NASASpaceFlight.com Forum

General Discussion => Advanced Concepts => Topic started by: on 01/17/2007 11:18 PM

Title: Navy rail gun breaches atmosphere
Post by: on 01/17/2007 11:18 PM
http://fredericksburg.com/News/FLS/2007/012007/01172007/251373/index_html?page=1












Title: Re: Navy rail gun breaches atmosphere
Post by: Stowbridge on 01/17/2007 11:32 PM
Now THAT'S what I'm talking about! Thanks very much for the link Bhankii. Awesome technology.
Title: Re: Navy rail gun breaches atmosphere
Post by: Norm Hartnett on 01/17/2007 11:56 PM
"When this thing leaves, it's [under] hundreds of thousands of g 's"

Very cool weapon system that I've been reading about for decades in SciFi. I wonder about the applications for shipboard anti-air, anti-missile?

Smaller projectiles fired at a high rate with that kind of speed could be more effective than the Vulcan system.
Title: Re: Navy rail gun breaches atmosphere
Post by: meiza on 01/18/2007 12:10 AM
I wonder how good can their accuracy be, if the resulting projectile is almost as expensive as a missile...
If the launch energy used is 64 MJ and they use a 1 MW generator, the load up time is only about a minute. With 10 MW, a few secs. (Seems Aegis cruisers have 75 MW shaft horsepower so they can spare.)
Title: Re: Navy rail gun breaches atmosphere
Post by: PurduesUSAFguy on 01/18/2007 01:16 AM
Once this technology has matured it will make cruise missiles obsolete. The next generation of US suface combatants, the DD(X) and CG(X) are going to be 'all electric' ship, that is to say their gas turbines and reactors generate electricity that is used to drive electric motors to drive the ship as opposed to generating steam to turn steam turbines for propulsion. This will allow ships power to spare for energy intensive weapons like rail guns.

From what I've read the rail guns envisioned by the navy for the potentially nuclear powered CG(X) they will be able to hit targets up to 600 miles inland with with minutes of travel time and since the projectile is simply a dart made of ferrous metal, the 'per shot' cost should be under $2000.

This will change the way the navy goes about power projection and once again put the gun carrying surface ship as the most important ships in the fleet.
Title: Re: Navy rail gun breaches atmosphere
Post by: nacnud on 01/18/2007 02:08 AM
Well there is still the small problem of stopping the rail gun melting with each shot, even at the current 8 MJ.
Title: Re: Navy rail gun breaches atmosphere
Post by: stargazer777 on 01/18/2007 02:47 AM
I saw a show on the Discovery Channel (Future Weapons) about a new GPS steerable artillery round (Excalibur) with tremendous range and accuracy developed for the Army.  The reason I mention it is that they had to develop electronics and navigation foils that could withstand the enormous G forces encountered in being fired out of a high velosity cannon and still instantly deploy to permit it to guide the round to the target.  Not sure the G-forces encountered by this artillery round are comparable to those that would be encountered by a rail gun projectile.  It seemed to be nearly ready for deployment with the Army.
Title: Re: Navy rail gun breaches atmosphere
Post by: TyMoore on 01/18/2007 04:30 AM

When I was in highschool (1985) I designed a fairly crude rail gun for a science fair project--but once the Principal got wind of what I had in mind, they squashed it as way too dangerous. Mine was just a teensy one: two meters long; stainless steel rails set for a 0.5 inch slug of solid copper; silver soldered copper pipe for bus bars; and fifteen salvaged car batteries (in parallel) for intermittent 5,000 to 10,000 amp pulses. I figured it might have a muzzle velocity of about 1 km/s. I guess it scared the bejeezes out of them.

I always wanted to build it though...

Later when I was in college studying undergraduate physics (1991), I had an interesting idea to build a three phase, 220vac electromagnetic coil gun that shot BB's. Again, something less than two meters long, firing BB's at a steady rate of 30-50 per second with a muzzle velocity close to 1 km/s. Using water cooled copper pipe for the windings and arcwelder triacs for switches triggered by photodiode / phototransistor arrays along the barrel to energize the coils sequentially, I figured the thing would dissipate just about 7kw when firing full auto.

Again never built the thing, but I always wanted too.

Naval rail guns will offer tremendous firepower in an economical package. Look for them in twenty years mounted on all electric tanks for the Army and Marine Corps. Small EM machine guns shooting almost solid streams of BB's would be an almost perfect close in weapons system--perfect for a replacement for aging Phalanx CIWS antimissile systems currently in use on US warships.
 

 

Title: Re: Navy rail gun breaches atmosphere
Post by: SimonShuttle on 01/18/2007 07:36 AM
Rail Gun, will then have a BFG next? ;)
Title: Re: Navy rail gun breaches atmosphere
Post by: stargazer777 on 01/18/2007 08:16 AM
Naval rail guns will offer tremendous firepower in an economical package. Look for them in twenty years mounted on all electric tanks for the Army and Marine Corps. Small EM machine guns shooting almost solid streams of BB's would be an almost perfect close in weapons system--perfect for a replacement for aging Phalanx CIWS antimissile systems currently in use on US warships.
Yes, but meanwhile other advanced weapons technologies are also advancing.  Directed energy and laser weapons for sea based, land based, airborne and space based applications are also rapidly being developed.  It will certainly make things interesting.
Title: Re: Navy rail gun breaches atmosphere
Post by: meiza on 01/18/2007 11:40 AM
What I'm saying is, the projectile can't be cheap and accurate at the same time! If it has to maneuver with airfoils, it is going to be expensive. And a solid slug is just very inaccurate at those distances.

And for the other things, ball ammo sucks for accuracy.
Title: Re: Navy rail gun breaches atmosphere
Post by: kevin-rf on 01/18/2007 12:41 PM
Nor are you going to launch complex payloads, like cluster munitions with them. There will stll be a need for cruise missiles.
Title: Re: Navy rail gun breaches atmosphere
Post by: on 01/18/2007 01:24 PM
Quote
meiza - 18/1/2007  6:40 AM

What I'm saying is, the projectile can't be cheap and accurate at the same time! If it has to maneuver with airfoils, it is going to be expensive. And a solid slug is just very inaccurate at those distances.

And for the other things, ball ammo sucks for accuracy.

You could put some fins on the back to get some spin - that would improve the accuracy.  At $1000 a pop you can fire 1000 for the cost of a cruise missile.  Surely you'll hit something.
Title: Re: Navy rail gun breaches atmosphere
Post by: simonbp on 01/18/2007 01:30 PM
This actually could work as an anti-satellite weapon, especially with the seeker head already developed for missile defense; timely considering that the Chinese just tested their first kinetic asat...

Simon ;)
Title: Re: Navy rail gun breaches atmosphere
Post by: kevin-rf on 01/18/2007 01:35 PM
Quote
bhankiii - 18/1/2007  8:24 AM
You could put some fins on the back to get some spin - that would improve the accuracy.  At $1000 a pop you can fire 1000 for the cost of a cruise missile.  Surely you'll hit something.

A fin will behave how at those speeds? You could groove the projectile body to cause it to spin. The sad part mentioned in the article is the acceleration is to high for current electronics. So no terminal guidance...

There was some interesting news on ultra capacitors from eestore over at hobby space this morning. http://hobbyspace.com/nucleus/HSblog.php?itemid=3186

It would help with the energy storage for these devices.
Title: Re: Navy rail gun breaches atmosphere
Post by: edkyle99 on 01/18/2007 02:27 PM
Quote
PurduesUSAFguy - 17/1/2007  8:16 PM

This will change the way the navy goes about power projection and once again put the gun carrying surface ship as the most important ships in the fleet.

Submarines are today's capital ships.  Surface ships are just targets.  ;)

 - Ed Kyle
Title: Re: Navy rail gun breaches atmosphere
Post by: on 01/18/2007 02:59 PM
Quote
kevin-rf - 18/1/2007  8:35 AM

Quote
bhankiii - 18/1/2007  8:24 AM
You could put some fins on the back to get some spin - that would improve the accuracy.  At $1000 a pop you can fire 1000 for the cost of a cruise missile.  Surely you'll hit something.

A fin will behave how at those speeds? You could groove the projectile body to cause it to spin. The sad part mentioned in the article is the acceleration is to high for current electronics. So no terminal guidance...

There was some interesting news on ultra capacitors from eestore over at hobby space this morning. http://hobbyspace.com/nucleus/HSblog.php?itemid=3186

It would help with the energy storage for these devices.

I'm sure there's some appropriate hypersonic solution to make the things spin.  The electronics solution is being worked - gotta have those smart cannon shells.  

There's also a discussion of ultra caps going on at cr4:

http://cr4.globalspec.com/

which, BTW, is where I got this news article.

Title: Re: Navy rail gun breaches atmosphere
Post by: Chris Bergin on 01/18/2007 10:15 PM
Quote
stargazer777 - 18/1/2007  9:16 AM
Yes, but meanwhile other advanced weapons technologies are also advancing.  Directed energy and laser weapons for sea based, land based, airborne and space based applications are also rapidly being developed.  It will certainly make things interesting.

Interesting attachments - very much appreciated.
Title: Re: Navy rail gun breaches atmosphere
Post by: rsp1202 on 01/18/2007 11:20 PM
http://en.wikipedia.org/wiki/Kinetic_bombardment
http://www.donaldsensing.com/2004/07/rail-guns-for-navy.html
http://www.arclight.net/~pdb/illos-comm/
http://www.nuvo.net/nuvoBB/viewtopic.php?p=4323&sid=ebeb118d858bff2128caf768d82318c1
Title: Re: Navy rail gun breaches atmosphere
Post by: simonbp on 01/19/2007 04:48 PM
Quote
edkyle99 - 18/1/2007  9:27 AM

Submarines are today's capital ships.  Surface ships are just targets.  ;)

But what do you mean by capital ships? Nuclear missile subs are one-shot surface bombardment platforms, and most likely targets in any ship-to-ship engagement. Attack subs can be effective against other subs or a lone surface ship, but useless against a properly organised surface fleet or convoy.

A DDX-style dreadnought (and they are about as big a WWI dreadnought) with massive railguns and a swarm of UAVs can physically command a swath of open sea, able to detect and instantaneously attack any ship (surface or not) within its sphere. That is a capital ship...

Simon ;)
Title: Re: Navy rail gun breaches atmosphere
Post by: kevin-rf on 01/19/2007 10:42 PM
and the tomahawks just take up space in the launch tubes on attack subs? They can get in close, fire and get out, a surface ship lacks stealth and needs a fleet to back it up. The LCS is an interesting concept, swarm the enemy with several small low cost ships spreading there resources thin and lauch a massive bombardment from them.

Might be a dumb question, but if a section of the slug was Al, is there enough energy in the impact to vaporize and ignite it?
Title: Re: Navy rail gun breaches atmosphere
Post by: TyMoore on 01/20/2007 12:22 AM
O.K., let's do some basic physics. There is a lot of really good information on the current Naval gun system: the Mk 45/54 Caliber 5 inch gun system at:

http://www.globalsecurity.org/military/systems/ship/systems/mk-45.htm

The muzzle energy of this system is 10-18 Megajoules (10 MJ for the Mk45/Mod 4, and 18 MJ for a more advanced unit with longer barrell and probably different propellant.) Project weight is probably somewhere in the neighborhood of 50-70 Kg (110 lb to 154 lb.) This gun system has a 'regular' range of 13 nautical miles, but with extended range ammunition (advanced rocket boosted, GPS guided munitions) this can be extended to 40 n.m.

Running some numbers for the Mk45:

Since KE=1/2*m*v^2 then rearranging to solve for "v" we get:

v=sqrt(2*KE/m)

For a projectile mass of 50 kg, muzzle energy of 18 MJ, we can expect to get about

v=848.5 m/s or about 2780 ft/s (a little slower than a 30-06 rifle bullet for you hunters out there!)

One of the number's 'tossed out' was Mach 5 projectile. Using this number as a WAG let's run some numbers.

Since Mach 5 at sea level is about 5*1043 ft/s=5215 ft/s. Let's use a muzzle velocity of 1 statute mile per second, 5280 ft/s, or 1600 m/s for metric buffs.

Let's look at a 20kg projectile of depleted uranium (this will be a dart about 5 cm in diameter with a 6 degree cone half angle and about 60 cm long (about 2 feet.) With a muzzle velocity of 1600 m/s, this project will have a muzzle energy of about:

KE=1/2*20kg*(1600m/s)^2

KE=25.6 Megajoules or about 70% more than the muzzle energy of the much heavier MK 45 shell.

This thing would definately pack a wallop! Incidently the "other" reason for choosing depleted urainum in armor defeating rounds has nothing to do with its density. It is that uranium metal is naturally pyrophoric--which means it burns spontaneously on contact with air when finely divided into powder. Well the impact of a highly energetic but very dense projectile will create jets of material that spalls of the penetrator as it flows through the steel armour. This jets of material will finely divide into microscopic droplets, which almost instantly burn in air. The net result is a catastrophic explosion inside whatever is penetrated all because of kinetic energy and pyrophoric chemicals. Inserting a pin of aluminum in the middle probably won't add too much to this, but I'm pretty sure it would burn just fine if it were a jacket.

Larger, faster projectiles are certainly possible and likely, especially if the Navy want's to go for guided munitions.

The problem is acceleration--rather too much of it. A rail gun projectile will accelerate pretty close to 100,000 g's which is about 10 times the g load of a conventional projectile: this means more difficult to engineer electronics with probably less capability. Longer barrels can help alleivate this, but that makes the weapon less compact. It's an interesting concept...
Title: Re: Navy rail gun breaches atmosphere
Post by: Polecat on 01/21/2007 05:23 AM
Maybe China was responding to this ;)
Title: Re: Navy rail gun breaches atmosphere
Post by: simonbp on 01/21/2007 07:14 PM
Quote
TyMoore - 19/1/2007  7:22 PM

The problem is acceleration--rather too much of it. A rail gun projectile will accelerate pretty close to 100,000 g's which is about 10 times the g load of a conventional projectile: this means more difficult to engineer electronics with probably less capability. Longer barrels can help alleivate this, but that makes the weapon less compact. It's an interesting concept...

I know some people a specialty soldering company here in Huntsville (whose main business is Army and NASA missiles) who are working on integrating the chip die directly on the PCB, specifically for high-G applications...

Simon ;)
Title: Re: Navy rail gun breaches atmosphere
Post by: on 01/21/2007 07:49 PM
Where there's a will and a government contract, there's a way.
Title: Re: Navy rail gun breaches atmosphere
Post by: stargazer777 on 01/22/2007 12:20 AM
Thanks Chris.  You should also check out the latest Aviation Week lead story on this topic:  http://www.aviationweek.com/aw/generic/story_generic.jsp?channel=awst&id=news/aw012207p1.xml