Apollo 12 - Experiences, Odds & Ends

[indy91]

Vector Comparison Display and Vector Panel Summary go hand in hand. On the vector panel summary there is a TLM button to get all the telemetry state vectors from the current vessel. That only makes a time tag appear on the page for each vector. I think in reality this was an automated process and it just stored the latest telemetry state vectors. So to "capture" a state vector from telemetry you have to move it to a more permanent saving location, the vector evaluation table. That's using the EV button. Then the telemetry vector will be assigned a vector ID which can be input on the vector comparison display. For more details, the displays are covered in the RTCC MFD manual.

 

[Miriam]

The TLM button gives me LGC and AGS SVs (both are powered down, interestingly), but no CMC SV (which is powered on). Or do I have to shift the MPT to inactive? Some things don't work when it's on, so...

 

[indy91]

Oh that's what you mean. It's one of those things that only works in the vessel you are currently in. So if you want to have the CMC (or even IU) state vectors you need to switch to the CSM, open the RTCC MFD there and press the TLM button then. MPT on or off doesn't matter in this case.

 

[Miriam]

I am in the CSM. Okay, the LM is still docked and when I open RTCC MFD in the CSM it also opens in the LM, but apart from that...

 

[indy91]

When in the CSM, go the configuration page. Is that set to LM or LM+CSM docked? It needs to be CSM or CSM+LM. That's the only explanation I have for that behavior. I just tried it, I don't know how it doesn't end up with a CTD but LGC and AGS state vectors appear, even if they surely will be nonsense, as the CSM has no LGC or AGS. I probably need to add some more logic checking the vessel class there. That CSM/LM business in the config menu will go away eventually, right now there are still a lot of places that check on the vessel type this way.

 

[indy91]

Before you started flying Apollo 12 I had already started my own mission but got distracted for a while. Finally got back to it and just did the landing. What I find odd is that the targeted landing site seems to be quite different from the actual one. I have to do a bunch of very early LPD commands to the left to get to the actual landing spot. They must have refined the landing site vector in the LGC before landing, but I can't find any specific reference to it.

And getting started with P57, I had some trouble and found there was a typo in the LGC padload for Apollo 12, which made the left detent unusable (its direction was all wrong). You can fix it by doing this:

V24 N01E
3403E
3120E
65253E

 

[Miriam]

Well, I had planned to do 'the day of days' this weekend, but one of my kids had something against it and brought a high quality flu (NOT Corona -of course not) home from school and now I'm dead in the water (or bed. Whatever).?

 

[rcflyinghokie]

Well, I had planned to do 'the day of days' this weekend, but one of my kids had something against it and brought a high quality flu (NOT Corona -of course not) home from school and now I'm dead in the water (or bed. Whatever).?

Ouch well get some rest and recover!

 

[Miriam]

Oh, I'm getting pampered quite well. My daughter (5) just brought me a big mug of cocoa.
And has caused a big mess in the kitchen while making it, when I get the rant she's receiving from my wife right. Those have to be the joys of family life, I guess...?

 

[Miriam]

Hm...has somebody seen a complete scan of the LM timeline book? All I can find are missing pages 3 and 4 (essentially DOI and PDI prep). Yes, I do get along with the flight plan and my own systems knowledge, but having this nicely condensed on two pages would be very convenient.

 

[rcflyinghokie]

Hm...has somebody seen a complete scan of the LM timeline book? All I can find are missing pages 3 and 4 (essentially DOI and PDI prep). Yes, I do get along with the flight plan and my own systems knowledge, but having this nicely condensed on two pages would be very convenient.

Based on the thread I assume you mean Apollo 12's. I am pretty sure we don't have a copy with those missing pages currently.

They should be pretty much the same as 11, but again that is an assumption

 

[Miriam]

Yeah, I've found that, too. The sequence of events is slightly different, so I'm currently pen & inking it to match Apollo 12. Yaay...
And, as I'm working through it:
What was the deeper sense of the P30/P40 stuff at 108:30:00 in the LM? I'd figure that this was a last sanity check of the LGC prior to DOI: see if it comes up with the correct angles in N18. Otherwise something had gone wrong with the alignments and/or REFSMMATs.
As we talk about REFSMMATs: how can I make sure in RTCC MFD that both CSM and LM receive the exact same REFSMMATs for the docked alignment? Just calculate it once and never touch that page again until both uplinks are in?
Oh, and is the separation burn the CSM does after undocking the no-brainer I suspect it to be? TIG = 108:24:22, dV = +2.5 fps in Z? I'm not supposed to receive a target load for that, not even a PAD, so I'd figure out it has to be that way.

 

[indy91]

What was the deeper sense of the P30/P40 stuff at 108:30:00 in the LM? I'd figure that this was a last sanity check of the LGC prior to DOI: see if it comes up with the correct angles in N18. Otherwise something had gone wrong with the alignments and/or REFSMMATs.

P40 also has a different downlink list for telemetry, just another check that the LGC is in a good state. They often enter P40 early if a burn happens without comm to the ground.

As we talk about REFSMMATs: how can I make sure in RTCC MFD that both CSM and LM receive the exact same REFSMMATs for the docked alignment? Just calculate it once and never touch that page again until both uplinks are in?

CSM and LM REFSMMATs are being treated separately. This might be a case where the button to move REFSMMAT around (G00) might be useful. If you have e.g. calculated the landing site REFSMMAT while being in the CSM you can move it to the LM with: "G00,CSM,CUR,LEM,CUR;". That moves the current CSM REFSMMAT into the slot for the current LM REFSMMAT.

Oh, and is the separation burn the CSM does after undocking the no-brainer I suspect it to be? TIG = 108:24:22, dV = +2.5 fps in Z? I'm not supposed to receive a target load for that, not even a PAD, so I'd figure out it has to be that way.

If you can decipher it, the CMP Solo Book has more detailed procedures than the flight plan: https://history.nasa.gov/afj/ap12fj/pdf/a12_cmp_sb.pdf

I think what you have to do to trick P41 to maneuver you to an attitude for a +Z axis burn is enter the DV as +2.5 + 0.0 + 0.0 in P30. And then hopefully P41 gets you to the attitude so that the +Z axis burn means burning radially towards the Moon. That sets up the desired trajectory. LM behind at DOI, but if DOI doesn't happen the radial only burn means the LM will come back to the CSM on its own after one orbit.

 

[Miriam]

CSM and LM REFSMMATs are being treated separately. This might be a case where the button to move REFSMMAT around (G00) might be useful. If you have e.g. calculated the landing site REFSMMAT while being in the CSM you can move it to the LM with: "G00,CSM,CUR,LEM,CUR;". That moves the current CSM REFSMMAT into the slot for the current LM REFSMMAT.

So the following should work:
-get CMCs REFSMMAT with the DWN button
-G00,CSM,CUR,LEM,CUR
-uplink that with mask 23
Or do I have to switch around something in the config page?

I think what you have to do to trick P41 to maneuver you to an attitude for a +Z axis burn is enter the DV as +2.5 + 0.0 + 0.0 in P30. And then hopefully P41 gets you to the attitude so that the +Z axis burn means burning radially towards the Moon (so burning down).

The solo book isn't really helpful here. It's first stated that one should use +2.5/0/0 as dV -and then later in the actual time line it says 0/0/+2.5. The latter makes sense to me and would give me the right N85 values to null when I maneuver to the burn attitude manually.

Oh, and how do I get the following things:

• LGC abort constants
• AGS abort constants
• AGS K factor (although I could do that manually, sure enough)

 

[indy91]

So the following should work:
-get CMCs REFSMMAT with the DWN button
-G00,CSM,CUR,LEM,CUR
-uplink that with mask 23
Or do I have to switch around something in the config page?

Downlink from CMC to RTCC is somewhat redundant as the REFSMMAT was calculated in the RTCC and then uplinked. So it should already be identical. But it doesn't hurt, if nothing changes when pressing DWN then it was already the same. Nothing to switch around in the config, just remember that the REFSMMAT for the LGC during LGC activation is the one time you uplink the actual and not the desired REFSMMAT.

The solo book isn't really helpful here. It's first stated that one should use +2.5/0/0 as dV -and then later in the actual time line it says 0/0/+2.5. The latter makes sense to me and would give me the right N85 values to null when I maneuver to the burn attitude manually.

If I understand the detailed procedure for the sep maneuver correctly on PDF page 28 then I think you just use the DV input in P30 for the auto maneuver. What you end up with in P41 after the burn as "residuals" is probably 2.5 in DVX (because you aren't burning DVX) and then in DVZ it starts at 0 and ends up as 2.5.

Before all this they already seemed to have used P30/P41 for auto maneuvering to the undocking attitude. And there you use 0 0 +2.5 as input in P30. But again, this is just to get the right attitude in P41, not an actually desired DV.

Oh, and how do I get the following things:

• LGC abort constants
• AGS abort constants
• AGS K factor (although I could do that manually, sure enough)

LGC and AGS abort constants can be updated under Utilities, Descent Abort. That page works for Apollo 11 and 12 only for now. But I wouldn't bother much with it, I know from Apollo 11 they checked the values in the LGC and AGS and decided they are close enough to not have to do an update. So I would just enter the numbers from the timeline book if they differ from what's already in the AGS.

AGS K-Factor can be updated on the "AGS SV PAD" page. After you have initialized the AGS clock (DEDA 377) then press the KFA button on that page and update the time in V47 with that. Should be within a second or two of the number that is already there, or else something didn't go right.

 

[rcflyinghokie]

The solo book isn't really helpful here. It's first stated that one should use +2.5/0/0 as dV -and then later in the actual time line it says 0/0/+2.5. The latter makes sense to me and would give me the right N85 values to null when I maneuver to the burn attitude manually.

I think I can clarify a bit here. The P30/P41's are used to establish both LM undocking attitude and CSM sep attitude. So the first one you use to maneuver to undocking attitude, then you call P30 and change the time and the dv, and the next P41 should have you in the same attitude as undocking, but set up timing and dv wise for the correct sep burn.

 

[Miriam]

Well, for undocking it has to be 0/0/+2.5. Logically, this makes 2.5/0/0 the right one for the sep burn (at least P41 throws out the right attitudes in both cases).?

Edit: I'm on the ground. But I have no idea if I'm where I should be. I saw nothing like the snowman during P64, not even those bigger craters in the vicinity, so I can't really tell. ?‍

 

[indy91]

Edit: I'm on the ground. But I have no idea if I'm where I should be. I saw nothing like the snowman during P64, not even those bigger craters in the vicinity, so I can't really tell. ?‍

I downloaded the Apollo 12 landing site sceneries by ggalfi (http://absimp.org/orbitersim/apollolandingsites.html), that enhances the landing visuals a lot. The "Oceanus Procellarum" base marker is basically in the crater where the Surveyor landed. The landing point with the pre-mission landing site vector in the LGC leads you not quite to that base marker for some reason. If you do some hard corrections with the LPD just when P64 starts you can get to the actual landing site anyway.

I don't know if it's the lighting condition at the time of landing, but I've only been able to recognize the snowman a few hours later. So I would suggest downloading the scenery, doing some big corrections early in P64 and once you get close to the base marker you will see the Surveyor crater and pick a landing spot.

 

[Miriam]

Jupp, that helps a lot. I changed my RLS to -3.01381/-23.41930 and P64 targeted me right inside the belly of the snowman. I didn't recognize it immediately, but coming closer I recognized this characteristic leg-belly-leg formation of the craters. Switched to P66, hit the brakes (I had the feeling that P64 was about to land me inside the belly crater) -and landed on the western slope of the "left leg" crater.?‍ Okay, next time I'll put more trust into the LPD, noted. ?
Btw., how are the lift-off times for T1,T2 and T3 calculated? T1 seems to be a simple "wait some seconds after touchdown", but T2...either I'm overthinking it and this is a simple PDI +XX:XX thing, or there's more to it. T3 -hmm...I'd say this is a 'normal' lift-off, right?
And how do I get the ABO page to work? It only starts to calculate and never comes to an end, whether I'm in flight or landed.
Edit: flew it again. What distracted me was that Orbiter switched from low res to high res textures some 10 seconds after P64 came up. Is it possible to make it switch earlier?

 

[indy91]

Btw., how are the lift-off times for T1,T2 and T3 calculated? T1 seems to be a simple "wait some seconds after touchdown", but T2...either I'm overthinking it and this is a simple PDI +XX:XX thing, or there's more to it. T3 -hmm...I'd say this is a 'normal' lift-off, right?

T1 is the last opportunity to abort with P71. That time could be mission specific I guess. The insertion velocity for P70/P71 insertion is variable and T1 is when the chosen rendezvous profile can't be reached anymore. The minimum (normally) targeted apolune altitude is 30NM and that is what you will get when aborting at T1.

T3 is a normal lunar liftoff one orbit after landing.

T2 is a bit more complicated. It uses a different rendezvous profile than T1, TPI happens one orbit later than with T1. On Apollo 11 they did recalculate the time when T2 happens during the actual mission. Just like for T3 they ran the Lunar Launch Window Processor (LLWP) for it. Normally they would use the option to have CSI at 50 minutes after insertion. For this T2 calculation the LLWP actually can't model the boost and height adjustment maneuver (called CSI1). So they used the option to have CSI at 217 minutes after insertion and then biased the calculated liftoff time by 74 seconds. So yeah, a bit complex... I guess if you want to try it you can just launch at the planned time of T2, that is usually good enough.

And how do I get the ABO page to work? It only starts to calculate and never comes to an end, whether I'm in flight or landed.

Well if you are already landed then it's a bit too late to calculate abort constants for P70/P71 and the AGS haha. I don't know how compatible I made it with the MPT and I haven't checked this calculation in a long time. If it works with the MPT then you need to have the DOI maneuver on the MPT. Without the MPT the DOI maneuver already has to have happened. So basically the program needs state vectors from CSM and LOI as they would be before PDI. And then you also need to input a TPI time. That time would be the one for the first segment of the abort constants, So 0 < PDI < 10 minutes. That time would be roughly 112:57:12. Do you know how to calculate an updated time there?