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Author Topic: Apollo 11 vAGC launch problem  (Read 7031 times)
AH
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« on: April 09, 2012, 08:36:27 AM »

Hello

I'm hoping someone can help me out again.

I've recently atarted trying the Apollo 11 vAGC scenario. Everything goes perfectly by the checklist until about 2 minutes 30 seconds after launch, just before staging, when the rocket goes completely haywire - at exactly the same time, in exactly the same way; PROG alarm on the computer, spinning and tumbling trajectory, smashing sounds, the whole works.   Gloomy

I've repeated the scenario several times, to the point where I'm running through the Prelaunch vAGC checklist in my sleep  ROTFL, but the same thing happens every single time. I'm certain I'm following the checklist correctly, and all the numbers seem fine, but then disaster. Could some very nice person please help me figure out what's going wrong?  What?

Cheers

AH
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retro
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« Reply #1 on: April 10, 2012, 11:19:17 AM »

 Do you have the limited fuel checked in  parameters ?
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AH
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« Reply #2 on: April 13, 2012, 05:00:35 PM »

Hi

I don't think so (i'm travelling and away from my home computer for a bit); i think i had it on unlimited fuel from trying out manouevers in Apollo 8 vAGC.

The problem seems to be that the stack begins pitching over as per usual, but keeps on pitching down, too far and too fast, until everything goes horribly wrong...

best

AH
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eddievhfan1984
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« Reply #3 on: April 13, 2012, 06:58:35 PM »

The closest thing I can think of--do you use time accel during launch, or do you keep it at realtime? Namely because I've have similar things occur in orbit, when I crank the speed up to 10x or more--PROG alarm, frozen DSKY, total inability to use CMC.
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drewhogue
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« Reply #4 on: April 14, 2012, 09:51:17 AM »

I don't think the vAGC is fully functional in any scenarios except Apollo 7 and 8.  I could be wrong, i've been away for some time.
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AH
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« Reply #5 on: April 15, 2012, 01:23:45 PM »

Hi

I do use time acceleration up to 10x to skip time lapses in the checklists, though I might do it in real time at the next attempt just to see what happens. Better keep a good book handy  ROTFL

I was sure I'd seen posts on this forum discussing successful Apollo 11 vAGC missions, though I might be wrong.

Best

AH

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eddievhfan1984
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« Reply #6 on: April 15, 2012, 04:32:20 PM »

Well, successful launches, but they've decided to improve the IGM code to get more accurate insertion orbits, and that work may be limited to 7 and 8 (the IGM mode for Saturn guidance engages just after S-IC staging, IIRC.
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bg114
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« Reply #7 on: April 16, 2012, 02:54:00 AM »

I made into orbit just fine. Which checklist are you using? I'm using Apollo 11 flightplan VAGC.
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meik84
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« Reply #8 on: April 16, 2012, 04:06:02 AM »

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but they've decided to improve the IGM code to get more accurate insertion orbits, and that work may be limited to 7 and 8
Oh, I haven't commited anything yet (I don't even have a CVS account yet), so this can't be the cause. Even the 'old' LVDC++ code is only activated when you put the appropiate command in the .scn file. If not, the normal code is used. And no, the LVDC++ will not be limited to Apollo 8; a Saturn V is a Saturn V, whether it carries 'Columbia' and 'Eagle' or 'Charlie Brown' and 'Snoopy'. The only difference is the target load for LEO and (if carried out) TLI.
To the problem: the first thing that catches my eye are the missing empty and fuel masses of the Saturn V in the .scn file. This can be a problem, I don't know how far this is absorbed in the code.
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Tschachim
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« Reply #9 on: April 16, 2012, 04:34:07 AM »

I don't even have a CVS account yet

Do you want CVS access? If yes please PM me your SourceForge user name.  Happy

Cheers
Tschachim
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eddievhfan1984
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« Reply #10 on: April 16, 2012, 05:13:29 AM »

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but they've decided to improve the IGM code to get more accurate insertion orbits, and that work may be limited to 7 and 8
Oh, I haven't commited anything yet (I don't even have a CVS account yet), so this can't be the cause. Even the 'old' LVDC++ code is only activated when you put the appropiate command in the .scn file. If not, the normal code is used. And no, the LVDC++ will not be limited to Apollo 8; a Saturn V is a Saturn V, whether it carries 'Columbia' and 'Eagle' or 'Charlie Brown' and 'Snoopy'. The only difference is the target load for LEO and (if carried out) TLI.
To the problem: the first thing that catches my eye are the missing empty and fuel masses of the Saturn V in the .scn file. This can be a problem, I don't know how far this is absorbed in the code.

Well, I meant applying it to only the 7 and 8 scenarios, but I get your point. I had just been thinking about it, because his problems don't start until just prior to S-IC staging, and until that point, the spacecraft just follows a simple pitch vs. time plot, right?
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AH
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« Reply #11 on: April 16, 2012, 07:15:16 AM »

@ bg114

I've used both the prelaunch vAGC checklist from the website and the checklist in the Project Apollo MFD, but I thought that the actual launch information was preloaded into the IU, and that the checklist configured the ship for flight and orbit, so I'm not even sure how a mistake in executing the checklist could lead to the results I've been seeing  Confused

AH
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meik84
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« Reply #12 on: April 16, 2012, 09:42:53 AM »

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Do you want CVS access? If yes please PM me your SourceForge user name.
I wanted to wait with that till I got that LVDC++-stuff at least orbit capable, but as we're just talking about it: forum & sourceforge name are identical. Wink
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because his problems don't start until just prior to S-IC staging, and until that point, the spacecraft just follows a simple pitch vs. time plot, right?
Right. This could also be a cause of the trouble: the event times aren't set, too. I'm going to make a test flight and see whats wrong. No big problem thanks to automatic checklist execution. Wink

Edit: first investigations show that the CMC has the wrong launch azimuth. It is certain that this causes at least the PROG alarm and possible that it makes the Saturn go maverick. The LVDC++ took its azimuth from the CMC (until I kicked that off from the code Wink) -I strongly believe that the non-LVDC-code is doing the same.
@tschachim: which software do we use on the CMC for Apollo 11? If we'd use our good old friend (Colossus 249) this would be a matter of copy & paste...
« Last Edit: April 16, 2012, 12:12:21 PM by meik84 » Logged
Tschachim
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« Reply #13 on: April 17, 2012, 07:02:00 AM »

...forum & sourceforge name are identical.

You're added.  Happy To commit changes to CVS you need to redo your checkout: http://nassp.sourceforge.net/wiki/Introduction_to_CVS

@tschachim: which software do we use on the CMC for Apollo 11? If we'd use our good old friend (Colossus 249) this would be a matter of copy & paste...

Yep, Colossus 249

Cheers
Tschachim
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meik84
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« Reply #14 on: April 17, 2012, 01:42:19 PM »

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To commit changes to CVS you need to redo your checkout: http://nassp.sourceforge.net/wiki/Introduction_to_CVS
I.e. I have do a complete new NASSP checkout & orbiter installation? Great... Undecided
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