Apollo 9 Docked DPS Burn?

Wedge313

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Hello, just completed the docked DPS burn., a few questions...

I must have missed something when I set up the DAP? My first attempt didn't go well, and I noticed I had the DAP set to a LM-only 01002 for some reason. So, I had to re-do it with a LM/CSM config. What should the DAP be here?

Before the burn when I turn the Master Arm ON I get a 1210 alarm and a RESTART. This being Saturday, Steve Bales and Jack Garman had the day off, and I was stuck with the weekend crew. For lack of better guidance, we chose to say "we're GO" with the alarm, reset and pressed on with the burn. Seemed to work out ok, but not entirely clear what routines I'm running simultaneously.

After engine cut off, following the checklist I expected to see a F 16 85. Instead I was stuck with the F 06 40, followed by a F 99 40 as if the LGC wanted to do another burn? For lack of a better plan I just V37E00E'd out of it, but what am I doing wrong here?

Finally, throughout the simulation it's impossible for me to fully null the CSM/LM rates. I seem to get everything nulled, but then slowly the CSM/LM rates start to build up again. It doesn't look like I'm getting any thruster activity. Is this some effect of being in orbit as opposed to a trans-lunar coast? Will the CSM/LM ever reach some sort of equilibrium or just continue to slowly tumble?

Thanks
 

rcflyinghokie

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I must have missed something when I set up the DAP? My first attempt didn't go well, and I noticed I had the DAP set to a LM-only 01002 for some reason. So, I had to re-do it with a LM/CSM config. What should the DAP be here?
Yes you missed in the "DAP set gimbal throttle test" procedure, there is a comment there under the V48 that says use "1" for first powerup and "0" for second powerup.
This would make it so you have a LM/CSM config during the first powerup (docked DPS) and a LM config during the second powerup (rendezvous)
Before the burn when I turn the Master Arm ON I get a 1210 alarm and a RESTART. This being Saturday, Steve Bales and Jack Garman had the day off, and I was stuck with the weekend crew. For lack of better guidance, we chose to say "we're GO" with the alarm, reset and pressed on with the burn. Seemed to work out ok, but not entirely clear what routines I'm running simultaneously.
Hmm I don't think I have ever seen a 1210 on the docked DPS burn. Can you replicate it? There shouldn't be anything running other than P40 routines.

EDIT: Just talked to @indy91 he reminded me the LR spurious routine is running, so that plus low frames from switching vehicles can cause the computer to hiccup with a 1210.
After engine cut off, following the checklist I expected to see a F 16 85. Instead I was stuck with the F 06 40, followed by a F 99 40 as if the LGC wanted to do another burn? For lack of a better plan I just V37E00E'd out of it, but what am I doing wrong here?
You should have a 16 40 after you manually cutoff the DPS. Then you press PRO right after to get the 16 85.
Finally, throughout the simulation it's impossible for me to fully null the CSM/LM rates. I seem to get everything nulled, but then slowly the CSM/LM rates start to build up again. It doesn't look like I'm getting any thruster activity. Is this some effect of being in orbit as opposed to a trans-lunar coast? Will the CSM/LM ever reach some sort of equilibrium or just continue to slowly tumble?
Ah this is due to atmospheric drag hitting your vehicle which is flying perpendicular to the atmosphere. Even the actual Apollo 7 and 9 crews complained about this as well. This is totally normal behavior. You null rates as best you can but they will pick up again.
 
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Wedge313

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use "1" for first powerup and "0" for second powerup.
I saw that. I can't remember why, but for some reason "powerup" meant something else to me, and I thought I had "powered up" the LGC once before, so I went with "0". All I can figure is I wasn't fully caffeinated at the time.

On to a new issue... getting ready for SPS-5, running through the P52 I noticed my optics are acting weird. I started some troubleshooting, if I zero out the optics and then go back to CMC the optics don't stay at zero, they drive to 27000/30100. If I run a P52 option 3, the program will select the first star, then the optics will search for the star and then start circling around, liked it has no idea where to go. The problem seems to have cropped up just before my DPS burn, but I haven't figured out where exactly it happens or what I did to cause it.

Have you heard of/seen this before? Is there a quick easy fix? I've tried to retrace back to a good save point before the DPS burn to find what's happened, but no luck yet.

Thanks
 

rcflyinghokie

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I saw that. I can't remember why, but for some reason "powerup" meant something else to me, and I thought I had "powered up" the LGC once before, so I went with "0". All I can figure is I wasn't fully caffeinated at the time.
I know all too well the symptoms of lack of caffeine sips coffee
On to a new issue... getting ready for SPS-5, running through the P52 I noticed my optics are acting weird. I started some troubleshooting, if I zero out the optics and then go back to CMC the optics don't stay at zero, they drive to 27000/30100. If I run a P52 option 3, the program will select the first star, then the optics will search for the star and then start circling around, liked it has no idea where to go. The problem seems to have cropped up just before my DPS burn, but I haven't figured out where exactly it happens or what I did to cause it.

Have you heard of/seen this before? Is there a quick easy fix? I've tried to retrace back to a good save point before the DPS burn to find what's happened, but no luck yet.
Hmm the driving when out of zero we have seen before but the circling a star seems to be a new one. Are you sure its not just the spacecraft rates due to atmospheric drag?

A save file with this happening would help tremendously in seeing what's up here.
 

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Here's a save, this is at about 53+15, I started a P52 option 3 trying to troubleshoot.
 

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rcflyinghokie

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Whoa its circling! We are looking into it.

Also just a tip, when you arent doing a burn, configure your auto RCS switches to match your DAP (A/C or B/D roll) this will let you use SCS without using all 4 roll quads and using more fuel and having larger rates.

In P52, 2 jet roll att hold using SCS helps a lot for stabilizing the spacecraft
 

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The problem seems to be on the CMC software side. If I cause a restart with Verb 69 and then re-zero the optics the issue is gone. Something in the CMC software might be thinking it has to issue SPS thrust vector control commands instead of optics commands, they use the same interface. I bet during the docked DPS burn, where you proceed far into P40, something in the software got messed up, with flags or so. The artificial restart kind of fixes that by resetting many flags. During the docked DPS burn, what exactly did you do with the CMC near ignition. Did you maybe PRO before ignition instead of doing ENTR as the checklist says? Maybe the TVC DAP got switched on then and somehow it didn't switch back properly to driving the optics as normal.

Ultimately this could still be an NASSP issue, in the way it interacts with the AGC, causing a problem with the software. But there are real bugs, like this one:

Colossus anomaly 86, "If P40 is exited before TIG .4 sec. optics problem".

Sadly we only know the name of this issue, but there are some strange optics issues we have only observed on Apollo 7-9. So it could be CMC bugs instead of NASSP bugs.

Speaking of NASSP issues, something you also only get on Apollo 9 and earlier is a coarse align issue. In P52 option 1 and 2, the DSKY shows you new IMU gimbal angles (06 22). If you PRO too quickly on that display, specifically if the FDAI error needles are still being driven, then you the coarse alignment will fail and you get program alarms. This is an issue I finally recently figured out, it's a bug at the interface between the AGC emulator and NASSP. It's difficult to fix, so don't expect that any time soon. We just have to be patient on the 06 22 display in P52 for now...
 

Wedge313

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I bet during the docked DPS burn, where you proceed far into P40, something in the software got messed up, with flags or so.
I'll go back to a "good" save before the DPS burn. It would not surprise me that I messed up something either going into or coming out of the burn.

Thanks.
 

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I went back to a save point where the optics seemed to be working correctly and worked forward. Here's a save from 49+18. At this point I just completed the CSM P30. I have the optics zeroed, with the mode in CMC, and it's holding at zero.

Following the PAMFD checklist, I start P40, I get F 50 18 displayed, and hit ENTER. F50 25 is displayed with 00204 in R1.

The BMAGs are in Rate 2, SC CONT is CMC, CMC MODE to HOLD, still displaying the F 50 25 R1 00204.

At this point I moved down to watch the optics as I hit ENTER. There is a pause, and then as the F 06 40 is displayed the optics start driving to 27000/30100.

Out of curiosity I restarted the scenario from this save point and did a P52 option 3 just to see if the optics were working normally, and they were. After the P52 I again zeroed the optics and began P40 following the checklist, and it's at the point I hit ENTER the second time that the optics begin to drive.

So I'm not sure where I'm going off the rails. Does this save help you narrow down what I'm doing wrong?

Thanks.
 

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rcflyinghokie

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At this point I moved down to watch the optics as I hit ENTER. There is a pause, and then as the F 06 40 is displayed the optics start driving to 27000/30100.
Your optics shouldn't move while in zero though, hitting enter at this point in P40, the optics are sharing with the TVC so if the optics are not in zero and in CMC, they will drive.

This is one of the reasons why you should have them in zero before a burn and the current checklists reflect this based on our previous discussion on the matter.
 

Wedge313

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Your optics shouldn't move while in zero though, hitting enter at this point in P40, the optics are sharing with the TVC so if the optics are not in zero and in CMC, they will drive.

This is one of the reasons why you should have them in zero before a burn and the current checklists reflect this based on our previous discussion on the matter.
OK, I think I follow this.

While trying to track down the problem, I've purposely been leaving the optics in CMC to see what happens. But this is actually causing the optics problem when I run P40. If I leave the optics in ZERO, and the mode in MAN, the optics won't drive.

And I may have caused the original problem if prior to the DPS burn I didn't have the optics in ZERO?

It's entirely possible I had this switch in the wrong position. I'll go back and check.

Thanks.
 

rcflyinghokie

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And I may have caused the original problem if prior to the DPS burn I didn't have the optics in ZERO?
Possibly, but I bet its more a function of when P40 was exited or how it was used (pro vs enter and when they were pressed etc) with the switch not in zero.
 

Wedge313

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OK! (I think)...

Went through the docked DPS burn once more. Left the optics zero switch in zero, mode MAN (I guess that tells the CMC that during P40 "Thou shall not pass" commands to the optics). I believe I found an "ENTER" step in P40 I missed after the burn. As you thought, a procedural error on my part.

After the LM closeout, just out of curiosity I did a CSM P52 opt 3, and the optics functioned normally. So, I think you've got me through that issue.

Thanks for bearing with me. On to SPS-5.
 

rcflyinghokie

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OK! (I think)...

Went through the docked DPS burn once more. Left the optics zero switch in zero, mode MAN (I guess that tells the CMC that during P40 "Thou shall not pass" commands to the optics). I believe I found an "ENTER" step in P40 I missed after the burn. As you thought, a procedural error on my part.

After the LM closeout, just out of curiosity I did a CSM P52 opt 3, and the optics functioned normally. So, I think you've got me through that issue.

Thanks for bearing with me. On to SPS-5.
I would bet the issue was from the missed ENTER and the optics still wanted to be driven based on TVC commands. That could even be the bug @indy91 mentioned in the actual software.

In any case, looks like you are on your way! Oh, one other thing, be prepared for high residuals on SPS-5 ;)
 
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