Apollo Spacecraft Launch Adapter and S$B stability.

[sodengineer]

Hello Aerospace Engineers-
A discussion between some civil engineers the other day has prompted this question.

During the Apollo mission, during transposition and docking to remove the LM, what kept the S4B stable, especially if one of the panels hung up? As I understand it, the third stage is spent so it is a free body and Newton's law will apply. So, if one of the panels hung up or if they did not open perfectly, the whole assemblage would begin to rotate, wobble, etc.

The other, related question is related to the above and actually occurred on Apollo 14. If the CSM tapped the LM anywhere but exactly in the center of gravity, the same would occur, a slight drift, wobble, etc. How did it remain aligned so a second attempt at docking could be made?

No, I'm not working on a project, just idle curiosity from someone who admires your work.

 

[GregLocock]

Newton's laws always apply. Glad we've sorted that out. Second bit first, the docking system has a set of catches with some room for error, as I understand it, so even if they are slightly misaligned you still get a positive latch. If the CSM had just rammed the LM randomly, yes there would have been trouble. Relative velocities during docking are in the low inches per second realm, they aren't banging about like billiard balls.

I don't know what the game plan was in your first case - spacewalk?

Cheers

Greg Locock


New here? Try reading these, they might help FAQ731-376

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[WKTaylor]

FYI ONLY...

THE APOLLO 14 DOCKING ANOMALY

https://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19730010157.pdf

Regards, Wil Taylor

o Trust - But Verify!
o We believe to be true what we prefer to be true. [Unknown]
o For those who believe, no proof is required; for those who cannot believe, no proof is possible. [variation,Stuart Chase]
o Unfortunately, in science what You 'believe' is irrelevant. ["Orion", Homebuiltairplanes.com forum]

 

[sodengineer]

Thank you both. Maybe this is a cement headed civil asking, but I still don't understand how the panels were ejected perfectly every time. I know on Apollo 7 one of the panels did not open all the way. So why did that not cause the spent 3rd stage to start to wobble or rotate?

Again, more of an idle question than a "need to know."
Thanks.

 

[VEBill]

Apparently the S4B stage have a mass of 13,500 kg empty, so they're not going to take off with a slight nudge. Furthermore, the fuel tanks were probably not quite empty, because some were subsequently relit and crashed into the Moon. Of course, let's not forget that for the purposes of your question, the empty S4B stage also contained the fully loaded Lunar Module which had a mass of another 15,000 to 16,000 kg. So, getting close to 30 tonnes combined.

Interestingly, the CSM was about 29 tonnes fully loaded. So about the same.

Also, the S4B stage did have attitude control (Wiki says: 2x APS Modules), so perhaps those were used to ensure attitude stability. Speculation.

 

[WKTaylor]

It is likely that at least one of the early S-IVB's has been detected... when it was temporarily captured by in a 'chaotic earth orbit' after several heliocentric orbits... but [now] has likely returned to heliocentric orbit due to lunar gravity perturbations...

Newly Discovered Object Could be a Leftover Apollo Rocket Stage
... An analysis of the orbital motion of the newly discovered object J002E3 indicates that it could be a leftover Saturn V third stage from one of the Apollo missions, most likely the Apollo 12 mission, launched on November 14, 1969. ...

https://cneos.jpl.nasa.gov/news/news134.html

[from 2002 CNEOS article]


Regards, Wil Taylor

o Trust - But Verify!
o We believe to be true what we prefer to be true. [Unknown]
o For those who believe, no proof is required; for those who cannot believe, no proof is possible. [variation,Stuart Chase]
o Unfortunately, in science what You 'believe' is irrelevant. ["Orion", Homebuiltairplanes.com forum]

 

[sodengineer]

<<Also, the S4B stage did have attitude control (Wiki says: 2x APS Modules), so perhaps those were used to ensure attitude stability. Speculation.>>

That makes some sense. I knew it had ullage motors, but I did not know it had attitude control. I guess I never saw them (or never had them pointed out to me.)

Thank you for the insight.