Tag Archives: energy weapons

Q&A: Gauss Rifles

So, how would a gauss sniper rifle work in real life (i.e. What kind of kick would it have, would it make a sound, what would the energy consumption be, etc)

Well, you’ve hit on the problem with all energy weapons, there. Power consumption is obscenely high. The entire reason that modern rail guns are ship mounted is because they are extremely energy intensive.

I’ll stick a caveat here that I may be doing the math incorrectly in my head, but: a handheld gauss weapon may actually have a substantially higher energy requirement per shot than a ship mounted weapon.  The energy used is based on getting the projectile to speed. With rail guns this creates two factors. First, a handheld one will have a shorter barrel, meaning it needs to accelerate the object faster, and small arms have, nominally, higher muzzle velocities than artillery meaning, in theory, you’d need to get the round to higher speeds than you’d need with a ship mounted system.

I say, “in theory,” because the muzzle velocity of the prototype rail guns the US Navy is using are somewhere in the range of 2400m/s. Which is ludicrously high speed, and gives the weapon an effective range of around 100 miles. In practice that is a bit overkill for an infantry weapon, and you could scale that back somewhat. But, you’re still left needing to accelerate an object to several times the speed of sound in a tiny fraction of a second.

I’m going to make a guess and say that recoil would be slightly more severe than with a modern gunpowder firearm. The problem is still basic physics. You’re accelerating an object into motion, which means Newton’s Third Law will take vicious revenge on your shoulder one way or the other.

What I’m not clear on is exactly how much, because of two factors. First you’re probably talking about a smaller round, and second, it will probably be going much faster than a modern firearm. A 2mm tungsten needle would have less recoil than most conventional firearms today, but muzzle energy is calculated (in part) based on the velocity and mass of the bullet when it leaves the barrel. (This is an easy point of reference for how destructive a bullet will be on impact.) In order for that 2mm spike to be more destructive than a modern bullet, it would need to be traveling significantly faster. So any recoil you saved on the lighter round would be replaced by requiring a higher muzzle velocity to do the same work.

One minor perk is that, while the projectile would have a higher velocity after exiting the barrel, it would build up speed in the barrel, meaning the recoil would be spread out a bit further. Does this matter? Maybe, but on a handheld weapon, probably not. If the overall length of the barrel is 36″ and you’re talking about a velocity of a projectile leaving it somewhere north of 1500fps, the difference between that and ignited powder would be mostly academic.

While I’m not sure what the rifle itself would sound like, I’d guess some kind of electric humming, simply because the magnetic coils would pull a lot of energy, (the prototypes sound a bit like someone shorting out a transformer), the actual gunshot would sound a lot like a modern rifle at long ranges. Again, physics is here to apply unfortunate limitations.

The speed of sound is, roughly 343m/s (or about 1125 feet per second). Any physical object that exceeds that limit will create a small air shock as it passes. (Technically, the exact point an object will create a sonic boom varies based on elevation, humidity, temperature, barometric pressure, and probably a few other factors I’m forgetting.)

Most modern rifles send rounds down range at speeds of at least 600 m/s. Even most handguns will exceed the 343m/s threshold. At long ranges, the loud crack from a rifle is a result of the bullet breaking the sound barrier. Now, if you’re operating a gauss rifle, that’s still going to happen. You’re dealing with basic physics. Firing the rifle will produce a loud crack along the path of the bullet.

Probably worth remembering the term, “rifle,” is a bit of a misnomer here. There’s no actual rifling in the gun, and bullet stabilization would probably occur via fins on the projectile itself. Probably with some kind of sabot system.

The choice of tungsten above wasn’t (completely) at random. The atmospheric friction will create a substantial muzzle flash. Where normal firearms eject burning powder, a rail gun would be ejecting flaming steel or whatever the sabot was made of. Having a projectile that can withstand the heat generated by atmospheric friction, and ferromagnetic enough to respond to the coils seriously limits the options. As mentioned above, you can’t fire a steel slug at 2400m/s because it will melt. Tungsten on the other hand has one of the highest boiling points for a metal. (It might actually be the highest, I don’t remember off hand.)

While I’m not 100% certain, it’s entirely possible the projectile may produce a visible tracer effect from atmospheric friction alone.

Now, there is another caveat here. I’m assuming you use similar velocities to a the navy’s prototypes. That’s not strictly necessary, and projecting a cartridge at, say, 800m/s would have vastly different characteristics, and may not generate enough heat to melt steel. It would also require roughly 1/3 the power per shot. However, the power consumption would still be extremely significant.

Some other details worth considering.

Because the barrel is responsible for the speed of the shot, it may be possible to fine tune how fast the resulting bullet leaves the gun. Depending on the design, this could allow for a kind of multipurpose assault/marksman rifle that isn’t really possible with modern firearms.

As I mentioned earlier, the navy’s prototypes have an effective range of 100 miles. (Or 160 km). At those ranges it would be basically impossible to fire accurately without extensive computer control, and possibly some kind of satellite aided targeting system. However, there are a couple reasons to tune one that high.

First, drop and drift. Bullets are, as we’ve said before, physical objects. There’s an old physics experiment where, if you fire a gun (parallel to a flat surface) and drop an identical bullet simultaneously, both will hit the ground at the same time. Depending on the cartridge, this does become a factor sooner or later. Spitting a round out at Mach 7 will have very limited drop in the first mile or two, meaning it will be somewhat easier to predict where the round will land at those ranges. This isn’t fully necessary, but it helps.

The second thing is transonic speeds. As a bullet travels through the air, it loses speed. When it gets down close to 343m/s, it will drop through transonic speeds. When that happens, it will be overtaken and hit by its own sonic boom. This destabilizes the bullet’s flight, and effectively destroys accuracy beyond that distance. The initial speed determines when that happens, and by extension, how far you can fire the weapon. If you can radically increase the initial speed of a bullet, you extend the effective range. This is part of why that prototype is so impressive.

Incidentally, if you get the velocity over, about 11.7k/s (so a little over four and a half times what the prototypes fire), you can put a round into orbit. Not particularly relevant for the question, but worth knowing. (Also that’s Earth’s escape velocity. It wouldn’t be the same for other planets. For example: those same railguns can achieve lunar escape velocity now.)

Of course, the biggest issue with these is still power consumption. Regardless of the factors, you’re still using electromagnets to propel a slug of metal to hypersonic speeds. With modern energy technology, that’s not really feasible.

-Starke

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Q&A: Basic Energy Weapons

If Sci-Fi laser guns existed, do you think the bolts would act more like bullets or laser pointers in relation to how the various variables affect their path?

The thing about lasers is, they actually exist now. Which wasn’t true (or, at least, wasn’t as true) back when science fiction first picked them up as a concept.

A laser is, basically by definition, going to travel at, or very close to C. (Roughly 300 million meters per second.) So, if you’re thinking of slow moving projectiles that your eye can see and track, that’s never going to happen.

The other thing about lasers is, they’re just focused light. This is the same, basic concept as a kid with a magnifying glass, weaponized. It’s still going to reflect off, or burn through, anything it hits. It will also be basically invisible.

The only time you can actually see a laser beam, in real life, is if there’s particulate matter in the air, reflecting the light back to you. Smoke, fog, and dust will all pick up the beam, and reflect some back to you so you can see it. This isn’t a problem when you’re talking about a targeter or pointer; the beam isn’t particularly destructive, so this kind of blowback is harmless. But, when you’re talking about a weaponized laser, that starts to become a real concern.

This is a general truth about seeing things, by the way. For your eye to see something, light needs to strike it and bounce off, hitting your eye. Your eye processes that light, and tells your brain, “hey, there’s a thing here.” Lasers, by definition, avoid that until contact with their target. Thing is with a weaponized laser, the produced light is the weapon. So, if you can see it, you’re getting hit. Even if it’s bouncing off water vapor in the air.

Of course, as with any other variety of light, you can bounce it off a reflective surface. This means, the greatest defense against future soldiers with laser weapons may just be polished chrome surfaces. Not only would it reflect the laser off of it, it would send it back in the general direction of the original user or their buddies. Best of all, you couldn’t see exactly where it was going, because you don’t want that light being reflected back to you.

Now, there is a possibility it would burn through any dust or other atmospheric contaminants on the way through, leaving a faint, singed, after image of where the laser was fired, but in general, you wouldn’t be able to see the beam. Which isn’t that different from bullets, for that matter. There’s another possibility where it would reflect off something like water vapor or any other atmospheric obstruction, (the way lasers actually do), and diffuse to the point of worthlessness almost immediately. (To be fair, I’m not sure which is more likely to occur.) Either way, you’ve got a weapon that will face all kinds of problems on a battlefield.

If you’re trying for a hard-sci-fi setting, (meaning the science underpinning your setting is sound), then all of these factors will make lasers less appealing. If your setting is aimed at a less grounded, soft sci-fi, then lasers are (somewhat) less appealing, simply because their fantastical value has worn off. Lasers sounded like weapons of the future, when you couldn’t pick one up as a cat toy for $5 in most department stores.

With that in mind, you can try to keep the same weapon concept, but selectively trim off the issues, for your softer settings. Things like Star Trek’s phasers and disruptors aren’t, technically lasers, while Star Wars’s Blasters are an entirely different technology that you probably interact with in a non-weaponized capacity on a regular basis.

As with a large amount of stuff in Star Trek, whatever technology keeps phasers from reflecting around randomly is never clearly explained. The term itself is a portmanteau of phased and laser. So, it’s some kind of laser variant that won’t normally reflect (though it is shown happening a couple times in the franchise).

Disruptors are even more nebulous, and it’s helpful to remember this is more of a catch all term, including things like sonic weapons, up through a variety of molecular disruption weapons.

Star Wars uses the molecular disruption idea for their disruptors, when the writers want one, but basic blasters aren’t laser weapons. Blasters fire bolts of ionized gas, meaning they’re actually plasma weapons.

As with lasers, plasma is a concept we’re familiar with in modern day. In the simplest terms, it’s a fourth state of matter. You have solids, liquids, and gasses, with plasma sitting above gasses. Plasma is heavily affected by magnetic fields, meaning it is possible to contain and eject it with directed energy weapons (though, that’s not possible with current technology.) It’s not a very energy efficient technology, but you don’t need to worry about it reflecting back and killing the shooter because it struck a mote of dust en route to the target.

If you absolutely need an energy weapon that behaves more like a modern gun, firing glowing bolts of energy, plasma is probably your best bet.

There are problems. Magnetic fields on the target’s armor could mess with the plasma delivery, (which may help you understand that line about the Death Star’s trash compactor being magnetically shielded.) Also, any magnetic field it passes through on the way.

Plasma is also an option for beam weapons. In fact, the most destructive form of plasma you’ve probably encountered is a lightning strike. The electrostatic discharge instantly ionizes the atmosphere between the points, and you get a visible flash of light, followed by the sonic shock of that air being instantly converted into plasma.

Before I move on, it’s probably worth noting, most current plasma research is focused on power generation. That is to say, using magnetic fields to contain plasma for the purposes of safe fusion reactions.

Long term, plasma weapons are probably going to fall by the wayside for sci-fi the way lasers have. Most people don’t think of fluorescent lights as plasma, so the term sounds more fantastic than the technology really is. With refinement of magnetic containment technology, and the use of fusion as a power source, plasma weapons will probably lose a lot of their shine.

The railgun is another weapon you’ll see referenced in near-future sci-fi. Sometimes called gauss weapons, or mass drivers, these are, quite simply, a gun. Instead of using a chemical propellant, they use magnetic fields to accelerate a ferrous slug to speed.

I’m bringing them up for two reasons. First, it is one conceivable way to make a plasma weapon viable. Second, they actually exist.

Laser weapons are, at best, theoretical. Plasma containment and manipulation is an actively researched topic. Though the primary goal there is power generation, not weapons technology. Railguns do exist today.

Modern railguns are mounted weapons. You can stick these things on a naval vessel, or in a facility. They draw massive amounts of power to fire, but deliver a lot of destructive force on impact. Part of the reason is because they’re truly frictionless. You can accelerate their payload to speeds that would utterly destroy conventional firearms. You can also send payloads down range that are far harder than anything you’d ever load into a gun.

One of the mechanical limitations to modern firearms is, the bullet and barrel are in direct contact. When you fire a bullet, it, quite literally, scrapes the barrel on its way out. Part of the reason why we make bullets out of materials like lead and copper is because they are substantially softer than the steel barrel, and will result in significantly less wear.

When we do need to fire a round with something more solid as its payload, the harder core will be wrapped (called jacketed) by a softer metal. For example, a steel core round will have a copper or lead jacket, to protect the firearm. On impact, that coating will strip away fully, and the steel will (usually) punch through any light armor in its path. You’ll also see things like depleted uranium, or tungsten used as cores for armor piercing rounds.

With railguns, that’s not a consideration. Unless the material is magnetically inert, you can just drop it in, and fire it.

What we can’t do with a rail gun, is carry it around. Current technology is too energy intensive for that. But, if you’re looking at a future setting, where power generation is less of a consideration, then these may be an option. Ballistically speaking, they are guns, firing solid projectiles. The only difference is, they’re doing so at speeds that are impossible to achieve with conventional firearms.

I’m going through all of these, but all of them are built around the idea that we need something other than conventional firearms. That’s probably true, on a long enough timescale, but modern ballistic weapons are remarkably energy efficient, for their design. You have a cartridge which contains all of the necessary energy to propel a round at hyper sonic speeds. There are considerations like recoil, which can be minimized through mechanical developments. There’s also potential hybridization of other technologies into them, in order to make a more efficient design. But, if you’re working with a sci-fi setting, it’s worth considering that guns may stick around, simply because they work.

In a vacuum, lasers or plasma weapons are probably more desirable, because a mass projectile will continue traveling until it hits something, which could be in hundreds of thousands of years. But, a laser will eventually disperse to the point that it is too indistinct to cause damage.

In an atmosphere, a gun, or gauss rifle may be a much better option for the situation presented.

-Starke

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