Prepare to Repel Boarders! Marine ship defense tactic help

[Venusian Broon]

Actually I tell a slight lie as a recoiless gun is possible if a significant amount of the propulsion gas is allowed to escape backwards (balancing the projectile). However it would not be a good thing for any friendlies behind you in a confined space like a spaceship. (see here).

On the other hand for in-ship fighting low velocity and relatively light projectiles (darts maybe rather than bullets) would be perfectly adequate for such short range fighting (not to mention significantly reducing the risk of hull punctures) and even in freefall the differences in mass between firer and projectile should then be negligible. Though you would probably still want to stick to single shots rather than a machine gun.

I had done my research before posting my comment so I knew we already had such weapons (I agree, not great for man on man confined shipboard fighting).

In fact the principle is rather simple, so if you really wanted some sort of L85A2-type weapon in the hands of people bouncing about in free-fall, why not have some sort of force cancelling mechanism built into the gun (a relatively big piston that is triggered the same time as the bullet shot in the exact opposite direction. You'll know all the forces, and the piston will be safely encased in a stock, hence not knocking out any member of your team behind you!) . Recocking the gun to the next projectile will to involve resetting the piston back of course.

Just a stab in the dark, I'm not a weapons designer nor great engineer

I would be probably go for anti-personal 'terminator' drones anyway to clean out a ship of any pesky humans - heavily armoured and not too bothered by a bit of exhaust gas

 

[Vertigo]

In fact the principle is rather simple, so if you really wanted some sort of L85A2-type weapon in the hands of people bouncing about in free-fall, why not have some sort of force cancelling mechanism built into the gun (a relatively big piston that is triggered the same time as the bullet shot in the exact opposite direction. You'll know all the forces, and the piston will be safely encased in a stock, hence not knocking out any member of your team behind you!) . Recocking the gun to the next projectile will to involve resetting the piston back of course.

Unfortunately that wouldn't work. The recoiless gun works by flinging the projectile one way and the gasses/counterweight the other way, leaving your momentum unchanged. Any enclosed system whether it is pushing pistons/compressing springs or whatever, still imparts the recoil momentum on to the firer. Spring type systems can alleviate it a little by storing the energy but when it is released (eg operating the reload bolt) the effect will be the same. You can't get away from the net change of momentum without slinging something away in the opposite direction.

It's actually not dissimilar in some ways to the problem of nuclear space craft engines. It doesn't matter how much energy your nuclear reactor generates, your spaceship won't move until you use that energy to fling something out the back. So whilst very little material is needed for the actual nuclear reaction, you need a whole lot of reaction mass to sling out the back and your spaceship effectively moves on the recoil from that reaction mass. That reaction mass is the 'fuel' that presents the biggest problems for realistic spaceship designs.

 

[Venusian Broon]

Unfortunately that wouldn't work.

Told you! I'm just not that good with practical 'get your hands dirty science' things. Have always preferred theory and models!

Its irrelevant for my WiP as my ships have artificial gravity and I don't have combat in freefall between people a.k.a. no space marines boarding flying battleships. But it's interesting trying to come up with 'solutions' here.

So next design (this is a bit like space-dragons den),

How about a bracing arm/hi-tech 3D tripod that fixes itself into a immovable object, like a corridor wall, while the weapon is mounted in some sort of heavy duty joint of the tripod (so you can change the aim, otherwise I suppose it ain't that useful). Assume as well that the trooper will try and find the best possible place to 'brace' himself - perhaps with the properties like PiousFlea suggests. Not recoilless of course.

Clumsy, but maybe this would mean that you could rapid fire?

 

[Vertigo]

I could see that working in much the same way as a platoon will generally have one heavy machine gun typically with a stand of some sort whilst the rest have lighter weapons.

I still think some sort of dart gun is more likely. Not much mass so not much recoil and minimal risk to the craft's structure. They could be powered by compressed gas so avoiding the risk of sparks and stuff causing explosions in an enclosed space (and incidentally silent). The darts could be loaded with fast acting toxins/sedatives/nerve agents giving flexibility in use. They could also easily be made non-metallic making them light and hard to detect.

 

[Venusian Broon]

I still think some sort of dart gun is more likely. Not much mass so not much recoil and minimal risk to the craft's structure. They could be powered by compressed gas so avoiding the risk of sparks and stuff causing explosions in an enclosed space (and incidentally silent). The darts could be loaded with fast acting toxins/sedatives/nerve agents giving flexibility in use. They could also easily be made non-metallic making them light and hard to detect.

I like this idea as well, it makes sense to me. Has this been used elsewhere?

I say this because I'm finding my soldiers walking about with needle guns in my WiP (i.e. the projectiles are needle-like), and I'm sure they must come from other SF work. I just can't think where.

I might have to change that, because I'm not sure they'd work that well in a heavy earth-like atmosphere, perhaps if they are spat out at very high muzzle velocities so that they deform/liquify into something a bit more aerodynamic through friction, wheras if fired in a vacuam they retain their long sharp profile....

 

[Abernovo]

Flechette guns are around now. They have potential problems, due to flechettes passing through targets and hitting bystanders.

In a vacuum though, where they could be designed with edges to rip, they would be deadly. With a little redesign, you could have them deliver a dose of toxin, as Vertigo suggests, or even fit them with a small capacitor to deliver an electrical shock. Overload the nervous system.

 

[Piousflea]

Needle guns are a popular theme in science fiction because a needle-shaped projectile has better penetration than an equal-mass round projectile, allowing relatively low-velocity needles to penetrate flesh. If the needle is fairly brittle then it may be lethal against unarmored humans while fragmenting harmlessly on hard surfaces. (ie spaceship hulls)

Needle shaped projectiles fly quite well in an atmosphere as long as they have fins. (aka flechette rounds) Without fins they would tumble and disintegrate (unless magically guided like in Halo).

One problem with needle-shaped projectiles is that they are very thin, so they cause less damage to tissue than a rounded projectile of equal mass. A low velocity needle won't be as lethal as conventional bullets, you might need to be very accurate with headshots. In order to be highly lethal, a needle-shaped projectile has to either have exceptionally high energy (ie flechette shotguns and flechette bombs) or it has to have a secondary effect. (ie poison, electricity, explosion). If it is really high energy then it loses the "hull safe" characteristic.

 

[Vertigo]

Yeah, agree Piousflea, that's why I would opt for the low energy/velocity needle/dart combined with a toxin.

The big downside would be dealing with armoured soldiers. Though it might depend on the type of armour; it is possible that a needle/dart/flechette would actually penetrate most current kevlar style armour much more easily than a bullet. However (and I've never considered this one before) a variation on the taser might be a very effective weapon against a heavily armored soldier if the armour is metal based.

 

[psychotick]

Hi,

Needle guns are an interesting idea because you can imagine that they have less recoil then normal bullets, so would be a better choice in a spaceship where both hull integrity and recoil are important. But I still think all forms of projectile weapon would be a mess in space.

I imagine hulls would be sturdier then the aluminium foil of modern satellites that we use today, but there must be a limit. The sturdier the hull surely the more it weighs, and weight is the enemy of acceleration in space, and if it lands on planets, it's the enemy of gravity wells as well.

As for internal gravity on a ship, surely there are three options for generating it. You can spin the ship, you can have some sort of artificial gravity, or you can use something else like magnetic boots instead. If you spin the ship, anything that interfers with the ships spin, or the spin you experience, interfers with your perception of gravity, say for example, moving closer to the centre of the ship where gravity will be less. Artificial gravity will surely be provided by some sort of machine, and machines can be turned on and off, and they can be destroyed. And magnetic boots come with a different set of problems since the strength of the magnetic field decreases faster with distance than does a gravitational field. In short, your boot provides some attraction maybe an inch or two above the steel deck, but after that you're weightless.

So whatever combat system you use it has to be designed in mind with the possibility that at some point in time, you are going to be weightless. At that point recoils a bitch.

Recoiless guns are in use, but as others have said, they mostly just vent gasses out the back or to the sides. They aren't truly recoilless, and from memory there's a price paid for having such a weapon, lower muzzle velocities (I'll actually have to do some fact checking on this but I'm sure the weapons don't have the same punch as their conventional equivalents).

And I forgot to mention, projectile weapons have another problem in a steel tin can like a space ship, ricochets. Frangible rounds may help with this, and may even save the hull, but at the same time, if your opponent's wearing some sort of body armour, the bullets may be useless against him as well.

Darts with toxins is an interesting idea, it gives a decreased recoil for a greater penetration of flesh and secondary method of delivering damage, but still only useful if your enemy is human. Aliens may not be too bothered by what poisons people. And it may take some time for the toxin to work.

You might want to check this site out on the wiki.

http://en.wikipedia.org/wiki/Directed-energy_weapon#Sonic_weapons

Cheers, Greg.

 

[Ursa major]

* Wonders why he's beginning to recall images from the ST:TOS episode, The Naked Time. *

 

[Vertigo]

Came across another technique recently (courtesy Lois McMaster Bujold). If you have true artificial gravity (rather than just centripetal force or the acceleration of your spaceship) and if it can be localised. You could crank up the gravity in the neighbourhood of the borders, and I mean seriously crank up the gravity, like bone breaking strength. Bujold actually used it to catch some escaped contagious birds on a space station. But something like that could make an extremely effective weapon.

 

[Stephen Palmer]

"How do you repel boarders? Stop changing the bedsheets!"

Spike Milligan, 1955.

 

[Esfires]

All of this sounds like it would be a wonderful excuse for using melee weapons in space.

 

[psychotick]

Hi,

A La Deathstalker? No melee weapons would suffer from the same momentum problems as projectile weapons in space if the gravity failed - or actually worse. Imagine swinging a sword one way and spinning out of control the other. You could easily end up cutting off your own leg!

Cheers, Greg.

 

[Vertigo]

That's very true psychotick! Maybe we'll just have to go back to the good old ray gun

Incidentally on the melee weapons, one thing I always liked about Herbert's Dune was the clever way he made knife fighting an essential skill in a futuristic world.

 

[Piousflea]

Came across another technique recently (courtesy Lois McMaster Bujold). If you have true artificial gravity (rather than just centripetal force or the acceleration of your spaceship) and if it can be localised. You could crank up the gravity in the neighbourhood of the borders, and I mean seriously crank up the gravity, like bone breaking strength. Bujold actually used it to catch some escaped contagious birds on a space station. But something like that could make an extremely effective weapon.

Hasn't crushingly powerful artificial gravity been used as a weapon in everything from Ringworld (or one of the other Niven books, I forget which) to Star Trek to Babylon 5? That makes it one of the "oldest tricks in the book" IMO. (although it is puzzling how often they don't use weaponized artificial gravity in Star Trek considering how powerful it should be)

 

[Vertigo]

Yes certainly has been used many before, it was just that coming across it recently put me in mind of it for this discussion - I had simply completely forgotten about it the old brain cells aren't what they used to be.