cannons in space

[Gordon861]

If you want to fire a cheap and simple round at a target in space why not go the whole hog and use a rail gun? The ammo is very low tech and all you need is the means to generate electricity to fire it.

[ravener]

If you want to fire a cheap and simple round at a target in space why not go the whole hog and use a rail gun? The ammo is very low tech and all you need is the means to generate electricity to fire it.

heat, power requirements, rare metals, hard to produce the caps in orbit, and it's heavy. lots of issues. it is pretty powerful though, but if a 400mm cannon is overkill, almost any railgun would be too.

[sal_vager]

I'm not convinced railguns are all that great, the gun itself is very complex and expensive, requires ridiculous amounts of power and like a directed energy weapon it'll generate a lot of heat, that power to the magnetic coils has to go somewhere and not all will be transferred to the projectile.

One reason for the development of railguns is the inordinate range they can offer in a atmosphere, this is not a factor in space.

[ravener]

this is the setting/feel

we have the engines to move heavy armour, how are we going about penetrating that armour?

[sal_vager]

Cruise missiles, with solid metal warheads that are propelled by shaped explosive charge an instant before impact as there's no atmosphere to transfer the energy of a normal explosive.

Or high velocity kinetic projectiles, in large numbers.

[Scotius]

Cannons in space? Well...think about how much you are complicating things for engineers. First of all: this cannon will be big, heavy, and will create huge structural stress every time it fires. It will require considerable amounts of explosives, which will have to be stored in secure compartment. And it will have to be put some distance from the cannon - explosives generally don't like to be stored next to a source of heat and frequent shockwaves. Which means cannon-armed spaceship will require transportation system for its ammo - secure of course. All of it means more mass, space and complexity of the design. There is a reason modern warships generally carry one medium-sized, universal, automatic cannon, and couple rapid firing, fast-tracking small caliber cannons as point defence weapons. When a ship needs to kill another ship, it will be done using aircraft (if available), then guided missiles - with cannons being used only as a weapons of last resort. Or against a target that is worth less than a bomb or guided missile. No one will shoot Harpoons or Tomahawks at Somali pirates O

There is also the small issue of barrel longevity Each shot degrades the barrel. Degraded barrel is less precise and more dangerous - keep firing, and it will finally explode. If you want to avoid this...well, go back to shipyard. There your cannon mount will be at least partially disassembled, old barrel removed, new one put in place. Then new barrel will have to be calibrated, properly tested (which means live firing, which starts the process of degradation ) - it's a long, time and workhour consuming process. Like i wrote - there are many reasons why modern warships no longer use cannons as primary armament.

[ravener]

lasers are out of the picture due to extremely low eficciency when it comes to penetrating anything. railguns, maybe, but they get kinda hot and require a lot of energy aka lots of bang, extreme buck. missiles are easy to counter with the weak point defence lasers we have and some time fuse flak cannons. we need something with moderate to high penetration abilities that we can make many of cheaply and operate on lowish power (they can use quite a bit, but lots of capacitors arent really wanted in space).

[Red Iron Crown]

If you have the engines to move that, the engines are the weapon. Remember the Kzinti lesson.

Edited May 26, 2014 by Red Iron Crown

[sal_vager]

the engines are the weapon.

:/

Of course! A properly made de lavel nozzle should give you a pretty tight stream of exhaust gasses, as shown in this pic, and that could be used as a weapon.

Actually, that reminds me of the PBC's from Independence War.

[ravener]

Cannons in space? Well...think about how much you are complicating things for engineers. First of all: this cannon will be big, heavy, and will create huge structural stress every time it fires. It will require considerable amounts of explosives, which will have to be stored in secure compartment. And it will have to be put some distance from the cannon - explosives generally don't like to be stored next to a source of heat and frequent shockwaves. Which means cannon-armed spaceship will require transportation system for its ammo - secure of course. All of it means more mass, space and complexity of the design. There is a reason modern warships generally carry one medium-sized, universal, automatic cannon, and couple rapid firing, fast-tracking small caliber cannons as point defence weapons. When a ship needs to kill another ship, it will be done using aircraft (if available), then guided missiles - with cannons being used only as a weapons of last resort. Or against a target that is worth less than a bomb or guided missile. No one will shoot Harpoons or Tomahawks at Somali pirates O

There is also the small issue of barrel longevity Each shot degrades the barrel. Degraded barrel is less precise and more dangerous - keep firing, and it will finally explode. If you want to avoid this...well, go back to shipyard. There your cannon mount will be at least partially disassembled, old barrel removed, new one put in place. Then new barrel will have to be calibrated, properly tested (which means live firing, which starts the process of degradation ) - it's a long, time and workhour consuming process. Like i wrote - there are many reasons why modern warships no longer use cannons as primary armament.

most explosives handle shock pretty well, and if it blows, so what? it just vents into space, no overpreasure to worry about. the structural stress is minimal as we can fit pretty large shock absorbers on this, there is no loader behind it to not kill. since the bore is so large pressures can be lower and the cannon can last practically forever. warships are also known for needing constant logistics support, i suspect this would be the case in space as well as a compact ship is favorable due to heating issues and to not be a huge target. i am working on the assumption that we are using some advanced propultion system so fuel isnt an issue, so ammo storage isnt really an issue.

[Seret]

If you have the engines to move that, the engines are the weapon. Remember the Kzinti lesson.

This.

Falling that, you can't beat a sunbomb for cracking unrealistically large space vehicles.

[Red Fang]

This was going to be a very long post, but I'll have to cut it short.

Due to high complexity of defensive systems on current armored vehicles and aircraft, as well as (semi-)autonomous avionics, dumb kinetic weapons stand little chance of hitting a target at "long" ranges in space. Say 10-100km ~5-50s flight time. At that range they can be intercepted by similar weapons and at shorter ranges they could be defeated with smart active defensive systems in a reasonable number of cases. The lower the number of projectiles to deal with, the more likely the defensive system will counter them in an efficient manner, by deflecting their trajectory. Given the low resistance of passive armor on a potential spacecraft to kinetic weapons, (probably in the class of aircraft armor or light IFV armor at best) any decent size of ammo will do enough damage. 30mm is probably an overkill. Therefore, a space gun needs and probably can achieve high rate of fire, fast tracking and be a good defensive weapon at ranges up to 100km and a serious damage dealer at somewhat shorter ranges. given the different tasks such a weapon may perform it will probably have a large variety of munitions available for quick selection.

Imagine an autonomous turret, fireing anywhere from 1200 to 2400 RPM at 2000 m/s. With ammo in at least these varieties

- DU kinetic penetrators, for "big" targets, such as armored ships and large caliber projectiles.

- Semi-smart fragmentation ammo akin to modern AA rounds of same caliber.

- Shot (DU, W, even steel) for covering large areas

Than as to the OP large caliber projectiles.

Anything comparable to 100mm caliber and above can be deployed with its own propulsion or from a recoil less riffle more easily, and with less weight penalty. Also, such munitions can not achieve any great rate of fire, and therefore every round counts, making it feasible to make all munitions smart munition and to experiment with different charges.

-Self guided rockets and rounds that keep themselves oriented in line with a firing solution to the target may be used as shaped charges. Shaped charges may form either a jet of metal, or an explosively formed penetrator that looks more like a solid slug. An EFP may exceed 10km/s so detonating a warhead some 10-20km away from target may actually hit it from a distance and deal terrific damage, even if the EFP deforms to a high degree in flight. Remember, we are essentially targeting a something that is probably weaker than an aircraft, not a tank. If these munitions are smart enough, they will detect, evade and detonate before being hit by defensive fire.

- Directed fragmentation/flak shells (imagine a shell designed as a claymore mine) detonating before being hit with flack will rip apart most unarmored components.

- Smart cluster munitions/missiles with smart or semi-smart sub munitions combining all munition types above in a single warhead.

Do not forget that for a ton of hypergorlic rocket with all the bells and whistles you can get ~4-5km/s delta-V and a decent payload of about 100-200kg on target, comprising of anywhere from 50 to 400 smart submunitions. HOW do you counter that? A high caliber gun will probably be able to fire 4-10 round during an engagement and will not weigh less than 10t with ammo. At that weight you are better off with smart missiles.

I see space combat with kinetic/explosive weapons as smart guns shooting smart munitions at smart munitions shot by smart guns/rockets, while everyone is trying to blind the other guy's optics with lasers and gas and crews only making decisions shoot/not shoot.

If they don't get disabled/fried by lasers at long range first...

EDIT:

Oh yeah. Thanks for mentioning The Kzinti Lesson. And Casaba(sp?) howitzers.

Edited May 26, 2014 by Red Fang

[rtxoff]

Trying to blind the enemy with lasers is probably a bad idea, why do you think that the enemys sensors work in the same wavelength like yours?

They could be calibrated for any wavelength while we are going to hit them only on one wavelength at the time with one laser. Hitting the right electromagnetic wavelength is gonna be a lottery.

So no blinding with lasers please.

[Red Fang]

Makers sense. I should have done a better research on that.

I stand corrected.

[ravener]

the 100+km range is what i would call the EXTREME maximum for even hitting a target of decent size. i would choose missiles on ranges higher than 10-30km due to the higher hit probbability. the cannon only really shines on ranges within 20km, optimally closer than 10km since the target would have little to no time to detect the projectile and deploy counters. the only counters that can really be deployed at short notice cant really deal with high density penetrators.

Edited May 26, 2014 by ravener

[Vanamonde]

I'm surprised that the discussion has gone on this long without anyone raising the biggest obstacle, which is simply hitting the target.

As far back as World War I, military engineers and scientists began to realize that you could pound an area with hundreds or even thousands of artillery shells, and when it stopped, most of the enemy would still be alive to pop back out of their bunkers and shoot at your attacking troops. In WW2, only a fraction of all the bombs dropped from aircraft actually got close to their intended targets, and even fewer actually hit the target. They were already working on smart weapons during WW2 itself, such as tv-guided drone planes. The reason militaries have switched to guided weapons is that, even though they are far more expensive per-unit, they are less expensive in the long run because you might only need to fire one of them to do the same job as dozens or hundreds of dumb projectiles.

And that's just the situation when firing at a large target that is sitting still, like a bridge or a factory. If the target is maneuvering at all, the only situations in which it makes sense to use dumb projectiles is if the time-to-target is short enough that the target will not have moved much by the time the projectile arrives (naval canon), or if you're firing a large number of projectiles and trusting to probability that at least some will hit (which is what fighter planes do). But notice that even in those instances, the limited range of the guns means that they are usually used as a last resort after missile supplies have been exhausted or range is under the missile's minimum.

And given the scale of the distances involved in spaceflight, it's hard to imagine a situation in which the target is still going to be at the aim point when a canon shell arrives. If the enemy is aware of your presence, it would be suicidal of him not to be jinking, in which case you'd be wasting a great deal of your finite supply of large canon projectiles as you try to hit him.

In short, it seems to me that the only way to effectively use dumb projectiles is to blanket the cone-volume of possible target positions with something like either machinegun bullets or shotgun pellets. By comparison, a missle, while more complex and larger, is likely to cross the distance faster and can make course corrections along the way, both of which make a hit more likely. If you can only carry a few large weapons, you'd be much better off choosing a few dozen guided missiles over a few score canon shells. This is, after all, the conclusion modern navies have reached.

[ravener]

I'm surprised that the discussion has gone on this long without anyone raising the biggest obstacle, which is simply hitting the target.

As far back as World War I, military engineers and scientists began to realize that you could pound an area with hundreds or even thousands of artillery shells, and when it stopped, most of the enemy would still be alive to pop back out of their bunkers and shoot at your attacking troops. In WW2, only a fraction of all the bombs dropped from aircraft actually got close to their intended targets, and even fewer actually hit the target. They were already working on smart weapons during WW2 itself, such as tv-guided drone planes. The reason militaries have switched to guided weapons is that, even though they are far more expensive per-unit, they are less expensive in the long run because you might only need to fire one of them to do the same job as dozens or hundreds of dumb projectiles.

And that's just the situation when firing at a large target that is sitting still, like a bridge or a factory. If the target is maneuvering at all, the only situations in which it makes sense to use dumb projectiles is if the time-to-target is short enough that the target will not have moved much by the time the projectile arrives (naval canon), or if you're firing a large number of projectiles and trusting to probability that at least some will hit (which is what fighter planes do). But notice that even in those instances, the limited range of the guns means that they are usually used as a last resort after missile supplies have been exhausted or range is under the missile's minimum.

And given the scale of the distances involved in spaceflight, it's hard to imagine a situation in which the target is still going to be at the aim point when a canon shell arrives. If the enemy is aware of your presence, it would be suicidal of him not to be jinking, in which case you'd be wasting a great deal of your finite supply of large canon projectiles as you try to hit him.

In short, it seems to me that the only way to effectively use dumb projectiles is to blanket the cone-volume of possible target positions with something like either machinegun bullets or shotgun pellets. By comparison, a missle, while more complex and larger, is likely to cross the distance faster and can make course corrections along the way, both of which make a hit more likely. If you can only carry a few large weapons, you'd be much better off choosing a few dozen guided missiles over a few score canon shells. This is, after all, the conclusion modern navies have reached.

you do realize that hitting a 3m x 3m target at 2km with a tank shell today is almost trivial right? accuracy has improved greatly since WW1 with better manufacturing and advanced electronics. hitting something larger than 20m x 20m in microgravity conditions with no windresistanse on ranges over 10km seems quite possible.

[rtxoff]

you do realize that hitting a 3m x 3m target at 2km with a tank shell today is almost trivial right? accuracy has improved greatly since WW1 with better manufacturing and advanced electronics. hitting something larger than 20m x 20m in microgravity conditions with no windresistanse on ranges over 10km seems quite possible.

Nope it is not, you are forgetting that most probably you will be on some orbit eventually travelling few thousands m/s around some body. It will be challenge to get so close to the target. This is going to be a fight of who has the better targeting computer intercepting the enemy earlier and also who is doing the better evasive maneuvers while approaching to the target. This all is not as easy as most of you guys think. Because cannons are pretty lowtech your winnig card is more computing power, eventually an AI.

Edit: also moar booooosters could help for better evasive maneuvers

Edited May 26, 2014 by gpisic

[ravener]

i think we have mostly agreed that the effective range of this is between 20-50km (i mentioned 100km, but that is with a large, stationary target at EXTREME range), anything over that is streaching what is even possible with an unguided projectile. i also think i mentioned that the theme is more

than apollo, i dont know if that counts as anything, but i'm going with hulks slugging it out with relative velocities around 200m/s. think battleships in space.

[Seret]

i'm going with hulks slugging it out with relative velocities around 200m/s. think battleships in space.

Is there any particular reason you've chosen that particular cutoff? Other than that it makes the kind of engagement you want to talk about possible?

[ravener]

Is there any particular reason you've chosen that particular cutoff? Other than that it makes the kind of engagement you want to talk about possible?

i might just misunderstand [sCI FI THEORY] then, there is so much sci fi to choose from and since Dodgey asked me

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.

i chose the huge lumbering ships and wondered how suited cannons would be in this situation.

feel free to correct me if i have misunderstood.

[Vanamonde]

you do realize that hitting a 3m x 3m target at 2km with a tank shell today is almost trivial right?

Modern tank combat takes place at ranges of a mile or so, which the projectiles cross in less than 1 second. Since tanks can not move at their top road speed when moving across uneven ground, this means that the target is, for practical purposes, nearly sitting still. So as I said, canons are still practical weapons if the time-to-target is quite short.

I also find highly questionable your stipulations that space combat would be between battleships at ranges of a few kilometers. There's a reason no one has built battleships in over 60 years; aircract and missiles can hit battleships long before battleship guns can hit back. That principle would hold true in space combat as well. Also, with modern guided weapons and innovations such as shaped charges, speed and maneuverability are better defenses than bulk and armor. If you do wish to limit the discussion to capital ship exchanges at fairly short range, then canons might indeed be the best choice, but that is a very arbitrary limitation and not likely to reflect future combat in space.

[ravener]

Modern tank combat takes place at ranges of a mile or so, which the projectiles cross in less than 1 second. Since tanks can not move at their top road speed when moving across uneven ground, this means that the target is, for practical purposes, nearly sitting still. So as I said, canons are still practical weapons if the time-to-target is quite short.

I also find highly questionable your stipulations that space combat would be between battleships at ranges of a few kilometers. There's a reason no one has built battleships in over 60 years; aircract and missiles can hit battleships long before battleship guns can hit back. That principle would hold true in space combat as well. Also, with modern guided weapons and innovations such as shaped charges, speed and maneuverability are better defenses than bulk and armor. If you do wish to limit the discussion to capital ship exchanges at fairly short range, then canons might indeed be the best choice, but that is a very arbitrary limitation and not likely to reflect future combat in space.

once again, this is sci fi, so i was burdoned with selecting the setting the weapon is set in. also, the effective range of an L55 rheinmetall cannon is 4000m, hitting something at twice the range without the limitation of gravity seems reasonable. there are reasons to use bettleship sized ships, mostly the cargo capacity and more surface to mount countermeasures on.

[Nuke]

i dont think a sabot would be neccisary in space. you usually use them where you have a finned projectile designed for atmospheric use. there is no air resistance, so using a wider, shorter shell is less of an issue.

i would also use a recoilless design where the end of the barrel is open and counter mass is expelled to reduce the overall recoil of the cannon. your round is essentially a tube, with a shell coming out of one end and a wad of counter mass, usually compressed wad of metal foil at the other end, and two or more times the usual powder charge. the foil is of a metal with a low vapor point, it vaporizes on its way out the back end, while the shell goes in the other direction. this is to minimize the damage zone behind the gun.

[Plebian]

I would assume any 'cannon' would likely be a light gas gun of some type. http://en.wikipedia.org/wiki/Light_gas_gun