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Space Shuttle - Help

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Re: Space Shuttle - Help

Postby GinGin » Sun Apr 07, 2019 8:50 pm

Ahhh very nice
A lot of good informations with velocities page .

I found earth relative in those .

And there is something strange with switch from 103 to 104 .

Speed in the pfd seems to go from inertial ( 25800 ish at meco in ops 103) to 27000 which correspond to Mach value in velocities page when transitioning towards new ops 104.

Need more test and will post deeper infos on that then :)
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Re: Space Shuttle - Help

Postby Thorsten » Mon Apr 08, 2019 5:16 am

At some point, you could probably just learn to read the code - might be faster than to do tests and reverse-engineer what happens :mrgreen:
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Re: Space Shuttle - Help

Postby GinGin » Mon Apr 08, 2019 11:41 am

Thorsten wrote in Mon Apr 08, 2019 5:16 am:At some point, you could probably just learn to read the code - might be faster than to do tests and reverse-engineer what happens :mrgreen:



Indeed, it would be wiser.
I have started a couple weeks ago to " learn Nasal" to read through the code directly.
https://forum.flightgear.org/viewtopic.php?f=30&t=33400



Up to MM 103, speed on pfd is well in inertial ( eci velocity mag), then switch to a Mach number quite higher in MM 104 up to OPS 3 ( 1200 fps more than Vi, don't know real meaning of the number)
Would it be possible to leave Eci Velocity Mag in OPS 2 and mm 104 through 106, and ops 3 up to mm 304 ?

Image



And same for OPS3, would it be possible to replace that "mach " value on the pfd by Vtrue in MM 304 ( to have Vr like in reality, in MM 304 Speed switches from Vi to Vr, ie. eci to Vtrue in FG)

Image


I finally found the two parameters I was looking for test ( eci and vtrue), thanks for the help :)
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Re: Space Shuttle - Help

Postby eatdirt » Wed Apr 10, 2019 1:24 pm

Hey guys, @Gingin especially.

I have troubles to start the STAR TRK and the -Z TRACKING to ISS, which should be target ID 1. Do we have to change something in the default mission file to do so?
For the time being, I am always getting NO TARGET and hitting MNRV in OPS 201 returns a crazy attitude like 180deg, 90deg 0deg. RDV ITEM 1 is enabled on SPEC 33 and correctly returns ranges and rates. For the time being, I was using 2018.3.2 with the upgraded orbital nasal file, right now I am compiling 2019.1.1 to see if that fixes the issue, but it looks like I am missing something, maybe it is a stupid thing from myself!?

any help appreciated!
Cheers,
Chris.
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Re: Space Shuttle - Help

Postby Thorsten » Wed Apr 10, 2019 1:49 pm

For the time being, I am always getting NO TARGET


For the Shuttle, that one is actually pretty descriptive - it really means it has no target and doesn't know what to track (which in turn probably means that rendezvous navigation on SPEC 33 wasn't started, so no target state vector is propagated by the avionics).
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Re: Space Shuttle - Help

Postby eatdirt » Wed Apr 10, 2019 2:11 pm

that rendezvous navigation on SPEC 33 wasn't started, so no target state vector is propagated by the avionics


Yes, I know, this sentence is even "blinking" in the manual, but it is started, everything works as expected on SPEC33 when I enable RDV nav, but no way to get other thing than NO TARGET. That's why I was thinking that extra-things should be added in the mission.xml file. Still, I have to test again with 2019.1.1, but I wanted to check with you guys I wasn't forgetting something else, I see on the GinGin pictures that this is working in his case :(
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Re: Space Shuttle - Help

Postby GinGin » Wed Apr 10, 2019 4:10 pm

Hey Chris,

At which distance do you try ?
You need to be close ( less than 200 or 300 km from ISS I would say)

An example of what you would see :

Image


-Z axis towards ISS ( maintained with LVLH dap and large deadbands on Spec 20 to avoid Hi Rate), Star tracker in TGT (No target if you are too far, OUT FOV if you are within a good disatance form iss but not pointing towards target, Hi rate if you move too fast, nothing if it is ok in Status)
Then filter starts to work on spec 33 ( crt 3)


You can try that scenario for practicing ISS rendez vous ( 2 or 3 orbits from ISS RDV)

Code: Select all
--lat=0.0 --lon=5.07 --heading=44.66
--aircraft=SpaceShuttle-ISS




and in Mission file

Code: Select all
orbital-targets>
  <section-defined type="bool">true</section-defined>

  <object-label type="string">ISS</object-label>
  <inclination-deg type="double">42.76</inclination-deg>
  <alt-km type="double">340.0</alt-km>
  <node-lon-deg type="double">5.07</node-lon-deg>
  <anomaly-deg type="double">2.0</anomaly-deg>
</orbital-targets>
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Re: Space Shuttle - Help

Postby eatdirt » Wed Apr 10, 2019 11:06 pm

Hi Gingin,
thanks for the help and advices, I think I was too far to get something else than NO TARGET then, was at 200ish kms. But using the devel version 2019.1.1 of FG, and starting with a empty .fgfs/ directory seemed to have fix the other issue, half of my problems was just moving the shuttle with -Z towards the target, now that works fine!!!!

Now, time to get close enough... :)

Thanks,
cheers,
chris.
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Re: Space Shuttle - Help

Postby eatdirt » Wed Apr 17, 2019 5:12 pm

@Gingin, quick question: do you center the target in the middle of the COAS, or like said in the NASA manual, 2.5 degrees below at 1000fts? (where the CoG is supposed to pass).

I ask you because while I was trying to get closer from a rbar above position, I had to always compensate an acceleration that was in the direction of motion. I was really expecting the opposite, being above I should fly slower and experience a relative acceleration in the direction opposite to motion.
An interpretation could be that since I was putting the target in the COAS middle, I was actually creating a DeltaVx compotent by closing-in on DeltaVz. Or the effect is due to cross-couplings? Or maybe an issue in the semi-analytical frame? Did you experience this as well?

Thanks,
Cheers,
Chris.
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Re: Space Shuttle - Help

Postby Thorsten » Wed Apr 17, 2019 5:38 pm

I had to always compensate an acceleration that was in the direction of motion. I was really expecting the opposite, being above I should fly slower and experience a relative acceleration in the direction opposite to motion.


You're flying on a circle with radius R with an inertial speed v. You cover the distance v*t per unit time. The whole circle has a circumference of 2 R pi, so the fraction you cover is vt / (2 R pi) and if you multiply that with 2 pi that's the angle you advance per unit time.

Now, proximity x is a measure of the angular distance between the two objects (multiplied with the target radius).

So as you go down, your new radius R' is smaller than R, and hence vt / (2R' pi) is _larger_ than vt/(2R pi) - in other words, for constant inertial speed decreasing the radius means the angular distance you advance per unit time grows - which is in essence an acceleration along proximity x.
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Re: Space Shuttle - Help

Postby eatdirt » Wed Apr 17, 2019 6:17 pm

for constant inertial speed decreasing the radius means the angular distance you advance per unit time grows


Arf!! Thanks!! You're completely right, v_x inertial remains constant while going down, so the angular speed must increase!!! I was completely drowned in the circular orbit picture. It costed me a lot of fuel as I put the shuttle the wrong way, I had to brake with the front thrusters.... :)
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Re: Space Shuttle - Help

Postby Johan G » Fri May 03, 2019 1:19 pm

Low-level flying — It's all fun and games till someone looses an engine. (Paraphrased from a YouTube video)
Improving the Dassault Mirage F1 (Wiki, Forum, GitLab. Work in slow progress)
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Re: Space Shuttle - Help

Postby GinGin » Sat May 04, 2019 10:25 am

Thanks Johan, the Snow line might be a recurrent question indeed
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Re: Space Shuttle - Help

Postby GinGin » Tue Jun 04, 2019 9:58 am

@EatDirt : Moving the topic here for manual ascent.
Nice for the warthog I am wondering if there is a way to put the THC on a stick and RHC on an another stick , would be awesome for rendez vous 8)

For the manual ascent, you can try first with a 60 degrees inclination to have a nice roll and stable attitude in pitch and yaw quite early in the ascent.

Then here some hints for first stage ascent

Image

Just after the roll, take pitch in css and carefully pitch down to 70 degrees before 30 seconds and Mach 0.9
At 30 seconds, throttle down and start to slowly pitch down at 0.5 deg/s max ( keep an eye on AOA , don’t go above 2 degrees above between Mach 1 and Mach 2 )
That rate will lead you at srb separation ( 1mn50 ish) around an attitude of 30 degrees ( 70-30 = 40 degrees to loose from 30 seconds up to 1mn50, hence 0.5 deg/s starting at 30 seconds is a good base)

Good luck :)
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Re: Space Shuttle - Help

Postby GinGin » Sun Jun 09, 2019 5:00 am

Quick question .
I am doing an external keyboard and some switches for dps management

I was wondering if it is possible to assign some keyboard shortcut for the keyboard on game like we have for some switches ( like de clutter , gear etc )
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