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Space Shuttle - Development

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Re: Space Shuttle - Development

Postby Thorsten » Tue Apr 09, 2019 9:52 am

Gentlemen, I can imagine you're all excited about the new features, the manual update etc. and like to play around and find the one or other thing.

But for me it's different - I really need a break from Shuttle work, I want to fire up my computer without doing some Shuttle test or bugfix for a bit.

So if it's mission-critical and there's a massive error - please post and request a fix. But if it's just curiosity or some random oddity - please just make a note and we'll address it when I'm ready to resume Shuttle development.
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Re: Space Shuttle - Development

Postby GinGin » Tue Apr 09, 2019 11:31 am

No worries Thorsten, totally understable .
Thanks again for your work on that top notch milestone and manual
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Re: Space Shuttle - Development

Postby wkitty42 » Tue Apr 09, 2019 3:36 pm

legoboyvdlp wrote in Mon Apr 08, 2019 8:53 pm:Bottom left, ULL P LH2 :)

oh! so there's 3 locations where that data is output... coolio...
"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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Re: Space Shuttle - Development

Postby legoboyvdlp » Tue Apr 09, 2019 4:04 pm

That specific measurement is "ullage" pressure which according to my google search is basically the pressure between the top of the propellant and the top of the tank :)
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Re: Space Shuttle - Development

Postby eatdirt » Tue Apr 09, 2019 4:09 pm

Gentlemen, I can imagine you're all excited....


:mrgreen: Oh yes we are!

Sure, by no means I meant to ask you to fix these little things, that also applies to Wayne who is doing a lot of 3D fixing. I had in mind to mention this here, in the devel thread rather than the bugfixing thread as a memo for future polishing, is that ok or you would prefer the other way around?

You and Wayne certainly deserve long holidays, far from our noisy excitation, granted!! :)

Thanks again!!!
Cheers.

PS: Thanks Gingin for the link, done, works like a charm.
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Re: Space Shuttle - Development

Postby eatdirt » Thu Apr 11, 2019 8:32 pm

Hi there,
I am sorry to make that little noise again, but I got again that issue with tracking the ISS, and this time, I can be a bit clearer, while not yet enough to nail the issue I guess.

First or all, the issue is not showing up all the time, for instance, soon after orbit insertion, everything is fine, it seems that I am encountering the problem when I am around ~200km from ISS :(

It has nothing to do with the star tracker, let's assume it is tracking stars, but we just have RDV NAV ENA (ITEM 1) in SPEC 33. In OPS 201, when tracking ID 1 (ITEM 8) with the -Z body axis (ITEM 14 +3) with Omicron vanishing (ITEM 17 +0), the Shuttle never manages to reduce the errors on Roll and Yaw, they actually oscillate while growing. There seems to be an instability, the REQD value for Roll reads +180.0 while the actual R reading seems to go further apart from +180.0, especially when trying to reduce the one on Yaw, and conversely.

From that unstable state, if I switch back ITEM 14 +1 to the X body axis, the pointing is fine, no issue. Back to ITEM 14 +3, pointing impossible. Then, I have tried to enter a value of Omicron ITEM 17 +0.01, and here we go, the pointing was fine along the -Z axis!

Edit: this is happening on a regular basis between 100km/200kmish from ISS, it looks like the Shuttle gets locked into that position, exactly as if it was locked into an Euler singularity in the error angles!??

Image


Cheers,
Chris.
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Re: Space Shuttle - Development

Postby Thorsten » Fri Apr 12, 2019 4:01 am

For tracking something that's not in an inertially fixed position but slowly moving, the deadbands of the default DAP-A are far too tight. Any roll correction induces a small yaw, any yaw a small roll, and if you require near-zero errors, it gets hard to do.

The manual actually describes the deadband issue. :D

But... deadbands can be configured on SPEC 20. Or i-loaded. Or you can try DAP-B - the precision you need for the star tracker is 10 deg - you even have a chance to doe this manually based on guesswork.
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Re: Space Shuttle - Development

Postby eatdirt » Fri Apr 12, 2019 7:51 am

Thanks Thorsten, I'll try that. I think I spotted a problem with SPEC 20, first time I am using it:

Image

In the DAP B column, some items are degenerated, for instance there are two items 33 such that we cannot change DAP B ROT DB, it only changes the latter, ROT PLS :) There are also 2 items 44 in the same column. I spotted also 2 items "24" and 2 items "64" (vernier buffer).

Cheers,
chris.
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Re: Space Shuttle - Development

Postby Thorsten » Fri Apr 12, 2019 8:02 am

They're probably just graphics glitches (copy/paste errors of lines in the display layout).
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Re: Space Shuttle - Development

Postby GinGin » Fri Apr 12, 2019 3:54 pm

@EatDirt: Yes, just graphic glitches. Item works well

I can advise you to directly modify that in the mission config file ( like that, for trans dap in MM 104,5,6 and OPS 3, you will have smoother deadband also)




Code: Select all
<dap>
  <section-defined type="bool">true</section-defined>
  <dap-A-PRI-rot-rate type="double">2.0</dap-A-PRI-rot-rate>
  <dap-B-PRI-rot-rate type="double">0.5</dap-B-PRI-rot-rate>
  <dap-A-VRN-rot-rate type="double">0.1</dap-A-VRN-rot-rate>
  <dap-B-VRN-rot-rate type="double">0.05</dap-B-VRN-rot-rate>
  <dap-A-PRI-att-db type="double">0.05</dap-A-PRI-att-db>
  <dap-B-PRI-att-db type="double">0.10</dap-B-PRI-att-db>
  <dap-A-VRN-att-db type="double">0.12</dap-A-VRN-att-db>
  <dap-B-VRN-att-db type="double">0.10</dap-B-VRN-att-db>
  <dap-A-PRI-rate-db type="double">0.05</dap-A-PRI-rate-db>
  <dap-B-PRI-rate-db type="double">0.1</dap-B-PRI-rate-db>
  <dap-A-VRN-rate-db type="double">0.001</dap-A-VRN-rate-db>
  <dap-B-VRN-rate-db type="double">0.005</dap-B-VRN-rate-db>
  <dap-A-ALT-rate-db type="double">0.2</dap-A-ALT-rate-db>
  <dap-B-ALT-rate-db type="double">0.2</dap-B-ALT-rate-db>
  <dap-A-PRI-rot-pls type="double">0.1</dap-A-PRI-rot-pls>
  <dap-B-PRI-rot-pls type="double">0.05</dap-B-PRI-rot-pls>
  <dap-A-VRN-rot-pls type="double">0.01</dap-A-VRN-rot-pls>
  <dap-B-VRN-rot-pls type="double">0.002</dap-B-VRN-rot-pls>
  <dap-A-PRI-comp type="double">0.0</dap-A-PRI-comp>
  <dap-B-PRI-comp type="double">0.0</dap-B-PRI-comp>
  <dap-A-VRN-comp type="double">0.0</dap-A-VRN-comp>
  <dap-B-VRN-comp type="double">0.0</dap-B-VRN-comp>
  <dap-A-PRI-p-opt type="int">0</dap-A-PRI-p-opt>
  <dap-B-PRI-p-opt type="int">0</dap-B-PRI-p-opt>
  <dap-A-PRI-y-opt type="int">0</dap-A-PRI-y-opt>
  <dap-B-PRI-y-opt type="int">0</dap-B-PRI-y-opt>
  <dap-A-PRI-tran-pls type="double">0.100</dap-A-PRI-tran-pls>
  <dap-B-PRI-tran-pls type="double">0.100</dap-B-PRI-tran-pls>
  <dap-A-ALT-n-jets type="int">3</dap-A-ALT-n-jets>
  <dap-B-ALT-n-jets type="int">3</dap-B-ALT-n-jets>
</dap>
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Re: Space Shuttle - Development

Postby eatdirt » Fri Apr 12, 2019 8:05 pm

Thanks Gingin, these numbers are indeed much needed, spent 1 hour playing with them :)

Edit: I don't understand, these values are actually not loaded!? Putting them in SpaceShuttle/Mission/mission.xml, SPEC 20 always give me the same numbers as before. Is there something I am missing? Does the mission.xml file has to be explicitly given in the command line?
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Re: Space Shuttle - Development

Postby Thorsten » Sat Apr 13, 2019 4:50 am

Most likely you have section-defined to 'false'
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Re: Space Shuttle - Development

Postby eatdirt » Sat Apr 13, 2019 7:33 am

Most likely you have section-defined to 'false'


Damned....... :oops: the obvious!!! THANKS!
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Re: Space Shuttle - Development

Postby eatdirt » Sat Apr 13, 2019 9:59 am

Ok, screwed up my first two attempts to enter into the proximity zone, that's not easy :) In addition to my stupid mistakes with the configuration DAP, in my last attempt I forget I was in THC mode and I was trying to track ISS. When I realized the mistake, I had already created DVy > 60 ft/s... :shock:

Now, I have a beer to relax, my kids are away, the week-end for me and a piece of paper nearby for doing basic orbital mechanics timings... I am Lambert targetting from ha=100nm to ISS. Now I understand the manual saying you have to be precise, just 30 seconds off from the optimal time and bang, Delta VZ gets immediatly a few decaft/sec. Prep well in advance, I am now -11minutes from firing with DeltaVz=3 and DeltaVx=129, I am excited :)


cheers.
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Re: Space Shuttle - Development

Postby GinGin » Sat Apr 13, 2019 2:38 pm

Nice Eat Dirt.
Take pictures and do a report of your first time with the rendez vous :)
Yes, 30 s at 27000 ft/s is like 100 Nm ish of distance flown.

Swiss Watch precision we need there :)
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