cannons in space

[Seret]

I can't imagine a lot of heat transfers to the projectile during the short time the gases are acting on it. Less if they're acting on a sabot instead of the baseplate.

[ravener]

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.

yes, it has been mentioned. it was never used in combat though (obviously) so it would be interresting to see how effective it would be.

[Red Iron Crown]

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

That's a good point about the planet obstructing the plume, but where would the heat in the projectile go?

Edit: Seret made a good point about sabots, but why would one use a sabot on an orbital projectile? And wouldn't the discarded sabots follow almost the same course as the projectile?

[ravener]

I can't imagine a lot of heat transfers to the projectile during the short time the gases are acting on it. Less if they're acting on a sabot instead of the baseplate.

it probbably gets pretty hot from friction, but you could always cool the projectile some before fiering and discard some of the hot sabot.

That's a good point about the planet obstructing the plume, but where would the heat in the projectile go?

space. cold projectile in the first place, many options.

[sal_vager]

Heat from the projectile is also radiated to space over time, if you're too close for that then the velocity of the projectile would not only be too high for your target to avoid (hopefully) he's also already know you're there, so hiding the shots wouldn't be an issue.

[Seret]

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.

Do aircraft need thick armour to resist autocannons, missiles and lasers?

This may be "Sci Fi Theory" but that doesn't mean we have to drop the "sci" and instead think like TV scriptwriters. Minimising weight is a fundamental principle of spacecraft design, you can't ignore it.

[ravener]

i dont think a cannon would be accurate enough to reliably hit a target on the other side of the planet, i dont even think it is accurate enough to go out to distances where orbit even matters in the trajectory calculation (okay, maybe a little.) at a maximum i would guess it could reliably hit something out to 100km with a long barrel and a static (ish) target in relation to the fiering ship.

[Seret]

but why would one use a sabot on an orbital projectile? And wouldn't the discarded sabots follow almost the same course as the projectile?

Yes, and there's no real need to minimise projectile cross-section either (the main reason to use a sabot). Larger calibre explosive projectiles with smart fuses would be more effective than KE penetrator rounds.

[ravener]

Yes, and there's no real need to minimise projectile cross-section either (the main reason to use a sabot). Larger calibre explosive projectiles with smart fuses would be more effective than KE penetrator rounds.

planes rely on countermeasures, there is very little you can do when a 250kg tungsten penetrator is hurteling towards you from a capital ship main cannon.

[sal_vager]

i dont think a cannon would be accurate enough to reliably hit a target on the other side of the planet, i dont even think it is accurate enough to go out to distances where orbit even matters in the trajectory calculation (okay, maybe a little.) at a maximum i would guess it could reliably hit something out to 100km with a long barrel and a static (ish) target in relation to the fiering ship.

There's nothing to perturb the projectile though ravener, and if the force of the shot is known, which it would be, and the orbit of an unsuspecting target was known a firing solution can be calculated so the orbits of the shot and the target intersect.

Also, buckshot

[ravener]

Yes, and there's no real need to minimise projectile cross-section either (the main reason to use a sabot). Larger calibre explosive projectiles with smart fuses would be more effective than KE penetrator rounds.

but it is way easier to counter, the small crossection is to better penetrate the hull of an enemy ship and i dont advocate a discarding sabot, it could stay with the penetrator until impact where the penetrator leaves the sabot behind.

[ravener]

There's nothing to perturb the projectile though ravener, and if the force of the shot is known, which it would be, and the orbit of an unsuspecting target was known a firing solution can be calculated so the orbits of the shot and the target intersect.

Also, buckshot

but i dont think the powder would burn accurately enough or the barrel be precise enough for more than some tens to maybe a few houndred kilometers.

[Red Iron Crown]

I'm starting to think missiles are better than cannon rounds. Recoil becomes a non-factor, heat almost so, plus it can carry its own sensors and course correct if the target tries to dodge.

[ravener]

I'm starting to think missiles are better than cannon rounds. Recoil becomes a non-factor, heat almost so, plus it can carry its own sensors and course correct if the target tries to dodge.

but if they arent kinetic impact weapons they are counterable, they are also a lot more expensive and harder to make in a crude ish space factory where the mills and 3d printers only go down to a few houndreds of a mm.

[sal_vager]

Kinetic energy missiles exist, how much guidance would something like this need do you think?

[ravener]

Kinetic energy missiles exist, how much guidance would something like this need do you think?

but they still need propulsion in flight. if the engine/fuel tank was to be damaged or ruptured it would probbably not hit its target.

[Seret]

but it is way easier to counter, the small crossection is to better penetrate the hull of an enemy ship

You just aren't going to see bulk armour on spacecraft any time when you're working against the rocket equation. You might get some minimal armour to more critical parts but in general your target is going to be made largely of aluminium and have vulnerable things like solar arrays, antennas, and maneuvering thrusters sticking out of it. HEI and proximity fused fragmentation warheads would be much more deadly than penetrators.

[sal_vager]

That'd be a very difficult thing to achieve (hitting the propulsion/tank), and if you fired more than one then you improve your odds of hitting considerably.

[Dodgey]

Firstly we need to establish the basics of your spacecraft and who you are fighting. That way we can design a weapons system to take it out, otherwise we are just takeing shots in the dark here.

[Seret]

but they still need propulsion in flight. if the engine/fuel tank was to be damaged or ruptured it would probbably not hit its target.

Any projectile (including KE ones) would be unlikely to hit the target if it was intercepted.

[Red Iron Crown]

It's a mistake to discard the sabot on impact, better to have its kinetic energy added to the penetrator; the narrowness of the penetrator is only really relevant for atmospheric rounds where drag is a factor.

I don't really see how kinetic impactors aren't counterable, ranges in space are long so there is time to maneuver out of a collision course with one assuming some modicum of mobility in the target.

[Awaras]

I'm starting to think missiles are better than cannon rounds. Recoil becomes a non-factor, heat almost so, plus it can carry its own sensors and course correct if the target tries to dodge.

Well, you could use a cannon round with an active RCS system so it can correct it's course slightly during flight. But yes, missiles would probably be preferable.

As for the "armor on a spaceship" discussion, if a round such as the one discussed here hits the spacecraft, armor will not be very helpful. I believe that the best course of action would be to use armor around strictly limited areas of the ship (the "bridge" and other critical areas) and focus on lowering the mass and increasing the maneuverability and sensor capacity of the ship.

After all, if you are able to detect a dumb fire projectile heading your way all you need to do in order to avoid it is move a few meters in a random direction.

[ravener]

You just aren't going to see bulk armour on spacecraft any time when you're working against the rocket equation. You might get some minimal armour to more critical parts but in general your target is going to be made largely of aluminium and have vulnerable things like solar arrays, antennas, and maneuvering thrusters sticking out of it. HEI and proximity fused fragmentation warheads would be much more deadly than penetrators.

most sci fi has some sort to compact, high power, high isp engine. in one setting it is stutterwarp, in another it's antimatter drives. aleredy now we can effectively counter most explosive based weapons (HEAT rounds and missiles) if we really wanted. the russians have a system that detonated the incoming warhead in flight with a shapecharge. if we can do it now we can probbably do it not far in the future.

Edited May 26, 2014 by ravener

[Seret]

the narrowness of the penetrator is only really relevant for atmospheric rounds where drag is a factor.

It helps with that, but the main reason for small cross-section penetrators is to maximise the local stresses at the point of impact. Generally speaking KE penetrators defeat the target by plastic deformation of the armour. Stress is force over area, so a smaller diameter penetrator will result in higher stress in the target for a given force.

KE penetrators have only evolved because armour on tanks got so thick that explosive rounds were no longer effective. Against anything with less armour than that (which is everything short of a main battle tank) you're still better off using an explosive warhead. Against the kind of construction seen in aerospace vehicles fragmentation warheads like a continuous rod are proven to be extremely effective.

[ravener]

It's a mistake to discard the sabot on impact, better to have its kinetic energy added to the penetrator; the narrowness of the penetrator is only really relevant for atmospheric rounds where drag is a factor.

I don't really see how kinetic impactors aren't counterable, ranges in space are long so there is time to maneuver out of a collision course with one assuming some modicum of mobility in the target.

the sabot is still hitting the ship, it woul probbably still penetrate the hull, but the penetrator would continue going when the sabot stops. countering a kinetic impact weapon is a lot harder than an explosive round, for that you just need a little heat. with a KE weapon you need to physically intercept the round with enough force for it to either miss or no longer have enough force to be an issue.