Help appreciated for a Layman

[n72.75]

Yes, you are correct. I don't remember how long it takes to cool in the current version, but the real one, and hopefully the next fuel cell update, would be on the order of 2-6 hours depending on how much load was on the cell before it was shut down.

 

[Lupus_Vulpes]

Just a quick question about the FDAI when aligning the GDC to IMU. This is what i want to see, right? Both FDAI's looking identical when i push the GDC ALIGN button?

 

[indy91]

Yes, that is the goal, to make the GDC have the same alignment as the IMU. Sadly in this screenshot I can't see some relevant switches to the left of the ATT SET switch. It is slightly suspicious that the FDAIs show 0° in all angles, that is what they would also show if one or both of the FDAIs are unpowered. So you could have aligned the GDC to an unpowered (all zeros) FDAI and not the actual IMU alignment. But it might be a coincidence.

 

[Lupus_Vulpes]

Ok, this is the original state before alignment, scenario "Apollo 8 - 03 - After Insertion Checklist T+54min:

After that, i initiate the "GDC to IMU Alignment" procedure... FDAI SEL 1 and i enter V16 N20E in DSKY to show IMU angles.

After that it says "ATT SET tw(3) - set to FDAI att", ok... Well... FDAI 1 att is 180 R - 0 P - 0 Y so i set it to those specs:

I change FDAI source to ATT SET and the ATT SET to IMU, and i null the FDAI errors to the angles displayed on the AGC. i set the ATT SET back to GDC and push the ALIGN GDC button, and this is how they look like in the end.

After all is done, this is how it looks like when i set the FDAI SEL bak to 1/2

 

[indy91]

Ah you know what, during that time the ORDEAL is driving FDAI 1 in pitch so that the FDAI works as a local horizon. To do the GDC alignment to IMU you need to temporarily deactivate that (FDAI 1 to INRTL). Do you know where the click spot is for the ORDEAL panel? It's above the EMS. Click there somewhere and the ORDEAL will appear (panel 13). The actual location of the ORDEAL is somewhere else (in our 2D panel system twice to the left from the main panel, and there on the upper edge) but it's helpful to have access to it on the main panel.

Maybe it would be helpful to add that to the Checklist MFD, switching the ORDEAL to inertial and then after the GDC alignment back to orb rate. That's not in the actual Apollo launch/TLI checklists but is certainly implied and necessary.

 

[Lupus_Vulpes]

Thought about that actually that the ORDEAL might be in the way of displaying correct data. After switching off ORDEAl and following the above procedure, both FDAI's show the same data. Alright... good to know!

 

[Lupus_Vulpes]

I'm having troubles with the P23 maneuver... My rates are huge when i finish, soi have a few questions...
When the automanouver finishes at F59, my optics don't end up near the horizon, they are a bit off...

My question is, should i calibrate the optics to the horizon when i do the F59 by moving the optics themselves, or by moving the CSM?

when i was finished i got those results, and i think they re not that good, they should all be below 500

V06 N49
R1 +00966 (delta R)
R2 +02521 (delta V)

 

[Thespacer]

I'm having troubles with the P23 maneuver... My rates are huge when i finish, soi have a few questions...
When the automanouver finishes at F59, my optics don't end up near the horizon, they are a bit off...

View attachment 23987


My question is, should i calibrate the optics to the horizon when i do the F59 by moving the optics themselves, or by moving the CSM?

when i was finished i got those results, and i think they re not that good, they should all be below 500

V06 N49
R1 +00966 (delta R)
R2 +02521 (delta V)

I’m fairly certain the Optics cal (F59) is irrelevant for NASSP purposes, as the Optics are always perfectly calibrated. So, while the auto-manoeuvre should leave the optics pointing near the horizon, if you do the optics cal mark a bit off, then that should not affect the following star/horizon marks.

As for your N49, yeah those are no good. It is possible to get acceptable values, within the limitations of Orbiter. This recent thread might be a good start for you to explore:
Thread 'NASSP: P23 Program Explanation'
https://www.orbiter-forum.com/threads/nassp-p23-program-explanation.36210/

 

[Lupus_Vulpes]

Finally managed to correctly execute the P23 program, am happy with the results
I always get results below +00010 now, you just have to be fast when aligning the SCT with horizon

 

[Lupus_Vulpes]

I have a question about the "P21 Ground Track Determination", I am currently at mission time +05:15:00 and i entered 69h 10m 00s as the time of LOI and after PRO in V06N43 i got these results:

R1 -01408 LAT
R2 +13637 LNG
R3 -01393 ALT

Is this right or did i do something wrong? Do i enter the time parameters as R1 +00069 R2 +00010 R3 +00000 or R1 -00069 R2 00010 R3 -00000? My first MCC was scrubbed, so i guess i am on a good path...

 

[indy91]

You didn't have a state vector uplink after the P23s, right? So this P21 will have been calculated with the state vector updated by the P23s. Your N49 results look really really good, but I wouldn't trust that your state vector is now spot on. That isn't really possible in Orbiter I think. Also, your actual trajectory might still be a bit off from the desired even if MCC-1 was scrubbed. I think those two things together can easily explain that negative altitude at 69:10:00. If you play around with the GET you can probably see an even lower altitude. In a mission techniques document it talks a bit about perilune sensitivity. It says that at the time of MCC-1 if your trajectory was off by 1 ft/s in the worst possible direction then the perilune could be off by 36NM. So a few feet per second already add up to quite a large number.

You used P21 correctly. The time you enter in each register is hours, minutes, centiseconds of GET. So that should of course be + and not -.

 

[Lupus_Vulpes]

You didn't have a state vector uplink after the P23s, right? So this P21 will have been calculated with the state vector updated by the P23s. Your N49 results look really really good, but I wouldn't trust that your state vector is now spot on. That isn't really possible in Orbiter I think. Also, your actual trajectory might still be a bit off from the desired even if MCC-1 was scrubbed. I think those two things together can easily explain that negative altitude at 69:10:00. If you play around with the GET you can probably see an even lower altitude. In a mission techniques document it talks a bit about perilune sensitivity. It says that at the time of MCC-1 if your trajectory was off by 1 ft/s in the worst possible direction then the perilune could be off by 36NM. So a few feet per second already add up to quite a large number.

You used P21 correctly. The time you enter in each register is hours, minutes, centiseconds of GET. So that should of course be + and not -.

I noticed when entering different GET in P21 the altitude changes drastically, i tried to see at what GET would the ALT be nominal, and i got it around +69:02:50 the alt was R3+00692 so 69.2 NM

 

[indy91]

I think the goal of that P21 excerise was to find the perilune, so the time of the closest approach to the Moon. That 69:10:00 time was probably fairly close to it. It won't be far away from 180° longitude. Of course in your case the perilune is actually inside the Moon. 69.2NM is quite far away from the perilune and so the altitude rate at that time will still be fairly large.

 

[Lupus_Vulpes]

So to get a visual representation of what's going on, P1 is my calculated perilune with minus -139.3 NM ALT and P2 is where it should be roughly, factoring in LAT and LNG for P1 it's currently on the Lunar latitude -014.08° and longitude +136.37, so is this correct... sorta?

 

[indy91]

Sort of. P1 isn't your actual perilune, it's just a random point along your trajectory (or at least the trajectory the AGC currently thinks you are on) at the time you specified in P21. On trajectories close to free return the perilune is usually close to 180°, but not exactly. To figure it out exactly you would have to do trial and error with the input time in P21 until you get the lowest altitude. The trajectory around the Moon is retrograde so along your trajectory your longitude becomes smaller. So with P1 being at +136.37° I would suspect you have to try an earlier time to find the perilune.

 

[Lupus_Vulpes]

Yeah, the lowest altitude is at GET +69:09:15 at LNG +179.37, ALT -02268