Big-S Wing Strake Burning Up on Re-entry

[Styles2304]

So I don't know if I'm re-entering improperly or if I need to redesign or what the issue is but on re-entry it seems that no matter what I do, the Big-S Wing Strakes overheat and explode. They're the only part that has problems.

When I'm coming in, I keep the nose pitched up between 15 and 20 degrees. I have two tail fins and two sets of wings and strakes where the top set of control surfaces raises like flaps and the tail fins open to either side for drag. I also raise all 6 air brakes. The wing strakes are the only part that heat to an unacceptable level and explode . . . the rest of the re-entry is fine but it's difficult to land without that extra lift.

Can anyone provide any input?

Edited May 1, 2015 by Styles2304
Switched to answered for lack of a better option

[InterCity]

I think that it's because the strakes are too high blast of heat from your reentry. Try reentering from lowest possible orbit and with a very shallow trajectory.

[Styles2304]

I'll give it a shot . . . as shallow as possible.

[ainurakne]

I have the exact same problem with the same parts with pretty similarly shaped shuttle-like spaceplane.

I have tried my descent many times over and over, using heat debug colors/temperatures to see what's going on, and they always get really hot and go *poof* much before the reentry effects kick in. At the time everything around them remains relatively cool.

It seems there are some problems with heat flux for this part - for some reason it absorbs heat really fast but gives it out very poorly, compared to other parts. I have thought about raising its heat capacity by filling it up with liquid fuel, but haven't had time to test it out yet.

[Screeno]

You have to pitch high in the thin atmosphere, as soon as you get in, pitch 45 and see how that shaves loads of speed in the upper atmosphere

[Styles2304]

I'm going to run some more test flights before I settle on the design so I'll see if I can't get my ship back to KSC and then I'll try another flight with fuel in the strakes. I'll let you know how it goes.

[MadMooMan]

I have this same exact problem, but it still happened when I set re-entry heat to 0% in the difficulty options, So I think its a bug either within the part itself or how the new re-entry heat system handles the part.

[ainurakne]

Ok, I had a successful landing.

I filled the wings with fuel before launch (but also made my re-entry trajectory as shallow as I could). It was a really close call as the temperature of those wing strakes rose up to over 1800 degrees, but fortunately the speed was already low enough by that time. So it is doable, but really hard.

I guess what amplifies the problem is that the wing strakes are attached to the cargo bay, which is hollow and thus has less thermal capacity, which means it gets hot faster than non-hollow parts (which was also visible using the thermal debug overlay). So the wing strakes that already have quite low thermal capacity have nowhere to conduct their heat to.

[Styles2304]

I was wondering about that. It seems almost like the cargo Bay is using the strike as a radiator. I'll see if I can come up with some sort jury rigged solution to offset the heat

[Styles2304]

So here's my report:

I attached the strakes to the big-s delta wing and maneuvered it into place, no change. I filled them with fuel, survived! But barely. The cargo hold was quite yellow also.

Lastly, I replaced the strakes with structural wings type A. They barely heated, the craft over all didn't change color... Landed without incident.

I can only conclude that the stakes are bugged.

[antbin]

The strakes have seemed very fragile to me. Here's a diff between Type A wings and Big-A strakes part.cfg:

Big-A strakes have "heatConductivity = 0.06", which is half the 0.12 default value.

They also have "dragAtMaxAoA = 0.6" compared to 0.3 for the Type A wings

It's probably the HeatConductivity flag. The Big shuttle Delta wing also has the same half-value heatConductivity, but it's so huge (and fuel filled) that perhaps it doesn't matter?

[Styles2304]

I can only assume it's bugged. I don't fill my Big-S Delta Wings with fuel and they don't heat up enough to notice any color change even when I did use the strakes. With the structural wings, nothing heats up to the point of color change aside from the strutural wings themselves and it's negligible.