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Re: Space Shuttle

Postby Thorsten » Mon Jul 31, 2017 6:38 pm

I have to read again, dont understand really why there is two choice to align IMU. Two differents method but same results.


I understand why there's a difference, I'm just not sure it makes any sense to simulate that difference - after all, I don't want to simulate all the different gimbal stages for each unit...
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Re: Space Shuttle

Postby GinGin » Mon Jul 31, 2017 6:43 pm

Yeah you right, was thinking to it.
Actually effect in sim will be exactly the same, to have a better aligned Imu at the end.

I am a bit lazy tonifht to go back in IMU wb but still curious ahah , could you quickly explain me why a torque would be choose over a matrix alignement and vice versa ?
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Re: Space Shuttle

Postby legoboyvdlp » Mon Jul 31, 2017 6:54 pm

Does the SpaceShuttle have GPS, or is that a too "modern" invention for its avionics? :)
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Re: Space Shuttle

Postby wlbragg » Mon Jul 31, 2017 7:03 pm

From the crew manual...
The release of OI-27 flight software (FSW)
began the process of replacing the orbiter
tactical air navigation (TACAN) system with a
global positioning system (GPS). GPS provides
the navigation system with an alternate source
of orbiter state vector data throughout the orbit
and entry phases of flight. Currently, there is a
mixed fleet of either triple-string GPS or triple
string TACAN with a single GPS receiver.
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Re: Space Shuttle

Postby Thorsten » Tue Aug 01, 2017 5:02 am

I am a bit lazy tonifht to go back in IMU wb but still curious ahah , could you quickly explain me why a torque would be choose over a matrix alignement and vice versa ?


I'm not 100% certain, but I think it's because of the Euler singularity - which is usually at 90 deg pitch up and down and confined to a point. Regardless of the 'true' gimbal orientation, you can always define a transformation that gives you a different system - except at the singularity.

But if you do so, the singularity expands from a point into a ring.

There's a practical example of this - Vitos has done the trick for Vostok, it utilizes the FG attitude computation but changes it into a system 90 degrees shifted - as a result the singularity encompasses the whole pitch=0 ring around the horizon.

What I'm guessing is that gimbals are torqued to avoid that from occurring by keeping the correction matrix shift as small as possible.

Does the SpaceShuttle have GPS, or is that a too "modern" invention for its avionics?


It sure does, but GPS doesn't provide attitude information. And Atlantis is a single string GPS vehicle - you can access GPS information, but there's no redundancy in case of a failure and so operationally you may not rely on GPS except in the case of a massive systems failure elsewhere or for testing and evaluation purposes.

(If you like, you can force GPS data into the state vector, and that's going to provide near-perfect position information).
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Re: Space Shuttle

Postby GinGin » Tue Aug 01, 2017 4:06 pm

Cool thanks.
So when it was approaching singularity point, it was necessary to Torque the IMU to another position instead of just doing a Matrix transformation?

I read your wiki about Git, it should be OK using TortoiseGit and putting the devel link to update directly in FG main file? ( is it like Tortoise SVN)
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Re: Space Shuttle

Postby Thorsten » Tue Aug 01, 2017 5:02 pm

I think it's a precaution - there's no escaping the singularity as you can orient the Shuttle any way you like, but normally the IMUs all have the orientation offset, so when the singularity is a point they never run into it all at the same time. If the singularity is ring-like, they might overlap among IMUs - and THEN you have a problem.
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Re: Space Shuttle

Postby GinGin » Wed Aug 02, 2017 4:15 pm

I might have speak a bit fast concerning the dev version installation :)

So I downloaded Git for Windows and Tortoise Git, then created on Desktop a new folder, I cloned your repository inside and took all the data into the code file into a file called SpaceShuttle.
Then I put it into C>Documents>FlightGear>Aircraft>org.flightgear.fgaddon

I guess it is just for official add on as I have an update showing on Space Shuttle in Launch menu and I can't Fly with it.

So I have to create a new aircraft file for manually downloaded ones and point it in Launch menu ?

And I saw the dev version is around 2 Gb and official version around 400 Mb, why that difference?
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Re: Space Shuttle

Postby wlbragg » Wed Aug 02, 2017 4:47 pm

The dev version is full of original reference material and artwork, along with the evolution history which swells over time.

Yes, you should put it in its own stand alone directory and point the QT launcher menu at it in Addons/Additional aircraft locations.
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Re: Space Shuttle

Postby GinGin » Wed Aug 02, 2017 5:17 pm

Perfect thanks
Next test on Sunday :)
Impressive those 2 gigs, Shuttle has gold inside ahah

You know on windows how to update the clone when files are changed without downloading the all repository again ?
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Re: Space Shuttle

Postby wlbragg » Wed Aug 02, 2017 6:19 pm

I don't know your GUI specifically, but on Linux Git Gui (which is what I am using) it is a "fetch" (git pull) and then "merge". That gets only the changes to the remote as compared to your local copy.
However , if there are any modifications to the local copy that have not yet been "committed" locally, it won't let you merge the new changes. And if any new "committed" changes conflict with the new "fetch" from the remote repo then you have to resolve those conflicts first.

If your not changing any files a fetch (git pull) and merge is all that should be required.
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Re: Space Shuttle

Postby GinGin » Wed Aug 02, 2017 6:32 pm

Thanks, so it's git pull and merge, perfect.
So you mean if I do any changes on my computer, it will not merge automatically, but if I don't touch the repository on my computer and pull and merge with the change that you make in the git repository, it's ok?

Ahhh can't wait to try BFS, I also noticed that you adjusted the flag for ADTA calculations Thorsten, great :)
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Re: Space Shuttle

Postby wlbragg » Wed Aug 02, 2017 7:10 pm

So you mean if I do any changes on my computer, it will not merge automatically, but if I don't touch the repository on my computer and pull and merge with the change that you make in the git repository, it's ok?

Correct
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Re: Space Shuttle

Postby GinGin » Fri Aug 04, 2017 3:39 am

Heya, thanks for the info. I am getting used to FG.

Once question concerning multiple objects in orbit, Do you think it will possible in the future to reach from ground an object already orbiting ?
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Re: Space Shuttle

Postby wkitty42 » Fri Aug 04, 2017 4:38 pm

the shuttle does have, IIRC, an ISS docking capability complete with an ISS to dock to ;)
"You get more air close to the ground," said Angalo. "I read that in a book. You get lots of air low down, and not much when you go up."
"Why not?" said Gurder.
"Dunno. It's frightened of heights, I guess."
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