Comments on: Rail gun uses kinetic energy to deliver Mach 5 wallop

Navy tests electro-magnetic rail gun.

[qwerty75]

Why don't they develop a rail gun for something useful for a change?

Like launching people into space! :)~

Gotta feel the acceleration!

Seriously, this is stupid. This has an extremely high of an energy requirement to make this practical. Have they forgotten about rockets?

This is government waste at is worst.

[GGGlen]

Rubbish.

Ever serve on a naval vessel?
Well I have.
Eliminating the need for highly complex, highly dangerous, highly expensive (and highly combustible!) systems for the development, maintenance and deployment of chemical rocket motors is a GOOD thing.
Last thing- About the energy requirements?
Naval combat vessels aren't Hyundai Sonata's.
They're very big, and they can carry turbine generators up the wazzoo.

[The_Decider]

Rubbish?

Can a ship currently produce enough power for all its systems, plus this?

No!

What that means is more nuclear reactors are needed. A terrible idea for little to no gain.

The ship will still have to carry weapons loaded with HE.

It is a bad and wasteful idea.

[Mark Donovan]

See http://www.onr.navy.mil/emrg/electromagnetic-railgun.asp for some facts and figures.

In 2004, a Navy technology assessment estimated the power for a rail gun could be supplied by a 15 to 30 MW dedicated pulsed alternator power generator. Other solutions use capacitors and excess power from existing on-board gas turbine generators.

As a comparison, a conventional high-explosive round uses 90 lbs of explosive propellant with a high-explosive warhead that weighs 260 lbs. The energy needed for a non-explosive 44-lb rail gun round is generated by 3 gallons of fuel.

[ralfthedog]

The big question is firing rate. How long does it take to charge the capacitors?

[GGGlen]

None at all.
The Navy is currently installing MKII Mr Fusions aboard all its vessels.
;-)

[Mark Donovan]

The Navy estimates the fully-developed rail gun will fire 6 to 10 rounds a minute. See http://www.onr.navy.mil/emrg/electromagnetic-railgun.asp and http://www.onr.navy.mil/emrg/faqs-electromagnetic-railgun.asp for answers to other questions, and the advantages rail guns have versus rockets and conventional explosive rounds.

[phsics1]

A joule is what's needed to produce one watt of energy for one second. NO!

A Joule is a unit of energy, A Watt is a unit of power. 1 Watt of power delivers 1 Joule of energy each second.

[JayScott]

Huh? It goes both ways! Sheesh! Even TIME goes both ways, for cryin' out loud! (Ever hear of a Feynman diagram?) If a watt for a second delivers a joule, then the reverse is just as true, even if it's not the usual way of thinking about it. Please! We get so much actually scientifically illiterate reporting that you really don't have to go and invent an offense.

[3rdalbum]

How would a railgun cover ground-based operations? Does it fire basically in a straight line or can it work in an upwards arc? If the former, then it's useless for providing covering fire from a ship to ground. If you could fire it in an upwards arc, and there's no warhead on board, then you'd end off damaging everything except the target.

[GGGlen]

Say what?
1st of all, I've read (and reread) the article and don't see a mention of supporting "ground based operations" anywhere in it.

A system like this would, however, provide excellent protection against what current naval missile systems are currently designed to do- Namely, knocking incoming aircraft out of the skies.

2nd of all, in the system WERE to be deployed as "ground cover", how in the blue blazes would the EXCLUSION of HIGH EXPLOSIVES, contribute to "damaging everything except the target"?

Logically, it should be evident to even the most casual of reader, that by ELIMINATING THE EXPLOSIVE WARHEAD, you can't damage everything EXCEPT the target.

Need I continue?

[The_Decider]

Are you joking Glen?

A projective with no self-propelled ability is going to shoot down aircraft at 100+ miles?

If you understood what a rail gun is, you would know it is a terrible idea.

[The_Decider]

Also, the recharge time will be fairly high, making it unreasonable to to fire twice at a moving target.

It is get a million to one shot off, or die.

Nice weapon.

[Mark Donovan]

The rail gun proposed by the Navy will fire 6 to 10 rounds per minute (one round every 6 to 10 seconds) at mach 7 (6 seconds to the horizon). WW II battleship main batteries fired about 2 rounds per minute.

[gjkezski]

The trajectory of the projectile is completely controllable by varying the electrical power allotted for driving it down range using something similar to a volume control. Turn it completely up & you will get the rated Mach 5, turn it down & it should be able to drop it within less than a mile. For an explosive projectile they might be able to design something similar to an older idea called a ring-airfoil grenade, this would be able to be slipped around the outside of the barrel. The magnetic field is not only inside the barrel, it also runs along the outside of the barrel as well. It could possibly be built with a hinge running down one side with a catch along the other side. Bring it up on a lift ahead of the breech assembly inside the turret, swing the two halves together & lock them shut then fire/energize the coil.

[gjkezski]

Who says that the projectile will have no directability? As the initial acceleration will be FAR less than developed by a gunpowder charge there is no reason for it to not have Some controllability. Even then, check out the US Army's "Copperhead" artillery round. It would not take that much to add that type of targeting capability to whatever they use.

[chuckhoffmann]

While this is an interesting development in railgun technology, the question I have to ask is, "Why is this weapon system needed?" Is there some shortcoming in the existing mix of naval gunnery and missile technology that it addresses?

[GGGlen]

You cannot electronically jam a Mach 5 slug of metal, and the range of the rail gun is, as stated in the article, 10x that of existing naval guns.

Also, and unlike the ECM susceptible missile, a soup can sized projectile won't show up on radar.

[AdventPurgatory]

Would you rather fire a million dollar cruise missile that is going to cause a lot of blast damage or an aluminum bullet thats a very small fraction of that cost and does pinpoint damage such as taking out a tank or single building not a whole city block.

[Lyzdog]

Edina Apartments Steals Money

[dmm]

Railguns would NOT be used to shoot down planes. From the Pop Sci article:
"The Marines, in particular, are interested in the potential for rail guns to deliver supporting fire from up to 220 miles away -- around 10 times further than standard ship-mounted cannons -- with rounds landing more quickly and with less advance warning than a volley of Tomahawk cruise missiles."
My understanding is that they shoot the projectiles in an arc. For reference purposes, Tomahawk cruise missiles travel at about Mach 0.9. Russia and India have jointly developed a cruise missile that can go Mach 2.8 and has a 200-mile range. India is talking about a Mach 8 cruise missile. See http://en.wikipedia.org/wiki/Brahmos
But the rail guns might have big advantages in fire rate, number of rounds, and cost per shot.

[Josh.Lowensohn]

Best video. Ever.

[skiwithpete]

If the gun is being fired by magnetic rails why is there fire that comes out of the muzzle when the projectile leaves the barrel?

[AdventPurgatory]

The projectile is leaving the barrel at such a high velocity that little shreds of aluminum are peeling off and basically burning up in the atmosphere.

[wildchild_plasma_gyro]

You ain got some spares that i can reengineer into my car have you.

[gjkezski]

Frankly, I'm amazed that it has taken them this long to be getting around to doing it. Back in the '70s there was a semi-trailer sized test bed rail gun that accelerated a 100 gram projectile to a velocity of 10km a second. Earths escape velocity is "only" 11km per second. Maybe there is a problem with scaling it up?

Maybe they should have tried a smaller trial concept. Maybe something around the scale & purpose of a replacement for the Phalanx ADA system. The power requirements would have been less than a full sized gun/launcher for the same rate of fire as the modified Vulcan & much easier to test to prove the concept.