13 Minutes to the Moon

Last year, before the 50th anniversary, BBC had aired a very informative and nicely produced podcast about the first landing of the Moon by Apollo 11 in July 1969. I have only just recently discovered the podcast, which is titled 13 minutes to the Moon.

The programme covers the whole development process, and of course, the final descent of the Lunar Module to the Moon’s surface – the 13 minutes. There’s a lot of background information on the people, technology, and the related challenges. An important topic is the control and guidance computer, including the famous 1202 and 1201 alarms during the descent and landing phase, the 13 minutes from separating the Lunar Module from the Control and Service Module until the touchdown on the Moon.

It seems I cannot get enough of this. Is there a Moon Landing Anonymous?! It’s probably a lot of engineer’s nostalgia, but then again, the Apollo program – and the predecessors Mercury and Gemini – was simply quite a science and engineering achievement, a victory of human ingenuity, dedication, and systematic work, also overcoming the many differences in viewpoints and cultures of groups of engineers and pilots, resulting in a well-functioning system nonetheless. This seems so far away – and ahead – of what would be possible in today’s political and economical landscape. You know, investment in real achievements, not social networks. I am aware this is an oversimplification, but I think the overall picture it nonetheless holds some truth if you squint a bit. Also, note that I am not saying this kind of endeavour should today be directed towards more space exploration, say, sending people to Mars. If the same will, focus, resources, and cooperation were applied to climate change and alternative energy, just to name an example, try to imagine what would be in reach within just ten years, ie. about the same time frame Kennedy set as objective for the moon landing.

But I digress. Back on topic. I admire the clever use of the available and nascent technologies, as well as engineering and science, where simplicity is a plus, with the only complexity allowed is driven by the needs of the problem space, and not the nice-to-haves of the solution domain. The first ever flying apparatus flown by a computer, autonomously, but with a fluid boundary as regards the separation of responsibilities between the astronauts and the guidance system once in space, based on the experience with the Gemini and the Mercury programs, as well as the X-15 experimental aircraft.

A few tidbits:

  • How do you even navigate in deep space, a featureless void? By inertial navigation. If you start from a known location, with a known velocity and direction, you can determine the current position by continuously measuring the acceleration (amount and direction) and time. But as any engineer would comment immediately, there are errors of measurements, and limits of precision in calculations, so how do you make sure where you actually are on a journey of close to 400,000 km? By checking your position using known positions of stars. That’s also how you calibrated and aligned the navigation system of the Lunar Module when you powered and started it up, close to the Moon.

  • The Apollo guidance and navigation system – gyroscopic and acceleration sensors, computer, programs, actuators, wiring – was developed at MIT’s Instrumentation Lab. It was based on navigation systems originally created for ballistic nuclear missiles fired from submarines (the Polaris project), as well as Mercury and Gemini systems.

  • Designing and building the guidance and navigation system was the first contract signed for the Apollo program. It was ten pages long. The needed programs were mentioned in a sentence or two. The concept of software as even being a thing was not recognised and developed at all yet. Margaret Hamilton, head of the development of all in-flight software, is credited with coining the term software engineering.

  • Apollo 8 was the first spacecraft ever that went out of Earth’s orbit into deep space, into the first lunar orbit. No-one had done that before, “manned” space flight was all close to Earth. I had never thought about that, but Apollo 17 in 1972 was the last space mission when humans ventured into deep space. Since then, human-staffed spacecraft and stations remained in Earth’s orbit. Leaving that orbit is a completely different endeavour.

  • In the beginning of 1968, the Saturn 5 rocket was far from ready, with lots of flaws and issues. Engineering and building the Lunar Module had fallen badly behind schedule. So it was decided to get the Saturn 5 up and running, and leave the Lunar Module behind for Apollo 8. The objective then was reduced – or focused – to just get Apollo 8 into lunar orbit, and back again, before the end of 1968 – just about six months before the first landing on the moon. That’s some crazy schedule.

  • Apollo 8 had to do its first-ever positional burn to enter lunar orbit while on the dark side of the moon, ie. without any contact to Mission Control. Quite some wait for the people down there until the signal was acquired again, and they knew if their calculations had been correct, and the technology had worked.

  • The Apollo 8 astronauts were the first humans to ever see the dark side of the Moon. They also saw the first ever Earth rise.

  • The Lunar Module was going too fast across the lunar surface during its powered descent. Later it was determined that the crew had not fully depressurised the tunnel between the Lunar Module and the Command Module before releasing the latches, and the residual pressure gave the Lunar Module a small jolt when separated, which resulted in some additional horizontal speed. This lead to a landing site further down the path, compared to what was planned, in a more rocky place, so that Armstrong had to find an appropriate spot in the last seconds before touchdown. This “pressure technique” was used later with Apollo 13 to separate the Lunar Module from the Command Module shortly before the latter’s fiery descent through Earth’s atmosphere.

  • The main rocket engine on the Lunar Module was the first type ever designed whose thrust could be regulated proportionally. Usual rocket engines were either on with full thrust, or off, nothing in between. To land on the Moon, this ability was crucial, of course.

  • Right when the time had come to initiate the powered descent of the Lunar Module towards the Moon, all communications between the space craft and Mission Control simply didn’t work, including the data links for the telemetry. Mission Control gave the Go to the Lunar Module relayed via the Command Module, and not based on actual data, but the last known reliable data set.

  • Apart from concerns about the safety of the astronauts, and the success of the mission, a missing data downlink was an issue as without the data a post-mortem analysis in case of a crash would not be possible – the engineers wouldn’t know why and how the Lunar Module crashed, hence inhibiting the required improvements for future attempts.

  • To measure the fuel level in the tanks, the Lunar Module had to fire its main rocket engine at 10% capacity for a short time, creating some artificial gravity and thus pressing the fuel towards the bottom of the tanks, thusly enabling the sensors to actually measure the available fuel. Before that initial small firing, they didn’t know the fuel levels, apart from the filling data before liftoff.

13 Minutes to the Moon
  • Since I was a kid, I had always liked how the Lunar Module looked. Spidery, mysterious, with its insulating wrappings of foil around parts of the body. Back then, many didn’t. Aeronautics engineers – and the public – were used to slipstreamed shapes suited to fly in air. The LM engineers at Grumman had to learn that out in space, close to the moon, for a vehicle that would never return to Earth, the shape simply didn’t matter. It was then all about reducing weight and optimising available space inside. There were no seats. The walls separating the astronauts from space could have been pierced with a sharp pen. OK, for the computer, which flew the Lunar Module, the shape did matter, to calculate the thrust of the many small jets to execute positional manoeuvres. Or at least the centre of mass defined by the shape and construction.

  • The podcast’s title music is by Hans Zimmer. I guess you need to be the BBC to pull that one off.

Ah, yes, there’s an added bonus to enjoy some Real English language, at least by the BCC staff. The interviewees mostly speak American English, obviously, but that cannot be helped, I guess. Just kidding. It’s highly interesting to listen to the first hand testimony of people that were actually there.

PS: There’s a second season of the podcast now, which covers the failed mission of Apollo 13. If you like the movie, don’t listen to the podcast. The movie is stale and somewhat silly after you do. The podcast enthralled me way more than the movie – I have checked after listening to the whole season. I don’t think I’ll ever watch that movie again.