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I was looking at some diagrams for the Apollo spacecraft, which I found to be interesting. It's clear that there's two separate enclosures that astronauts could reside in (the lunar module and command module). However, there is a massive rocket nozzle in between each habitable enclosure. This leads me to a few related questions.

Where and what kind of design was in place to allow the astronauts to safely move from enclosure to enclosure? How did the astronauts traverse them? Were there any restrictions? What sort of precautions and safety mechanisms were in place to keep the astronauts safe when a lower section of the craft was discarded through the various stages?

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Ellesedil
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The launch escape system was jettisoned after launch. Here is a picture of it being tested:

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With the launch escape system out of the way, and the fairings released, the crew performed a transposition and docking maneuver on the way to the moon.

It was performed by the Command Module pilot (although, as a contingency, the Lunar Module pilot and commander were also trained to perform the maneuver), and involved separating the CSM from the S-IVB, pitching the CSM 180° and proceeding to dock with the Lunar Module, by inserting a probe at the top of the CSM into a drogue at the top of the Lunar Module. Then, the Apollo spacecraft stack would separate from the S-IVB, which would then either continue on to a heliocentric orbit or be deliberately steered into a crash landing on the Moon.

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Nathan Hughes
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Erik
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  • Cool. Then they'd just proceed through the top of the command module into the lunar module? What about if they needed access to the launch escape system prior to jettisoning it? – Ellesedil Dec 08 '14 at 06:49
  • Yepper. All Intravehicular Activity (IVA) -- no spacewalks required. A tricky docking maneuver, but the stack is on a free return trajectory at that point anyway. So if something goes wrong you at least have that going for you. – Erik Dec 08 '14 at 06:51
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    The Launch Abort System (LAS) isn't habitable. It just yanks the command module off the top of the S-V stack if something goes wrong early in the flight. – Erik Dec 08 '14 at 06:52
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    Ah. So it's just essentially a rocket to provide thrust for the command module? Interesting. – Ellesedil Dec 08 '14 at 06:55
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    @Ellesedil Yup. Idea of LES is that its safer to be strapped to bottom of tiny flaming rocket than being stuck on top of much bigger exploding one. According to Wiki it was used only once for its intended task and although it worked crew was close to becoming marmalade (14-17g, ouch). – PTwr Dec 08 '14 at 10:44
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    The movie "Apollo 13" showed this maneuver very clearly. https://www.youtube.com/watch?v=Tefgq4q372Y CMP John Swigert performed it, though the docking probe scraped against the side of the drogue before securely docking to the LM. – The other other Alan Dec 08 '14 at 14:40
  • I clearly rememember reading about this docking maneuver in a child's pop-up book about Apollo, in the early 70s! Thanks for reminding me. – Ross Presser Dec 08 '14 at 16:01
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    @PTwr It should be noted that the only "in anger" use of a Launch Escape System was on a Soviet Soyuz launch. It was never used in the Apollo program, though it was tested on the unpiloted A-004. – pericynthion Dec 08 '14 at 19:16
  • For completeness' sake, it should be noted that the diagram showing the separation, transposition & docking is not to scale. I don't know the distances involved in actual Apollo missions off the top of my head, but I do remember that the Apollo 13 movie claims 100+ feet distance. You'd want enough separation to be able to safely and accurately line up, but not so much separation so as to use an excessive amount of fuel for lining up. It's not so much a matter of distance as it is a matter of the precise maneuvering needed to align with the quite small target area which is in a separate orbit. – user Dec 09 '14 at 15:26
  • @Erik perhaps worth explicit mention was the existence of hatches at the top of the lunar and command modules, which in the docked configuration formed a "tunnel" between the two craft. – Anthony X Mar 08 '15 at 15:03
  • @MichaelKjörling actually once you input the initial acceleration, you can keep the speed differential for as long as you want, and create as much separation as you want for free. – Antzi Sep 09 '16 at 16:15
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    @Antzi Late reply but in case anyone else reads along - the complication on longer distances is that you start to have to treat things more like orbital transfers and less point and shoot straight line travel. – Saiboogu Feb 16 '18 at 05:16
  • The Mercury Redstone 1 mission accidentally fires an LES after an engine ignition failure. No crew were on board. A fully powered and fueled rocket was left sitting on the pad while the LES took off like a bat outta hell. Mission control had no idea how to handle it and actually wanted to shoot at it with a rifle to attempt to perforate the fuel tanks. Somebody stopped them and made them simply wait for the batteries to die and the oxidizer to boil off. Still, ya gotta laugh at some of NASAs best and brightest going "well....... has anybody tried shooting at it?" – TCAT117 Feb 16 '18 at 18:30
  • @AFischbein, the Apollo 13 clip about docking and transfer is not available anymore at the link you provided. Can you suggest any more link? – Niranjan Dec 20 '18 at 05:10
  • @Niranjan , poorer quality, but all i could find for now https://www.youtube.com/watch?v=oHeGQjpVBPA – The other other Alan Dec 21 '18 at 13:23
  • Worth pointing out, I think, that way more docking and undocking of the CSM and LM was involved: it was not restricted to low Earth orbit as suggested above. In order for the LM to descend to the Moon's surface, the LM pilot had to perform an undocking manoeuvre in Lunar orbit; and on returning to the CSM, after the landing, the LM pilot then had to perform a docking with the CSM. Then, following the crew transfer from the LM to the CSM, a 4th manoeuvre (an undocking) was performed by the CSM pilot to separate it from the LM, as only the CSM returned to splash-down in the Pacific. – Ed999 Apr 17 '19 at 19:10
  • @user: There was a question asked and answered recently about the distance reached during translation and docking. Much smaller than I would have thought! – Fred Larson Nov 22 '21 at 19:01