Steve Jackson Games Forums - View Single Post - [Spaceships] IR Signatures for the power plants and drives in Spaceships 7

Anthony · 09-29-2017, 04:21 PM

Note that the existing rules for IR signature don't bear a lot of resemblance to reality.

The minimum energy output of a drive is 0.5 * thrust * ISp; if we convert to spaceships this works out to 7.2MW * (accelerator/1g) * (delta-V per tank/1 mps) * 10^(SM/2). Looking at a couple of examples:

Chemical: 3G, 0.15 mps/tank, so 3.2MW * 10^(SM/2).
Ion drive (fission reactor): 0.0005G, 3 mps/tank, so 11kW * 10^(SM/2).
Nuclear thermal (TL 9): 0.5G, 0.45 mps/tank, so 1.6* 10^(SM/2).

IR signature should probably be something like 3 * log10(power) - 7 (+0 at 200W), so at SM +6 we get:
Chemical: 3.2GW, log10(power) = 9.5, signature = +21 (SS1: +11)
Ion: 11 MW, log10(power) = 7, signature = +14 (SS1: +12)
NTR: 1.6GW, log10(power) = 9.2, signature = +20 (SS1: +12)

09-29-2017, 04:21 PM	#4
Anthony Join Date: Feb 2005 Location: Berkeley, CA	Re: [Spaceships] IR Signatures for the power plants and drives in Spaceships 7 Note that the existing rules for IR signature don't bear a lot of resemblance to reality. The minimum energy output of a drive is 0.5 * thrust * ISp; if we convert to spaceships this works out to 7.2MW * (accelerator/1g) * (delta-V per tank/1 mps) * 10^(SM/2). Looking at a couple of examples: Chemical: 3G, 0.15 mps/tank, so 3.2MW * 10^(SM/2). Ion drive (fission reactor): 0.0005G, 3 mps/tank, so 11kW * 10^(SM/2). Nuclear thermal (TL 9): 0.5G, 0.45 mps/tank, so 1.6* 10^(SM/2). IR signature should probably be something like 3 * log10(power) - 7 (+0 at 200W), so at SM +6 we get: Chemical: 3.2GW, log10(power) = 9.5, signature = +21 (SS1: +11) Ion: 11 MW, log10(power) = 7, signature = +14 (SS1: +12) NTR: 1.6GW, log10(power) = 9.2, signature = +20 (SS1: +12) __________________ My GURPS site and Blog.