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  #1  
Old 08-29-2013, 09:37 PM
Habeed Habeed is offline
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Are hand-held high energy weapons possible via known physics?

The reason this is in general questions and not IMHO is it is a factual question based on current accepted knowledge.

Conditions : You have the technology to arrange matter in any arbitrary configuration that is stable. Could you build a "hand held" energy source in a weapon that produced, say, 100 kilowatts of continuous electric power, and could fire until the waste heat made it too hot to handle?

By "hand held", it has to be smaller than about 20cmx20cmx20cm, and weigh less than 10 kilograms. Also, it can't emit fatal (to a human today) amounts of gamma rays.

Chemical energy sources won't do it, and the problem with all the nuclear reactions I know about is that

1. To create a chain reaction, you need a critical mass. That means several kilograms of high purity fissionable material at a minimum, and the real problem is that the neutrons released by a chain reaction can't be stopped by anything other than a lot of material, far more than 10 kg worth.

2. Nuclear batteries that don't involve chain reactions can't be throttled. Short half life Americium that emited beta particles might work, but there would be know way to turn it off.


Am I missing anything?

I've read about a theoretical nanoscale battery that stored energy in electron spin and if you could build trillions of complex molecular subunits to make such a battery, it would be practical.
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  #2  
Old 08-29-2013, 09:39 PM
Johnny L.A. Johnny L.A. is offline
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Kinetic energy weapons are quite common.
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  #3  
Old 08-29-2013, 09:44 PM
Chronos Chronos is offline
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Critical mass isn't (in principle) a problem, either. The critical mass of uranium or plutonium is several kilograms at low pressure, but you can decrease that either by compressing it, or by using a different isotope. With a more active isotope like americium, you can get a critical mass from a few grams.
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Old 08-29-2013, 09:58 PM
Trinopus Trinopus is offline
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To cheat just a little, you could have "beamed power." The real power supply is in a big building in Omaha, but it gets beamed to your hand-weapon, which then uses it to produce a zap ray.

Otherwise...matter/antimatter power cells. That's pretty much the upper limit on energy storage. Twelve ounces of matter, twelve ounces of antimatter, unite the two judiciously, and you've got a blortload of energy to use.
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  #5  
Old 08-29-2013, 10:08 PM
lisiate lisiate is offline
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Energy density is the big limiting factor. Your 10-kilo weight limit means even if it's all devoted to batteries you'll only have 18 Megajoules of energy total - about the same energy as a cup and a half of petrol. Which can power your 100 kilowatt energy weapon for about 1.7 seconds I think.
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  #6  
Old 08-29-2013, 10:12 PM
Terr Terr is offline
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Originally Posted by lisiate View Post
Energy density is the big limiting factor. Your 10-kilo weight limit means even if it's all devoted to batteries you'll only have 18 Megajoules of energy total - about the same energy as a cup and a half of petrol. Which can power your 100 kilowatt energy weapon for about 1.7 seconds I think.
See matter/antimatter thing upthread. Containment, though, is a bitch.
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  #7  
Old 08-29-2013, 10:32 PM
Mister Rik Mister Rik is offline
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So, basically, a handheld, 1920s-style death ray?
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  #8  
Old 08-30-2013, 11:38 AM
Habeed Habeed is offline
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Antimatter doesn't count. An electron-positron pair annihilation releases 511 KeV gamma rays - see the listed constraints.
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  #9  
Old 08-30-2013, 04:17 PM
Trinopus Trinopus is offline
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So shield the gamma rays and use the other energy to power your laser. Antimatter/matter is still the absolute limit on energy density. Nothing can possibly ever be better. We've driven a surveyor's stake into the ground, establishing the absolute upper end of weapons efficiency.

Because of the need for containment, shielding, etc., the real "best possible" weapon will be somewhere below the position of that end-point.

You invoked the "known rules of physics" but then immediately violated them by allowing us to arrange matter in "any arbitrary configuration that is stable." This means we're working with speculative future technology which we cannot, now, predict.

BTW, why exclude gamma rays? They could make a fairly effective weapon. Would you want to stand in front of someone's gamma ray gun? (No, not you, Dr. Banner. We know your opinion.)
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  #10  
Old 08-30-2013, 04:19 PM
Habeed Habeed is offline
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You can't shield the gamma rays - 10 kg weight limit.

It requires known physics - by "any configuration that is stable", I meant you can state "carbon nanotube batteries" or some other exotic material we know exists but cannot make in quantity.

We do have to know about it, today, or it isn't valid. I'm trying to ask if someone could design a ray gun using a CAD system today, and have a reasonable confidence it would work, even if they could not manufacture it.

Last edited by Habeed; 08-30-2013 at 04:21 PM..
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  #11  
Old 08-30-2013, 04:28 PM
gnoitall gnoitall is offline
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Originally Posted by Trinopus View Post
So shield the gamma rays and use the other energy to power your laser. Antimatter/matter is still the absolute limit on energy density. Nothing can possibly ever be better. We've driven a surveyor's stake into the ground, establishing the absolute upper end of weapons efficiency.

Because of the need for containment, shielding, etc., the real "best possible" weapon will be somewhere below the position of that end-point.

You invoked the "known rules of physics" but then immediately violated them by allowing us to arrange matter in "any arbitrary configuration that is stable." This means we're working with speculative future technology which we cannot, now, predict.

BTW, why exclude gamma rays? They could make a fairly effective weapon. Would you want to stand in front of someone's gamma ray gun? (No, not you, Dr. Banner. We know your opinion.)
Well, most gamma ray sources are effectively omnidirectional. So they're more dangerous to the person holding the gun than the target (thanks to the inverse square rule).

And you don't have enough in your 10kg weight limit allowance to meaningfully shield a decent gamma source so that the death rays only come out in the intended direction.
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  #12  
Old 08-30-2013, 06:11 PM
Do Not Taunt Do Not Taunt is online now
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Originally Posted by lisiate View Post
Energy density is the big limiting factor. Your 10-kilo weight limit means even if it's all devoted to batteries you'll only have 18 Megajoules of energy total - about the same energy as a cup and a half of petrol. Which can power your 100 kilowatt energy weapon for about 1.7 seconds I think.
18 Megajoules is 18 million joules. 100 kilowatts is 100 thousand joules per second. So my division gives you 180 seconds, or 3 minutes, assuming no waste.
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  #13  
Old 08-30-2013, 08:50 PM
Lumpy Lumpy is offline
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The Atomic Rockets site has a page devoted entirely to the pros and cons of energy sidearms. It addresses several problems with the concept. Energy density of power source, waste heat, and especially the problem that any electromagnetic beam (laser, etc.) powerful enough to burn a hole through its target is going to backscatter enough energy to maim or kill the gun wielder.
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  #14  
Old 08-30-2013, 09:58 PM
Xema Xema is offline
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Originally Posted by Mister Rik View Post
So, basically, a handheld, 1920s-style death ray?
They didn't go hand-held until the early thirties.
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  #15  
Old 08-31-2013, 12:36 AM
dropzone dropzone is offline
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Originally Posted by Johnny L.A. View Post
Kinetic energy weapons are quite common.
And this is why the gunpowder-based handguns in Firefly make much more sense than phasers and blasters. Handheld energy weapons are a fun intellectual exercise and I don't want to derail the thread. I mean, it's brainstorming and there are no bad ideas in a brainstorming session.

However, Arte Johnson and Peter Sellers say it best.
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  #16  
Old 08-31-2013, 01:31 AM
scr4 scr4 is offline
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Originally Posted by Habeed View Post
Could you build a "hand held" energy source in a weapon that produced, say, 100 kilowatts of continuous electric power, and could fire until the waste heat made it too hot to handle?
...
Chemical energy sources won't do it...
Why are you dismissing chemical energy? 10 kilograms of gasoline contains about 460 MJ of energy. That's 100 kilowatt x 4600 seconds. If you can get the total efficiency to 1%, you have 46 seconds of use, which seems sufficient for a hand-held weapon.
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  #17  
Old 08-31-2013, 12:39 PM
Habeed Habeed is offline
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Why are you dismissing chemical energy? 10 kilograms of gasoline contains about 460 MJ of energy. That's 100 kilowatt x 4600 seconds. If you can get the total efficiency to 1%, you have 46 seconds of use, which seems sufficient for a hand-held weapon.
That fails to meet the stated constraint of "could fire indefinitely, limited by waste heat".

Weaponry like this is a sci-fi trope. In order for it to work, a form of nuclear energy that does not release gamma rays is probably the only valid solution.
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  #18  
Old 08-31-2013, 01:53 PM
scr4 scr4 is offline
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Originally Posted by Habeed View Post
That fails to meet the stated constraint of "could fire indefinitely, limited by waste heat".
You only said "fire until the waste heat made it too hot to handle," which is very different from "indefinitely". I took it to mean the weapon overheats before the energy source runs out.

Quote:
Weaponry like this is a sci-fi trope. In order for it to work, a form of nuclear energy that does not release gamma rays is probably the only valid solution.
I don't recall any sci-fi weapons having an unlimited power source. Star Trek phasers had power cells that needed to be recharged, for example.
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  #19  
Old 08-31-2013, 01:57 PM
Chronos Chronos is offline
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And gamma rays are a feature, not a bug. You just need to figure out a way to make them only come out the front, not the sides.
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  #20  
Old 08-31-2013, 03:36 PM
dstarfire dstarfire is offline
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So, atomics radiation is out (spiralling into debate of issues irrelevant to this scenario).

But what about the old "nuke in a tube" sci-fi trope?

Also, what about lasers? I know the Navy has shot down a target drone with a laser.

How about microwaves? The Army has a crowd suppression system that uses specially tuned microwaves to create a sunburn-like sensation. Could you tune it instead to boil a person's tissues while still meeting the OP's requirements?
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  #21  
Old 08-31-2013, 03:36 PM
aNewLeaf aNewLeaf is offline
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Well, matter conversion technology takes care of the directionality.
You can convert a fraction of a gram of of matter into many, many ergs (E=MC^2).
Trick is to arrange it so the energy comes out all more or less in the same direction.
Think of laser light, or perhaps a magnetron tube, as an analogy. Directed energy output at nearly 100% efficiency.
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  #22  
Old 08-31-2013, 10:10 PM
Habeed Habeed is offline
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Obviously matter -> energy conversion is the only way to meet the constraints. But how. Antimatter releases extremely high energy gamma rays in all directions. Most nuclear reactions release neutrons and gamma rays, and need a critical mass.

Off hand, the only way I can think of that might meet the constraints is aneutronic fusion. This is a series of fusion reactions that release charged particles only, that can be converted directly to energy.

http://en.wikipedia.org/wiki/Aneutronic_fusion


Of course, the proposed fusion reactors that do this are huge..but maybe, just maybe, the conditions necessary to make fusion work could be done at the nanoscale.
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  #23  
Old 09-01-2013, 04:46 AM
eburacum45 eburacum45 is online now
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Cold fusion or sonofusion would be nice, if these were real things.

How about a flywheel gun? Might be a bit tricky to aim, because of gyroscopic effects, but a diamond flywheel could have as much energy density as the same weight of kerosine - good for a few shots.

Maybe if your gun has lots of little flywheels, all pointing in different directions.

Last edited by eburacum45; 09-01-2013 at 04:49 AM..
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  #24  
Old 09-02-2013, 12:16 AM
Pasta Pasta is offline
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Quote:
Originally Posted by Habeed View Post
...100 kilowatts of continuous electric power, and could fire until the waste heat made it too hot to handle?
Quote:
Originally Posted by Habeed
...could fire indefinitely, limited by waste heat
Can you clarify your constraint? I still don't see why chemical sources are out by these conditions. It sounds like you are defining "indefinitely" as "as long as it isn't too hot". Why can't a chemical energy weapon fire just as well as anything else until it gets too hot? Do you mean something different by "indefinitely"?
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  #25  
Old 09-07-2013, 07:15 PM
Habeed Habeed is offline
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Originally Posted by Pasta View Post
Can you clarify your constraint? I still don't see why chemical sources are out by these conditions. It sounds like you are defining "indefinitely" as "as long as it isn't too hot". Why can't a chemical energy weapon fire just as well as anything else until it gets too hot? Do you mean something different by "indefinitely"?
I mean you could fire the weapon for weeks on end if you could dispose of the waste heat. Aka the only power source that can work has to involve conversion of matter to energy.

I used the word "indefinite" to mean that no combat situation you could ever plausibly get involved in would drain the power source.

Think those "infinite ammo" blasters they have in video games, or the power source on a lightsaber, etc.

Last edited by Habeed; 09-07-2013 at 07:17 PM..
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  #26  
Old 09-07-2013, 07:50 PM
aNewLeaf aNewLeaf is offline
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Well, I can't operate it for days. But I've got a straight sword I could use for hours and still manage the waste heat.
The weapon allows killing at a distance, rapid redeployment rate, reliability of design, and to some extent, the use of a backup hand.

So really, any sort of storage device needs to start there, matching or exceeding a human. Then we can worry about matter conversion.
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  #27  
Old 09-07-2013, 08:55 PM
kanicbird kanicbird is offline
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It would seem very likely. Chemical energy in gun powder is converted in to lethal kinetic energy but transferring that to bullets. Tazers are currently designed to be less then lethal, but can they be made to be lethal?

The problem does not seem to be the energy source, but the method of delivery. If the energy can be delivered efficiently on target it seems very possible.
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