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Space Shuttle - Bugfixes

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Re: Space Shuttle - Bugfixes

Postby Thorsten » Mon May 13, 2019 6:28 am

Perhaps it's a compositor issue?
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Re: Space Shuttle - Bugfixes

Postby legoboyvdlp » Mon May 13, 2019 10:26 am

I'm not using the compositor (at the moment).
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Re: Space Shuttle - Bugfixes

Postby eatdirt » Tue May 14, 2019 9:53 pm

Hi there,
while still lagging behind Thorsten for the docking challenge, I am trying to optimize things. One thing I don't manage to sort out is that when I start a scenario with:

Code: Select all
fgfs --aircraft=SpaceShuttle-ISS --prop:/sim/presets/ISS-prox-x=150


the Shuttle gets something as 1.9ft/s of initial relative velocity w.r.t ISS. Here a picture when the simulation starts, with the rdv manager opened and showing the velocities (the ISS really moves to the right in a matter of a few seconds):

Image

I am keeping on burning some fuel even before starting the docking to cancel this, so I was just wondering if that's expected?

I have also noticed that changing the --lon and --lat on the command line affects the initial velocities, they're still non vanishing but distributed differently with respect to vx, vy, vz, very weird. I've checked that this is not my joystick mocking me, it was unplugged :)

Any advice appreciated,
Cheers,
Chris.
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Re: Space Shuttle - Bugfixes

Postby Thorsten » Wed May 15, 2019 6:43 pm

It seems well within tolerances...

(Just think about it - we're placing object in earth-centered co-moving coordinates. So there's one object moving with 26.000 ft/s computed at 120 Hz, you're trying to place another object right next to it moving at the same speed, but you compute that at any rate ranging from 5 z to 60 Hz, you compute by necessity in a different engine, there's all sorts of discretization errors, there's the frame drag due to model placement itself which gives a hefty extra one-time discretization error - and at the end of the day, you're ~ 2 ft/s off initially - or an error of <0.0077% - it's not so bad, all things considered... for miracles, please contact the Heaven department...)
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Re: Space Shuttle - Bugfixes

Postby eatdirt » Wed May 15, 2019 7:47 pm

for miracles, please contact the Heaven department


Hey, that's exactly what I was doing there :mrgreen:

Thanks for the explanations. It is however not a random error but a quite constant systematics, those numbers show up at each start, but then I suspect they come from the approximate 2 to 1 body method and same chain of events to place them. And maybe my 16K earthview textures do not help in doing fast calculations neither... I'll live with that then :)
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Re: Space Shuttle - Bugfixes

Postby eatdirt » Wed May 15, 2019 9:06 pm

please contact the Heaven department


It is actually happening!!!!! They talked to me, direct line to my mind!!! They suggested to start FG with:

Code: Select all
fgfs --prop:/sim/presets/ISS-prox-x=150 --aircraft=SpaceShuttle-ISS


instead of what I was doing

Code: Select all
fgfs --aircraft=SpaceShuttle-ISS  --prop:/sim/presets/ISS-prox-x=150


and that's what I get:
Image

Woo! Now that sounds like a bug :) And now we're talking about the docking challenge :mrgreen:
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Re: Space Shuttle - Bugfixes

Postby Thorsten » Thu May 16, 2019 5:22 am

I can't even begin to guess why this should possibly matter...
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Re: Space Shuttle - Bugfixes

Postby wkitty42 » Thu May 16, 2019 9:02 pm

the only thing i can think of is initialization processing order...
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Re: Space Shuttle - Bugfixes

Postby eatdirt » Thu May 16, 2019 9:47 pm

the only thing i can think of is initialization processing order...


I see 2 fgfs threads running at 100% each during initialization, maybe it is some race conditions?
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Re: Space Shuttle - Bugfixes

Postby Thorsten » Fri May 17, 2019 5:23 am

Yeah, except it really shouldn't matter when exactly the offset property is initialized, because it for sure is used only a few seconds after FDM-init.
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Re: Space Shuttle - Bugfixes

Postby GinGin » Sat Jun 01, 2019 11:47 am

A small thing I was tracking for weeks ( not a "proper" bug though)


I had the feeling that Shuttle was always 30 000 pounds ish too heavy
Like doing a landing with No OMS propellant, nothing in the payload at 210 000 pounds plus where it should be around 190000 ( taking a 185000 pounds shuttle dry weight)


So, I looked into the internal properties and found that:


Starting a scenario with 20000 pounds of payload in mission file


Image


Shuttle Orbiter should be 1850000 +20000 +30000 ( OMS fuel, RCS, cryo etc)= 235000 ish pounds


But one in Orbit, I had 2740000 pounds
I found in payload properties that there was a 40000 pounds coming from nowhere ( different from the mission file)
It is reset at that value at each launch game



Image



after removing it, weight is looking close to what was expected

Image
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Re: Space Shuttle - Bugfixes

Postby Johan G » Sat Jun 01, 2019 2:11 pm

If that is an issue and it will be fixed, it would be very interesting to see how close you get to published numbers in the various tests you are doing. That said, Thorsten's work in that regard is already quite impressive.
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Re: Space Shuttle - Bugfixes

Postby GinGin » Sat Jun 01, 2019 2:15 pm

Numbers are very close.
I took data’s from official mission sum up weight and payload .

Yes I think it is 40000 in addition , like a standard payload , but that add to te payload we can put into the mission file.
After removing that 40000 thing , numbers are really close .
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Re: Space Shuttle - Bugfixes

Postby wlbragg » Sat Jun 01, 2019 3:46 pm

It coming from SpaceShuttle/shuttle.xml
Code: Select all
<pointmass name="Equipment">
            <weight unit="LBS"> 40000 </weight>
            <location name="POINTMASS" unit="M">
                <x>  2.7 </x>
                <y>  0.0 </y>
                <z> -2.7 </z>
            </location>
        </pointmass>

Added to the empty weight of 180,000.
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Re: Space Shuttle - Bugfixes

Postby GinGin » Sun Jun 02, 2019 9:30 am

Nice catch thanks.
Could you put it to zero for next Dev branch update ?
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