Navy Sets World Record With Rail Gun | Hacker News Reader

Navy Sets World Record With Rail Gun

foxnews.com

91 pointsgibsonf181 comments

This is great! When the Soviets come roaring through the Fulda Gap, or the Japanese descend on Pearl Harbor, we got 'em!

Oh, wait. We're preparing for the last war or even the one before that, all over again.

How does this help in the world of asymmetric warfare, failed states, nukes in container ships, and Stuxnet? (I'll bet the Maginot Line was pretty cool technology in its day as well.)

> I'll bet the Maginot Line was pretty cool technology in its day as well.

Definitely. Hidden tunnels with high speed trains to bring ammunition and personnel at any point in no time; hidden turrets in the forest that emerge from the ground; dragon teeth and minefields prevent tanks from going through.

Unfortunately big brass love big weapons, big bombers, big ships, big guns; never mind if they're useless nowadays in a world of guerilla and IEDs. The future is not the F22, it's a slow and cheap remote controlled drone with a propeller.

The future is not the F22, it's a slow and cheap remote controlled drone with a propeller.

It's a slow but highly efficient autonomous drone with GPS and a terrain map.

Well, you may be surprised by the increasing relevance of naval forces in our modern world. Even though big ships fighting Bismarck style is rare, big ships are still very useful in securing seaways for shipping. This is why China, India, S. Korea are all building up their navy. Sure, SpecOps / "terrorists" grab the headlines, but remember that countries have many other threats and don't openly promote them without cause.

Yes, spending $569,000 on a cruise missile to take out a merchant vessel of comparable cost wouldn't be good economic warfare doctrine. If the navy can develop weapons that can sink merchant vessels from 200 miles away with dirt-cheap munitions (like a dozen $1000 ceramic slugs) then this makes for a more credible threat.

They probably wouldn't be blowing up merchant vessels like U-Boats, but they certainly would still spend whatever money it takes though: Mark 48 torpedos are a cool $1M to $3.5M.

http://en.wikipedia.org/wiki/Mark_48_torpedo

I think the main advantage for rail guns are that they allow a much higher volume of fire and faster time to engage more targets. It just happens to use cheaper ammo - I'm sure the gun will be much more expensive to make than a standard machined barrel.

They probably wouldn't be blowing up merchant vessels like U-Boats

But a part of the point is that they could in theory.

they certainly would still spend whatever money it takes though: Mark 48 torpedos are a cool $1M to $3.5M.

This would be dandy for blowing up a submarine or major warship which costs a lot more. This might also be viable for "demonstrating" your capabilities one or several times. Sinking a major merchant marine fleet this way wouldn't be cost effective.

It just happens to use cheaper ammo - I'm sure the gun will be much more expensive to make than a standard machined barrel.

With a 200 mile stand-off range, a much more expensive gun would still make sense. The extreme range would make such a weapon more survivable. There would also be applications for land to shore fire support.

Point taken. Still, it leaves me wondering: what's the "rail gun" of diplomacy - e.g. how would serious money spent on R&D help us resolve the issue of Israel and the Palestinians?

And what's the "rail gun" for nation building - how would serious money spent on R&D help us create a stable, democratic Afghanistan?

I fear we're stuck in the "meta" version of "if all you have is a hammer": in terms of budget, all we have, in international relations, is the Defense Department. It has its uses, but its effectiveness is increasingly limited, not by dollars, but by our vision.

Lets get bunch of rails into the low polar orbit. Once a 1000 or so is deployed, there will be an almost-instant (20 minutes) strike capability for any location on the earth. The good part is that kinetic energy of re-entering rail will be unmatched by any railgun.

On the serious note, they didn't specify the weight of the projectile, and this is quite important factor. Comparison of the energy delivered at the target range to the energy delivered by the conventional winged missile would be useful as well.

Blog of the guy who build portable supersonic railgun at home (in Russian): http://railgun.org.ua/ Check out his video page: http://railgun.org.ua/video/

If you take the numbers from the article as accurate, 33 megejoules at Mach 7 means the weight is ~15kg (assuming I got all my conversions and orders of magnitude right, feel free to do your own e=1/2mv^2 calculation...)

I got ~10kg from the 2500m/s number, and under 12kg from the Mach 7 number. Google agrees:

http://www.google.com/search?q=2*33megajoules/(2500+m/s)^2+i...

http://www.google.com/search?q=2*33megajoules/(7+*+speed+of+...

Projectile speed will be much less after it has travelled 100km.

I don't think other world powers would be totally cool with us putting superweapons into low polar orbit right over their heads... you should totally expect those satellites to be shot down as soon as you put them up there.

Why would they shoot down relatively harmless rails from the orbit and not other already existing spy satellites?

because of offensive vs. defensive purpose?

You already have 20-30 minute strike capability for any location in world. You've had it for decades.

What you want is 20 minute strike with less warning than existing ICBMs. And also banned. The nuclear weapons reduction and restriction of weaponization of space treaties are some of the successful treaties with regard to controlling weapons that anyone, let alone the United States has been involved with. Violating said treaty will bring ridicule and anger to whoever breaks it, and a non-miniscule chance of the other major nuclear powers launching all their nukes.

As much as I would prefer otherwise, it seems pretty clear that space has already been weaponized. Between the Shuttle the X-37, and whatever else exists, for all we know there are already satellites in orbit armed with kinetic kill vehicles.

All satellites in orbit are already kinetic kill vehicles, just with varying degrees of sophistication. Everything in space is a kinetic kill vehicle. The idea that space can somehow not be weaponized is sheer physics ignorance. In some ways this is the largest challenge to space exploitation, which is rapidly becoming relevant as commercial spaceflight recently passed a milestone. A corporation that can retrieve an asteroid for mining purposes is a corporation that can drop that asteroid on your capital. There aren't very many realistic treatments of this scenario in "the literature". ("The Moon is a Harsh Mistress", at least the base scenario if not the details of the superintelligent computer, is one of the few.)

Maybe I shouldn't have used that term. I am aware of the basic physics of the situation, but that's not what I was talking about. I think it's likely there are already devices in orbit with the capability of launching "dumb" (i.e., non-explosive ) munitions to either take out other satellites or small targets on earth.

When people discuss the weaponization of space in terms of the treaties, implying ignorance because it isn't about basic physics doesn't provide any constructive input, and is frankly just needlessly hostile. These treaties are about weapons in a military sense, with the ultimate issue being the presence of nuclear weapons in orbit. I don't think it would be news to anyone that the whole business is inherently dangerous and that anything in orbit can come down anywhere on earth with little warning.

But that's the point. Anything nontrivial in space already is a military weapon. (Though most satellites are trivial by this measure, I'm really talking about the mid-term future.) It doesn't even have to be nuclear. It is not possible to really seriously use space without it being intrinsically weaponized. There's no such thing as non-weaponized space.

And no, I seriously doubt our political leadership really understands this at a gut level. You might even find some people in such positions that could pay lip service to the idea, but still don't really get it. You don't even need "nukes", which, frankly, are redundant pretty quickly and would only add a psychological scare factor.

I am absolutely with you in thinking that politicians don't get this at all. My main point is that there is a context in which those terms are used that doesn't immediately mean that anyone who uses them doesn't realize that mass in space == potential big boom somewhere.

>...for all we know there are already satellites in orbit armed with kinetic kill vehicles.

That seems more like pure conjecture than anything clear.

I do remember a PopSci article talking about doing it, but no one would dare admit it if they did.

By "strike capability" here I mean "small payload pin-point strike capability", not "nuclear warhead". But you are correct in that it's possible to use ICBM to deliver rail to the target.

How would you use ICBM to deliver rail?

By "rail" here I mean long prolonged heavy metallic object. Replace warhead with the rail and launch ICBM.

No, we need something cheaper.

ICBMs are too expensive to use to deliver conventional explosives or kinetic kill projectiles. Forget bioweapons and toxins, they're not any deadlier than cluster bombs.

The power of an explosion follows an inverse square law, so you can destroy something with 1/4 the explosive if you can get twice as close to it.

If you could drop thousands of 25 lb bomb equivalent devices an hour with GPS accuracy at a city, you could wreck it's infrastructure in a few weeks.

And wish nuclear death on yourself. You also already are developing that ability with Prompt Global Strike (essentially non-nuclear ICBMs).

I believe prompt global strike (and similar schemes) to be highly unstabalizing and to be avoided at all costs. The global suspicion (with a country with 2000k+ nukes none the less) would be suffocating. If the USA employed such a system, the moment you acted as anything less than a white knight, the world be up in arms. And justly. Your friends (the UK and Canada and Australia) would start edging away. And then you're truly fucked. (Canadian).

Reality check:

According to that logic, Canada should already have that attitude to the US, since most of their population is inside aircraft range...

Huh, why the minus votes? Is there anything wrong with the argument or is this political believers' reactions?

Airplanes [edit: and rocket artilleri, for that matter] in range is functionally the same thing as such a strike capacity, but cheaper.

There is no reaction from Canada and won't be; see the democratic peace theory.

Yea except that inconvenient treaty that states you can't put weapons in space. Oh and also if you try to do this China would just try to shoot it down anyways. http://en.wikipedia.org/wiki/Outer_Space_Treaty

A big rail gun is nothing new. The hard part, the part they still haven't figured out, is firing the thing without blowing it up at the same time.

Pretty awesome.

There's an unfortunate focus in the admiral's comments on ship-to-ship warfare, which really isn't something we get a lot of nowadays.

What's deliberately not mentioned is how useful this might be for shooting down a missile at launch. It is, as they say, hard to hit a bullet with a bullet. But hitting a bullet with a much faster bullet...

That's their main use

With a missile coming toward you at Mach 2-3 you don't want to be shooting subsonic cannon shells at it.

The rail gun ammunition is much smaller so you can carry much more of it and make a much more mobile gun turret because it doesn't need to store tonnes of shells or have a feed back to a magazine.

But if you look at the video, it's clear they're a long way from making any kind of agile turret out of this. It's HUGE.

It is not that big compared to the guns on a destroyer or a battleship. It is still large and bulky, but not that far off.

Current destroyer's gun: http://en.wikipedia.org/wiki/5%22/54_caliber_Mark_45_gun

Iowa Class gun: http://en.wikipedia.org/wiki/16%22/50_caliber_Mark_7_gun

Yeah. The part of the turret you can see when you look at the ship is only the tip of the iceberg.

They'll be able to hit incoming missiles, but the primary strength of the system is as long-range artillery for land attack. It won't have the rate of fire you'd need to defend yourself against multiple incoming missiles.

Thier main use will be hitting targets far in land.

The article says "Indeed, a railgun could be used to inflict just such harm on another vessel.", which is true, it could be used for this purpose, but they would not be sinking money into this just for that.

"[A] railgun offers 2 to 3 times the velocity of a conventional big gun, so that it can hit its target within 6 minutes."

I'd expect that most projectiles decay exponentially toward a terminal velocity, so the impact of shooting a bullet faster is negligible when it's going to be in flight for 6 minutes. Anyone know whether that's true for long range projectile weapons these days?

Railgun ammunition is designed to lose as little kinetic energy as possible. After all, there's no point hitting someone with a non-explosive projectile unless it's moving fast.

This suggests that the terminal velocity of a rail gun projectile is around Mach 5: http://www.globalsecurity.org/military/systems/ship/systems/...

I guess I can spend my time worrying about other things!

What is the possibility of using these for space launches?

edit: obviously would have to be slower then these for the sake of any fragile cargo (including people)...

Hard to imagine anything useful withstanding that acceleration. You could make a longer launch tower, but how tall would it have to be?

For humans who can survive an acceleration of about 3 g, you'd need a 1000 km long railgun in order to deliver enough energy.

For cargo a railgun a few miles long would probably be enough, but designing a missile which can survive surface air densities while travelling at orbital velocities would be very difficult.

Launching bulk cargo would still be a very worthwhile thing to do. Solar power satellites, anyone? The main obstacle is the launch cost. If we could reduce the shipment of bulk items to orbit to freight rates, then solar power satellites would become a reality. The US military already has specs for electronic components that can withstand 100,000 gravities. (Yes, the number of zeroes is correct!) I bet we could develop lightweight thin-film solar panels that could be rolled up and packaged to survive 1000.

Why not aim for the horizon? That way your track can be on the ground, and even better your impulse is spent approaching orbital speed rather than struggling against gravity drag. Even traditional space rockets turn east as quickly as possible, and a (semi) ballistic launch can do it from the start.

That said for human payloads you'd need a really long track, tens or hundreds of kilometers. I wouldn't want to live near the launch end. (edit: to get a useful amount of speed; still assuming rockets to get us the rest of the way)

Better yet - tunnel it underground.

Nah. You'd be better off building it up the side of a mountain (or mountain range). You want the air to be as thin as possible when the projectile hits it going mach 25 (or whatever, depending on where it's going).

tunnel can be environmentally controlled, which is good to reduce the possibility of combustion (argon gas). The force against the rails can be mitigated by the constraints of the earth it self at tremendous pressures. The exit can be out of the side of the mountain, its somewhat arbitrary. More importantly the tunnel/launch tube should be at/near the equator.

And yes, since the first half of the tunnel is sloping downwards you are using a large fraction of g to accelerate the slug/projectile, thus reducing the power requirements.

Its an engineering problem, not a physics problem.

Unfortunately a project of this scale is beyond the largest organizations that exist today, nation-states. Maybe later?

When the day comes for the need of a super-structure to be built in orbit, this technology will likely be used. This or a space elevator. Getting far enough away from our own gravity well will free us from this rock.

It's feasible to build a structure about 10 miles high using even conventional construction techniques. (Which would allow for orbital velocities at under 500 gravities.) Some folks at JPL have determined that aircraft building materials make 60 mile high structures possible.

I think our government should build such a launch accelerator in the desert somewhere. (Tilted at 45 degrees or so, to get a cargo drone out of the atmosphere and give it a big boost towards orbital velocity.) The ability to place bulk cargo into orbit would give the US a tremendous economic advantage. (Selling solar power satellites, colonization of Mars...)

Ten miles from a flat surface? That seems a bit ambitious to me.

You either lose energy to gravity during the launch or while in the air. Either way you lose that energy, it really doesn't matter when.

Rockets turn sideways because when you're in orbit, you're moving sideways.

You're right, but look up gravity drag. Every second you're standing on your boosters you're wasting fuel. Imagine wearing a jetpack and wasting all your fuel hovering an inch off the ground. If you turn horizontal the thrust is invested rather than spent, but first you have to build enough speed to not crash.

Actually, once you get to a high enough altitude, it doesn't take that much fuel to maintain your speed. The "Pop-up" trajectory (first stage up, 2nd stage forwards) is one that's actually practical and has been proposed for TSTO.

Well lets see:

Assuming:

Launch Speed: 17,180 mph (Speed of Space Station) [1]

Launch Acceleration: 25g (Based on my understanding of what humans can survive) EDIT [2]

Just using that as a rough estimate and Wolfram Alpha we get 242,250 meters, or about 150 miles.

http://www.wolframalpha.com/input/?i=17,239.2+mph+/25+gs

http://www.wolframalpha.com/input/?i=31.434+seconds+at+17,23...

Please feel free to check my math and yell at me.

[1] http://en.wikipedia.org/wiki/International_Space_Station

[2] cperciva [http://news.ycombinator.com/item?id=1993399] used 3g. Based on that you would have to multiply the launch distance by (25/3) and get 2,018,750 meters, about 1,250 miles. Again please correct me if I got something wrong.

It's been a long time since I've thought about rail guns, but I think you might be off in your second equation. But seeing as my other comment today is about how I may not have fully recovered mentally from a debilitating disease, I have to doubt myself.

Anyway, aren't you forgetting that most of the time is spent at a lower speed, so that you want to integrate the acceleration rather than simply multiplying by the escape velocity?

d = 1/2 at^2, where t = escape velocity / 3 G?

http://www.wolframalpha.com/input/?i=escape+velocity+%2F+3gs t = 6.3 min

http://www.wolframalpha.com/input/?i=distance+travelled+in+6... d = 2100 km (1300 miles)

While we're at it, I'm not sure what we really should be using for escape velocity. We should probably account for the deceleration after we leave the muzzle while still in the atmosphere. And if we presume a surface mounted rail gun, we'd probably want the escape velocity for a launch aimed just above the horizon, which involves more of this.[1]

Or if we're somehow presuming vertical, we'd want the escape from that height. But if vertical, we'd have to account for the extra gravitational force on the passengers, unless this is already accounted for in the human limits. In any case, I'm not sure that the speed of the Space Station (or the surface velocity I used above) really makes sense here.

[1] I vaguely recall that ignoring air resistance, the velocity is the same regardless of direction, but I don't have confidence in this, and my quick searching hasn't turned up anything definitive. Is this possibly right?

Your answer makes sense. Regarding [1] I do believe that your right, without air resistance the escape velocity is the same regardless of direction. The reason I chose the speed of ISS is because the escape velocity to enter into orbit it he speed needed to maintain that orbit. So in order to reach an orbit that parallels the ISS you would have to get up to the speed of the ISS and not necessarily any faster.

No, direction does matter. Perhaps we're confusing things by talking about escape velocity instead of orbital velocity. We want to reach a certain orbital velocity with respect to the Earth as a reference.

Think of it this way: if you were approaching Earth from space and wanted to enter orbit with the ISS, you need to reach a speed, e.g. 17,600. The speed is the same no matter where you are coming from, such as from the Earth's surface.

On the equator, if you take off east, you already have about 1,000 mph working with you. If you take off west, you need to get an extra 1,000 mph. Towards the poles, the (dis)advantage lessens.

I agree on the East vs West if we are aiming for orbital. I disagree on the speed being the same even at the surface, as (I think) you have to subtract the gravitational deceleration as you get from the surface up to the height of orbit. Coming from space you gain speed coming in, so this is not an issue.

Details aside, the overall conclusion remains that rail guns are not likely to be a useful means of propelling squishy cargo like humans into space.

Forget about launching people or anything squishy or delicate. You'd still get a lot of use out of things that could survive 1000g. That would let you launch things into orbit with an accelerator only 4 miles long. Launching refueling stations or LEO->GEO tugs would be useful. How about rolled-up thin-film solar panels?

Rail guns wouldn't be very useful for delicate things, but you could, in theory, use one to launch bulk supplies like fuel and water. The problem is the projectile comes out of the gun so fast most of the weight is going to be taken up by shielding. If you have to put up with a sucky mass factor you may as well build a rocket instead.

A ram accelerator is probably more practical in any case.

The problem is the projectile comes out of the gun so fast most of the weight is going to be taken up by shielding.

Just how long does the shielding have to withstand high temps? We already solve a much harder problem with reentry of orbital vehicles. The problem here is much simpler, as we don't actually want to shed most of the velocity. In fact, we want to lose as little of our kinetic energy as possible. If ablative shielding can handle reentry, it can handle launch. AFAIK, the mass ratio for reentry shielding is quite good.

The difference is where you start. Coming back from orbit you're going to start your run at orbital speed in no air and gradually increase air density. You'll dissipate most of your energy by the time you reach the thick air of the lower atmosphere.

The rail gun cargo is going in the opposite direction - you start in the thick air at a speed greater than orbital velocity. It's been years since I could grind through the numbers, but it makes a big difference

You'll dissipate most of your energy by the time you reach the thick air of the lower atmosphere.

This speaks to my point. In launch accelerator mode, you want to dissipate as little energy as possible. In reentry mode, you want to dump the majority of a big honking chunk of kinetic energy.

I'm sure there are all sorts of optimizations to consider. How about a mostly vertical trajectory, with most of the horizontal velocity provided by lasers heating a heat-exchanger?

By keeping the trajectory mostly vertical, one can avoid most of the lower atmosphere by stationing the opening to the atmosphere miles above the surface. This also limits the downrange danger-zone for falling malfunctioning cargo pods. Additionally, it makes the cargo pods easier to target with the lasers, since the powered flight would be entirely in the upper atmosphere. It would also make the rocket nozzles easier to design.

There appears to be potential. A quick google search turned up 'Launch to Space With an Electromagnetic Railgun' in IEEE Transactions on Magnetics. [1]

"The extension of this technology [rail guns] to the muzzle velocities ( 7500 m/s) and energies ( 10 GJ) needed for the direct launch of payloads into orbit is very challenging, but may not be impossible."

[1] http://research.lifeboat.com/ieee.em.pdf

Not much use on earth given the length of the rail required to launch at a reasonable g force but very practical on the moon where there is a lot more space and a lot less gravity (and no atmosphere to speak of).

"We're also eliminating explosives from the ship, which brings significant safety benefits and logistical benefits," Ellis said. In other words, there is less danger of an unintended explosion onboard, particularly should such a vessel come under attack.

The first half (logistics benefits) is a good statement. The rephrasing the the second half is bogus.

Joules are joules the world over. If the enemy fire hits the caps full of joules, it ain't gonna be good for the good guys even if there are no conventional explosives involved.

Joules are joules, but what you are failing to account for is the form the joules might take. If the enemy hits the caps and they explode, an amount of energy equal to one projectile launch is liberated.

If, on the other hand, you take out a magazine, you liberate an amount of energy equal to all the shots the ship is capable of taking ALL AT ONCE.

The energy necessary to fire all those shots is probably still on board, but it is likely in the form of a nuclear pile in the reactor, which is shielded up the wazoo. Even if the ship is running a conventional generator, diesel fuel doesn't have a tendency to explode in quite the same way as gunpowder.

That's true, but 33megajoules is almost exactly the amount of energy in 1L or 1/4Gal of gasoline. I don't know how much explosive a typical ship mounted canon requires for propellant and payload, but even given all the inefficiencies turning gasoline into electricity Id be quite surprised if there's quite a bit less energy on board to supply the rail gun.

200 pound of tnt is 30.2 mJ in the M107 round you have 14.6 lbs of tnt in that shell. So basically 14 shells would equal about that many mJ. I'm sure that the ship has more than 14 shells.

The mechanism of storage makes all the difference. If I store my Joules as, say, wood that has dramatically different failure mechanisms than if I store it as RDX. Even if the difference is just diesel vs. RDX. It's easier to prevent an explosion hitting diesel fuel from destroying a ship (it's been done since WWII) than it is to prevent an explosion hitting a stockpile of explosives from destroying a ship.

Even more so if the energy is coming from a fission reactor. Since the energy source is comparatively more compact and can be protected with armor more effectively.

Ok, granted, this is cool. And I see a lot of utility for space launch and other applications, so I support the research.

My question: does it actually have practical utility as a weapon of war for the modern US Navy? This seems like fighting the last war -- this is about building a weapon that goes on giant ships, when the new war is all about information and special forces strikes.

Yup. See the "Maginot line" discussion above.

When they started putting big guns on battleships, they came up with a new term: "gunboat diplomacy." When the Easter Uprising began in Ireland, the Royal Navy just sat their gunships in the bay and started shelling them from a safe distance.

So I guess they're hoping that they can bring back gunboat diplomacy in a form more suited to the 21st century. And if they're aiming for ranges of two to three hundred miles, I guess that theoretically means that no part of the UK would be entirely safe except maybe Birmingham, and that's mostly because nobody wants to go there even to blow it up.

So it leaves the gun traveling at Mach 7 and can go 100 miles but how fast is it going when it reaches the target 100 miles away? By the time it reaches the target most of it's energy is lost. The main power of this weapon is the kinetic energy it delivers to the target but that information is nowhere to be found in the article.

>So it leaves the gun traveling at Mach 7 and can go 100 miles but how fast is it going when it reaches the target 100 miles away?

The one they plan to deploy is supposed to go something like mach 20 and have a ballistic trajectory. Not something you could destroy a city with, but it'll make a bigger bang than an 8-inch shell.

Navies still get an awful lot of leverage out of the ability to destroy merchant vessels.

Wonder if a startup could get those Tomahawks down to 60,000$ a pop.

The last thing we need is new weapons.

I am sorry, I have to say this... my Quake bits won't let me rest otherwise.

"Now they just have to figure out the Quad Damage and it's going to be insta-gibs on any target!"

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