Radiators and Real Fuels

[NFunky]

Does anyone know if the stock radiators do anything to retard boil-off when using Real Fuels?  I know about, and have Heat Pumps, but I am having a little trouble integrating it into my existing career setup.  They also require massive amounts of electricity, which makes sense, but is a pain to plan for.

Does it make any difference whether a radiator is in the sunlight?  For instance, could I put a row of radiators on one side of a cryogenic tank and make sure they are always in the tank's shadow?

And finally, does quantity make any difference?  If I use eight radiators, will that work better than four?  If so, does the effectiveness increase linearly with number of radiators, or does it start to fall off after a point?

I'm trying to do my own tests on these questions, but they take a solid amount of KSP time perform, and I figured I'd ask here before devoting too much time to it.

Thanks!

[IncongruousGoat]

I do believe radiators help mitigate/prevent cryogenic boiloff. Now, I'm not certain, since I've only tested with the full Realism Overhaul suite, but I don't think RO changes heat mechanics.

On the subject of radiators in the sunlight, yes, it makes a difference. The stock heat model accounts for radiative heating from the Sun. Oh, and more radiators should be more effective than less radiators. I don't know if the effect is linear-you'd probably have to do some empirical testing.

[NFunky]

Really good to know.  Have you used the Fuel Pumps mod?  Is it just more powerful radiators (i.e. electrically cooled), or do they work in a completely different way?  I only ask because I'm trying to work out whether it's worth me getting my career save to work with Heat Pumps.

I'm mainly interested in using refuelable hydrolox rockets for cislunar operations.  With no radiators, a hydrolox upper stage seems to begin serious boiloff after 24+ hours.  I've done a few tests sending unmanned upper stages to lunar free return trajectories, and after about a day, Kerbal Engineer starts showing my delta-v dropping rapidly.

I'm curious if anyone knows how the cryogenic fuel system in RF works.  Are the tanks pre-chilled ore something?  Do planets (Earth) radiate heat at all?  I'd like to understand why I can store a tank of hydrolox for a day without much loss, as well as why it rapidly begins to boil off after that.

Should I be posting this in the mods forum instead?

[bewing]

There are two types of radiators. Fixed and rotating. Fixed radiators are sensitive to sunlight. Rotating radiators rotate so that they are edge-on to the sun, and therefore do not have solar heating problems.

Rotating radiators cool your whole ship, including the fuel in the tanks (unless the mod doesn't support that).

Quantity does not matter with rotating radiators. There is a limit as to how much heat they can suck out of their surroundings, and as long as you are not mining or running RTGs or other heat-producing equipment, probably even just one radiator will limit out while running at partial capacity.

 

[NFunky]

9 hours ago, bewing said:

There are two types of radiators. Fixed and rotating. Fixed radiators are sensitive to sunlight. Rotating radiators rotate so that they are edge-on to the sun, and therefore do not have solar heating problems.

Rotating radiators cool your whole ship, including the fuel in the tanks (unless the mod doesn't support that).

Quantity does not matter with rotating radiators. There is a limit as to how much heat they can suck out of their surroundings, and as long as you are not mining or running RTGs or other heat-producing equipment, probably even just one radiator will limit out while running at partial capacity.

 

Thank you for this info.  Really good to know.  I assume you're talking about the stock radiators?

[bewing]

5 minutes ago, NFunky said:

Thank you for this info.  Really good to know.  I assume you're talking about the stock radiators?

yes

[NFunky]

17 hours ago, IncongruousGoat said:

I do believe radiators help mitigate/prevent cryogenic boiloff. Now, I'm not certain, since I've only tested with the full Realism Overhaul suite, but I don't think RO changes heat mechanics.

On the subject of radiators in the sunlight, yes, it makes a difference. The stock heat model accounts for radiative heating from the Sun. Oh, and more radiators should be more effective than less radiators. I don't know if the effect is linear-you'd probably have to do some empirical testing.

Thank you.  With RO, is it possible to build large, hydrolox (or nuke hydrogen) vehicles for long duration, deep space missions?  I'm not using RO, but I am using RSS, Real Fuels, Tweakscale, and some others.  I am getting tired of having to pack insane amounts of hydrazine based propellants in order to do any significant maneuvers  beyond earth orbit.

Anybody got any tips or suggestions for building large, interplanetary spacecraft?  Particularly, fuel type and engine choices?

[IncongruousGoat]

2 hours ago, NFunky said:

Thank you.  With RO, is it possible to build large, hydrolox (or nuke hydrogen) vehicles for long duration, deep space missions?

Honestly, I have no idea. I've only ever tried to keep LH2 using radiators for a couple of weeks, and that was to run some fuel cells. I suspect, however, that radiators can be used to keep LH2 from boiling off indefinitely, as long as they have power. It's the power that would be tricky, what with inverse square laws making solar power worthless much past Mars.

[NFunky]

Good point.  I have not yet unlocked RTGs, but I have the science, so I suppose that's what I should spend it on.  I was mainly planning for using hydrolox stages to make it easier to develop cislunar space, with an eye to possibly docking several of these stages in LEO for a manned mars mission.  Depending on how well cryogenics could store, I was maybe going to use a hydrolox or methalox return stage.  Looks like I may need to use hypergolics for that after all though.

I am going to try to get Heat Pumps working.  Does anyone know if Heat Pump radiators will work for things like ISRU and reactor cooling?  How about cooling solar probes?  I can't seem to find  much detailed documentation on this mod.