How do you Manage Heat in an SSTO?

[Dogface]

In order to escape gravity I am trying to get up speed, about 1000-1400m/s. But somewhere in that speed range my SSTO nose starts to heat up and eventually something explodes. I can keep the speed down, but then I dont get near an Ap of 70km.

My nose is made up of air intakes, for obvious reasons. Do I need a heat shield for an SSTO noce?

Edited May 20, 2015 by Dogface

[Goomblah]

Once you start accelerating wildly after breaking Mach 1 (340 m/s), you need to begin slowly pulling up so your prograde is at about 30 degrees by the time you hit Mach 3. Pulling up too fast will cost you velocity, and not getting to a safe altitude fast enough will make you overheat and explode at such high speeds. I usually break the sound barrier at an altitude near 15km, then pull up so I hit 1200m/s or so at 25km, switching over to rocket propulsion shortly after, as the air thins out.

The main issue is making sure you get out of the lower atmosphere before drag from hypersonic flight pulls your spaceplane apart.

[Dogface]

Thanks, I will try that. That is sort of what I am doing, but obviously not getting it just right. SSTOs are far more complicated than a rocket launch. And more aggravating.

[moronwrocket]

I do 15* from 10ish km up to switching to rockets. Switch over as soon as your surface speed peaks and starts dropping.

[ajburges]

Old aero the challenge was climbing while accelerating.

New aero the challenge is to not blow up before leaving the lower atmosphere with all the speed you can. Then have enough anaerobic dV to reach orbit.

It is hard to survive maxing out the aerobic velocity of a space plane SSTO because you want as much acceleration in high Mach as possible for a better final aerobic speed. (balanced against the alternative of more fuel mass to get that speed in anaerobic mode) Optimal ascent should see you redline before temperatures drop as you climb out of the atmosphere. The relevant variables are many more than old aero.

Edited May 20, 2015 by ajburges

[Mastikator]

Ram Air intake has the highest heat resistance, only use that, no Shock Intakes or anything.

Go up about 7km, reach about mach 1.5, start a slow incline, maybe 10 degrees, make sure your incline does not reduce your acceleration too much.

When you reach mach 2 tip higher at about 20-30 degrees, it will start to overheat but once you reach 25km up the air resistance will be low enough for you to stop heating up. Switch over to oxidizer when the air intakes run out. When you reach 70km+ apo wait until you get close and circularize.

[Dogface]

Thanks guys. I find SSTOs very frustrating. I have gone to all the planets, moons, put up two space stations, brought Kerbals back from Duna, flown two SSTOs in previous versions. But I cant seem to get a version1.0 SSTO into a circularized orbit.

And making it worse is that I cannot tell if it is my flight plan or my design, or probably both.

[ajburges]

Thanks guys. I find SSTOs very frustrating. I have gone to all the planets, moons, put up two space stations, brought Kerbals back from Duna, flown two SSTOs in previous versions. But I cant seem to get a version1.0 SSTO into a circularized orbit.

And making it worse is that I cannot tell if it is my flight plan or my design, or probably both.

For design, once you figure out aerodynamic stability and control (CoL, wet mass, and control surfaces), the issues are lift, drag, aerobic thrust, and anaerobic dV.

You want only enough lift for a stable glide path for landing. This may allow you to take off before the runway's end, but too little lift can increase your drag when you have to maintain to high an AoA for lift.

Drag saps your dV and increases your thrust requirements. It has uses in reentry, but there are plenty of ways of dealing with that without flying a piece of Styrofoam. Use utility/cargo bays and only attach radially what you need. (gear, wings, ladders, and engine nacelles) Use as few of the largest wrong pieces you can for your lift.

Aerobic thrust is your enabler. Jet dV is cheap in every sense. You want enough thrust to go fast before you run out of air or blow up. Too much though is wasted mass.

Anaerobic dV is how you go from airplane to space plane. 1.8 Km/s vacuum should get you to an 80x80 orbit from 1 Km/s @ 18 Km. You still want a respectable thrust here, but it is a more relaxed requirement.

[Dogface]

Thanks guys. I finally got an SSTO into a circularized orbit. The game crashed, so I will see later if it can reenter. I get a lot more crashes with v1.

One thing I did was uninstall and reinstall. I think that helped a bit. Also installed four more engines.

[cephalo]

Thanks guys. I finally got an SSTO into a circularized orbit. The game crashed, so I will see later if it can reenter. I get a lot more crashes with v1.

One thing I did was uninstall and reinstall. I think that helped a bit. Also installed four more engines.

Disable the heat gauges with the F10 key. They have memory leaks and will crash your game when parts heat up.

[ajburges]

Disable the heat gauges with the F10 key. They have memory leaks and will crash your game when parts heat up.

Unfortunately, you really need those while debugging heat management.

If you are suffering from crashes, do disable those once you debug reentry (and restart KSP)

[NathanKell]

Ram Air intake has the highest heat resistance, only use that, no Shock Intakes or anything.

Uh...that's totally false. Shock intakes are much more survivable in terms of heat--indeed, if you look in the cfg, you'll see they literally have a multiplier of 0.5 to their convection flux.

[Orbital Vagabond]

Uh...that's totally false. Shock intakes are much more survivable in terms of heat--indeed, if you look in the cfg, you'll see they literally have a multiplier of 0.5 to their convection flux.

Uh, any chance you could explain the significance of that value for us lesser minds?

[Murph]

Uh, any chance you could explain the significance of that value for us lesser minds?

Heating from convection (which is most of your incoming heat during re-entry) only hits the shock intakes half as hard.

[Dogface]

Disable the heat gauges with the F10 key. They have memory leaks and will crash your game when parts heat up.

Thank you. I turn it off and havent had a crash yet. My crashes were happening after an ascent, so it makes sense that temp may have been playing a role.

I also managed to get my SSTO back to Kerbin without exploding any parts. I mostly just dropped the Pe to 50km and aimed prograde, I opened my airbrakes (10) and burned RCS thrusters backwards (not sure that did much, but it gave me something to do). So it is a proven SSTO. I seem to have experienced less heat on the reentry than I did on the ascent.

Thank you all very much for your advice.

If you are having SSTO problems and looking for design hints, I used a heavily modified version of this ship...

Edited May 28, 2015 by Dogface