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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

#211

Post by drewbt »

toss1 wrote: post #115
drewbt wrote: post #55

Earlier quoted context omitted.

How does it work, how should it work, and what are we doing about it?

How it works now is that some percentage of the humans want to become, and/or want to support authoritarian rule. Authoritarian rule always wants to expanad, and will treat both it's subjects and other people as objects. How should it work? Like eradicating smallpox, we'll need to somehow engineer, or teach, or by some other method, eradicate from the entire human race the authoritarian impulse. Until then, the choic…

“Hi Drew/Glenda It is with great pleasure to see the project at this stage. We have yet once again proved the sceptics, nay sayers and persmists wrong. From a plain field to a sight commanding building that yields hope to drags of our society and the future itself. Despite of the hindrances we have encountered along the way, I am humbled, awed and jubilant to have been a part of such a gesture. In this money fueled life style I would also been delighted to have made myself a fortune in building such a building that is going to make a difference in many people's lives but the greatest fortune of all is the joy I find in knowing that these hands have built such a meaningful building. The project may have come to its end but the memory will linger in my heart forever. This hasn't only equipped me with skills but changed the way I view life. It is this reason that I would love the organisers to allow us to keep the tools we have used in building the hope and the future of our society so that we can continue putting bread on our tables and helping those in need of our assistance. My humble thanks to all those who selflessly opened their check books and offered with their hard earned cash to the project, and not forgetting those who could not offer funding but took it upon themselves and used their precious time to personally give a hand in this project. This project is a full proof that humanity/Ubuntu still exists. Regards Michael Dyasi”

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

#212

Post by aeneasmackenzie »

mikeash wrote: post #174
Zelizz wrote: post #145

Earlier quoted context omitted.

I think they were suggesting that you could save fuel for once you're out of atmosphere, so that you're not fighting air resistance when you start a burn to get into orbit.

You could save a decent chunk of your fuel this way. Maybe 25% or so. In exchange for that, you have to build your rocket and satellite to withstand 10,000 gees of acceleration and hypersonic flight through the lower atmosphere. And somehow build a rail gun that can fire something the size of an office building.

You use an extremely long track, not high acceleration.

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

#213

Post by DuskStar »

sharpneli wrote: post #122
SEJeff wrote: post #38

Earlier quoted context omitted.

But the US Military uses depleted uranium (the hardest material) for tank rounds, so they could make pretty hardy railgun projectiles.

Not the hardest. Bit less than Tungsten so pretty hard but far from hardest. It is used because it is really really dense and hard enough. Perfect for piercing armor.

Depleted uranium also has a few other wonderful qualities - one is that it's self-sharpening, as the nose of the projectile will shear instead of deforming [0]. Another is that uranium burns in such situations, which means you get 'incendiary' for free.

0: https://en.wikipedia.org/wiki/Staballoy

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

#214

Post by keiru »

fooker wrote: post #170
keiru wrote: post #158

Earlier quoted context omitted.

"shoot satellites out of orbit", not "into orbit"

Same fundamental problem.

On top of everything else commented, there's the matter of how delicate you need to be about it. I do hope no one ever tries to down a satellite with a railgun, as debris might create a runaway effect that brings about a dark night. Use lasers, be responsible.

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

#215

Post by mikeash »

aeneasmackenzie wrote: post #212
mikeash wrote: post #174

Earlier quoted context omitted.

You could save a decent chunk of your fuel this way. Maybe 25% or so. In exchange for that, you have to build your rocket and satellite to withstand 10,000 gees of acceleration and hypersonic flight through the lower atmosphere. And somehow build a rail gun that can fire something the size of an office building.

You use an extremely long track, not high acceleration.

Hard to do if you’re aiming straight up.

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

#216

Post by FreeFull »

xyzzy_plugh wrote: post #127
coder543 wrote: post #58

Earlier quoted context omitted.

Railguns are not coilguns. Railguns maintain physical contact between the projectile and the rails for the entire length of the barrel. That's a lot of friction. Friction leads to heat, light, and a puff of smoke from material that has been ablated during the launch, if I were to guess. This leads to one of the big problems with railguns, which is that you have to replace the rails frequently due to wear and tear.

They don't need to maintain physical contact. You can have an air gap, as long as the circuit shorts through the projectile. The rails still wear down.

If you have a gap, then you end up with electrical arcing which generates even more heat

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

#217

Post by wiml »

noir_lord wrote: post #120
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.

Space. The propellant for a large shell takes up more space than the shell it fires, it's tremendously dangerous to have around from both accidents and enemy impacts. Compared with a rail gun which is room full of exquisitely machined inert metal blocks. Cost - Those inert machined metal blocks are cheap in a military if not absolute sense.

Though, this only really makes sense on a nuclear-powered ship. You've got to store your energy somehow, and I'm sure gunpowder is less energy-dense than diesel fuel, but from what I've read one of the big attractions of electric weapons is that you can replace all that chemical energy storage with far, far denser nuclear energy.

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

#218

Post by learc83 »

hollerith wrote: post #72
bin0 wrote: post #50

Earlier quoted context omitted.

We've been stockpiling nukes for a half-century, and only ever used two. I would contend that the two which were used were a net benefit in terms of what it would have cost (in both American and Japanese lives) to invade the islands. Of course, the threat is only good if the nation doing the threatening is willing to use it, so the merits of stockpiling are still arguable. With that said, they were something of a too…

> the two [nukes] which were used were a net benefit in terms of what it would have cost (in both American and Japanese lives) to invade the islands. There was no need to invade the islands. For the last year of the war, the Japanese had severe problems importing supplies. A significant fraction of their imports were coming in on tiny wooden ships: larger ships and steel ships would probably be sunk by US submarines…

I agree that the decision to use the bomb wasn't purely (probably not even mostly) based on the desire to limit loss of American and Japanese life. I'm also not saying I necessarily agree with the decision, but an extended siege would surely have caused massive food shortages. By the end of the war Japanese daily rations were already barely above the minimum long term daily requirements, and by 1946 even with US aid, rations were at 65% of minimum daily requirements.

I don't know how many Japanese would have died because of a siege, but it seems likely that if the siege took an extended amount of time, it would be more than died during the bombings.

Additionally in the alternative scenario where the Soviets invade, you'd still likely have a higher death toll. And there is also the continuing deaths of Civilians and POWs in Japanese occupied Manchuria that would have continued until the Soviet invasion was successful.

I don't think I could order a nuclear attack or support a politician who did--but from a purely utilitarian perspective, it's not an easy decision.

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

#219

Post by flukus »

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'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?

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

#220

Post by killjoywashere »

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…

Point of order in the definitions here: an explosive projectile is still a kinetic weapon and is not NOT a chemical weapon. A chemical weapon causes chemistry to happen in/on the target: mustard gas, VX nerve gas, etc.

This is not my opinion. This is widely accepted and a matter of many international treaties.

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