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FG Space Shuttle: the Van Allen mission

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FG Space Shuttle: the Van Allen mission

Postby eatdirt » Sun Nov 11, 2018 3:25 pm

Hi there, a few snapshots of an unprobable voyage with our FlightGear Space Transportation System (STS).

How far the Shuttle can go? But more relevant, from how far can we come back?

I am a newbie to FG, just landed a couple of months ago here because you people just created the perfect simulation for one of my childhood dream, the Space Shuttle. I was 6 years old when it flew, and I still remember watching the news about it. My nickname here is a good summary to what happens when I am in command, so don't be surprised of what follows :)

Lunch from Kennedy Space Center, with a very special Shuttle. Two of our best engineers have fitted in the payload bay the "Thorsten & Wlbraag" OMS payload kit: an extra reserve of fuel for the Orbital Maneuvering System (OMS, the two hydrazine engines at the back pods of the Shuttle). We also have a scientific payload to explore the inner Van Allen belt, a region where ionized particles get trapped in between 600 and 4000 miles. This is where we go today!

But we want to go back too, so we've started with an inclination a bit higher than the latitude of KSC, at about 39 degrees. You'll see why that's important later on.

Ignition, and leaving home:

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Our first challenge is to reach straight a high elliptical orbit, with an apoapsis at 800 miles, full power on the Main Propulsion System (MPS, the three eco-friendly monster engines at the back, they produce water!). Full power means we force the Throttle to the ABORT rating of 109% :shock:

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Main engines off, external tank separated, fuel dumped done, where are we? As planned, although we're far from any reasonable settings: altitude at apoapsis 810 miles!!! Not so incredible though, the automatic lunch guidance system is actually made by the very same Thorsten: in the FG Space Shuttle, we're in good company, even far from the allowed.

But that is only halfway to our mission. Let's burn almost all the OMS 2 pods reserve, and kick the Shuttle again by a velocity change of 800 ft/s. Why not all? The small amount remaining will be kept from going back...

In the picture below, CUR means our current orbit, TGT means what we're targeting:

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Burn ON, and ON for long. Here we go reaching Spain, with OMS engines vomiting their toxic yellow flames (these are all but eco-nice):

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Till extinction at an altitude of 380 miles. Very long burn, we've reached an orbit not exactly as planned HA=1372, HP=104, but that's even better, the periapsis at 104 miles means that we will not re-entering the atmosphere, perfect.

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Now, we can relax. We still have the full OMS payload kit to burn to increase again the apoapsis. But the burn should be done at periapsis, in a bit less than a full orbit. We deal with all the thermal management issues of the Shuttle, in summary we switch on a lot of heaters and cooler to avoid various lines freezing and various hot stuff burning!

And then, let's kick the Shuttle again by a velocity change of 500 ft/s, burn on again all over the Atlantic, here leaving the East Coast

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Done, this time, almost as planned. Current orbit reaches an apoapsis higher than 1800 miles, we'll be exploring the MEO zone, within the inner Van Allen belt.

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Ten hours of flight, time to release the payload, above South America. This Van Allen probe actually looks like exactly as the SPARTAN-201 satellite, but that's really a Van Allen probe ;)

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Takes some time to use the arm, but here we go, attached and released into Space:

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That's about how far we are (finally got my screensaver snapshot!!!).

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And now, the big problem... How do we go back with almost no fuel?
Hitting the atmosphere at Mach 29, with the same parameters as for the normal flights produce fireworks. We have too much speed! Thanks to GinGin, this is what the Shuttle is capable of at re-entry, not too much:

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Solution: atmospheric braking, we do not attempt of full re-entry, but only bounce on top of the atmosphere to loose a bit of energy, within the thermal limit of the Shuttle.

How to get this? Tune the orbit such that the flightpath angle at re-entry remains lower than the ones in the above picture. With some basic orbital mechanics, that you can get here:

reentry.py

we find that getting a safe flightpath angle of about 2.4 degrees can be obtained if, starting from our current orbit HA=1800 HP=100, we lower the HP at about 44 miles. This needs a small amount of fuel, less than the remaining 20% of the tank reserve. And that's what we get at re-entry, we pass over Earth and rise again to a new orbit (see the Shuttle symbols on the screen, far above the nominal trajectory)

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The new orbit had HA=1114, HP=42. The process made us loose 700 miles of altitude at apoapsis, good job! The new orbit is again fine with thermal limit, so we wait again one more orbit to gentle bounce on the atmosphere. In between, we deal again with thermal management, cool the freon by opening the payload door, close them before re-entry...

And we repeat the process, here 3 times to land on HA=344 HP=31, which is now more or less ok to attempt a full reentry.

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In the following picture, we're making some small adjustments to rise the periapsis to 35 miles with the RCS thrusters.

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The reason being that we cannot choose the point at which we enter the atmosphere, we enter at periapsis. Therefore, we have to plan, three/four orbits in advance, where the periapsis will be, and it should be at about a few thousand miles from our landing site! That's one of the reason the have a inclination slightly larger than the latitude of the departure site, to also allow landing at the departure site.
Here, KSC was quite far, more than 4500 miles, so I chose the White Sands Space Harbor lake bed, but it was quite far too from the expected re-entry point, so we rise the orbit a bit to HP=35 miles. Once we sure, we finally make all the nominal re-entry procedure, fuel dump, and we go deep into the flames:

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HP at 35 miles was still a bit low, we lack some energy to reach White Sands, but, again the autopilot will do its best to get that energy back in the following minutes:

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Plasma trails and glows:

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West Coast in sight:

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and we're getting our energy back (the shuttle symbol gets closer to the nominal green curve)

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and now, the auto-pilot can work on targeting the landing site

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Almost nominal now:

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Last turns before the HAC (Heading Alignment Cone) that puts the Shuttle straight in front of the landing lane!

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Back on perfect:

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Passing down the sound barrier:

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And into the heading cone, manual control:

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We target the lake bed:

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Last moments, virtual lane appears on the HUD, we're a bit low on energy but no worry, and it's a lake:

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That's us "alive"

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That trip might actually make me the most incompetent flightgear user having flew the highest altitude?
I might also got the highest speed record, MACH 29.2 for the first atmospheric bounce :mrgreen:

Hope you'll try the Shuttle too, it rocks!

Cheers,
chris.
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Re: FG Space Shuttle: the Van Allen mission

Postby GinGin » Sun Nov 11, 2018 5:19 pm

Wow man, amazing :)

OMS Kit takes all its meaning here ahah.
Aerobraking with the Shuttle, smart idea and it looks to work so weel . Very fuel efficient. NASA would love that :)


White Sands, love that base. Good luck to clean all the thin particle of sands inside all the pipes now ahah

For the Periapsis, you can try to play with the VZ radial component to move the shape of the line of apsides.
It works quite well combined the LEO tool and either PEG 4 or 7 for deorbit burn


Well done again, it's cool to read experience through screenshots like that
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Re: FG Space Shuttle: the Van Allen mission

Postby wlbragg » Sun Nov 11, 2018 5:23 pm

Well done again, it's cool to read experience through screenshots like that

Yes it is and what a fun adventure and storytelling!

That was a really cool mission and I can't wait for the Van Allen data to start poring in. :wink:
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Re: FG Space Shuttle: the Van Allen mission

Postby Thorsten » Sun Nov 11, 2018 5:49 pm

You guys are crazy, that's all I have to say :mrgreen:
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Re: FG Space Shuttle: the Van Allen mission

Postby GinGin » Sun Nov 11, 2018 6:24 pm

For sure Eat Dirt is one of test pilot xD
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Re: FG Space Shuttle: the Van Allen mission

Postby eatdirt » Mon Nov 12, 2018 10:39 am

Thanks guys, yes, that sounds that what I am doing here is really a test and crash pilot :)

For the storytelling, I am just mimicking Gingin style, I am finding it nice to read, and thanks Gingin for the suggestion of playing with Vz for moving the periapsis. I'll try that next time.

White Sands are perfect for my beginner flying, plenty of space to land the Shuttle. And for the dust, fortunately, Thorsten has not coded that yet within the sim :)

I did not write it, but, with a save/resume, I've also tried a landing at Vandenberg. That was amazing. My first try was a success by pure luck. The Shuttle had far too high energy and the AP did unbelievable things. Monster bank angles at the beginning, and then, at some point, the AP made the Shuttle plugging deep to compensate the too high altitude. A bit like the constant Nz in ABORT, at some point got 4g of deceleration when reaching again the nominal altitude. But at that point, I was already above the HAC cone. The AP did a quasi looping to put me on the last quarter of the HAC, and I finally succeeded to do the landing. I've tried two other times, but the Shuttle always broke apart. So, the safe option was indeed White Sands!

I should also try to push even further the MPS. I am still amazed by the AP that works fine for 800 miles of HA. I guess at some point, the conservation of energy will put the HP well below REI and there will be some trade-off with the OMS-1 burn to do.

cheers,
Chris.
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Re: FG Space Shuttle: the Van Allen mission

Postby Thorsten » Mon Nov 12, 2018 10:58 am

And for the dust, fortunately, Thorsten has not coded that yet within the sim


Wayne might have - I was surprised when I tried landing in rain that we have a pretty impressive spray simulation - I vaguely remember we had more dust off a runway.

I am still amazed by the AP that works fine for 800 miles of HA.


At that point of the flight, it's a dead easy problem - you're essentially already orbital, so you just keep attitude and keep the engines firing till the calculated apoapsis reaches the desired value. Since the AP tries to give you zero vertical speed, you automatically place your periapsis at the MECO point (sort of...)

I'd like to tell you all to try out the 500, 1000 and 1500 OMS kit versions which I coded this morning, but SF seems to have issues and I can't access the devel branch. I hope that resolves on its own during the next day, otherwise we'll have to talk to SourceForge.
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Re: FG Space Shuttle: the Van Allen mission

Postby legoboyvdlp » Mon Nov 12, 2018 11:36 am

interesting video of the real thing:

and article:
http://www.americaspace.com/2013/03/30/ ... -of-sts-3/

very nice writeup :D

good job on staying alive!
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Re: FG Space Shuttle: the Van Allen mission

Postby eatdirt » Mon Nov 12, 2018 12:40 pm

Wow, the article is amazing, especially all the sh... with the AP!!!

I've just learned that we should put the landing gears on at 200ft, was still doing it with KEAS! Thanks!
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Re: FG Space Shuttle: the Van Allen mission

Postby wlbragg » Mon Nov 12, 2018 5:15 pm

@eatdirt I gather you land at White Sands after launching in Florida. Is there an actual runway designation in FG for the White Sands runway you land at or did you simply aim for the lake bed. I'm asking because I am trying to duplicate the landing you did but using the "On Approach" and both the AFB and the Regional airports in that area don't have that dry lake bed as part of their runways.
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Re: FG Space Shuttle: the Van Allen mission

Postby eatdirt » Mon Nov 12, 2018 5:20 pm

@wlbragg, yes!

This is in the last pages of the FG Shuttle manual by Thorsten. I've used the secondary runway, the NOR32, it is equipped with MLS for landing, but watch out, they are on channel 6, so you have to change the channel on the overhead panel from 8 to 6!

Up to this, this is exactly as landing elsewhere, with the advantage of that you can touch down earlier or later without having the frustration of being in the grass of stopping after the end of the runway :)
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Re: FG Space Shuttle: the Van Allen mission

Postby wlbragg » Mon Nov 12, 2018 5:52 pm

Up to this, this is exactly as landing elsewhere

Yeah, I was mostly interested in looking at the ground cover and how much dust effect we get with it. After looking at the video that lake bed kicks up a bunch of dust and I want the simulation to accurately depict it.
We do have water spray and dust effects but at the time I did them I really didn't look at much reference and now it is just a matter of a little tuning to get it to match reality. Thorsten has that FDM and all the systems tuned and so outstanding I really want the graphics and visuals to do that Justice.
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Re: FG Space Shuttle: the Van Allen mission

Postby GinGin » Mon Nov 12, 2018 7:38 pm

Nice link lego.
Complex spacecraft but not that dangerous like depicted in the article though :)


Nice Wayne :)
Some dust and sand effect for white sands and Edwards .

Some new ksc by LEGO.

And maybe some hd textures for thé shuttle

Christmas coming with all that work around the Shuttle.

So cool :)
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Re: FG Space Shuttle: the Van Allen mission

Postby Thorsten » Tue Nov 13, 2018 7:10 am

Shiny new OMS kit (1500 fps variant) in the payload bay :D

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Re: FG Space Shuttle: the Van Allen mission

Postby GinGin » Tue Nov 13, 2018 10:03 am

Very nice works guys
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