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US Navy's Railgun Now Undergoing Tests in New Mexico

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Re: US Navy's Railgun Now Undergoing Tests in New Mexico

#201

Post by chillwaves »

DuskStar wrote: post #101
charlesju wrote: post #97

Earlier quoted context omitted.

I think the interesting use case would be to put things into space for a lot less money. Imagine putting one or many of those new Space X internet satellites into a rail gun that goes straight up. It doesn't need to go all the way into space, it just needs to get pretty high, then the cost to break into orbit can require a lot less fuel and make it a lot more cost effective to do space stuff.

> Imagine putting one or many of those new Space X internet satellites into a rail gun that goes straight up. Orbit doesn't work like that. Getting 200, 300 miles up is the easy part - the vast majority of the required energy comes from going sideways at 7800m/s.

Could the targeting system account for the sideways movement?

Re: US Navy's Railgun Now Undergoing Tests in New Mexico

#203

Post by stcredzero »

ohaideredevs wrote: post #54
stcredzero wrote: post #7

It looks right. It looks like it could well be the ancestor of the MAC cannons from Halo. EDIT: I said this to my coworkers a couple of weeks ago: I'm calling it now. Either 1) Naval Railguns also wind up being killer AA weapons and there aren't any game changers in submarine warfare or 2) Railguns are going to be the equivalent of WWII naval cannon -- They won't be nearly as important as something else.

"2) Railguns are going to be the equivalent of WWII naval cannon -- They won't be nearly as important as something else." Railguns would completely surpass missiles for StS warfare, which can be intercepted by other missiles, whereas a railgun shot cannot at this time.

Railguns would completely surpass missiles for StS warfare

Yes, but my thought is that it's possible that in the future, no one is going to care about surface warships shooting each other. My full prediction is: Either 1) Naval Railguns also wind up being killer AA weapons and there aren't any game changers in submarine warfare or 2) Railguns are going to be the equivalent of WWII naval cannon.

Navies will be important, but what people will care about is 1) the ability to interdict shipping, 2) the ability to prevent amphibious landings, and 3) the ability to project power. It's possible that technology will get to a point where ships fighting ships with guns is irrelevant to all three. One possibility is that navies will develop swarms of autonomous AI minisub drones which can deny the sea to surface ships. Autonomous flying drones could also yield such a change.

So let's say there is some game-changing development like the ones mentioned above, such that surface ships within a certain range of the enemy are no longer viable in combat. What will happen to the big railgun equipped ships? They will be relegated to shore bombardment, but only once air superiority has been established, and all other opponents have been neutralized: Just like their WWII forebears.

(If railguns can become killer AA weapons, then my prediction 1) applies. I'm not certain this will come to pass, however.)

Re: US Navy's Railgun Now Undergoing Tests in New Mexico

#204

Post by UnpossibleJim »

Zelizz wrote: post #151
UnpossibleJim wrote: post #134

Earlier quoted context omitted.

It isn't only that, with a powder charge you are pushing the projectile with an explosion. That explosion will also cause a disturbance on a ship, until you get to a pretty enormous size, you have to calculate that into your trajectories. With a railgun, you have a series of magnets pulling a projectile forward incrementally faster. It's a lot less energy wasted into the environment, meaning a lot less energy put bac…

What you are describing is a coilgun, a railgun uses a slightly different principle.

Oh. Ok, I'll have to look into that. New project to look into for the summer =)

Re: US Navy's Railgun Now Undergoing Tests in New Mexico

#205

Post by dghughes »

mabbo wrote: post #135
ChuckMcM wrote: post #44

I find the physics of rail guns pretty fascinating. For something nominally invented in world war 1 (1918) which is now "only a few years" away from possible deployment. We are talking literally a 100 years later. We went from powered flight to flying in orbit in less time, think about that. Is it a compelling weapons concept? Of course it is, you don't need explosives to shoot things that is pretty huge. Are wars ba…

The concept is the same for any projectile weapon: I'm going to convert stored energy into kinetic energy. Bow and arrow? Stored energy in the bow turned into kinetic energy in the arrow. Handgun/cannon/musket? Stored chemical energy in some compound, quickly converted into kinetic energy in the bullet via exploding. A rail gun isn't much different- it's just a different means to store the energy (in electrical stora…

Rail guns will be powerful but powerful chemical energy LASER weapons will be frightening without projectiles, instant, no recoil, fast aim.

Re: US Navy's Railgun Now Undergoing Tests in New Mexico

#206

Post by ThrustVectoring »

Fej wrote: post #73

Why have coilguns not gotten the same amount of attention as railguns?

Coilguns have physical limitations that make them unsuitable for extremely high velocity applications. Specifically, the engineering difficulty in switching the coils on and off scales with the square of the currents used in a coilgun.

Any inductor has a rate of change of current proportional to the voltage across the ends. So all else equal, if you double the current, you double the switch-on and switch-off times. But, since you're using higher energies, you're getting a faster projectile - which means you now need to switch the coil off faster as well, to prevent suck-back.

So in short, coilguns get significantly harder to build at higher energies. In contrast, railguns get more energy efficient as projectile velocity increases.

Re: US Navy's Railgun Now Undergoing Tests in New Mexico

#207

Post by ThrustVectoring »

leetcrew wrote: post #86
Fej wrote: post #73

Why have coilguns not gotten the same amount of attention as railguns?

I'd guess the main reason is that it's an inherently more complicated design; if you don't sync the electromagnets perfectly you spend energy decelerating the round. it does have the advantage that the projectile doesn't need physical contact with an electified rail, so maybe it could be less damaging to the device itself.

The coils are inductors, and so cannot be turned off instantaneously - you get a voltage across them proportional to how quickly you're changing the current. As you build a faster coilgun, it gets harder to deal with the voltages generated by the sharper current pulses necessary to do useful work. And presumably you're also increasing the current involved to get higher velocity, which also contributes to the engineering difficulties involved in managing the coil voltages.

Re: US Navy's Railgun Now Undergoing Tests in New Mexico

#208

Post by timerol »

mcguire wrote: post #114

1) " The system charges for two minutes... " One shot per two minutes is pretty bad; the current 5" gun shoots 16-20 rounds per minute. 2) "...at speeds up to Mach 6." One of the issues with old school, large caliber naval guns was that the blast from the guns would damage or destroy equipment near the muzzle. (I was just reading Pursuit by Ludovic Kennedy, about the British pursuit of the Bismark, and (IIRC) one shi…

A previous article mentions a "a five shots per minute minimum goal": https://www.thedrive.com/the-war-zone/12716/watch-the-navys-...

Re: US Navy's Railgun Now Undergoing Tests in New Mexico

#209

Post by jbattle »

dogma1138 wrote: post #119
openasocket wrote: post #116

I've never quite understood why we need to change technologies so completely to get the projectile moving faster. As in, why couldn't we do the same thing by just making a bigger explosion in the barrel? I assume there's some point of diminishing returns or inefficiency that makes it impractical, but I haven't been able to find a source that gives the math to explain it.

To make a bigger explosion you need a bigger barrel and more powder charges. Eventually you hit a limit where you simply can’t create enough pressure to propel the projectile faster and not turn the barrel into a pipe bomb. For the most part many guns have already hit their practical limit in this regard. There is a good reason why battleships fell out of favor other than the US being the only blue water navy after W…

The real reason battleships fell out of favor is that aircraft (and eventually missiles) are better at basically everything.

Re: US Navy's Railgun Now Undergoing Tests in New Mexico

#210

Post by DuskStar »

chillwaves wrote: post #201
DuskStar wrote: post #101

Earlier quoted context omitted.

> Imagine putting one or many of those new Space X internet satellites into a rail gun that goes straight up. Orbit doesn't work like that. Getting 200, 300 miles up is the easy part - the vast majority of the required energy comes from going sideways at 7800m/s.

Could the targeting system account for the sideways movement?

Do you mean in order to use this as an ASAT or ABM system? In that case, probably - though you'd still need some sort of terminal guidance to actually achieve a hit.

If you mean "account for the sideways movement" as "give the satellite the horizontal component of the required orbital velocity" this doesn't work for a variety of reasons - #1 is that the railgun is 2000m/s and orbit is 7800m/s, and #2 is that things going 7800m/s (17450mph) at or near sea level tend to get very, very hot very, very quickly which is not particularly great for railgun projectiles and utterly disastrous for things like solar panels.

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