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Space Shuttle - Development

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Re: Space Shuttle - Development

Postby GinGin » Sat Feb 22, 2020 4:45 pm

Hello,

Since BFS has now its own set of CWS warning messages (most of them coincide with PASS, but there's some that are specific to either system, so I had to separate them) removing the blinking last message from BFS now requires depressing key on the keypad talking to BFS


Was it introduced in the last dev version from january ?
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Re: Space Shuttle - Development

Postby Thorsten » Sat Feb 22, 2020 6:13 pm

Yes.
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Re: Space Shuttle - Development

Postby GinGin » Sun Feb 23, 2020 2:19 pm

Thorsten wrote in Sat Feb 22, 2020 6:13 pm:Yes.


Alright.
What specifically is in BFS CWS warning messages ?
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Re: Space Shuttle - Development

Postby GinGin » Tue Mar 31, 2020 6:47 pm

Just a quick post to show the effect of thrust and consumption adjustments on propellant remaining and payload limitation.

Here, a 40k lbs payload with an OMS assist of 4000 lbs ( 100 seconds) for a direct insertion on a 51.6 ° Orbit
( Max payload for that INC in SCOM performance)

Image



Just 2000 ish lbs prop remaining , quite alike real Final Performance reserve.
Just enough to not let the engines dry out and damage the Turbo Pump :)
Tested RTLS, TAL and ATO also. At FCOM Limitations .

I will do a thorough report later.
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Re: Space Shuttle - Development

Postby GinGin » Wed Apr 01, 2020 6:57 pm

Same test with a due East Launch, and 50 k lbs payload ( we might go up to 53 kish lbs for a 120 Nm Apogee)
13k lbs more than for the same Launch towards ISS, that is becoming challenging payload wise :)

On the limit, less than a percent remaining


Image
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Re: Space Shuttle - Development

Postby eatdirt » Wed Apr 08, 2020 2:21 pm

Hi there,
I am reading the SCOM... don't ask me why :) Up to the style which sucks, quite a lot of interesting details inside!!!

I've spotted 2 little things in our Shuttle that are slightly different on panel R2:

1) SCOM, page 2.1-15, section "Temperature Control", they say that the BOILER CNTRL/HTR switches have 3 positions: A, B and OFF. We kind of see it as well in the 3D model, but the label "OFF" seems to be hidden by a screw and we can only read "O..". In our shuttle, the switches have only A or B positions. Correlated to this, in the checklist for post-insertion, it is written to switch on heater, and even though the switches are already in position B, that checklist item is not displayed in green. So it sounds like the 3D model of that switches is missing the OFF position and that the initial position should be OFF and not B?

2) In the logic for the APU ready to start indicator, page 2.1-16 (first column left), they claim that the "nitrogen shutoff valve should be opened". In our shuttle, it seems that the logic only test for the BOILER PWR switches and ignore the BOILER N2 SUPPLY switches.

I've also discovered why we keep APU running in case of aborts, these bastards may explode if restarted before 180mn without active cooling. Amazing :)
I also like the comment claiming that after active injector cooling, during 3.5 minutes, you only have 1 second to start the APU. Better not slipping on the switch then...

Cheers,
chris.
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Re: Space Shuttle - Development

Postby GinGin » Sat Apr 11, 2020 4:52 pm

eatdirt wrote in Wed Apr 08, 2020 2:21 pm:Hi there,
I am reading the SCOM... don't ask me why :) Up to the style which sucks, quite a lot of interesting details inside!!!
.

Nobody gonna blame you for that :)

Yes, the boiler heater in sim acts like a on/off switch With no A or B redundant power
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Re: Space Shuttle - Development

Postby amalahama » Tue Apr 14, 2020 11:39 am

Hello Thorsten, GinGin,

Would it be possible to add the fantastic GinGin advance tutorials from the fg wiki to the already quite thorough manual?

Having access to them offline, even being able to smoothly print everything with the same format would be a nice touch.
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Re: Space Shuttle - Development

Postby GinGin » Tue Apr 14, 2020 12:51 pm

amalahama wrote in Tue Apr 14, 2020 11:39 am:Hello Thorsten, GinGin,

Would it be possible to add the fantastic GinGin advance tutorials from the fg wiki to the already quite thorough manual?

Having access to them offline, even being able to smoothly print everything with the same format would be a nice touch.


Hello, Thanks.
I might be able to convert them to PDF, google drive and a link on the wiki (?)
And have a revisit of them also, so many changes realism wise in 2 years :)
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Re: Space Shuttle - Development

Postby amalahama » Tue Apr 14, 2020 12:58 pm

That would be amazing already GinGin :)
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Re: Space Shuttle - Development

Postby GinGin » Tue Apr 21, 2020 3:17 pm

Hello,

I am working a bit on Autolaunch.nas
I would like to introduce a gamma target instead of an hdot target past mach 23 for MECO.


I understand how the hdot error worked and how it is coded :

Code: Select all
<fcs_function name="systems/ap/launch/stage4-hdot-error">
      <function>
         <difference>
            <property>velocities/v-down-fps</property>
            <property>systems/ap/launch/hdot-target</property>
         </difference>
      </function>
      </fcs_function>


But I have some trouble to find where the property "systems/ap/launch/hdot-target" is defined in the ap.xml to appear into ap/launch
I would like to create the same with " gamma-target" to be fed by a set prop in autolaunch.nas

And then gamma error etc based on the hdot error,stage4-pitch-PID-trigger and stage4-target code.

Code: Select all
<fcs_function name="systems/ap/launch/stage4-gamma-error">
      <function>
         <difference>
            <property>flight-path/gamma-deg</property>
            <property>systems/ap/launch/gamma-target</property>
         </difference>
      </function>
      </fcs_function>


Thanks for the help.
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Re: Space Shuttle - Development

Postby Thorsten » Tue Apr 21, 2020 5:56 pm

But I have some trouble to find where the property "systems/ap/launch/hdot-target" is defined in the ap.xml to appear into ap/launch


It isn't - targets are set from Nasal (autolaunch.nas) and the job of the AP JSBSIm tags is to achieve them, so the easiest way is to compute per cycle the hdot target that corresponds to the current gamma target. The harder option is to introduce a conditional into the JSBSim definitions and follow either hdot or gamma with a suitably tuned PID.

But the first really would do pretty much the same and save you much trouble.
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Re: Space Shuttle - Development

Postby GinGin » Wed Apr 22, 2020 9:27 am

Thorsten wrote in Tue Apr 21, 2020 5:56 pm:
But I have some trouble to find where the property "systems/ap/launch/hdot-target" is defined in the ap.xml to appear into ap/launch


It isn't - targets are set from Nasal (autolaunch.nas) and the job of the AP JSBSIm tags is to achieve them, so the easiest way is to compute per cycle the hdot target that corresponds to the current gamma target. The harder option is to introduce a conditional into the JSBSim definitions and follow either hdot or gamma with a suitably tuned PID.

But the first really would do pretty much the same and save you much trouble.


I see thanks.

I am trying something.
I put a gamma target in space shuttle-common.xml
I put an extent into mission.xml and a var in autolaunch.nas
Below mach 23, ap takes hdot and above gamma target.

Then that:

Code: Select all
 <fcs_function name="systems/ap/launch/stage4-gamma-error">
      <function>
         <difference>
            <property>flight-path/gamma-deg</property>
            <property>systems/ap/launch/gamma-target</property>
         </difference>
      </function>
      </fcs_function>
      
      <deadband name="systems/ap/launch/stage4-pitchgamma-PID-trigger">
         <input>systems/ap/launch/stage4-gamma-error</input>
         <width>0.01</width>
        </deadband>
      
      <pid name="systems/ap/launch/stage4-pitchgamma-target">
         <input>systems/ap/launch/stage4-gamma-error</input>
         <kp> 0.3 </kp>
         <ki> 0.0 </ki>
         <kd> 0.0</kd>
         <trigger>systems/ap/launch/stage4-pitchgamma-PID-trigger</trigger>
         <clipto>
            <min> -30.0 </min>
                 <max>  35.0 </max>
         </clipto>
      </pid>
      
      


And now playing with the PID.
I think I need to implement a conditionnal like you said to either have one ( hdot Pid) or the other ( gamma Pid) active in stage 4.
I will see if I can add another trigger velocity related or something like that.
Quite entertaining to learn those things.
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Re: Space Shuttle - Development

Postby GinGin » Sat Apr 25, 2020 7:05 pm

Some nice steps.
The gamma thing works quite well coupled to Hdot PID
I fixed TMECO by setting correct 100 % thrust and some other minor stuffs .

Initial MECO altitude is 345000 feet now.
Here targeting for a 0.23 ° path at MECO and a 125 Nm apogee ( MECO Vi is the variable then)
Close enough :)
I did a wide range of tests, different payloads, and loft. Apart the need to adjust sometimes the second stage angle in mission.xml, it is on the spot, especially with the h dot guidance that Thorsten made, putting us back on the good traj with some slight altitude deviations.
I also adjusted the TAL MECO altitude at 360000 feet and a very shallow fligh path angle ( 50 ft/s) like in books. Working very well.

Image


It works well with lofting and MPS/SRB angle bias
Here loft of 60000 feet for a MECO at 400000 feet ( like first STS missions)

Image


I almost finish the first stage opened loop.
Path is less lofted at SRB sep ( 30 ° vs 45 ° before, hence the need to modify a bit stage 2 initial Pitch target)
Really close to real datas, and adjustable with SRB loft angle.
Also , I added a more lofted traj ( 35 °) in case of an early engine failure to not be too far for RTLS selection at 2mn30 ( based on real datas also)

Here at max Q after an 180 ° roll ( so even more margin with no roll and heading 270 for lift off)

Image
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Re: Space Shuttle - Development

Postby Thorsten » Sun Apr 26, 2020 5:34 am

I guess we're happy to take merge requests once you're satisfied with the results :mrgreen:
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