Flight Question n00bish DeOrbit question

[Usquanigo]

So I can generally make it back down, especially in the XR series with it's awesome AoA attitude hold. And final touch-down isn't a problem either. And I can change Inc. to have my orbit cross the target base.....

But how do I know when to do my burn and for how long? I've searched this and I keep seeing things like 17,000 or even 18,000, but that seems to be only half the info, unless I'm missing something (which I think I am lol).

Ok, let's say my orbital plane is lined up for KSC, and I'm in that range, and facing retro-grade for a firing.... how far should I drop my PeA?

I've always been afraid of dropping it too far, lest I become a large ball of expanding incandescent gas and fragments. But by not setting it far enough, I run the risk of over-shooting.

 

[TSPenguin]

There is experience. I learned it by endless trial and error runs...

AerobrakeMFD is a tool that helps a lot.
It is often said that an entry angle of 1° is preferable. From my experience I can reenter the XRs at much higher rates.

Edit: Chat speak is frowned upon in this forum. Please don't attempt any more to be 1337. These things belong in the offtopic section only, and even then only if they are appropiate. Thank you.

 

[Poscik]

Shuttle makes de-orbit burn 180° from base and drops PeA to ~55km.

 

[Scarecrow]

Shuttle makes de-orbit burn 180° from base and drops PeA to ~55km.

Are you sure? I thought they dropped it to -20km.

Anyway, through trial and error, I've determined for DGish craft, some good numbers (with wiggle room) are:

Reentry from LEO: When you're 180° from your target, drop your PeA to 50km.
Aerobraking from the Moon: put your PeA at 60km and go in upside down.
Aerocapture from a Mars to Earth Hohmann transfer orbit: put your PeA at 70km and go in upside down.

You should be able to interpolate/guess reasonable numbers for other orbits from these data points. For example, from GEO, 55km is probably a fine number.

 

[Tommy]

If you use AerobrakeMFD, use the view that looks like MapMFD, de-orbit 180 degrees from base, and stop burn when green line ends at base (as noted before, this will be about 50k PeA).

On the other hand, if you're good at handling a more rigorous aerobrake, de-orbit about 14.2 M from the base, and go for a PeA of about zero, or a little less.

Aerobraking from the Moon: put your PeA at 60km and go in upside down.

That will fry a DGIV, 70k (inverted) works well for all aerocaptures.

 

[penlu]

I am also an aeroentry noob. Do you mean upside down by heat shield facing upwards? And what does this end up doing?

And how do you instruct a DGIV to reenter inverted?

 

[HiPotOk1978]

you got it, heatshield facing away from the planet. If you are going to try to do reentry inverted, your gonna be at the controls, not the Flight computer

 

[Tommy]

I am also an aeroentry noob. Do you mean upside down by heat shield facing upwards? And what does this end up doing?

For an example / tutorial on inverted re-entry (using the XR2 Ravanstar) see the following link:
[ame="http://www.orbithangar.com/searchid.php?ID=3660"]Home Direct[/ame]

This now includes a PDF manual by markl315, and the filename mismatch has been corrected so it can simply be unzipped into the Orbiter root folder (keeping folder names intact), and it will work. Flight recording with anotations will be located in the Scenarios/Tutorials folder, manual in the Docs folder.

This also covers an entire return trip from Brighton Beach to Cape Canaveral using IMFD, however, IMFD is not required to view this flight. AerobrakeMFD was also used, but not needed to view the flight recording.