Large Spaceplane Reentry?

[InterCity]

Hello, guys.

I got myself into a bit of trouble trying to get my shuttle orbiter back from orbit: I get the 75 km "landing" orbit and I try to just gently dip into the atmosphere (about 6000 m periapsis), but whatever pitch i use to enter the atmosphere, I get crispy at best. My best attempt so far ended up in landing gear and wing strakes exploding at about 20 km. I landed the steak anyway with my patented emergency chute system. However, I'd be happy if I could use the orbiter again after landing. What am I supposed to do (except for messing with cfg and using the cheat menu)?

Edited August 28, 2015 by InterCity

[MaverickSawyer]

I never target a PeA... I use Trajectories and burn half an orbit ahead, then wait until it's about 300 km short of the KSC. The wings will take care of the rest of the range, and a lifting reentry eases the heat load. I also tend to run with airbrakes out in the early phases, to help manage my speed.

That said, I've never cooked off a wing strake before. The only thing I've burned off was the basic fins (and anyone who's toyed around with those knows exactly why...), and that was on a particularly aggressive entry.

[Nich]

6 km is really low I normally set PE to 40-45 km and aerobrake until orbit runs into KSA

[RexKramer]

If you aren't using airbrakes, they are surprisingly effective. The airbrakes currently have a glitch where action group assignments don't work, they are effectively permanently tied to the brake group. I activate the 'parking brake' to deploy them prior to entry. This, combined with a 10 to 20 degree angle of attack, is working well. (Nose of vessel is pointed 10 to 20 degrees above prograde marker)

You might consider a steeper entry also. While your vessel is between 35 and 55 km, you generate a lot of heat, but not much drag, so you get hot but don't slow down.

Not saying this is ideal, but my descent starts with a burn about 90 degrees before KSC, so the orbit intersects (impacts?) KSC. Then I rotate to point prograde. At atmosphere entry, I deploy airbrakes if equipped, and try to hold pitch 10 to 20 degrees above the prograde marker. An unpowered plane will sometimes level off around 40km doing this, which you don't want- you're still generating a lot of heat but not much drag. If that happens, lower the nose a bit to keep the descent going.

[ajburges]

Time for the obvious question. Is your craft fuel tank near empty yet? Did you forget to deploy the payload?

Also keep high, you want drag, not momentum, to take you below 36 km. Laminar flow really kicks in below 24 km.

[Snark]

Reentry for spaceplanes is pretty easy, especially with airbrakes. Set the periapsis really high, and use lift to generate drag and keep your periapsis where you want it.

If you're reentering a lot faster than circular orbital velocity (e.g. coming back from the Mun), pitch nose-down to generate negative lift, to keep yourself in atmosphere longer so you can drag your apoapsis down.

If you're in a roughly circular LKO, you can enter very gradually/gently with a high periapsis, and keep angled nose-up so that lift helps you stay at high altitude while slowing down. By the time you descend into the crispy-critter zone (35km and below), you're already slowed down to 1500ish m/s and the remainder of the entry isn't too bad.

[RoboRay]

6km Pe is not "just gently dipping into the atmosphere"... it's fairly steep, but survivable (depending on the craft design). I normally set Pe to about 20km with planes (since I can pitch to a high Angle of Attack and slow down quickly) and 30km for ballistic reentry pods.

[DancesWithSquirrels]

I set my periapsis to 35-38km for ballistic pods - with that reentry path even a Mk1 has no problem without a heat shield.

6km is coming in really hot.

[Vegetal]

I don't know what you people are saying, my entry periapsis for spaceplanes is below ground, and close to 100% success rate.

You shouldn't be getting that with a 6km Pe, are you sure it's the heat that is killing your parts? If you lost solar panels or other low-tolerance parts, that would make sense, but landing gear and wing strakes usually take a lot of heat before blowing up.

[InterCity]

Thanks for all the help, guys. I was aiming for 6km to get some decent precision before landing, but I guess safety comes first. I'll just skim the atmosphere and fix the trajectory when already there.

[Val]

I don't do targeted re-entry with spaceplanes, unless I'm close to a 80 km circularized orbit. I use aero-capture/braking and burns as needed to get into such an orbit first.

And then I follow these steps:

1. 80 km orbit. In Map mode, focus Kerbin and turn camera so KSC is facing towards you right above the Navball.
   
2. Time warp until your spaceplane is right behind Kerbin.
   
3. Put a maneuver node right where you orbit appears from behind Kerbin on the left side.
   
4. Pull the retrograde marker until the planned orbit intersects the surface through KSC.
   
   

Perform the maneuver.
Turn Prograde and time warp till you enter atmosphere.
Keep nose 20-40 degrees above horizon until your speed is around 1400 m/s. (Angle will depend on wing area and mass)
Nose down 0-5 degrees below horizon.
You should be nearing the coast of the landmass where KSC is at 25-30 km altitude.
Aim to pass the mountains at 10 km, at 650-750 m/s.
Nose down further, if needed, and aim for a point about half a runway length in front of the runway.
When below 1000 m, try to slow down to around 150% of your touchdown speed.
At 200 m, pull-up and aim for the runway.
Touch down.

[InterCity]

Okay guys, thanks to you I've finally made it. The gauges didn't even show up...

... But surely enough, I ended up right in the middle of an ocean.

With heroic effort and the nerves of touching down at 41 m/s (at which point the orbiter was nearly uncontrollable), I managed to walk away from the landing...

... Only to be attacked by Kraken when trying to get a daylight shot.

Thank you guys, without you, Kraken wouldn't have dinner today.

Edited August 28, 2015 by InterCity