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Space Shuttle - Bugfixes

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Re: Space Shuttle - Bugfixes

Postby GinGin » Wed Feb 24, 2021 3:26 pm

Nice, that will avoid some bad surprises with no drag chute after landing :)
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Re: Space Shuttle - Bugfixes

Postby Thorsten » Wed Feb 24, 2021 5:27 pm

Actually, somehow it seems impossible to follow procedure and avoid the SSME REPOSITION failure... so what are we missing?

I open the TVC valves, and prior to the de-orbit burn I start one APU and pressurize its system. Then I transit to 301. Error pops up.

So are we requiring /all/ APUs started to avoid the error? But two of them are only started following the de-orbit burn in the original checklist, and we definitely need to transit to 301 before the burn. Or am I missing something else?
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Re: Space Shuttle - Bugfixes

Postby GinGin » Wed Feb 24, 2021 5:48 pm

Yes, it requires at least two apu’s to powered the three ssme nozzles.
You are right for the one APU only before deorbit burn, I didn’t think about that.
So we can change the trigger form ops == 3 to mm == 304 to have the three apu available and tvc valves opened ?
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Re: Space Shuttle - Bugfixes

Postby Thorsten » Thu Feb 25, 2021 5:48 am

So we can change the trigger form ops == 3 to mm == 304 to have the three apu available and tvc valves opened ?


Let's try this then, yes.
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Re: Space Shuttle - Bugfixes

Postby Thorsten » Fri Feb 26, 2021 1:43 pm

Okay, I've found a way to get back to Spaghetti on ENTRY TRAJ - we can use EXEC to move forward through the displays, and that (possibly in combination with the attempt to change page while being on the wrong page) seems able to trigger some graphical confusion.
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Re: Space Shuttle - Bugfixes

Postby GinGin » Fri Feb 26, 2021 2:21 pm

Ok, maybe it needs some stronger conditions in the entry.nas ( I used mainly setVisible at each display flag changes )
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Re: Space Shuttle - Bugfixes

Postby Thorsten » Tue Mar 02, 2021 11:52 am

Okay, since I've had a good TAL to Banjul today, I've been stress-testing since by flying a spy satellite into a high polar orbit using the OMS kit, and to make things more fun, I used BFS.

A few observations:

* bad things (TM) happen when the ET fuel runs out - regardless of a manual OPS 104 transition somehow the DAP wasn't properly changed. I suppose we must do as the real Shuttle does and check whether the cutoff-buttons have been pressed to detect such a situation - in the event I used CTRL+M to manually force the transition

* BFS basically works okay, I just had to remember that one has not only to manually steer into burn attitude but also to follow the burn attitude manually - for the looong burn with the OMS kit, this actually makes a difference.

* for some reason, the OMS-2 burn wasn't terminated. Could be that we somehow never leave the OMS-1 burn under BFS control, could be something else, but it was actually counted negative in time when I finally decided to end it manually

* supposedly in simple mode the transition from BFS back to PASS should 'just work', but somehow it doesn't - definitely need to investigate what happens there, but I ran out of time.

We'll see what the saved state recovers of the adventure next time... Probably lots of errors get fixed :evil:
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Re: Space Shuttle - Bugfixes

Postby GinGin » Tue Mar 02, 2021 5:18 pm

regardless of a manual OPS 104 transition somehow the DAP wasn't properly changed. I suppose we must do as the real Shuttle does and check whether the cutoff-buttons have been pressed to detect such a situation - in the event I used CTRL+M to manually force the transition


I experienced quite the same situation during Lower Boundary limit Single engine TAL tests
It needs a manual shutdown before ET is empty to have the transition, or force the ET separation.
I didnt report it as it was close to the real thing; the need to force the shutdown like you mentionned


it was actually counted negative


Interesting, I think I observed that at least one time.
I will have an eye on it if I trigger it again during the peg 4 insertion tests ( I will test it through the BFS then)
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Re: Space Shuttle - Bugfixes

Postby Thorsten » Wed Mar 03, 2021 7:49 am

Okay, I've added a condition to the standard final stage of the ascent guidance loop that MECO is detected either when the targeted apsis is reached or when all three engines have been commanded off manually.

That leaves the situation that you might have been unable to do that because of a command path failure on one of the engines, so that engine was shut down by removing power from the engine controller, in which case we have no regular MECO signal when flying manual. Then the 104 transition, ET sep and MPS fuel dump would all have to be done manually, so I believe what I need to do is force DAP-A upon the 104 transition (currently we rely on that being done automatically to null rates prior to ETsep) and terminate the launch_loop in stages.nas at latest on ETsep (might already be done).

This is all moderately complicated, because there's surprisingly many branches that might happen...

Next I need to think how to handle all that on the abort MECO branches...
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Re: Space Shuttle - Bugfixes

Postby GinGin » Wed Mar 03, 2021 10:33 pm

Could you try a RTLS abort ?
I observed a strange behavior with last commits. After RTLS MECO, it goes to mm 104 like if it was a regular meco condition.
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Re: Space Shuttle - Bugfixes

Postby Thorsten » Thu Mar 04, 2021 6:42 am

I observed a strange behavior with last commits. After RTLS MECO, it goes to mm 104 like if it was a regular meco condition.


Aw... that sounds like we never terminate the regular guidance branch when doing an RTLS... and just haven't ever noticed because we never reach orbit either. Just now we notice because of course we shut down the engines, which is now able to trigger regular MECO.

Edit: Okay, it was as I suspected. We never terminate the regular Nasal ascent guidance loop so it keeps setting pitch targets and everything, but since the JSBSim AP path for the regular guidance is off when RTLS is running, they're not being used in any way. Only the engine-off condition is picked up in the end. Since we terminate the branch for TAL, I've added the condition to terminate it also for RTLS. I still have to check whether this would also occur for the contingency aborts, though usually an intact abort would be declared before a contingency abort...
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Re: Space Shuttle - Bugfixes

Postby GinGin » Thu Mar 04, 2021 7:59 am

Alright, perfect.

I will test that, need to see also if an early RTLS transition ( 110 Nm / mach 4.5 ish) is interesting S turn wise.
That was done like that in real, so lets test :)

Indeed for the Intact before Contingency, I dont see how it can be possible the other way around, but someone can still push the intact button by not following the procedures
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Re: Space Shuttle - Bugfixes

Postby GinGin » Thu Mar 04, 2021 9:46 pm

I fixed the Entry Display Spaghetti thing when scrolling between mm304 display with PRO/EXE

@Thorsten: I noticed something while testing the OMS insertion.

When entering a TIG early on after MECO ( like for OMS 1 autoload) , the forecasted Apsis are not calculated correctly.
I didnt find the cause, but when I compute again above 400000 feet, it works like intended

So maybe there is some 400000 feet treshold somewhere for Future TIG Apsis calculation (?)


Image
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Re: Space Shuttle - Bugfixes

Postby Thorsten » Fri Mar 05, 2021 7:06 am

When entering a TIG early on after MECO ( like for OMS 1 autoload) , the forecasted Apsis are not calculated correctly.


I suspect it might be as trivial as residual atmosphere (maybe also if it is done really early, also the effect of the MPS dump which is, after all, propulsive). So at least you need to wait till the dump is over, which would be like 2-3 minutes after MECO.

At which time

I *think* OMS burn autoload just fills the entries, but doesn't actually load the solution yet, so that wouldn't be a problem (?)
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Re: Space Shuttle - Bugfixes

Postby GinGin » Fri Mar 05, 2021 8:28 am

Ok, I see . Indeed for the dump , target apses are correctly computed after .

The oms burn are loaded automatically .
It does not interfere with the oms1 outcome .
Just the target display is showing wrong data’s if not reloaded after dump but the burn is nominal.
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