Spaceplane ascent overheating

[Nothalogh]

So I was building a pretty standard Rapier powered Mk2 passenger SSTO.

I flew a pretty conservative ascent profile:

30 deg supersonic climbout to 10km

15 deg run for max airbreathing velocity at 19km

As soon as I passed 1500ms at around 22km, I got a red heat bar on my cockpit and it then vaporized.

 

Has hypersonic aero changed that drastically in 1.0.5?

Edited December 1, 2015 by Nothalogh

[JTpopcorn]

Yup.

1.05 did some funky things to aero, such as causing upper atmo to be very thin, and lower atmo to be more dense.  This causes a "wall" in which while still at orbital speeds crafts hit low atmo and overheat, or are unable to slow quick enough to open chutes.  If possible, I would suggest geting rapiers to supersonic at low pitch, then going up relativly steeply to skip the dense atmo, and level off close to the top of low atmo.(on the density bar)  You shouldn't have to much trouble with heat if you get high enough in the atmosphere, but at a certain point heating will go through the roof, and you will need to get above that altitude as quickly as possible.  A steeper climb should cause heat to be less of an issue but will hurt efficiency.

-JT

[Nothalogh]

See, that's the thing, I'm only mildly supersonic up until 10km, only then do I pitch down for my airbreathing run, which worked flawlessly, I had 1400m/s as I cleared 19km in a 15 deg climb.

It all looked good, power was dropping on the Rapiers, so I closed the intakes and went closed cycle, pitched up to 20 deg and started gaining velocity and apoapsis.

And that's where it all went to hell, somewhere around 1600 to 1700 m/s, at around 22 or 23 km.

[Val]

Use a Shielded Docking Port as nosecone and you should be fine up to 1600 m/s below 22km and orbital speeds higher up in the atmosphere 

[Venusgate]

You might need a steeper final climb out of the atmosphere. 

My understanding is the atmo was redistributed more evenly, so the lower 10km is thinner (and won't auto catch anything that falls straight down) and the upper 30km actually has air in it

[Nothalogh]

So, theoretically my engines can breathe above 20km?

Neat

[cephalo]

I try to get to about 26k before switching to rocket mode. At that point I''m going about 1400 ms.

[rocketbuilder]

Firstly, your spacecraft needs to be higher in altitude like everyone said and in 1.05 reentry heating was turned up massively. 70% reentry heat is like 1.04 now, but 85% is kinda fun. With 85% it's possible to aerobrake at other planets, even Jool, but the spacecraft needs to be completely shielded by heat shields.

[AeroGav]

You could try changing your ascent profile.   Even RAPIER engines start loosing thrust above 1215 m/s,  so I'm not sure what the advantage is in exceeding that.  Accelerate to 1215 above 20km then maintain constant airspeed and use excess power to climb.   You might want to resize your wings for the higher, slower profile - in stock aerodynamics, best lift-drag ratio occurs at 2 degrees angle of attack subsonic, rising to 5 degrees at 2200 m/sec.   With Ferram Aerospace mod, it'll be more like 10 AoA at mach 3.7.      If you're finding the angle of attack needed to maintain level flight at those speeds and altitudes is higher than that needed for best lift/drag, you need more wing.  If lower, you need less.

[NathanKell]

Interestingly, reentry heating was actually not turned up. What changed was skin->internal conduction, which got turned down, which means you can't soak heat like you used to.

[Nothalogh]

11 hours ago, AeroGav said:

You could try changing your ascent profile.   Even RAPIER engines start loosing thrust above 1215 m/s,  so I'm not sure what the advantage is in exceeding that.  Accelerate to 1215 above 20km then maintain constant airspeed and use excess power to climb.   You might want to resize your wings for the higher, slower profile - in stock aerodynamics, best lift-drag ratio occurs at 2 degrees angle of attack subsonic, rising to 5 degrees at 2200 m/sec.   With Ferram Aerospace mod, it'll be more like 10 AoA at mach 3.7.      If you're finding the angle of attack needed to maintain level flight at those speeds and altitudes is higher than that needed for best lift/drag, you need more wing.  If lower, you need less.

That is my plan.

I just wasn't aware that we had engine usable atmo above 20km, post 1.0.5

[Nothalogh]

Great success.

 

At 10km I pitch down to 15deg to begin high speed run

As soon as I reach 1000m/s I pitch up to 20deg, and ride that until power loss at 1400m/s and 24km

Engage the rockets, pitch up to 25 deg, and push my apoapsis to 54km

Cut throttle and coast to above 50km

Then make several short burns to raise periapsis, push apoapsis clear of atmo, and insert into low orbit.

 

Honestly, I like it.

[AeroGav]

59 minutes ago, Nothalogh said:

That is my plan.

I just wasn't aware that we had engine usable atmo above 20km, post 1.0.5

Pretty sure i've had RAPIER craft able to maintain 1215 m/s and a slow climb up to 26km, post patch.  The fuel use falls off with thrust, so it was worth hanging on to.  That particular aircraft didnt carry any oxidiser, so at that stage i started up the NERV and left the RAPIER going till it quit at 29.5km.  Useable lift is there till 40km with stock Aero.

[Wanderfound]

Slightly cheesy design hack: radiators. Stick a small one somewhere in the vicinity of your overheating part and your exploding problems will go away.

This 'un has one of the small curved radiators on top of each of the long lateral tanks, protecting the normally vulnerable 747-style wings (BTW, did your Mk2 plane have a Mk1 cockpit? The one-seaters are a bit explody; low heat tolerance).

 

Feel free to now have a lengthy argument over the realism or otherwise of this working.

Edited December 3, 2015 by Wanderfound

[gilflo]

For SSTO, problem is the climb, you can find how to pass quickly between 20 and 28km were you get the most heating....

The problem is re entry, and how to slow speed enough between 40 and 20km so that you will not overheat. Even with 2 tons of radiators, i did not manage that....

and i don't see any tiles or any shield to protect the skin of a SSTO, because every part is exposed to heat.....

[Wanderfound]

1 hour ago, gilflo said:

The problem is re entry, and how to slow speed enough between 40 and 20km so that you will not overheat. Even with 2 tons of radiators, i did not manage that....

and i don't see any tiles or any shield to protect the skin of a SSTO, because every part is exposed to heat.....

Pitch up to about a 45° angle of attack as soon as you touch atmosphere, and keep it there until you've achieved level flight. Then gradually lower the nose, basing the speed of your descent on the temperature of your hottest bits.

Airbrakes make the process much easier, but they aren't necessary.

[gilflo]

Yes, that's what I am trying, but sooner or later it ends in spin. I guess it's easier with small SSTO.

[Wanderfound]

If you're spinning, shift weight forwards. Pump some of the fuel in the rear tanks to the forward tanks before reentry. Beefing up your tailfin would help as well.

If all else fails, a Vernor each side of the nose can work wonders.