View Full Version : question re: LM attitude during descent

2007-Jul-14, 06:03 PM
So I'm curious about the various attitude positions of the LM during descent. I'm asking because watching fictitious depictions (e.g., "From the Earth to the Moon") always gets my mind wondering.

In "Spider" (in "From the Earth to the Moon" shows), the Apollo 10 LM is briefly shown over the moon, completely upright, but having a [seemingly] high horizontal velocity. Such a depiction makes me wonder how it is supposed to decrease its horizontal velocity. But of course, that was Apollo 10; it never needed to land, so perhaps said depiction was accurate.

Anyway, all I really know is that the LM starts powered descent in a horizontal position (with a really high horizontal velocity.) And by landing, it is [obviously] vertical (with virtually a zero horizontal velocity.) Are there any detailed timelines available of the LM's powered descent along with its attitude at any given time?


2007-Jul-14, 07:17 PM
I didn't read this really closely, but it looks like it might cover what you are looking for. It does have a diagram showing DOI and PDI with the LM initial attitude at DOI.


2007-Jul-14, 08:08 PM
'Spider' was the Apollo 9 LM. Apollo 10 LM was Snoopy. Are you sure Snoopy was in powered descent in the shot you mention? It could have just been coasting in the descent orbit. The flight profile up until Apollo 14 was that the LM would separate from the CSM in lunar parking orbit, perform descent orbit insertion using the descent engine and lower the pericynthion to something like 2000ft. At pericynthion would be powered descent initiation and the LM would fire retrograde to power out of orbit and into approach to the surface. For most of powered descent, the LM will be oriented arse into motion as it performing a braking burn. Only when it reaches the approach phase (breaking phase, approach phase, landing phase iirc), would it pitch to orient arse down.

2007-Jul-14, 08:41 PM
... Are you sure Snoopy was in powered descent in the shot you mention? It could have just been coasting in the descent orbit ...
I'm sure it was the latter (I don't know all the technical details of Apollo.) In either case, in "From the Earth to the Moon," Snoopy was in "arse down" position with quite a high horizontal velocity. But it was just a movie. And thanks for the info. in your reply.