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Natural Science Forum / Physics / Research / July 2008Gamma Ray Gun
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?  SignatureDirk http://www.transcendence.me.uk/ - Transcendence UK Remote Viewing classes in London > I once did a calculation for a NG, sci.military.moderated IIRC, > concerning the lethality of the hypothetical weapon given a beam pulse [quoted text clipped - 4 lines] > 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. SignatureUncle Al http://www.mazepath.com/uncleal/ (Toxic URL! Unsafe for children and most mammals) http://www.mazepath.com/uncleal/lajos.htm#a2 >> I once did a calculation for a NG, sci.military.moderated IIRC, >> concerning the lethality of the hypothetical weapon given a beam pulse [quoted text clipped - 11 lines] > 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. SignatureDirk http://www.transcendence.me.uk/ - Transcendence UK Remote Viewing classes in London On Jul 16, 6:52 am, Dirk Bruere at NeoPax <dirk.bru...@gmail.com> wrote: > >> I once did a calculation for a NG, sci.military.moderated IIRC, > >> concerning the lethality of the hypothetical weapon given a beam pulse [quoted text clipped - 18 lines] > 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 > On Jul 16, 6:52 am, Dirk Bruere at NeoPax <dirk.bru...@gmail.com> > wrote: [quoted text clipped - 18 lines] > > 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). SignatureDirk http://www.transcendence.me.uk/ - Transcendence UK Remote Viewing classes in London On Jul 18, 4:07 am, "n...@bid.nes" <Alien8...@gmail.com> wrote: > On Jul 16, 6:52 am, Dirk Bruere at NeoPax <dirk.bru...@gmail.com> > wrote: [quoted text clipped - 23 lines] > > 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 > On Jul 18, 4:07 am, "n...@bid.nes" <Alien8...@gmail.com> wrote: >> On Jul 16, 6:52 am, Dirk Bruere at NeoPax <dirk.bru...@gmail.com> [quoted text clipped - 37 lines] > 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)? SignatureDirk http://www.transcendence.me.uk/ - Transcendence UK Remote Viewing classes in London >> On Jul 18, 4:07 am, "n...@bid.nes" <Alien8...@gmail.com> wrote: >>> On Jul 16, 6:52 am, Dirk Bruere at NeoPax <dirk.bru...@gmail.com> [quoted text clipped - 45 lines] > 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 SignatureDirk 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 >> I once did a calculation for a NG, sci.military.moderated IIRC, >> concerning the lethality of the hypothetical weapon given a beam pulse [quoted text clipped - 11 lines] > 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 |
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