13 by the design improvements in spacecraft components and systems.
“This resulted in the much improved, safer, more reliable Apollo Command Module,” said Woodfill.
Woodfill said the C&WS additionally helped — both before and after the fire — to reveal what in the manufacture of the poorly made initial Block One ill-fated Spacecraft 012 that contributed to the fire which cost the lives of the Apollo 1 crew in January of 1967.
“The Caution and Warning System revealed a myriad of glitches, flaws, discrepancy reports, squawks, oversights and shortcomings,” Woodfill said. “Yet, the warning system, in doing its job, led to design improvements in the next series of Apollo craft which included Apollo 13. Though compromised by a damaged O2 tank, Apollo 13 had numerous features added as a result of the terrible Spacecraft 012 fire.”
Woodfill’s part in improving the system was key. Both the Command and Lunar Module’s C&WS were improved following the fire, and were thoroughly reviewed to assure all systems were safely upgraded to avoid the kind of failure which killed the Apollo 1 crew. These improvements in the Lunar Module’s C&WS are listed in the Apollo Experience Report Woodfill co-authored as the Warning System Engineer, which can be read here.
“Had not the Caution and Warning System helped alert NASA and the contractor team to how badly the original command ships were made, likely Apollo 13 would have not survived the oxygen tank explosion,” said Woodfill.
Apollo 13 images via NASA. Montage by Judy Schmidt.
Apollo 13 images via NASA. Montage by Judy Schmidt.
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.
The night of the explosion on Apollo 13, engineers working in Mission Control and the back-up Mission Evaluation Room (MER) assessed the situation. There were numerous failures in different systems, and finally, instead of just looking at the failures, the engineers had to determine what was actually working on the spacecraft in order to rescue the crew.
A relatively recent term called ‘macgyvering’ was definitely at work during the Apollo 13 mission. Named for the lead character in the television series MacGyver – who usually used duct tape, a Swiss Army knife and anything else he could find to get himself out of sticky or dangerous situations -– macgyvering means solving complex problems by taking something ordinary and using it in an unusual way, but it works perfectly.
The engineers working during the Apollo 13 mission may have been the original “MacGyvers.”
According to NASA engineer Jerry Woodfill, his definition of a good engineer is “one who can take the simplest tool to accomplish the most complex task in the easiest way,” and its corollary, “The greatest engineer is one whose solution is so simple that no one sees his contribution as noteworthy.”
Some of the solutions for Apollo 13’s problems were ingenious. Others were simple, but definitely contributed to the crew’s rescue.
Here’s a look at a few ‘everyday’ items that either the crew were really glad to have on board during the rescue or items that were “macgyvered’ to solve a problem:
The Apollo 13 Lunar Module ‘Aquarius’ as seen by the crew after the module was jettisoned prior to reentry into Earth’s atmosphere. Credit: NASA.
1. “Jumper cables”
Do you carry a set of jumper cables in your car? Apollo spacecraft didn’t actually have any jump-starting equipment, but a set of heater cables in the Lunar Module were macguyvered to perform as jumper cables.
There were 3 batteries in the Command Module to provide power for reentry, but after the explosion, they had been tapped for a short time to provide power when the fuel cells in the CM shut down. NASA engineers and flight controllers started looking at ways to try and recharge the batteries and came up with using heater cables from the LM in the reverse direction to charge the batteries for the reentry. It was never in the original design to charge the CM batteries from the LM, but the idea was to trickle-charge power from the large lander batteries to the modest capacity entry batteries.
A copy of the invoice sent by Grumman Management to North American Rockwell for charges associated with the Grumman LEM towing Rockwell’s CSM back to Earth. Via SpaceRef.
Two of three batteries were near full 40-amp-hour strength, but the third only had about half that amount. On a normal reentry, they would require 70 to 80 amp hours, but no one wanted to cut it that close on a mission that had so much going against it. So Mission Control told the crew to hook up a cable to the power system of the LM and recharge the weak battery. The process took about 15 hours and drew about 8 amps from the LM.
Famously, the company that built the LM, Grumman Aerospace, sent a mock invoice to the maker of the CM, following the successful return of Apollo 13 for LM’s “towing” service and included was a $5 charge for using the LM for “battery charge.”
An image of the OMEGA Speedmaster Professional watch worn in space. Image via OMEGA.
2. Watches
NASA supplied each of the Apollo astronauts with a standard issue OMEGA Speedmaster Professional manual-wind wristwatch. The astronauts were expected to wear them during the entire mission, and in fact, the watches were certified to be worn on all extra vehicular activities including the moonwalks. The version the crew used had a long Velcro strap, and with the adjustable strap, the watch could be worn on the outside of the pressure suits.
But more importantly – for Apollo 13 anyway – the watch included a chronograph or stopwatch, using the large third hand on the watch dial. This watch was used to time the manual engine burns to keep Apollo 13 on course and get them safely back to Earth.
However, this wasn’t the first time an Apollo mission used this type of watch in an ‘emergency.’ Buzz Aldrin wrote in his autobiography that an in-cabin timer in the LM had quit working and so during the moonwalk, Neil Armstrong left his Speedmaster inside and it served as a backup timer.
Since the Apollo 13 astronauts used their OMEGA Speedmaster Professionals to time a 14-second mid-course correction, when the company put out a commemorative version of the watch for this 45th anniversary, a small inscription is included on the dial between zero and 14 seconds that asks, “What could you do in 14 seconds?”
In April 1970, the OMEGA Speedmaster was given the “Silver Snoopy Award” from the astronauts for contributing to the rescue of Apollo 13 mission. Fred Haise’s Speedmaster is currently on display at the Penn-Harris-Madison Planetarium in Mishawaka, Indiana.
The Model FA-5 Penlight made by ACR Electronics that was used during the Apollo missions. Image via Space Flown Artifacts.
3. Flashlights.
When all the systems were shut down in the CM, the interior became dark and cold. Likewise, most sytems were shut down in the LM as well to save battery power. The crew used flashlights to make their way in the dark and cold cabins.
According to Space Flown Artifacts, NASA used the ACR Model FA-5 Penlight pictured above, a distinctive brass flashlight that were used from Apollo 7 to the early space shuttle missions. The same website quoted a letter dated Apr 19, 1971 from the Apollo 13 crew to ACR Electronics:
“The penlight which you have supplied for the Apollo missions has been very useful and dependable in all missions to date. However, you deserve special praise for the role it played on our mission – Apollo 13.
As you know, due to the explosion, we were forced to ration our electrical power and water. With regard to the former, we never turned on the lights in the spacecraft after the accident. As a result your penlights served as our means of “seeing” to do the job during the many hours of darkness when the sunlight was not coming through the windows. We never wore out even one set during the trip; in fact, they still illuminate today. Their size was also a convenience as it was handy to grip the light between clinched teeth to copy the lengthy procedures that were voiced up from Earth.”
A graphic showing the markings on the windows of the Apollo Lunar Module, which shows T the azimuth and elevation variations of possible viewing limits by the LM pilot. From the NASA report, ‘Apollo Lunar Module Landing Strategy.’
4. Window markings on the LM.
The special markings on the LM windows enabled Jim Lovell to hold course by aligning them with the Earth’s terminator. This was crucial to preventing too shallow an entry angle resulting in missing the entry point. According to a NASA report called “Apollo Lunar Module Landing Strategy,” the markings were part of the guidance system, and coupled with the computer system, made it possible for the pilot to “observe the intended landing area by aligning his line-of-sight with the grid marking according to information displayed from the guidance system.”
And so the crew used these markings in a way that wasn’t originally intended, but it made a big impact on the ability of the crew to navigate and fly the ship “by hand.”
John Young’s Apollo 16 flown Garland mechanical pencil. Via Space Flown Artifacts.
5. Pencils and pens.
Unlike the space shuttle and space station, there were no printers on board the Apollo spacecraft to print out daily planning reports and updates to the flight plan. The Apollo crews had to do things the ‘old fashioned way’ and used special mechanical pencils and pens that were flight certified to record modified checklist procedures called up to Apollo 13 by Mission Control — as the crew said above, they needed writing instruments to “copy the lengthy procedures that were voiced up from Earth.”
“Without them, crucial onboard operations could not have been performed,” said Woodfill
Again, according to Space Flown Artifacts, for most Apollo missions, the stowage lists show that each astronaut carried a Garland mechanical pencil, and despite the worldwide fame of the Fisher Space Pen it is probably the Garland mechanical pencil that was the most heavily-used writing instrument on the Apollo missions.
The Apollo 13 fix — complete with duct tape — of making a square canister fit into a round hole. Credit: NASA
6. Duct tape, plastic bags, hoses and flight plan covers.
This is the ultimate in macgyvering! As we talked about in the original “13 Things That Saved Apollo 13” series, the crew had to create makeshift CO2 air scrubber out of things they had on the ship. This included duct tape to fashion a Rube Goldberg-like assemblage which the square CO2 filters from the CM to fit the round hole where the LM filters would go – so, fitting a “square peg into a round hole.”
Along with the duct tape were plastic bags that were mostly used for food and other storage, a vacuum-like cleaner/blower and hose that came from the space suits, and cardboard card stock used for the covers of the Apollo reference log manuals. These items all combined to manufacture a simple solution to save the Apollo 13 crew.
Screen shot from Apollo 13 footage showing Jim Lovell with duct tape.
“Without the vacuum like blower called the suit fan and a suitable lengthy hose to route the blower’s airflow to the duct taped filters, rescue might not have happened,” said Woodfill.” “Yes, if not for everyday things on board the ship, perhaps the Apollo 13 crew would not have survived.”
Woodfill often talks to students and he was so taken by how simple things like duct tape saved the crew that he wrote a song ” Tribute to Duct Tape ” which he performs for kids as seen in this video of one of his classes done remotely via Skype:
The Display & Keyboard (DSKY) mounted in the Main Display Console of the Apollo 13 spacecraft, Odyssey. Note the gimbal lock display in the second row. Credit: NASA/The Apollo Flight Journal
It was an unlikely case, having an Apollo command ship disabled thousands of miles from Earth. But during the Apollo 9 mission, the crew had actually conducted a test of firing the Lunar Module’s engines while it was docked to the Command Module. It turned out to be fortuitous to have considered such a situation, but Apollo 9 didn’t have to perform the type of maneuvering under the myriad of conditions Apollo 13 faced.
Steering was among the crucial threats for Jim Lovell and his crew. Without the command ship’s thrusters to steer, only the lander’s were available, and flying the crippled Apollo 13 spacecraft stack and keeping it on the right trajectory was a huge challenge.
During a normal mission, the ship’s computers allowed for much of the navigation, but the Apollo 13 crew had to fly “by hand.” The Command Module was shut down, and the LM’s limited battery power required the shutting down most of its systems, so even backup propulsion and navigation functions were unavailable. Lovell had to struggle to bring the unwieldy two-vehicle craft under control.
Apollo 13 commander Lovell with a model Lunar module. Image credit: NASAThe lander’s steering was fashioned to handle only its mass and center of mass location. Now it had to steer the entire assemblage, which included the dead mass of the Command and Service Module as well as the lander. Then there was oxygen venting from the damaged tanks in the SM. This all contributed to putting the stack through contortions of pitch, roll, and yaw.
Even now, oxygen spewed from Odyssey’s side like blood from a harpooned whale. The escaping gas acted like a small rocket, fighting Lovell’s efforts to stabilize the joined craft – which the astronauts called “the stack” – with Aquarius’s thrusters. Lovell soon found that trying to control the stack from the lander was strange and awkward, like steering a loaded wheelbarrow down the street with a long broom handle. When he nudged the hand controller the joined craft wobbled unpredictably. It was, Lovell would say later, like learning to fly all over again. And he had to learn fast, because if he let the spacecraft drift uncontrolled, there was a danger that one of Aquarius’s gyros would be immobilized – a condition called gimbal lock that would ruin the alignment of the navigation platform. With no way of sighting in the stars, there would be no hope of realigning it….
“I can’t take that doggone roll out, “Lovell said. Throughout the next 2 hours Lovell wrestled with his unwieldy craft, as the time for the free-return maneuver approached. He wondered if Aquarius would be able to point them toward home, and whether it would last long enough to get them there. Lovell and his crew had become the first astronauts to face the very real possibility of dying in space.
From “A Man on the Moon,” chapter 7, “The Crown of an Astronaut’s Career”
by Andrew Chaikin
Used by permission.
One of the items discussed in the original “13 Things That Saved Apollo 13” was how well suited rookie Apollo crewman Jack Swigert was to the Apollo 13 mission, as he was said to have basically ‘wrote the book’ on Command Module malfunctions. Likewise, says NASA engineer Jerry Woodfill, was Commander Jim Lovell’s ability as Apollo 13’s helmsman.
“Tales are often shared about Lovell’s skills as a naval aviator,” said Woodfill, “making aircraft carrier deck landings in the dark with a malfunctioning display, or in storm-tossed seas.”
Being able to judge aircraft descent rates and attitude with respect to a wave-tossed carrier deck was a challenge. Woodfill said this ideally trained Lovell for avoiding gimbal-lock on Apollo 13.
An annotated image of the Apollo Flight Director Attitude Indicator, commonly called the navigation 8-ball. Via Kerbal Space Program.
“Gimbal-lock meant the guidance system could no longer trust its computer,” explained Woodfill. “The guidance system’s orthogonal gyroscopes (gyros) judged the degree of pitch, roll, and yaw. Gimbal-lock exceeded the system’s ability to gauge position. Such an instance could be compared to an automobile’s tires slipping on an icy road. Steering becomes almost useless in such an event.”
Historian and journalist Amy Shira Teitel recently posted this video in regards to gimbal lock and Apollo 13:
Then, later came a second dire “steering” challenge to Lovell and his crew. Apollo ships required a rotating maneuver about their longest axis known as Passive Thermal Control (PTC), nicknamed the rotisserie, to protect one part of the spacecraft from continually being baked by the Sun. Normally, this was done by the CM’s computer, and the LM’s computer didn’t have the software to perform this operation. Lovell had to maneuver the unwieldy ship by hand nearly every hour to perform the “slow motion barbeque spin” as Chaikin called it. Without the CM’s orientation control thrusters and having the center of gravity extremely off-center with respect to the lander’s control system, it made the situation problematical.
“Lovell seemed to have the ability to quickly adapt to difficult situations,” said Woodfill, “and the knack of quickly coming up with solutions to problems.”
But that’s part of the makeup of being a test pilot and what distinguished the men who were chosen to be astronauts in the Apollo program.
“As great a pilot as Jim Lovell was, I think any of the Apollo commanders could have handled that situation from a piloting point of view,” Chaikin told Universe Today via phone. “One benefit that Lovell brought to the situation was his calm, composed personality—a real asset during that entire ordeal.”
As Chaikin quoted original Apollo 13 crew member Ken Mattingly in “A Man on the Moon,” if Apollo 13 had to happen to any spacecraft commander, there wasn’t anyone who could have handled it better than Jim Lovell.
Nancy Atkinson with Jim Lovell in 2010 at the Abraham Lincoln Presidential Museum.
Here’s an additional, more technical description of gimbal lock:
This view of the severely damaged Apollo 13 Service Module (SM) was photographed from the Lunar Module/Command Module (LM/CM) following SM jettisoning. As seen here, an entire panel on the SM was blown away by the apparent explosion of oxygen tank number two located in Sector 4 of the SM. Credit: NASA.
The explosion of a liquid oxygen tank in Apollo 13’s Service Module violently propelled debris and a 13-foot (4 meter) outer panel of the SM out into space.
Later, the crew saw the damage when they jettisoned the SM prior to reentering Earth’s atmosphere. Commander Jim Lovell described the scene:
“There’s one whole side of the spacecraft missing!” Lovell radioed to Mission Control. “Right by the high-gain antenna, the whole panel is blown out, almost from the base to the engine.”
The panel was likely blasted outward and rearward, toward the deep space S-Band radio antenna. The antenna was attached to the outer edge of the module’s rear base via a meter-long strut, and was used for both telemetry and voice communications.
NASA engineer Jerry Woodfill feels this hi-gain antenna was surely struck by the panel and/or schrapnel ejected by the oxygen tank explosion.
“That deep space radio communication was maintained during and after the explosion was almost miraculous,” Woodfill said. “Such a blow should have destroyed that hi-gain antenna. Those of us who watched the telemetry display monitors saw only a momentary flickering of the telemetry, but after a few flickers we continued to receive data.”
Woodfill said it was as though a boxer had taken a devastating punch and continued to stand unfazed.
This video of the severely damaged Apollo 13 service module was taken by the crew after it was jettisoned.
If instead, the antenna had been destroyed, the loss of data would have resulted in an impaired ability to analyze the situation and communicate with the crew.
The moments following the explosion are seared into Woodfill’s memory. On the night of April 13, 1970, 27-year-old Woodfill sat at his console in the Mission Evaluation Room (MER) in Building 45 at Johnson Space Center — next door to Mission Control in Building 30 — monitoring the caution and warning system.
Jerry Woodfill working in the Apollo Mission Evaluation Room. Credit: Jerry Woodfill.“Because I was watching the command ship’s telemetry on a monitor at the moment of the explosion, both the words heard in my headset, “Houston, we’ve had a problem” and the scene I saw of the video monitor have not been forgotten” Woodfill said. “Seconds before I heard the audio of Jack Swigert’s call, I watched the video screen flicker several times.
To this day, Woodfill said he cannot understand how it continued to function following the explosion.
“As an engineer, I have studied the basics of simple machines,” he said. “The concept of the lever arm dictates that when an explosive blow strikes a structure atop an arm, the arm must bend back about its attachment to the supporting structure. In this case, that structure was the command ship’s supply module, the Service Module. Later photos by the crew (below) showed the antenna intact and the conical reflector dishes present with their center probes intact. In my mind, the entire assembly simply should have been severed altogether.”
An Apollo high gain antenna, on display at the Stafford Air & Space Center, Weatherford, Oklahoma.
The Unified S-band (USB) system was a tracking and communication system that combined television, telemetry, command, tracking and ranging into a single system. The high-gain antenna consisted of an 11-inch-diagonal wide-beam horn flanked by an array of four 31-inch-diameter parabolic reflectors. Its multifunctional system simplified operations, and its construction saved on weight.
And obviously, it was very durable.
Woodfill reiterated how important it was that the antenna survived the explosion.
“Later on it wasn’t needed, as the crew used the Lunar Module communication system,” said Woodfill, “but having that initial continuous communication was one of the things that was very important.”
This color view of the severely damaged Apollo 13 Service Module (SM) was photographed with a motion-picture camera from the Lunar Module/Command Module following SM jettison. Credit: NASA.
And later those in Mission Control and the MER were be able to go back and look at the data that had been transmitted to Earth during that very crucial period of the mission, to help understand what had actually occurred.
“It was critical to have that data in those first moments of the explosion to analyze what had happened,” Woodfill said. “Uninterrupted communication was essential to investigating the status of the vehicle. While it may be true that the backup omni-antenna might have provided temporary communication, based on my analysis, the omni-antenna would not have served as ably during the time of greatest initial peril. In fact, to configure its use with the NASA world-wide tracking network would have caused an unfortunate delay.”
Here are some zoomed-in photos taken by the crew of Apollo 13 after the explosion of the S-Band/hi-gain antenna, and Woodfill has noted the parts of the antenna. They show the explosion failed to sever the hi-gain antenna mast and the conical dish receivers as well as the rectangular antenna, and the center probes of the conical dishes appear intact. Considering the force of the explosion, this is remarkable.
At left, a view of the Service Module and the S-Band antenna during a previous Apollo mission. At right is a zoomed in look at the damaged SM and the unfazed S-Band antenna on Apollo 13, taken during SM jettison. Credit: NASA/Jerry Woodfill.
An annotated closeup of the S-Band/Hi Gain antenna on Apollo 13 after the explosion. Credit: NASA/Jerry Woodfill.
Apollo 13 images via NASA. Montage by Judy Schmidt.
Schematics of the Apollo command module interior. The surge tank was located in the left hand intermediate equipment bay. Credit: NASA.
Join Universe Today in celebrating the 45th anniversary of Apollo 13 with insights from NASA engineer Jerry Woodfill as we discuss various turning points in the mission.
Within minutes of the accident during the Apollo 13 mission, it became clear that Oxygen Tank 2 in the Service Module had failed. Then Mission Control radioed up procedures and several attempts were made to try to save the remaining oxygen in Tank 1. But the pressure readings continued to fall, and it soon became obvious that Tank 1 was going to fail as well. At that point, both the crew and those in Houston realized the extreme seriousness of the situation.
No oxygen meant the fuel cells would be inoperative, and the fuel cells produced electrical power, water and oxygen – three things vital to the lives of the crew and the life of the spacecraft.
For power in the Command Module, all that was left were the batteries, but they were to be the sole source of power available for reentry. Besides the ambient air in the CM, the only oxygen remaining was contained in a so called ‘surge tank’ and three reserve one pound O2 tanks. These, too, were also mainly reserved for reentry, but they were automatically tapped in emergencies if there any oxygen fluctuations in the system.
In Chris Kraft’s autobiography Flight: My Life in Mission Control, the former flight director and former director of Johnson Space Center cited Gene Kranz’ decision to immediately isolate or seal off the surge tank as being one of the things that made rescuing the crew possible.
Why was it so essential to assure that the spare oxygen surge tank in the CM was protected?
“With the luxury of nearly a half century to review each decision made during those April days in 1970,” said NASA engineer Jerry Woodfill, “we can look back and see that those in Mission Control indeed made the right decisions, but at the time, many of those decisions had to be made without knowing the full extent of the problem. But more importantly, they had the presence of mind to look beyond their immediate problem and see the big picture of how to save Apollo 13.”
Shortly after the accident, electrical output readings for fuel cells 1 and 3 were at zero. Fuel cell 2 was still working, but without oxygen from the main tanks, it began to pull oxygen from the reserve surge tank. The 3.7 lb capacity tank was called a ‘surge tank’ because one of its functions was to absorb pressure fluctuations in the oxygen system. Due to the depletion of the two main oxygen tanks, the remaining fuel cell 2 began to automatically pull from the surge tank’s small supply of oxygen.
However, the surge tank also served as the reserve tank of oxygen that the crew would use to breathe during reentry to Earth after the Service Module (with -– during a normal mission — its two large full and functioning oxygen tanks) had been jettisoned. But with those tanks damaged and empty, the remaining fuel cell was starting to draw on the surge tank’s small supply in order to keep power flowing.
Kranz’ decision to isolate the tank was important, but of course, he didn’t make that decision alone. In an article in IEEE Spectrum, the EECOM (Electrical Environmental and Consumables) officer for Apollo 13 Sy Liebergot, recalled the moment he realized the Service Module was running out of power and oxygen — permanently. He, too, didn’t make that realization alone.
Sy Liebergot, EECOM in Mission Control on Apollo 13. Image courtesy Sy Liebergot.
As writer Stephen Cass explained in IEEE Spectrum, “Each flight controller in mission control was connected via so-called voice loops–pre-established audio-conferencing channels–to a number of supporting specialists in back rooms who watched over one subsystem or another and who sat at similar consoles to those in mission control.” (This includes the Mission Evaluation Room where Jerry Woodfill monitored the Caution and Warning System.)
Liebergot was in communications with a team down the hall from Mission Control in Building 30, consisting of Dick Brown, a power-systems specialist, and George Bliss and Larry Sheaks, both life support specialists. When they confirmed the surge tank was being tapped, they realized they had to revise their priorities, from stabilizing Odyssey to preserving the command module’s re-entry reserves so that the crew could eventually return to Earth.
Liebergot said his call to isolate the surge tank initially took Kranz off guard, as it was exactly opposite of what was needed to keep the last fuel cell operating.
But Liebergot and his team were looking ahead. “We want to save the surge tank which we will need for entry,” writer Cass quoted Liebergot, and Kranz almost immediately understood. “Okay, I’m with you. I’m with you,” said Kranz resignedly, and he ordered the crew to isolate the surge tank.
Chris Kraft with his new flight directors before the Gemini 4 mission. (Clockwise from lower right: Kraft, Gene Kranz, Glynn Lunney and John Hodge.) Credit: NASA.
“Because Gene was Flight Director at the time of the determination,” explained Woodfill, “his decisions result from inputs from a team of experts. He, like all the lead flight directors, is, ultimately, responsible for determining and weighing inputs from the chief system controllers who likewise receive instructions and information from a support team. To this end, ‘Flight’ is responsible for the final decision which is passed to the CapCom who, in turn, instructs the astronaut crew to act. Based on the process, often, an unknown expert might have been the original source of the instruction.”
This demonstrates how it was a team effort to save Apollo 13, and decisions that may have initially seemed incomprehensible ended up being the right ones.
“Loss of either Command Module capability — entry battery power or oxygen — threatened to be a fatal situation during the capsule’s entry return to Earth,” said Woodfill. Fortunately, as stated in one of our articles the first series of “13 Things,” a ‘jumper-charge technique dealt with the recharging the reentry batteries in the CM.
But while the LM had ample oxygen – in the form of oxygen tanks for repressurization after moon walks, tanks in the lander’s descent and ascent stages, and in the Portable Life Support System (PLSS) in the spacesuits that would have been used during moonwalks — apparently, there was no such similar way to replace oxygen in the CM from the lander’s oxygen stores.
Woodfill noted that had the surge tank been expended by the failed service module O2 tanks, there likely could have been a backup reentry plan of the crew wearing their launch suits and some type of jury-rigged system of using the oxygen from the PLSS system’s oxygen.
“A ‘shirt-sleeve’ entry would not have been the case,” said Woodfill. “This could have entailed a process similar to three scuba divers breathing from a pair of aqua lungs following the failure of one of the three.”
Woodfill noted one interesting fact. “Both Mission Control and the crew of Apollo 13 were so certain of the availability of surge tank oxygen that everyone agreed reentry would be space-suit-less.”
The jettisoning of elements during the critical last hours of the Apollo 13 mission is shown in this sequence drawing. Credit: NASA.
Join Universe Today in celebrating the 45th anniversary of Apollo 13 with insights from NASA engineer Jerry Woodfill as we discuss various turning points in the mission.
The final scenes of the movie Apollo 13 depict the spacecraft’s dramatic reentry into Earth’s atmosphere. As the seconds count beyond the time radio blackout should have lifted, the Capcom calls for Apollo 13’s crew to answer, but there is no response.
Everyone’s thoughts run through the possibilities: Had the heat shield been compromised by shrapnel from the exploded oxygen tank? Had the previously finicky hatch failed at this critical time? Had the parachutes turned to blocks of ice? Had the Inertial Measurement Unit (IMU) gyros failed, having inadequate time to warm-up causing the capsule to skip off the atmosphere, or incinerate with the crew in a fiery death plunge to Earth?
Of course, the crew finally did answer, but confirmation that Lovell, Haise and Swigert had survived reentry came nearly a minute and a half later than expected.
Some might feel director Ron Howard may have over-sensationalized the re-entry scenes for dramatic effect. But in listening to the actual radio communications between Mission Control and the ARIA 4 aircraft that was searching for a signal from the Apollo 13 crew, the real drama is just as palpable – if not more — than in the movie.
For virtually every reentry from Mercury through Apollo 12, the time of radio blackout was predictable, almost to the second. So why did Apollo 13’s radio blackout period extend for 87 seconds longer than expected, longer than any other flight?
The view in Mission Control after Apollo 13 landed safely. Credit: NASA.
During the Apollo era, the radio blackout was a normal part of reentry. It was caused by ionized air surrounding the command module during its superheated reentry through the atmosphere, which interfered with radio waves. The radio blackout period for the space shuttle program ended in 1988 when NASA launched the Tracking and Data Relay Satellite System (TDRS), which allowed nearly constant communication between the spacecraft and Mission Control.
It is difficult to find official NASA documentation about the extended radio blackout time for Apollo 13. In the mission’s Accident Review Board Report, there’s no mention of this anomaly. The only discussion of any communication problem comes in a section about reentry preparations, after the Service Module was jettisoned. There was a half-hour period of very poor communications with the Command Module due to the spacecraft being in a poor attitude with the Lunar Module still attached. Some of the reentry preparations were unnecessarily prolonged by the poor communications, but was more of a nuisance than an additional hazard to the crew, the report said.
In numerous interviews that I’ve done and listened to in preparation for this series of articles, when those involved with the Apollo 13 mission are asked about why the blackout period was longer than normal, the answer normally comes as a hedged response, with the crew or a flight director indicating they don’t know exactly why it happened. It seems analysis of this has defied a reasonable and irrefutable scientific explanation.
Overall view showing some of the activity in the Mission Operations Control Room during the final 24 hours of the Apollo 13 mission. From left to right are Shift 4 Flight Director Glynn Lunney, Shift 2 Flight Director Gerald Griffin, Astronaut and Apollo Spacecraft Program Manager James McDivitt, Director of Flight Crew Operations Deke Slayton and Shift 1 Flight Surgeon Dr. Willard Hawkins. Credit: NASA.
At an event at the Smithsonian Air & Space Museum in 2010, Apollo 13 Flight Director Gene Kranz said he never heard an answer or explanation that he believed, and Fred Haise chuckled and said, “We just did Ron Howard a favor!”
Jim Lovell gave the most detailed response – which is the one most often given as a likely explanation — suggesting it perhaps had to do with a shallowing reentry angle problem, with a strange space-like breeze that seemed to be blowing the spacecraft off-course with respect to entry.
“I think the reason why it was longer was the fact we were coming in shallower than we had planned,” Lovell said at the 2010 event. “Normally we come in from a Moon landing and have to hit the atmosphere inside a very narrow pie-shaped wedge and I think we were continually being pushed off that wedge. The reason was, we found out about 2-3 months after from analysis, was the lander’s venting of cooling vapor. The way we cool the electronic systems in LM was to pass water through a heat exchanger, and that water evaporates into space. That evaporation — which would be insignificant during a normal lunar landing mission — was going on for the 4 days we were using the LM as a lifeboat, acting as a small force, forcing us off the initial trajectory.”
Coming in on a shallower trajectory would result in a longer period in the upper atmosphere where there was less deceleration of the spacecraft. In turn, the reduced pace of deceleration lengthened the time that the heat of reentry produced the ionized gasses that would block communications.
The Apollo 13 spacecraft heads toward a splashdown in the South Pacific Ocean. Note the capsule and its parachutes just visible against a gap in the dark clouds. Credit: NASA.
But NASA engineer Jerry Woodfill offers additional insight into the communication delays. He recently spoke with Jerry Bostick, the Flight Dynamics Officer (FIDO) for Apollo 13, who told him, “Many believe the added time resulted from the communication signal skipping, like a stone, over layers of the upper atmosphere because of the shallow entry angle.”
“Bostick likened the radio signals to a stone skipping on a pond, and finally, the signal found a location to sink Earthward,” Woodfill said.
However, this explanation too, leaves questions. Woodfill said he has studied the “signal skipping” phenomenon, and has found information to both support and refute the concept by virtue of when such an occurrence could be expected.
“The consensus was it is a night time phenomena,” Woodfill said. “Apollo 13 entered in daylight in the Pacific and in Houston. Nevertheless, the question to this day demonstrates just how near Apollo 13 came to disaster. If the radio signal almost skipped off the Earth’s atmosphere, one wonders, just how very close was Apollo 13’s capsule and crew near to a fatal skipping into the oblivion of space as well.”
Another “angle” on Apollo 13’s reentry was how it very nearly escaped another potential disaster: landing in a typhoon. A group of flight controllers gather around the console of Shift 4 Flight Director Glynn Lunney (seated, nearest camera) in the Mission Operations Control Room. Their attention is drawn to a weather map of the proposed landing site in the South Pacific. Among those looking on is Christopher Kraft, Manned Spacecraft Center Deputy Director, (standing, in black suit, right). Credit: NASA.
“A tropical storm is a retro’s (retrofire officer) worst nightmare,” said Woodfill. “Knowing how unpredictable the movement and intensity of such storms are makes selecting a landing site difficult. No NASA reentry had ever landed in a tropical storm, and Apollo 13 might be the first. Among NASA scientists are meteorologists, and by their best science, they predicted that Tropical Storm Helen would move into the designated Apollo 13 landing site the day of reentry and splashdown.”
If Apollo 13 had splashed down amidst the storm, the capsule may have drifted and been lost at sea. To conserve the entry battery power, the beacon light recovery system had been deactivated. The crew would have been invisible to those looking for the capsule bobbing up and down in the Pacific Ocean. They eventually would have had to blow the hatch, and the Apollo 13 capsule likely would have sunk, similar to Gus Grissom’s Liberty Bell during the Mercury program. But the crew of Apollo 13 might not have been as fortunate as Grissom who had helicopter rescuers overhead quickly pulling him to safety.
However, the decision was made to ignore the weather forecasts, which ended up being fortuitous because Helen ultimately changed course. But then there was the uncertainty of the entry location due to the ‘shallowing’ the spacecraft was experiencing.
“Once more, the retro made the decision to ignore that shallowing at reentry in the same fashion as he had ignored the weathermen’s ominous prediction,” said Woodfill. “In both instances, the retro was correct. He rightly predicted that the drift would not be a problem in the final stages of reentry after the lander was jettisoned. Again, this was altogether fortuitous in that no one knew the lander’s cooling system was the source of the drift. Earlier, however, the retro had compensated for the shallowing drift by bringing Apollo 13 into the correct entry corridor angle via first having the crew fire the lander’s descent engine and later the lander’s thrusters.”
An approximate representation of Apollo 13’s re-entry groundtrack. Click the image for access to a larger pdf version.
As it turned out those mysterious extra seconds caused by coming in at a shallow angle were also fortuitous.
While the added time of communications blackout was nail-biting, the more shallow and longer angle “added to the downrange path of Apollo 13, dropping the capsule in calm water so near the waiting aircraft carrier Iwo Jima that the accuracy was among the finest of the program,” Woodfill said.
Revisiting the length of the communications blackout, there are some discrepancies in various sources about the length of the extra time Apollo 13’s blackout time lasted. Some websites lists 25-30 seconds, others a minute. Again, I was unable to find an ‘official’ NASA statement on the subject and the transcript of the technical air to ground voice communications does not include time stamps for the beginning and end of blackout. Additionally, two of the definitive books about Apollo 13 – Lost Moon by Jim Lovell and Jeffrey Kluger, and A Man on the Moon by Andrew Chaikin – don’t give exact numbers on the timing of the blackout.
“Per my mission log it started at 142:39 and ended at 142:45— a total of six minutes,” Kranz told journalist Joe Pappalardo in 2007. “Blackout was 1:27 longer than predicted … Toughest minute and a half we ever had.”
87 seconds also is confirmed by a transmission recorded on one of the ARIA, the Apollo/Advanced Range Instrumentation Aircraft, which provided tracking and telemetry information for the Apollo missions, especially at launch and reentry, when the Manned Spaceflight Network tracking could not.
Captain David Dunn served as the Mission Co-ordinator onboard ARIA 4. Image via Honeysuckle Creek Tracking Station and David Dunn.
Space Historian Colin Mackellar from the Honeysuckle Creek website told Universe Today that until it was recently published on the Honeysuckle Creek website, the recording had not been heard by anyone other than Dunn’s family. Mackellar explained that it contains simultaneous audio of the NASA Public Affairs commentary, audio of the Flight Director’s loop, the ARIA transmissions and a portion of the Australian Broadcast Commission radio coverage.
Again, you can hear the palpable tension in the recording, which you can listen to at this link. At 7:21 in the audio, as communications blackout nears the predicted end, one of the ARIA communicators asks ARIA 4 if they can see the spacecraft. Negative is the reply.
At 7:55 you can hear Kranz asking if there is any acquisition of signal yet. Again at 8:43, Kranz asks, “Contact yet?” The answer is negative. Finally, at 8:53 in the audio, ARIA 4 reports AOS (acquisition of signal), which is relayed to Kranz. You can hear his relieved exhalation as he replies, “Rog (roger).”
Then comes Kranz saying, “Capcom, why don’t you try giving them a call.”
The ARIA 4 Prime Mission Electronic Equipment crew and the flight crew with the ARIA 4 specially equipped C-135 aircraft. Image via Honeysuckle Creek Tracking Station and Captain David Dunn.
It required no great imagination to know that back in the US, and in fact all around the world, folks were glued to their TV sets in anticipation, and that Walter Cronkite was holding forth with Wally Schirra on CBS, and at the Houston Space Center breathing had ceased.
But we were there, ground zero, with front row seats and we would be the first to know and the first ones to tell the rest of the world if the Apollo 13 crew had survived…
On all the aircraft and all the airwaves there was complete silence as well as we all listened intently for any signal from Apollo 13.
ARIA 2 had no report of contact; ARIA 3 also had no report.
Then I observed a signal and Jack Homan, the voice radio operator advised me we had contact.
From Apollo 13 came the reply “OK, Joe……” relayed again from our radios to Houston and the rest of the world. Not much, but even such a terse reply was enough to let the world know the spacecraft and its crew had survived. In an age before satellite TV, teleconferencing, and the Internet, it was easy for us in the clouds at 30,000 feet above the splashdown zone to visualize breathing resuming in Houston and around the world.
Dunn concluded, “Now, exactly why would Ron Howard leave such a dramatic moment out of his film? There’s a real mystery!”
Apollo 13 images via NASA. Montage by Judy Schmidt.
