Bradford's comments on IR

2 posts ยท Apr 18 2000 to Apr 18 2000

From: Thomas Barclay <Thomas.Barclay@s...>

Date: Tue, 18 Apr 2000 11:36:20 -0400

Subject: Bradford's comments on IR

If I understood correctly:

You indicated that ships without thermal protection are visible at 1 LS and
hard to detect at 10 LS.

You worked with 300K temp I believe.

You indicated ships could disperse their heat (or maybe even store it
internally by some method instead?) and thus (because radiation is a T^4
property), decrease their luminosity by 16 for every halving of temperature.

So, this to me says that if I could drop my temp to 150 K (a long way from
absolute zero) on the hull, I'd be visible only at 1/16th of a LS
(300,000
km/16 is roughly 20,000 km) . If I could drop my temp to 75K, I'd be
visible
at 1/256th of a LS (1500 km?).

So, if I read you right, and I can drop my hull temp by even half (to 150K), I
can make detection difficult to inside of 60,000 km (which I'd call a tactical
range). If I can drop it to 75K, I can probably sneak right up to within 6000
km (6") in a tactical scale.

Or am I missing something? I'd be interested to see some of the
math/assumptions/physical constants you used to back your calculations.

From: Laserlight <laserlight@q...>

Date: Tue, 18 Apr 2000 11:49:22 -0400

Subject: RE: Bradford's comments on IR

Thus spake Thomas Barclay:
> You worked with 300K temp I believe.

You indicated ships could disperse their heat (or maybe even store it
internally by some method instead?) and thus (because radiation is a T^4
property), decrease their luminosity by 16 for every halving of temperature.

So, this to me says that if I could drop my temp to 150 K (a long way from
absolute zero) on the hull, I'd be visible only at 1/16th of a LS
(300,000
km/16 is roughly 20,000 km) . If I could drop my temp to 75K, I'd be
visible
at 1/256th of a LS (1500 km?).

So, if I read you right, and I can drop my hull temp by even half (to 150K), I
can make detection difficult to inside of 60,000 km (which I'd call a tactical
range). If I can drop it to 75K, I can probably sneak right up to within 6000
km (6") in a tactical scale. <<

Making the assumption that you're approaching a target in a system which has
been inhabited a while (long enough for your adversary to set up sensor
platforms in several locations so you can't radiate heat "away from
him")...
I'd think you'd need to carry a chunk of ice with you to absorb heat.
Alternately you can spread it out over a greater area at a lower temperature,
but you'd still be putting out the same total energy.

(caveat: I passed the toughest physics class at my university...every day,
when I went to lunch...so the above is not guaranteed to be correct)