Practical Manportable Railguns

[JJohnston015]

The weapon could be designed with multiple mags with different ammo (both shape and mass). Between on-the-fly ammo selection and variable acceleration you could precisely tailor the round delivered for each and every shot.

Make it voice-activated, and you'd be Judge Dredd!

"Double Whammy."

Not that I actually watched that.

 

[QKRTHNU]

For those of you that envision a world where OPEC is relegated to the same international significance as Bolivia's bauxite mining by the development of fuel cells you may be forgetting that fuel cells operate on hydrogen (some very few on natural gas) and that hydrogen is evolved by use of electricty and electricty comes from oil fired, coal fired, gas fired, hydroelectric, wind, solar electric generating facilities (in that order). Without conservation, alternative/renewable fuels, nuclear power, etc. we will continue to be in the thrall of the oil producing countries.

There are already some pretty cool ways of gathering Hydrogen for fuel cells. Check this out.

http://www.fuelcells.org/fcfaqs.htm#hydro

Enzymes - Another method to generate hydrogen is with bacteria and algae. The cyanobacteria, an abundant single-celled organism, produces hydrogen through its normal metabolic function,. Cyanobacteria can grow in the air or water, and contain enzymes that absorb sunlight for energy and split the molecules of water, thus producing hydrogen. Since cyanobacteria take water and synthesize it to hydrogen, the waste emitted is more water, which becomes food for the next metabolism.

Solar- and Wind- powered generation - By harnessing the renewable energy of the sun and wind, researchers are able to generate hydrogen by using power from photovoltaics (PVs), solar cells, or wind turbines to electrolyze water into hydrogen and oxygen. In this manner, hydrogen becomes an energy carrier – able to transport the power from the generation site to another location for use in a fuel cell. This would be a truly zero-emissions way of producing hydrogen for a fuel cell.

 

[M67]

This isn't new. I have seen a reference to (but not read) an article in Scientific American from the 1840s about shoulder fired coil guns, and I don't think the idea was new then either.

I do see large style weapons being introduced relatively soon, like ship-board systems, and large, mobile type set-ups, where power generation and size don't matter so much.

Not new either. A Norwegian scientist filed some patents regarding large coil guns around the turn of the last century, I think 1901 or '02. His tests in his lab at the University of Oslo involved a 20 kg iron projectile fired into a wooden "bullet trap". I don't remember velocities, but he did say that he could have gotten more velocity if only he could have drawn more power from the city's main grid. In a later experiment he overloaded the main circuit board at a hydro electric power plant, and caused a fire. The plan was to build field and coastal batteries. For anti-shipping use he envisioned "torpedoes", huge iron shells with a payload of 500 kg of nitro glycerin... The guns were supposed to be powered by mobile generators with "huge flywheels". The main problem was to switch the coils on and off at the right time, this was before computer control, photoelectric switches and such. I think the plans for full-scale guns involved hundreds if not thousands of individual coils. If the coils were not switched on/off at the right time, the result was huge sparks and lots of noise. And a further digression: Even if the electro-magnetic artillery project never came to much, this way of making huge electric sparks lead directly to a new method for producing nitrogen-based fertilizer. For those interested in WWII history, one of the byproducts of this manufacturing process is heavy water.

During WWII there were German plans to build electromagnetic guns for shooting from Belgium to targets in Britain. I don't remember where I read about this, but it included drawings of huge contraptions that looked like something out of Jules Verne.

 

[MrAcheson]

A railgun projectile is accelerated by a lot of force on a small area for a relatively long length. To defend against it you need to be able to produce a lot more force in a much shorter distance on a much larger potential area. A shorter distance because a vest needs to stop the projectile in 2" instead of the 20" it was accelerated in. A larger area because the cross sectional area of a gun barrel is much smaller than to the cross sectional area of your whole chest. A lot more force because you have to overcome the distance and area problems with force.

Now you may be able to get around the area problem by using a good control system, but you cannot get around the length and force problem easily. As such defense will lag behind offense, if they are using the same physical principles. Besides who says the railgun nail needs to be conductive, what if the nail's ballistic sabot is conductive but the nail is not? If the nail is essentially inert (ceramic/polymer penetrator for instance) then no field is going to stop it because those physics don't apply anymore.

Also, carbon nanotubes are really really brittle and fragile. Makes them stink at impact absorption because they break down with multiple impacts. Your backplate would be trashed after the first impact. This is why some polymer framed guns have had problems with cracking.

Seriously though, railgun research has been dropped in many areas. Power supplies are ridiculously large (like a the size of a building) and the guns themselves are as heavy as conventional guns because of the spreading forces created by the e-fields used to propel the nail. Plus conservation of momentum means you don't get a free lunch on recoil either, gun pushes projectile and projectile pushes gun.

 

[PaladinX13]

There's no reason to power up the entire chest as you presume, just as active armor doesn't explode the entire surface of tank. Besides, that's just one means of doing it, another would be to have literal active armor... a plate of armor that, upon detection of incoming projectile, moves out a couple inches to meet it, this can handle whatever a bullet may be made of and solves the distance/force issues... essentially turns bullets into bean bags.

Don't limit your imagination. The point is that whether defense lags behind or not, a railgun isn't a magic sword. At any point that something becomes magic-sword like, the defensive side closes the gap. You can list all these advantages that a railgun has over present day technologies... but don't ignore the advantages that would go to defense along the way.

Brittle Carbon Nanotubes that's an old and incorrect misconception tackled in an old TFL thread. Perfect carbon nanotubes are nothing like fiberglass-type polymers and can be very elastic.

 

[TexasVet]

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Another advantage is the lack of sound; while the power source might make some noise (perhaps a hum or something), a coil gun would not rely on chemical combustion; in other words, the actual firing wouldn't make any noise.
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Actually, since the projectile is usually exceeding the speed of sound while still in the barrel, the experimental military railguns are EXTREMELY loud.

 

[MrAcheson]

Sorry Paladin, but I'm also a ex-composites engineer. I have handled carbon nanotubes, they're brittle like graphite at the macroscale. I also have been to conferences where their proporties (which are entirely theoretical for nanotubes longer than a millimeter or so) have been discussed. Carbon nanotubes are like every other nanotech wonder technology, full of promise but almost worthless for the foreseeable future until manufacturing in a usable form becomes possible.

Secondly, do not assume that defense will automatically close the gap with offense. For essentially two hundred years no one bothered to wear body armor to protect against bullets. Why? Because the armor would have been so heavy as to be utterly impractical. Offense in this area badly outstripped defense and people focused on mobility instead. It was only the advent of manmade fibers that allowed defense to catch up.

The point is that because of basic laws of physics anbd natural human tendencies, a soldiers defensive gear almost always lags behind his offensive gear. Railguns are not magic swords, but defensive garments are even less likely to be magic shields.

 

[Nightcrawler]

Actually, since the projectile is usually exceeding the speed of sound while still in the barrel, the experimental military railguns are EXTREMELY loud.

Well yes, but that's why you adjust your muzzle velocity down to subsonic speeds. That's why it's so versatile.

 

[Nightcrawler]

Many gauss rifle ideas I see on the internet (mostly on role playing game sites) involve a 4x20mm flechette. That's kind of on the small side.

What would you prefer? Tiny and super fast or bigger and not quite so fast?

Gauss rifles would have the disadvantage of requiring a power supply. They would have the advantage of having almost no moving parts and a perfectly clean method of operation; they wouldn't foul, even after thousands of rounds of firing, and parts breakage would be much less.

A recoil reduction/absorbtion device might be warranted, adding complexity, but nothing unworkable.

 

[TexasVet]

yes, but...

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Well yes, but that's why you adjust your muzzle velocity down to subsonic speeds. That's why it's so versatile.
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But then your cost/benefit ratio gets stacked WAY in favor of conventional arms. Silencers are very cheap to make.