How exactly do radiators work? Can I use them to help with aerobraking?

[yorshee]

I have this huge ship that I want to aerobrake at Eve but stuff keeps overheating which is understandable because, well, it's Eve. Heatshields don't help because the rocket is so long, any slight deviation from the retrograde marker means the back (front?) end of the rocket gets fried.

Would attaching radiators to the craft help or will the radiators themselves overheat? If they could help, could I attach the static radiators anywhere or do they specifically have to be attached to the parts that overheat?

If radiators are no use, what else could I use to aerobrake this craft? Or should I just pack more fuel so I can get captured via retro burning?

Edited July 26, 2015 by yorshee

[Feradose]

Try keeping the radiators away from the burny flamey side or it will work in reverse and warm you up, possibly overheat.

[Geschosskopf]

Technically, radiators should NOT help with reentry heat. Heat only moves from hotter things to colder things. During reentry, the air is hotter than the rocket, which is why the rocket heats up. Therefore, the rocket can't dump heat from the rocket back into the air, and trying to do so with radiators should instead make the rocket heat up faster by increasing the surface area through which it can absorb more heat from the air.

If radiators do in fact help ships survive reentry heat, that just points out the brokenness of the underlying system. So the better way to deal with the heat issue is just to turn down the heat level and not even try to use radiators. Your ships would be more realistic without them and if the underlying system is broken anyway, there's no shame in avoiding the problems it causes.

[Laie]

Radiators are of very little (if any) use during reentry.

I suggest you turn on the thermal data in the debug menu and see what exactly is going on when your ship blows up. I suspect that it will be because some part's surface temperature goes over the threshold -- radiators won't help you with this.

The only situation I found where they provide any benefit at all is during long entries when the surface heat creeps into the parts and becomes just plain heat. The radiator has to sit on the leeward side of the part that is getting too hot (preferably no flames at all at the radiator) which can be tricky to assemble, and for all the effort the amount of heat you shed is very small. Pretty much everything else you can do will be more effective than trying to find just the right spot for a radiator.

Keep some fuel handy and do a retro-burn when the heat gets serious. Attach wings and try a gliding entry (in terms of weight, that's totally affordable... part count can become nasty, though). Exploit the glitch where occluded parts receive much less heat but still create full drag (airbrakes FTW).

[Chyort]

Heat shield on one end, Airbrakes on the other to keep it angled properly as it skims the atmo(And you shouldn't have to dive as deep), and possibly radiators hidden in the heat shield's shadow to help magically keep everything cooler.

That is what i would try anyways.

[X-SR71]

I must be missing something - I have a huge 150mass ship with 4 LV-Ns plus full ISRU setup. After launching, it refueled in minmus, then it visited gilly, ike, dres, and pol, extracting and refueling along the way. I have now returned it to kerbin orbit. No radiator and no dangerous overheat, even at 13min+ burn times. Are radiators even necessary?

[Hagen von Tronje]

AFAIK the most straightforward answer is to go slower, i.e. bring more fuel. At least, I don't think I'd want to rely on aerobraking to have enough to safely land, but I'm not such a great pilot so I try to account for that. Also this seems like it would lead to imprecise landing and maybe splashing you into the ocean.

You can survive going in surprisingly fast (at least surprising to me) but if you're going in too steep or too fast, you're toast, no questions asked. Drogue chutes, A.I.R.B.R.A.K.E.S., and heat shields can all save on fuel if you can put them to use, really it's just like Kerbin but harder (and no jets).

Edited July 26, 2015 by Hagen von Tronje

[Laie]

@X-SR71: nope, you're right: the LV-N heat has been cranked down enough so that you can do very well without any heat sink. There may be exceptions, like if you put insulating bits between the engine and the nearest tank... but by and large, radiators seem to be unnecessary.

I have an inkling that it won't stay like this forever. Heat may make a comeback in as a limiting factor in ISRU, for example.

[FungusForge]

As I discovered with my own testing, the radiators will make it worse. They were designed so heat would easily transfer to them, however if the radiator is directly heated it applies the heat to the parts is attached to. The part the radiators are attached to will evaporate extraordinarily fast compared to the part being directly heated.

[yorshee]

I see, looks like I'll have to retro burn outside of Eve's atmosphere to get captured. More fuel it is, then.

[Laie]

*Capture* at Eve is pretty much out of the question. Maybe a very lightweight probe with a big heatshield, but nothing substantial.

As to your original question: static panels only work on the part they're attached to. For practical purposes, they increase that part's surface area.

The foldable parts appear to come with a lot of (invisible) internal plumbing. They will assume a temperature that's pretty close to the hottest part of your vessel, regardless of where you put them. Be aware that some of that heat creeps through their attachment point and back into the part they're attached to. This could potentially cause trouble.

[Megadeath]

I have a spaceplane that survives entry better with the foldable radiators. Though I do use quite a shallow reentry with it. They are in the vessels shadow, and survive deployed quite deep into the atmosphere so long as I don't manoeuvre or use engines.

[Kurld]

Well, I guess I'm confused... what are these parts supposed to be used for?

[Laie]

As of a few weeks ago, the LV-N engine created so much heat that vessels were blowing up. The players demanded that the heat be turned down or we get radiators -- now we have both.

Heat management is an important part of real-life spacecraft design, the ISS has about as much radiators as it has solar panels. It may well be that future versions of KSP will introduce less ridiculous heat sources that make heatsinks mandatory. But right now, the panels aren't really vital.

Anyhoo, they're supposed to rid you of heat *in space*. Realistically, they should be totally useless during reentry.

[Geschosskopf]

Well, I guess I'm confused... what are these parts supposed to be used for?

Radiators? They're intended to keep a ship from overheating due to prolonged exposure to intense, unfiltered sunlight and the slow build-up of heat from the long-term operation of its various systems. That's what they do in real life. The whole thing about using them to cool rockets when running nuclear engines and during reentry is the result of sheet technical ignorance on the part of a large proportion of the community.

The story goes like this: In 1.0-1.0.2, nuclear engines suddenly became effectively useless because Squad decided, for no apparent or justifiable reason, to make them blow up if you ran them for very long. This was totally unrealistic because in real life, nuclear engines are cooled by the flow of the fuel, which takes the heat and expands, thereby creating thrust. That's their entire operating principle so overheating during operation isn't a problem with them.

However, instead of clamoring to fix this basic problem with the game, a lot of technically ignorant folks demanded radiators to deal with the new heat, and even thought this heat was realistic. Some more technically savvy folks, however, clamored to remove the silly unrealistic heat instead. So in 1.0.4, Squad catered to both groups. Nuclear engines now produce a LOT less heat than they did in 1.0.2, AND we have radiators. Because all the ignoramouses who were demanding radiators for their LV-Ns now no longer needed them for that, and thought (based on mods, I guess) that this was the only reason to have them, they think radiators are now useless.

These folks have obviously never been to Eve or Moho in 1.x. 1.x didn't just add reentry heat, it added solar heating, and that's pretty friggin' intense inwards from Kerbin. So at Eve you can, and at Moho you SHOULD, use radiators for their intended, real-life purpose of keeping your ship from frying while just sitting in orbit. But if you stay at Kerbin, or only go to Duna and Jool, then you don't really need radiators.

Of course, there are mods that require radiators. Near Future, for example, on its nuclear reactors. But also Atomic Age, which adds a bunch of nuclear engines, some of which produce even more heat than LV-Ns in 1.0.2.

Edited July 28, 2015 by Geschosskopf

[Kurld]

I understand about why you would want them in real life. The Apollo SM had them to radiate heat from the fuel cells and other sources as I recall. I skipped 1.02. I'm getting ready to send a mission to Moho in 1.04. Do I need radiators?

[Fearless Son]

On that subject, I have found thermal control systems useful in certain suborbital spaceplane designs where the hull heats up due to its acceleration during ascent. It needs to lose that heat before reentry lest it go over the threshold, and the thermal control systems help get rid of it for its brief stay above the atmosphere.

[Randazzo]

*surprisingly ugly quote*

I released both the Heat Management mod and LV-N temperature adjustment in this period, and heat management beat out the LVN temp adjustment by margins so enormous that the latter is hardly worth a mention.

[KerikBalm]

Geshoss... calm down.

They nerfed LV-N heating... most players complained that the heating shouldn't have been there to begin with.

Now we have stuff good for sundiving, and a new system for mods to work with... I used radiators before with "fusion reactors", although I wasn't using the popular mods per se... just and extendable thing that generated "coolant"

Now we have something that works for sundiving, and opens up easy modding possibilities for adding "reactor" parts that produce a lot of heat and require use of these radiators.

I prefer to think of them as a "here's some fun toys to work with, now mod to your tastes"

[gary.townsend]

Geshoss... calm down.

They nerfed LV-N heating... most players complained that the heating shouldn't have been there to begin with.

Now we have stuff good for sundiving, and a new system for mods to work with... I used radiators before with "fusion reactors", although I wasn't using the popular mods per se... just and extendable thing that generated "coolant"

Now we have something that works for sundiving, and opens up easy modding possibilities for adding "reactor" parts that produce a lot of heat and require use of these radiators.

I prefer to think of them as a "here's some fun toys to work with, now mod to your tastes"

Well along this line of questioning then i've had Numerous probes (3 minmus, 1 Mun, 1 Kerbin) decide to explode since i started playing again in 1.0.4 a couple weeks ago. I don't have deadly reentry turned on but something is making my probes go pop. it's to the point htat i don't dare leave my probes around minmus in anythin higher than 10x warp when they are runnng SCANsat equipment haven't nailed it down to a specific part yet though and i am including extendable radiators as the non extending ones didn't seem to do anything.

[KerikBalm]

I've heard people reporting these random overheats.... but so far I haven't encountered anything like that... strange...

[jackboy900]

Technically, radiators should NOT help with reentry heat. Heat only moves from hotter things to colder things. During reentry, the air is hotter than the rocket, which is why the rocket heats up. Therefore, the rocket can't dump heat from the rocket back into the air, and trying to do so with radiators should instead make the rocket heat up faster by increasing the surface area through which it can absorb more heat from the air.

If radiators do in fact help ships survive reentry heat, that just points out the brokenness of the underlying system. So the better way to deal with the heat issue is just to turn down the heat level and not even try to use radiators. Your ships would be more realistic without them and if the underlying system is broken anyway, there's no shame in avoiding the problems it causes.

Well if the radiators are not heating up then the atmosphere on that side of the craft is colder than the re-entering side.

[p1t1o]

Can I just ask if I am understanding a few things right:

So radiators work fairly logically - in that they will increase the rate of heating if they are exposed to re-entry airflow.

However, they do provide a modicum of cooling if sheltered from airflow (leeward side).

Fixed radiators cool only the part they are attached to.

Extensible radiators remove heat from the craft as a whole but may redistribute heat to the part it is attached to, increasing heat locally.

Radiators not necessary outwards from Kerbin as not many parts produce that much heat?

Exploit the glitch where occluded parts receive much less heat but still create full drag (airbrakes FTW).

What is the deal here? I thought that my centre-of-drag/lift was a bit far forward launching my last few probes (with procedural fairings).

Is this a global phenomenon? Ie: parts in cargo bays and within fairings still produce drag? Or does it refer to occlusion by the craft itself (ie: if located leeward from airflow, as in the radiator example above)? Do they still produce drag even if they are occluded by forward parts of the craft? (Eg: parts in a cargo bay, rearward of the forward fuselage...)

Does FAR have any effect on this?

(I'm recently returned to KSP ater a long hiatus so Im not familiar with the common bugs/idiosyncrasies anymore)

Thanks

[Laie]

[radiators] do provide a modicum of cooling if sheltered from airflow (leeward side).

Yes, but. Even under the best circumstances you can expect only verly little cooling while aerobraking. I don't think it's ever worthwhile, certainly not when compared to other options.

Fixed radiators cool only the part they are attached to.

Yes.

Extensible radiators remove heat from the craft as a whole but may redistribute heat to the part it is attached to, increasing heat locally.

Not so sure about "the craft as a whole": In my experiments, they quickly assume the temperature of the hottest part on the vessel, which tends to be an engine.

Regarding re-entry and occlusion: Parts inside fairings and bays are supposed to be shielded no matter what (beware the fiendish bugs, though).

For purposes of reentry heat, the foremost parts make a bow wave and create a bubble where trailing parts are relatively well-protected. This means that radially mounted pieces behind a heat shield (or engine or...) can be protected from the heat even if they stick out.

For purposes of drag, however, this doesn't work. Radially-attached parts will always create drag no matter what.

Taken together, this allows for smartly-placed airbrakes to create a lot of drag without being subject to re-entry heat.

[Fearless Son]

Of course, there are mods that require radiators. Near Future, for example, on its nuclear reactors. But also Atomic Age, which adds a bunch of nuclear engines, some of which produce even more heat than LV-Ns in 1.0.2.

That was something I always thought radiators would be great for, nuclear power plants to make large numbers of ion engines on more massive craft somewhat practical (assuming you could model, plot, and execute continuous acceleration.)

I am reminded of a bit late in ​The Martian where they say that they have to turn down the output on the reactors due to tarnishing of the heat dispersing panels making them less efficient and risking reactor overheat if run at full capacity.