The Power of a Star....(calculations of Warship engine power and heat)

[Vehrec]

Earlier today I was talking on Discord with someone who is creating her own hard-SciFi universe, and she went off on a tangent I found interesting about fusion reactors.  Her 15 kTon frigate design, about the size of a medium dropship, with an acceleration of .13 g, 2000 tons of radiators, 1000 tons of drive assembly, and 5000 tons of internal fuel, giving it about 2 days of slow burn maximum efficiency transfer.  Plus the option to bolt on external fuel tanks for in-system work.  All of this is powered by a 5 TeraWatt reactor.

Compare this to a McKenna, which can accelerate almost 8x faster, is 128x more massive, has only 32% of the fuel, and has 20 times more burn time eeked out of it.  So...it's gotta be at least a hundred PetaWatts of reactor, right?  But you'll need to contain that reactor, which means you need to tap it off for energy-lets assume you only need 10% of it's power to contain the reaction, and you have a 98% efficent way to turn the charged particles into electrical power, so only .2% of the 100,000,000,000,000 watts is turned into heat.  That's still like 200 terawatts of heat to radiate.  Those radiator fins must be white hot!

[Daryk]

Strategic thrust has always been a problem in BattleTech, usually hand waved away by linking it to KF jump physics being discovered in a fusion reactor.

[Vehrec]

Strategic thrust has always been a problem in BattleTech, usually hand waved away by linking it to KF jump physics being discovered in a fusion reactor.

  Consider, however, the implications for weapons-heat!  If flank acceleration for the McKenna is 200 terawatts of heat, and that's only what, seven heat points?  How much power is wasted by the NPPCs!

[Daryk]

Oh, plenty... best not to look too hard at THAT sun... ;D

[Pat Payne]

  Consider, however, the implications for weapons-heat!  If flank acceleration for the McKenna is 200 terawatts of heat, and that's only what, seven heat points?  How much power is wasted by the NPPCs!

It's a good thing that BattleTech has acceptible breaks from reality -- otherwise how would a WarShip radiate all that heat quickly enough to keep from flash-frying the crew?

[DevianID]

The plog art where the mckenna's many fins are very clearly radiators is one of the cooler redesigns for warships, and what I wish was a thing from the start.

As for the reactors in Btech, even a small, .5 ton reactor can power infinite lasers/flamers, if you can keep it cool... So the fusion engines in btech are practically limitless for energy, only kept in check by burgeoning heat dissipation needs that make it more efficient to just run a second power source after the first 10/20 heat.  So on warships, you can potentially be cranking them up to just silly heat levels, and somehow containing all that heat and pressure with no wastage.  It almost seems like the engines in battletech eat heat, instead of emit heat, based on how the rules work.

[Vehrec]

I'm just saying, we need a colorization of that Plog-art where the McKenna's radiator fins are glowing properly white-hot from the rejected heat and flash-burning the paint off anything that comes too close. :D

[Daryk]

Plog has very reasonable commission rates, and since that's just a re-color of something he already did it might be even more reasonable... ;)

[cray]

The estimate for a McKenna's engine power is probably orders of magnitude low.

Exhaust power equals 0.5 x exhaust velocity x exhaust force / efficiency

If you use exhaust velocity in meters per second, force in newtons, and efficiency as a unitless fraction (0.00001 to 1), you get power in watts.

It's easy enough to find a McKenna's newtons of thrust. The problem is exhaust velocity. For ships that are using grams of fuel per second in strategic mode, you can find superluminal values of exhaust velocity (if you stick with Newtonian math). The resulting power value exceeds the amount of energy you can get from nuclear fusion of hydrogen, or potentially from antimatter.

[Paul]

The problem is exhaust velocity. For ships that are using grams of fuel per second in strategic mode, you can find superluminal values of exhaust velocity (if you stick with Newtonian math)

If I recall an ancient thread correctly (with Fallguy, to date it some) there is some 'gain' in the sense that the mass of the fuel goes 'up' relative to the vessel the closer to c the fuel is made, but still nowhere in the ballpark of removing the sheer magic of it all. I can't recall if it's better or worse for DropShips; I assume there's more magic in WarShips.