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mikey117

Delta wing exploding on reentry

Question

Does anyone know why my mk3 spaceplane wings keep instantly overheating?(big delta wing)

It performs fine during ascent, however when trying to return from the mun the wings instantly overheat as soon as I enter the atmosphere. I was originally putting periaps at around 50,000m. I then thought well I obviously need to do a more gentle aerobrake . But the same thing happens even If I put periaps at 65,000m.

Really frustrating me now. Also I'm on console . Not sure which version the console is currently on. 

So just thought I'd ask if pc players had the same /similar issue with an earlier build of the game?

 

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Can you post a picture of the craft?Are you sure its the wing thats overheating or another part?

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4 hours ago, mikey117 said:

Does anyone know why my mk3 spaceplane wings keep instantly overheating?(big delta wing) 

How fast are you going when you hit atmosphere?

4 hours ago, mikey117 said:

however when trying to return from the mun the wings instantly overheat as soon as I enter the atmosphere

If you're returning straight to atmosphere from the Mun, without any braking before hitting atmosphere, that's awfully fast for a craft without a heat shield. Are you going 3000+ m/s? What if you brake by a few hundred m/s before reentry?

4 hours ago, mikey117 said:

I was originally putting periaps at around 50,000m. I then thought well I obviously need to do a more gentle aerobrake . But the same thing happens even If I put periaps at 65,000m. 

You've got it backwards (don't feel bad, it's a common mistake). A really high Pe like that will generate tons of heat while not really slowing you down at all. Result: you get fried. Generally you want to aim for a Pe in the 30-35 km range, certainly no higher than 40 km. (I'm talking in general, here. Not sure whether that would do the trick in the case of your particular craft.)

 

Also, out of curiosity, 1.how much does your ship mass when it hits atmosphere, and 2. what angle of attack are you?

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Thanks for the quick reply. Yeah now that you mention it, I have noticed spending too long at higher altitude causes more heat with deorbits from around kerbin.(not really sure why I didn't make the same correlation with mun return). Thanks for the logic recalibration ,lol

Tbh it's one of the things I love about this game/ learning orbital mechanics in general. A lot of  counterintuative things to wrap your head around.

59 minutes ago, Snark said:

you're returning straight to atmosphere from the Mun, without any braking before hitting atmosphere, that's awfully fast for a craft without a heat shield. Are you going 3000+ m/s? What if you brake by a few hundred m/s before reentry?

I will probably need to try slowing down a bit first. And will try a few different reentry  profiles . I'm not at home at the moment, but i will let you know if i am still having issues after a few attempts.

Not sure what craft mass is at this point ,but its a big mk3 cargo ssto, so will still be pretty heavy at this point.

2.well I tried my usual 30° and then also tried to nose into it a bit more to take advantage of the heatshielding on the leading edges of the delta wings. Still no luck.

But yeah I will try ,try and try Again until successful as is the Kerbal way. 

If ksp came in a box with disc instead of an age warning it would have a :Caution stubbornness level  required; -very high:confused:

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2 hours ago, mikey117 said:

Not sure what craft mass is at this point ,but its a big mk3 cargo ssto, so will still be pretty heavy at this point. 

But empty of fuel, yes?

Anyway, if it's heavy/dense, that will make reentry more punishing.

2 hours ago, mikey117 said:

2.well I tried my usual 30° and then also tried to nose into it a bit more to take advantage of the heatshielding on the leading edges of the delta wings. Still no luck. 

Oh dear lord no.

First, "heat shielding on the leading edges of the wings" isn't a thing. At all. Maybe in IRL spacecraft, but not in KSP. Any given part has the same temperature tolerance throughout.

Second, "nosing into it" (by which I assume you mean pointing :prograde:) is the absolute worst possible thing you could do. The name of the game here is to generate the most drag that you possibly can, in order to slow below charbroil speeds before you go kaboom. Pointing 90 degrees up would be great, so that your wings are presenting big flat draggy surfaces directly at the oncoming airflow. Pointing :prograde:, on the other hand, is minimizing your drag, which is the worst possible thing to do, because that preserves your lethally high speed until you get deep into atmosphere.

30 degrees can be a nice compromise between lift and drag, at LKO reentry speeds. At higher reentry speeds, though, you need drag more and you need lift less, so a steeper AoA is a good idea.

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It's a combination of the following:

(1) You're coming in too fast (from too high an orbit)

(2) You're coming in at too shallow a re-entry corridor

(3) Your craft is too heavy

(4) Your re-entry attitude is too nose-down

Changing any of the above 4 factors will reduce heating. 

If you're coming in hot you will want to keep pointed straight up as long as you can, or until you're down to a sane re-entry speed, whichever comes first. If you can't, it means your craft is too nose-heavy and you need to pump ballast backward; if that's not sufficient, you need to tune/redesign. Also you will want to be carrying minimal fuel; if you still have significant amounts, burn it off -- this addresses (1) and (3) at the same time.

Spaceplane re-entries direct from a Munar transfer are on the hotter side of things, so expect to have to tune to survive it.

 

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Even with all that, losing wings with a 65 km periapsis is a neat trick, sounds more like skin overheat than internal overheat.

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Posted (edited)

Not implying this is an issue, but without craft, all avenues need to be explored...

What is your lift to mass ratio? Stalling on wings designed for full wet mass takeoffs (without said wet mass) are a big reason space plane reentry works. I've had successful cargo SSTO designs that would burn up if they didn't dump excess fuel at an orbital depot before reentry.

I would consider aerobrake to LKO before deorbit pass (two+ pass reentry). That initial bleed of energy is your most hazardous time. Popping back to vacuum for 15+ minutes during deorbit really helps thermal management.

YMMV. I don't use space planes that do both SSTO and interplanetary. There isn't much point to haul jet engines out of LKO (except for Laythe). My interplanetary space planes use Mk2 bodies for extra drag and only capture to LKO from SOI boundary.

Edited by ajburges

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