Re: Detection by IR

"Thomas.Barclay" wrote:
> 
> Brian,
> 
> I have to suggest that if your logic for suggesting you'd be detected
> anywhere in the system if you went active drive is the 'sector
blanking'
> that prevents FT ships from shooting out the rear, I must ask:
> 
> 1) Thrusters can fire without causing this interference. Does this by
> inference mean one could manouvre on these without detection? I think
you'd
> answer no.

	Indeed. That's a weakness that I didn't consider. Mostly, I was
indicating that interference as meaning that WHATEVER your drives, they
put SOMETHING out.

> 2) What is the practical range of IR detection? Bradford made some
comments
> based off of black body radiation, but didn't say much about what
ranges
> drives could be detected at. You figure across the system. I have to
wonder
> about that.

	I'm basing this on an article from rec.arts.sf.science (I
believe
that's the NG) that calculated that, with today's infrared telescopes,
we could detect the Space Shuttle's manuvering thrusters firing in the
asteroid belt, and the main engines firing significantly beyond Pluto. I
don't have the math or science training to verify this (although I'm
hoping to acquire it before I graduate), but there seemed to be a
consensus that the person who was doing the calculations knew what they
were doing.
	As for 'future drives' I'm guessing that they would radiate AT
LEAST as
much as the space shuttle (they have to move a larger mass at greater
acceleration, at least assuming 1 thrust = 1g). Also, the best way to
increase the efficiency of a drive is to make the reaction mass hotter
(and thus easier to detect), while the best way to increase the thrust
is to increase the mass of propellant used per unit time, thus also
making it easier to detect. Yes, ejecta would be directional, but it
would still be detectable pretty far out.

> So it seems that if you could close on a ballistic track with baffling
on
> and some method of dropping your hull to 150 K, you could probably
close to
> tactical ranges without detection. If you fire up your (presumably)
hot
> drives, you get picked up wherever you are, if someone is looking. If
you're
> a real stealth machine, you might even get under 6 mu, but your ship
would
> be storing heat at I imagine a high rate... which you would eventually
have
> to dispose of.

	Whereas essentially my view is that, given the information
above,
you'll be picked up (and your course plotted) as soon as you start
manuvering. If you go ballistic (undetectable or not), your course isn't
changing, so they know where you are ANYWAY (sure, with a VERY low-power
thruster burning VERY far away, you won't be detected, but it'll take
you forever to get anywhere.

> So what this seems to suggest is that comet-tail riders, asteroid
riders,
> and stealthed ballistic ships could close in on enemies with good
sensor
> arrays, but anyone just manouvring would be far more visible at huge
> distances. I guess it pays to have your patrol ships take a peek at
any
> strange objects floating through your space - and check for
> "hangers-on".....

	Unfortunately, asteroid-riders would tend to be fairly
detectable. Most
asteroids don't get near anything interesting, and even today people are
looking fairly hard at those that do....

-Brian Quirt