Space Shuttle - Development

[wlbragg]

I completely misread the texturing of the NASA model and left out a few of the original textures. Here it is corrected and with a "first attempt" normal map for the foil effect.

Anyone have a nice GPL foil texture lying around. I made this one in a couple seconds in GIMP from the existing texture which had some structure to it.

[legoboyvdlp]

That looks good! Nice work!

[wlbragg]

Thanks, it's really all NASA, I just added a couple hastily made normal maps.

I guess I am done for now and will push this. Eventually we can add a couple details like darkening the camera lenses and better foil texture.

[Thorsten]

Nice and shiny! Great work!

[legoboyvdlp]

Nice work, that looks great

(SOTM? )

[GinGin]

Wow very nice guys.
Thanks for taking a look at ISS Wayne

[Vinny002]

The space shuttle for FG is just keep getting better and better!!

Cheers,
Vincent

[GinGin]

Indeed, I think it is eligible for a NASA stamp approval

[GinGin]

Some news of some work I made On Shuttle Ascent AP.

I wanted to reproduce with AP what I did in manual by flying a more close to real profile






Aim was to be before Mach 1.2 up to 1.6 ( Max Q 750 psf ish) around -4° of alpha, the Shuttle Sweet spot for wings loading




I mainly changed the pitch ratio and attitude target ( 65 ° of pitch before bucket)
Then widden the pitch down after thrust bucket ( end of bucket 50 seconds at 65 ° of pitch and then a 0.5 °/s of pitch down to be at 30 ° at Srb sep around 2 mn into the flight)
That worked really well, and really close to the above ascent guideline

Here at Max Q, alpha of -6 °, plenty of room for wing loading limits







Then for the second stage, I wanted MECO around 8mn40 s around 360 kfeet and Apogee 40 mn after lift off ( to be close to real MECO situation)
A bit of tweaks and here we are :

40 seconds after MECO
Apogee 40 mn into the flight at 125 Nm





If that is not a demonstration of how precise is the fdm coded compared to real datas.
I am quite happy on that one, being able to reproduce the ascent as close as NASA did , with a safer margin concerning wing loading.



Question: Is it possible to tell in AutoLaunch.nas to throttle up up to 106 % after bucket by some command lines ? ( didn't find the shortcut in fdm/jbsim)

[Thorsten]

Question: Is it possible to tell in AutoLaunch.nas to throttle up up to 106 % after bucket by some command lines ? ( didn't find the shortcut in fdm/jbsim)

Throttle is determined by two parameters - mapping and setting. If you set it to 1, the normal mapping is 100%, but you can remap 1 to 106 or 109% (SPEC 51 allows you that - but since it's basically a property, you can also pre-set it via commandline).

If you are in the default mapping, you can not throttle higher than 100% - you need to activate a different mapping for that.

[GinGin]

I see.
That would be nice.
I used 109 pour-cent in stage 2 to compensate the 100 pour-cent in stage 1
Average for 8mn30 is 104 pour-cent, ie. What was flown.

In which file can I remap the 1 to 104 pour-cent ,? ( or the correct command line )
That would be neat, thanks

[Thorsten]

Try setting

/fdm/jsbsim/systems/throttle/throttle-mode

to 1 - this should map to 106%.

[Thorsten]

After some coordinate system pains, I have now implemented non-grabbing interactions between end-effector and a satellite (basically you can - intentionally or not - push it away with the end effector). Since there have been quite some changes to basically all of the co-orbiting objects codebase, I'd appreciate if the people running the development branch could test whether the normal rendezvous stuff still works as expected (I don't expect any breakage, but who knows...)

[GinGin]

Try setting

/fdm/jsbsim/systems/throttle/throttle-mode

to 1 - this should map to 106%

Thanks.
I changed it directly in the Throttle.xml
( I put correct order, max 109, abort 106 and nominal at 104, works really nice)

Code: Select all

<switch name="systems/throttle/throttle-factor">
         <default value="1.0"/>
         <test value="1.09">
            systems/throttle/throttle-mode == 1   
         </test>
         <test value="1.06">
            systems/throttle/throttle-mode == 2   
         </test>
         <test  value="1.04">
            systems/throttle/throttle-mode == 3   
         </test>
      </switch>

I'd appreciate if the people running the development branch could test whether the normal rendezvous stuff still works as expected (I don't expect any breakage, but who knows...)

Of course, Time for some Hubble Rendez Vous.


I almost finish my stuff with Ascent AP.
I entered into Auto Launch.nas all the open loop parameters for stage 1.
Even closer to the real path now.

Code: Select all

if ((getprop("/fdm/jsbsim/velocities/vtrue-fps") > 571.0))
      {
      setprop("/fdm/jsbsim/systems/ap/launch/pitch-target", 69.4);
      setprop("/fdm/jsbsim/systems/ap/launch/pitch-max-rate-norm", 0.04);
      }

   if ((getprop("/fdm/jsbsim/velocities/vtrue-fps") > 678.0))
      {
      setprop("/fdm/jsbsim/systems/ap/launch/pitch-target", 68.6);
      setprop("/fdm/jsbsim/systems/ap/launch/pitch-max-rate-norm", 0.04);
      }
      
    if ((getprop("/fdm/jsbsim/velocities/vtrue-fps") > 747.0))
      {
      setprop("/fdm/jsbsim/systems/ap/launch/pitch-target", 67.8);
      setprop("/fdm/jsbsim/systems/ap/launch/pitch-max-rate-norm", 0.04);
      }
      
   if ((getprop("/fdm/jsbsim/velocities/vtrue-fps") > 846.0))
      {
      setprop("/fdm/jsbsim/systems/ap/launch/pitch-target", 66.2);
      setprop("/fdm/jsbsim/systems/ap/launch/pitch-max-rate-norm", 0.04);
      }   

etc

And a initial roll based on relative speed

Code: Select all

if (getprop("/fdm/jsbsim/velocities/vtrue-fps") > 120.0)

At Max Q ( 760 and alpha of -2 °, like in the books)




Almost finish with Stage 2.
I changed the H dot target at Meco to Have 270 fps, giving a good inertial FPA for a 120 Nm apogee

On that matter, I was wondering if it was possible to set a Flight path target at MECO instead of Hdot
FPA from that property



into /fdm/jsbsim/systems/ap/launch

That would allow us to pinpoint even more the MECO target based on those datas

[Thorsten]

I changed it directly in the Throttle.xml

The reason I normally throttle at 100% is that by default, we fly pretty empty - so if we add payload and change throttle mapping, we might get comparable flight characteristics. Especially abort dynamics seems to be dependent on performance, I've seen several scenarios in which the AP worked fine for the default launch but failed with a heavy payload.

So I am generally wary of changing performance - I know it is possible to run into issues, I just don't have a good feeling for them.

On a similar note, I was never able to figure out whether the fact that we can reach orbit with 6% propellant remaining with an empty payload bay in a low-inc scenario is realistic or bad. It seemed quite a lot of leftover to me, and more than once I was wondering just where we might go wrong. I believe the SRBs are well under control, rocket performance outside the atmosphere is mathematically easy, but I can't see for the sake of it how drag or pressure effects inside the atmosphere might screw things to that degree (and I remember I have explicitly verified that liftoff thrust of the engines is okay).

On that matter, I was wondering if it was possible to set a Flight path target at MECO instead of Hdot
FPA from that property

As in 'flightpath angle' like for a PEG-4 target, i.e. basically the ratio of vertical over horizontal velocity? That's fairly easy.