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Project Apollo Beta 7.0 released!
http://nassp.sf.net/wiki/Installation
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Author Topic: CMC frozen on STBY / LVDC not achieving orbit  (Read 801 times)
MrFickles
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« on: August 28, 2017, 01:11:00 PM »

Hi guys, I've not flown NASSP for a couple of months now, decided to fly Apollo 7 all over again with the latest release.

I've encountered 2 different problems, one each on Orbiter 2010 and 2016.

On Orbiter 2010 (latest commit on Orbiter 2010 branch), the CMC shows a only a STBY light and becomes totally unresponsive after the light test on the startup checklist. It still shows STBY and nothing else with the CBs pulled. Same issue with Apollo 8.

On Orbiter 2016 (release 693), LVDC will not put the spacecraft into a stable orbit, it puts me into a 160-something by -70-something orbit. Not caused by propellant shortage, scenario editor confirms that there is propellant in the S-IVB after cutoff.
Apollo 8 LVDC works as intended, putting the spacecraft into a near circular 100-something orbit.

Scenarios used are,
Orbiter 2010:
Apollo 7/8 MCC - Launch (1st & 2nd attachments)

Orbiter 2016:
Apollo 7/8 MCC - Launch (3rd & 4th attachments)
Apollo 7 - 01 - Before Launch T-60s
Apollo 8 - 02 - Before Launch T-60s

* Apollo 7 MCC - Launch.scn (5.09 KB - downloaded 47 times.)
* Apollo 8 MCC - Launch.scn (10.95 KB - downloaded 48 times.)
* Apollo 7 MCC - Launch.scn (5.06 KB - downloaded 52 times.)
* Apollo 8 MCC - Launch.scn (10.9 KB - downloaded 50 times.)
* Apollo 7 - 01 - Before Launch T-60s.scn (96.04 KB - downloaded 47 times.)
* Apollo 8 - 02 - Before Launch T-60s.scn (95.66 KB - downloaded 43 times.)
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indy91
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« Reply #1 on: August 28, 2017, 01:55:31 PM »

The Orbiter 2016 issue with Apollo 7 is easily explained. The Orbiter terrain at LC-34 (where Apollo 7 launched) is not flat. That means the Saturn IB will not point straight up at launch. And that messes up the alignment of the launch vehicle IMU at liftoff. Bad alignment during the launch phase means bad orbital insertion. This terrain issue is something we can fix in NASSP, essentially "overriding" the terrain of Orbiter 2016 in that area. But nobody has done that yet. So essentially, launching Apollo 7 is currently broken in NASSP 8.0.

About the CMC issue, is it happening to you in the T-4 hours launch scenarios? So, when you close the circuit breakers for the AGC you immediately get the STBY light? There were a few changes to the saving format for the AGC in scenarios which usually lead to the AGC being stuck in standby. But that should only be the case for old quicksaves, not the scenarios that come with the NASSP releases. Any scenario you have previously saved could be affected.
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MrFickles
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« Reply #2 on: August 28, 2017, 09:28:30 PM »

Makes sense, I did notice how the FDAI wasn't exactly at 90 degrees pitch after P01.

As for the CMC issue, my saved scenarios seem to work fine, as all of them are at least at T-30min. It's the  T-4h scenarios that come with the latest NASSP release that have this issue. The old scenario, Apollo 7 Virtual AGC LVDC++ MCC - Launch.scn, has no such issue even when used on the newer release.
Is it safe to use the old scenario with the newer NASSP release, or have there been significant changes made to NASSP between the two releases such that I may encounter other issues down the road?
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indy91
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« Reply #3 on: August 29, 2017, 05:44:39 AM »

Makes sense, I did notice how the FDAI wasn't exactly at 90 degrees pitch after P01.

The FDAI would have shown 90, because that is the pitch angle that the CMC torqued the IMU to for launch, not the actual pitch angle of the launch vehicle. If you take a look at the HUD view outside of the cockpit (press F8 twice) then you will notice that the Saturn IB points to about 88 pitch and 1 yaw. That will be enough of a misalignment to cause the insertion issues.

Quote
As for the CMC issue, my saved scenarios seem to work fine, as all of them are at least at T-30min. It's the  T-4h scenarios that come with the latest NASSP release that have this issue. The old scenario, Apollo 7 Virtual AGC LVDC++ MCC - Launch.scn, has no such issue even when used on the newer release.

I am a bit confused which scenarios you use with which NASSP version. Are you using the latest scenarios from the NASSP 8.0 Alpha releases with the Orbiter 2010 branch? Or did you try it with the NASSP 7.0 release version? The NASSP 7.0 release and the Orbiter 2010 branch are not the same thing.

I tried the Orbiter 2010 branch, but the T-4h scenarios that come with it work perfectly fine. The Orbiter 2010 branch is a bit of an experimental branch which hasn't been updated in a while. It was only created so we could test launches, when that wasn't possible yet at the time in NASSP 8.0 due to Orbiter 2016 changes. I might give it another update, so that all the latest changes for NASSP 8.0 can be used in Orbiter 2010.

Quote
Is it safe to use the old scenario with the newer NASSP release, or have there been significant changes made to NASSP between the two releases such that I may encounter other issues down the road?

In general, yes. You can use older scenarios. If you encounter a scenario with a permanent STBY light on then the AGC save state is broken, due to the saving format changes I mentioned. It is possible to fix that by editing the scenario, but it is a bit of a hassle. If your RCS seems to be broken in an on-orbit scenario then you have to activate the "RCS Enable/Disable" relays again. These simulated relays have been moved internally in NASSP, so they can appear as off in older scenarios. All you have to do is close the SECS circuit breakers on panel 8 and then switch RCS CMD to On on panel 2. For the CSM these are usually the only issues in older scenarios.

All the Apollo 7 and 8 scenarios that you can find under "Project Apollo - NASSP\Apollo - Historical Missions" have been mostly updated with the NASSP changes. So at least the CMC problems shouldn't happen in those. If your own older scenarios won't work, then you could try one of these scenarios instead of flying a whole mission from scratch again.
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MrFickles
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« Reply #4 on: August 29, 2017, 01:59:11 PM »

I am a bit confused which scenarios you use with which NASSP version. Are you using the latest scenarios from the NASSP 8.0 Alpha releases with the Orbiter 2010 branch? Or did you try it with the NASSP 7.0 release version? The NASSP 7.0 release and the Orbiter 2010 branch are not the same thing.

Alright, here's the breakdown of what scenarios I'm using.

The scenarios packaged with NASSP 7.0 release version (master branch) works on the latest release on both NASSP 7.0 and NASSP 8.0

The scenarios packaged with NASSP 8.0 Alpha doesn't work on either version.

The scenarios that are not working are attached above. They are the 1st and 2nd files listed.
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indy91
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« Reply #5 on: August 30, 2017, 04:15:32 AM »

The first two scenarios you have attached are not the current NASSP 8.0 scenarios. As you said in your first post, the 3rd and 4th scenarios are from NASSP 8.0. And those should work in NASSP 8.0 with Orbiter 2016. Are you sure you haven't copied scenarios from one folder to another one time too often?  Very Happy

Copying launch scenarios from one NASSP version to another will never do you any good. Those initial scenarios are a bit different from scenarios you save throughout the mission. They only have the minimum number of parameters, so that they can be changed more easily. One difference between the two "Apollo 7 MCC - Launch.scn" as an example. The older version of the scenario does not have the DAP configuration as part of the padload for the CMC. That was done in NASSP code instead, when the CMC is loaded for the first time. Now the DAP initialization is done by loading the parameters in the launch scenario. So the older version of the scenario will give you trouble in the current NASSP 8.0 Alpha version. Once the CMC was started for the first time the full AGC memory is always saved, so at that point there won't be a difference between NASSP versions. So later scenarios are more interchangable between NASSP versions than the T-4h launch scenarios. I hope that clarifies my previous statement about using scenarios from older NASSP versions.

I really don't see how the T-4 hours scenarios could have the STBY light issue. The CMC isn't even on at that point. When you close the circuit breakers you will get a restart and program alarm, but not standby mode. The T-60s scenarios are another story. There you can be accidentally in standby mode due to the AGC saving format change I mentioned.
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