Atmospheric entry with odd shapes

[Hell_Raiser]

I have no problems preventing round pods from overheating on entry, however, every time I try to bring a space plane or rover into an atmosphere it goes Ka-Boom.  I have tried enclosing them in fairings (rovers) and air-brakes/shallower angles (space planes) but they still tend to blow up.  I can barely get a plane down from LKO, but I am red lining the cockpit.  With fairings the fairing survives entry, and usually survives impact with the ground, but everything inside blows up.

 

Is there some trick to this I am missing or do things just like blowing up without heat shields?

[Temstar]

With spaceplanes it's actually safer to reenter at steeper angle than it is to try to reenter at shallow angle. The reason for this is you accumulate a lot of heat plowing through the upper atmosphere while hardly slowing down at all. When you reenter at shallow angle you spend a long time in this region and by the time when you actually reach dense enough atmosphere for some serious braking you are ready near max heat capacity.

Reentry at steeper angle means you quickly punch through the upper atmosphere and end up with plenty of heat capacity left when you reach the deceleration zone.

In either case, reentry with very large AoA will help. Large AoA decreases your ballistic coefficient and spreads the heat load over a larger area instead of focusing it all at the leading edge and nose. Powerful aerodynamic forces will try to pull your plane prograde when you reach denser air, I leave my RCS system on during reenty to fight against the aerodynamic forces to keep large AoA for as long as possible.

[moogoob]

8 hours ago, Temstar said:

With spaceplanes it's actually safer to reenter at steeper angle than it is to try to reenter at shallow angle. The reason for this is you accumulate a lot of heat plowing through the upper atmosphere while hardly slowing down at all. When you reenter at shallow angle you spend a long time in this region and by the time when you actually reach dense enough atmosphere for some serious braking you are ready near max heat capacity.

Reentry at steeper angle means you quickly punch through the upper atmosphere and end up with plenty of heat capacity left when you reach the deceleration zone.

In either case, reentry with very large AoA will help. Large AoA decreases your ballistic coefficient and spreads the heat load over a larger area instead of focusing it all at the leading edge and nose. Powerful aerodynamic forces will try to pull your plane prograde when you reach denser air, I leave my RCS system on during reenty to fight against the aerodynamic forces to keep large AoA for as long as possible.

I suppose the reason you can do this on a spaceplane and not a capsule is that the spaceplane, when pancaked, has much greater drag, correct?

[Temstar]

Well capsule falling heat shield side first is already correctly orientated for maximum drag, so not much you can do there.

You can however change the shape of the capsule at design time to change its drag profile, for sample:

This hilarious shaped capsule is part of the Japanese Fuji spacecraft design. The reason why it looks like an Apollo capsule that's been run over is because Fuji was designed with space tourism in mind. And since your average space tourist cannot tolerate as many G as astronauts who were basically selected because they were superman the capsule was designed to be extra draggy so it loses more speed higher up and experiences lower peak acceleration in the lower atmosphere.

[Gojira1000]

Attitude during re-entry counts for a whole lot in survivability with a spaceplane. Here's a Mk1 I flew last night, all stock, not even airbrakes on it. While it does get a tiny bit red, it's never in danger of overheating and going *boom*. https://www.youtube.com/watch?v=K3cEyray7Yc

[NathanKell]

There's actually two approaches to spaceplane reentry, and both work. One is the one @Temstar outlined above: minimize your time in the high atmosphere and make your BC as low as possible with  a high-alpha reentry. It has no particular L/D requirements and can be done with high wing loading. That's what all real life spaceplanes have been designed to do. The second approach is the one originally envisioned for spaceplanes: very low wing loading, high L/D. You keep your descent rate low enough that you radiate heat as fast as you take it in, and only descend below, say, 45km once you're quite slow (in relative terms). This approach requires you to keep your L/D fairly high and to not have too high an angle of attack (for fear of lowering your periapsis too far).

 

As to the Fuji: It's flat like that more because you get a much high L/D ratio, and they wanted to fly a (comparatively) high-lift descent, which lowers the G forces. A ballistic (zero lift) reentry is always going to have the same peak G no matter the ballistic coefficient, IIRC; what changes the peak G is the entry angle, and/or lift.

[AeroGav]

Not edited as nicely as the above post, but here's my re-entry, 

 

1. landing gear down and cargo bay doors open, for more drag, slows down faster (apparently rubber tyres are more heat resistant than thermally hardened spacecraft parts)

2. pitch up to 20-25 degrees above prograde.  Max lift is at 30, but it falls off quickly past that point and given how hard it is to hold an exact pitch angle, i usually shoot for 20 or so.    The lift keeps you out of the thick atmo till you're really slowed down.

My plane got to 752/1400K on the cockpit, having so much wing helps with 2).

Also, I think i just won the spot landing competition.   That's a seriously slow touchdown speed my plane has.