cannons in space

[ravener]

in sci fi games and stories you always need some sort of armament, this is mostly lasers, beams and rockets, but could a cannon be a useful addition to a sci fi setting?

also, sorry in advance for my more than likely ****ty english

obvious points before i get to space cannon design:

cons to cannons in space:

-weight. cannons are notoriously heavy in addition to heavy ammo.

-recoil. if your ship has limited fuel to correct the trajectory, you might not be able to afford wasting fuel correcting for recoil.

-accuracy. if you work on ranges over a few tens of kilometers and/or fire on a target that is accelerating or manouvering in general hitting might be a problem.

-speed. a good cannon might get the projectile up to 1800m/s. intercepting a target moving faster than that relative to your ship is only possible if it moves towards you.

-gyro stabilisation. to impact in the correct orientation without active steering you need to gyrostabilize the shell. fin stabilization doesent work in a vaccum. this isnt a huge issue, but it requiers rifled barrels.

pros to cannons in space:

-cost. in a world where we have advanced production and mining capabilities in space steel will be abundant in orbit as the iron is pretty common in asteroidds we mine. cannons expend little "advanced" materials and can be produced entirely from steel, chrome, nickel and a little carbon, all of which are easy to mine. both the cannon and its ammo can be produced with pretty crude production facilities.

- interceptability. a tungsten rod moving towards you is close to impossible to stop.

-damage. a laser is pretty nice at range, but within the range of a cannon it deals a pretty hard blow, penetrating everything that isnt extremely heavily armoured.

-accuracy. although a cannon has miserable accuracy compared to a guided missile, it has a great accuracy in space. since you are fiering in a microgravity enviroment it is effectivly shooting in a straight line, removing the issues of wind conditions and dropoff from gravity.

here is a mock up of a cannon and a sabo shell.

cannon length: why so short cannon? well, in space you get a slight boost to power since there is a vaccum on the outside. also, a long cannon is heavy, and weight is a huge concern, even in sci fi. if the barrel doubbles the weight, why not half the length and get 50% more cannons?. a recoilless rifle could be better due to it not affecting the orbit, but it would restrict loading and then also the combat eficciency of the ship.

i'm no engineer, so lots of stuff is overdimentioned or underdimentioned, but the bore diameter is on purpose. a huge bore helps with the short barrel length. the sabo round would be burried deep inside the cartridge/shell in a perforated flash tube surrounded by solid fuel, so the barrel is effectively a little longer than it looks since the projectile starts further back.

i havent covered the autoloader here (it obviously cant be manually loaded), but i imagine it being an arm that lifts the new shell up to the cannon while catching the remainder of the spent shell for storage (we dont want unnessecary debris do we?).

ammo:

the obvious choice for a cannon on a space warship is a heavy penetrator projectile as it is the hardest to intercept (if you use a shape charge, why not just use a missile? you loose some penetration ability and a lot of survivability for the projectile. versus a hardned, armoured target you would obviously prefer a tungsten penetrator, but that is hard to get and is maybe unnecessarily heavy. hardned steel should do.

the sabo doesent have to be discarding since its only job is to accelerate the projectile and there is no air resistance. the sabo would have to be made from mild steel, aluminium, copper, lead or maybe tin. it just needs to be able to gyrostabilize the whole projectile. the sabo should discard on impact, if it stayed with the penetrator it would defeat the purpose of a penetrator.

i might have overdimentioned the penetrator a tad, it could probbably do with being a lot smaller.

i'm not covering the turret this would be mounted on either as that is common amongst most sci fi weapon systems.

[sal_vager]

I'd like to add to this the issue of heat, heat dissipation is a real problem in space where there is no atmosphere to allow for convection, all heat dissipation is via radiation.

I bring this up because directed energy weapons will generate a lot of heat which has to be removed, radiative heating would be slow and having a store of gas to pass over the hot elements of a laser to then dump into space would limit the number of times the laser could be used.

A mechanical weapon with solid projectiles would not get anywhere near as hot, even the heat from a heavy machine gun barrel in space would be manageable, so having to deal with heat from such a weapon would not be a concern.

Of course, an energy weapon would dump a lot of heat into your target, but a tank round can also cause a lot of thermal trouble to whatever it hits due to the extreme velocity of the impact.

[ravener]

I'd like to add to this the issue of heat, heat dissipation is a real problem in space where there is no atmosphere to allow for convection, all heat dissipation is via radiation.

I bring this up because directed energy weapons will generate a lot of heat which has to be removed, radiative heating would be slow and having a store of gas to pass over the hot elements of a laser to then dump into space would limit the number of times the laser could be used.

A mechanical weapon with solid projectiles would not get anywhere near as hot, even the heat from a heavy machine gun barrel in space would be manageable, so having to deal with heat from such a weapon would not be a concern.

Of course, an energy weapon would dump a lot of heat into your target, but a tank round can also cause a lot of thermal trouble to whatever it hits due to the extreme velocity of the impact.

the heat from the cannon is easilly dissapated with some heat pipes, the issue at the recieving end however are pretty dire as it is concentrated on a pretty small area. it it was to hit a fuel tank it would not only vent the fuel, but also bring a large amount of it to quite high temperatures. if it hits the crew compartment (assuming there is one) the overpreassure would be the greater problem, that would probbably also rupture any liquid holding tanks when i think about it.

EDIT:

it also turns out that a cannon is an eficcient way to accelerate a projectile. it is lighter, cooler, more reloadable and more reliable than a railgun and a LOT cooler than a laser (temperature).

Edited May 26, 2014 by ravener

[rtxoff]

What about the propulsion method of the projectile? How are you going to accelerate it. Conventional gun powder is hard to use, u need oxygen for it to burn, also it creates gases what to do with them?

Not sure about some other modern projectile propellants if they need oxygen.

[sal_vager]

ravener, heat pipes do not make heat go away in space, they only move it, likely to a waste heat array but it still has to be removed from a vessel by radiation.

[ravener]

What about the propulsion method of the projectile? How are you going to accelerate it. Conventional gun powder is hard to use, u need oxygen for it to burn, also it creates gases what to do with them?

Not sure about some other modern projectile propellants if they need oxygen.

propulsion method is smokeless gunpowder. current tech. it works great in space, all the oxygen is contained in the gunpowder. how do you think oxygen from the atmo would get into the reaction in a rifle? a regular earth gun would work great in space, a glock or 1911 in space? no problem. also, "what to do with the gasses?" uh... accelerate a projectile?

ravener, heat pipes do not make heat go away in space, they only move it, likely to a waste heat array but it still has to be removed from a vessel by radiation.

you could transfer the heat into the hull ( probbably mild steel, we are talking about a warship here), the heat would be radiated by the hull and/or would be stored there.

[sal_vager]

The hull still needs to remove that heat or it'll build up, remember there are volatiles (fuel) and perishables (crew) in there, also delicate electronics.

It'll still need to be radiated to space.

[Jouni]

As a rough guideline, weapons (or actually their delivery mechanisms) are about as powerful as the means of propulsion, no matter whether we are speaking about triremes, jet fighters, or spaceships. As long as we can harness more energy without making the design too expensive or unwieldy, and without getting into trouble with waste heat, structural integrity, or similar stuff, we can use that energy to get more powerful engines and weapons.

[ravener]

The hull still needs to remove that heat or it'll build up, remember there are volatiles (fuel) and perishables (crew) in there, also delicate electronics.

It'll still need to be radiated to space.

i dont think the heat from the cannon would be the issue. if you ship can handle sunheating it can handle the small amount of heat from the cannon. imagine 100+tonnes of steel armour on a sizable warship, you could dump a lot of heat into that before it becomes an issue. in short, any ship should have the heat dissapation capabilities to handle a cannon, even ISS could probbably handle it with its radiators.

As a rough guideline, weapons (or actually their delivery mechanisms) are about as powerful as the means of propulsion, no matter whether we are speaking about triremes, jet fighters, or spaceships. As long as we can harness more energy without making the design too expensive or unwieldy, and without getting into trouble with waste heat, structural integrity, or similar stuff, we can use that energy to get more powerful engines and weapons.

depends. a hellfire missile mounted on a WW2 aircraft is pretty destructive, almost as much as when mounted on an attack chopper.

Edited May 26, 2014 by sal_vager

[sal_vager]

I was talking about the heat from a laser or similar directed energy weapon, that'd be considerably greater than any conventional armament, it is an argument in favour of projectile weaponry over fancy lasers.

And a vessel would still need to dissipate the heat from the sun, as well as heat from on-board systems, crew, engines and everything else, so I'd expect a warship to have some funky armoured radiators on the back regardless of what weapons it employed

[ravener]

I was talking about the heat from a laser or similar directed energy weapon, that'd be considerably greater than any conventional armament, it is an argument in favour of projectile weaponry over fancy lasers.

And a vessel would still need to dissipate the heat from the sun, as well as heat from on-board systems, crew, engines and everything else, so I'd expect a warship to have some funky armoured radiators on the back regardless of what weapons it employed

we are in agreement then.

[Jouni]

depends. a hellfire missile mounted on a WW2 aircraft is pretty destructive, almost as much as when mounted on an attack chopper.

The entire weapon system would be much worse than a modern aircraft armed with Hellfire missiles. Warships and combat aircraft are generally designed to be bigger, better, faster, and more powerful, until the designers (almost) run into some kind of trouble.

[Seret]

The hull of a spacecraft probably can't offer much help as a heat sink. It won't be hundreds of tonnes of steel, spacecraft need to be optimised for weight. You'd need to send your heat to radiators.

You won't be getting bigtime heat problems from a gun though. Most of the heat is carried away by the has you vent it the muzzle, and I don't think it's likely that an engagement would require a lot of shots. One hit from any gun larger than about 40mm is going to be curtains for anything in orbit.

[ravener]

The entire weapon system would be much worse than a modern aircraft armed with Hellfire missiles. Warships and combat aircraft are generally designed to be bigger, better, faster, and more powerful, until the designers (almost) run into some kind of trouble.

but the weaponsystem itself is what is in question here. a spaceship with catapults is useless, doesent matter how advanced it is. the weapon system has to match the capabilities of the vihecle.

[ravener]

The hull of a spacecraft probably can't offer much help as a heat sink. It won't be hundreds of tonnes of steel, spacecraft need to be optimised for weight. You'd need to send your heat to radiators.

You won't be getting bigtime heat problems from a gun though. Most of the heat is carried away by the has you vent it the muzzle, and I don't think it's likely that an engagement would require a lot of shots. One hit from any gun larger than about 40mm is going to be curtains for anything in orbit.

if is issupposed to be a warship it needs armour of some sort, most likely a mix of thermal (insulation against lasers) and steel armour. we are talking sci fi here, so propulsion might not be an issue. steel armour of almost ANY thickness is an effective heatsink, the mass of the hull wil almost ALWAYS be higher than the weapons it mounts. if the hull is twenty times the weight of the cannon, it can store twenty times more heat than the cannon alone and it could just be a buffer so the radiators can "suck" the heat out later. the heat issue isnt so bad though, i think we agree there, the penetrator can be pretty small, the bore diameter is just so we can get away with a shorter gun.

Edited May 26, 2014 by ravener

[Red Iron Crown]

The barrel of your mockup cannon is absurdly short, most of the propellant's energy will be wasted after the projectile leaves the barrel. There's a reason longer barrels are preferable, especially as engagement ranges increase.

What sort of targets are you planning to attack with the cannon?

[ravener]

The barrel of your mockup cannon is absurdly short, most of the propellant's energy will be wasted after the projectile leaves the barrel. There's a reason longer barrels are preferable, especially as engagement ranges increase.

What sort of targets are you planning to attack with the cannon?

spaceships. armour thicknesses are probbably not that high as heavy armour isnt really useful in space. i know it is extremely short, that's why it's so thick, so it accelerates fast in the little time it has. the model i made is not that important though, it could easilly have multiple times longer barrel, i am just saying that a long barrel might not be the best in space combat where fast gimballing might mean life or death as engagement times are very short.

[ravener]

note that on a space ship a cannon of this size would be akin to a naval cannon on a battleship. 20mm autocannons would be extremely dangerous, but a pennetrator from a 400mm cannon is nothing to joke about. this is a weapon that would take almost anything down in one or two shots.

[sal_vager]

You'd only need one of those guns, as the craft could just turn to face any angle required, you could even fire at a target on the other side of a planet as the projectile would just orbit around till it hit.

Stealth cannon projectiles would be the in thing.

[xenomorph555]

The soviets already had a space cannon, it was mounted on the almaz 2 military station. In addition they had a variant of the soyuz that had machine guns.

[Seret]

if is issupposed to be a warship it needs armour of some sort

Why? Do aircraft have armour (well, they do, but very small amounts of it). Spacecraft, like aircraft, need to be designed for minimum weight, and would be facing similar threats to aircraft so would be highly likely to use similar solutions for protection.

If you want to know what combat spacecraft would look like, don't think of naval vessels in space, think of actual current spacecraft but with weapons. Less starship Enterprise or Macross and more Soyuz with guns.

[Red Iron Crown]

Stealth cannon projectiles would be the in thing.

How could you hide the heat transferred from the propellant to the projectile? It would stick out like a sore thumb on IR.

[ravener]

here is the cannon model with a slightly longer barrel (about 3x barrel length )

[sal_vager]

How could you hide the heat transferred from the propellant to the projectile? It would stick out like a sore thumb on IR.

Well Red, if you are on one side of the planet and your target is on the other, he's not going to see your plume and the projectile will have time to cool down

[ravener]

Why? Do aircraft have armour (well, they do, but very small amounts of it). Spacecraft, like aircraft, need to be designed for minimum weight, and would be facing similar threats to aircraft so would be highly likely to use similar solutions for protection.

If you want to know what combat spacecraft would look like, don't think of naval vessels in space, think of actual current spacecraft but with weapons. Less starship Enterprise or Macross and more Soyuz with guns.

this is [sCI FI THEORY]. a ship built for combat has to be able to survive combat. if autocannons, misslies and lasers are the weapons of a given sci fi setting you need ships that can handle some amount of pummeling.

Edited May 26, 2014 by ravener
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