Prepare to Repel Boarders! Marine ship defense tactic help

[Piousflea]

Originally Posted by James Coote

I can't imagine you'd use swords or melee weapons for the same reasons. You might just slice though a 1amp electricity conduit by accident

My densified nano-diamond blade laughs at your puny ampere of current.

[Gumboot]

Originally Posted by Piousflea

My densified nano-diamond blade laughs at your puny ampere of current.

It may indeed, but if your densified nano-diamond blade conducts electricity your body won't be laughing at that 1 ampere current (1 amp is the current required to stop a human heart).

[Piousflea]

Originally Posted by Gumboot

It may indeed, but if your densified nano-diamond blade conducts electricity your body won't be laughing at that 1 ampere current (1 amp is the current required to stop a human heart).

Pretty sure that diamonds are non-conductive. That was supposed to be the point of the joke.

[psychotick]

Hi,

I knowlittleabout the combat side of things, but I do read a little about weaponry, and my thought is that this would be vital to your scenario.

I don't think any projectile weapon would be a flyer in space. Apart from the obvious risk of puncturing the hull and suffocating everyone, think about Newtons little rules. If the gravity's off for whatever reason, and everyone's floating about, you shoot in one direction and fly backwards.

Explosives are even less likely, because not only might you blow the hull, but you could also start a fire which would consume your air. And then there's the shockwave to consider. The overpressure shockwave would be channelled down corridors at massive velocities and would probably be just as deadly to friends as foes.

Lasers at least don't have a recoil, but they would start fires. And rail guns, assuming you have one that's small enough to hold, would just be even more dangerous projectile weapons.

My thought would be to look at some of the DARPA stuff for non lethal urban pacification, and start advancing their ideas. Recently I've seen docos showing the use of sound waves to pacify crowds, and so maybe a sonic pistol could be set to rupture flesh and not metal. Also they have weapons that can fire foam that sets hard around people in seconds, trapping them. Also from my gaming, how about grease guns, that leave the enemy floudering, but thanks to specially designed boots, your people can walk safely through.

Also as Paul said - on ships doors are your friends. On space ships my thought is that they could be your absolute bestest friends. Simply lock them in a section of the corridoor that's air tight, and remove the air.

Hope that helps.

Cheers, Greg.

[Venusian Broon]

Originally Posted by psychotick

Hi,
think about Newtons little rules. If the gravity's off for whatever reason, and everyone's floating about, you shoot in one direction and fly backwards.

Although there isn't a market for space personal weaponary, so no one has probably bothered to research/test anything...

...surely it would be easy enough to construct some sort of recoiless projectile weapon system for zero-g/freefall. If that was your goal (and you wanted to puncture the ship's hull - perhaps you don't care about the air inside and you are suited in some manner)?

[Piousflea]

Originally Posted by psychotick

I don't think any projectile weapon would be a flyer in space. Apart from the obvious risk of puncturing the hull and suffocating everyone, think about Newtons little rules. If the gravity's off for whatever reason, and everyone's floating about, you shoot in one direction and fly backwards.

Any spaceship/starship plausibly capable of safe interplanetary/interstellar travel is going to be MUCH sturdier than the flimsy structures we are launching into space with current-day tech.

A starship that can realistically travel long distances will be built to withstand impacts from space debris far, far more energetic than a modern sniper rifle bullets. I don't think it's unreasonable to have projectile weapons capable of killing people but not capable of puncturing their hull. On a sufficiently large starship the walls would likely be very thick, and would be surrounded by water or other radiation shielding instead of vacuum.

Even if you had a hypervelocity railgun capable of penetrating relatively strong starship walls, it wouldn't take a whole lot of nanotech to create self-repairing walls. All you need is a material that can liquefy/solidify on command. Surface tension would pull it into place and then it could solidify into an air-tight (if not particularly strong) plug. This is a vastly lower tech level than say, a Iain Banks General Systems Vehicle.

[Mpaul301]

Originally Posted by Piousflea

Even if you had a hypervelocity railgun capable of penetrating relatively strong starship walls, it wouldn't take a whole lot of nanotech to create self-repairing walls. All you need is a material that can liquefy/solidify on command. Surface tension would pull it into place and then it could solidify into an air-tight (if not particularly strong) plug. This is a vastly lower tech level than say, a Iain Banks General Systems Vehicle.

This being true, it may work out better for the invading force. A ship's battery railgun (ie VERY large calibur) would, as I stated, punch a hole in the ship, ignite the local air supply, perhaps even punch out the other side, and (even if momentarily) expose the crew in affected spaces to vacuum. If the hull seals again, then the only damage done is the loss of some atmosphere and a whole bunch of crew. If your intent is to fight with the captured ship, then that works out VERY well... No lengthy and dangerous damage control operations.

[Venusian Broon]

Originally Posted by Piousflea

Any spaceship/starship plausibly capable of safe interplanetary/interstellar travel is going to be MUCH sturdier than the flimsy structures we are launching into space with current-day tech.

A starship that can realistically travel long distances will be built to withstand impacts from space debris far, far more energetic than a modern sniper rifle bullets. I don't think it's unreasonable to have projectile weapons capable of killing people but not capable of puncturing their hull. On a sufficiently large starship the walls would likely be very thick, and would be surrounded by water or other radiation shielding instead of vacuum.

What's clear is, to get the correct 'answer' you have to have decided what all your technologies at the time of your novel are available and also have a design philosophy.

For example an orbiting dyson cylinder is specifically designed so that it can sustain being punctured by debris. The reason is because Mass really matters in this case and it makes a lot of sense to build the infrastructure as light as possible. From my reading, it seems that the reduced overall air pressure and the large volume ensures very little loss of air and you can quite leisurely replace any damage.

In fact if your starship engines are not powered by handwavium and do not produce Giga-terra watts of energy to propel the ship forward at a snap of a finger*, then you'd have to factor in mass as a constraining factor of your starship design. It would be a bit like the early days of tank development: Do you built a heavily armoured 'walking' pillbox that might manage 4kph, or sacrifice armour and get something zipping about at 40kph, or do you build in a big gun and sacrfice some armour and speed?

However I would agree that it would relatively simple to come up with some sort of well-protected hull - and if it was specifically designed to be a war craft of some sort, there would be an arms race between armour+protection and weaponary designed to puncture it. (Why a war craft would have big corridors inside it and people walking about is another question, unless it was a transport of some kind I suppose...)




*Let's face it most people just assume this in most spaceship futures

[Vertigo]

Originally Posted by Venusian Broon

Although there isn't a market for space personal weaponary, so no one has probably bothered to research/test anything...

...surely it would be easy enough to construct some sort of recoiless projectile weapon system for zero-g/freefall. If that was your goal (and you wanted to puncture the ship's hull - perhaps you don't care about the air inside and you are suited in some manner)?

A recoiless gun is an impossibility. All projectiles have mass and if one is accelerated away from you, by whatever means, then you will be accelerated in the opposite direction. That said if your mass is (as is likely) considerably greater than that of the projectile then the effect on you will not be all that significant. The kick you feel when you fire a hand gun seems quite large but that is because it is really only affecting your hand. If the gun is rigidly fixed to you body it will not seem as great.

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.

[Piousflea]

If the gravity's off for whatever reason, and everyone's floating about, you shoot in one direction and fly backwards.

If you want to fight effectively, you will almost certainly try to avoid "floating about". Staying near hard surfaces allows you to take cover behind corners and such, while floating freely leaves you exposed.

So you can safely assume some sort of magnetic +/- adhesive ability in combat spacesuit boots and gloves, which should allow you to absorb reasonable amounts of recoil without floating up and away.

Originally Posted by Vertigo

A recoiless gun is an impossibility.

Recoiless rifles exist, but as pointed out they will eject something backward - either explosive gases or a counterweight - rather dangerous for anyone behind you.

Alternatively, if your spaceships are propelled by non-inertial handwavium, you can simply propel your bullets with smaller amounts of non-inertial handwavium.

Note that a true hypervelocity weapon may well have less recoil than a "modern day" firearm. Muzzle energy increases with the square of velocity, so as velocity increases you can use a much lighter projectile and have less total recoil with the same muzzle energy.

In the supersonic range of velocities (ie gunpowder firearms) you'll lose a lot of stopping power by having a lighter, faster bullet. However, as you get into the hypersonic realm your projectile starts to deliver thermal and concussive energy and may remain destructive even with very small size and mass. (ie, it no longer follows the ballistic stopping power equation)

Of course, as you approach the relativistic limit of very high velocity and very low mass you end up with a particle beam rather than a projectile.

On the opposite end of the spectrum, low-velocity frangible rounds could be designed to have extremely low penetration and minimal damage against walls, such as this round used by air marshals:
http://en.wikipedia.org/wiki/Glaser_Safety_Slug

[Venusian Broon]

Originally Posted by Vertigo

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]

Originally Posted by Venusian Broon

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]

Originally Posted by Vertigo

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]

Originally Posted by Vertigo

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....