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Re: Space Shuttle

Postby Thorsten » Fri Jul 22, 2016 6:03 pm

Tried for an emergency landing in Bermuda today - the first attempt was about 140 miles short (okay, it's hard to estimate the precise ranges for the abort regions from the schematics in the manual, so no surprise here) - the second was probably okay, but then the AP lost roll control just before the hard part of the Nz pullout (I'm fairly sure there was a non-zero beta when Aerojet engaged, and it was trying to correct that while managing the pullout, which didn't go well). Surprisingly I lived to see 70.000 ft, but then it all spiraled out of control.

Aerodynamically the contingency aborts are just an extremely challenging regime - basically the AP needs to change within a few seconds from 'only thrusters do anything' to 'thrusters are far too weak to do anything' to 'airfoils start to jam because qbar is so high' - while you reach vertical speeds of 800+ m/s (!).

Yeah, that's right, the vertical speed is more than most planes will ever go horizontally...

Anyway, I think I'll just leave the remaining engine on for a few seconds more to stabilize the situation next time (I already updated the Bermuda regional texturing to show something closer to reality - seems it's quite densely populated...). Also there's now TAEM guidance for the airport - manage approach carefully, the runway isn't that long :-)
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Re: Space Shuttle

Postby Thorsten » Sat Jul 23, 2016 6:13 pm

Made it - the most expensive holiday trip ever I guess:

Start with a regular launch, TAL abort after the first engine failure some 3 minutes into the flight, down-moded to contingency abort after the second engine failure.

Going through the contingency abort procedure (that's the original cue card available in-sim for easy reference):

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Kicking off the ET - in the GREEN region, it's actually disconnected via high rate sep (there's six different separation techniques for the ET in the upper atmosphere - RTLS and Contingency BLUE use alpha = -2, Contingeny GREEN uses high rate, and the other four are for when things are really going pear-shaped and you have no engines left...)

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What follows is a 3.4 g pullout, some following phugoid oscillations as the Shuttle flies the alpha-transition pattern starting at Mach 6 through the upper atmosphere, taking over the roll axis to CSS to aim at Bermuda, then letting the AP fly again.

Bermuda, here we come (I've added plenty of shipping traffic around the islands for enjoyment):

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And, a short-field touchdown (okay, I broke a gear strut...)

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Here's the trajectory:

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First wiggle is the TAL trying to steer northward to Spain, second (very small one) is the contingency yaw steering trying to steer south to Bermuda, and the third major one is my CSS takeover during supersonic flight. The HAC is too small to be seen on the scale, but I basically made it right into the TAEM pattern without any S-turns and was delivered into a perfect final from 12.000 ft - messing up the touchdown was entirely my fault...

It's actually fun to pull off this kind of stunt...
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Re: Space Shuttle

Postby Thorsten » Wed Jul 27, 2016 5:54 pm

I've learned some interesting stuff trying to implement the contingency YELLOW procedure (that's one of the branches you execute if you lose one engine early on, abort RTLS and halfway into the RTLS lose a second engine - which is *very* awkward since you basically kill all speed during the abort).

The procedure involves using the remaining engine to slow down the descent by pointing it downward. Since the SSMEs actually are mounted at an angle, this means pitching up to 100 degrees (i.e. beyond the vertical, with the noise pointing against the flight path).

Now, that's a fun region since pitch gains formally reverse at the vertical, and roll changes from inverted to upright - which then needs to be changed back to inverted to be able to pitch down into the flight path again. And yaw becomes arbitrary at the vertical - so I had to freeze commands during the actual transit to not get artifacts.

In addition, JSBSim actually doesn't provide a KEAS if you are not pointed into the velocity vector (of course a pitot tube wouldn't show anything, but the Shuttle doesn't use air data at this point, it uses the IMUs in combination with an atmosphere model) - but the MECO condition utilizes KEAS - so I had a spectacular crash finding that out before I settled on using qbar as a proxy.

It's... fun. I wonder whether any existing AP in FG has worked in this region of alpha > 90 and beta ~ 180 degrees before.
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Re: Space Shuttle

Postby legoboyvdlp » Thu Jul 28, 2016 2:21 pm

I was interested to know what would happen if you lost all engines a few seconds after SRB separation ;)
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Re: Space Shuttle

Postby Thorsten » Thu Jul 28, 2016 2:51 pm

You likely die - it's marked as a black zone - no safe ET separation dynamics and bad entry conditions. You would try to follow the 3 out BLUE procedure I think - see the Contingency Aborts cue card in-sim for the details.
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Re: Space Shuttle

Postby wlbragg » Tue Aug 02, 2016 2:08 am

Finally some results to share on the creation of some cockpit lightmaps. It's pretty slow going because of the major blend/ac refactoring required. Note to anyone: think ahead when setting up your blend file and uv mapping. My lack of experience cost me quite a bit of time. But what the heck, that's how you learn, right?

This map isn't the final, it is more of a test than anything. As you can see there are still overlapping uv mappings, parts of the forward windows are mapped to the same texture location as some of the object that are the subject of this LM, but it's getting there.

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This image isn't completely dark, it has a small amount of illumination (.3). I somehow didn't manage to save the "light off" image.
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Kansas(2-27-15)/Ohio/Midwest scenery development.
KEQA (2-27-15), 3AU, KRCP Airport Layout
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Re: Space Shuttle

Postby Thorsten » Tue Aug 02, 2016 5:00 am

*Very* nice - even better than I was hoping for!
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Re: Space Shuttle

Postby Thorsten » Tue Aug 02, 2016 9:17 am

Here's the lighting for a night launch during SRB separation.

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Initially as the separation motors ignite there's a bit more light on the front of the orbiter, then as the boosters drop behind their flame light disappears from the orbiter and only they themselves are lit.
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Re: Space Shuttle

Postby legoboyvdlp » Tue Aug 02, 2016 12:23 pm

Whoa. Whoa.
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Re: Space Shuttle

Postby D-ECHO » Sat Aug 06, 2016 3:09 pm

Thorsten, your Bermuda pictures inspired me to make a Bermuda custom scenery ;)
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If you're interested, viewtopic.php?f=5&t=30157
Thanks :D
PS: As you see, my picture looks different from yours, do you have a special material file?
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Re: Space Shuttle

Postby Thorsten » Sat Aug 06, 2016 5:17 pm

It's very pretty - could we try to get it to Terrasync?

PS: As you see, my picture looks different from yours, do you have a special material file?


Yes - but it should be pushed by now. I suppose you need one for your scenery as well - spruce in Bermuda? :mrgreen: These trees grow in our yard in central Finland... (literally these, I made these textures from pictures of them).
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Re: Space Shuttle

Postby Octal450 » Sat Aug 06, 2016 6:22 pm

cool stuff @Thorsten @D-ECHO
Waste of time. Goodbye forever.
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Re: Space Shuttle

Postby Thorsten » Thu Aug 11, 2016 2:44 pm

Hooked up the LCD screens to the electrical system. You can now see which screens hang on which bus by disconnecting that bus from the fuel cell. Also, power consumption will be reduced if you dim the LCDs or switch them off (I know it's a bit over the top, but I'm imagining a situation in which you have just very limited power available and need to carefully switch off systems to get the operational voltage high enough to do an emergency de-orbit...)
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Re: Space Shuttle

Postby legoboyvdlp » Fri Aug 12, 2016 2:34 pm

Awesome. This sure sounds amazing.
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Re: Space Shuttle

Postby amalahama » Mon Aug 15, 2016 4:14 pm

Thorsten wrote in Thu Aug 11, 2016 2:44 pm:Hooked up the LCD screens to the electrical system. You can now see which screens hang on which bus by disconnecting that bus from the fuel cell. Also, power consumption will be reduced if you dim the LCDs or switch them off (I know it's a bit over the top, but I'm imagining a situation in which you have just very limited power available and need to carefully switch off systems to get the operational voltage high enough to do an emergency de-orbit...)


You have Apollo XIII film in your mind, don't you :D

It would be nice to have a second "launch" scenario from Vandenberg AFB and try to reach a polar orbit, as intended in STS-62 before Challenger accident. It's a specially interesting "what if" scenario. I don't know if current systems and autopilot could cope with it though. Neither in the sim or real life.

Any news about the overhead panel? This beauty is begging it badly.

Regards!
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