Navy Debuts New Railgun That Launches Shells at Mach 7 630
Jeremiah Cornelius writes: "The U.S. Navy's new railgun technology, developed by General Atomics, uses the Lorentz force in a type of linear, electric motor to hurl a 23-pound projectile at speeds exceeding Mach 7 — in excess of 5,000 mph. The weapon has a range of 100 miles and doesn't require explosive warheads. 'The electromagnetic railgun represents an incredible new offensive capability for the U.S. Navy,' says Rear Adm. Bryant Fuller, the Navy's chief engineer. 'This capability will allow us to effectively counter a wide range of threats at a relatively low cost, while keeping our ships and sailors safer by removing the need to carry as many high-explosive weapons.' Sea trials begin aboard an experimental Navy catamaran, the USNS Millinocket, in 2016."
Re:IANA Physicist, So... (Score:5, Informative)
Hot expanding gases, you're pushing a projectile at Mach 7 through air that doesn't really have anywhere to go.
Re:IANA Physicist, So... (Score:5, Informative)
It is called plasma. It happens when you heat gases beyond a particular limit.
A 23 pound slug traveling at Mach 7 is displacing a lot of air very quickly.
Do you think that air will get colder?
SWATH, not Catamaran (Score:5, Informative)
Re:IANA Physicist, So... (Score:5, Informative)
Oxygen, it's in the air...
fine vaporized particles of metal...
*poof*
Re:"Low Cost" (Score:5, Informative)
Railgun $25,000 a round versus $1,000,000 a round for missiles.
Cost on just purely physics level, is rather irrelevant. It is economics that are the limiting factor.
Both GA and BAE Railguns will be Tested (Score:3, Informative)
Not to nitpick (well.....yah, I'm nitpicking), but both General Atomics and BAE Systems Railguns will be tested on the USNS Millinocket. BAE Systems actually got the Phase II contract, whereas General Atomics did not.
Link: http://breakingdefense.com/2014/04/navys-magnetic-super-gun-to-make-mach-7-shots-at-sea-in-2016-adm-greenert/
Full Disclosure: I nearly got to work on the GA RailGun system and I know some people who are on it. It's a better design than the BAE one but BAE got the contract.
Re:IANA Physicist, So... (Score:5, Informative)
"Flame" is nothing but superheated gases. You can have a flame without combustion if you raise the temperature some other way. In this case it's electrical heating, ram air pressure, and simple air friction.
And the advantage of this is? (Score:5, Informative)
Many!
Imagine if you didn't need to handle explosives like Cordite as propellents anymore. This will reduce storage space and make a battleship's gun turret a while lot safer place to work. One small spark won't set off a magazine anymore.
"Muzzle velocity" is higher, so the distance you can throw something is a bit further, like 5x further. If you can fire further, you have a huge advantage because you can hit your opponent before he can shoot at you. Or if you are doing ground support, you can fire further inland.
I'm assuming a rail gun will be faster to reload. Might take some time to recharge the power supply, but surely we can fire faster than a Mark 7's 2 rounds a minute. More pounds and rounds on the target than your opponent is always better.
Finally, it may be possible to more strictly control forces on the shell when firing it, which may make it possible to put more technology IN the shells, and still get very high velocity. Imagine a shell that can adjust it's flight path, even slightly, which means you can fire in the general direction you want, then fine tune the aim in flight. (I assume they don't do that now..)
Issues to watch out for: First, Rail guns tend to have tracks (rails) and said rails usually have difficulty with wear due to the huge forces and high speeds involved. Hopefully they have engineered the better materials. Second, power supplies for rail guns have to be designed to provide HUGE impulse powers with power generation systems wanting to be running at steady state. You have to match the two. Finally, weapons like this usually mean you have to redesign the whole weapons system, a process that literally takes decades.
Go Navy, this is worth the R&D money..
Re:IANA Physicist, So... (Score:4, Informative)
The temperature of the air will be around ten times ambient, so 3000K, which is more or less the stochiometric temperature for hydrocarbon fuels.
Read this [cfd-online.com] for details of the isentropic flow relationships.
Re:IANA Physicist, So... (Score:2, Informative)
most high power rail guns operate with what is called a plasma armature, meaning that the projectile or sabot is probably designed with ablation in mind and that the current heats the metal body of the sabot or projectile to the point of ionization so that additional accelerating current is able to flow through the plasma
the 'plasma cloud' behind the projectile is at a temperature of thousands of degrees -- it will appear 'hot' from blackbody radiation and emission spectra of anything moving in the cloud, and the fact that it's both enormously hot and ionized and has things with colorful emission spectra floating in it is for the most part enough for it to behave like a fireball when leaving the confinement of the barrel, but probably there are combustion and electrochemical reactions occuring as well
Re:Power? (Score:5, Informative)
Mach 7 = 5300 mph = 2382 m/s
KE = 0.5mv^2 = 59.6 MJ
The ship in question has four 9100 kW diesel engines (12,200 hp).
Assuming you have a big enough capacitor, the output from just one diesel engine should be enough to power a round every 6.5 seconds. There are conversion and efficiency losses, so probably every 15-20 seconds is more realistic.
Also note that 59.6 MJ is about equivalent to 14 kilos of TNT. So the energy yield of this will be on the order of a high explosive round from a 5 inch shell (which weighs about 30 kg), assuming the projectile doesn't pass entirely through the target.
Re:IANA Physicist, So... (Score:5, Informative)
Not exactly. Oxygen is a prerequisite for the process known as combustion, since combustion is an oxidization reaction. "A rapid, exothermic oxidation of a substance, called the fuel," is a reasonable definition of combustion. Usually we say the fuel is combustible.
Re:Shoot The Moon! (Score:4, Informative)
It's got a ways to go.
Re:WTF? (Score:4, Informative)
Why the hell does an inert slug encased in a discarding sabot cost twenty grand?
The only way these get cheap is if we have to make a lot of them to fight a war. Be thankful we only have to deal with low-rate peacetime economics where the development costs of unique tooling gets amortized across a small number of prototype rail gun slugs creating a big per-unit price tag that causes fools to go apoplectic.
Re:IANA Physicist, So... (Score:5, Informative)
There are several advantages to railguns for the Navy, in lethality, cost-per-round, how much ammo you can carry, and overall safety.
Lethality - the kinetic energy of a 'passive' round at these velocities is equivalent to or greater than an explosive round (though I would think it might not be all that useful in all circumstances - just flying through some softer materials instead of blowing them up). As the videos show, the 'kill' factor is substantial. The projectiles are also much less affected by gravitational drop and windage - I would think proportional to the velocity - so accuracy will be better. The higher velocity also allows for firing at much longer range - up to 200 miles vs. 30 for the latest 155mm round.
Cost-per-round - while not as cheap as lasers (the laser about to go through sea trials has a cost of about $1 per shot), these systems should have a cost-per-round an order of magnitude cheaper than the big artillery presently in use. (I just read that 155mm shells cost $50,000 each.) It's much easier, cheaper, and safer to build a solid chunk of tungsten or whatever than a huge shell, especially when the savings in transport and necessary safety systems and procedures is taken into account.
How much - the propellant takes up a lot of space, must be stored in special containment that takes up more space. All of that space can be used to store actual projectiles instead, possibly multiplying the number of rounds available by a factor of 5 to 10. Add to that the the higher kinetic energy allows a smaller projectile to be equally effective, which means you can increase the number even more.
Safety - this eliminates the problem of ammunition exploding either in the ship that will use it, or the supply ship. There are many instances of a single 'lucky' hit on a ship that happens to penetrate the ammunition magazines, whereupon that explosion rips the ship in half. The explosives used in ammunition are also toxic. Removing the propellant greatly increases the survival probability in the event of a hit, and eliminates the probability of an unfortunate accident sinking the ship. This also means the supply ships are safer and can deliver much more ammunition in one trip.
Re:IANA Physicist, So... (Score:5, Informative)
1. The projectiles are inert blocks of metal by necessity of their design, and yet they strike with enough force to cause incredible destruction on impact. (kinetic energy released as mechanical failure of structure, turning into an explosion) which leads to,
2. Inert projectiles are safer to transport for the military. (no one has to sleep on a ship full of explosives)
3. They projectiles are far cheeper to manufacture. (its a block of metal and a sabot, vs the complex things that go into a detonatable round that can be fired a long distance)
4. The range. 100 mile range on these things means they can engage targets without risking the ship itself as much, which is always a plus in combat.
5. One guy can operate it. If you ever watch any footage of large naval guns being fired, it tends to be a multi-person operation to load, fire, and work the gun. Less manpower devoted to a single operation is always helpful.
Re:IANA Physicist, So... (Score:5, Informative)
The flight time at mach 7 for 200 miles is about 2.3 minutes, practice your highschool physics and work out how much it drops not allowing for drag.
(hint: a LOT). That is assuming no loss of speed (which of course would be SIGNIFICANT).
Which kind of helps, otherwise it could not reach the ground for much of a distance, but hell.. it still needs to be allowed for.
But even worse, the effect of a crosswind along the trajectory path sums over that time also, and that matters as it is much less predictable.
This is a kinetic kill vehicle - it needs to hit the target, without terminal guidance. At 200 miles, it simply will not (unless the target it BIG, as in a small
town..). They will of course try and convince us this is a surgical weapon, however it is not - unless they start using terminal guidance, and good luck getting
electronics to survive the electromagnetic environment of launch in this thing.
This will of course allow them to more cheaply scattergun an enemy from a nice safe range - go USA!