Wednesday, December 26, 2007
Flying Apollo 12
I was reading about Apollo 12 in A Man on the Moon, and it reminded me that this was one of my favorite Apollo missions, with a fun-loving all-Navy crew of Pete Conrad, Al Bean, and Dick Gordon. It took place in November 1969, just a few short months after Apollo 11, but in the Apollo era, they learned fast. Aside from a lightning strike that briefly knocked out their electrical systems moments after launch (fortunately not affecting the Saturn V guidance systems), it was pretty much "nominal" all the way. It was also the last Moon landing mission that I paid much attention to at the time, sad to say. Apollo 13 was April 1970 - I followed the crisis like everyone else, but of course they didn't land on the Moon. Then in August 1970, I went off to college, and for the next few years, Moon landings were not my top priority (neither were academics at first, but that's another story). Of course in this respect I was not that different from the public at large - Apollos 14, 15, 16, and 17 each did progressively more amazing things, but no one paid much attention.
Reading again about Pete Conrad's pinpoint landing (within walking distance of the Surveyor III spacecraft), I wanted to experience it for myself. So I fired up Orbiter and AMSO (Apollo Mission Simulator for Orbiter) to simulate the Apollo 12 landing. First I checked the AMSO installation and found that while there was a suitably modeled landing site for Apollo 12, the Surveyor spacecraft was not included. I then searched Orbit Hangar for a Surveyor spacecraft add-on and found one (created by Jim Williams). I installed that add-on in my AMSO directory and did a little scenario editing to place the Surveyor on the surface within the Apollo 12 landing area (the base in AMSO is called Procellarum). I didn't worry about the exact position, but I placed it near the edge of the large crater that was dubbed "Surveyor Crater" (the largest of a cluster of craters that looked something like a snowman). It's not exactly on the surface - for reasons I don't fully understand, it's floating about a meter above the Apollo 12 base texture - oh well. I tried to hide this in my screen shots.
AMSO is not a "system simulation" as the NASSP add-on is for selected areas. In NASSP you find fairly detailed instrument panels and even virtual cockpits, allowing (or requiring) you to click sequences of switches similar to what the astronauts did for various operations. This is impressive and cool but also somewhat impractical. AMSO accurately simulates the many steps and actions of the Apollo missions, but the interface is reduced to a few keys and simple menu prompts in the lower left corner of the screen, and there is a lot of available autopilot help, although everything can be done manually if you are so inclined (and skilled).
For the Apollo 12 landing, I chose a supplied LM descent scenario, which starts with the LM already in its low-pass orbit, a few minutes before PDI (powered descent initiation). Using the K key and arrow keys, I found I was about 500 seconds from PDI (braking with the LM's descent engine). I used 10x time acceleration to get to the good stuff, allowing the autopilot to fly just as in the real thing. Once the LM pitched up to its vertical "hovering" position and the landing site was visible, the computer switched to a mode where the landing point could be shifted with the arrow keys, similar to what Conrad did with a couple of toggle switches in the real LM. In this way I could avoid landing in the large crater. I spotted the shiny pixels of the Surveyor from a couple of kilometers out, and in a few minutes, the autopilot had landed (manual control for the final minutes of the landing is possible just as in the real thing, but only with a joystick, and I don't have one hooked up for this computer).
I ended up within a few hundred meters of the Surveyor, and I launched my two astronauts on their first EVA. I didn't first read the EVA instructions so I didn't deploy an antenna, plant the flag, and search for rock samples, though this is all implemented in AMSO! I just had my virtual Pete and Al hop around for a bit while I took some pictures. I was impressed that with the low Sun angle, even the dark color of the surface seems to match the character of the real site as shown in many Apollo 12 photos (Alan Bean accidentally pointed their color video camera at the Sun and fried its sensors, so there was no EVA video from Apollo 12, alas).
AMSO is great and with all the automation and supplied scenarios, it's possible to experience the complexity and even the beauty of the Apollo missions without being an Orbiter "ace," or to fly a complete end-to-end mission if you are. More pix on Flickr. See also the impressive AMSO Gallery at the primary author's web site.
N.B. From the gallery and some further tests I found that Surveyor 3 actually is part of the Apollo 12 landing site in AMSO, but it does not appear until EVA #2, when retrieving a piece of the spacecraft is part of your EVA goals, as indeed it was for Pete and Al. Lunar surface EVA's in AMSO have a simple game-like aspect to them - you need to go to one or more EVA sites in a prescribed order and retrieve several specific rock samples before you can complete that EVA and go on to the next one. You can even run out of oxygen if you don't keep an eye on your consumables and return your crew to the LM in time. This is all described in a supplied file (EVA.DOC) that even includes maps of the landing areas and EVA routes. Whoa.