Apollo 9 Problems

[Max-Q]

So I am working through the Apollo 9 mission, and I have successfully completed the first four flight days. Now, I am on my third try at day five, rendezvous day. For the Docked IMU Coarse Align, the checklist says to set ref to Identical for everything, except LVLH for Apollo 9 rendezvous. Do I use LVLH?

 

[rcflyinghokie]

Exactly as it says, LVLH for Apollo 9 rendezvous, and Identical for everything else. You align the platform twice for Apollo 9, once for the docked DPS and once before rendezvous. For the docked DPS (and every other mission's docked alignment) you will use "Identical"

For Apollo 9's rendezvous alignment you will be using LVLH, it is the only case where this is used.

 

[Max-Q]

That is what I thought, but on my previous try at day 5, things really went bad later.

 

[rcflyinghokie]

Well let us know if we can help you through it, many places to make mistakes!

Here, the IRC or discord we are around to help! https://discord.gg/n8YvgGWG

 

[Max-Q]

Ok, now I am at AGS Initialization. What does "Set AGS Time (377) Biased" mean? I have 16 65 on the DSKY showing the GET.

 

[rcflyinghokie]

Ok, now I am at AGS Initialization. What does "Set AGS Time (377) Biased" mean? I have 16 65 on the DSKY showing the GET.

So this is setting the AGS clock. AGS cannot hold a time as large as the LGC, so you "bias" it so it only has to display and compute a smaller number.

Since you are on rendezvous I assume, you will see it says (90h Bias). So this means your AGS time is your mission time minus 90 hours.

AGS stores its time in decimal minutes, so say your mission time is 95h0m0s, your AGS time will be 5 hours, or 300 minutes, or on the DEDA 377+03000.

 

[Max-Q]

So if my GET is 91h 38m 00s it would be 377+00980, correct?

 

[rcflyinghokie]

That is correct. 98.0 minutes

 

[Max-Q]

Now for the CSM RCS sep burn. In P30 I am instructed to load the PAD TIG. Is this the TIG listed in the remarks section of the LM PHASING PAD as "Your SEP time: 092:59:49" or am I missing a PAD specific for this maneuver? In Apollos 10 and 11 there was a "SM RCS SEP" PAD or something like that.

 

[Max-Q]

Update, I went ahead and tried that and it seems to have worked.
Now I am in at "V84 Target dV" in the LM. It wants dV XYZ and TIG. Is this for the phasing burn?

 

[rcflyinghokie]

Now for the CSM RCS sep burn. In P30 I am instructed to load the PAD TIG. Is this the TIG listed in the remarks section of the LM PHASING PAD as "Your SEP time: 092:59:49" or am I missing a PAD specific for this maneuver? In Apollos 10 and 11 there was a "SM RCS SEP" PAD or something like that.

Yep that is the pad SEP time.

Now I am in at "V84 Target dV" in the LM. It wants dV XYZ and TIG. Is this for the phasing burn?

So this is for the results of the CSM RCS SEP burn. What you are doing is putting the CSM sep burn data into the LM to update the CSM state vector.

 

[Max-Q]

Ok I am now up to the AGS Phasing burn. I get ignition at 10% throttle as expected, then 15 seconds later I manually power up to 40% as instructed. However, the engine does not shut down on time. The PAD says that this is a 26 second burn, but the engine runs for over a minute and a half before cutoff. I know I got WAY to much dV because PAMFD (yeah, cheating, I know) shows a PeA of -0.3nm!

 

[indy91]

I'm not sure if the checklists have this wrong, but for Earth orbit the AGS uses a different scaling for numbers. That means if you input a DV vector to the AGS the last digit isn't a tenth of a foot per second but instead a full foot per second. So 2.0 ft/s would be +00020 in lunar orbit but only +00002 in Earth orbit. So maybe you just did a burn that is 10x the desired one?

 

[Max-Q]

Okay, THAT explains a lot! But what do I do about the tenths of a foot per second? Trim them out with the RCS after the burn?

I'm not sure if the checklists have this wrong, but for Earth orbit the AGS uses a different scaling for numbers

Yeah, no mention of that in the checklists.

 

[rcflyinghokie]

Okay, THAT explains a lot! But what do I do about the tenths of a foot per second? Trim them out with the RCS after the burn?


Yeah, no mention of that in the checklists.

Wasn't mentioned in the actual procedures either, but as indy91 stated, earth orbit scaling is to 1fps instead of 0.1fps in AGS.

 

[MrFickles]

I'm guessing it wouldn't be on the checklist if they trained only with the earth orbit AGS

 

[rcflyinghokie]

I'm guessing it wouldn't be on the checklist if they trained only with the earth orbit AGS

Well its in the AGS documentation and pretty well alluded to. But not explicitly stated outside of the AGS software manual.

Its also not technically an "earth orbit AGS." Any AGS software used in earth orbit (intentionally or due to an alternate mission) had to be rescaled the same way.

 

[Max-Q]

Now I am in P34 waiting for marks, and I randomly get a program alarm light with a flashing 05 09 showing 00525 in R1 and 00000 in R2 & R3.

 

[rcflyinghokie]

Now I am in P34 waiting for marks, and I randomly get a program alarm light with a flashing 05 09 showing 00525 in R1 and 00000 in R2 & R3.

This means either the CM is not where the computer thinks it is (bad state vector) or you have a side lobe lock on, hard to tell which without seeing myself.

 

[Max-Q]

Here in a scenario
If it is a bad state vector, is that fixable?