Railguns

[MolotovCocktail]

How exactly does a railgun work, and what uses are there for it other than as a weapon?

 

I know it uses some sort of magnetic field to push projectiles out, but how exactly does it do it?

[Sisyphus]

Ok. Electrical current running in a straight line produces a circular magnet field perpendicular to it, kind of like a spiral. Two "rails" with current flowing in opposite directions will produce a powerful magnetic field in the same direction between them.

 

Also, an electrical current running perpendicular to a magnetic field produces a force perpendicular to both of them. So, you have your two electrified rails, and join them with a conductor, producing a parallel current to both the rails and the magnetic field those rails produce. That conductor experiences a force in the direction parallel to the rails.

 

Other uses I'm not really sure about, but I think I've heard talk of it being used as a cheap way of throwing satellites into space.

[Mokele]

Other uses I'm not really sure about, but I think I've heard talk of it being used as a cheap way of throwing satellites into space.

 

Using only a railgun is unfeasible, but railgun-assist, yes. If you used just a railgun, you'd have to accelerate the satellite to escape velocity in a comparatively short distance (at least compared to the usual distance), resulting in massive G forces, which in turn may damage delicate instrumentation (or require engineering compromises that reduce the abilities of instrumentation).

 

However, even accelerating a craft to 600 mph before it switches to on-board fuel would represent a tremendous savings in terms of fuel weight and cost of launch.

 

Mokele

[Sisyphus]

Yeah, g-forces would clearly be the major obstacle. It seems like you could reduce it by making a longer track? I wonder how long the railgun would have to be to reach escape velocity under reasonable acceleration. Maybe some kind of circular track?

[Mokele]

It seems like you could reduce it by making a longer track? I wonder how long the railgun would have to be to reach escape velocity under reasonable acceleration.

 

Using some basic kinematics, I found that with an acceleration of 5G, it would take 228 seconds to reach escape velocity, but would need a track 1279 kilometers long.

 

However, if you're just launching a tank of some substance like compressed oxygen or water or fuel, there's no real reason to restrict G forces. Still, even at 20G, the track would need to be 320 km long.

 

Maybe some kind of circular track?

 

Possible, but I cringe to think of how precisely engineered and perfect the switch mechanism would have to be.

 

 

In terms of straight feasability and economics, using it to just give rockets an initial boost would probably be best. The length would be defined by the point beyond which further railgun acceleration would be more costly and difficult than rocket engines.

 

Mokele

[Lekgolo555]

it is kind of like a monorail. It is using magnetism to pull the trains forward. The railgun uses magnetism to pull the projectile to a high velocity.

 

They made one already called metalstorm. It is pretty cool. It shots like a 1000 bullets a minute

[Sisyphus]

it is kind of like a monorail. It is using magnetism to pull the trains forward. The railgun uses magnetism to pull the projectile to a high velocity.

 

They made one already called metalstorm. It is pretty cool. It shots like a 1000 bullets a minute

 

A monorail is just any train with a single track. I assume you're thinking of a maglev train, but that works on different principles, and is quite different from a railgun. You might be thinking of a coilgun, which IS basically just "using magnets to pull the projectile to a high velocity," with simple attractive force to successive electromagnets.

 

That is NOT what a railgun is, however. Railguns use the force exerted on an electric current through a constant magnetic field.

 

Also, metalstorm is not a railgun. Also, it fires 1,000,000 rounds per minute.

[Rocket Man]

this is likely to be highly impractical, but is it possible to get a decent rail gun effect using ionised gas as the rails?

[Cap'n Refsmmat]

Possible, but I cringe to think of how precisely engineered and perfect the switch mechanism would have to be.

If we can do it with particle accelerators operating at .9c, we can do it with a railgun.

[Mokele]

If we can do it with particle accelerators operating at .9c, we can do it with a railgun.

 

Yeah, but this isn't directing a stream of particles, it's a rail supporting a several hundred ton ship, possibly filled with explosives. The forces on the rail themselves would be enormous. Any slight irregularity would have the same effect as the proverbial penny of the train tracks. The switching mechanism itself would have to move several multi-ton tracks from one position to another extremely fast and result in perfect alignment, and with no residual vibrations.

 

Mokele