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Plasma cannons and other SF weapons

  1. Dec 28, 2016 #1
    I think about a far future story with a good amount of battles.

    Futuristic battletech i can imagine would involve things like deploy nanobot clouds that jam and damage sensors and everything vulnerable, powered battle armors of course, drones, probably some meelee solution for bunker combat (create such a strong EMP for a short time that even nearby energy based weapons explode?).

    I thought, that probably the most fearful enemies of space marines wont be giant robots, but small drone snipers, that can literally dodge bullets. Lasers could be a solution, but an important element in the story of my universe is the development of X-ray mirrors (a combination of really strong magnetic field and alien alloy, atoms arranged so precisely, that they bounce of X-rays, so an X-ray dielectric mirror) so deep space combat will be missile based.

    I wondered whether there is a more or less plausible way to have weaponised plasma?
    I thought that probably a plasma weapon could actually fire a supervelocity slug, but it quickly turns into plasma in air. Maybe the projectile could generate plasma in front of it, similar to supercavitation?
  2. jcsd
  3. Dec 28, 2016 #2


    Staff: Mentor

    Have you read The Expanse novels? They are like the Game of Thrones in outerspace. The battletech is navy based with stealth and railguns and some more exotic weaponry.
  4. Dec 28, 2016 #3
    First book was good space crime story. Third i couldnt finish reading it, it became áll about pushing pseudo religious texts shallow thinking about evolution and how to make everyone a total idiot so Holden can save the world again and again.
  5. Dec 29, 2016 #4


    Staff: Mentor

    What I liked was how the monster keeps morphing in unexpected and more dangerous ways.

    I didn't get the vibe you got from the third book perhaps because I just glossed over it.

    One thing though was the naval battles and how they are fought was quite interesting and somewhat believable. I like sci-fi that tries to stay true to the physics of things.

    With respect to your plasma weapon perhaps the plasma could be shaped into a streamlined shape like a torpedo and then when it hit the target would envelope it or the plasma could surround a central object that emanates a field that contains the plasma.
  6. Dec 30, 2016 #5
    It shoulf move through air around 100km/s so i think it should be streamlined.


    Watched this, ionization energy of nitrogen and oxigen around 1400 kj/mol. With density, molar mass, i calculated around 12,5 MJ energy to create 1cm*1cm*1km plasma path, although the point of the supervelocity slug could drag plasma, so probably less could be enough.
    1g to 100km/s is 10 Mj, so if my calculations are correct, around 22,5 MJ to create 1km plasma pathway for 1g slug.
  7. Mar 27, 2017 #6
    I wondered about a nonlethal, taser like weapon, but without wires.
    Is it a bit plausible for near future story (where most handguns still use powder, it isnt that easy to drag 20kg conventional battery, or an isotope battery) to say, a shock pistol blast the target with sound and microwaves?
    It would be rather inefficient compared to firearms, standard one only two shot, and short range.
  8. Mar 31, 2017 #7
    Have you looked into smoke ring guns some of the highest energy ring cannons can knock down walls
    I imagine a plasma version may even be possible
    But it's certainly plausible enough to do well in a book
  9. Apr 3, 2017 #8
    The problem is that vortex cannons work by the physics of fluid dynamics. Plasma follows no such rules; its behavoir is dominated by electromagnetic forces.
    Last edited: Apr 3, 2017
  10. Apr 3, 2017 #9
    I am sorry but no
    plasma follows all the rules of fluid dynamics AND is subject to electromagnet force otherwise how can you blow out a candle and why does fire follow convection currents ?
  11. Apr 3, 2017 #10
    Fire is not a ball of plasma, it's just a temporary plasma state or the material being burned. The plasma that you see in a flame is not the same plasma that was there a microsecond ago. Chemical processes are fueling that process continually, it is not self contained.

    I retract what I said about EM dominating. I was thinking about how it would work in space; under and entire atmosphere worth of pressure, fluid dynamics would still play a major role.

    That in itself is a problem though. In a vortex the contents inside the spinning air is at the same pressure as the atmosphere that it's going through. Plasma is way higher temperature (and cold plasma wouldn't give you any effect.). So it should just blow up. I'd also think it'd be quite wasteful. I'd bet very little air actually moves from the cannon to the target. I know that some does (you can blow a smoke ring) but it seems like it'll leave most of its energy in a tail.
  12. Apr 3, 2017 #11
    I think that the OP is using the plasma guns on the surface
    And you have a good point about EM effecting plasma maybe a combination of
    EM and FD start with FD and then heat up and accelerate with EM
    Ha ha it would look like a freaken Flash Gordon raygun shooting glowing donuts
  13. Apr 4, 2017 #12
    Well since it should take out a really fast drone, it shouldnt be like SW blasters (too slow in the movies) but rather like a blazing ray (supervelocity projectile and ionization of air)
  14. Apr 4, 2017 #13
    Hmmm ok how about if a maser excited a column of air into plasma and
    You used the plasma as an electrical connection to negatively charge the target
    And then somehow positively charged the plasma column it would suck itself into the target like acid spaghetti elwire
    Or shoot a slug of molten copper so fast it leaves a vapour trail behind charge the heck out of it as soon as the slug hit something BLAM parabolic lightning bolt.
    Last edited: Apr 4, 2017
  15. Apr 4, 2017 #14
    What is BLAM?
  16. Apr 4, 2017 #15
    You need to close the circuit, and I'm afraid it would short-circuit pretty early into the ground.

    A sound made by lightning.

    Well air combat is much harder than space combat. Underwater is even harder, underground yet more.
    I haven't seen launched grenades mentioned before, although you probably don't want your missile to be more expensive than its target.

    I don't know how hard it is to make an ion thruster's beam very narrow, as in several atoms, but a high-velocity stream of heavy nuclei should cut the drones in half quite easily.
    Someone should check the math on air drag though... you can assume that air is rushing into the beam at the speed of sound all along the beam, and needs to be accelerated to a speed similar to that of the beam. So it should be very narrow, dense and fast.
  17. Apr 4, 2017 #16
    How should a grenade hit a really fast drone?
    Yes in space a relativistic particle beam is great, the question is, whether it is possible to overcome air drag (or vaporization of projectile) with somekind of plasma or supervelocity weapon?
  18. Apr 4, 2017 #17
    For one of my own stories I designed a kugelblitz projectile weapon. Focus an incredible amount of gamma rays into a tiny point so that it forms an event horizon and stays contained. Calculate exactly how far you want it to go before it detonates, then do the Hawking radiation math to figure out exactly how much energy to put into the projectile, then send it off in the direction of your enemy.

    It'd quickly evaoparate as it goes, but would be so tiny that it would pass straight through the atoms of the hull of the enemy ship. Once inside, it'll explode and does so with the energy of a nuke.
  19. Apr 4, 2017 #18
    The idea was that the grenade would just explode nearby.

    I did a bit of math and if you could focus the beam to 5 atomic diameters (about 1 nm), it seems that for 1 km beam it would drag around 1.3 grams of air per second. That sounds doable.
    That would be a lovely weapon, but I thought about something similar just yesterday. If visible light was used, the mass of the light would have to weigh about 1/10000 of earth mass (unless I made a mistake). Focusing such an amount of energy into a sphere of diameter just one wavelength sounds quite challenging. Have you found some serious treatment on making a kugelblitz?
  20. Apr 4, 2017 #19
    I've seen many different estimates for the minimum size of a kugelblitz, and they're radically different depending on whether you assume GR holds for such small things or not. None of them are that massive though, if you converted 1/10000 the matter of the earth into pure energy, you'd get a monster explosion, way more than I was thinking of. I was thinking more along the energy equivalent of a few grams at the most. Remember that you WANT these things to explode fairly quickly and the bigger you make it, the more stable it becomes. You don't have to fit anything inside of a wavelength, just inside the Schwarzschild radius, and I would assume gamma rays would be used as they are much higher energy.
  21. Apr 4, 2017 #20
    I read a book with a similar idea but it was with lasers
    The idea being the laser had so much photonic mass that it would collapse into a ball and as soon as the tail caught up to the head it would explode into a cone of light
    I don't know how accurate that may be but it makes for a good book
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