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Author Topic: Apollo 7 Test Launch to MET 26:25  (Read 4151 times)
irnenginer
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« on: March 08, 2010, 03:07:15 PM »

I finalyl got a chance this weekend to fire up Apollo 7 and test out some of the (some not so new) features such as ORDEAL,SIVB takeover, sounds and Uplink to vagc improvements. I used the vagc scenario with auto checklist enabled, because I am lazy about launch switch flipping.  ROTFL

Some notes:
Insertion: Launch went very well and insertion was nominal. I did notice that post insertion the FDAI indicated about a 5 degree yaw from state vector error from the launch pad load. This remains a slight issue that was corrected with a SV update and P52 and did not effect any further part of the test.
OREDEAL operation: Played around with the modes and controls. Everything worked great and was very useful when piloting. Great Job.
S4B takeover per preliminary flightplan: again everything went as expected with no anomalies. CMC takeover and ORBrate of S4B were all very smooth.
State Vector updates including S4B: updated state vectors via MFD for both CSM and S4B. Verification with vAGC tracking using P20 should excellent tracking of stage at 1000km (using docking HUD to indicate S4B location). We may want to include some indication that when selecting a different source the SV will load into the "other vehicle" slot. It was unclear to me until I did a run with CM UPLINK at BLOCK to check where the upload went in that case.

The one issue: The first phasing maneuver set at 7.5ft/s. I knew from earlier runs that is too much delta V in orbiter. I did about 5ft/s but still ended up about 1000km from SIVB at MET 24:00 when I should be about 93km. The orbits at that point were pretty far off as well. I simulated the 26:25 SPS burn with parameters listed in the flightplan which went as planed but the burn would never get me to the right location for rendezvous. I did not do a second phasing maneuver which might of corrected it somewhat. Also the S4B had a real good spin going after 24 hours (most of which at 10X time accel). I am going to play around with the burn some to see if the outcome can be closer.

The new soundtrack is great too.

Again great job on the latest work Thumbs Up
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kneecaps
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« Reply #1 on: March 08, 2010, 05:29:08 PM »

Quote
The first phasing maneuver set at 7.5ft/s

Any ideas why this is? I see this quite a lot. Atmospheric drag models? Differences in pertubations? Combination of many factors?

I can get DVs pretty close to the historical in STK...so I can only think that Orbiter is not calculating something to the required degree of accuracy?
« Last Edit: March 08, 2010, 05:48:06 PM by kneecaps » Logged

"Okay. As soon as we find the Earth, we will do it."
- Frank Borman, Apollo 8

Current Work: ?? What next??

Future Work:
I know the AGC pretty well so anything need doing there?

On Hold/Completed:
SPS TVC in P40 issues.
P11 FDAI Error Needles (98%) complete. Comitted. Working A7 scenario.
P06 AGC Standby. Concluded. It's done by the AGC PSU.
Got us a complete AOH Volume II
irnenginer
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« Reply #2 on: March 08, 2010, 07:12:55 PM »

My thought has been primarily atmospheric drag modeling of the S4B. I say this because the Mission report mentions that the reason a 2nd phasing maneuver was not needed was because the atmospheric drag on the S4B was higher then predicted, and the drag is not modeled in Orbiter. Secondary, as you mentioned something to do with orbiters orbital progression calculations, something where a small error is compounded.
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Tschachim
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« Reply #3 on: March 09, 2010, 06:05:04 AM »

I did notice that post insertion the FDAI indicated about a 5 degree yaw from state vector error from the launch pad load.

That was my "hack" of the Saturn IB launch autopilot to achieve a "historically more correct" insertion orbit inclination, I hope this is at least fine for now: http://www.ibiblio.org/mscorbit/mscforum/index.php?topic=1456.msg19192#msg19192

Also the S4B had a real good spin going after 24 hours (most of which at 10X time accel).

Hm, after separation, the S-IVB should hold its inertial attitude until the APS fuel is spent, was there fuel left at that time?

My thought has been primarily atmospheric drag modeling of the S4B.

Orbiter 2009/2010 does model atmospheric drag, perhaps it's worth to check if it behaves different there? Additionally, I'm not sure what the (real) S-IVB did after separation, perhaps there's a 2nd venting event and it changed its orbit again?
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irnenginer
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« Reply #4 on: March 09, 2010, 11:11:25 PM »

1. Should we update the launch heading in vAGC to match the launch?

2.It ran out of fuel somewhere between MET14:30 and MET 20:34. at 14:30 it was holding retro orbrate. Tanks 1 and 3 are empty at MET20:30.
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Tschachim
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« Reply #5 on: March 10, 2010, 07:40:21 AM »

1. Should we update the launch heading in vAGC to match the launch?

No, heading is fine, it's just the way my "hacked" autopilot is flying the Saturn IB after 1st stage separation, this will be fixed "automatically" when dseagrav's LVDC++ is ready.

2.It ran out of fuel somewhere between MET14:30 and MET 20:34. at 14:30 it was holding retro orbrate. Tanks 1 and 3 are empty at MET20:30.
Of course retro orbital rate, I wrote it here myself: http://www.ibiblio.org/mscorbit/mscforum/index.php?topic=1456.msg19293#msg19293  Duh!
I'm going to check this stuff when I'm done with separation, that might take some time as I'm once again busy with real life recently...

Cheers
Tschachim
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kneecaps
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« Reply #6 on: March 10, 2010, 03:15:16 PM »

My thought has been primarily atmospheric drag modeling of the S4B. I say this because the Mission report mentions that the reason a 2nd phasing maneuver was not needed was because the atmospheric drag on the S4B was higher then predicted, and the drag is not modeled in Orbiter. Secondary, as you mentioned something to do with orbiters orbital progression calculations, something where a small error is compounded.

Thanks, I'm going to try eliminating atmospheric drag from my models. It's frustrating not knowing the source of the errors. I'm going to look into exactly how orbiter is propagating things. I think I have to make my models work in the 'Orbiter' world rather than tuning them to the real world numbers. 
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"Okay. As soon as we find the Earth, we will do it."
- Frank Borman, Apollo 8

Current Work: ?? What next??

Future Work:
I know the AGC pretty well so anything need doing there?

On Hold/Completed:
SPS TVC in P40 issues.
P11 FDAI Error Needles (98%) complete. Comitted. Working A7 scenario.
P06 AGC Standby. Concluded. It's done by the AGC PSU.
Got us a complete AOH Volume II
Swatch
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jasonims
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« Reply #7 on: March 11, 2010, 12:27:17 AM »


Orbiter 2009/2010 does model atmospheric drag, perhaps it's worth to check if it behaves different there? Additionally, I'm not sure what the (real) S-IVB did after separation, perhaps there's a 2nd venting event and it changed its orbit again?

Tschachim, let me dig through some documents tonight... I'll post a synopsis for you when I'm done.
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My Project Apollo Work:
CM Visual
 -VC (~75% complete: texture work beginning again; mesh-78%; texture-70%)
Propulsion Particle Improvements (Focused on S1B right now, BETA 1.0 has been commited)
New Docking Method (~50% complete: research complete; coding partially completed, testing not underway)

Future Work:  (if it's here, it's deemed unnecessary to upcoming release)

Older Work:  (if it's here, it's fair game to whoever wants to improve)
EMS Implementation (committed: minor flaws, but groundwork is there, needs extensive testing)
EMS scrolls (committed: not refined, but usable)
SM Visual (committed: mesh-finished, texture-60%; possibly revisited in future)
J2 Texture (commited: room for improvement)
LRV (committed: mesh-finished, texture-90%; in future a ground up rebuild may be in order, but not on my plans)
Swatch
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jasonims
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« Reply #8 on: March 11, 2010, 03:31:51 AM »

All I could find about post-separation propulsive venting is as follows...

CM Sep               T+10,502.388

LH2 Tank Vent Valve Open      T+11,354.474
LH2 Tank Vent Valve Close      T+11,756.123

LH2 Tank Vent Valve Boost Close On   T+11,757.006
LH2 Tank Vent Valve Boost Close Off   T+11,763.355

Initiate SIVB/IU Retrograde with   T+11.818
   Local Horizontal Roll to
   Position 1 Up and Maintain
   Orbital Rate

Start Stage Control Sphere He Dump   T+11,853.958
LOX & LH2 Pump Seal Purge Off(?)   T+14,821.276

LH2 Tank Vent Valve Open      T+14,747.274
LH2 Tank Vent Valve Close      T+15,008.445

LH2 Tank Vent Valve Boost Close On   T+15,009.253
LH2 Tank Vent Valve BOost Close Off   T+15,015.711

Start Second Cold He Dump      T+16,216.948
Stage Control Sphere He Dump Off   T+14,821.276

LH2 Tank Vent Valve Open      T+17,035.855
LH2 Tank Vent Valve Close      T+17,341.721

LH2 Tank Vent Valve Boost Close On   T+17,341.621
LH2 Tank Vent Valve Boost Close Off   T+17,348,578

LH2 Tank Vent Valve Open      T+18,539.182
LH2 Tank Vent Valve Close      T+18,684,844

LH2 Tank Vent Valve Boost Close On   T+18,685.619
LH2 Tank Vent Valve Boost Close Off   T+18,721,358


I'm still trying to figure out what the LH2 Vent Valve Boost Close is referring to.   If I have time, I'll look into the propulsive capacity of the LH2 vent and He Dump.  No guarantees though... things are getting busy as we work to get the first Falcon 9 off the ground here.
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My Project Apollo Work:
CM Visual
 -VC (~75% complete: texture work beginning again; mesh-78%; texture-70%)
Propulsion Particle Improvements (Focused on S1B right now, BETA 1.0 has been commited)
New Docking Method (~50% complete: research complete; coding partially completed, testing not underway)

Future Work:  (if it's here, it's deemed unnecessary to upcoming release)

Older Work:  (if it's here, it's fair game to whoever wants to improve)
EMS Implementation (committed: minor flaws, but groundwork is there, needs extensive testing)
EMS scrolls (committed: not refined, but usable)
SM Visual (committed: mesh-finished, texture-60%; possibly revisited in future)
J2 Texture (commited: room for improvement)
LRV (committed: mesh-finished, texture-90%; in future a ground up rebuild may be in order, but not on my plans)
kneecaps
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« Reply #9 on: March 11, 2010, 04:19:19 PM »

Do we really need to know the precise details of the venting? We know the burns that were made to phase and rendezvous, so we know where the S-IVB WILL be in the future time at rendezvous. All that needs be done is make it 'vent' any way we need that satisfies this future rendezvous state?

 
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"Okay. As soon as we find the Earth, we will do it."
- Frank Borman, Apollo 8

Current Work: ?? What next??

Future Work:
I know the AGC pretty well so anything need doing there?

On Hold/Completed:
SPS TVC in P40 issues.
P11 FDAI Error Needles (98%) complete. Comitted. Working A7 scenario.
P06 AGC Standby. Concluded. It's done by the AGC PSU.
Got us a complete AOH Volume II
Tschachim
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« Reply #10 on: March 12, 2010, 05:48:19 AM »

Thanks Swatch! Now, the big question is if these ventings were propulsive ventings. AFAIR the mission report is a little bit vague about the post separation stuff, especially the S-IVB trajectory data, but perhaps someone could find some more info?  Happy

Good luck with the Falcon 9, Swatch, and please no "go fever"!  Wink

Cheers
Tschachim
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kerlix
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« Reply #11 on: May 20, 2010, 08:04:51 PM »

Dunno if this helps with all the questions on the propulsive effect of venting once in orbit. I'm not as technically proficient as most here so this may just be redundant data but I thought it might be interesting to look at. If it's already data known to developers, then i apologize, as I have no technical knowledge on the subject. What I found is just sort of a basic run-through of a launch and gives some specific, but mostly general, it seems, data. Maybe some of it will be useful. That's up to the developers to decide though.



http://www.apollosaturn.com/s5flight/sec2.htm
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