Could magnets substitute gunpowder in guns?

[angushall19]

I was wondering if electromagnets could substitute gunpower. If you could have multiple with a charge on one spot, could a bullet be propelled forwards with the same effects. Possibly working like a tiny rail gun.

Edited November 23, 2015 by angushall19

[Greg H.]

In theory, yes. In practicality, no, though it's strictly an engineering problem in terms of how much power you need and the size of the capacitor banks, etc it takes to construct it.

 

Although in that case, you really don't need a bullet. A nail or an iron ball would also work acceptably well.

Edited November 23, 2015 by Greg H.

[Phi for All]

Although in that case, you really don't need a bullet. A nail or an iron ball would also work acceptably well.

 

Much, much better than a Pb bullet would.

[MigL]

Small guns would be impractical.

Large guns, for anti-aircraft or anti-satellite, are being tested and evaluated.

Look up railgun or coilgun.

[TheGeckomancer]

Well really the problem comes down to energy densities. Every bullet you fire carries it's own fuel to propel it. You would be replacing all of the gunpowder that is used to accelerate that bullet with stored electricity that would be used to run the magnetic rail. The problem is that the best batteries in the world have nowhere near the energies densities of any solid chemical we use for propellant. In larger scale this problem really becomes irrelevant because you could hook up a static one straight to a hydro electric dam and fire scrap for nearly eternity without running out of ammo. On larger scale it becomes way cheaper because even though the raw energy required to power the weapon is greater, you remove all cost from ammo and manufacturing complexity.

[swansont]

Well really the problem comes down to energy densities. Every bullet you fire carries it's own fuel to propel it. You would be replacing all of the gunpowder that is used to accelerate that bullet with stored electricity that would be used to run the magnetic rail. The problem is that the best batteries in the world have nowhere near the energies densities of any solid chemical we use for propellant. In larger scale this problem really becomes irrelevant because you could hook up a static one straight to a hydro electric dam and fire scrap for nearly eternity without running out of ammo. On larger scale it becomes way cheaper because even though the raw energy required to power the weapon is greater, you remove all cost from ammo and manufacturing complexity.

 

Not so much — why batteries? The energy density of gunpowder is about 3 MJ/kg, while for gasoline it's 44.4 MJ/kg (diesel and propane, etc. are similar). So even acknowledging inefficiencies in converting fuel into electricity and electricity into propulsion of a projectile, you have a factor of 10 head start if you use a generator or fuel cell.

 

And as you point out, scaling is in your favor, too — put this on a nuclear powered vessel, and your capacity to efficiently generate the electricity (in terms of energy density) goes up by many orders of magnitude. Without the danger of storing all that gunpowder.

 

Further, I expect that for larger projectiles, the ability to impart momentum from a railgun over the length of the barrel rather than expanding gases (pressure decreases as the projectile moves down the barrel) may make for higher muzzle speeds and thus greater ranges.

[TheGeckomancer]

For batteries, I was mainly referring to handguns and whatnot. You would not want to carry a diesel generator on your back to use a rifle. I honestly don't know much about the energy density or capacity of fuel cells.

[OldChemE]

I realize this is an old post-- but gunpowder and firearms design is a topic close to my heart so I thought I would add some ideas.

 

Certainly, a magnetic or other energy source approach to a firearm is within the reach of current technology. This prompts me to toss out some suggestions for the specifications such an alternate approach might want to meet. At a very early point in history firearms were revolutionary-- but since then the development of firearms has been evolutionary-- and there are lots of unique aspects that a new design might want to consider.

 

The energy source: Certainly, any energy source that cam impart sufficient velocity and momentum will do. Gunpowder is particularly well suited to this task. It is easily packaged in the cartridge which means no external power source has to be maintained. It lasts very long times without degradation (100year old ammunition usually works just fine). This gives it a degree of superiority over liquid fuels and external power sources.

 

The projectile: accuracy over a great distance usually requires stable flight and a minimum of velocity loss with distance. This prompts us to want low drag and high mass. Low drag to minimize energy losses and high mass to provide higher energy and momentum. Lead projectiles, although originally convenient because one could make their own musket balls over a fire, work particularly well (regardless of whether or not they are covered by a metal jacket) because lead is a very dense material-- allowing lots of mass in a small package with a small drag cross-section. Your design needs to think about the projectile, how far you want it to go and how much energy you want it to retain over that distance.

 

The launching mechanism: Unless your projectile can be controlled during flight, you need to give it not only linear momentum but also angular momentum about the axis of the direction of travel (spin). This is another reason lead has worked out so well-- it engraves to the rifling, which imparts spin, yet it (and copper jackets) are soft enough that they cause minimal wear to the barrel. And-- a rifled barrel is really a very simple means of imparting spin to a projectile. your design needs to consider how you will obtain stability in flight and how to do so in a way that will be reliable for extended use.

 

Energy impulse: The time duration and peak of the energy impulse has a lot to do with the requisite strength of the launching mechanism. This actually makes something like a rail gun look pretty good, because the acceleration force can me modulated and maintained right up until the projectile leaves the mechanism. This is, in fact, how gunpowder systems work. There are currently about 150 different formulations of gun powder commercially available that have purposely designed burning rates ranging from very fast (essentially an explosion) to very slow (more like solid fueled rockets). This permits each cartridge to be designed such that the gunpowder burn will last until the projectile leaves the barrel and also allows the peak pressure of the burn to be matched to the capabilities of the firearm design.

 

Flexibility and ease of use: This relates to the hobby of reloading. Many people (myself included) reload our own ammunition because it allows us to customize the ballistics of our firearm for whatever purpose or interest we wish. We can tailor our charges for any velocity from barely enough to leave the barrel all the way to supersonic flight (within the pressure capability of the firearm). We can vary the composition, mass and shape of our projectile to suit our interests. Some of us (particularly old engineers) can waste thousands of rounds of ammunition doing nothing be experiment with the variables. The equipment needed is simple and inexpensive. This is why reloading is such a popular hobby even though factory made ammunition is readily available-- the factory loads are very standardized and not customized to a particular firearm and its mechanical tolerances. So-- if you want to design a good replacement for gunpowder firearms, think about whether or not you design will be within the reach of people to tinker and play with.

 

(for those wondering what I do with all this-- I plan to someday have a perfect set of custom loads for each of my 5 rifles-- just for target shooting, since I am not a hunter. So far I've only built and fired about 18,000 rounds, but I still have so very many experiments I still want to try).

[Bender]

A rail gun has other things to tinker with, such as the optimal signal to send to the coils for different bullets/applications. The tinkering becomes electronic rather than chemical.

 

About the weight: iron isn't much lighter than lead. Undoubtedly, people could come up with e.g. steel-tungsten alloys if necessary. Besides, when the bullet doesn't need a gunpowder container, it automatically has higher bullet weight/stored weight and bullet weight/stored volume ratios.

edit: the US military beat me to it with tungsten armor-piercing bullets.

[OldChemE]

Very true, but I enjoy playing with the chemical side (probably not surprising for a Chemical Engineer).

[RiceAWay]

 

Not so much — why batteries? The energy density of gunpowder is about 3 MJ/kg, while for gasoline it's 44.4 MJ/kg (diesel and propane, etc. are similar). So even acknowledging inefficiencies in converting fuel into electricity and electricity into propulsion of a projectile, you have a factor of 10 head start if you use a generator or fuel cell.

 

And as you point out, scaling is in your favor, too — put this on a nuclear powered vessel, and your capacity to efficiently generate the electricity (in terms of energy density) goes up by many orders of magnitude. Without the danger of storing all that gunpowder.

 

Further, I expect that for larger projectiles, the ability to impart momentum from a railgun over the length of the barrel rather than expanding gases (pressure decreases as the projectile moves down the barrel) may make for higher muzzle speeds and thus greater ranges.

I hope you realize that what you are suggesting is that natural gas would be a lot easier to carry and could propel a bullet with a great deal less fuel that gunpowder? Far better to use the fuel itself than go through a couple of energy conversions.

[swansont]

I hope you realize that what you are suggesting is that natural gas would be a lot easier to carry and could propel a bullet with a great deal less fuel that gunpowder? Far better to use the fuel itself than go through a couple of energy conversions.

Let's see the math.

[RiceAWay]

Let's see the math.

Isn't that like saying "design it for me"? My ideas are my own.

[swansont]

Isn't that like saying "design it for me"? My ideas are my own.

You're making an assertion based on something I didn't actually say (I never said anything about natural gas, and I was talking about a rail gun projectile). I'd like to know if your assertion has merit. Can you back it up, or was it baseless?

[RiceAWay]

I realize this is an old post-- but gunpowder and firearms design is a topic close to my heart so I thought I would add some ideas.

 

Certainly, a magnetic or other energy source approach to a firearm is within the reach of current technology. This prompts me to toss out some suggestions for the specifications such an alternate approach might want to meet. At a very early point in history firearms were revolutionary-- but since then the development of firearms has been evolutionary-- and there are lots of unique aspects that a new design might want to consider.

 

The energy source: Certainly, any energy source that cam impart sufficient velocity and momentum will do. Gunpowder is particularly well suited to this task. It is easily packaged in the cartridge which means no external power source has to be maintained. It lasts very long times without degradation (100year old ammunition usually works just fine). This gives it a degree of superiority over liquid fuels and external power sources.

 

The projectile: accuracy over a great distance usually requires stable flight and a minimum of velocity loss with distance. This prompts us to want low drag and high mass. Low drag to minimize energy losses and high mass to provide higher energy and momentum. Lead projectiles, although originally convenient because one could make their own musket balls over a fire, work particularly well (regardless of whether or not they are covered by a metal jacket) because lead is a very dense material-- allowing lots of mass in a small package with a small drag cross-section. Your design needs to think about the projectile, how far you want it to go and how much energy you want it to retain over that distance.

 

The launching mechanism: Unless your projectile can be controlled during flight, you need to give it not only linear momentum but also angular momentum about the axis of the direction of travel (spin). This is another reason lead has worked out so well-- it engraves to the rifling, which imparts spin, yet it (and copper jackets) are soft enough that they cause minimal wear to the barrel. And-- a rifled barrel is really a very simple means of imparting spin to a projectile. your design needs to consider how you will obtain stability in flight and how to do so in a way that will be reliable for extended use.

 

Energy impulse: The time duration and peak of the energy impulse has a lot to do with the requisite strength of the launching mechanism. This actually makes something like a rail gun look pretty good, because the acceleration force can me modulated and maintained right up until the projectile leaves the mechanism. This is, in fact, how gunpowder systems work. There are currently about 150 different formulations of gun powder commercially available that have purposely designed burning rates ranging from very fast (essentially an explosion) to very slow (more like solid fueled rockets). This permits each cartridge to be designed such that the gunpowder burn will last until the projectile leaves the barrel and also allows the peak pressure of the burn to be matched to the capabilities of the firearm design.

 

Flexibility and ease of use: This relates to the hobby of reloading. Many people (myself included) reload our own ammunition because it allows us to customize the ballistics of our firearm for whatever purpose or interest we wish. We can tailor our charges for any velocity from barely enough to leave the barrel all the way to supersonic flight (within the pressure capability of the firearm). We can vary the composition, mass and shape of our projectile to suit our interests. Some of us (particularly old engineers) can waste thousands of rounds of ammunition doing nothing be experiment with the variables. The equipment needed is simple and inexpensive. This is why reloading is such a popular hobby even though factory made ammunition is readily available-- the factory loads are very standardized and not customized to a particular firearm and its mechanical tolerances. So-- if you want to design a good replacement for gunpowder firearms, think about whether or not you design will be within the reach of people to tinker and play with.

 

(for those wondering what I do with all this-- I plan to someday have a perfect set of custom loads for each of my 5 rifles-- just for target shooting, since I am not a hunter. So far I've only built and fired about 18,000 rounds, but I still have so very many experiments I still want to try).

Interesting note: the rifling imparted to the bullet actually decreases the aerodynamic drag if the bullet. The reason that gunpowder works better than other fuel sources is the speed of the flame front - just below the speed of sound. Otherwise it would explode the barrel. So while the AVAILABLE energy of other fuel sources is much higher, the practical use of it is much worse than gunpowder.

 

As you mention, a bullet also requires a very high density so steel and such things work very poorly beside wearing the barrel out in very short order.