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Author Topic: Apollo 8 Testing using Apollo 8 Flightplan  (Read 12450 times)
Admiral
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« Reply #15 on: April 08, 2008, 06:26:45 AM »

I'm also in the middle of running the Apollo 8 mission.  I agree with Admiral.  Everything is very well done. 

I have not encountered any CMC problems however, but I'm only at MET 037:xx:xx.


God speed Reuben.  It will be good to hear how the mission progresses.  I am interested to hear if you start getting cmc issues as you leave Earth SOI up to LOI after state vector updates.

I am just about to restart Apollo 8 and work it through fully again after my first attempt ended in the astronauts burning up on reentry.  Since my first attempt, I've been spending time learning as much as I can on apollo and the agc, especially wrt g&n. I found it to be a steep learning to go from Orbiter low earth orbit missions to apollo using the vagc  straight away as a Apollo noob.  I hope the effort and practice will pay off in a safe return this time.

This time I will take notes to scrutinize the documentation to particularly look for documentation improvements.  I also aim to hit the documented mission timelines this time to help get my TEI right .  My apogee and perigee were heights were off at the moon (my circularization burns were short in the agc) so this would have affected the time of TEI as well and my 3rd mid course correction was off. I expect CMC issues for the reasons in the link of post 6, but this time am a bit more informed to give it another go.

The Admiral
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rwitham
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« Reply #16 on: April 08, 2008, 12:49:26 PM »

It would be an honor to join your team!!  Excited!  I certainly don't want to step on anyone's toes though.

I must confess that as a married father of two my time is a precious commodity, but I would very much like to help in any way that I can.  I think it would really help me understand what all the switches I'm toggling are really doing!

I would be very appreciative if someone would help me get started (i.e. create a working project, compiling/building, etc.).

Admiral, I will let you know how the mission progresses.

Reuben
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lassombra
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« Reply #17 on: April 08, 2008, 03:59:00 PM »

Reuben, I'll gladly work with you to get you started.

The first two steps are easy.  First, contact Tschachim here on the board and let him know you'd like to join the dev team.  Give him your sourceforge username (If you don't have one, register at sourceforge for one) so he can get you on the developer CVS.

Then follow the tutorial here to get VC++ 2005 express installed (If you want to use 2008 you can, the links are different, and the setup steps shown on that page should be irrelevant, as the 2008 installer sets up the variables and the platform sdk for you.)
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My current Project Apollo work:

Quickstart to the Moon initiative (Quickstart_to_the_Moon): Done through earth orbit.  Working on new method of calculating TLI.

Checklist Controller: 
  • MFD Interface 99%(Minor cleanup and future features remain)
  • Panel Interface 99%
  • Excel interface and logic 99%
  • LEM Event code.0%
  • DSKY Interface code. Framework complete, creating "buttons"
  Approximately 80% done. (Checklist Controller
Tschachim
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« Reply #18 on: April 08, 2008, 06:26:11 PM »

Hi Reuben, welcome to Project Apollo - NASSP!  Happy
Just follow Lassombra's instructions and I'll add you to the developers.

... Basically there is a big piece of the control loop is missing. There is a lot more to this piece and it really needs some work. If you like I will put together what I have figured out.

That sounds like a rather major problem, yes, please tell us more. Also a scenario shortly before such a burn starts would be great, such in case you have one at hand.  Happy

Cheers
Tschachim

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rwitham
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« Reply #19 on: April 14, 2008, 03:34:06 PM »

Admiral,

I have run into the same CMC issues.

Between 052:30:00 MET (after 3rd P23 of the mission ) and 060:00:00 MET I noticed I had a constant Comp Activity light come on.

The 2nd mid course correction had prog error 1520 or error 1202 alarms occur at execute.  P00 would not set and the comp Activity light stayed on.

I found this to be somewhere between hours MET 056:00:00 and MET 057:00:00.  Right around the time IMFD projected I would enter moon SOI.  Did you try to resolve the COMP ACTY problem prior to the 2nd MCC, and if not, is that why you received the 1520 and 1202 alarms?

To fix, I did a V36 CMC restart procedure.  This cleared the comp activity light error and I performed an IMU recovery.  Interestingly I was out of both Earth and Moon SOI according to IMFD so did not do a state vector update until I was in th Moon SOI well after the burn.

Where is the V36 procedure documented?  It's not in the Apollo 8 checklist.  How did you perform an IMU recovery?  Can you provide me with (or point me to) a procedure for that?

I am currently at MET 058:30:00.  I would like to resolve the COMP ACTY before the P52 alignment and 2nd MCC.

Thanks,
Reuben
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bluespace88
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« Reply #20 on: April 14, 2008, 03:37:19 PM »

V36 recovery is in the errors and failures tab of the mission checklist, under CMC restart..  From there, you'd go through P51 and P52 to realign the IMU, which was knocked out due to V36.
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Admiral
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« Reply #21 on: April 14, 2008, 04:14:53 PM »

Hi Reuben

I had more success with V96E later in the mission after I discovered it.  This would would terminate the comp activity light and I didn't have to realign the IMU.  You could try that.  V96 purpose is to provide a means of suspending state vector integration.  Then I went to V37E 00E successfully.

I initially didn't try to fix the comp activity light and this would have led to the 1202 and 1520 at 2nd MCC.

I got the V36 procedures where BlueDragon mentioned.  It just takes a while and by the time i left lunar orbit, V36 was proving to be ineffective.

Hope this helps

The Admiral
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bluespace88
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« Reply #22 on: April 14, 2008, 04:18:14 PM »

yeah, doing the entire IMU realignment takes a while.  I never tried V96, so thanks for pointing that out.
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rwitham
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« Reply #23 on: April 14, 2008, 04:35:24 PM »

Thank you BlueDragon and Admiral.

I reference a printed copy of the flight plan/checklists and neglected to print the "errors" page.  Embarassed

If V96 suspends state vector integration, is it necessary to do a state vector update after the CMC has been reset?

Thanks,
Reuben
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bluespace88
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« Reply #24 on: April 14, 2008, 04:45:07 PM »

yep.  According to the manual, going to V96 does not maintain state vectors, so you would need to update them when you bring it out of suspension.
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rwitham
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« Reply #25 on: April 14, 2008, 06:10:09 PM »

yep.  According to the manual, going to V96 does not maintain state vectors, so you would need to update them when you bring it out of suspension.

What manual are you speaking of?
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bluespace88
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« Reply #26 on: April 14, 2008, 06:11:28 PM »

The Colossus 249 manual
http://www.ibiblio.org/apollo/links.html
the R-577 one.
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irnenginer
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« Reply #27 on: April 14, 2008, 07:32:40 PM »

V96 suspends the current orbital integration cycle and goes back to POOH, which will eventually attempt another integration again. V96 does not invalidate anything like IMU alignment or the state vectors per se, though the state vectors will not get updated.

I missed the earlier email about lockup. I know exactly what that is about. I still need to commit changes to include solar position data into the AGC load(the current scenerio may also be missing an accurate lunar position as well). The AGC needs to know the position to correctly determine the state vectors when, particularly as orbiter shows, the sun and moon are dominate gravitationally.

For a while I managed to stay ahead of you guys on getting this sorta thing figured out. Now your passing me. Undecided

I was holding up committing until I got the TVC thing figured out. Since that will take a while I will go with what I have got, expect it in the next day or so.
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rwitham
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« Reply #28 on: April 15, 2008, 01:28:08 AM »

Hey irnenginer,

From where I sit, it looks as if you're still very far ahead of us.   Wink  Let me know if I can be of help on the TVC.  After re-reading your posts, it sounds like a PID control loop would do the trick.

Thanks for the link to the AGC manual, BlueDragon.  That is by far the most comprehensive source I've seen!

Reuben

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Admiral
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« Reply #29 on: April 15, 2008, 03:43:55 AM »

Yeah, the manual is like the nuts poker hand for the AGC.  You just can't beat it.

It will be interesting to see if you can do the state vector update after v96, Reuben, pre and post irnenginer's commit to see if this affects the comp activity light before you get to 2nd MCC.

The Admiral
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