A11 landing spot.

[drewid]

I've made a new thread for this as I don't want to take the other thread OT.

Sept 3, 2011 21:16:39 GMT -4 Bob B. said:

The following should give you what you want regarding weights of various components at various times:

history.nasa.gov/SP-4029/Apollo_18-37_Selected_Mission_Weights.htm

As you probably know, the CM/LM was pressurized to just 5 psi. I don't know the exact size of the docking tunnel, but it was about 30 inches diameter. This means the force pushing on the LM was about 3500 lbf, which was enough to give it an initial acceleration of about 3.3 ft/s². Of course, as soon as the vehicles undocked, that pressure was very quickly relieved; therefore, the duration the LM was subjected to any kind of a push was only a fraction of a second. I doubt the LM received even 1 ft/s delta-v as a result of the tunnel pressure. At the time of CSM-LM separation, the CSM's mass was only about a ton more than the LM, therefore it received just slightly less delta-v in the opposite direction.

That's just what I'm looking for. CSM at Separation for Lunar Landing 37,076.8 lbs LM at Separation for Lunar Landing
33,683.5 lbs. I'm sort of surprised they're as close in mass as they are but there's a lot of CSM fuel been burnt and a couple of astronauts moved from CSM to LM.

It's interesting that you come up with 1fps. I've seen that in one of the docs. I've read through so much in the last couple of weeks that i'm having trouble keeping it straight just where I saw it. I thought it might be the mission report, or ALSJ but looking through now I've not been able to spot it.

What I'm looking for is something that makes sense of the Reed quote. Now there's already a 21000 foot uprange error noted in the mission report, if the csm is also running a little slow that might explain the extra. Presumably the instrument error would be being corrected regularly, but even so...

Of course the Reed measurement is the only one that measures the relative positions of the CSM and LM. I'm wondering of that Reed quote came just before they realised about the uprange error. It's also interesting that the landing radar position and the photography(geologists) position match so well.

[drewid]

Aha, this doc even gives the delta V for each orbit of the CSM.

next.nasa.gov/alsj/a11/A11TrajectoryAnalysis.pdf

not that it's very readable on the tiny screen I'm using right now.

[Bob B.]

Please refresh my memory. What's the Reed quote?

[drewid]

"I sat down at the console for that prelaunch shift and was debriefed by the previous team to complete hand-off. I probably had my second cup of coffee by then and got on the loop to SELECT to get the best landing site. I remember asking SELECT what he had for landing site coordinates. I’ll never forget his answer when he said, “take your pick FIDO!” I also remember not reacting too positively to his offer. He explained that we had five different sites. He said “we have MSFN(tracking radars), PNGS (primary LM guidance computer), AGS(backup LM guidance computer), the targeted landing site and, oh yes, the geologist have determined yet another site based upon the crew’s description of the landscape and correlating that with orbiter photos”. No two of these were even close to each other."

"I remember taking my headset off and walking up to the Flight Direc- tor, Milt Windler to explain the situation. We only used that kind of face to face communication when we had a serious problem such as this. I detailed the problem as best we knew it and the process that we’d have to follow to get the data we needed, and why we had to start a rev early to finish the calculations and then find the critical lift-off time for lunar launch. I recall the CapCom instructing Buzz Aldrin that we needed him to perform the RR check early but I don’t believe that CapCom explained why, just another check was all. Shaft & trunnion angles were passed up to aid acquisition. Right on time as the CSM cleared the horizon we began seeing data. We counted the agonizing minutes as the telemetry came flowing in until the CSM was receding. Now we had the data we needed to run the problem (a rendezvous problem in reverse) and get the correct liftoff time*. And that’s what we used. Later we would find out just where were we on the surface. We were actually over 25,000 feet from the nearest of the other five choices we had! At 5,000-fps orbital velocity of the CSM that could have been up to a ten second error in liftoff."

Apparently quotes from the book "From the Trench of Mission Control to the Craters of the Moon"

y'see I reckon this is where they spotted the uprange error and corrected, but I don't have that particular book so I can't check the accuracy of the quote or the circumstances around it.

[chew]

The best part about Dr. Socks quoting that part of Reed's account was when he injected his own special brand of ignorance by characterizing the rendezvous as "threading the needle". When I pointed out to him that "threading the needle" took 4 hours to complete he, of course, pretended he didn't see my post.