I once did a calculation for a NG, sci.military.moderated IIRC,
concerning the lethality of the hypothetical weapon given a beam pulse
energy comparable to the muzzle energy of a conventional handgun (about
700J).

The question I could not answer concerned its effect on the user of the
weapon. Would there be enough back scatter from the air at the muzzle
and along the beam path to seriously endanger the health of the firer?

--
Dirk

http://www.transcendence.me.uk/ - Transcendence UK
Remote Viewing classes in London

Dirk Bruere at NeoPax wrote:

I once did a calculation for a NG, sci.military.moderated IIRC,
concerning the lethality of the hypothetical weapon given a beam pulse
energy comparable to the muzzle energy of a conventional handgun (about
700J).

The question I could not answer concerned its effect on the user of the
weapon. Would there be enough back scatter from the air at the muzzle
and along the beam path to seriously endanger the health of the firer?

How short is the pulse?

An M16A2 rifle has a muzzle velocity of 2800 ft/sec. The bullet
travels one foot in 0.3571 msec. 700 J in 0.3571 msec is 1.96 MW. The
air would massively ionize. Worry about thermal and UV burns, then
soft x-ray backscatter.

--
Uncle Al
http://www.mazepath.com/uncleal/
(Toxic URL! Unsafe for children and most mammals)
http://www.mazepath.com/uncleal/lajos.htm#a2

Uncle Al wrote:
Dirk Bruere at NeoPax wrote:
I once did a calculation for a NG, sci.military.moderated IIRC,
concerning the lethality of the hypothetical weapon given a beam pulse
energy comparable to the muzzle energy of a conventional handgun (about
700J).

The question I could not answer concerned its effect on the user of the
weapon. Would there be enough back scatter from the air at the muzzle
and along the beam path to seriously endanger the health of the firer?

How short is the pulse?

An M16A2 rifle has a muzzle velocity of 2800 ft/sec. The bullet
travels one foot in 0.3571 msec. 700 J in 0.3571 msec is 1.96 MW. The
air would massively ionize. Worry about thermal and UV burns, then
soft x-ray backscatter.

Since we were talking handguns the velocity would be around 1/3 of that
if we stuck to the analogy. However, since we do not have to worry too
much about beam drop (as opposed to bullet drop) the real time to
consider is time on target. Since I doubt anyone could dodge such a beam
lasting 10mS, we now have a power of 70kW. For simplicity we can assume
a beam diameter of 10mm.

--
Dirk

http://www.transcendence.me.uk/ - Transcendence UK
Remote Viewing classes in London

Uncle Al wrote:
Dirk Bruere at NeoPax wrote:

I once did a calculation for a NG, sci.military.moderated IIRC,
concerning the lethality of the hypothetical weapon given a beam pulse
energy comparable to the muzzle energy of a conventional handgun (about
700J).

The question I could not answer concerned its effect on the user of the
weapon. Would there be enough back scatter from the air at the muzzle
and along the beam path to seriously endanger the health of the firer?

How short is the pulse?

An M16A2 rifle has a muzzle velocity of 2800 ft/sec. The bullet
travels one foot in 0.3571 msec. 700 J in 0.3571 msec is 1.96 MW. The
air would massively ionize. Worry about thermal and UV burns, then
soft x-ray backscatter.

I don't understand this estimate. It assumes the 700J energy of the
bullet is entirely expended in the first foot of air after leaving the
muzzle, after which the bullet would presumably drop to the ground. In
that unrealistic case maybe the 2 MW pulse would "massively ionize" that
foot of air. The beam of a GRG would also, presumably, not lose all its
energy in one foot of air. How does your estimate relate to the original
question?

- Dushan Mitrovich

On Jul 16, 6:52 am, Dirk Bruere at NeoPax
wrote:
Uncle Al wrote:
Dirk Bruere at NeoPax wrote:
I once did a calculation for a NG, sci.military.moderated IIRC,
concerning the lethality of the hypothetical weapon given a beam pulse
energy comparable to the muzzle energy of a conventional handgun (about
700J).

The question I could not answer concerned its effect on the user of the
weapon. Would there be enough back scatter from the air at the muzzle
and along the beam path to seriously endanger the health of the firer?

How short is the pulse?

An M16A2 rifle has a muzzle velocity of 2800 ft/sec. The bullet
travels one foot in 0.3571 msec. 700 J in 0.3571 msec is 1.96 MW. The
air would massively ionize. Worry about thermal and UV burns, then
soft x-ray backscatter.

Since we were talking handguns the velocity would be around 1/3 of that
if we stuck to the analogy. However, since we do not have to worry too
much about beam drop (as opposed to bullet drop) the real time to
consider is time on target. Since I doubt anyone could dodge such a beam
lasting 10mS, we now have a power of 70kW. For simplicity we can assume
a beam diameter of 10mm.

70 kW of what, photons? If so, what wavelength(s)?

Mark L. Fergerson

wrote:
On Jul 16, 6:52 am, Dirk Bruere at NeoPax
wrote:
Uncle Al wrote:
Dirk Bruere at NeoPax wrote:
I once did a calculation for a NG, sci.military.moderated IIRC,
concerning the lethality of the hypothetical weapon given a beam pulse
energy comparable to the muzzle energy of a conventional handgun (about
700J).
The question I could not answer concerned its effect on the user of the
weapon. Would there be enough back scatter from the air at the muzzle
and along the beam path to seriously endanger the health of the firer?
How short is the pulse?
An M16A2 rifle has a muzzle velocity of 2800 ft/sec. The bullet
travels one foot in 0.3571 msec. 700 J in 0.3571 msec is 1.96 MW. The
air would massively ionize. Worry about thermal and UV burns, then
soft x-ray backscatter.
Since we were talking handguns the velocity would be around 1/3 of that
if we stuck to the analogy. However, since we do not have to worry too
much about beam drop (as opposed to bullet drop) the real time to
consider is time on target. Since I doubt anyone could dodge such a beam
lasting 10mS, we now have a power of 70kW. For simplicity we can assume
a beam diameter of 10mm.

70 kW of what, photons? If so, what wavelength(s)?

Well, for argument's sake let's say 500keV since that gives a reasonable
range of some 60m in air before beam energy halves (at least in the low
power case).

--
Dirk

http://www.transcendence.me.uk/ - Transcendence UK
Remote Viewing classes in London

On Jul 18, 4:07 am, " wrote:
On Jul 16, 6:52 am, Dirk Bruere at NeoPax
wrote:

Uncle Al wrote:
Dirk Bruere at NeoPax wrote:
I once did a calculation for a NG, sci.military.moderated IIRC,
concerning the lethality of the hypothetical weapon given a beam pulse
energy comparable to the muzzle energy of a conventional handgun (about
700J).

The question I could not answer concerned its effect on the user of the
weapon. Would there be enough back scatter from the air at the muzzle
and along the beam path to seriously endanger the health of the firer?

How short is the pulse?

An M16A2 rifle has a muzzle velocity of 2800 ft/sec. The bullet
travels one foot in 0.3571 msec. 700 J in 0.3571 msec is 1.96 MW. The
air would massively ionize. Worry about thermal and UV burns, then
soft x-ray backscatter.

Since we were talking handguns the velocity would be around 1/3 of that
if we stuck to the analogy. However, since we do not have to worry too
much about beam drop (as opposed to bullet drop) the real time to
consider is time on target. Since I doubt anyone could dodge such a beam
lasting 10mS, we now have a power of 70kW. For simplicity we can assume
a beam diameter of 10mm.

70 kW of what, photons? If so, what wavelength(s)?

Sorry, "senior moment"; title of thread = "Gamma Ray Gun". Anyway,
apparently gammas are very easily absorbed by air. Perhaps "absorbed"
isn't exactly appropriate, considering there are gamma-ray
observatories being built on Earth's surface that don't actually look
for gammas but rather the particle showers resulting from what happens
when incoming gammas strike air.

So, having lowered the pulse intensity below the threshold of
"ionize the air in front of the muzzle into a lethal mirror", you have
your pulse of prompt gammas pretty much converted to lower-energy
photons and fast-moving electrons, muons, and who knows what other
charged particles within a very short distance.

Perhaps you could think about some sort of "afterburner"
electrostatic muzzle add-on that would encourage the charged particles
to emit their contribution to the final beam in the general direction
of the target rather than back at the wielder?

Mark L. Fergerson

wrote:
On Jul 18, 4:07 am, " wrote:
On Jul 16, 6:52 am, Dirk Bruere at NeoPax
wrote:

Uncle Al wrote:
Dirk Bruere at NeoPax wrote:
I once did a calculation for a NG, sci.military.moderated IIRC,
concerning the lethality of the hypothetical weapon given a beam pulse
energy comparable to the muzzle energy of a conventional handgun (about
700J).
The question I could not answer concerned its effect on the user of the
weapon. Would there be enough back scatter from the air at the muzzle
and along the beam path to seriously endanger the health of the firer?
How short is the pulse?
An M16A2 rifle has a muzzle velocity of 2800 ft/sec. The bullet
travels one foot in 0.3571 msec. 700 J in 0.3571 msec is 1.96 MW. The
air would massively ionize. Worry about thermal and UV burns, then
soft x-ray backscatter.
Since we were talking handguns the velocity would be around 1/3 of that
if we stuck to the analogy. However, since we do not have to worry too
much about beam drop (as opposed to bullet drop) the real time to
consider is time on target. Since I doubt anyone could dodge such a beam
lasting 10mS, we now have a power of 70kW. For simplicity we can assume
a beam diameter of 10mm.
70 kW of what, photons? If so, what wavelength(s)?

Sorry, "senior moment"; title of thread = "Gamma Ray Gun". Anyway,
apparently gammas are very easily absorbed by air. Perhaps "absorbed"
isn't exactly appropriate, considering there are gamma-ray
observatories being built on Earth's surface that don't actually look
for gammas but rather the particle showers resulting from what happens
when incoming gammas strike air.

So, having lowered the pulse intensity below the threshold of
"ionize the air in front of the muzzle into a lethal mirror", you have
your pulse of prompt gammas pretty much converted to lower-energy
photons and fast-moving electrons, muons, and who knows what other
charged particles within a very short distance.

Perhaps you could think about some sort of "afterburner"
electrostatic muzzle add-on that would encourage the charged particles
to emit their contribution to the final beam in the general direction
of the target rather than back at the wielder?

The absorption of 500keV gammas allows a half intensity beam to arrive
on target at ranges getting on for 100m. How much air ionisation from a
70kW/sq cm is another question. I imagine the beam would be pretty
visible. It is also doubtful that ionised air would stop the gammas any
better than un-ionised.

So let's return to the original question - how much back scatter
(through 180 degrees)?

--
Dirk

http://www.transcendence.me.uk/ - Transcendence UK
Remote Viewing classes in London

Dirk Bruere at NeoPax wrote:
wrote:
On Jul 18, 4:07 am, " wrote:
On Jul 16, 6:52 am, Dirk Bruere at NeoPax
wrote:

Uncle Al wrote:
Dirk Bruere at NeoPax wrote:
I once did a calculation for a NG, sci.military.moderated IIRC,
concerning the lethality of the hypothetical weapon given a beam pulse
energy comparable to the muzzle energy of a conventional handgun (about
700J).
The question I could not answer concerned its effect on the user of the
weapon. Would there be enough back scatter from the air at the muzzle
and along the beam path to seriously endanger the health of the firer?
How short is the pulse?
An M16A2 rifle has a muzzle velocity of 2800 ft/sec. The bullet
travels one foot in 0.3571 msec. 700 J in 0.3571 msec is 1.96 MW. The
air would massively ionize. Worry about thermal and UV burns, then
soft x-ray backscatter.
Since we were talking handguns the velocity would be around 1/3 of that
if we stuck to the analogy. However, since we do not have to worry too
much about beam drop (as opposed to bullet drop) the real time to
consider is time on target. Since I doubt anyone could dodge such a beam
lasting 10mS, we now have a power of 70kW. For simplicity we can assume
a beam diameter of 10mm.
70 kW of what, photons? If so, what wavelength(s)?
Sorry, "senior moment"; title of thread = "Gamma Ray Gun". Anyway,
apparently gammas are very easily absorbed by air. Perhaps "absorbed"
isn't exactly appropriate, considering there are gamma-ray
observatories being built on Earth's surface that don't actually look
for gammas but rather the particle showers resulting from what happens
when incoming gammas strike air.

So, having lowered the pulse intensity below the threshold of
"ionize the air in front of the muzzle into a lethal mirror", you have
your pulse of prompt gammas pretty much converted to lower-energy
photons and fast-moving electrons, muons, and who knows what other
charged particles within a very short distance.

Perhaps you could think about some sort of "afterburner"
electrostatic muzzle add-on that would encourage the charged particles
to emit their contribution to the final beam in the general direction
of the target rather than back at the wielder?

The absorption of 500keV gammas allows a half intensity beam to arrive
on target at ranges getting on for 100m. How much air ionisation from a
70kW/sq cm is another question. I imagine the beam would be pretty
visible. It is also doubtful that ionised air would stop the gammas any
better than un-ionised.

So let's return to the original question - how much back scatter
(through 180 degrees)?

Partially answering a previous post: if 350J were dissipated in a column
of air 100m long by 1cm diameter (say 1cm^2) we have a volume of 10L
Mass at STP = 10/22.4 x 36 = 16g
Specific heat of air approx 1 degK/J/g
Hence we would expect a temp rise of approx 350/16 = 20 degK

Of course, the beam would not dissipate energy linearly with length but
the above figures give some ballpark estimates.

Hardly a super radiant plasma

--
Dirk

http://www.transcendence.me.uk/ - Transcendence UK
http://www.theconsensus.org/ - A UK political party
http://www.onetribe.me.uk/wordpress/?cat=5 - Our podcasts on weird stuff