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Brownhair2

Keeping SSTOs Cool

Question

Don't have a specific design for this, this is just a general question. How do you keep SSTOs from exploding during re-entry? I've tried radiators, but they don't seem to help

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Don't do suicide reentrys. Low orbit into shallow dive and once in atmosphere, nose up as much as you can. You go prograde - you burn(usually).

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Point your nose 90 degrees up, and make sure you don't come in too timidly. You want to get yourself below 45km ASAP. Further up than that, you don't get any worthwhile slowing effect, but you still get lots of heat, and that adds up over time until all your parts run out of heat capacity. Since a spaceplane does not carry ablator, you only have a couple of minutes survival time under high heat load, so you want to make it count for slowing down.

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First off, technique - come in conservatively with a higher apoapsis if you're having trouble.   So long as the AP is below 70km and the PE is within Kerbin's SOI, you'll come down eventually.   Also don't go in prograde like in a capsule - pitch up a bit.   I go for about 20 deg pitch to maximise lift and keep out of the thicker atmosphere as long as possible.  Some say pitch up into a stall or spin deliberately.

20160708202324_1_zpsyejtmwp6.jpg

low tech career mode spaceplane coming in from 300km orbit.

Finally, lowering landing gear and opening cargo bays can help, by increasing drag.

 

Design

1. more wing area = more lift = not dropping down till slower, so less rapid rate of heating

2. inline cockpits rule.    That way the nose cone takes the brunt of the heat.      They are also more crashworthy 

3.  In a spaceplane with lots of lift, the limiting factor can be prolonged heat buildup in the core of the cockpit part over the course of multiple skips off the atmosphere , rather than skin temperature from rapid peak instantaneous heating.  What you can do is put retractable radiator panels inside a service bay.   They don't appear to work below 70km but each time you skip off back into space you can open the service bay and deploy the radiator to get rid of heat that built up on the last dip in the atmosphere.  That way on the final re-entry you're not coming in with a cockpit that's already been heat soaked to 55% max temperature before you even encounter the atmo.

4. put an antenna on the nose cone to effectively move the cockpit further back.

5. as an insurance policy, you can use a low melting point nose cone (like the 2000k type A part) , and put a heat shield between it and the rest of the fuselage.   In normal service, the heat shield is not consumed and makes no drag, but if things go wrong, it will save the rest of the airplane at the cost of a nose cone.

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But how about keeping the cockpit cool? My latest SSTO has suddenly got a bad case of explodes-during-ascent

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If you are using mk1 cockpit, I had problems with that too. My solution is using inline cockpits. They make it much easier to survive re-entry.

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Sticking a blunt object at the front of the craft will create a detached shockwave which will keep the heat off the craft.  If said blunt object has high heat tolerance (like the shielded docking port), your craft can survive very high speeds in low atmosphere.  Of course the trade off is that you have a poor aerodynamic form, which means you will have to fight a lot of drag and lose out on a lot of SSTO efficiency, but the upside is that you can reach faster speeds with exploding.  Good for designs have a lot of engine power and no critical need for efficiency.

QHa5tqXR.jpg

Edited by Edax

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1 hour ago, Edax said:

Sticking a blunt object at the front of the craft will create a detached shockwave which will keep the heat off the craft.

But does it happen in KSP?

Anyway, do radiators at least help?

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Well, managed to get my latest SSTO to orbit. Honestly not sure what helped, but thanks everyone :D

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5 minutes ago, Brownhair2 said:

Well, managed to get my latest SSTO to orbit. Honestly not sure what helped, but thanks everyone :D

Blunt objects help as the guy above you said. I was blowing up in re-entry countless times before I started using inline cockpits.

 

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8 hours ago, Edax said:

Sticking a blunt object at the front of the craft will create a detached shockwave which will keep the heat off the craft.  If said blunt object has high heat tolerance (like the shielded docking port), your craft can survive very high speeds in low atmosphere.  Of course the trade off is that you have a poor aerodynamic form, which means you will have to fight a lot of drag and lose out on a lot of SSTO efficiency, but the upside is that you can reach faster speeds with exploding.  Good for designs have a lot of engine power and no critical need for efficiency.

QHa5tqXR.jpg

Have the best of both worlds and put a nose cone on a stack separator.  That way you benefit from low drag on ascent and high drag on the way down.  Or just use a nose cone with a low melting point like the type A (2000k) - incidentally this is also the lowest drag part available.

Not technically SSTO but come on,  would you rather a spaceplane that can go to Minmus but has to replace its nosecone every flight or one that barely makes low orbit because it used all it's fuel fighting drag,  or used it's payload fraction on extra engines to overcome the drag?

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Well, I prefer putting a klaw on my nose. It gives all the benefits of a blunt nose, it's light, it allows you to dock with anything, and it costs a lot less science than a shielded docking port. Then I usually launch my TSTO vertically, on a recoverable booster. That way, I avoid most of the aerodynamic drag on the way up.

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21 hours ago, Brownhair2 said:

But does it happen in KSP?

Anyway, do radiators at least help?

Yeah they do, also on the way up, but keep in mind the fixed radiators only cool parts that are up to two connections away. I need them for the way up too because apparently standard procedure is to inflate rovemax M1s with lighter fluid and they keep exploding in the bay. At worst it'll give you a little more margin during reentrance

iYhx2jql.png

Thebest advice I've read in this thread is to get into thicker parts of the atmosphere as soon as you and going in pancake (close to or at 90 degrees for as long as you can hold that pitch).

zzQCRial.jpg

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I reenter Mk1 craft at 15-18 deg from a low orbit with a 20km Pe, haven't burned one up yet - that's without tricks like nose-antennae. Airbrakes help.

Bigger craft have higher heat tolerance & I just set them at 12 deg & ignore them.

Edited by Van Disaster

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