SoylentNews is people
SoylentNews
Allen McDuffee writes the US Navy's latest weapon is an electromagnetic railgun launcher that can hurl a 23-pound projectile at speeds exceeding Mach 7 with a range of 100 miles turning a destroyer into super-long-range machine gun able to fire up to a dozen relatively inexpensive projectiles every minute. The Navy says the cost differential $25,000 for a railgun projectile versus $500,000 to $1.5 million for a missile will make potential enemies think twice about the economic viability of engaging U.S. forces. "[It] will give our adversaries a huge moment of pause to go: 'Do I even want to go engage a naval ship?'" says Rear Admiral Matt Klunder. "Because you are going to lose. You could throw anything at us, frankly, and the fact that we now can shoot a number of these rounds at a very affordable cost, it's my opinion that they don't win."
Engineers already have tested this futuristic weapon on land, and the Navy plans to begin sea trials aboard a Joint High Speed Vessel Millinocket in 2016. Railguns use electromagnetic energy known as the Lorenz Force to launch a projectile between two conductive rails. The high-power electric pulse generates a magnetic field to fire the projectile with very little recoil, officials say. Weapons like the electromagnetic rail gun could help U.S. forces retain their edge and give them an asymmetric advantage over rivals, making it too expensive to use missiles to attack U.S. warships because of the cheap way to defeat them. "Your magazine never runs out, you just keep shooting, and that's compelling."
(Score: 2) by egcagrac0 on Friday April 11 2014, @12:29PM
The Hypervelocity Projectile [navy.mil] that the railgun launches is far more interesting than the article suggests.
At first, I was wondering how they could make a 23 pound hunk of metal cost $25,000. Now, I'm wondering what the "guidance electronics" are that the HVP page is talking about, and what they can do.
Big electric guns are cool, but the Mach-7 and shooting-around-corners* parts are pretty spiffy.
*I have no idea if it shoots around corners - they haven't told us much about what the bullet can do.
(Score: 2) by Rivenaleem on Friday April 11 2014, @01:04PM
That any guidance electronics survive the coils is the spiffy part I think.
(Score: 2) by wantkitteh on Friday April 11 2014, @01:11PM
Far more interesting to me is that they aren't mentioning barrel lifetime any more. A few years ago they couldn't get more than a few rounds through it before the stress destroyed it. Perhaps the counter-tactic for these ships will be to fly lots of cheapass drones towards them, forcing them to engage them all, wearing out the railgun and putting it out of action?
(Score: 2) by Rivenaleem on Friday April 11 2014, @01:27PM
Except I don't think the Railgun is for shooting drones. I expect they'll still have conventional guns for that. This weapons is more for shooting Constructacons from the tops of pyramids.
(Score: 0) by Anonymous Coward on Friday April 11 2014, @05:48PM
Those guidance electronics are probably wrapped inside a reasonably effective Faraday cage - the hunk of metal that is most of the projectile. A layer (or 6) of mu-metal [wikipedia.org] might help, too.
(Score: 2) by frojack on Friday April 11 2014, @07:15PM
There is no such thing as a "reasonably effective Faraday cage" at the voltages being used in rail guns.
No, you are mistaken. I've always had this sig.
(Score: 0) by Anonymous Coward on Monday April 14 2014, @01:00PM
(Score: 2) by frojack on Monday April 14 2014, @11:51PM
Yes it does.
Don't believe me? Put on your rubber boots, and hold up a metal rod while standing on a hill in a thunder storm.
You will quickly find that there is no such thing as insulation where lightning is concerned.
No, you are mistaken. I've always had this sig.
(Score: 3, Insightful) by TK on Friday April 11 2014, @03:10PM
Thanks for the link.
A few numbers for the interested.
To accelerate a 23lb (10.5kg) mass to Mach 7 (2400 m/s, 5300 mph) requires ~3*10^7 J of energy. To do this twelve times every minute requires 6*10^6 W of power. The USNS Millinocket is powered by four 8000 kW diesel generators. If there is no additional power supply, this gun will require almost 20% of the total available power, not including electrical losses.
The peak temperature on the nose of the projectile at Mach 7 is ~3000 C. Note the different colored material on the concept in the pdf, that's probably an ablative coating to dissipate heat.
Given that the nose is so hot, I don't know what kind of sensing equipment these could reasonably use, certainly not something based on heat signature of the enemy. On the other hand, mach 7 is just the muzzle velocity, and the speed would drop off rapidly in flight. I would attempt a rough calculation of the drag over the 100 mile range, but wave drag is dominant at these speeds, and I don't have those equations available at the moment. I could reasonably see this traveling at supersonic speeds even after 100 miles, but the nose temperature is a function of the square of mach number, and would present a much smaller problem at say, mach 2 (1.8 times ambient temperature, rather than 10.8).
It definitely has control surfaces to correct for targets moving in unexpected ways. In this case, you don't really need to correct too much, because boats are slow, and your projectile is fast. I wouldn't exactly call it shooting around corners, but you can get a bit of curve if you need to.
A quick look at wikipedia for the 5" guns mentioned in the pdf, gives the Mark 42 [wikipedia.org] and the Mark 45 [wikipedia.org], at 6.858m and 7.874m barrel length, respectively. Given a muzzle velocity of 2400 m/s, the average acceleration would be about 37,000 g in the longer gun, and 43,000 g in the shorter one.
If anyone would care to take a stab at the current requirements for the gun, the Wikipedia article on railguns [wikipedia.org] has a set of equations, but the resistance in the coil is a function of the projectile's position, and I don't feel like doing that much calculus on a Friday.
The fleas have smaller fleas, upon their backs to bite them, and those fleas have lesser fleas, and so ad infinitum
(Score: 0) by Anonymous Coward on Friday April 11 2014, @04:00PM
Well if you include shooting over the horizion as shooting around a corner... then yes it can.