Nuclear Engine Cooling Help

[Mars-Bound Hokie]

I'm trying to make an interplanetary tourist ship, which means I need to get fuel efficiency down. I decided to go with the nuclear engines, but I read somewhere that they tend to overheat.

 

What parts can I use to prevent that? I installed engine pre-coolers on the engines themselves (which are powered by fuel tanks you'll find on planes), but I don't think that'll be enough once I escape the atmosphere. How useful are they? Recommended radiators?

[Ultimate Steve]

I think nuclear engine heat was a problem a few versions ago, but I don' think it's a problem any more. You should be just fine without any radiators, or any other cooling part.

But if I were you, I'd take a few radiators because they look cool just in case. Keep in mind that the static ones only cool a few parts around them, so try to put them near the engines.

[KeranoKerman]

I believe the engine pre-coolers won’t help. I would recommend thermal control systems because they generally look better. If you do use regular radiators, then remember that they only cool the block they are placed on and the blocks attached to that. If you want a sleek ship with no parts sticking out (to get those cool looks), then a mark 1 liquid fuel tank should have enough surface area when the engine is directly attached. Happy floating!

[Mars-Bound Hokie]

4 minutes ago, KeranoKerman said:

I believe the engine pre-coolers won’t help. I would recommend thermal control systems because they generally look better. If you do use regular radiators, then remember that they only cool the block they are placed on and the blocks attached to that. If you want a sleek ship with no parts sticking out (to get those cool looks), then a mark 1 liquid fuel tank should have enough surface area when the engine is directly attached. Happy floating!

Are you saying I should scrap the pre-coolers (and trade them for more fuel tanks)? If so, I must also let you know that the nuclear engines will not activate until I'm well past the atmosphere; if the coolers need air to work, then they're pretty much useless.

 

I don't care about my craft looking cool - you can't fly in style if you crash. Aside from that, I installed small thermal control systems on the pod; I could only fit in small ones thanks to the wings (for liftoff) and monopropellant engines (for docking)/turns. I also installed edge radiator panels on the parts directly above the nuclear engine. 

 

Is that sufficient?

[KeranoKerman]

I’d think yes. Just make sure to turn them on! Given that you have wings I’m gonna guess you have an interplanetary SSTO. Congrats! I may have had a probe on every planet except Eello, but my kerballed craft have only gone to Dres. And not back. Happy waiting! (For those darn transfer windows!)

Edited December 1, 2018 by KeranoKerman
Didn’t want to add a entire new post

[Mars-Bound Hokie]

It's technically not an SSTO - the wings are just there to increase stability during liftoff.

 

Anyway, for the pod in question, think of a Mk. 2 crew cabin with a hitchhiker and an inflatable heat shield (and a remote guidance unit so I can send in unmanned), 12 Mk. 1 jet fuselages (3 for each of the 4 nuclear engines), 1 Mk. 2 fuel tank, and 8 small thermal control systems. You think 8 will be enough for 4 engines?

 - also, do you think it is sufficient to do a fly-by of Eve and back? Orbital rendezvous with a station at Duna/Eve and back home?

 

UPDATE: To add 1200 More liquid fuel units, I plan to add 4 big-s delta wings. How do you think that will work out?

Edited December 2, 2018 by Mars-Bound Hokie
Update

[swjr-swis]

2 hours ago, Mars-Bound Hokie said:

if the coolers need air to work, then they're pretty much useless.

Precoolers are specifically configured to soak up more heat, conduct it slower, and irradiate it more efficiently than most other parts. They're not as efficient as radiators at it, but they don't use EC to have this effect and add very little drag. They do not need air to do this, their thermal effect works in vacuum too.

Precooler downsides:

• It 'only' carries 40 units of LF compared to 150 for the nacelle or DSI, but I never really understood why (or where?) this part carries any fuel anyway, so those 40 units feels like a bonus already.
• It only really affects directly attached parts, where radiators draw heat from further away (static attached+1, deployable the whole craft).

Squad toned down the heat buildup of the Nervs quite a bit at one point, to where they hardly ever need special treatment anymore. I find precoolers to be effective enough now even for prolonged burns. It sure beats the heavy drag and EC penalty of radiators, plus they are one of the best air intakes for spaceplanes.
 

[MR L A]

Editing:

37 minutes ago, Mars-Bound Hokie said:

It's technically not an SSTO - the wings are just there to increase stability during liftoff.

What do you mean by this? If it has a single stage it is an SSTO regardless of how it takes off or if it has wings, wheels, legs, none or all of the above

Edited December 2, 2018 by MR L A

[Mars-Bound Hokie]

6 minutes ago, MR L A said:

Editing:

What do you mean by this? If it has a single stage it is an SSTO regardless of how it takes off or if it has wings, wheels, legs, none or all of the above

It actually takes multiple stages for the pod to get into Kerbin's orbit.

[magnemoe]

18 hours ago, Ultimate Steve said:

I think nuclear engine heat was a problem a few versions ago, but I don' think it's a problem any more. You should be just fine without any radiators, or any other cooling part.

But if I were you, I'd take a few radiators because they look cool just in case. Keep in mind that the static ones only cool a few parts around them, so try to put them near the engines.

Yes they are generally not needed however if you have lots of engines and do long burns like 9 in the end of the long MK3 fuel tank doing an 10 minute burn its recommended. 
Radiators are needed for ISRU however. 
Use the fold out radiators the static ones only cool close parts and you don't stay in the atmosphere long anyway. 

[GRS]

use extendable ones, they remove heat much faster, screw the engine precooler, use them if you want some jet engine crafts, if you are not going to have a long burn, try to not use them, except to look cool

[Snark]

Moving to Gameplay Questions.

On 12/1/2018 at 1:42 PM, Mars-Bound Hokie said:

I'm trying to make an interplanetary tourist ship, which means I need to get fuel efficiency down. I decided to go with the nuclear engines

A good choice for high-dV craft that don't need much TWR. 

On 12/1/2018 at 1:42 PM, Mars-Bound Hokie said:

but I read somewhere that they tend to overheat.

Nope.  Not even slightly, unless you're taking them super close to the sun or something.

Once upon a time, many KSP versions ago, it was the case that they'd overheat, and needed radiators to stop from blowing up on long burns.  But that was a long time ago, and the heat production has long since been nerfed.  I don't think it's even physically possible to blow them up from overheating anymore, at least not from their own heat production.  They'll get warm, sure, but they won't come even close to blowing themselves up, even on a really long burn.

On 12/1/2018 at 1:42 PM, Mars-Bound Hokie said:

What parts can I use to prevent that?

None.  You don't need any parts.  Because they never overheat anymore. 

On 12/1/2018 at 1:42 PM, Mars-Bound Hokie said:

I installed engine pre-coolers

Engine pre-coolers don't actually cool anything, as far as I can tell.  It's just a name.  What they really are is a small LF fuel tank with some built-in air intakes.  Not needed for an LV-N ship in outer space.

On 12/1/2018 at 5:06 PM, Mars-Bound Hokie said:

8 small thermal control systems. You think 8 will be enough for 4 engines?

Zero would be enough, for any number of engines.

[Kernel Kraken]

Pre-coolers are aesthetic only and take in intake air to use for jet engines. Just put a few radiators on and it should perfectly fine,unless another engine is pointing at the engine. Thats a design flaw.

[Mars-Bound Hokie]

Scroll down to the "Return Pod" section of the following post, and you'll see what it looks like. The main stage (the one without the boosters) has 8 small thermal control systems for 4 nuclear engines and can carry 7 Kerbals and 6,400 units of fuel.

 - I would also like your input on my Eeloo fleet, please.

 

[FleshJeb]

On 12/3/2018 at 1:05 PM, Snark said:

Engine pre-coolers don't actually cool anything, as far as I can tell.  It's just a name

Go take a look at the CFG file. They have an emissive constant of 0.95. Most parts IIRC are 0.60.

I’ve been getting deep in to thermal engineering for extreme aero braking. It’s more fun than you might think.

[Duck McFuddle]

I don't have many issues with the nuke engines overheating, but I probably should be more careful. I guess just have a few radiators because they siphon off extra heat and (As mentioned by Ultimate Steve), look cool and add to the overall "Spacefaring" look of the ship.