Moderator: Alyrium Denryle
I was wondering if anyone could confirm/refute this and if so explain why. I know coil guns have a max velocity of 2 km/s because of physical limits for how fast the magnets can be energized and generate a field of sufficient strength. But I'm not sure about a rail gun.The maximum velocity of the projectile is about six kilometers per second, which is pretty freaking fast
so it depends on the pressure, and thus the temperature. So the real limit is only the material of the barel and the energy released by the reaction?Seggybop wrote:For a chemically launched projectile, the speed is limited by the velocity at which the propelling gas expands (from here referencing space-launch cannons)
Damn...me want!Seggybop wrote:For a chemically launched projectile, the speed is limited by the velocity at which the propelling gas expands (from here referencing space-launch cannons)
Whoa ! Reallife railguns are way faster than I thought. Any idea how big the projectile was ?n atmosphere, which is really the only place we're going to be using such things, the speed limit is determined by drag and so friction on the projectile. Escape velocity is around 11 km/s, which has been attained by the railgun in Texas at Austin University, but you run into the problem of a slug exploding before it gets anywhere near the target. There is no real speed limit, bar the ultimate one that is. But with air in the way of the target it means under 10 km/s will be the norm, likely around 4 km/s as proposed in most military journals for naval railguns.
I've incessantly seen 8km/s quoted as the maximum velocity that could be achieved with a railgun (but I think that's for in an atmosphere), with 6km/s being the most likely practical limit, due to the horrendous barrel erosion such a weapon would have and the limits of the atmosphere on the projectile.Ender wrote: I was wondering if anyone could confirm/refute this and if so explain why. I know coil guns have a max velocity of 2 km/s because of physical limits for how fast the magnets can be energized and generate a field of sufficient strength. But I'm not sure about a rail gun.
Most certainly; chemical propellants can't produce velocities over about 2km/s, modern tank guns with muzzle velocities of 1.8km/s represent the highest velocity weapons around and are basically the limit of the technology. However, a high end Electric Thermal Cannon could potentially go higher then this, to 2.5km/s or more, by converting chemical propellant into plasma with a huge electrical pulse.Also, is there any such liit on the velocity of an explosive launched projectile?
If you read what Ender posted, you'd know that it is to do with the potential for the electromagnets to charge up and degauss quickly enough. There is only so fast a way you can do that and so coilguns typically stop around a couple of klicks a second. Railguns have no such limit as the electrical potential of the rails moves the slug (or armature). I should add, rail erosion is no longer a massive problem thanks to plenty of research into tough, low-friction coverings. The early railguns had bare copper rails usually and wasted most of the energy as sound and heat from plasma as the surface of the rails came off during firing.The Shadow wrote:What is this coil gun limitation Ender mentioned ? Why are not railguns affected by it too ?
Wait, is this coilgun limitation physically fundamental? Couldn't you hypothetically overcome any timing difficulties just by making a really really long one (e.g. in space) with ultimately huge distances to the next coil?Admiral Valdemar wrote:If you read what Ender posted, you'd know that it is to do with the potential for the electromagnets to charge up and degauss quickly enough. There is only so fast a way you can do that and so coilguns typically stop around a couple of klicks a second. Railguns have no such limit as the electrical potential of the rails moves the slug (or armature).The Shadow wrote:What is this coil gun limitation Ender mentioned ? Why are not railguns affected by it too ?
Apparently, Sandia National Research Laboratories made 0.1g go 16km/s, and Maxwell Laboratories did 1.6kg at 3.3km/s. Although that page appears a bit old.The Shadow wrote:Whoa ! Reallife railguns are way faster than I thought. Any idea how big the projectile was ?n atmosphere, which is really the only place we're going to be using such things, the speed limit is determined by drag and so friction on the projectile. Escape velocity is around 11 km/s, which has been attained by the railgun in Texas at Austin University, but you run into the problem of a slug exploding before it gets anywhere near the target. There is no real speed limit, bar the ultimate one that is. But with air in the way of the target it means under 10 km/s will be the norm, likely around 4 km/s as proposed in most military journals for naval railguns.
It is inherent to the physics of the electromagnets, no advance in technology will produce fields that form and collapse instantly. Railguns are cheaper, simpler and have an infinite theoretical speed limit within certain constraints.Winston Blake wrote: Wait, is this coilgun limitation physically fundamental? Couldn't you hypothetically overcome any timing difficulties just by making a really really long one (e.g. in space) with ultimately huge distances to the next coil?
Quenching superconductors. Those quench at some ludicrious rate when you have fast heating (i.e. laser or electrom beam irradiating the the wire). The problem is you need a high Tc superconductor which is just barely up to liquid nitrogen temperatures for anything that can be made pliable. In the future you might be able to set up a superconducting ring current that results from electron pumping, which gets you quench rates on the order of atomic motion scales. Instaneously, no, but with some hefty technological progress you could theoreticly get it down to a dozen femtoseconds.It is inherent to the physics of the electromagnets, no advance in technology will produce fields that form and collapse instantly. Railguns are cheaper, simpler and have an infinite theoretical speed limit within certain constraints.
Eh the paper I read dealt with launching payloads into orbit. We have yet to reach the theoretical limit of coilguns, only hit massive cost effectiveness and technological barriers.Indeed, you could get some high-rates, but I'm taking field deployability into account here since we're talking military (the most interesting field for such tech I admit). Coilguns are great for lack of friction with the barrel, but the added weight of those electromagnets, especially if they have to be liquid cooled and superconducting, means more cost as well and bigger target.
