skin heat/ core heat questions

[cephalo]

So, parts blow up if they have too much skin heat and/or too much core heat correct? Radiators affect only core heat directly correct? Does skin heat affect core heat in any way? How do radiators currently function in 1.0.5? Googling is confusing because there seem to have been changes, and also there are many rumors floating about. (radiators affect up to two parts away? False?)

So I have this re-entry craft that gets a lot of skin heat. I put radiators on it, and then I thought that's probably just dead weight so I removed it again. Now I'm having some heat issues that I didn't have before. The radiator was only the trailing side of the craft that got less hot, but connected to a part that was getting the brunt of the re-entry. I think maybe it was doing some good after all.

What are radiators and what do I do with them in KSP 1.0.5?

 

[NathanKell]

Nope.

There's three temperatures to keep in mind: Internal and skin for all parts, and core temp for certain parts (drills, ISRU, RTGs). Skin and internal heat conduct. Internal and core conduct. Skin radiates and convects. Radiators draw from internal and core.

[Chaos_Klaus]

It seems that there are no more passive radiators. Am I right?

[fourfa]

Do the solar panels act as passive radiators?  The tool tips claim they do, but as we know many of those are years out of date or refer to game mechanics that never existed at all

[cephalo]

1 hour ago, NathanKell said:

Nope.

There's three temperatures to keep in mind: Internal and skin for all parts, and core temp for certain parts (drills, ISRU, RTGs). Skin and internal heat conduct. Internal and core conduct. Skin radiates and convects. Radiators draw from internal and core.

Ok, I'm not clear on what that means. If skin conducts to internal, and radiators draw from internal, is there no benefit of a radiator regarding skin temp? When do parts blow up?

[Barrrrry]

16 minutes ago, Chaos_Klaus said:

It seems that there are no more passive radiators. Am I right?

I believe that the "panel" radiators are passive. (The ones that stick out, but don't move). I also think that the skins of most objects can cool in different environments (like Space), which cool internal temps. I could totally be wrong though

Edited December 11, 2015 by Barrrrry
More information

[fourfa]

They're not passive - they now draw electricity, I guess for liquid cooling pumps.  Not much, but enough to drain your battery in time warp if you don't have inputs

[cephalo]

Ok, I have discovered the debug option for looking at temperature, and I have found that the radiators can help a great deal during re-entry. Check out the following image on Jool:

The 'internal temperature' is much lower in this example than without the radiator (on the top forward fuel adapter) at this point in the descent. I assume the 'SkinToIntFlux' is the transfer rate between the skin and the internal, and it's a high number. When I pitch the craft up, the canards cool down very rapidly. By keeping the nose up as high as I can (it kinda rocks up and down) my canards have a chance to cool down. As the craft pitches down, the canards heat up to dangerous levels but they cool off again at the peak of the oscillation.

It's the radiator that is making this happen. Without it, I can't keep my canards. Eventually, the internal temperature slowly rises and reduces its cooling effect, but by that time we are out of the danger zone. Without the radiator the internal temp rises much faster and I can't cool the canards long enough.

So my craft can make it to Jools lower atmosphere intact. Now I need to work on the ascent back out, and that unfortunately has some opposite requirements to the descent. Weird things are happening to the CoM as fuel is consumed, the front heat shield throws me around a bit as I get back to supersonic (around 2500ms on Jool at 150km altitude). The problem with putting the CoM forward is that I can't pitch up well to cool my canards on the descent, but if put it too far back I have difficulty controlling the ascent. On my last test I touched the controls at a critical moment entering supersonic, (I should have just accepted a slight yaw) and went into a flat spin.

The craft has around 5000 dv, and I believe its enough to achieve orbit from ~115k altitude. Before I added the top drop tanks, I was able to almost make orbit with around 3000 dv.

Edited December 11, 2015 by cephalo
typos

[NathanKell]

18 hours ago, cephalo said:

Ok, I'm not clear on what that means. If skin conducts to internal, and radiators draw from internal, is there no benefit of a radiator regarding skin temp? When do parts blow up?

Skin <-> internal. So if the radiator draws from internal, it's indirectly helping skin too.

Parts blow up when skin temp > skinMaxTemp or internal temp > maxTemp. skinMaxTemp defaults to maxTemp if not set independently.

[Snark]

18 hours ago, fourfa said:

They're not passive - they now draw electricity, I guess for liquid cooling pumps.  Not much, but enough to drain your battery in time warp if you don't have inputs

And unfortunately, there's no way to turn them off (in stock).  The folding panels are fine because they turn off when you retract them (stop cooling, stop drawing power).

If you'd like to be able to turn the static panels on/off, here's a little mod I wrote that gives them a toggle switch.

[cephalo]

Thanks for the replies everyone. I do have one more heat related question. In every craft I have applied significant atmospheric heating to, the leading part always gets by far the most heat, even though other parts are every bit as exposed.

For example, in my picture I use a radiator to cool the canards, but I ended up solving the temperature problem by moving the canards aft a bit and on the side of the outer fuel tanks. They are just as exposed to the air stream, but they are getting much less heat there for some reason.

Does anyone know what decides how much heat a part will get? Why do areas near the nose get so much heat?

[NathanKell]

The leading part may have an attached shockwave, whereas parts further back--even if they are fully exposed--will be behind the edge of the shockwave.

[Chaos_Klaus]

the active radiator panels don't cool the part they are attached to. They cool whatever part is too hot.