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Virtual AGC
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movieman



Joined: 25 Nov 2004
Posts: 1018

PostPosted: Thu Feb 23, 2006 1:53 pm    Post subject: Reply with quote

Quote:
It hit it's target almost dead on. The error was 20 NM.


Do we have an aircraft carrier we can put at the planned landing site, to see how close we're getting on re-entry?

I seem to remember one of the astronauts saying that on the early Apollo missions the captain parked the carrier exactly where the capsule was supposed to land, but by the end the computer was getting so accurate that they moved the aircraft carrier away from there just in case Smile.
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dseagrav



Joined: 03 Dec 2005
Posts: 216

PostPosted: Thu Feb 23, 2006 2:16 pm    Post subject: Reply with quote

I checked in what I have, someone do a build and tell me if it wins or loses.

There are two caveats:

#1, there are now two seperate RCSes for the CM, so if you have a scenario with a CM by itself (no SM), you will have no fuel in CM RCS System B unless you modify your scenario. The two RCSes work independently of one another and you can turn them off and on at will.

#2, the RCS exhausts are purposely reduced to bright dots at the position of the thruster itself. This makes it easier to see which jets the AGC is using, and also will make it easier for someone who is better at screwing with objects in 3D space than I to fix the thruster positions to match the texture and aim them. I can go back and do it myself later if nobody wants to.
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Tschachim



Joined: 26 Nov 2004
Posts: 1272

PostPosted: Thu Feb 23, 2006 2:22 pm    Post subject: Reply with quote

Quote:
Do we have an aircraft carrier we can put at the planned landing site, to see how close we're getting on re-entry?

There's a USS Hornet made by Kev Shanow here: http://www.orbithangar.com/searchid.cfm?ID=1474 and a USS Iwo Jima in Saturn V's Apollo 10 scenarios: http://www.orbithangar.com/searchid.cfm?ID=1470 , but we'd have to ask the authors if we are allowed to use/distribute that.

Cheers
Tschachim
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irnenginer



Joined: 29 Jan 2006
Posts: 64

PostPosted: Thu Feb 23, 2006 4:25 pm    Post subject: Reply with quote

There is a P37 (return to earth) which can be used to set up reentry. It allows you to control the entry angle.

The angle depends on whether your coming from a earth orbit or from the moon. I can find the exact values but I recall it is between 5 and 7 degrees.

When returning from orbital flight you should see skips. They probably did that kind of entry with A7. The only other orbital mission was 9. Which if I recall used a lunar entry trajectory on reentry.

But I could be wrong, I said the CM RCS couldnt control jets seperatly. Embarassed
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dseagrav



Joined: 03 Dec 2005
Posts: 216

PostPosted: Thu Feb 23, 2006 4:36 pm    Post subject: Reply with quote

irnenginer wrote:
There is a P37 (return to earth) which can be used to set up reentry. It allows you to control the entry angle.

Oooh, I didn't even know that. I've just been pointing the thing retrograde and guessing. I'll have to play with that when I get home.
Quote:
But I could be wrong, I said the CM RCS couldnt control jets seperatly.

It's OK, I only found out by reading the DAP documentation while doublechecking things. ^_^
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Toadtal



Joined: 24 Dec 2005
Posts: 69

PostPosted: Fri Feb 24, 2006 2:54 am    Post subject: Reply with quote

I though P37 is using the dsky to change orbit altitude
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dseagrav



Joined: 03 Dec 2005
Posts: 216

PostPosted: Fri Feb 24, 2006 3:48 am    Post subject: Reply with quote

Eh, it's definetely a re-entry program - I'm figuring out how to use it now.
I have it set up and it gave me a burn solution, and I'm going to see how far off it is.
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Toadtal



Joined: 24 Dec 2005
Posts: 69

PostPosted: Fri Feb 24, 2006 4:28 am    Post subject: Reply with quote

can u post the procedure u used to get it to work
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dseagrav



Joined: 03 Dec 2005
Posts: 216

PostPosted: Fri Feb 24, 2006 4:40 am    Post subject: Reply with quote

Toadtal wrote:
can u post the procedure u used to get it to work

I will when it works. The first attempt failed outright, the second one didn't make it low enough for atmospheric braking to be a factor.
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Toadtal



Joined: 24 Dec 2005
Posts: 69

PostPosted: Fri Feb 24, 2006 4:59 am    Post subject: Reply with quote

i tried to run program 37 with v37n37e then it flashes two values which are target apa and pea then pro and then it computes a time to burn and then i let the program run out and it just has me in and orbit of the targeted apa and pea
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irnenginer



Joined: 29 Jan 2006
Posts: 64

PostPosted: Fri Feb 24, 2006 5:43 am    Post subject: Reply with quote

Just so happens I was working on P37
Quote:
1 V37E37E P37
FV06N33 Specify GET of ignition V25E to change
R1:XXXXX Hrs
R2:000XX Min
R3:0XXXX .01sec
PRO
2 FV06N60 Specify VPRED and GAMMA V22E and V23E
R2:XXXXX FPS Maximum ?V
R3:XXXXX .01 degree GAMMA Flight path angle between inertial velocity vector and local horizon at entry interface ”400,000 ft”. If zero the middle of the reentry corridor will be chosen.
PRO Computation can take some time
Possible Program Alarms:

605 Could Not Converge
612 State Vector in Moon Sphere of influence
613 Desired Flight Path Not Reached

3 FV06N61 Verify These Values V32E to recycle
R1:YYYYY Impact LAT .01 degrees +North –South
R2:YYYYY Impact LONG .01 degrees +East -West
PRO or V32E PRO to Proceed. V32E to recycle
4 FV06N39 Verify Time from Burn to Entry Interface (400,000 ft)
R1:YYYYY Hrs
R2:YYYYY Min
R3:YYYYY .01 sec
PRO or V32E PRO to Proceed. V32E to recycle
5 FV06N60 Verify VPRED and GAMMA
R2:XXXXX FPS Maximum ?V
R3:XXXXX .01 degree GAMMA Flight path angle between inertial velocity vector and local horizon at entry interface ”400,000 ft”. If zero the middle of the reentry corridor will be chosen.
PRO or V32E PRO to Proceed. V32E to recycle
6 FV06N81 Verify ?V Burn Parameters
R1:YYYYY ?VX .1 FPS
R2:YYYYY ?VY .1 FPS
R3:YYYYY ?VZ .1 FPS
PRO or V32E PRO to Proceed. V32E to recycle
7 Repeat from 3 1 iteration to refine burn parameters
8 FV04N06 Request Option
R1:00007 Specify Propulsion System 1:SPS 2:RCS V22E to change. Value specified is AGC recommended value
PRO
9 FV06N33 Verify Time of Ignition
R1:YYYYY Hrs
R2:YYYYY Min
R3:YYYYY .01 sec
PRO
10 FV16N45 Verify Parameters
R1:YYBYY MRK CTS (Not Needed for this procedure)
R2:YYBYY Min sec from TIG
R3:YYYYY MG .01 degree angle at TIG
PRO
11 FV37 Enter 00E for POOH,40E for SPS burn, 41E for RCS Burn

I would suggest a value of max delta v to 2000fps and a gamma of -5.1 degrees. I tested with those values and got no errors procedded to P40. Make sure you have the DAP up and running for P40.

This format is close what I have been putting together for documentation. I will probably be commiting these documents to CVS soon. I think that will be the best way since some of these procedures (as you can see) get long in a hurry. The notation should be clear, let me know of any feedback.
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movieman



Joined: 25 Nov 2004
Posts: 1018

PostPosted: Fri Feb 24, 2006 11:42 am    Post subject: Reply with quote

BTW, the Apollo 15 Delco manual says that in Prog 67 you put Spacecraft Control to SCS and then press PRO after the parachutes deploy: that should go to VERB 37 to select a new program.
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dseagrav



Joined: 03 Dec 2005
Posts: 216

PostPosted: Fri Feb 24, 2006 4:12 pm    Post subject: Reply with quote

irnenginer wrote:
Just so happens I was working on P37

When you were testing this, did you run it in earth orbit, or after a TEI burn?
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irnenginer



Joined: 29 Jan 2006
Posts: 64

PostPosted: Sat Feb 25, 2006 3:01 am    Post subject: Reply with quote

I was in earth orbit.
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dseagrav



Joined: 03 Dec 2005
Posts: 216

PostPosted: Sat Feb 25, 2006 3:04 am    Post subject: Reply with quote

How far from current was the burn time you used?

When I try this from orbit, I get strange results, usually the capsule ending up too high for atmospheric braking and stuck in orbit, or vertical burns that put the capsule thousands of km away from the target point.

Oh, and are you using positive or negative numbers for the DV and angle?
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