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Space Shuttle

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Re: Space Shuttle

Postby Thorsten » Wed Oct 10, 2018 5:42 am

I will! Do X,Y,Z, VX,VY,VZ from SPEC 34 are enough at the times you mentioned?


The MCC dialog has a feature to capture the state vector with a timestamp intended for that purpose - I'd recommend to use that, SPEC 34 will inevitably lag some and getting accurate timing won't be easy.

SPEC 95 displays compatible settings, and I've tried as well on the payload operations menu, same result, ELBOW does not move a bit.


-2.4 degree is the reach limit of the elbow joint... I suspect there may be a connection.

(And internally, the RMS arm is integrator-driven - unfortunately if you drive past a stop, the arm stops moving but the integrator still logs, so once you stop and reverse, you need to drive the integrator back for a while till it reaches the working region again - perhaps not so realistic, but the RMS arm isn't my favourite system to work on, the math is a mess...)
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Re: Space Shuttle

Postby GinGin » Wed Oct 10, 2018 4:44 pm

@Thorsten: 2018.1.1 for the version


Spec 34... The day you fully implement that page with rendez vous, I take one week off out of work :mrgreen:
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Re: Space Shuttle

Postby eatdirt » Wed Oct 10, 2018 7:10 pm

you need to drive the integrator back for a while till it reaches the working region again


Thanks!!!! that was it, it was deep into the void, took me a while to get it back :)
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Re: Space Shuttle

Postby eatdirt » Thu Oct 11, 2018 6:43 am

At last!

I also discovered that it was not a good idea to put the END EFF with a pitch of 90, R=Y=0 (soft stop disabled). The arm was doing small random jumps around that position for a while in spite of my command to change the angle back to 85. It did after quite a while.

Image

flying solo:

Image
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Re: Space Shuttle

Postby eatdirt » Thu Oct 11, 2018 8:35 am

Flightgear 1980.1.1, SpaceShuttle add-on? :shock: :shock: :shock:

Image
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Re: Space Shuttle

Postby Thorsten » Thu Oct 11, 2018 10:00 am

I also discovered that it was not a good idea to put the END EFF with a pitch of 90, R=Y=0 (soft stop disabled).


Euler singularity...
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Re: Space Shuttle

Postby Thorsten » Thu Oct 11, 2018 4:21 pm

And... would you remember the state vectors for the insertion burn and coast afterwards? I'd really like to be able to confirm whether 2018.2.2 is working as it should...
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Re: Space Shuttle

Postby eatdirt » Thu Oct 11, 2018 9:55 pm

Yes, sorry, I am still up-there, trying to fit a de-orbit burn in my real life :)

I'll try to test the insertion as soon as possible, just after coming (crashing) home!
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Re: Space Shuttle

Postby eatdirt » Fri Oct 12, 2018 10:22 pm

Ok, here you go, started a 2nd instance of fgfs for that. Launch guidance from Kennedy Space Center targetted at 320 miles.

Just after ET separation (HA=325 HP=68):
Image

OPS 105, 10 minutes before the burn. Solution looks good TGT 325 322:
Image

Just before pressing "EXEC", 2 secs before the burn. As I mentioned in an older post, the attitude always lags behind the always changing one required by the burn, shift of 3 degres between actual R on the ADI ball and burn attitude R; 1 degree of error for the Pitch. Dunno if that may play a role.
Image

For the eyes, the burn over Australia:
Image

Burn is over, CUR HA=346 HP=300, no good then :?
Image

This should be 20 minutes later, trained GPC reconfig for waiting:
Image

Some time even after:
Image

Just before abandoning ship
Image

Hope it helps!

PS: On my other running session, there is a small, but certain, memory leak in fgfs, after 5 days, takes 10Gb of RAM while it starts around 2 Gb max.
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Re: Space Shuttle

Postby Thorsten » Sat Oct 13, 2018 6:43 am

Putting

Code: Select all
input

config

units imperial
time_format plain
gravity_model J3
earth_model IERS
burn_model constant
plot2d_resolution 400
fit silent
max_time 6000
fit_max_iterations 100
time_format MET

state_vector

x 9666558
y -16333688
z 9719450
vx 23116
vy 11764
vz -3260

met 000/00:14:43

landing_site
name Testsite
lat 0.0
lon 0.0

launch_site
name Testsite
lat 0.0
lon 0.0


burn_peg7
name insertion
tig 000/00:56:00
dx 430.0
dy 0.0
dz 0.0


output

list
orbital final

plot3d
file shuttle_test_leo.dat   
x x
y y
z z



end


into my leo_targeting tool gives me

Image

(i.e. all points match up as expected within accuracy - FES exhaust and attitude control would stll give propulsive effects which the solver does not know)

and confirms final apoapsis and periapsis to 345.85 and 299.993 nm respectively, i.e. the burn outcome is correct for the Delta v applied.
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Re: Space Shuttle

Postby legoboyvdlp » Sat Oct 13, 2018 9:21 am

Given the default value is about 100 / 60 miles as far as I remember, if the testing user did not perform any OMS 2 would they not almost re-enter the atmosphere at periapsis?

Furthermore, I did crash quite a lot of times by accidentally transitioning to thrust vectoring or aerojet in orbit and not realising it until too late.

I'll test 2018.4 this morning with default settings and see if I can survive one orbit without any burns.
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Re: Space Shuttle

Postby eatdirt » Sat Oct 13, 2018 9:41 am

Given the default value is about 100 / 60 miles as far as I remember, if the testing user did not perform any OMS 2 would they not almost re-enter the atmosphere at periapsis?


I remember my first flight, this is what happened, I ripped the shuttle at HP but I was not in the correct attitude. Another time, I remembered putting manually the shuttle at some AoA manually, bouncing on the atmosphere and landing to a new orbit :)

Whatever you do in orbit, clck on DAP auto on neutral should put you back on tracks!
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Re: Space Shuttle

Postby eatdirt » Sat Oct 13, 2018 9:43 am

confirms final apoapsis and periapsis to 345.85 and 299.993 nm


Perfect then, actually impressive!!

Would it be possible to improve the accuracy of the predictor though?
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Re: Space Shuttle

Postby Thorsten » Sat Oct 13, 2018 9:45 am

Given the default value is about 100 / 60 miles as far as I remember, if the testing user did not perform any OMS 2 would they not almost re-enter the atmosphere at periapsis?


Yes - at periapsis, i.e. over the continental US (a bit before the point where MECO occurred) - not after half an orbit over India as has been observed.

Furthermore, I did crash quite a lot of times by accidentally transitioning to thrust vectoring or aerojet in orbit and not realising it until too late.


Are you in the habit of pressing Ctrl+key frequently for some odd reason? It's a two key combo involving a rare key, so it should be pretty hard to get by accident - never happened to me even once.

Also, why would you crash in orbit? Activating thrust vectoring in orbit would be completely harmless - akin to switching to a free drift DAP.
Last edited by Thorsten on Sat Oct 13, 2018 10:03 am, edited 1 time in total.
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Re: Space Shuttle

Postby Thorsten » Sat Oct 13, 2018 9:46 am

Would it be possible to improve the accuracy of the predictor though?


Kinda surprised it's not done yet, I need to have a look. Probably the predictor uses impulse approximation, so for a long burn you're off a bit. But since the Shuttle has a lightweight copy of LEO Targeting, we can get the precise value easily.
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