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Project Apollo - NASSP 6.4.3 released!
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Meadville Space Center
Project Apollo - NASSP
Project Apollo - NASSP Development
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Tschachim
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Swatch
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IMFD and VAGC.
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Topic: IMFD and VAGC. (Read 4628 times)
Christophe
Project Team Member
Hero Member
Posts: 1072
Re: IMFD and VAGC.
«
Reply #15 on:
September 18, 2006, 04:30:44 AM »
Here are some good an bad news:
I tested the new IMFD for TLI and it seems to be more accurate than the previous version. Now you can compute a burn to establish on a free return trajectory, even o Apollo 8. It's not easy since you have to be very carefull with TEJ and TIN.
I performed the burn using auto burn to restart the SIVB, associated with P47 for the AGC to monitor the burn.
All worked well until I decided to do the first MCC using IMFD to compute the delta V's and AGC to perform the burn. As soon as I entered the delta V's into the AGC P30, the disky crashed during the iteration: In fact, after one hour, the iteration wasn't yet complete!, with the COMP ACTY light still on.
May be was it because I didn't use the P47 right. It is told in the check that the P47 has to be turned on just before the burn and terminated as soon as possible. Since I've forgotten that, I enabled the P47 about one hour before TLI and let it run a long while after. May be that confused the AGC?
I guess there still is lot of work with the vAGC to be reliable away from low earth orbit...
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Tschachim
Project Apollo - NASSP
Administrator
Hero Member
Posts: 3687
nassp.sf.net
Re: IMFD and VAGC.
«
Reply #16 on:
September 18, 2006, 10:24:37 AM »
Hi Christophe,
thanks a lot for doing and reporting the test flight results! I was wondering how you do a TLI burn with IMFD auto burn and the VAGC, I assume you're "cheating" and are using the VAGC with REALISM 0, so you have manual SIVB engine control?
Anyway, during P47 the AGC is in Average G mode, so it measures accelerations actually. So if you are in P47 a long time, Orbiter's errors and "fluctuations" could sum up, so it's a good idea to keep the time as short as possible. Additionally do
not
use time acceleration at all during P47, otherwise you'll get very "rough" accelerations from Orbiter and your state vector gets messed up.
It would be quite interesting what orbit (V82) and what position (P21) the AGC reports after the TLI burn. Also it's perhaps worth a try to update the AGC state vector after the burn, if this is already possible with irnenginer's Excels.
Cheers
Tschachim
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Christophe
Project Team Member
Hero Member
Posts: 1072
Re: IMFD and VAGC.
«
Reply #17 on:
September 18, 2006, 12:09:34 PM »
Hi Tschachim!
I concluded almost exactly the same.
As far as the TLI is concerned I just used the IMFD autoburn to take the control of the SIVB. That worked very well and I loaded the P47 into the DSKY to monitor the burn. May be it worth to mention I used a stock home made scenario from the Apollo 8 vAGC default one. I just checked for the realism level but the line seemed to have disappeared from the scenario file(?) so I don't know.
I agree with you: I think I messed up the state vector while staying too long in P47. And, although I did not exactly remember, I probably used time accelearation meanwhile! I'll redo the test this evening and will enable the P47 just the time for the burn. If the AGC will jam again I'll try a state vector update right after the TLI.
Quote
It would be quite interesting what orbit (V82) and what position (P21) the AGC reports after the TLI burn.
I tried V82 too after a relaunched of the saved scenario. It was the same issue than for the P30: The CMC ran into an endless iteration and jammed in "comp acty" light on. I didn't try P21.
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Tschachim
Project Apollo - NASSP
Administrator
Hero Member
Posts: 3687
nassp.sf.net
Re: IMFD and VAGC.
«
Reply #18 on:
September 18, 2006, 12:34:10 PM »
Hi Christophe,
because of the SIVB manual control and REALISM level: No REALISM line in the scenario means Standard realism level. I just checked the code and in case of the VAGC you always have manual SIVB control, independed of the REALISM setting. I feel a little bit stupid, now I can remember that I did that change, I just forgot it completely...
Cheers
Tschachim
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Christophe
Project Team Member
Hero Member
Posts: 1072
Re: IMFD and VAGC.
«
Reply #19 on:
September 18, 2006, 02:38:47 PM »
No matter Tschachim!
You just made me a bit afraid about my scenario...
I just redid the test, this time by activating P47 the minimum time and with no time acceleration of course.
Result: Right after TLI, V82 worked well and I thought I was on the right way. Unfortunately I experienced the same trouble with P30.
Now I'm about to try to update the the state vector via P27 and I'll see if that fix the problem.
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Christophe
Project Team Member
Hero Member
Posts: 1072
Re: IMFD and VAGC.
«
Reply #20 on:
September 18, 2006, 03:13:49 PM »
No dice
Even the state vector update crashed.
At the end of the P27 (via V71) when time to V33E, the AGC runs into another endless iteration and jams.
It seems that it doesn't accept such a state vector, relative to a high eccentricity orbit.
Of course I have no clue why. It's far beyond my skill.
Worse: IMFD seems to be unable to take over control of the CSM. Nor RCS neither SPS. I'm lost into the space.
Bad mood...
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Zachstar
Sr. Member
Posts: 317
Is it Star Trek?
Re: IMFD and VAGC.
«
Reply #21 on:
September 18, 2006, 05:26:03 PM »
Well let me cheer you up.
Off topic but..
I launched the Space Shuttle Challenger with 2 ANIK Sats designed for GeoSync Orbit. (STS-Payloads rock)
What do I do instead? Send one to the moon of course!!
So I let the PAM-D do its thing then I do another burn with the AP motor. This long burn takes me from the earth to the moon.
2 small course correction burns later (The Map Program really helps me do this) And I was heading for a very nice arrival low point of 111Km
A long burn later and im in a 0 ECC lunar orbit low enough to really look at awe of Moon 3D!
IMFD really helps make it possible and now with the Apollo AGC elements I am starting to REALLY get interested in NASSP 7.
Thanks alot guys!!
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Christophe
Project Team Member
Hero Member
Posts: 1072
Re: IMFD and VAGC.
«
Reply #22 on:
September 18, 2006, 06:10:30 PM »
Quote from: Zachstar
IMFD really helps make it possible and now with the Apollo AGC elements I am starting to REALLY get interested in NASSP 7.
That's exactly what I was guessing a few posts above!
I'm pretty sure the combination of IMFD and vAGC will drain a lot of people to interest in NASSP.
And Zachstar: congratulation for your trip around the moon, even if you are a space hijacker...
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Rex
Full Member
Posts: 14
Re: IMFD and VAGC.
«
Reply #23 on:
September 30, 2010, 09:29:09 PM »
hey everyone rex here; and yes i know this thread has been dead for 4yrs and 12 days but instead of starting a new one that deals with the same thing i figured id revive the thread
now down to the point:
today I was doing all kinds of research on the Apollo Program and got to wondering how the astronauts got from the CM to the LM [or LEM if you prefer] I mean where did the docking probe go? so i loaded up the Apollo 9 quick launch got into orbit then when i was in orbit after about 3 orbits i decided to change my orbit to a 300km ciculuar orbit, so i thrusted around so that the CSM was pointed at my direction of travel then pitched up to about 60deg from my line of travel /_ sorta like that underscore is my orbit and the slash is my pitch and fired up the engines i killed continous thrust at about 290km and used burst thrust [emulating translational fireing of the SM RCS] I achived an alt of 300.7km then i switched on IMFD entered the orbit circ. part of it and hit autoburn and it was going good the engines fired for a litle bit then it went into attiude mode and for a whole orbit it was still in attiude mode and the orbit was nowhere near circ.
now after reading a lot of threads on here i've come up with an idea, instead of using the base IMFD with Apollo p30 [yea even with that on i got a main engine fire - which shutdown for attitude adjustment and spent another orbit in attitude mode] someone should create an project Apollo nassp specific mfd so if someone wanted to they could circularize their orbit
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