13 MORE Things That Saved Apollo 13, part 6: The Mysterious Longer-Than-Expected Communications Blackout

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.
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.
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.
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 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.
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.

But Air & Space Magazine quoted Gene Kranz as saying it was 87 seconds.

“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.

ARIA 4 had the distinction of being the first to reacquire Apollo 13 after the longer-than-expected communication blackout, as it was near the predicted point of reentry. Captain David Dunn, who served as the Mission Coordinator onboard the ARIA 4 aircraft, provided a recording to historians at the Honeysuckle Creek Tracking Station, who have put together a wonderful history of their role in the Apollo missions.

Captain David Dunn served as the Mission Co-ordinator onboard ARIA 4. Image via Honeysuckle Creek Tracking Station and David Dunn.
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.”

Capcom: “Odyssey, Houston standing by.”
Swigert: “OK, Joe.”

When the crew splashed down, the official duration time of the mission was 142 hours, 54 minutes and 41 seconds.

Dunn wrote about his experiences for the Honeysuckle Creek history website:

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.
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.
Apollo 13 images via NASA. Montage by Judy Schmidt.

Tomorrow: Isolating the Surge Tanks

Previous 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

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

13 MORE Things That Saved Apollo 13, part 5: The CO2 Partial Pressure Sensor

The Apollo 13 accident crippled the spacecraft, taking out the two main oxygen tanks in the Service Module. While the lack of oxygen caused a lack of power from the fuel cells in the Command Module, having enough oxygen to breathe in the lander rescue craft really wasn’t an issue for the crew. But having too much carbon dioxide (CO2) quickly did become a problem.

The Lunar Module, which was being used as a lifeboat for the crew, had lithium hydroxide canisters to remove the CO2 for two men for two days, but on board were three men trying to survive in the LM lifeboat for four days. After a day and a half in the LM, CO2 levels began to threaten the astronauts’ lives, ringing alarms. The CO2 came from the astronauts’ own exhalations.

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

NASA engineer Jerry Woodfill helped design and monitor the Apollo caution and warning systems. One of the systems which the lander’s warning system monitored was environmental control.

Like carbon monoxide, carbon dioxide can be a ‘silent killer’ – it can’t be detected by the human senses, and it can overcome a person quickly. Early on in their work in assessing the warning system for the environmental control system, Woodfill and his co-workers realized the importance of a CO2 sensor.

“The presence of that potentially lethal gas can only be detected by one thing – an instrumentation transducer,” Woodfill told Universe Today. “I had an unsettling thought, ‘If it doesn’t work, no one would be aware that the crew is suffocating on their own breath.’”

The sensor’s job was simply to convert the content of carbon dioxide into an electrical voltage, a signal transmitted to all, both the ground controllers, and the cabin gauge.

Location of Caution And Warning System lights in the Command Module. Credit: Project Apollo - NASSP.
Location of Caution And Warning System lights in the Command Module. Credit: Project Apollo – NASSP.

“My system had two categories of alarms, one, a yellow light for caution when the astronaut could invoke a backup plan to avoid a catastrophic event, and the other, an amber warning indication of imminent life-threatening failure,” Woodfill explained. “Because onboard CO2 content rises slowly, the alarm system simply served to advise and caution the crew to change filters. We’d set the threshold or “trip-level” of the alarm system electronics to do so.”

And soon after the explosion of Apollo 13’s oxygen tank, the assessment of life-support systems determined the system for removing carbon dioxide (CO2) in the lunar module was not doing so. Systems in both the Command and Lunar Modules used canisters filled with lithium hydroxide to absorb CO2. Unfortunately the plentiful canisters in the crippled Command Module could not be used in the LM, which had been designed for two men for two days, but on board were three men trying to survive in the LM lifeboat for four days: the CM had square canisters while the LM had round ones.

The fix for the lithium hydroxide canister is discussed at NASA Mission Control prior to having the astronauts implement the procedure in space. Credit: NASA
The fix for the lithium hydroxide canister is discussed at NASA Mission Control prior to having the astronauts implement the procedure in space. Credit: NASA

As was detailed so well by Jim Lovell in his book “Lost Moon,” and subsequently portrayed in detail in the movie “Apollo 13,” a group of engineers led by Ed Smylie, who developed and tested life support systems for NASA, constructed a duct-taped-jury-rigged CO2 filter, using only what was aboard the spacecraft to convert the plentiful square filters to work in the round LM system. (You can read the details of the system and its development in our previous “13 Things” series.)

Needless to say, the story had a happy ending. The Apollo 13 accident review board reported that Mission Control gave the crew further instructions for attaching additional cartridges when needed, and the carbon dioxide partial pressure remained below 2mm Hg for the remainder of the Earth-return trip.

But the story of Jerry Woodfill and the CO2 sensor can also serve as an inspiration to anyone who feels disappointed in their career, especially in STEM (science, technology, engineering and math) fields, feeling that perhaps what you are doing doesn’t really matter.

“I think almost everyone who came to NASA wanted to be an astronaut or a flight director, and I always felt my career was diminished by the fact that I wasn’t a flight controller or astronaut or even a guidance and navigation engineer,” Woodfill said. “I was what was called an instrumentation engineer. Others had said this is the kind of job that was superfluous.”

Woodfill worked on the spacecraft metal panels which housed the switches and gauges. “Likely, a mechanical engineer might not find such a job exciting,” he said, “and to think, I had once studied field theory, quantum electronics and other heady disciplines as a Rice electrical engineering candidate.”

NASA engineer Jerry Woodfill with Chris Kraft, former NASA flight director and manager, in early 2015. Image courtesy Jerry Woodfill.
NASA engineer Jerry Woodfill with Chris Kraft, former NASA flight director and manager, in early 2015. Image courtesy Jerry Woodfill.

Later, to add to the discouragement was a conversation with another engineer. “His comment was, ‘No one wants to be an instrumentation engineer,” Woodfill recalled, “thinking it is a dead-end assignment, best avoided if one wants to be promoted. It seemed that instrumentation was looked upon as a sort of ‘menial servant’ whose lowly job was servicing end users such as radar, communications, electrical power even guidance computers. In fact, the users could just as readily incorporate instrumentation in their devices. Then, there would be no need for an autonomous group of instrumentation guys.”

But after some changes in management and workforce, Woodfill became the lead Command Module Caution and Warning Project Engineer, as well as the Lunar Lander Caution and Warning lead – a job he thought no one else really wanted.

But he took on the job with gusto.

“I visited with a dozen or more managers of items which the warning system monitored for failure,” Woodfill said. He convened a NASA-Grumman team to consider how best to warn of CO2 and other threats. “We needed to determine at what threshold level should the warning system ring an alarm. All the components must work, starting with the CO2 sensor. The signal must pass from there through the transmitting electronics, wiring, ultimately reaching my warning system “brain” known as the Caution and Warning Electronics Assembly (CWEA).”

And so, just hours after the explosion on Apollo 13, the Mission Engineering Manager summoned Woodfill to his office.

“He wanted to discuss my warning system ringing carbon dioxide alarms,” Woodfill said. “I explained the story, placing before him the calibration curves of the CO2 Partial Pressure Transducer, showing him what this instrumentation device is telling us about the threat to the crew.”

Now, what Woodfill had once had deemed trivial was altogether essential for saving the lives of an Apollo 13 astronaut crew. Yes, instrumentation was just as important as any advanced system aboard the command ship or the lunar lander.

“And, I thought, without it, likely, no one would have known the crew was in grave danger,” said Woodfill, “let alone how to save them. Instrumentation engineering wasn’t a bad career choice after all!”

The Apollo 13 fix -- complete with duct tape -- of making a square canister fit into a round hole.  Credit: NASA
The Apollo 13 fix — complete with duct tape — of making a square canister fit into a round hole. Credit: NASA
This is an example of the team effort that saved Apollo 13: that the person who was working on the transducer years prior was just as significant as the person who came up with the ingenious duct tape solution.

And it was one of the additional things that saved Apollo 13.

Apollo 13 images via NASA. Montage by Judy Schmidt.
Apollo 13 images via NASA. Montage by Judy Schmidt.

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 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.

13 Things That Saved Apollo 13, Part 10: Duct Tape

[/caption]
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.

It’s the handy man’s secret weapon, and has become a must-have item for astronauts, too. While duct tape alone didn’t save the Apollo 13 crew, it certainly would have been difficult for them to have survived without it. Even though the accident which crippled the ship took out the two main oxygen tanks in the Service Module, having enough oxygen really wasn’t an issue for the crew. A big problem was having too much carbon dioxide (CO2), which came from the astronauts’ own exhalations.

The Lunar Module had lithium hydroxide canisters to remove the CO2 for two men for two days, but on board were three men trying to survive in the LM lifeboat for four days. However, with a little ingenuity and duct tape, the Apollo Mission Operations Team was able to fit “a square peg in a round hole.”

The Mission Evaluation Room for Apollo. Image courtesy Jerry Woodfill.

“Any of us in the Mission Evaluation Room (MER) might be called upon to assist in an Apollo 13 ‘solution,’” said Jerry Woodfill, who helped design and monitor the Apollo caution and warning systems. The MER was where the spacecraft systems engineers were stationed during a mission, and should a problem arise on any Apollo mission, the “MER-men” were called on for expert advice.

“Should an inexplicable glitch in an alarm occur, I might be consulted,” Woodfill said, “and I was – when the carbon dioxide levels began to threaten the astronauts’ lives, ringing alarms. However, to this day, I am proud that the Command Module’s alarm system was the first warning alerting Mission Control and Lovell’s crew to the life-threatening problem.”

The MER engineering team was led by Don Arabian. “His loud, challenging voice could carry the entire length of the Mission Evaluation Room,” Woodfill said. “Despite his fierce personality, he was a brilliant engineer. No forensic engineer working with any attorney had a greater ability of assessing a spacecraft mission anomaly than Don Arabian.”

Additionally, Woodfill said, Arabian was wholly unorthodox in his management approach. “He feared no man above or below his pay grade. He was honest almost to the point of embarrassment. He would not ‘sugar coat’ any situation Apollo 13 was dealing with as far as the press was concerned.”

Woodfill recalled how Arabian commanded the MER team from the “throne-like” center seat of a long table perpendicular to tables of engineers. “He was, perhaps 20 feet from my station as the Caution and Warning Apollo 13 Engineer. Don never intimidated me, though I had felt nervous about many of my superiors. Don had that same quality of leadership Gene Kranz possessed. He was fair with lower level workers and respected their knowledge.”

For that reason, Woodfill said he felt privileged rather than frightened when summoned to Arabian’s private office to discuss the threat to the lives of the Apollo 13 crew, the build-up of CO2 in the spacecraft.

Woodfill had worked with the environmental system engineers to establish an alarm level based on the percentage of CO2 in the cabin atmosphere. The idea was to use the warning system as an alert for changing the filters.

With the CO2 alarms ringing on Apollo 13, Woodfill met with Arabian. “As I recall there were three calibration curves, one for three different cabin pressures,” Woodfill said. “Arabian began to throw questions at me across his desk: ‘Is the alarm accurate…is the transducer working correctly…what about the calibration?'”

Woodfill had the information on the calibration curves with him, and together, he and Arabian carefully studied it based on the known cabin pressure, the voltage output from the CO2 transducer and the voltage level at which my warning electronics initiated the alarm.

“Yes, the warning system was telling the right story,” Woodfill said.

Jack Swigert works on the CO2 canister during the Apollo 13 mission. Credit: NASA

But there was a problem with the CO2 “scrubbers,” the lithium hydroxide canisters. The cabin air was fed continuously through environmental control equipment, and the lithium hydroxide reacted with the carbon dioxide and trapped it.

“There were but two round lithium hydroxide canisters in the LM, able to provide filtering for two men for two days,” said Woodfill. “With the trip back to Earth at least four days in length, and three men on board, the carbon dioxide content of the cabin air would rise to poisonous levels, and the crew would expire without a solution.”

Each canister had a life of approximately 24 hours with two men on board. Since there were now three men, that life would be somewhat shortened. The round filters were housed in two separate barrels in the lander. One barrel was plumbed into the cabin’s environmental control system, and the other barrel simply stowed the second cartridge. When the first filter was consumed, the crew simply interchanged the filters in the barrels.

“While there were plenty of filters in the Command Module, these were square and wouldn’t fit in the LM barrel,” Woodfill said. “Without some kind of unusual miracle of making a square peg fit into a round hole the crew would not survive.”

The fix for the lithium hydroxide canister is discussed at NASA Mission Control prior to having the astronauts implement the procedure in space. Credit: NASA

The experts in the MER had 24 hours to deal with the challenge and solve the problem. “My recollection of the threat,” said Woodfill, “besides the earlier meeting with Don Arabian, was Don’s voice bellowing from his throne in the mission evaluation room that Tuesday, ‘I need those guys to come up with an answer on the CO2 thing and do it fast!’ He was referring to the ‘tiger team’ led by Ed Smylie, the crew systems manager working the problem.”

Using only the type of equipment and tools the crew had on board –including plastic bags, cardboard, suit hoses, and duct tape — Smylie and his team conceived a configuration that just might work.

“The concept seemed to evolve as all looked on,” Woodfill said. “It was to attach a suit hose into a port which blew air through the hose into an astronaut’s space suit. If the space suit was eliminated and, instead, the output of the hose somehow attached to the square filter, perhaps, the crew could be saved. This, in effect, would bypass the barrel. The air blown through the filter by the suit fan would have no carbon dioxide as it reentered the cabin atmosphere.”

The biggest challenge was attaching the hose into a funnel-like device having a small round inlet hole for the suit hose and a much larger square outlet attached and surrounding the square filter. But the funnel would most likely leak. Added to that difficulty was the hose and plastic bags tended to collapse restricting the air flow through the filter.

“Then the thought came, ‘Use cardboard log book covers to support the plastic,” said Woodfill. “It worked! But more importantly, they had to figure out how the funnel could be fashioned to prevent leaking. Of course…the solution to every conceivable knotty problem has got to be duct tape! And so it was.”

Screen shot from Apollo 13 footage showing Jim Lovell with duct tape.

Woodfill said that duct tape had been stowed on board every mission since early in the Gemini days.

The contraption that Smylie and his team came up with was checked out in the simulators, which worked, and then the team quickly radioed instructions to the crew, carefully leading them through about an hour’s worth of steps.

At a mission debrief, Jack Swigert noted, “At this point in time I think the partial pressure of CO2 was reading about 15 millimeters. We constructed two of these things and I think within an hour was down to 2 tenths.”
Woodfill watched his systems from the MER. “I saw the alarm light go out and it stayed out the rest of the mission.”

As Jim Lovell wrote in his book “Lost Moon, “The contraption wasn’t very handsome, but it worked.”

And it saved Apollo 13.

Next: Part 11: A Hollywood Movie

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.

13 Things That Saved Apollo 13, Part 8: The Command Module Wasn’t Severed

[/caption]

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.

When the Apollo 13 crew jettisoned the crippled Service Module as they approached Earth, they saw the extent of the damage from the explosion of an oxygen tank. “There’s one whole side of that spacecraft missing!” Jim Lovell radioed to Mission Control, his voice reflecting his incredulousness at seeing the damage of a 13-ft panel blown off the spacecraft. However, the situation could have been more dire. The heat shield on the Command Module could have been damaged. What’s more, NASA engineer Jerry Woodfill said that instead of the panel blowing out, the explosion could have — and maybe should have –severed the Command Module from the Service Module.

Graphic of the CSM. Credit: NASA

Photos taken by the Apollo 13 crew after the service module was jettisoned in preparation for the command module’s reentry via the heat shield revealed that not only was the panel missing from the side of the spacecraft — blown into the vastness of space by the exploding pressure of the detonating oxygen – there was also damage to the Hi Gain Antenna, at the right of the vehicle drawing above, indicating the panel had catapulted into space, striking the antenna. What the images couldn’t show, and what the Apollo 13 crew couldn’t see was if there was any damage to the Command Module’s heat shield.

“The structural design of the interior of the Service Module is that it has a long open tunnel-like volume in the center of the module, about 30 inches by 13 feet,” said Woodfill. “The tunnel is much like a chimney such that gases, liquids, or particles could readily move through it toward the main engine bell at the right and the heat shield at the left. The tunnel is not sealed so that the explosive force of the burning oxygen from the exploded O2 tank 2 could escape into and around the tunnel in the direction of both the heat shield and main engine.”

Woodfill said concern was voiced in Mission Control that shrapnel from the exploding tank had entered the tunnel, and perhaps ultimately caused damage to both the heat shield and main engine. The main engine wasn’t the biggest issue, as the crew was able to use the lunar lander’s descent engine. (see our previous article , “Using the LM for Propulsion.”) But there was only one heat shield, and it had to work to enable the capsule and the crew to survive the fiery reentry through Earth’s atmosphere.

Thankfully, as it turned out ,the heat shield wasn’t damaged.

The recovery of the Apollo 13 Command Module. Credit: NASA

But almost miraculously, Woodfill said, the command module and service module remained connected following the explosion, while the internal pressure of the explosion rocketed the exterior panel into space.

“The attachment strength of the Service Module panel to the structure required a considerable internal pressure of 24 pounds per square inch for severing it from the service module,” Woodfill said. “A much lower pressure was required to separate the Command Module with its heat shield from the Service Module, only 10 pound per square inch. One can only speculate on why the panel blew and the crew capsule/service module attachment remained intact.”

Since there is no air pressure in space, Woodfill explained, the force which held the vehicles together was the strength of their mechanical attachments.

“Two pressures were at work,” he said. “Each attempted to overcome respective attachment forces: the force which attached the Service Module to the Command capsule and the force which attached the Service Module panel to the Service Module. Because the explosive pressure force of the oxygen was immediately applied in great strength to the panel, this overwhelming force would be expected to blast that panel apart from the vehicle, exceeding the 24 pound per square inch attachment strength. However, venting of residual explosive oxygen into the framework of the Service Module could well be expected to overcome the attachment strength between the two vehicles, separating them.”

Yet, it did not. Why?

Sequence photo from 16mm motion picture film of test at Langley Research Center which seeks to determine mechanism by which Apollo 13 panel was separated from Service Module. Credit: NASA. Click image for more information

“Apparently, the presence of ‘tankage’ and other structure acted to mitigate and dissipate the sudden pressure spike before it reached the interface between the vehicles,” Woodfill said. “However, if a shard from the exploded O2 tank 2 had punctured any of the adjacent tanks, likely a secondary explosion of any of them would have propagated both the explosion and build up of pressure. In that event, certainly, the vehicles would have experienced either a fatal separation or fatal damage to the heat shield.

A piece of shrapnel did fracture the plumbing between the oxygen tanks that allowed the oxygen to leak out of Tank 1, causing the complete loss of power in the Command Module, for without oxygen the fuel cells couldn’t work.

Some may say that having the Service Module attached to the Command Module wasn’t important – it was just dead weight anyway. However, other problems could have developed without the Service Module attached, according the Apollo 13 Failure Report. Having the heat shield exposed to low temperatures for a long period could have damaged it, and internal Command Module thermal problems could arise if the Service Module was jettisoned too early.

Additionally, flight control problems were anticipated if the Command Module wasn’t attached.
The immediate loss of the Service Module would have meant immediate loss of the residual power from the fuel cells while the crew and mission control wrestled to understand the problem. This would have required a much greater power drain on those emergency batteries to the extent that one wonders if the later “trickle-charge” from the lander’s batteries would have been sufficient for reentry.

The crew of Apollo 13, Jim Lovell, Jack Swigert and Fred Haise, during a post-flight debrief. Credit: NASA

Of course, since the Service Module was jettisoned before the crew re-entered (and the SM itself later burned up in the Earth’s atmosphere) no one could do any “forensic analysis” or an engineering “autopsy” on that part of the spacecraft.

“To me, it is amazing that, one, the heat shield wasn’t damaged from the explosion, and two, the connection that could withstand higher pressure ended up blowing, while the weaker connection stayed together,” said Woodfill.

But those were among the many things that saved Apollo 13.

Next: Part 9: Which tank was damaged

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.

13 Things That Saved Apollo 13, Part 7: The Apollo 1 Fire

[/caption]
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.

“Far better is it to dare mighty things, to win glorious triumphs, even though checkered by failure than to rank with those poor spirits who neither enjoy much nor suffer much, because they live in a gray twilight that knows not victory nor defeat.” – Theodore Roosevelt

It’s hard to chronicle any of the Apollo flights without mentioning the Apollo 1 fire. And while many believe the Apollo program perhaps wouldn’t have succeeded without that disaster, the sacrifice made by Gus Grissom, Ed White and Roger Chaffee definitely saved the crew of Apollo 13.

“Among the early space missions, I’ve always believed that the greatest courage was needed by their first crews,” said Apollo engineer Jerry Woodfill. “Whether it was Al Shepard, the Apollo 1 crew, or shuttle astronauts John Young or Bob Crippen, the most likely danger would be the first time any new space craft was launched into space. Flaws in design or manufacture could very well be fatal during maiden missions.”

The crew of Apollo 1: Gus Grissom, Ed White and Roger Chaffee. Credit: NASA

On January 27, 1967, during a test on the launch pad with the crew on board, tragedy struck when a flash fire started in the command module. With the pure oxygen environment inside the capsule, the fire quickly proved fatal for the crew before they or workers at the launch pad could get the hatch open. Although the ignition source of the fire was never conclusively identified, the astronauts’ deaths were attributed to a wide range of design and construction flaws in the early Apollo Command Module. The manned phase of the project was delayed for twenty months while these problems were fixed.

“To suggest the dire event of losing three brave astronauts contributing to Apollo 13’s rescue seems almost ludicrous,” said Woodfill, “but the evidence is striking. What Grissom, White and Chaffee contributed to the rescue of Apollo 13 makes them even more heroic than they were when they gave their lives so that men could go to the moon.”

The irony of the whole situation involves the hatch. Following Gus Grissom’s near fatal drowning when his Mercury capsule sank, the Apollo hatch had been redesigned to avoid the kind of unexpected actuation thought to have caused Grissom’s “Liberty Bell 7” to sink.

Gus Grissom and the Liberty Bell 7. Credit: NASA

“Unfortunately, it led to a hatch impossible to open before the Apollo 1 crew expired,” said Woodfill. “Nevertheless, circumstances used Gus, Ed, and Roger’s sacrifice to save other crews in route to the Moon.”

NASA fire-proofed all future Apollo vehicles with non-flammable materials, used a pad atmosphere of a nitrogen/oxygen mix, and coated of all electrical connections to avoid short-circuits.

“Every switch contact and wire was coated with a moisture proofing substance called conformal coating,” said Woodfill. “Were it not for fire-proofing the Apollo command and service modules, Apollo 13, likely, could not have survived reentry. The cold, damp reentry module interior faced extreme condensation of water vapor from the astronauts’ breath. Droplets of water formed behind the display panels.”

Diagram of the Apollo Command Module control panel. Credit: NASA History Office. Click for larger version.

Woodfill said when Apollo 13’s switches were activated for reentry, the interior would surely have burst into flame, were it not for the fireproofing. Condensed water droplets might have short-circuited panel switches, circuit breakers, and connector wiring.

Woodfill said America might never have landed a man on the Moon without Apollo 1. If a fire had occurred on the way to the Moon, it might have ended the will to land men there. “Imagine the horror of the world at such an event,” said Woodfill, “hearing the crew’s painful cries from deep space, ‘We’ve got a fire in the spacecraft.’”

Apollo 1 and the fireproofing of future Apollo spacecraft prevented such an event.

A favorite quote of many managers of the Apollo program, Woodfill said, is from President Theodore Roosevelt, the one posted at the top of this article.

“In a sense, the Apollo One mission was altogether different from Challenger, Columbia, and Apollo 13,” said Woodfill. “No one had dared such a mighty thing as to man the first Apollo spacecraft into orbit. And it, in this case, was fraught with suffering, failure and defeat, rather than a glorious triumph and victory.”

But later, it allowed for great triumph with the success of the Apollo program, and a defying of the odds of the Apollo 13 crew’s survival.

Tomorrow, Part 8: What the Explosion Didn’t Do

Additional 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.

13 Things That Saved Apollo 13, Part 6: Navigating By Earth’s Terminator

[/caption]

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.

The rupture and explosion of Apollo 13’s oxygen tank crippled the spacecraft, endangering the lives of the crew and making a Moon landing not an option. But more problems arose as the perilous flight progressed. Keeping the spacecraft on the right trajectory was a huge challenge for Mission Control, and especially for the crew. Normally, the ship’s computers allowed for much of the navigation, but due to the loss of the Service Module as an electrical power source, even backup navigation and targeting functions were unavailable. The Lander’s limited battery power required the shutting down of its guidance computer. The astronauts also needed to use an on-board sextant to confirm their location by sighting-in the stars, similar to how ancient sailors navigated. “There are thirty-seven stars – and one is the sun,” said Apollo engineer Jerry Woodfill, “that provided an accurate way of aligning the spacecraft’s computer platform to allow the astronauts to steer their way through the heavens.”

But the explosion of the tank had enshrouded the Apollo 13 spacecraft with debris. Commander Jim Lovell and his crew couldn’t discern the stars from the particles that glimmered in the sunlight. “The situation was, without the ability to see the stars, you couldn’t navigate,” Woodfill said.

But NASA had a backup navigation plan, thanks to an insightful NASA contractor employee. This novel way of navigating had only been tried once before in space. And coincidentally, the astronaut who used it was Jim Lovell, during his previous flight — Apollo 8 — which orbited the Moon in December of 1968.

An employee of TRW – which was the contractor for many of the navigational systems and procedures for NASA — thought of an unusual backup navigation plan one day. “This fellow is a friend and neighbor of mine,” said Woodfill, “and by his account of the story to me, he said that a thought came to him one day about Apollo astronauts using stars to navigate. What if the stars couldn’t be seen? Now, that was highly unlikely, as there are no clouds, fog, or smoke to conceal stars from viewing by astronauts. But, nevertheless, the thought simply wouldn’t cease. Soon a follow-up idea came to mind. Why not use the Earth’s terminator?”

The nominal flight plan for a mission to the Moon. Credit: Apollo 13 report.

The terminator is the line which delineates between night and day on Earth; where the Sun is shining and where it is dark.

Woodfill’s friend figured out the geometry and wrote a computer program to validate the idea. He submitted the proposal to the navigation board, which approved the technique so that it was entered into the computers in the Mission Control Center.

Through unusual, and what could be called happenstance circumstances, Lovell experimented with the backup plan during Apollo 8.

Lovell served as navigator for the first manned mission to orbit the Moon. He made a star sighting in preparation for the return to Earth, and entered the coordinates into the Apollo spacecraft’s primitive computer using the “DSKY” (display and keyboard). Instead of pressing the ENTR (enter) key, he inadvertently pressed the adjacent CLR (clear) key erasing the entire navigational alignment.

“Lovell consulted with Mission Control whether to repeat the sextant star sighting,” Woodfill said, “and someone realized this would be an opportunity to test the backup ‘seat of the pants’ means of navigating using the Earth’s terminator. And it worked! But then everyone forgot about it, until…guess when?”

Apollo 13's view of the Moon. Credit: NASA

Initially, the Apollo 13 crew was able to use the Sun as a “marker” to help in guiding the spacecraft to confirm they were on the right path, and were able to fire the LM engines for course corrections using the transferred guidance platform from the Command Module.

But as Apollo 13 headed back to Earth, the Reentry (RETRO) and Guidance, Navigation and Control (GNC) officers looking at the trajectory analysis noticed the spacecraft was coming in too “shallow,” that is, Apollo 13 was headed to skip off the atmosphere and out into space forever. Something seemed to be “blowing” the spacecraft off course. Later, it was discovered that cooling vapor from the lander was responsible. Since no lander had been present for previous missions on a return trip from the Moon, such a mysterious “wind” had never been encountered prior to Earth re-entry.

Another burn was needed, but no help from the guidance system would be available, as powering the lander’s guidance system, its gyros, the computer, etc. would use too much electrical power.

Here’s where the backup navigation approach that Lovell experimented with on Apollo 8 came to the rescue.

“If a ‘dead-reckoning’ approach could be used, no electricity would be needed,” said Woodfill. “Simply point the vehicle correctly, start the engine and stop it based on Mission Control’s prescribed time for its operation.” Lovell eyed up the Earth’s terminator line and controlled the “yaw” of the spacecraft, Haise controlled the “pitch” and Swigert timed it with his accurate Omega Speedmaster watch.

Graphics from the Apollo 13 report on using Earth's terminator for navigation.

The Navigation report for Apollo 13 describes it this way:

“The cusps of the Earth terminator were placed on the Y axis of the COAS. The illuminated part of the Earth was placed at the top of the reticle. Pitch attitude was achieved by placing the Sun in the upper portion of the AOT (see below). This procedure aimed the LM +Z axis at the Earth and aligned the LM +X axis retrograde along the local horizontal. An AGS body axis alignment was performed, followed by transitioning the AGS to the automatic attitude hold mode. A maneuver to burn attitude was performed, followed by another body axis alignment.”

Navigation graphics from the Apollo 13 report.

Woodfill said he enjoyed Hollywood’s re-enactment of the procedure in the “Apollo 13” movie. Though the spacecraft gyrations about the heavens are wholly exaggerated, the scene where Tom Hanks, Bill Paxton, and Kevin Bacon set-up and execute the terminator burn is generally accurate.

Suffice to say, the procedure worked for Hollywood dramatics, but more importantly, it worked to save the lives of Lovell, Haise and Swigert.

Tomorrow, Part 6: Fire

Other 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.

13 Things That Saved Apollo 13, Part 3: Charlie Duke’s Measles

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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.

Just 72 hours before the scheduled launch of Apollo 13, Ken Mattingly was removed from the mission and replaced by Jack Swigert from the back-up crew as Command Module Pilot. Charlie Duke, also from the back-up crew caught the measles from one of his children, and exposed Mattingly — the only other member of either the prime or back-up crews who were not immune to the disease. If Mattingly were to come down with the measles, he might contract it while alone in the Command Module while Jim Lovell and Fred Haise were walking on the Moon.

“I think Charlie Duke’s measles contributed to the rescue,” said NASA engineer Jerry Woodfill, who has come up with “13 Things That Saved Apollo 13.” “This is one that probably everyone disagrees with me, but it seems like the astronauts on board were perfect to deal with what happened on the Apollo 13 mission.”

Woodfill says his conviction in no way denigrates the abilities of Ken Mattingly. “Ken was a wonderful crew member,” Woodfill said, “and he is a very detailed guy who helped with the rescue of Apollo 13 in a magnificent way. In the movie, Apollo 13, they capture the essence of how he is an ‘engineer’s engineer’.”

Astronaut Charlie Duke. Credit: NASA

Although, ironically Mattingly and Duke flew together later on the Apollo 16 mission, were it not for Charlie Duke’s measles, Woodfill said that Swigert’s special talents for an Apollo 13-type mission would not have been present.

Jack Swigert. Credit: NASA

First of all, his physique was better suited to the harsh conditions he experienced in the inoperable Command Module, where he was positioned for most of the flight. Woodfill said that likely, Swigert’s brawn as a former University of Colorado varsity football player better served him to withstand the cold conditions and endure the small amounts of water that the astronauts had to ration among themselves.

Water was one of the main consumables – even more than oxygen – of which the crew barely had enough.

“Mattingly and Haise had about the same build,” said Woodfill, “which was not as robust a build as Swigert and Lovell. Haise ended up with a urinary tract infection because of not getting enough water.”

But more importantly were Swigert’s familiarity with the Command Module and his “precise” personality.

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

“Among the nearly thirty Apollo astronauts, Jack Swigert had the best knowledge of Command Module malfunction procedures,” said Woodfill. “Some have said that Jack had practically written the malfunction procedures for the Command Module. So, he was the most conversant astronaut for any malfunction that occurred in the CSM.”

Swigert had to quickly and accurately write down the procedure to transfer the guidance parameters from the CSM computers to the Lunar module computers. And the procedure for the reentry of the crew to Earth’s atmosphere had to be re-written, with Mission Control calling up to the crew with hundreds of changes to the original plan. “The team on the ground had to recreate a checklist and a procedural ‘cookbook’ that would normally take three months to create, and they had to do it in just days. Jack had to be accurate when he wrote down these procedures. And the communication system wasn’t always the best – it was sometimes garbled or couldn’t be heard very well. While all the astronauts had to have orderly minds, Jack Swigert was a man of extreme order.”

Woodfill said an account from Swigert’s sister bears out that fact. She at one time asked her brother Jack to put away cans of frozen orange juice and lemon juice in her freezer. When she looked in her freezer later, all the lemon juice cans were lined up in orderly fashion, with the orange juice cans neatly lined up in an adjacent row. Later, she asked her brother why he had neatly lined all the lemon cans in a row then a row of orange juice cans, and according to Woodfill, Swigert answered, “Because “L” comes before “O” in the alphabet.”

“The truth is, Swigert was gifted with a respect for extreme order and precision, and he was onboard for just that reason,” said Woodfill. “Every one of the steps in the rescue checklist had to be ‘in the right order’.”

Fred Haise, in 1966. Credit: NASA

And, equally important, said Woodfill, was the talent Haise brought to recording and rewriting operational procedures. “Fred had been a newspaper stringer for a small newspaper in Mississippi in his youth, taking notes and editing them for his local Mississippi paper’s stories. Utmost among reporters is accuracy in quoting sources. Those transmitted words from mission control had to be flawlessly transcribed if the crew was to survive, and Fred and Jack did an amazing job.

Remarkably, said Woodfill, each man’s talents specifically served the unique need. “Each man exhibited exceptional accuracy in adverse surroundings,” he said. “The lander was noisy, the audio sometimes fuzzy, movement unpredictable, temperatures cold, sleep scarce, and fatigue always present.”

Of course, those familiar with the Apollo 13 story know that Ken Mattingly never got the measles. But the role he played in getting the astronauts back home safely can’t be overestimated.

“Call it luck, call it circumstance,” said Woodfill, “but because of Charlie Duke’s measles the men on board Apollo 13 — and back on the ground — were perfect for the situation they encountered.”

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

Introduction

Part 1: Timing

Part 2: The Hatch That Wouldn’t Close

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.