Use of Nuclear Artillery in space combat

[Connor MacLeod]

Is there some reason you can't be using shaped charge nukes or some sort of bomb pumped x-ray laser warhead?

[Starglider]

Is there some reason you can't be using shaped charge nukes

Those work by heating up a lot of driver material into a conical spray of plasma. Firstly that adds a lot of mass to the warhead. Secondly it still disperses quite rapidly (just like conventional shaped charges). You'd get more energy on target than a simple device, maybe an order of magnitude more, but most of that energy will be coming as diffuse non-penetrating plasma instead of hard penetrating X-rays. Against a Whipple-shielded spacecraft the best a plasma spray is likely to do is melt/vaporise the outer layer, whereas the X-rays could potentially penetrate and damage critical systems (at the very least, screw up all the IR sensors).

or some sort of bomb pumped x-ray laser warhead?

That is a good idea in principle but it hasn't been shown to actually work in practice. Not in unclassified data anyway; the Cabra test was reported as a failure.

[Ariphaos]

A mass driver, lets say it fires a .1 C projectile at a target 300,000km's away. So ten seconds to cross the distance assuming a stationary target. So lets say it's a ship going at a very slow space speed, escape velocity at 11.2 kilometers a second.

A mass driver firing at .1 C is going to be a lot longer than 300,000 km in the first place.

[Simon_Jester]

Point defense? Why would you use a nuclear device as point defense? Knock down incoming missiles? A counter-missile can mission- or otherwise kill an incoming missile simply by smashing into it. In the vacuum of space, a nuclear device will produce a (very) bright flash of x-rays, a shower of alpha and beta particles, and a few kilograms of highly radioactive debris.

What you really want for point defense in space are flak projectors, or countermissiles with a chemical warhead that bursts the missile into a cloud of outbound fragments. At any speed where the incoming missiles are a major kinetic-kill threat against your ship, it takes only a very small object to kinetic-kill the missile. So put a lot of fragments in a wall across the missile's entire maneuver envelope; that way it can't simply dodge your countermissile and keep boring in.

This bright flash of x-rays and gamma rays will be about as hazardous to you as it will be to what you're defending against. Especially if the distances are short.

Countermissiles are useless if they don't hit the target more than a few hundred meters out from the hull in any case. At ranges long enough that it's worth even trying to shoot down the incoming missile, the flash from your own point defense nuke is not a serious problem.

Even then against an incoming kinetic projectile you're not going to do a whole heap of anything useful. Because the projectile is small, you have to be detonating really really close to do anything significant to it.

Though, to be fair, not as close as you'd have to get for a kinetic kill. Though probably closer than you would have to get for a kinetic kill if you used a normal missile with a chemical warhead on a time-delay fuze, as mentioned above.

Against guided projectiles, there's a real advantage to damaging it enough to knock out the guidance while it's still far enough out for you to evade. I'd much rather have a ballistic chunk of iron coming at me at 20 km/s from 600 km out than a maneuvering chunk of iron at the same range and bearing.

To people saying nukes wouldn't be worth it for unguided munitions, why is that? Even if the shell does as much/more damage by striking, doesn't the ability to miss by a few dozen or hundred meters and still make a kill make it very useful? Especially since dodging is the most viable form of defense against high velocity slugs?

Here, again, the smart plan is to use a chemical warhead as a bursting charge. Think WWII flak shells.

If you design the fragmentation right, that lets you make a much larger volume of space lethal for the missile than a nuclear blast would.

None of which are possible in a vacuum. In a vacuum, all you get is a pulse of hard radiation and a rapidly dispersing cloud of plasma and incandescent gas that used to be the device's casing and delivery vehicle (which won't amount to much.) The pulse of hard radiation loses strength according to the inverse-square law (i.e. the intensity of radiation diminishes as a function of the square of the distance from the event.)

Of course, in principle there's nothing stopping you from wrapping several tons of rocks around the bomb to get "shrapnel" (a denser cloud of plasma and/or fragments. But at that point you're talking about something too massive to be effective as a conventional missile. You'd more or less have to use it as a strategic weapon accelerated to speed by spaceship-sized boosters, or as a defense against incoming relativistic kill vehicles (steer the nuclear mine into its path, hit it with fragments, break it up and watch it disperse as it approaches the target).

A mass driver firing at .1 C is going to be a lot longer than 300,000 km in the first place.

The only questionable assumption I see is the field strength. For ferromagnets, 2 T or less is the lower bound, but superconductors can reach up to around 10 T already, though that requires cryogenics.

Room temperature superconductivity isn't guaranteed, but it's as plausible as a lot of other assumptions that go into depictions of hard-SF space combat, and while it doesn't give you 0.1c mass driver slugs, it does give you much higher muzzle velocities than 2 tesla will.

[Ariphaos]

The only questionable assumption I see is the field strength. For ferromagnets, 2 T or less is the lower bound, but superconductors can reach up to around 10 T already, though that requires cryogenics.

Room temperature superconductivity isn't guaranteed, but it's as plausible as a lot of other assumptions that go into depictions of hard-SF space combat, and while it doesn't give you 0.1c mass driver slugs, it does give you much higher muzzle velocities than 2 tesla will.

You would need to make the slug a superconducting electromagnet in that instance. Not happening.

The equations are only good for a uniform distribution of the field acting on a ferromagnetic projectile far from saturation. Even the 2 Tesla in this case is absurdly optimistic, above and beyond the overall force equations using a simplified, idealized case.

Note that, if you are not firing across a long enough distance where heat is an issue, then by all means - you can pump thirty or maybe even a couple hundred Tesla into it - but the projectile will demagnetize if not melt eventually. You can't afford that when you are talking about bringing it up to relativistic velocities - that is an entirely separate issue.

[Simon_Jester]

You would need to make the slug a superconducting electromagnet in that instance. Not happening.

The equations are only good for a uniform distribution of the field acting on a ferromagnetic projectile far from saturation. Even the 2 Tesla in this case is absurdly optimistic, above and beyond the overall force equations using a simplified, idealized case.

Ah, I see. I hadn't considered the effect of heating the projectile past the Curie temperature. Never mind, then.

[Sea Skimmer]

Most real concepts for coilguns or railguns of any great power use a separate armature which pushes the actual projectile. Even if the armature can't tolerate the heat, it might be possible to design it to combust or otherwise self destruct and bleed off energy as its fired, while still maintaining electrical contact. You just need a part of it, which might be a pretty small part of the whole, to keep on contact with the projectile to keep pushing it. You could even have a whole string of them burn up behind you, though this might make it a one use barrel. But what the hell space war is always expensive. It would might be no worse then a missile which is also one shot, long range space missiles would be epic in cost.

Given sufficiently advanced technology you could also reduce the total heat load by combining technologies with a light gas gun to boost up the initial speed, reduce workload on the armature. Those can reach 7km/s at the moment, which if you could make them work on a much larger scale would be a useful chunk of a tenth of the speed of light. An EM gun which does not need to start from zero velocity would be a much more viable design path if you wanted absurdly high velocities to come out of it.

[Iosef Cross]

The efficiency of artillery versus missiles in space depends on the conditions of the space "battlefields". Under certain conditions, artillery will be more efficient than missiles, under others, missiles will be more efficient.

If we have an combat environment where capital ships in different fleets are far apart and battles occur under thousands of kilometers in distance, missiles will be superior to artillery, for the reason that the enemy will be dispersed and very far away. In these conditions you need weapons with the precision and capability of trajectory correction of missiles. Also, if the starships have armor capable of resisting nuclear yield weapons, missiles are recommended because of their higher (on average) yield.

In the other hand, if we have an environment like the battle of Coruscant in RoTS, with starships close to one another, artillery will be the way to go. In this combat environment precision is not important: you will use area attacks and massed artillery.

Since the former conditions are the most probable for space warfare, missiles will be the weapon of choice.

[Ariphaos]

Saying something that achieves 7 km/second could scale up to a useful chunk of 30,000 kilometers per second is like saying walking will scale up to scramjet speeds.

[Sea Skimmer]

Saying something that achieves 7 km/second could scale up to a useful chunk of 30,000 kilometers per second is like saying walking will scale up to scramjet speeds.

We went from walking as the primary means of transport to scramjets in about 150 years, a blink of the eye considering mankind has been around hundreds of thousands of years already in a universe billions of years old, what was your point again? Last time I checked this was the science fiction forum.

[Starglider]

We went from walking as the primary means of transport to scramjets in about 150 years, a blink of the eye considering mankind has been around hundreds of thousands of years already in a universe billions of years old, what was your point again?

Gas-based guns are ultimately friction limited; either the projectile seal vs barrel walls, or the gas itself against the barrel walls. I don't know how to calculate the exact max velocity, but I doubt it's going to be of much use in a relativistic weapon (which would necessarily be a ridiculously long coilgun operating in a vacuum). As a first stage to a shp-mounted railgun operating at more realistic velocities, sure.

[Ford Prefect]

We went from walking as the primary means of transport to scramjets in about 150 years, a blink of the eye considering mankind has been around hundreds of thousands of years already in a universe billions of years old, what was your point again? Last time I checked this was the science fiction forum.

Did you miss the part where 'science fiction' has 'science' in it? Saying that a light gas gun might scale up from 7km/s by hundreds or even a thousand times would be akin to saying that in the future we might be able to build fusion drives which can pull a hundred gees. There's no real basis for making such a claim.

[Ariphaos]

We went from walking as the primary means of transport to scramjets in about 150 years, a blink of the eye considering mankind has been around hundreds of thousands of years already in a universe billions of years old, what was your point again? Last time I checked this was the science fiction forum.

Last I checked, walking and scramjets are such different modes of transportation that they have little else in common with each other. Light sails are a perfectly reasonable means to get an object to .1 of c or even better - but it is 1) Not a feasible weapon compared to the beam moving it and 2) Just as alien to your gas gun as scramjets are to walking.

As for the 'point', I made a factual claim, however elaborate, based on a known upper-limits equation. You proposed, as an alternative, a system that involved maintaining material contact while these velocities are approached. This being a forum filled with generally educated people, I made the assumption that I did not even have to bother with dismissing that as ludicrous.

Even if you want to bring the fiction into it, however, the fact remains that if you are using a gun in combat, a contraption of equal or lesser length can be used in defense, above and beyond any other benefit that such wondrous materials might present to combat.