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# Re: Further thoughts on hitting with lasers

From: Jonathan white <jw4@b...>
Date: Wed, 25 Feb 1998 08:33:02 +0000
Subject: Re: Further thoughts on hitting with lasers
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At 15:58 24/02/98 -0500, you wrote:
>Hi there!
>
>I have been doing some number crunching on how difficult it would be to
>hit a ship with lasers once the targeting system had locked on and I
>thought I would share it with you.  This is by no means exhaustive but
>it is accurate for the premises.
>
>1. The target ship is 1000 feet long (sorry if you use metric but I was
>raised with feet even though Canada is officially metric now).
>2. The target ship is moving 10,000 miles per hour relative to the
>targeting system.  Comparing that to B5 and other sci-fi shows that is
>VERY fast.
>3. The target ship is moving along the long axis  ie. it's bearing is
>4. Laser light travels at 186,000 miles per second.
>10,000 miles per hour equals 2.777777 miles per second
>2.777777 miles per second equals 14,611.11 feet per second
>therefore a 1,000 foot long ship would cover its own length in 1/14
>second
>This would mean that targetting the centre of the ship and firing would
>hit somewhere along its length
>as long as the beam didn't take more than 1/28 of a second.
>Therefore
>it would hit at a distance of
>186,000 divided by 28	or 6,642.85 miles. Now I am not suggesting that
>targeting systems or laser beams would be effective at that distance
but
>it does show that at a range of 100-200 miles you are going to hit as
>long as you push the button and are targeted on the enemy.  You can
play
>with this by changing the target speed, angle of the target, how well
>weapons are aligned to the target (and that will have some effect) but
>if you can target it you will hit it.	It also means if the laser is
>pointing at a fighter which is closing to kill the laser will hit every
>time as at that distance the laser is just travelling too fast to miss.
Nice calculation. What you have deduced is perfectly reasonable. You are
also correct that the the closer the ship the easier it is to hit (in
fact,
if you look at it in vector terms, as the ship gets closer the relative
tracking speed - the angle you have to move the laser through to keep it
on
target - approaches zero). The problem with this in the real world is
keeping the beam on exactly the same spot for that 1/28th of a second,
rather than just within your 1,000 foot diameter. After all, it's
probably
doable to vapourise a (say) one foot circle of hull in 1/28th of a
second,
but a lozenge 1 foot in width and 1,000 feet long? Heck of a lot more
energy required.

While we are vaguely on the subject, anyone who can find a copy should
check out the Colonial Marines Tech Manual (I think it's called), a
piece
of licenced fluff from the Alien movies. It has a section on space
combat
(purely narrative and 'factual') which is most interesting, along with
some
SGII/DSII relevant things to say about infantry combat in the age of
mobile
sentry guns, smart mines, laser rifles etc etc...

TTFN
Jon
----------------------------------------------
"Reality never lives up to all that it used to be.."
Beth Orton 'Best bit'
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