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# Heating created by different engines?

## Question

I've searched for information on engine heating, finding only results regarding atmospheric and speed heat effects.

I'm trying to figure out if the exhaust heat from engines is simply a linear function of thrust, or if there are other things going on?

Why do I want to know?  I have a career-mode spaceplane full of tourists that crashed on the mun, destroying the engines but leaving the mk2 passenger module intact.  It doesn't have docking ports, so I plan to land a space-crane of sorts next to it, grab it via Klaw and return the kerbal denziens home.  I don't want to bring the entire shipwreck though, so I want to use rockets to burn off the other sections of the wrecked plane.  Thus, whats the most space-arc-welding power per mass?

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Why you don't bring a vessel with enough passenger capacity to get all tourist, Klaw the wreck, transfer everyone and then release the wreck?

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3 hours ago, panzerknack said:

I've searched for information on engine heating, finding only results regarding atmospheric and speed heat effects.

I'm trying to figure out if the exhaust heat from engines is simply a linear function of thrust, or if there are other things going on?

I don't know if exhaust heat is proportional to throttle but that seems as good a guess as any.  What I do know, however, is that it's damn hard to burn parts up these days (maybe that changed in 1.3.1 as @Geonovast says but I'd be surprised).  Back before we got re-entry heating even a tiny bit of exhaust would explode a fuel tank, so you had to be very careful when placing Sepratrons on asparagus boosters.    Apparently, engine fire is a higher temperature than any part could stand, so instant boom.  But OTOH, you could make cool fireworks that way.....

HOWEVER, once re-entry heat became a thing, KSP started modeling heat flowing in and between parts, and also their specific heat.  So when you apply engine heat to 1 part, instead of immediately burning through and exploding it like before, the heat spreads all through that part at a rate seemingly proportional to its mass, and then will spread into adjacent parts, too.  And parts have to warm up to their exploding temperature throughout their volumes, not just in 1 spot anymore.  So you have to really cook a part now before it will explode, and there's always the chance that some more "flammable" (lower mass and lower exploding temperature) part elsewhere on the target will explode first.

Therefore, I don't think this idea will work very well today.

3 hours ago, panzerknack said:

Why do I want to know?  I have a career-mode spaceplane full of tourists that crashed on the mun, destroying the engines but leaving the mk2 passenger module intact.  It doesn't have docking ports, so I plan to land a space-crane of sorts next to it, grab it via Klaw and return the kerbal denziens home.  I don't want to bring the entire shipwreck though, so I want to use rockets to burn off the other sections of the wrecked plane.  Thus, whats the most space-arc-welding power per mass?

I recommend 1 of 2 things:

• What @Spricigo said above.
• Cheat the contract complete, then terminate the wreckage, tourists and all

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The way I understand it, and from my experience, is engine exhaust didn't heat any other part of the craft... until 1.3.1.

If you're on 1.3.1, you'll have heat damage from the engine thrust.

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This is the most Kerbal thing I've heard today. Please let us know how it went.

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Thank you all for the input!

I completely forgot about what Spricigo suggested; that you can transfer passengers through the Klaw.  I'll try doing just that.

I've continued to test exhaust-heating mechanics, imagining if you could reliably explode specific nearby parts it has great potential for cheap stage separation and more compact rocketship buids.  It's quite difficult to test on the surface of celestials, since the exhaust reaction will either push the target or you away-I try stabilizing with landing struts and counter-torque engines, etc.

What is Mr Headshot referring to when he says "cheat the contract"?  I thought the tourists must be returned to Kerbin for completion.

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Wouldn't it be simpler than using a claw to just have the crew EVA and walk over to a rescue craft?

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5 hours ago, Foxster said:

Wouldn't it be simpler than using a claw to just have the crew EVA and walk over to a rescue craft?

Tourists can't EVA.

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3 hours ago, Geschosskopf said:

Tourists can't EVA.

Ah, right. Been a long time since I played career.

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18 hours ago, panzerknack said:

What is Mr Headshot referring to when he says "cheat the contract"?  I thought the tourists must be returned to Kerbin for completion.

He means using the Cheat Menu, accessible by MOD+F12, to mark the contract as completed.

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Well, rarely do missions go as planned, it's usually "crap i angled solar panels wrong now drone is dead" or "what the VAB reverted my stages to wrong order", but this went beautifully - I landed a rover with a klaw-docking port adapter to make things line up, and everything went swimmingly

Pay no attention to the debris from other failed attempts heh.  Thanks again for the suggestions here, from now on my career passenger transports will definitely include docking ports as a safety precaution!

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This thread has given me a great idea for a mod.  Too bad I'm clueless on how to make one.

A ship-mounted laser cutter would be awesome.  Point it at the joint of a ship, use up an enormous amount of EC, generated a ton of heat, and BAM!  Ship cut in half.

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42 minutes ago, Geonovast said:

A ship-mounted laser cutter would be awesome.  Point it at the joint of a ship, use up an enormous amount of EC, generated a ton of heat, and BAM!  Ship cut in half.

Well, BDA Armory has weapons that do this sort of thing already (besides a whole bunch else, such as the ability to have drones fight each other for your amusement).

54 minutes ago, panzerknack said:

Thanks again for the suggestions here, from now on my career passenger transports will definitely include docking ports as a safety precaution!

Bravo!

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8 minutes ago, Geschosskopf said:

Well, BDA Armory has weapons that do this sort of thing alread

They'll break joints without actually destroying any of the parts?

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1 hour ago, Geonovast said:

They'll break joints without actually destroying any of the parts?

No, they destroy parts that get hit.

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I always heard a Sepraton was like a laser, a very damaging thin beam.  I imagine a sep would work well for this, especially if you could give it a reservoir of fuel rather than just the road-flare amount.

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2 minutes ago, GarrisonChisholm said:

I always heard a Sepraton was like a laser, a very damaging thin beam.  I imagine a sep would work well for this, especially if you could give it a reservoir of fuel rather than just the road-flare amount.

This used to be true, because back in the old days, exposing any small area of a large part to heat above its explosion temperature, even briefly, caused the whole part to explode.  But since we got re-entry heating, parts only explode once their entire mass has reached that temperature.  So the game now models the heat flux of engine flames (as in how much heat energy they deliver over time) and the thermal properties of parts (how much heat energy per ton is required to raise their temperature 1^, how fast they absorb heat, and how fast they dissipate it via conduction, convection, and radiation).  Because of this, Sepratrons are now pretty safe.  While the flame temperature is still quite high, it's not a very big fire, and it doesn't last very long, so it cannot heat most parts up to explosion temperature prior to burnout.

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On 1/10/2018 at 2:49 PM, panzerknack said:

I've continued to test exhaust-heating mechanics, imagining if you could reliably explode specific nearby parts it has great potential for cheap stage separation and more compact rocketship buids.

Fire-in-the-hole staging was pretty awesome, but it's pretty difficult to do reliably with the larger thermal tolerances of parts these days. Doing Node 0 rockets (which meant no decouplers) and using solid boosters to detonate the solid booster underneath 'em was oodles of fun. You could get to the Mun that way