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The Military United States

Navy Debuts New Railgun That Launches Shells at Mach 7 630



Navy Debuts New Railgun That Launches Shells at Mach 7

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    Do you think that air will get colder?

  • SWATH, not Catamaran (Score:5, Informative)


    Oxygen, it's in the air...

    fine vaporized particles of metal...


  • Re:"Low Cost" (Score:5, Informative)

    by PortHaven (242123) on Wednesday April 09, 2014 @02:20PM (#46706683) Homepage

    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.

















    Read this [] for details of the isentropic flow relationships.

  • by Anonymous Coward on Wednesday April 09, 2014 @02:54PM (#46707075)

    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)

    23 lbs = 10.5 kg
    Mach 7 = 5300 mph = 2382 m/s
    KE = 0.5mv^2 = 59.6 MJ



  • by Bacon Bits (926911) on Wednesday April 09, 2014 @03:01PM (#46707149)

    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)

    by kenaaker (774785) on Wednesday April 09, 2014 @03:09PM (#46707229)
    Escape velocity is Mach 33, 11.2 kilometers/second, orbital velocity is Mach 25, 7.7 kilometers/second.

    It's got a ways to go.

  • Re:WTF? (Score:4, Informative)

    by Tailhook (98486) on Wednesday April 09, 2014 @03:29PM (#46707437)

    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.

  • by garyebickford (222422) <> on Wednesday April 09, 2014 @03:33PM (#46707473)

    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.

  • by Jarik C-Bol (894741) on Wednesday April 09, 2014 @06:09PM (#46708893)
    The article explains what the major advantages are. Short version, is:

    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.
  • by thesupraman (179040) on Wednesday April 09, 2014 @06:12PM (#46708905)

    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!
