Radiator area for 3e Vehicles

[mindbound]

I find the 3e Vehicles and its two supplements to be the most useful vehicle construction kit for both any edition GURPS and any "realistic" RPG, period. Right now I'm working on designs for a early XXIII century space fleet in a setting that's primarily built for the Stars Without Number (an OSR sci-fi system) that, while won't be using GURPS level of detail, still can very much benefit for the detailed vehicle designs as the starting point from which to simplify.

That said, I fail to find any rule for calculating the required radiator area for a ship to successfully get rid of the excess heat (which, for a military spacecraft without any superscience tech, is going to be considerable), either in the main Vehicles book or in either of the expansions. I'll probably just go and adapt the material from the Atomic Rockets site (a truly invaluable resource for any hard sci-fi worldbuilder!) but I'm wondering if there might exist something that has already been GURPS-ified. TIA.

[Crystalline_Entity]

I think Transhuman Space had rules for radiators in space in Appendix A, but you'd have to convert the simplified spacecraft design system there into GURPS Vehicles terms.

Edit: I've just checked my copy, it does have rules for radiators. They are (obviously) tied to the Transhuman Space design system so you'd need to do a bit of work to convert, e.g. working out what an "old fission power plant" is in Vehicles terms.

[mindbound]

Thank you! I'll try to get my hands on a copy of THS and work from there.

[johndallman]

Originally Posted by mindbound

Thank you! I'll try to get my hands on a copy of THS and work from there.

Available at Warehouse 23.

[Varyon]

If you're ok with only a modest level of resolution in this regard, GURPS Spaceships (a 4e product) has rules for main radiators. It's a binary switch if the vessel needs them or not (rather than something like "each SM+10 Fusion Reactor needs n square yards of main radiator, which weighs m tons"), but you get a list of what systems require them (SS1:31), how exposed and resilient they are (SS1:66, under "Targeting Exposed Systems"), and what happens if they are retracted or disabled (SS1:65); there are also options to use coolant to extend the amount of time radiator-dependent systems can function with restracted/disabled main radiators (found initially on SS1:31, and reiterated on SS1:66). SS simplifies the radiator arrays as having no appreciable cost and mass (or, rather, it states the mass of the radiator arrays are part of the cost and mass of the systems that require them).

[Anthony]

The radiators in spaceships don't scale quite right. There might also be rules in the vehicles extensions.

[mindbound]

There are no radiator rules in either of the two extensions. I think I'll try going with the THS radiator rules, they look like a reasonable approximation for game purposes, and I could always correct the values by Boltzmann law if I wanted to go for the extra detail (since this is not something anyone will be calculating at the actual table).

The binary option from 4e is what drove me to write this post. First of all, it's a given (there will almost always be exposed radiators in a non-superscience spacecraft of near to moderately far future). Second, I can't get very much useful information out of it regarding the actual shape and size of the ship, not to mention things like the distance from which it can be spotted even with engines off.

[Varyon]

Originally Posted by Anthony

The radiators in spaceships don't scale quite right.

I'm guessing the required surface area should scale with weight, while the Spaceships rules functionally have it scale with the vessel's surface area?

[Anthony]

Originally Posted by Varyon

I'm guessing the required surface area should scale with weight, while the Spaceships rules functionally have it scale with the vessel's surface area?

Yeah. Solar panels have the same issue.