Reusable Craft with Deadly Reentry

[Sauron]

Does anyone have any tips? I'm trying to build a fully reusable rocket SSTO architecture for Kerbin/Laythe (and by extension everywhere except Tylo and Eve). I'm running into some problems though:

-Since it has to be multi-use I can't use ablative heat shields (which will wear out) or the baloon (which is one-time-use for landers), and reentering using the engine as a heat shield is dicey for Kerbin.

-How do you shield landing legs effectively?

-Anything I should know?

[TechnicalK3rbal]

Why is the balloon only one time use? Just mount the engines radially instead if decoupling it.

[Sauron]

But then the engines are outside the shield, no? Also, there's some ground clearance and placement issues with landing gear too, I imagine.

[CreepyD]

From my experience a heat shield projects a cone behind it.

For example using a 1.25m shield it protects a 2.5m payload behind it, and even a couple of RCS thrusters radially attached to that placed towards the rear.

Experiment a bit re-entering Kerbin.

[Taki117]

This might give you some ideas.

In it Scott Manley uses a Space Plane (That does not have an ablative heat shield) and reenters safely with deadly reentry. Also, Engines are perfectly good heat shields. Because they are designed to withstand exhaust temperatures they can withstand extremely high heat. Just make sure your reentry is shallow and you are fine.

[Bobnova]

Gentle aerobraking is key, don't dive in.

Ideally your aerobrake will take a long time and end at least a third of the world from where it started. I like to aim for half. If you do it right you don't even need heatshields.

[Sauron]

Issues:

-Recoverable SSTO is worthless without precision landings. Very shallow reentry profiles make this quite hard to do. (I need to land at KSC or at a handful of bases on Laythe. And not in the ocean, obviously)

-I've been able to safely reenter on laythe with everything but the landing legs intact--I can't fiddle with it enough to make sure they're shielded properly.

[vetrox]

Could u not take some heat shields with docking ports attaches and use kas to attach the new one after landing? Or if u dont want more mods u could build a contraption that has a bunch of heatshields on it that your ssto can just drive up to? Launch a couple to laythe and leave some by the runway on kerbin

Edited February 19, 2014 by vetrox

[rhoark]

Also, Engines are perfectly good heat shields. Because they are designed to withstand exhaust temperatures they can withstand extremely high heat. Just make sure your reentry is shallow and you are fine.

It works if you don't care for verisimilitude. Engines' heat tolerance comes from at least one of three things:

1. Ablative coatings that are meant to be blasted out, not rammed up the throat.

2. Curtains of moving fuel insulating the engine from the flame

3. Cold fuel piped along the outer surfaces

None of these really apply during reentry.

Gentle aerobraking is key, don't dive in.

Ideally your aerobrake will take a long time and end at least a third of the world from where it started. I like to aim for half. If you do it right you don't even need heatshields.

A very shallow entry causes too little drag, so the integral of heat over time can be larger than a steeper reentry. It takes a happy medium.

Edited February 19, 2014 by rhoark

[Sternface]

A real SSTO would need a massive maintenance overhaul after each flight. Considering there are no repair shops on Laythe, perhaps you could just be careful enough with your reentries so that you have enough shielding to return to Kerbin for 'maintenance.' Then just recover and launch it again all refurbished.

For me that would solve the role-playing element, especially if you landed back on the runway. Doesn't do much to give you a maintenance-free SSTO tho...

Sounds like you need an ablative-replacement-from-EVA mod...

P.S. You could always simulate a replaceable shield by tweaking the relevant part's configs to raise its maximum temperature or ablative quantity. Kinda hackish tho.

Edited February 20, 2014 by Sternface

[Geschosskopf]

A real SSTO would need a massive maintenance overhaul after each flight.

What he said. I mean, look at the turn-around for the Space Shuttle.

Sounds like you need an ablative-replacement-from-EVA mod...

That's a cool idea but I'm trying to figure how that could be made to work. I mean, you can code anything to make it happen by magic in a game, but how would you apply the new ablative stuff? A spraying thing would just fly off under its own thrust. Trying to roll it on would just push the Kerbal away. And it wouldn't trust zero-G brick masonry to replace Shuttle-like tiles, either, even ignoring the huge pile of replacement bricks you'd need, and a way to dispose of the used ones.

Perhaps some sort of nanotech extrusion? Between the actual structure and the heat shield, you have a thin layer that, when fed the proper components, oozes out new heat shield, like how we grow skin. And you wouldn't need to EVA to do it, just dock at a tanker containing the input chemicals for the extruder. But it might take months to extrude a sufficient thickness....

[Bobnova]

A very shallow entry causes too little drag, so the integral of heat over time can be larger than a steeper reentry. It takes a happy medium.

What I've seen is that the peak temperature is lower with a very shallow angle. Also heatshield damage/consumption seems to be lower as well. The only negative I've found so far is if you don't slow down enough and come back out of the atmosphere and are still going fast enough to escape (or have limited life support supplies and can't last till the next orbit).

I'm not sure where heat over time comes into things, being at 1000°-1200° for a couple minutes doesn't seem to do any damage, while being over the part's heat maximum even briefly destroys it.

EDIT: Please note that I'm talking purely about KSP with DE, not real life.

[Cakeofruit]

For the rentry of my orbiter i usually go for a 100km * 40 at 1/3 or 1/2 kerbin of the ksc or you can make just above it but you need to lose speed before 20km and a péri close to 35 km ( you just make a major steal at 45km for loosing speed at high altitude )ps : with FAR

[rhoark]

I'm not sure where heat over time comes into things, being at 1000°-1200° for a couple minutes doesn't seem to do any damage, while being over the part's heat maximum even briefly destroys it. EDIT: Please note that I'm talking purely about KSP with DE, not real life.

Very true. I think KSP's heat conduction is too low and dissipation too high. Both are moddable so I may get to it if someone else doesn't.