[Tutorial] Fly fast without burning up

[Xyphos]

 

 

Overheating occurs when fast moving gases are pressed down upon your vessel, as shown in image 4.

To prevent this, you need to change the shape of your nose. By adding a shielded docking port or a heat shield to the front, you can create a double-shock cone.
By creating a double-shock cone, you're able to push hot gases away from your ship, via Ablation Effect, which allows you to go fast without taking heat damage.
in the last image, the ship has attained terminal-velocity for that altitude and cannot go any faster without climbing to a higher altitude with a thinner atmosphere, but it's not taking any heat damage at all.

Edited July 17, 2016 by Xyphos

[bewing]

From my experiments, a klaw may actually work better than a shielded docking port.

[Foxster]

Or you can use something nice and pointy with a  Communotron 16 on the tip for even better performance. 

[Xyphos]

On 7/18/2016 at 2:47 AM, Foxster said:

Or you can use something nice and pointy with a  Communotron 16 on the tip for even better performance. 

actually, pointy creates a compressed shock cone, which causes overheating, and discussed in the OP as the exact opposite thing to do.
you want something that can produce the ablation effect, such as a heat shield or shielded docking port.
@bewing claims that the klaw would work too, but I've never tried it.

[Foxster]

4 minutes ago, Xyphos said:

actually, pointy creates a compressed shock cone, which causes overheating, and discussed in the OP as the exact opposite thing to do.
you want something that can produce the ablation effect, such as a heat shield or shielded docking port.
@bewing claims that the klaw would work too, but I've never tried it.

Have you tried it?

[Xyphos]

2 minutes ago, Foxster said:

Have you tried it?

I've tried all kinds of pointy objects; nosecones, tail cones, anteneas, fly-by-wire systems... all same thing; if a compressed shock cone occurs, so will overheating.
blunted objects do create more drag but deflect the hot gasses away from your ship.

[Foxster]

I've tried all kinds of stuff too and keep coming back to the aerial stuck on the front option because it overheats less and get's an SSTO to orbit on the least dV. 

[TopGull]

I'm pretty skeptical about the shock cone and ablation effect explanations for why this works to protect your ship from atmospheric heating.  It looks like you're using the stock aero model (I don't see FAR among your tabs, sorry if I missed it).  As far as I know, KSP's aero model isn't sophisticated enough for all that and the "shock" effects you see are purely visual.  I do have an alternative explanation though.  Check out the maximum temperatures for the Mk2 Cockpit, the Communotron 16, the Klaw, and the Shielded Docking Port:

Part	Max Skin Temp	Max Int Temp
Mk2 Cockpit	2500 K	1400 K
Communotron 16	2000 K	2000 K
Advanced Grabbing Unit	2000 K	2000 K
Shielded Docking Port	2600 K	2600 K

The obvious weak point is the low max internal temperature of the Mk2 Cockpit.  I suspect that in your first test, the internal temperature built up enough to exceed that limit.  The Shielded Docking Port, on the other hand, has a higher max skin temperature and a much higher max internal temperature.  I think that's the real reason the second craft doesn't explode.  I don't have KER installed right now so I can't be certain about this, but it looks like you do.  You could run this test again and watch the critical temp readout to see the actual temperatures of both parts.

[bewing]

1 hour ago, TopGull said:

 

I'm pretty skeptical about the shock cone and ablation effect explanations for why this works

 

Yeah, well. They aren't exactly right. On another thread, a squad guy (it might have been Claw?) said specifically that the aero effect he had added was the "detached shockwave" effect. When a sharp object travels fast the resulting plasma is created right on the skin of the vehicle, and conducts plenty of heat directly to the skin. When it's a blunt object going fast, the plasma is formed a small distance out in front of the skin, and never touches the skin. So you only get radiative heating from the plasma, which is a lot less.

The antenna trick works because there is only a tiny pinpoint area absorbing heat directly from the plasma, so the antenna does not absorb a lot. So it does not conduct much to the rest of the craft. But in a more sophisticated model, the tip of the antenna would melt.
 

Edited July 20, 2016 by bewing

[TopGull]

Hmm, I guess I missed that thread, but I ran some experiments with different nose parts and I've convinced myself that you must be right. The shape of the leading edge seems to have a big effect on the amount of convective flux, leading to skin overheating.  Case in point, I tried using the 1.25 m fairing to make a pointy nose and a flat nose, and the pointy one exploded while the flat one was fine.  It also seems like this effect is very sensitive to the exact shape of the nose. The short blue nose cone isn't much sharper than the shielded docking port, but it generated a lot more heat under the same conditions.

I also noticed a very strange effect when I tried using the FL-A10 adapter as a nose cone. There were two very distinct heating modes that seemed to be triggered by a combination of speed and altitude: one where little heat was generated, as if it was a blunt object; and one where an insane amount of heat was generated, enough to raise the skin temperature from barely overheating to well over the max in a fraction of a second. At 1000m altitude, it would flip suddenly into the high-heating mode at around 1370-1380 m/s. Any ideas why this might happen? Some quirk of the part geometry, maybe?