Sci-fi weapon... does this sound feasible to you?

In My Humble Opinion
1

I like to write. I like to write sci-fi/space opera. I like figuring out all sorts of bizarre, obscure little gadgets and gizmos and weapons that sound like they’d be pretty cool. However, I’d like to maintain a little bit of realism.

I had an idea for a space-borne weapon system, and I want to run it by everyone to see how feasible they think it would be (in theory). Essentially, the weapon is an anti-matter gas that is released from magnetic containment into the vacuum of space. It’s purpose would be to act as a sort of large-scale space minefield. The idea is that, since there is very little matter floating around in space, the anti-matter field won’t immediately erupt in a massive explosion of energy (which is what would happen if this were released in atmosphere). Hopefully, an enemy vessel comes floating along, drifts into this massive cloud of anti-matter, whereupon the A-M makes contact with large clusters of matter, and… boom.

Well, okay. “That’s a fine idea,” my brain says. “But be wary of anti-matter weapons… them’s the stuff of Star Trek, and we all know how idiotic Star Trek is.” :smiley:

So I thought, “Well, my fellow dopers are pretty smart. Maybe one of them will come along and say, ‘SPOOFE, you’re a genius’ or ‘SPOOFE, you’re an idiot’ (or both).” So… would this anti-matter cloud be a feasible idea? Sure, after a while enough stray particles will drift into the cloud and cause the whole thing to dissipate, but what about in the meantime? Assuming that the ship laying the cloud has the systems capable of keeping the anti-matter gas from interacting with the delivery systems… do y’all see any major hurdles in this idea?

2

If you want to use it as a mine field, don’t you want it to be undetectable? A cloud of antimatter would be pretty easy to detect - it would react violently with the solar wind and other interplanetary (or interstellar) matter.

Have you done the math and calculated how much of the antimatter you need? The amount of antimatter M you need to produce energy E is of course E = 2 M c^2. (2 is there because mass M of antimatter reacts with mass M of normal matter.) One kiloton TNT equivalent is 4.18x10^12 Joules. Decide how much energy density you want and how much volume of space you want to cover, and you can calculate how much antimatter you need.

I think tiny lumps of antimatter may work a bit better. That is, dust or sand instead of gas. Larger lumps will survive interaction with interplanetary particles longer. Of course, it shouldn’t be so large that the gaps are large enough for enemy ships to pass through.

3

If these ship can travel near, at or above the SOL they will need something to push stray particals away from them unless they are not traveling throught space-time (i.e. hyperspace). They would need something like a deflector shild used in S.T. that should also work w/ antimater.

How about a few 'roids (maybe a ft in diameter- maybe less) that appear like normal matter but have a A/M containment inside and a proplusion/guidance system.
The A/M weapon might make a good partical acc. gun.

If you do have hyperspace capability then why not just hide the mines in hyperspace triggered by a very small proximity detector.

4

Iain M Banks uses a similar weapon in his novel Consider Phlebas, which he calls collapsed anti-matter (CAM). I vaguely recall it being ‘dusted’ over large vessels or space stations to destroy them.

5

(pulling flower petals)

SPOOFE, you’re a genius!

no,

SPOOFE, you’re an idiot!

no,

SPOOFE, you’re a genius!

no,

SPOOFE, you’re an idiot!
etc…

6

Another consideration would be dispersion.

How persistant do you want your interdiction cloud to be? You’d need to calculate the rate of dispersion, and the desired density of the cloud, and then adjust the amount of AM released to create the persistance you want. If you’re just trying to cover your back-trail for a few minutes while you high-tail it out of orbit, low-persistance is fine, and you can use relatively little AM. In fact, gaseous AM that reacts noticably with space dust and the Solar wind woud be a plus in this case, as antagonists would know it’s there, and have to adjust orbit/trajectory to avoid it. If high-persistance is desired, then the cloud would need a higher initial mass, and would eventually wind-up covering a far larger region than a low-persistance cloud, and would present a hazard to ‘navigation’ over a far larger voulume of space.

As a self-defense, it also has possibities. You could drop slugs of AM gas or particles into the path of incoming projectiles or missiles, and allow the M-AM reaction to disable or blow them off course. Alternatively, if it’s tail-chase (two vessels on similar trajectory), you could ‘stream’ AM gas behind you, forcing any projectiles or missiles to to fight their way “up stream” through the AM, and would likely force the trailing vessel onto a different trajectory.

7

I did some back of the envelope calculations and here is what I got.

Lets assume you want to interdict an area of one cubic kilometer. This is pretty small by space standards, except for things that have no real ability to maneuver.

Further let’s assume that you’re using 100kg of antimatter Hydrogen. You may use more or less, but to me that is a pretty scary amount of stuff to keep on hand.

When you scatter the hydrogen over one square kilometer, you wind up with 1x10^-4 grams of the stuff per cubic meter. That means that each cubit meter will have 6x10^14 j of available energy in it, assuming it is able to completely cancel itself out with an equal amount of matter. That would be more or less equal to 150 kilotons of TNT for every cubic meter.

If the enemy sends in a spacecraft with a frontal surface area of 10,000 m^2 (say a 100 m cube), it will encounter 1x10^7 cubic meters of hydrogen as it passes through, for a total energy exposure of 6x10^21 joules. This is rather a lot, being equal to a hit from a 1500 gigaton warhead.

However, as somebody already pointed out, a cloud of antimatter in space would be quite visible to many sensor types, as its’ reaction with the few errant hydrogen atoms that had the misfortune to be around would produce heat, radiation and a not inconsiderable particle flux. Assuming the approaching ship could maneuver, it could be avoided. It could also be dispersed or detonated without too much trouble by hitting it with some type of loose-focus particle beam, or even firing a missile at it. Either one would probably introduce enough matter into the cloud to disperse it partially or completely. Mind you, there would also be quite a bang when it did so.

Also as somebody pointed out, any ship that was equipped with a way to shield itself from particles in space (navigational deflectors, to use the Trek term) could probably also brush the cloud aside.

Added to which the cloud would continue to expand, rather rapidly in “empty” space, so it would be effective only for a very limited period of time. How quickly this would happen is a more tricky calculation than I have room for remaining on my envelope.

All in all I’d have to say you’d probably be better off with a high-speed short ranged missile with an anti matter warhead that just launched itself at any ship from which no IIF signal was forthcoming, but that wouldn’t be as neato, I’ll admit… :slight_smile:

8

I like the dust idea. If they appear to be nothing but random interstellar particles (the collision with which would have to be accounted for in the design of a vessel) then they would be a formidable weapon.

So if you can figure out a way to mask the antimatter’s presence, and somehow shield it from reacting with anything that is not of a given mass or momentum (sort of like a weight-sensitive mine, or even have it detect the presence of large masses and then zoom toward them), then meybbe.

Otherwise, it would be too easy to get rid of. I could see a futuristic version of the now-infamous daisy cutter, clearing antimatter minefields. In fact, chucking out any kind of cheap mass - water comes to mind for some reason - would trigger them. I imagine there would be something of a chain reaction as well if they’re too close together.

The dispersion comments are good - might want to have them self-destruct after a certain time (or not, depending).

9

I’m reminded of the time we all went out to lunch at El Famous Burrito and the fan in the men’s room was broken…
More seriously, though, wouldn’t the “cloud” tend to attract itself and coalesce into larger pieces unless it was dispersed too far afield to do much damage?

B.

10

Hmm… well, since my sci-fi setting has the ships equipped with shields, I suppose the AM cloud wouldn’t be that effective. It’s a nice idea, though… I’ll have to shelve it and see if I can use it somewhere at a later time. A billion thanks to Leonidas (and everyone else) for calculations and thoughts on the idea.

K2Dave…

Well, my anti-matter guns are railguns that fire meter-long slugs that contain a magnetic containment generater and a healthy dose of anti-matter. I just wanted to see if I could use anti-matter in other, non-conventional ways.

11

my only beef is the same one I have with land mines: How do you clean up after the war is over? I mean, land mines are a bitch to find and extremely deadly. I am thinking an antimatter cloud would be just as bad. And can you imagine one of these clouds surrounding a planet? It would be considered an atrocity and all remaining galactic factions would declare war on you.

On the subject of exotic weapons, I always liked the concept of genetically engineered beasts of war unleashed on a battlefield…

12

In terms of cleanup, the antimatter cloud would actually be pretty easy. It would continue to disperse itself, and react with whatever random particles of matter happened to wander by. Even in a low orbit it wouldn’t do much more than put on a light show for the people below. The only real problem would be if there were something in the same orbital path as the cloud. That could get ugly.

You’d have to spray an awful lot of the stuff onto the atmosphere of the planet before you’d get much effect, as it would begin reacting faster as it got into the more dence layers of the atmosphere, probably running out of steam long before it got anywhere near the planet’s surface.

Now if you could get it down to the planet first, then it would be something really impressive…unless you were nearby…

13

If you use tiny pieces of antimatter rather than gas, it would solve the dispersion problem. Gas expands, but a cloud of dust or sand would stay put for a while. It’d stay a long time if you fill up a stable orbit or Lagrangean point with that stuff.

As for shields, it depends on what mechanism yours uses. Larry Niven’s General Products hulls are invulnerable to everything except antimatter.