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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

#191

Post by velosol »

crimsonalucard wrote: post #159
grenoire wrote: post #144

Earlier quoted context omitted.

Is it really that humidity in the air is classified as steam?

No steam references entropy or distribution of the molecules in the air. Concentrated water molecules visible as myst produced from hot water is steam. The water molecules evenly dispersed in the air is humidity.

>Concentrated water molecules visible as myst produced from hot water is steam.

Steam/water vapor/humidity is gas phase H2O and is transparent. Water droplets in air is often referred to as 'steam' or 'wet steam' but is liquid phase H2O suspended in air. If it mattered in context I assume it would be clearly stated as gas rather than liquid mist.

I doubt anyone would call the component of air that is 'humidity' by the word 'steam' but it seems it would be correct [1]. I am used to the term 'water vapor' for that gas phase H2O though.

[1] https://www.wordnik.com/words/steam

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

#192

Post by SEJeff »

RantyDave wrote: post #184
SEJeff wrote: post #141

Earlier quoted context omitted.

So perfect for a railgun projectile? :) What is the hardest man-made substance?

Artificial diamond? But it doesn't matter - you don't actually want something hard because you don't actually want it to go all the way through and out the other side. You want it to dump all that lovely kinetic energy into whatever it's hit.

Yeah, DU has an incendiary property along with a "self sharpening" property. It doesn't mushroom as much when used as a sabot round as tungsten. My platoon sergeant in the US Army was a former tanker and we learned all about it (I flew the Shadow 200 TUAV).

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

#193

Post by ars »

logfromblammo wrote: post #133
ars wrote: post #110

Earlier quoted context omitted.

> would be instantly squished Not so. That's only for a very short launch. You would actually have a track a few miles long (probably up the side of a mountain) and launch using that. The g-forces would be very mild.

You need about 1200km to reach LEO from the equator with max acceleration of about 3G. I did the math once, and a track from the Galapagos Islands to the peak of Chimborazo on the continent in Ecuador would do it.

I was a little shocked at that number, so I ran the math again, and wow.

Quite a bit longer than I expected.

Maybe a circular track till you build up speed, then switch over to the mountain track?

Of course the circular track would have g-forces due to that..... (Do you feel like doing more math?)

I guess it's more practical to use the track just for the initial boost above the atmosphere, then a rocket to add speed. Also a track that can handle something moving at km/s is .... not easy.

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

#194

Post by saalweachter »

mikeash wrote: post #172
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…

For a more extreme example: it took less than seven years from the discovery of nuclear fission for this discovery to be used obliterate cities.

On the other hand, consider the time it too to develop gunpowder projectile weapons to the point that they were useful.

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

#195

Post by gricardo99 »

RantyDave wrote: post #177
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…

No because "chemical" guns accelerate their loads by putting enormously high pressure gases behind them. Obviously, then, once the load is off the gases spew out the end (and make a really, really loud bang noise). Railguns, IIRC, use a chemical charge to get the first couple of mach but then the magnets to pull the load to full speed so it's not followed out the barrel by a mountain of hot gas. The flames you see co…

Thanks, that answers a question I had about the flames/discharge after the round exits. I expected to see nothing other than the round.

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

#196

Post by mikeash »

saalweachter wrote: post #194
mikeash wrote: post #172

Earlier quoted context omitted.

For a more extreme example: it took less than seven years from the discovery of nuclear fission for this discovery to be used obliterate cities.

On the other hand, consider the time it too to develop gunpowder projectile weapons to the point that they were useful.

Indeed. I guess a century or so of development isn’t so bad by comparison.

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

#197

Post by Animats »

derefr wrote: post #49
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…

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've been wondering when EMALS catapults get converted to ultracapacitors. The current energy storage system on the Ford class carriers is a motor/generator/flywheel setup, and it's a reliability headache. The catapult itself is just a linear induction motor.

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

#198

Post by salty_biscuits »

salty_biscuits wrote: post #139
pneill wrote: post #51

Does anyone know why there is a flash of light and a puff of smoke when the gun fires? Since it's electromagnetic, you'd think you wouldn't see anything.

The old designs used to use copper behind the projectile. The current would make it vaporize and be a conducting gas/plasma thing to push the projectile along with the lorentz force.

I was stretching back in my memory about this stuff so had to read up again, the term they use is a "plasma armature" or "hybrid armature". I haven't been able to find out what this one uses in a quick search around.

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

#199

Post by fkdo »

maccam94 wrote: post #183
xyzzy_plugh wrote: post #131

Earlier quoted context omitted.

Indeed, we don't typically resort to shooting bullets at bullets to defend incoming gunfire.

https://en.wikipedia.org/wiki/Trophy_(countermeasure) (Granted, it's more anti-missile than anti-bullet)

Missiles are bigger (they carry their own engine and fuel), are in the sky longer due to their longer range, and shooting missiles from the sky has never been implemented with a high success rate in active combat.

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

#200

Post by steve19 »

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…

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 itself as the target (OK, a bit of an overstatement but I doubt any of those sailors left the navy with hearing intact). They were slow to fire, extremely heavy, and required a lot of dangerous chemicals to be stored. One mistake and the ship would blow up.

This allows deep penetrating weapons containing huge amounts of energy to pierce bunkers from way over the horizon.

This is the kind of weapon the Navy will want if the Korean peninsula ever heats up to a boil.

Edit: I suspect I am being downvoted because I am discussing weapon systems. There is a difference between advocating for weapons/war and discussing them. It is better weapons are discussed in the open, than developed in secret where the public cannot weigh in. Truly horrifying things are born in the dark.

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