Problem aerobrake Probs

[Interceptor]

Hi Guys my DeltaGliderIV keeps blowing up during reentry, or it overshoots and undershoots KSC. Anyways I have been using aerobrake and I deorbit burn until the green line is exactly over KSC on the map display for aerobrake. But then I look on the stock map display and the orbit impact orange block won't appear, so I burn longer until it appears, but this in turn makes me undershoot the base. So I get it the green line as close as possible to KSC, and my ship always explodes during reetry. And I am using the stock reentry autopilot to guide me in. The closest I have ever came to KSC was 300KM. confused thanks

 

[tblaxland]

The map display won't take into account the effect of the Earth's atmosphere on your trajectory when it calculates where the orange(?) part of the orbit is. That part of the orbit is calculated to be below the surface by pure orbital mechanics. Aerobrake MFD is a bit smarter in that it will predict your path through the atmosphere based on your current angle of attack. Hopefully that explains the difference between the two MFDs.

 

[Tommy]

The Deorbit burn should take place on the opposite side of the planet, at least 18M from the base. Do the deorbit burn until AerobrakeMFD shows the green line ending at the base. MapMFD will still be all green, your PeA after deorbit burn is usually just under 50k.

Once you've descended BELOW 200k, adjust your AoA with the Autopilot until the green line on AerobrakeMFD ends at the base. Since the DGIV adjusts the AoA in five degree increments, you probably won't get it right on the base, it will either be short or long. Start with it short, and watch your hull temps (press "d" then "3" to see the reentry display) When it gets too hot, lower your AoA. It's a good idea to watch your VS in SurfaceMFD, and keep it above -100 m/s, lower the AoA to raise it if needed.

Once you get closer to the base, you can tune in the descent better - a five degree AoA change won't make as much difference to your endpoint as it does early on.

Remember, AerobrakeMFD doesn't account for aerodynamics (wings and lift) until you are under 200k altitude, and shows the path at your current AoA.

 

[Interceptor]

Thanks Gentleman it's tricky but i'll get it


-----Post Added-----


Hey whats the Hypotetic V Delta button, for on aerobrake. And do you guys also use basesync, and how the heck do you use that. I read the vague instructions and messed with it a bit. and all I could get from it, is it tells you how many orbits you pass before you encounter a base Thanks again

 

[Tommy]

I've never used Hypothetic Delta-V on aerobrakeMFD, but I believe it's used to help plan an Aerocapture maneuver, and not used for a re-entry.

As for Basesync, it's actually pretty easy to use once you know how to set it up. Press <TGT>, and type in the name of the base. If you're not sure the exact name of a base, use "Object Info" (found in the main (F4) menu)). It's not case sensitive, don't worry about capitalizing. Press <MOD> to enter "closest approach" mode. Press <E/D> to get into "Direct" mode.

At the bottom, one of the lines will be in white. That's the closest pass. It may change after a few orbits if a closer pass is coming. You can "force" Basesync to use a sooner orbit by pressing <NUM> and entering in the number of orbits you want to consider.

If the closest approach is over 100k, I like to "prepare" by doing a plane adjustment a couple orbits before re-entry, especially if I'm in a low (200k) orbit, but you don't have to. Don't bother getting it closer than 50k, things change a little when you perform the de-orbit burn.

Basesync won't count down to a node until the last node (after the de-orbit burn) so if you want to do a prep burn, check the Tn counter. If it's a negative number, use the opposite of the direction the PlC shows. In other words, if PlC shows a plus sign, you'll need to burn anti normal (Normal - ). This is only for burns before the last node. Since you won't get a TN countdown, just burn at the grey line (they should be 90 degrees from the target, if not check to see that you're in "Direct" mode, not "Equatorial".)

When you are on the last orbit, perform your de-orbit burn when on the opposite side of the planet. You can use MapMFD and burn when the distance starts shrinking, or just "eyeball" it using Basesync's display.

Basesync won't start the TN countdown until about one minute to the node, so if the TN number is negative, orient opposite the PlC sign. When you get to the last node (90 degrees before touchdown) burn to reduce the closest approach distance. For Canaveral, I like to head 20km south of the base to provide room for runway alignment. After that last alignment burn, orient for re-entry as normal.

 

[Interceptor]

Wow tommy great tutorial thanks

 

[Interceptor]

Hey Tommy. Sorry to bug you again. But when you say burn normal or anti normal a couple of orbits away at grey line using the basesync mfd. How long should I burn for and what do I use to indicate this. thanks

 

[Tommy]

Use the closest approach distance indicated by BaseSyncMFD. For instance, if the closest approach will be 300km on the second orbit, burn until that number is reduced to 75m - 100km. This isn't really necessary, but it helps reduce the burn time for the final alignment burn. Since the final alignment burn takes place 1/4 orbit from the target base (and after the de-orbit burn), you're usually well below 200k alt by then. A shorter burn just makes it a little easier to get the burn finished, and orient for re-entry, a little sooner. That way you're a little less rushed when using AerobrakeMFD to find the correct AoA to reach your target.