Cockpit burns up during reentry

[Human Person]

It happened to Scott Manly and it happened to me a lot: The mk1 and mk2 cockpits burn up during reentry. Nothing seems to help. Maybe you can help by analyzing Scotts accident. It happened at 7:20 

 

[Blaarkies]

Cockpits at the front like to heat up. Have them behind something for heat occlusion, or put them inside a fairing/cargo bay.

Personally i like building MK3 size drop ships, enough to land a 2.5m ISRU anywhere on Kerbin/Laythe. So the MK3 cargo-tail is excellent...for the front of the ship!

[evileye.x]

Scott in this video could not maintain high angle of attack. Also Mk-1 cockpit is not very space plane -ish, rather for airplanes.

Edited March 22, 2017 by evileye.x

[bewing]

The mk2 cockpits should not burn up. They have a lot of drag, and a high temperature resistance.

You need to make sure to 1) keep the nose up (preferably at 90 degrees to prograde), 2) don't reenter with too much mass, 3) don't reenter from a really high orbit all at once, and 4) if you have the time to spare, do a gentle reentry with a very high Pe (above 60km).

 

[Urses]

If i See that i catch to fast on heat i try to go normal/antinormal to Stay in the Altitude and bring my belly in the Wind.

If it is not enough "uncontrolled" spin. My planes are mosty chubby and compact mainstake and big sleack wings, so they (mostly) never breack.

For M1 Edge radiators on Cockpit ofsetted on the wings or tailsection.

M2 Same but Big radiators can be used. But i mostly have only problems with tanks behind cargobays. Maybe a clipping problem? But Cockpit hmm didn't meet the Prob. 

 

[AeroGav]

I'm not sure what's going on with Scott, either he's out of practice making and flying aircraft or he's deliberately creating mishaps for drama purposes.  He used to be a really good pilot  !

The launch profile on his first flight was obviously terrible (trying to go supersonic in a steep climb, when that didn't work, started his rocket engines early, then runs out of fuel) , now this disaster.

Inline cockpits FTW.     Mk1 inline cockpit is less prone to overheating than a mk3 cockpit, because you can put it a few modules back from the bow shock, away from the heat.

[Human Person]

3 hours ago, bewing said:

keep the nose up (preferably at 90 degrees to prograde)

90 degrees to prograde? That's the same as radial out. Are you sure?

 

 

Edited March 22, 2017 by Physics Student

[cratercracker]

Just. Don't . Nose . Dive

[AeroGav]

For comparison, mk1 inline cockpit ship re-entering.   Moderate nose up angle for lift, but like Scott i am aiming at the space centre, so the prime consideration was trajectory control

Craft file here - https://kerbalx.com/AeroGav/freedom-fighter

Video of me building it and launching it, here - https://youtu.be/XXhIb5OlSRY

 

[bewing]

3 hours ago, Physics Student said:

90 degrees to prograde? That's the same as radial out. Are you sure?

 

 

Yeah. Heating goes as velocity cubed, so to manage heat, you want to slow down. And going in belly first does a fairly good job of spreading the heat around, rather than concentrating it in your nose.

 

[sal_vager]

I prefer a 45 degree angle when re-entering with a spaceplane.

[FloppyRocket]

In Scott's video, the craft kept oscillating back to nose-forward because SAS was on Prograde.

[Urses]

@sal_vager

But you can not hold your altitude at 45 degrees? At 45 you tend to knock off back in Space if you a 'lill to fast.

Like @bewing said 90 Grades give you the most as aerobreak. This is why i tend to go normal/antinormal because my planes are mostly autoleverage and before i become lift for nose up and hold ,i have it much easier to hold belly for position. 

 

Edited March 22, 2017 by Urses

[sal_vager]

1 minute ago, Urses said:

But you can not hold your altitude at 45 degrees? At 45 you tend to rknock off back in Space if you a 'lill to fast.

 

Well, I build my craft to be stable at that angle, though it may take some up trim.

[Urses]

@sal_vager Thank you, it explains my curiosity.

[swjr-swis]

8 hours ago, Physics Student said:

The mk1 and mk2 cockpits burn up during reentry. Nothing seems to help.

Nothing? A single Linear RCS Port offset to the very nose of the Mk1 or Mk2 cockpits are all you need to protect them from overheating. They 'detach' the shockwave from your cockpit so it soaks up a whole lot less heat at reentry.

[martinborgen]

I don't really buy that the mk1 nose cockpit is supposed to be for airplanes only - it has the docking window on the back! 

[Wanderfound]

 

As others have suggested:

1) High AoA cobra reentry. The pointy Mk1 cockpits are perfectly adequate for this if you do it right; lightweight Mk1 aircraft lose speed very quickly in these conditions.

2) To make it easier, stick something in front of your cockpit. You need intakes: why not use the nose for that? Alternately, it's also a good spot for a shielded docking port or a nosecone LF tank.

[martinborgen]

How good is the shielded dockingport? It looks quite blunt? 

[Wanderfound]

1 hour ago, martinborgen said:

How good is the shielded dockingport? It looks quite blunt? 

Good enough.

[Kryxal]

Putting one LF tank up front also allows for trim adjustment unless you're bone-dry.  I ran a spaceplane out past the Kerbin SoI recently, and on atmospheric passes adjusted the fuel to reduce SAS needed.  I sort of had to do a skip reentry because I didn't have an extra 900+ delta-v to bring my orbit down again...

[bewing]

4 hours ago, martinborgen said:

How good is the shielded dockingport? It looks quite blunt? 

That's kind of the "point", actually. Blunt on ascent adds a little difficulty, because of the extra drag. But it also completely eliminates all your nose heating problems on ascent and reentry, because of the detached shockwave effect.

I find that a klaw on the nose works just as well for this.

 

Edited March 23, 2017 by bewing

[FullMetalMachinist]

4 hours ago, martinborgen said:

How good is the shielded dockingport? It looks quite blunt? 

To illustrate @bewing's point, here's a picture. 

https://commons.m.wikimedia.org/wiki/File:Blunt_body_reentry_shapes.png

That little cushion between the shockwave and the ship actually insulates it from the worst part of the heat. And KSP models this. 

[Gordon Fecyk]

Yes the Mk1 cockpit is really prone to exploding on re-entry. The Mk2 cockpit isn't much better; I forget how many ships I lost (and saves reloaded) because of the things.

It isn't impossible though. AeroGav might not approve of me re-entering 'full cobra' but it does seem to avoid the worst of the overheating:

Spoiler

 

That was with a stock Aeris 4A, but modified for this scenario. You just have to be gentle at first. Then there's the 'antenna aerospike' trick:

Spoiler

 

In this latter example the antenna is extended. In KSP 1.2 this will break the antenna if extended, but will hold if retracted. The radial mounted version, clipped into the nose, also works and gives the benefit of a radio link that can transmit science at all times.

Edited March 23, 2017 by Gordon Fecyk
grammar

[AeroGav]

@Gordon Fecyk Inspired by your example I've started a career game with Ferram Aerospace , Real Fuels, Real Engines and Advanced jet engine.

Re-entry is easier in Ferram,  because it obeys the law that lift quadruples when you double the speed.  In stock aero, there is too much lift at low speeds (supersonic, fuel laden aircraft coming in to land at the speed of a Cessna 172) and not enough at high speed.    It lands at 62 m/s (120knots) which is very fast compared with stock aero,  but at mach 1.5 i'm struggling to hold the sucker down, it wants to climb over 20km ! 

Also , in stock aero, lift drag ratio is constant from mach 1.7 out to orbital velocity.  Drag reduces drastically when you point prograde and is virtually nonexistent above 30km.  In FAR,  L/D ratio it steadily declines as you increase from mach 1.5 no matter how well area ruled your ship is and no matter how much you sweep back the wing. Also, most of it is parasite drag, unaffected by angle of attack.   It doesn't magically disappear when you point prograde, and there is still a noticeable amount of drag at 50km plus.

TL:DR - More drag above 40km in FAR.    40km and below, much more lift generated, you'll skim off the upper atmosphere and not drop down in the the peak heating zone till you've slowed waay down.