I've been playing around with lunar launch delta-v requirements, and it seems that you can get a lot of bang for your buck if you launch "sideways" so to speak. Well, in the absence of atmosphere obviously... But I'd see that as a huge safety hazard to the crew if a certain threshold was exceeded. I wouldn't want to be flying 100 meters above the surface of the moon flying at 100m/s.

Does anyone have a diagram of the LEM ascent trajectory that illustrates the maneuver used?


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The mission planning document has such a diagram.

The TL;DR: ascend straight up for 8-10 seconds, then execute a gradual tipover from vertical to horizontal over the remainder of the ascent, approximating a linear-tangent steering law.

The expected trajectory parameters are given in the LM timeline documents such as this one for Apollo 12 (the page labeled FLIGHT PLAN ASCENT MONITOR); I haven't checked to see how they compare to the linear tangent law results.

  • $\begingroup$ The angle of the flight path! Right, that's the word I was looking for. Thanks for the linked documentation. $\endgroup$ Commented Oct 9, 2018 at 3:02
  • $\begingroup$ I'm still trying to find an authoritative description of the actual guidance program, i.e. whether it was computing arctangents or just working through a table. Might have to get one of our AGC program analysts involved... $\endgroup$ Commented Oct 9, 2018 at 3:05
  • $\begingroup$ If you'd like, feel free, this more than answers the intended scope of the question though; I'd say this is a duplicate unless you'd like me to edit it to include more about the ascent guidance program (which I absolutely would love to see!) If you do talk to someone I'll make appropriate edits to conform the topic more towards the guidance methodologies and choices made by the computer $\endgroup$ Commented Oct 9, 2018 at 3:26
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    $\begingroup$ Toss-up whether it's dupe or not; I'm going to write a separate question asking about the implementation details. $\endgroup$ Commented Oct 9, 2018 at 3:27
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    $\begingroup$ That's what I was thinking, I'll accept that and vote to close, let everyone else decide. Link that question though, I'll +1 and follow it :). $\endgroup$ Commented Oct 9, 2018 at 3:32

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