Burning during re-entry

[george7378]

Hi all,

When I am re-entering using the AeroBrake MFD, I align the grey and yellow lines before re-entry, but as the re-entry commences, the ship's AoA usually changes, and I burn to keep the grey and yellow lines together. Is this what usually happens?

Thanks.

 

[the.punk]

No.

You control your reentry with the AOA.
You must use controlsurface and maybe RCS to control your AOA.
When you must burn during reentry you made something wrong.

 

[ar81]

AerobrakeMFD brings a very bouncing AoA.
Using an alternative MFD or craft may bring you to a stable AoA.
DGIV is a good example.

This might help
[ame="http://www.orbithangar.com/searchid.php?ID=3428"]Tutorial: Concepts for atmospheric reentry[/ame]

 

[brandonman]

Another note: I have only done 2 manual re-entries with the DGIV, and one went fairly smoothly (Except for falling short of Wideawake Int'l) The first one, I was going really well, and suddenly my nose pitched down. I tried wrestling the joystick to get it up, but it wouldn't go. BOOM, goes the DGIV. Turns out, I needed to change the dial in the main cockpit view to Elevon and Gear? and then turn on RCS - ROT in the other view that just shows the two MFD's. Hope this helps.

 

[george7378]

Right, so what I learned from that tutorial is:

- At 90 degrees from base on the BaseSync MFD, burn until the 1st line's distance is pretty much 0.
- Opposite the base on the Aerobrake MFD, burn until the gray line is on the yellow line, and set 40 degrees on the AoA hold in the DGIV.
- Re-enter

I have one question:

When I hit the atmosphere, the impact point changes. Should I just leave it? (Experience tells me I should).


EDIT:

Or do I change AoA in the autopilot?

Thanks.

---------- Post added at 06:25 PM ---------- Previous post was at 06:16 PM ----------

Basically, does this image mean I'm doing OK?:

---------- Post added at 06:48 PM ---------- Previous post was at 06:25 PM ----------

Well, it worked, and I didn't even have to fire my main engine :

I am wondering though, is there a way to make minor adjustments to AoA on the autopilot?

 

[EnDSchultz]

The DGIV autopilot can only be adjusted in 5 degree increments by using the numberpad keys, as far as I know. 'Tis why I personally prefer the XR series spaceships in this respect, since their attitude hold autopilots allow you to tune your AOA to within half a degree.

In any case, congratulations on a successful re-entry! =D

 

[Ark]

Burn at 180 degrees and set your PeA to 60k. I find it saves fuel and makes for an easier reentry.

The Aerobrake MFD's AoA is a pain to use, if you turn time acceleration on it tends to pitch wildly and kill you. I usually have to counter that tendancy with the RCS. XRs are real nice to land, though.

 

[Tommy]

First, remember that Aerobrake doesn't consider the atmosphere until you are under 200k altitude. Usually, you'll be de-orbiting from higher. Aerobrake is predicting your trajectory in a purely ballistic fashion. Don't even bother with setting an AoA until you are under 200k, I usually start orienting around 150k.

If you burn opposite the base, a PeA of 40k - 60k works well. You'll have a "bouncy" re-entry, but you won't burn up.

I find Aerobrake is a lot easier to use in it's map view. Hit the MOD button to get "Graph/Map" mode, then hit PROJ until you see the worldmap. Then just keep the endpoint at your target by adjusting the bank and AoA as you go.

You can eliminate sonme of the bouncing by de-orbiting closer to the target, about 17.5M if you are coming from the ISS.

 

[ar81]

Conditions for a cold entry:
1.Less vessel mass as possible
2.Deorbit at low altitude, preferably just above 150 km
3.Entry angle < 1 degree. I usually deorbit in the opposite side of the planet.