SG says snipers sometimes carry laser weapons. However, I recall a
discussion in which it was said the x-ray lasers so beloved of my
Traveller
characters would hardly be silent/invisible--more like a lightning bolt.
Don't know whether that was accurate, though.
So, questions for you educated blokes:
a. would/could a military laser weapon be invisible/inaudible? Or would
it be useless to snipers due to signature? (assumes a standard Earth
atmosphere with no unusual components) b. in a zero gee environment, would
lasers have *no* recoil? This doesn't seem logical because we've talked about
a lasers as a ship drive, so there has to be some recoil....but how much?
Either as compared to a rifle, or in
> On Mon, Sep 17, 2001 at 03:09:15PM -0400, Chris DeBoe wrote:
An infra-red laser wouldn't necessarily leave an obvious trail; that's
about all I can think of.
> b. in a zero gee environment, would lasers have *no* recoil? This
Trivial. A laser-drive uses _huge_ amounts of energy.
> At 3:09 PM -0400 9/17/01, Chris DeBoe wrote:
Doesn't have to be visible light. It could be Infrared. X-ray lasers
I think would be silent however...
> So, questions for you educated blokes:
It should be nearly inaudible. Visible to the right sensors though.
> b. in a zero gee environment, would lasers have *no* recoil? This
Why not? Laser drives lase a specific material exciting it to a higher state
and expending mass to a degree I think....
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> On Mon, 17 Sep 2001, Chris DeBoe wrote:
> SG says snipers sometimes carry laser weapons. However, I recall a
I think this would depend on what you'd try to accomplish. Blinding someone
would be as much of a 'mission kill' as anyuthing else, and this is certainly
feasible without the above mentioned effects.
> b. in a zero gee environment, would lasers have *no* recoil? This
Mmmm. Good one, need to think on it.
Cheers,
> >So, questions for you educated blokes:
Does this depend on how much energy you're putting on the target? (with the
implied question: how much is enough?)
> >b. in a zero gee environment, would lasers have *no* recoil? This
To move a thousand ton ship, yes. I'm only talking about moving a 100kg
> On Mon, Sep 17, 2001 at 03:57:59PM -0400, Chris DeBoe wrote:
that's
> about all I can think of.
I suspect so. I don't have that information, alas.
> Trivial. A laser-drive uses _huge_ amounts of energy.
OK. How much damage does a man-portable laser need to do? An M60 machine
gun firing 7.62NATO (about 3kJ/round) at 100 RPM (recommended cyclic
rate) gives a sustained energy transfer of about 5kW. Let's be generous and
scale that up by ten, to burn through armour and so on; 50kW it is, for a
fairly hefty laser support weapon.
Momentum of a photon = E/c where E is its energy and c is the speed of
light. A 50kW beam gives about 167 microNewton - which will accelerate
the 100kg trooper at 1.67 micrometres per second per second. After nine days
of continuous fire he'll be moving at walking pace.
(For comparison - the M60 fires a 10g round at about 770m/s. Momentum
per round = 7.7 Ns for a force of 13 Newton on full-auto.)
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> On Mon, 17 Sep 2001, Ryan M Gill wrote:
> At 3:09 PM -0400 9/17/01, Chris DeBoe wrote:
Yes/no. It's not the wavelength, it's the enrgy concentration. Enough
energy density (energy going through a small volume of air) will ionise the
air, resulting in a (loud & visible) electric discharge.
> >So, questions for you educated blokes:
See above. But for blinding, a much lower energy density is required.
> >b. in a zero gee environment, would lasers have *no* recoil? This
I'd have to check, but I as far as I recall atoms get excited to a higher
levbel and fall back with the emission of a photon. Dimensions of the
lasing cavity dictate an in-phase monochromatic light. I do not recall
any loss of mass.
Cheers,
G'day guys,
I know zip about weapon grade lasers, but...
> Doesn't have to be visible light. It
If at sufficient strength (don't know if weapon grade would be that by the
way), wouldn't it ionise the atmosphere and thus produce a sonic boom? Good
for the first shot, bad for any subsequent ones as they'd know where the
sniper was.
Cheers
> Beth.Fulton@marine.csiro.au wrote:
> G'day guys,
Good
> for the first shot, bad for any subsequent ones as they'd know where
Now you've done it! I now realize that I may have the education to look up the
True. But it would ionize it all the way to the target. Thus the sonic boom
would not be as localized as a gun shot. However, if there were the
accompaning electrical discharge (lightning), it could show almost exactly
where the sniper is.
On the other hand the film I saw (several years ago) of an high energy laser
hitting a target did NOT leave a visible trail (spectrum was above visible). I
could not tell if there was any associated sound because the target exploded
as the metal was superheated.
---
Brian Bell bbell1@insight.rr.com ICQ: 12848051 AIM: Rlyehable YIM: Rlyehable
The Full Thrust Ship Registry:
http://www.ftsr.org
---
[quoted original message omitted]
> At 9:18 PM -0400 9/17/01, Brian Bell wrote:
Achaa. Good point. There isn't the Bang/Crack sound of the rifle.
Just the Crack of the laser. And it's going past you but you just can't tell
from where and along where. Just that it passed near you.
> On the other hand the film I saw (several years ago) of an high energy
I'd suspect that the thermal effects of the target would be as nearly
instantaneous as that of the air/thermal effects, or close enough
that it'd not be detectable by the Mk 1 Ear. Use of far better gear (EW
trooper) would be needed.
[quoted original message omitted]
> Laserlight wrote:
> SG says snipers sometimes carry laser weapons. However, I recall a
Referring to the previous posts it could be invisible to the Mk.1 eyeball,
depending on wavelength and energy density. IR vision gear is another
question entirely though - when today's best IR sights can detect the
thermal output from a low-powered radio antenna, I wouldn't be surprised
if tomorrow's IR goggles could detect the "trail" of a laser rifle.
As for using laser weapons to blind the enemy trooper, well... unless
you're fighting a low-tech enemy or you catch him bareheaded, you won't
get
a clear LOS to his unprotected eyes.Burning out/through visors or sights
ups the amount of energy necessary to disable the target considerably, and if
the visor or sight is all that burns out, well... that's quite a bit
easier to replace than an eye :-/
Later,
Chris
> SG says snipers sometimes carry laser weapons. However, I recall a
I'm doing my degree if that counts!
> a. would/could a military laser weapon be invisible/inaudible? Or
Um, the noise would be a question of the gun itself, rather than the passage
of the laser beam, the lightning bolt effect could possibly be to do with the
beam being cut off, and the vacuum (and particularly the lack of heat) creatde
by it, causing thunder in the same way as lightning causes it, BUT this could
be easily avoided by using either pulse lasers (which can deliver more energy
anyway) or by fading the beam away rather than cutting it off.
> b. in a zero gee environment, would lasers have *no* recoil? This
Photon's are very tiny particles that behave like waves, (or the other way
round, its complicated). Some A-level quantum physics:
The de Broglie wavelenght is expressed as planks constant/its momentum
(aha I here you cry if it has momentum then it must have mass, resulting in
recoil...) But: Plank's constant is REALLY Small
(0.00000000000000000000000000000000002, or around that) and so the momentum is
Really small too, since the velocity is pretty big (the speed of light) this
means that the mass must be very very
small:(0.000000000000000000000000000000000000000000000000000000000000000 01
Kg) so yes there is SOME recoil, but barely noticable (like the recoil when
you speak), so I'm not sure how you would use light as a drive for a space
ship.
Hope that helps
> On 21-Sep-01 at 08:59, Richard Kirke (richardkirke@hotmail.com) wrote:
> The de Broglie wavelenght is expressed as planks constant/its momentum
small:(0.000000000000000000000000000000000000000000000000000000000000000 01
> Kg) so yes there is SOME recoil, but barely noticable (like the recoil
I had a physicist friend that made a SF RPG. Initially he was going to use a
laser drive, that is until he figured out that at 1G acceleration you could
kill a planet with the thing.
***
I had a physicist friend that made a SF RPG. Initially he was going to use a
laser drive, that is until he figured out that at 1G acceleration you could
kill a planet with the thing.
***
I thought that was the idea; chem and/or nuclear drive for significant
fractions of 1G, light drive for 0.00000000000... G, for STL interstellar.
Very low thrust, but next to no reaction mass, and very efficient over the
very long haul.
> On Fri, 21 Sep 2001 08:14:55 -0500, devans@uneb.edu wrote:
> I thought that was the idea; chem and/or nuclear drive for significant
That's what I remember. Basically it involved pushing something like a probe.
You didn't move it very fast, but it was constant acceleration. Eventually it
would be moving at a pretty good clip. It also meant you didn't have to take
your fuel with you, which made the payload even smaller.