Monday, May 11, 2015

Hanging Out With Someone Who Walked On The Moon

Lunar dune buggy rides, piloting the most powerful machine made by humankind, stuck thrusters, landing, eating, sleeping, and working on the moon. It does not get any more exciting than the Apollo program! I was recently given the opportunity to sit in on the MIT course, Engineering Apollo: the Moon Project as a Complex System where I met David Scott who landed on the moon as commander of Apollo 15. I not only sat in on a long Q and A session I also was able to spend time with David after class. It is not every day you that you meet someone who has landed on the moon, below are my notes from this experience.

ap15-KSC-71PC-605HR as15_hfd_4 Dave_Scott_Apollo_15_CDR GL Charvat and David Scott


David Scott flew on Gemini 8 with Neil Armstrong during the stuck thruster incident. He was the command module pilot in Apollo 9 which was a test flight of the complete Apollo spacecraft system. He landed on the moon as commander of Apollo 15, which was the first mission to carry the lunar rover.


David lives up to his legendary status as an Apollo astronaut while also being very approachable. His sense of humor had the class in an uproar on many occasions. The MIT students were asking very specific technical questions. David's deep understanding of everything about the Apollo system was impressive, not a question couldn't be answered in detail and with additional nuance that may not even be in the history books yet. I'm sure he would have drawn block diagrams and schematics if we had asked.

Gemini 8 and the stuck thruster

You've probably heard of the stuck thruster incident during Gemini 8. One of the maneuvering thrusters stuck-open, causing the spacecraft to rotate faster and faster and faster again. So fast that David and Neil Armstrong were starting to black out. They survived it by shutting down the one thruster system and using the reentry thrusters to stop the spin.

The mission had to be ended sooner than expected. Re-entry began over Africa which was not the original plan. During re-entry they passed over the Himalayas and soon thereafter landed the south China sea. David told us that the view of the Himalayas was absolutely amazing.

David and Neil were not totally confident that they had made it over ocean which necessary for a normal landing. Fortunately Neil was able to confirm this with his mirror looking out the window, seeing ocean through the window. Chutes opened and there was no need to eject over land!

Photos from the Gemini 8 mission. s66-25782 s66-18602 s66-24482

Quality of Apollo simulations

David told us that the simulations were remarkably accurate. His recollection was the only difference between the simulation and being on the moon was the fact that you were on the moon. Quite an endorsement of the Apollo simulators.

Apollo mission simulator.Apollo mission simulator.

David is a big fan of simulations. He told us that when traveling into space you want to simulate as much as possible while on the ground so that you get to know the systems and your fellow crew members. Apollo went so far as to simulate parts of the mission with the CM and LM inside of a huge vacuum chamber.

The simulators were hybrid digital and analog systems. David told us that the people running the simulations were trying to kill them by causing a large plurality of alarms, false alarms, systems failures, partial failures, and so on. It required an engineer's mind to solve the puzzle presented by almost any alarm because alarms were not always what they seemed. Correctly solving this conundrum of machine feedback was a matter of life and death during a real mission.

David had kind words to say about the controversial LM flight trainer. This is a vehicle flown in earth's atmosphere in order to train the astronauts; the same one that crashed and nearly killed Neil Armstrong. Without this the moon landing would have been much more dangerous.

Abort control on takeoff

There is an abort control on the left side of the left seat (pilot's seat) of the command module. It's a very interesting thing, if you are at the start of your flight rocketing up with the whole stack (F1 engines going) and you rotate it right then the entire stack is now under manual control where the pilot in the left seat is manually flying the entire rocket.

This feature was never used but it was tested in simulation many times. Apparently under manual control you had to keep a pair of crossed needles lined-up on one of the instruments on the front panel while riding the most powerful machine ever made by humankind. It sounds extremely challenging, right?


If you turned the abort handle left then the escape rocket at the top of the CM would fire, subjecting the crew to 14G's. Nobody wanted to rotate it to the left because, as you can imagine, 14G would not feel too good and aside from personal comfort the crews were extremely motivated to make things work no matter what happened.

Even when Apollo 12 was hit by lightning, causing the electrical systems to go crazy as it was clawing its way up into the atmosphere, the abort control was not touched. They still went for it.

Apollo 15 landing

David and James Irwin landed between the two largest mountains on the moon at a steep descent angle so that they could safely 'thread the needle' between the two mountains. David admits flying the LM is a challenge, but even more so with the added weight of the J mission which includd the rover, tools, experiments. This weight penalty was further compounded by the steep descent angle caused by the mountainous approach.

Why manual control on final phase of descent

David talked about how the LM could land on the moon entirely by itself but the last portion of the landing was always taken over by manual control. This was not macho fighter pilots showing their bravado at the controls, instead it was a safety concern. There was not much time to react and trouble-shoot if an alarm light occurred on the final phase of descent. By contrast if a pilot were in control he would feel the spacecraft do something different if there was a problem and be able to naturally compensate. This is why the last phase of landing was achieved with manual control.


Don Eyles, who was key to architecting the LM's software and specifically the landing programs, was sitting next to me in the audience and took this all very well. Later that evening I was able to chat with Don, he is also extremely interesting and a super-nice guy, he explained to me that the entire Apollo computer was made from NOR gates and showed me one of the logic cards.

Living on the moon

During Apollo 15 David and James had to live and work on the moon for 3 days which meant that they had to develop procedures to live, eat, and sleep on board the LM. Not a trivial task.

Sleeping in a space suit was not comfortable, resulting in little sleep. Space suits had to come off every evening. Taking off the suits and not getting lunar dust all over everything in the LM was tough, apparently this was done in a large bag of sorts to at least minimize it. Hammocks were setup in the LM and the guys slept in their underwear.

They researched circadian rhythm, which was not well known at the time. Moon time became Huston time for the purposes of maintaining their sleep-wake cycles.

When examining the space suits on board the LM, they found that the caked on moon dust was surprisingly abrasive. This raised concerns about the integrity of the suits' air-tight fittings.

The lunar rover, dune buggy on the moon!

As if you had any doubts, but David confirms the lunar rover was really fun to drive. The vehicle had a wide wheel base, a low center of gravity, and each wheel had its own motor. But there was one occasion that caused a stir when the rover nearly slid down a mountain.

Preventing the lunar rover from sliding down a mountain.Preventing the lunar rover from sliding down a mountain.

David and James noticed a green-colored boulder on the side of a fairly steep mountain so they cruised to it in the rover. In 1/6 gravity it wasn't long before the rover started sliding sideways down the mountain! James had to catch it with his own two hands. Mission control did not have a live video feed during this time so the guys kept it on the DL.

This is the photo of the green rock with the rover in the background, one of its wheels up in the air and James is literally holding the vehicle up, keeping the rover from sliding further down the mountain.

Feather and hammer gravity demonstration

Which falls faster in a vacuum, a feather or a hammer? David wanted to test-out the feather and hammer drop right away because there was a risk that static electricity could cause the feather not to drop. For this reason he brought two feathers with him, one for the video recorded demo and the other to test it first. Fortunately the demo was a huge success. We're greatly amused that David's reaction to the successful experiment is "How 'bout that?"!

NASA Culture during Apollo

Being involved in startups I've always been curious as to what the cultures are like in other fast organizations. Apollo was fast, in about 7 years they went from Gemini missions to walking on the moon with an organization that included nearly 400,000 people (of course this is a high estimate, including the subcontractors and so-forth).

How did they do it? I asked David this question specifically.

The astronauts were closely involved in development. David was involved in the development of guidance and navigation. He also developed the layout for the panels on both the command module and the LM from a pilot's perspective for ease of use.

For example the Friday Tindall meetings involved representatives from each major subsystems. The objective of the meeting was to solve problems and make decisions affecting all of the major systems. Engineers in attendance were empowered to make decisions for their respective teams and decisions were communicated the program via Tindall memos.

"Well, I just got back from MIT with my weekly quota of new ulcers, which I thought might interest you." – Bill Tindall, June 13, 1966.

These memos were funny to read but also key in keeping everyone on the same page. Of course some decisions were overturned when more info was available the following week, but this was the synchronization pulse.

In summary, meetings were for making decisions and every engineer had a voice, listened to no matter what level.

David also pointed out that generally speaking, Apollo engineers were of the can-do variety. They may have never done the thing that was being asked of them but they were willing to give it a try, make mistakes, and learn from those mistakes.

Read the book and Prof. Mindell

Look, you may not ever be faced with the amazing opportunity to hang out with an astronaut who has been to the moon. But the astronauts from all of the various missions have been great at sharing their experiences.

Credit for this experience belongs to Prof. Mindell, who is the Frances and David Dibner Professor of History of Engineering and Manufacturing (STS) at MIT. Prof. Mindell created the course and wrote the book Digital Apollo. This book is a must-read for those interested in the nuts and bolts of the guidance, navigation, and many other technical details of the Apollo system.

Prof. Mindel also wrote two other books that might be of interest to the Hackaday community:


We can learn a great deal from how the Apollo program accomplished its missions and should always take the opportunity to listen to those who worked on Apollo. If you've had the chance to meet someone having to do with the program please let us know about your experience in the comments below.

Author Bio
Gregory L. Charvat is a huge fan of manned space flight, is the author of Small and Short-Range Radar Systems, co-founder of Hyperfine Research Inc., Butterfly Network Inc. (both of which are 4catalyzer companies), visiting research scientist at Camera Culture Group Massachusetts Institute of Technology Media Lab, editor of the Gregory L. Charvat Series on Practical Approaches to Electrical Engineering, and guest commentator on CNN, CBS, Sky News, and others. He was a technical staff member at MIT Lincoln Laboratory where his work on through-wall radar won best paper at the 2010 MSS Tri-Services Radar Symposium and is an MIT Office of the Provost 2011 research highlight. He has taught short radar courses at MIT where his Build a Small Radar course was the top-ranked MIT professional education course in 2011 and has become widely adopted by other universities, laboratories, and private organizations. Starting at an Early Age, Greg developed numerous radar systems, rail SAR imaging sensors, phased array radar systems; holds several patents; and has developed many other sensors and radio and audio equipment. He has authored numerous publications and has received press for his work. Greg earned a Ph.D in electrical engineering in 2007, MSEE in 2003, and BSEE in 2002 from Michigan State University, and is a senior member of the IEEE where he served on the steering committee for the 2010, 2013, and 2016 IEEE International Symposium on Phased Array Systems and Technology and chaired the IEEE AP-S Boston Chapter from 2010-2011.

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