Sci-Fi weapons

Factual Questions
#1

Not sure if GQ is the right place for this one, but wanted to ask some questions about some old favorite Sci-Fi type weapons, what exactly they are, and what, if any, reality underlies them.

The first weapons I see a lot of is a plasma rifle/cannon. What exactly is it? I understand what plasma is, but how would you go about using it as a projectile type weapon, i.e. how would you ‘fire’ plasma at a target? What would it take to create a man portable plasma weapon? What would it (theoretically) use as fuel (I’ve seen hydrogen used in books)? What would its (theoretical) energy requirements be?

The next weapon is the rail gun. I remember in my college physics class talking about rail guns WRT then president Reagans Star Wars program (my physics prof was involve in some research program related to SW). But how practical is such a weapon? What would it take to make a rail gun that was man portable? What kind of ammo could or would (theoretically) be used? What would its energy requirements (again, theoretically) be?

The old standby…the laser rifle/cannon. Would this be a practical military weapon? What would it take to make a man portable version? What would its energy requirements be?

From Honor Harrington, what exactly is a grazer…and how would it theoretically work? What does it fire, and what kind of power requirements would it have? Also from HH, how practical and how would an X-Ray (bomb pumped) laser work?

How about the old fashion light sabre. How could such a weapon work (how would it repel another light blade for instance)? Would it be a plasma, a laser…something else? Again, I realize its Sci-Fi but is there anything in science that could underpin the concept?

Mods, if this would work better in IMHO or another forum (because there are no factual answers I suppose) feel free to move it there.

-XT

#2

Rail gun page on Wiki: http://en.wikipedia.org/wiki/Electromagnetic_gun
Laser rifle (though designed to blind not kill): http://extremephoton.com/article/Air+Force+Develops+a+Phaser+Gun/166236_1.aspx

#3

Plasma is (can be?) electrically conductive, so it could, in theory, be accelerated electromagnetically to rather high speeds; this makes the weapon a bit like a flamethrower, i suppose, but more directional.

There’s a fair bit of confusion over the term ‘rail gun’ in everyday terms; many people seems to use it to refer to a linear magnetic accelerator (a coil gun), but strictly speaking, it’s not that at all; a true rail gun uses the Lorentz force to accelerate the projectile.

#4

rail gun/mass driver/guass gun - fires a projectile using powerful electromagnets. Works just like a chemical powered projectile however the projectile travels much faster. These weapons are actually in development.

laser - The advantage over a projectile weapon should be obvious - a beam that travels at the speed of light and does not drop with distance. The disadvantage is that it is a line of sight weapon. These weapons are currently in development for shooting down aircraft and missles.

particle beam - fires streams of atoms or subatomic particles. Essentially it is a more powerful version of a cathode ray tube in a TV set.

plasma/ion weapons - presumably fires some kind of ionized energy which would make it another name for particle beam. At this point you start to delve into fantasy so how these weapons theoretically work depend on the author.

grazer/blaser/phaser/blaster/pulse riffle/disruptor/etc - Same as above. Basically how they work depends on how the author (who probably chose the name because it sounded “spacy”) decided it would work.
The biggest problem with most energy weapons IRL is powering them. Right now there isn’t a power source compact enough to make it practical to mount a laser, partical beam or rail gun in anything smaller than a Boeing 747.

Not to mention that they also are very complex and have a lot of delicate lenses and magnets and whatnot. Not ideal for battlefield conditions.

#5

I haven’t read any of the Honor Harrington books, but it sounds like a grazer would be like a laser, except that it would fire a coherent beam of gravitons. No one knows how that beam would be generated or how much energy it would require because no one has even definitely established that gravitons actually exist, as far as I know (but I’m no physicist).

The X-Ray lasers designed for the Excalibur version of Star Wars (SDI, not the movies) have not been firmly established to work. In Voodoo Science physicist Richard Park described the uncertainty over whether any lasing actually occurred in the only test I know of, a nuclear bomb test under the Nevada desert. Apparently only the optimism of Edward Teller can even make it appear like that weapon would work.

The only thing that would make a light sabre work is a Phased Linear Oscillating Transducer Device (i.e. a PLOT Device). :wink:

#6

plasma rifle

#7

One thing with handheld laser guns in the visible spectrum is that firing one powerful enough to cut through a human in seconds would blind everybody in a hundred yard radius simply through reflected coherent components of the laser. You can make it safe for the person using the gun by having shutter glasses connected to the gun that close for the duration of the pulse, but everybody else … bye bye eyesight.

#8

I can answer the rail gun one a bit. My old college prof did all of his research in high energy physics. He had a small railgun we could handle and pictures of a six-footer he passed around.

A rail gun is two conductors, like copper bars, spaced carefully apart along their lengths. The bars are surrounded by insulator material & then those are wrapped top & bottom with metal plates.


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This is the view from the end, the hole in the middle is where the projectile was fired from. The railgun was 13 inches long. The “X”'s is steel, the “I” is insulator (it looked like black plastic but was probably more sophistcated than that), and the “C” is the copper bars seen on end. The steel plates were a good inch thick and secured with a dozen and a half heavy steel bolts along the outer edges.

To power it, he spend hours and hours charging up a bank of capacitors. Each capacitor was the size of a kitchen trash can. One thing about a railgun is that it requires a buttload of energy released very quickly. Amperages are off the scale as compared to nearly any common electrical item.

Now, stuff a small piece of plastic down the barrel. This will be your projectile.

So, you connect the copper bars, the rails, to the capacitors and switch it on.

The capacitors release all their stored energy in a couple milliseconds. Between the copper bars, at one end, a spark strikes from one rail to another.

Now, you’ve got moving electrons, this generates a magnetic field. Electrons in a magnetic field, even a self generated one, generate force. In physics it’s often called I-cross-B forces. The spark, under its self-generated magnetic field, flies down the rails to the other end, propelling the plastic projectile ahead of it.

He said he could blow holes in an inch-thick steel plate with this little 13-incher.

Force on impact, kenetic energy, is E=mVV. (mass times velocity-squared). The plastic didn’t have much mass, “m”, but it had buttloads of “v”.

The sparc also tended to erode the copper bars, what really burst out the end was a projectile & a ton of copper ions. The gun was only good for a few firings until it had to be rebuilt.

The forces, by the way, are so great that it tries to rip apart the gun. That’s why the two huge steel plates & all the thick bolts.

The six footer in his picture had to be placed under a pile of lead bricks to hold it down during firing, he said. Even then, the bricks would all pick up a few inches & fall back down.

As you can see, it’s not easily hand-carried as a weapon. First you need a huge source of energy and the ability to discharge it rapidly. Second, it has to be strongly constructed which’ll limit it to being on a vehicle. Lastly, and this is no doubt being worked on, it has limited firings before the barrel is too degraded & it must be remade.

#9

How a Light Saber Works

#10

Of course, attempting to parry someone using a light saber (assuming you could find a power source to fit in the handle) would result in the blades passing through each other…which could really ruin your whole day.

Wow…thanks for the great responses everyone. I guess this WAS the right forum. :slight_smile:

-XT

#11

Of the weapons named so far, which, if any, are likely to actually be used in warfare? Or are we going to simply keep refining the current projectile gun technology?

-XT

#12

Who wants to bring up scalar weapons?

#13

Actually, a graser is a gamma-ray laser. Gravity tech does play a significant part in them, in the H. H. books, though, since they use gravitational focusing (lenses don’t work for gamma rays). There’s also a directed gravity weapon in the books called a grav lance, but it’s too bulky and short-range to be practical. It has the effect (if you can get into a position to use it effectively; a dicy proposition) of burning out an enemy ship’s drive and shield systems (both also based on gravitational technology), leaving one’s foe vulnerable to an array of other weapons.

I should mention that gravitational technology, so popular in many SF works, is probably just a pipe dream. The usual assumption is that we can manipulate gravitational fields just as we manipulate electric and magnetic fields. Well, that’s true, in a way, but it doesn’t get you much: The way we manipulate electric and magnetic fields is ultimately by moving charges around. So the equivalent for gravitational fields would be to move masses around. But while the charges needed for electromagnetism are manageable, the masses needed for practical gravitational effects are planetary in scale. In other words, if you want a gravity generator on your starship, all you need to do is carry the Earth around with you. Now, I’ll not rule out the possibility of practical gravity control, since a good scientist is loathe to ever definitively rule out anything. But there’s absolutely nothing to indicate that it would be possible.

#14

Pretty sure bomb-pumped lasers would work with today’s technology if you really wanted to build one. Essentially the very, very start of an atomic explosion is a crapload of x-rays. Focus those at something and you have an x-ray laser. The advantage is you get very high energy levels out of the x-ray laser. The disadvantage of course is you just exploded a nuke so you had better not be anywhere near (that and the weapon destroys itself so it only gets one shot).

This was proposed for Reagan’s Star Wars system as an anti-ballistic missile defense. Orbiting nukes not to mention the damage caused by setting them off in orbit saw the idea fall flat but I think they think it could be done.

I think the main problem with most sci-fi weapons is portability. Many sci-fi authors at least try to make a nod towards science but while a laser is something we can use today one powerful enough to be a weapon is not something you could carry around. Most of your portability issues will come from having a sufficient energy source to make your weapon useful. You can carry a laser pointer easily enough but it won’t hurt a fly. Want to drill a hole in a tank at two miles and you had better have a massive generator handy (and/or capacitors that could hold enough charge).

#15

Railguns of some form or lasers. Given a sufficent power source either of these could see a battlefeild in a matter of decades especially carried by tanks or AFV’s of some sort.

The problems of course are legion, right now you might be able to use something akin to a bradley AFV, with a crew compartment full of generators and capacitor banks to make something capable of doing some damage but probably nowhere near as effective as its current ammo based bretheren.

Lasers are also still pretty inefficent at converting power to a beam capable of damaging a target so it takes hundreds of thousands of kilowatts to create a beam that would put a hole in another tank at any significant range.

I would be interested if a sniper weapon of some sort might be slightly more feasible since rate of fire, number of shots fired, and weight are less of an issue since they already carry around some pretty hefty rifles. The lack of wind influence and bullet drop on a laser would be a huge improvement in the world of sniping. You would also only need to generate a shot capable of killing a person not penetrating the armor of a tank.

#16

You could do a plasma projectile gun, which is something like the Babylon 5 PPG. The idea is to first “bottle” the plasma into a projectile, which would be a charged bladder of some sort. Next, the filled bladder would be fired from the weapon. You could do this with a rail-gun-like design, using the charge of the bladder.

Of course, this arrangement would involve lots of energy.

#17

Here’s another article that explains how lightsabers work

and uses for a lightsaber, like cutting and toasting your bagel in one stroke.

#18

For a space based weapon system, a big assed computer, and a really good optical and EM observation system, and a stator accelerator for pitching stuff off your weapons station would work with not much in the way of “breakthrough” advancement. Of course, it’s a sitting duck for any similar system, and after about six of them get trashed in space, no one can fly around up there much at all.

Tris

#19

Yeah but would a laser really be all that damaging of a rifle? I mean burning a pinhole through someone probably doesn’t feel good but seems like minimal damage overall. If you got a sustained beam and sliced them up that would be one thing.

Actually I do not know what a laser would do. What would a high power laser do to someone? Assuming the beam is not from this thing (aperature looks wide enough to blow away most of a person in one shot) but rather narrow, laser pointer beam in diameter what would it do? Would it superheat fluids and make the person explode? Drill right through in a blink?

#20

What kinds of (realistic) potential power sources may exist to power some of this stuff? Could you, say, use really efficient capacitors…maybe in individual packets (somehow), almost like bullets, that would have sufficient energy stored for a single ‘shot’.

BTW, facinating discussion so far…I LOVE this board. :slight_smile:

-XT