Cobra reentry with a spaceplane OP

[SelectHalfling0]

I mean it's not exactly the same, but that is how the shuttle slowed down so rapidly...

I do agree there needs to be more aero stress though.

[sal_vager]

This looks pretty legit to me, you're presenting a very blunt and draggy craft to the airflow by having your nose up that far, I'm told the space shuttle re-entered at around 40° AoA as well, which is pretty steep.

You'll lose speed quickly, so your craft will be exposed to compression heating for less time and those heat gauges only show up when you're over about 90% of the parts heat tolerance.

I used to think I had to re-enter high and level too, so the craft would have a gentler time of things but that compression heating, even in the high atmosphere, adds up over time.

Probably the only unrealistic thing here is the absence of any consequences from the high-G's experienced with a more rapid re-entry.

[Korizan]

Two things.

1 - Heat, right now all kinds of things make it back to kerban that shouldn't, most things should be burning up in the atmosphere.

2 - The new aerodynamics are not necessarily wrong, resistance translates to heat. Making the atmo thinner doesn't make it correct.

What will happen when you drop something into an atmos at high speeds.

Well it will rip it apart, and then burn it up.

Something not very easy to simulate when you give people the freedom to build just about anything.

How do you decide what gets ripped apart and what doesn't.

Things can get rather ugly real fast, think 1.0 on steroids.

[Goomblah]

I do this for all my spaceplane re-entries, as well as with landers and rockets. It can make the difference between a toasty but manageable descent and a complete failure.

The Flying Slab (link below) was able to decelerate using this method on a suborbital trajectory at altitudes as high as 65km. By the time it reached the thicker atmosphere at 25km it was only moving at 1600m/s; it barely got hot at all.

http://forum.kerbalspaceprogram.com/threads/33312-Showcase-SSTO-s%21-Post-your-pictures-here?p=1952607&viewfull=1#post1952607

In real life, it almost certainly would have been torn apart by atmospheric stresses (and it blew up in-game, too, but for different reasons)

[rtxoff]

I think in real life the more speed you are bleeding off per second the more heat is produced and the more stress your structure is exposed to. Right now in KSP it seems that reentry heat depends only on your actual speed and atmosphere density but your actual deceleration is not accounted for heat production. I could be wrong however.

[Red Iron Crown]

I think in real life the more speed you are bleeding off per second the more heat is produced and the more stress your structure is exposed to. Right now in KSP it seems that reentry heat depends only on your actual speed and atmosphere density but your actual deceleration is not accounted for heat production. I could be wrong however.

I think you're mistaken there. Deceleration rate has nothing to do with it, it's all about the speed at which you're passing through the atmo.

The reason there's not much heating with this approach (or reentry in general) is because of Kerbin's very low orbital velocity (a consequence of its tiny size). The heat and aero system are reasonably realistic, there's just not that much speed to scrub away. It's a difficult balancing act: Turn up the heating to make reentry dangerous and spaceplanes burn up during ascent, turn it down and reentry is just not dangerous unless you're doing it directly from a high orbit.

[Korizan]

You can't really can't compare earth orbit speeds of ~7,800 m/s to Kerban's ~2.500 m/s It is just apple and oranges.

One of the biggest problems is just using real world formula's for something that just won't exist.

It doesn't work the math will always be off.

If you did use real numbers you could have a valid argument that there is too much heat in the current system.

But what would be the fun in that.

No matter either way it should be interesting to see what the squad does in 1.0.3 and we will just have to adapt from there

[MatterBeam]

What happens to re-entry if we took the drag slider in the Physics tab of the Alt+F12 menu and reduce it to 1/3?

I imagine the re-entry would be much longer, extend to lower atmospheres, nerf the high-altitude cobra-turn/AIRBRAKE parking-brake maneouvers and increase the duration of heating.

Is this workable?

[sephirotic]

Flying for 2 minutes at mach 3: Your cabin explodes by overheating:

Reenter with a SSTO on a 60% AoA on an eccentric 400x10km orbit: Nothing happens.

Yeah, Heating needs serious rebalance.

[Red Iron Crown]

Flying for 2 minutes at mach 3: Your cabin explodes by overheating:

Reenter with a SSTO on a 60% AoA on an eccentric 400x10km orbit: Nothing happens.

Yeah, Heating needs serious rebalance.

Such statements are meaningless without quoting altitudes, and you are defining exactly what the problem is: Increase atmospheric heating to make reentry difficult and you make hypersonic flight nearly impossible; decrease it for high speed flight and reentry becomes trivial. It's not like separate mechanics are being used for them, change one and you automatically change the other.

The source of the disconnect is Kerbin's low orbital speed, if it was remotely close to the ~8km/s of Earth then reentry would suddenly become dangerous without making high speed flight impossible.

[Tw1]

It's a difficult balancing act: Turn up the heating to make reentry dangerous and spaceplanes burn up during ascent, turn it down and reentry is just not dangerous unless you're doing it directly from a high orbit.

I wonder if an awful hacky way to make this work would be to have more heat per speed for objects coming down from space, vs objects coming up from kerbin. Probably would be bad...

[sgt_flyer]

Personally, i find that drag is currently completely insane for non streamlined objects (well, that might be because contrary to FAR, stock aero model doesn't occlude anything that is not behind nosecones or stuffed inside fairings / cargo bays). (I have a roughly 23 tons replica that has really high drag because of the wings making off the shape) - it can't get faster than 42m/s of horizontal speed at sea level - with a TWR Slightly above 1 (can't even climb to vertical because of drag)

Looks like the various terminal velocities are currently wayy too low. (Heck, you can almost land safely with only A.I.R.B.R.A.K.E.S....)

Edited May 25, 2015 by sgt_flyer

[Jouni]

Looks like the various terminal velocities are currently wayy too low. (Heck, you can almost land safely with only A.I.R.B.R.A.K.E.S....)

The problem is with drag coefficients, which are too high for streamlined shapes.

There are also some issues that arise from a combination of powerful reaction wheels, a very forgiving stall implementation, and the high impact tolerance of many parts. The fact that you can land safely with a Mk2 cockpit isn't as strange as it sounds, once you take these into account. There's a lot of surface area and only a little mass.