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Meeting ISS

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Meeting ISS

Postby Thorsten » Mon Jan 21, 2019 1:03 pm

Doing the last leg to ISS, from a phasing orbit about 15 km lower and 120 km behind right to a vbar stationkeeping position off ISS.

Preparation starts during dusk over Africa - see the illumination on the horizon? That's a tropical thunderstorm raging...

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The on-board Lambert solver spits out a transfer solution:

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The solution gets transferred to MNVR and translated into a burn program:

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Egypt and the Nile delta seen out of the window while the Shuttle moves into burn attitude (the terrain is unusually bright since we have full moon illuminating bright desert sand here...)
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The transfer burn with Israel seen in the foreground:

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Aurora on the horizon as we pass over central Asia.

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The Lambert solver spits out a trajectory correction:

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After we've burned the correction, it provides the braking burn:

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Sunrise on the horizon...

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... and we fly into morning.

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Light plays on the interior as the Shuttle moves into attitude for the braking burn...

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The OMS fires with ISS already visible a few miles off

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And, after some manual corrections, the view through the overhead window - the Shuttle hanging in the vbar of ISS, ready to get closer whenever this is required.

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Re: Meeting ISS

Postby wkitty42 » Mon Jan 21, 2019 5:45 pm

"Nice work!" just doesn't seem to cover it ;)
"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: Meeting ISS

Postby ThomasS » Mon Jan 21, 2019 7:54 pm

Wow, fantastic! Both the shuttle interior and the earth in background.
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Re: Meeting ISS

Postby wlbragg » Mon Jan 21, 2019 8:05 pm

Stunning!
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Re: Meeting ISS

Postby eatdirt » Mon Jan 21, 2019 10:17 pm

Ooohhhh, we're doing to have a lot of fun very soooooonn!! Will the Deluxe manual get a new chapter on rendez-vous?
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Re: Meeting ISS

Postby Thorsten » Tue Jan 22, 2019 7:36 am

Will the Deluxe manual get a new chapter on rendez-vous?


Well, I suppose most people won't figure out how it works otherwise... :mrgreen:
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Re: Meeting ISS

Postby bugman » Tue Jan 22, 2019 12:39 pm

That is awesome! Have you used your c++ LEO targeting code for this? And have you used NASA's high resolution 3D model of the ISS?

Regards,
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Re: Meeting ISS

Postby GinGin » Tue Jan 22, 2019 1:19 pm

Awsome, what an achievement code wise :)

Do you use Spec 33 and RR tracking?
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Re: Meeting ISS

Postby Thorsten » Wed Jan 23, 2019 6:23 pm

Okay, let's continue where we left off - on the vbar of ISS. The Shuttle is not put vertical with the payload bay pointing towards ISS - that allows good operations of the Ku-antenna as radar ranging device. The REL NAV display shows the radar ranging data, while the Shuttle is piloted looking upward out of the overhead windows towards ISS.

Luckily, the controls can be adjusted to fly 'normally' from that perspective - in Orbiter I had docked stock Atlantis once to ISS where it isn't possible to switch the control sense, and I found my brain in a tight knot pretty fast...)

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Approaching on the vbar - orbital mechanics requires us to regularly null the vertical speed, the orbiter wants to go upwards relative to the station.

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Aiming below ISS to get into the rbar position...

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... and on the rbar, rotating and switching to LVLH mode to lock attitude with respect to the horizon (and ISS)

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Going up the rbar - when only a small upward velocity is used, orbital mechanics will provide a braking force, so we don't have to fire upward thrusters to brake, frying the station in the process...

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Nearly there (took a while, slow does the trick...)

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... and just before sundown, docked properly

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Docked to ISS now, nice aurora display around the South Pole:

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Just as the Rendezvous workbook states, the Achilles heel of the whole thing is the FRCS - most translation maneuvers use the FRCS, but its propellant can't be cross-fed from the OMS, so once it's gone, translation capability is gone. Thus, one would have to be really careful about conserving RCS propellant (my approach was far too hasty to be propellant-friendly...)
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Re: Meeting ISS

Postby GinGin » Wed Jan 23, 2019 8:30 pm

Impressive, well done
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Re: Meeting ISS

Postby wlbragg » Thu Jan 24, 2019 3:42 am

Really, wow!
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Re: Meeting ISS

Postby Thorsten » Thu Jan 24, 2019 5:53 am

Have you used your c++ LEO targeting code for this?


As with the PEG-4 targeting, it's a light-weight variant of it coded in Nasal.

And have you used NASA's high resolution 3D model of the ISS?


No - first I'm not a 3d modeler, but second, since FG doesn't support 'docking' we have to include any docked object as child model of the main spacecraft - which would make the Shuttle mesh another 80 MB heavier and increase loading time accordingly.

So even if we had a properly scaled and textured ISS, this problem would have to be solved.
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Re: Meeting ISS

Postby wkitty42 » Thu Jan 24, 2019 9:43 pm

Thorsten wrote in Thu Jan 24, 2019 5:53 am:So even if we had a properly scaled and textured ISS, this problem would have to be solved.

i can't help but to envision an AI aircraft carrier at a masquerade party wearing an ISS costume... as with the carriers, that could be expanded for MP use where someone "drives" the ISS... of course, there's not much to do, really. when driving the ISS... so with this idea then comes an F15 landing on the carrier would be kinda similar to the shuttle docking to the ISS... i think that works in AI and MP modes... yeah, there's some work to be done there if this comes to fruition ;)
"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: Meeting ISS

Postby Thorsten » Fri Jan 25, 2019 6:50 am

i can't help but to envision an AI aircraft carrier at a masquerade party wearing an ISS costume...


Short of computing orbital dynamics for an object, there's no way you can make it appear 'static' with respect to a Shuttle that's moving at Mach 27 so that you can dock. So basically all the ways to control AI motion don't work, they're far too simplified.

And as for MP, at that speed, an MP transmission delay of one frame will mean a few hundred meters offset.

Whatever object you choose, it needs a full J3 gravity solver underneath.

(Of course you can code a new orbital class of AI objects an define things such as docking ports there properly... It's not that it could not be done, it's just that I don't have the time to do it.)
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Re: Meeting ISS

Postby V12 » Fri Jan 25, 2019 7:14 am

Absolutly amazing. My poor english has not enough words for description.
Fly high, fly fast - fly Concorde !
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