Apollo 12 - Experiences, Odds & Ends

Miriam

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Do you know how to calculate an updated time there?
Aha! I thought it would do that by itself. No, I don't. ? Or does it use the times from the launch window processor?
 

indy91

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The launch window processor doesn't calculate a TPI time either, it needs to be input there as well. The easy way to do it is under Targeting, Rendezvous, TPI times. Choose your CSM as the vessel, use the orbital midnight option and then input an estimate of the TPI time. The "correct" way of getting TPI times is using the MPT, MCC Displays, Sunrise/Sunset Table. Orbital midnight is defined as 23 minutes before sunrise, so you have to do some math there. The advantage is it will show you a bunch of sunrise times and you can calculate a few TPI times at once. Because usually you need 3-4 of them for the various PADs the crew got before PDI, as different rendezvous profiles are used for T1 vs. T3 etc.
 

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CSM plane change burn coming up now. I figure that TH1 is the usual 'next hour to TIG' thing. But TH2...input guide says 'align time'. I guess that has to be the LM lift-off time, right?
 

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CSM plane change burn coming up now. I figure that TH1 is the usual 'next hour to TIG' thing. But TH2...input guide says 'align time'. I guess that has to be the LM lift-off time, right?
Correct, T-Align is the same as the LS REFSMMAT alignment time for lunar liftoff, which would be LM liftoff time in this case.
 

Miriam

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The SPQ is confusing me: I set it up right (I guess), but its times and those from P32 don't match. While CSI and CDH TIG are within 1 min, TPI TIG is over 5 mins off. Any ideas?
 

indy91

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In the SPQ the TPI time is usually an input and in the AGC it's always an input. Maybe you are running the SPQ mode to achieve a specific Delta Height? The SPQ has two modes. When you use "Fixed TPI time" then it works like in the AGC. TPI time has to be input and it will iterate on the DH to achieve TPI at that time. In the "Fixed DH" mode it will always converge on the desired DH but then the TPI time can't be specified and might be different than desired. Maybe you are using the Fixed DH mode?

There also is an "optimum CSI" option, which tries to achieve both the DH and the TPI time by letting the CSI TIG slip by up to +/- 5 minutes. But the trajectory has to be near perfect for that to achieve the desired effect and it shouldn't be used when you have already "commited" to using a specific CSI TIG.
 

Miriam

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Right, I forgot that TPI time is indeed an input in P32. D'oh!?‍♀️

Another thing: the LM tracking light seems to 'vanish' when I switch from the SXT view and back. When I switch to the CSM and go to the SXT it's there at the first time. But when I leave the SXT view and come back later, it's not there. I have to switch to the LM and back to the CSM to bring it back. No problem, I just activate the docking HUD and put the crosshairs in the middle of the box, but strange...
 

rcflyinghokie

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Right, I forgot that TPI time is indeed an input in P32. D'oh!?‍♀️

Another thing: the LM tracking light seems to 'vanish' when I switch from the SXT view and back. When I switch to the CSM and go to the SXT it's there at the first time. But when I leave the SXT view and come back later, it's not there. I have to switch to the LM and back to the CSM to bring it back. No problem, I just activate the docking HUD and put the crosshairs in the middle of the box, but strange...
I haven't seen the light vanish before, only the yellow box for vessel marking. The light should be visible as long as that tracking light is facing the CSM. Do you have a scn I can try to reproduce with?
 

Thespacer

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Another thing: the LM tracking light seems to 'vanish' when I switch from the SXT view and back. When I switch to the CSM and go to the SXT it's there at the first time. But when I leave the SXT view and come back later, it's not there. I have to switch to the LM and back to the CSM to bring it back. No problem, I just activate the docking HUD and put the crosshairs in the middle of the box, but strange...
FWIW I’ve noticed the visibility range of the LM through the CSM sextant during RV is not quite as high as it used to be in previous builds. I used to be able to spot both the yellow box and tracking light at about 110NM in range, but now they appear at about 80-ish. Not a huge drama, as you’ve pointed out the HUD docking is a sufficient workaround.
 

rcflyinghokie

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FWIW I’ve noticed the visibility range of the LM through the CSM sextant during RV is not quite as high as it used to be in previous builds. I used to be able to spot both the yellow box and tracking light at about 110NM in range, but now they appear at about 80-ish. Not a huge drama, as you’ve pointed out the HUD docking is a sufficient workaround.
Might just be a perception thing as those distances haven't been changed at all, and the vessel box draw distance is an orbiter thing I believe. I will say the LM tracking light visibility through the sextant isn't is far as it was IRL though, it had the potential to be seen 400nmi away (according to the AOH) but I believe it shows up around 100 in orbiter.
 

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Coming up on LM deorbit burn. Big question: how did they do it? Just bring up P42 and don't PRO on the V99?
 

indy91

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Coming up on LM deorbit burn. Big question: how did they do it? Just bring up P42 and don't PRO on the V99?

I believe that is correct. Ullage burn until RCS propellant depletion.
 

Miriam

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Good to know that they did it exactly like I did. Well, without the signal delay, that is.😁
And I knew it: they did indeed target for some specific impact point. RTCC MFD can't calculate that yet, right?
 

rcflyinghokie

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Good to know that they did it exactly like I did. Well, without the signal delay, that is.😁
And I knew it: they did indeed target for some specific impact point. RTCC MFD can't calculate that yet, right?
Not directly, I believe the best option is to use the space digitals display and check for an impact point based on a burn and iterate from there.
 

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PC-2 coming up. Two questions: first, what is the target and align time? Lalande? Descartes? Second: how do I obtain the 'photo REFSMMAT'? It has to be some nominal thing, as yaw for tracking the various landmarks is 0°, but the rest -no idea.
 

rcflyinghokie

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PC-2 coming up. Two questions: first, what is the target and align time? Lalande? Descartes? Second: how do I obtain the 'photo REFSMMAT'? It has to be some nominal thing, as yaw for tracking the various landmarks is 0°, but the rest -no idea.
Ahh those have always been interesting since I do not believe we have the actual data used. I believe what I did is use Google Moon to find an approach path that crosses the photo sites and used the GPM to generate a PC that crosses it. I then picked one of those spots as a landing site REFSMMAT.

No idea if this is correct but it seems to work-ish :p
 

Miriam

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I think I got it: I just read through the transscripts and it seems that a) DE-1 (8.883 S/15.550 E) was the target side (Capcom says it's "on track") and b) align time was 165:25:00 (actual value for T2 was 165:29:17; TCA was 75 s later, at about 165:30:30; however, they were about 5 mins behind all other flight plan times, which makes 165:25:00 most reasonable).
I haven't tried it, though. I'm just done with those tracking excercises and not really inclined to jump back and do most of the day again.😮‍💨
 

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Hi All.

A random Apollo 12 query, regarding TLI monitoring. Seemed like an Odds and Ends type question.

From the Tech Crew Debrief, 5.1:

“The TLI burn was normal in all respects. My one comment is that we had the little additional program in the CMC to count down to timebase 6 which I thought was extremely good. Dick set it up and had it running.“

Any idea what they are referring to?
 

rcflyinghokie

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Hi All.

A random Apollo 12 query, regarding TLI monitoring. Seemed like an Odds and Ends type question.

From the Tech Crew Debrief, 5.1:

“The TLI burn was normal in all respects. My one comment is that we had the little additional program in the CMC to count down to timebase 6 which I thought was extremely good. Dick set it up and had it running.“

Any idea what they are referring to?
It looks like they had an EMP they used to monitor time until TB6.

002:25:41 Gordon: And Houston, if you're not going to use the computer, I'd like to go ahead and put in the Timebase 6 program that we have in our erasable, just to watch it.

If you check out the Apollo 12 launch checklist, it's in the backup TLI procedures. Also in the Apollo 13 main TLI procedures.

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