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plane cargo bay heat insulation?


FancyMouse
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Not sure whether I miss anything, so I'm coming to ask.

I'm having a mk2 cargo plane with a probe inside the cargo bay and I want to drop the probe to some distant place on Kerbin. When the plane flies at 1.2km/h for a while, the probe core explodes. Apparently heat conducts fast inside the cargo bay and causes the part with the lowest max temp, the probe core, to explode.

Looking at http://wiki.kerbalspaceprogram.com/wiki/1.0#Heat_Simulation, it says (I know I can't totally trust that, but at least this isn't outdated information, or is it?):

  • Service modules, fairings and cargo bays can be used to protect parts inside from heat.

But seems a simple attach doesn't insulate heat well... How do I protect my probe in the cargo bay from the heat of my jet during flight?

I've tried:

1. Heat shield. It doesn't quite work as it's a pretty long flight. I've tried that in a much shorter flight and it was already consuming ablator too fast.

2. Service bay seems to insulate heat to some extent, but my probe doesn't fit in a service bay (to be more precise, the biggest RT antenna which basically just occupies a whole length of a short cargo bay). Seems ModuleConductionMultiplier is doing the job, but only service bays have this, not cargo bays, not fairings.

Or I need to try some mods? I'm not opposed to mods but is there a stock solution at the first place?

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Need to dissipate the heat faster than the probe absorbs it. I've had some success with Ox-Stat panels- probably not to the extent you are stressing the part. You can mount a fair amount of them directly to the probe body and see if that works.

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I have seen some severe and abnormal overheating with some science instruments placed on the back face of a mk2 cargo bay. Technically that means they were attached to the part behind the bay, but they still should have been protected. I'm not sure whats going on, but at one point I had the thought that it seemed like they got incoming heat flux like they were outside the bay, but outgoing heat flux like they were inside of it. I need to do more testing, but I don't recall having the same problems with the front edge of the cargo bay.

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^^ I was just suspecting the same thing - I didn't dare opening the cargo bay, but for testing purpose, I opened it during flight, and my front antenna is damn hot as if it was exposed to air. I'm pretty sure I stack attached everything, but I did attach it at the back. Just trying put it in the front now.

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They are no longer overheating from "air friction" directly. They are overheating through conduction from the element they are attached to.

One silly trick which should protect them: use an "engine precooler" as their mooring element. The precooler has an insane heat dissipation constant, so it should protect the probe from conductive heating.

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They are no longer overheating from "air friction" directly. They are overheating through conduction from the element they are attached to.

One silly trick which should protect them: use an "engine precooler" as their mooring element. The precooler has an insane heat dissipation constant, so it should protect the probe from conductive heating.

It's for sure not conduction after I diagnosed with F11 as I mentioned in #4. My setup is like this (sorry no pics because I've already changed it)

[ Antenna - Probe - some cubic struts - decoupler - Cargo bay back ]

where the whole [] is the cargo bay. When I flied near 1km/s, I press F11, opened the bay, and then everything except the antenna is moderately hot (still mostly red, not close to yellow), while the antenna is extremely hot. Can't say for sure about probes because I can't see it well, but I have RTGs radially attached to cubic struts and they have the same max temp and they're not hot at all - kind of proves to me that conduction is not the issue, since the heat cannot be conducted from the back of the cargo bay if RTGs don't get hot (they're even closer to cargo bay attachment point).

I also tried to use the solution from heat management between decoupler and cargo bay. Not better at all.

My initial testing of moving the payload to cargo bay front seems solves the problem - even without heat management. I'm having some other troubles about the design, and will update when I have final results.

- - - Updated - - -

No... problem isn't solved. It wasn't the cargo bay back problem. Then let me post some pics.

First design inside the cargo bay. Pretty much what I described in #6 except it's moved to cargo bay front:

PoB7lXn.jpg

Next, in-flight F11. Note note that inside the cargo bay, only the antenna (not even the probe) is overheat... note the probe has max temp 1200, while the antenna is the RT GX-128 that has max temp 2900.

H4YzsoO.jpg

ok now I'm totally confused.

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