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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

#221

Post by killjoywashere »

flukus wrote: post #219
derefr wrote: post #49

Earlier quoted context omitted.

It's not like the technology behind railguns hasn't been stable and ready to use for decades now. It's just that, until the more recent invention of ancillary technologies like supercapacitors, it's been so costly to fire them that there was no logical place for them on the battlefield, so we never bothered to operationalize them.

I'd be interested to know why we haven't seen intermediaries that don't need the advanced tech of a rail gun, like why haven't we seen magnetically driven mortars or artillery? These seem less demanding, is it just a case of existing tech being good enough?

The energy density of batteries is relatively low compared to the liquid hydrocarbons and other chemical accelerants. It goes from being a mortar you can throw in the back of a Jeep, to a mortar you can throw in the back of a Jeep plus a semi truck full of battery capacity.

On ships and airplanes, you can replace internal weapons bays which have substantial storage capacity. And the batteries (this is particularly an issue for airplanes) aren't terribly mass-dense either. And you can use the vessel's turbine-powered electric generators to recharge the batteries from fuel (this reduces the range, but hey, tankers).

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

#222

Post by PopeDotNinja »

steve19 wrote: post #200
mabbo wrote: post #135

Earlier quoted context omitted.

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…

You put it well. The problem of of putting energy into projectiles caused a move from kenetic to chemical weapons (missiles). But delivering chemicals to a target is expensive and at some point scaling it up becomes politically dangerous (you cannot just lauch even a conventional icbm without all sorts of risks). Scaling up kenetic weapons ended up with huge battleship guns that did almost as much damage to the ship…

> ...huge battleship guns ... were slow to fire ...

I was curious about how fast battleships could actually fire, so I googled around and found a couple stats.

On an Iowa class battleship:

- Armed with nine 16"/50 caliber Mark 7 guns [1]

- Each 16" gun is quoted as having a firing rate of 2 rounds per minute [2]

- Each shell weighed between 1900lbs / 865kg and 2700lbs / 1225kg pounds [3]

So math says 2 rounds/minute * 9 guns is 18 shells/minute. That is 34_200 lbs (18 * 1900) and 48_200 lbs (18 * 2700) of ordinance per minute. I would not want to be on the receiving end of that!

EDIT: fixed some numbers I goofed after @CapricornNoble was kind enough to point them out. Thanks!

[1] https://en.wikipedia.org/wiki/Iowa-class_battleship#Main_bat...

[2] https://en.wikipedia.org/wiki/16%22/50_caliber_Mark_7_gun#Se...

[3] https://www.cs.mcgill.ca/~rwest/wikispeedia/wpcd/wp/i/Iowa_c...

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

#223

Post by tdxcbkifxxxx »

fnord77 wrote: post #157

I wonder how durable these will be in combat Seems vulnerable to damage during a battle. A couple stray bullets or shrapnel hitting those power cables would put it out of commission unless it was heavily armored. where as they would just ping off an old-timey cannon harmlessly.

Go back to playing video games. That's the dumbest comment I've read all week

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

#224

Post by steve19 »

PopeDotNinja wrote: post #222
steve19 wrote: post #200

Earlier quoted context omitted.

You put it well. The problem of of putting energy into projectiles caused a move from kenetic to chemical weapons (missiles). But delivering chemicals to a target is expensive and at some point scaling it up becomes politically dangerous (you cannot just lauch even a conventional icbm without all sorts of risks). Scaling up kenetic weapons ended up with huge battleship guns that did almost as much damage to the ship…

> ...huge battleship guns ... were slow to fire ... I was curious about how fast battleships could actually fire, so I googled around and found a couple stats. On an Iowa class battleship: - Armed with nine 16"/50 caliber Mark 7 guns [1] - Each 16" gun is quoted as having a firing rate of 2 rounds per minute [2] - Each shell weighed between 1900lbs / 865kg and 2700lbs / 1225kg pounds [3] So math says 2 rounds/minute…

Interesting but I don't think that's sustained fire.

You see crazy him rpm for firearms. The rate of fire is restricted by the magazine size (ship guns do have magazines) and how fast the gun can cool.

The US Army changed the barrel of the M4 Carbine (automatic rifle) after some troops during a sustained defense of some hill had barrels failing after glowing white hot. Machine guns often have barrels that can be replaced during prolonged engagements.

A hot naval gun could detonate the charge if it overheats. It has happened although I don't remember how long ago.

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

#225

Post by CapricornNoble »

PopeDotNinja wrote: post #222
steve19 wrote: post #200

Earlier quoted context omitted.

You put it well. The problem of of putting energy into projectiles caused a move from kenetic to chemical weapons (missiles). But delivering chemicals to a target is expensive and at some point scaling it up becomes politically dangerous (you cannot just lauch even a conventional icbm without all sorts of risks). Scaling up kenetic weapons ended up with huge battleship guns that did almost as much damage to the ship…

> ...huge battleship guns ... were slow to fire ... I was curious about how fast battleships could actually fire, so I googled around and found a couple stats. On an Iowa class battleship: - Armed with nine 16"/50 caliber Mark 7 guns [1] - Each 16" gun is quoted as having a firing rate of 2 rounds per minute [2] - Each shell weighed between 1900lbs / 865kg and 2700lbs / 1225kg pounds [3] So math says 2 rounds/minute…

A few minor corrections. The 16-23 rounds/minute is for the secondary battery of 5" guns, not the primary battery of 16" guns. If you watch a video of the loading/firing process of a 16" inch gun you'll quickly see why a firing rate of 1 round per 3-5 seconds is physically impossible.

So 2/min * 9 guns * [900kg;1225kg]/gun =

16,200kg/min high explosive broadside or

22,050kg/min armor piercing broadside

Your concluding sentence is 100% correct: best to be somewhere else.

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

#226

Post by CapricornNoble »

mikeash wrote: post #215
aeneasmackenzie wrote: post #212

Earlier quoted context omitted.

You use an extremely long track, not high acceleration.

Hard to do if you’re aiming straight up.

You'd have to re-purpose something like a deep mining shaft from a diamond mine, then stick a giant rail gun in it, almost like Germany's V-3 cannon[1] but on steroids.

[1]https://en.wikipedia.org/wiki/V-3_cannon

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

#227

Post by charlesju »

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.

Maybe I should rephrase and emphasize that I think this is interesting not necessarily immediately practical. From what I understand about rail guns, they're not even practical yet to deploy for military ground to ground purposes, let alone to get things into space.

I think I'm taking a lot of liberties to imagine a future where we figure out a ton of challenges to get all the engineering to match the theory of making this happen. And in general, I believe we should take an optimistic approach to the future, given that getting humans into space in scale would be a marvelous accomplishment for the human race.

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

#228

Post by ChuckMcM »

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…

I don't disagree, at 100,000 feet all weapons are mass gets propelled by force, where I part ways with you is here:

"A rail gun isn't much different"

While I completely agree that in concept rail gun isn't different, making one is extremely different. That is why I would have little trouble making a bow and arrow over the weekend that would serve as a respectable weapon[1], but I would not be able to create a similarly lethal rail gun[2]. Reducing the theory to practice is neither straight forward nor obvious. People have been trying to build them for 100 years after all and we're only now seeing some that come close to being competitive with other weapon systems.

What I'm saying is that your "overhead in terms of gear to make it work" covers for a whole crapload of technology and engineering.

What I hear when you dismiss this technology is a lack of appreciation for what is involved, it sounds to me like someone saying "Making an atom bomb is pretty simple right, simply hold a super-critical mass of fissile material really tightly until you've achieved the desired number of fission events. Right?" But you can't pick up two 4 lb pieces of plutonium and bang them together like a couple of rocks and expect to get a bomb event (although you will die). There is nothing "simple" about it, even if the concept is easy to express.

[1] In part because we learned how to make bows in Boy Scouts and I spent a summer doing a survival course where I had the opportunity to build one for my final.

[2] Even though I'm a classically trained EE, understand the theory, have experience in switching fairly high currents from my Battlebot experiences and a fairly complete EE lab at my disposal.

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

#229

Post by CapricornNoble »

vkou wrote: post #138
asark wrote: post #117

Earlier quoted context omitted.

Explosives are really dangerous to carry around. Go looking through the fates of ships lost in WWI and II (last time there was a fair amount of ship combat going on) and there's an awful lot of "several rounds hit but everything was basically fine, except then one hit the magazine, blowing the ship in two and sinking her", or a fire starting and doing something similar, or a smaller cache of explosives readied for im…

It wasn't even shells hitting magazines. It was shells hitting gun turrets, with the explosions reaching the magazines. In the Battle of Jutland (The largest naval battle of WWI), the Royal Navy lost three capital ships (Two battlecruisers and a heavy cruiser) to single shells that struck their gun turrets, detonating their ammo magazines. The gun turrets were, in theory, supposed to be sealed off, by blast doors, fr…

As an addendum:

The Royal Navy had a long and well-established tradition of exceptionally well-drilled gun crews, probably going back almost 150 years from WWI through the Napoleonic era. It could be argued that their fast-firing and disciplined gunnery were decisive in more than one British victory.

HOWEVER....as you point out this led to objectively-suicidal practices....What's that term for when you've been doing a risky job for so long you don't realize how dangerous your habits are? Yeah Royal Navy gunnery is a textbook example of that.

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

#230

Post by sandworm101 »

Some forgotten limitations of railguns: There is a maximum speed for projectiles in naval warfare. Earth is round. So anything moving too fast (~8000m/s) simply cannot hit distant targets. If fired horizontally, the shell will climb up as the earth curves away. This causes all sorts of difficulties if trying to attack another ship. At best, your shells will hit horizontally, far above the waterline. You would need a shell that could either fly itself downwards, bleeding speed, limiting penetration, and defeating the point of using a railgun.
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