Apollo Image Question

There is a question about Apollo 13 images of the LM when they had seperated, the legs of the LM are extended.

www.lpi.usra.edu...

That isn't really a big issue, except in the flight plan the legs are usually extended during station keeping after seperation from the CSM in lunar orbit.

And since they never achieved Lunar orbit, I was wondering the reasons why they'd waste power on extending the legs, plus the issue that the legs are extended by Pyro-intitators.

Now I could come up with a few reasons, but since I am unable to find the answers I thought maybe someone could lend a point a view.

My thoughts are the decent engine would not fire for the PC+2 burn needed to place the CSM stack back on a free-return trajectory, unless the legs are extended and locked.


Well does anyone know?

reply to post by theability


'theability' ---

I think you answered it there. The descent engine needed to have an unobstructed thrust path, in order to use it effectively.

[edit on 14 April 2010 by weedwhacker]

reply to post by weedwhacker


I was wondering if this was correct, but I haven't been able to confirm this, leading me to ask if anyone knew where I could locate data supoort this theory.

reply to post by theability


Found this, in search for "Apollo 13 timeline":

Midcourse correction ignition to free-return trajectory (LM DPS).
061:29:43.49 (GET)
08:42:43 (GMT)
14 Apr 1970

Midcourse correction cutoff.
061:30:17.72 (GET)
08:43:17 (GMT)
14 Apr 1970

LM systems powered down.
062:50 (GET)
10:03 (GMT)
14 Apr 1970

Lunar occultation entered.
077:08:35 (GET)
00:21:35 (GMT)
15 Apr 1970

Lunar occultation exited.
077:33:10 (GET)
00:46:10 (GMT)
15 Apr 1970

S-IVB impact on lunar surface.
077:56:40.0 (GET)
01:09:40 (GMT)
15 Apr 1970

LM systems powered up.
078:00 (GET)
01:13 (GMT)
15 Apr 1970

Abort guidance system to primary guidance system aligned.
078:10 (GET)
01:23 (GMT)
15 Apr 1970

Transearth injection ignition (LM DPS).
079:27:38.95 (GET)
02:40:39 (GMT)
15 Apr 1970

Transearth injection cutoff.
079:32:02.77 (GET)
02:45:02 (GMT)
15 Apr 1970

LM systems powered down.
082:10 (GET)
05:23 (GMT)
15 Apr 1970

history.nasa.gov...

Seems pretty conclusive to me, since they had to fire the LM DPS, and the gear legs would be in the way, possibly alter the thrust component, if retracted. Better to extend them, to be safe.

Maybe can hunt through these references, too...there looks like a lot of reading...

history.nasa.gov...



[edit on 14 April 2010 by weedwhacker]

reply to post by theability


Wow Awesome content, thanks I will indulge in reading them!

Thanks Weedwacker!

Well nothing like finding an answer.

From what I have read, the LM legs had to be extended before th PGNS would allow the DPS logic to initialize.

Obviosuly that would be a bad day if that didn't happen!

COOL!