Magnetic Gun


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Suppose you have a ten meter barrel which is inside 1000 super conducting electromagnets that is used to acceralate a steel ball of 1 gram, what the is maximum veolocity that can be achieved? Assume any parameters not given such as the frequency of the linear motor, diameter of the barrel, flux density etc.

Can such devices be used to propel small payloads to space?
Insufficient information ...

Vented (skeletal) or solid barrel?

If solid, normal atmospheric pressure or vacuum?

Impulse duration?

Flux density?

If assumptions optimal: yes (if fired from the top of a mountain - at least 12,000 feet)
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Hi Kmguru,

You would need to know the strength of the magnetic fields (in Tesla = knowing exact currents going through superconducting material, temperature of superconducting material and ofcourse the kind of superconducting material), the kind of "steel" used (in what amount is it ferromagnetic). You would need to know the airfriction ( = knowing air density, exact shape of ball), friction of the object holding the ball before the magnet is switched on.

Once you know all that, you need to calculate the magnetic field that is induced in the steel ball to find out in what way it will be propelled by the superconducting magnets. The formula:

F = q*(E + v x B)

no longer works here because a macroscopic object has q = 0 on the average.

Not really an evident calculation.


Darn you Crisp ...

Always have to be so logical ...

Couldn't you at least have agreed with me?

All I could imagine when I wrote that post was kmguru hauling the necessary equipment up to the top of some mountain.

Party poop!
There has been some speculation on the use of magenetic rail guns used for launch. However, I'm really not based enough to say this is what it takes. I can tell you thoughts on it. Most picture something on the order of a tube, laid against a mountain side (for scope of size) to get the elevations right. A lot of rows of superconduting magnets each set at the right distance to pick up where the other left off. One of the questions in the back of my mind is how much velocity would that provide and exactly what parameters would be needed to allow for the human cargo not to be squished against the back bulk head?
Vulcan logic can come in handy some times

Hi all,

Chagur: Now you mention it, that *would* have been a great sight, wouldn't it ;).

But I'll agree with you. With big enough magnets and strong enough fields, I think you'd be able to speed something up to escape velocity. To minimize airfriction, it would indeed be a good idea to go on top of a mountain (airfriction tends to slow things down fast).

Wet1: Yes, I've read something in those lines at various Space news sites. I guess that if they seriously considered building a magnetic gun, that it would provide enough speed for an object to enter an earth orbit. I also suppose that the acceleration would increase after the gun is switched on (making sure the "craft" - or should we say, cannonball - gradually leaves before it attains the required speeds). It's a good idea to prevent the human cargo from having their heads banged against the back wall (and I try hard not to mention the words "brains" and "splatter" in that sentence ;)).


Hi kmguru,

"Supercavitation principles", could you elaborate a bit further on this ?


I guess ...

What kmguru is referring to is creating a 'vacuum bubble', something he's no doubt worked on at one time or another, and using it in the same way the Russians have used a rocket created bubble about their torpedos to attain extremely high underwater speeds. Like two to three hundred kph with their Squale torpedo and latest improvements (which may have been responsible for the loss of the Kursk).

Damn, I hope I wasn't a party poop, Crisp.
Hi Crisp:

Chagur is right on the low pressure bubble. I do not know if it will work, it was just a speculation. You are the expert. You will tell us why it wont work, right?

Chagur is wrong in that I have not worked on aerodynamic engineering. :(

Here is a link to Supercavitation in US military if anyone is interested.

Hi Chagur:
Mentioning personal experience in one thing or another helps me not to quote too many references where I have first hand knowledge. If that causes some problems for you, I apologize.
Hey, kmguru ...

Thanks for the link. Although I check the ONR every so often, I hadn't seen it. Either it's relatively new, or I just missed it. The best part is at the end:
Expected funding available for this area in fiscal year 2002 is in the range of $1,900K to $2,700K
I'd say they're out of the closet about that research now that there's been so much written about it. Don't have to keep it a 'black' project any longer.

The other thing is; no need to apologize. I fall back on personal experience quite often as you may have noticed. You're fortunate to have had such a wide range of experience. Few people have.

Take care
Perhaps not vacuum, but a gas thinner than air will do.

Hi Kmguru, Chagur,

What kmguru is referring to is creating a 'vacuum bubble', something he's no doubt worked on at one time or another, and using it in the same way the Russians have used a rocket created bubble about their torpedos to attain extremely high underwater speeds. Like two to three hundred kph with their Squale torpedo and latest improvements (which may have been responsible for the loss of the Kursk).

The ONR link Kmguru supplied doesn't seem to talk about a "vacuum" being created in front of the torpedo to reduce drag. And because of the high tendency of fluids and gas to immediatelly fill vacuums, I personally think air or some kind of gas is exhausted in front of the torpedo (I could be wrong on this one though, even though it would be interesting to know how they maintain that vacuum for a descent enough time for the torpedo to propel into).

However, a similar mechanism could be used for the magnet gun yes, if the object to be fired would replace regular air by a less dense gas such as... Helium, less friction is introduced in front of the object. (I'm only using Helium as an example because I basically just got up and my celebral capacity has not yet attained high enough levels to think of something thinner than helium ;) - experimentation would probably rule out which gasses are better not used). This method would only be usefull for not too high altitudes; once you're high enough, the air probably becomes thinner than the gas you're propelling into, so some sort of "altitude" / air density measurement device would be required.


You are the expert. You will tell us why it wont work, right?

Hehe, good one :). The best I can do is give you my point of view. In the very few experience I've gained in the last couple of years, I've only realized that I've made some very stupid/physically incorrect statements on this forum ;) in the past, so it would be quite unfair to the real experts to call me one.


Now that we solved the problem, should we start working on a prototype? Crisp, are you interested on this project? If so , send me a PM.
Hey Crisp ...

Sorry for the missunderstanding ...
and using it in the same way the Russians have used a rocket created bubble about their torpedos
Should have been clearer re. the bubble, not a vacuum, being created by the rocket.

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great ideal, but ....

Well if you can use magnetic force to power a gun then you could most likely power a motor using magnetic or eletromagnetic force. If I am correct the typical motor is powered by electromanetisim.
A motor needs a battery because of the electromanet, but is you introduce a normal magnet
in the proper place of a magnetic motor it should run with out a battery by using the magnets force.
I am sure that you could desighn a motor that could completely rely on a manetive force, this would not need any power supply. While I am on this subject you could use physics to power any motor or enginne. A force can not be created nor destroyed so with that in mind you could recycle a force into a continuise power supply for example...A motor greats kinetic and heat energy so if we can convert the heat an kentic energy back into eletrical energy and use that energy to power the motor this process will continue forever if a am not mistaken.

You will break the law of conservation of mass/energy and get a ticket from God....
Close, but there's this annoying thing called thermodynamics...

Hi Jimmy James,

Very nice in theory, but you forgot to include friction in your calculations. This will eventually slow down the engine/motor because energy is lost in collisions with air molecules, other parts in the engine, ...


Thanx for the chuckle on your post to, JimmyJames.

One of the contenders for cheap methods to space has been the beanstalk. The big holdback had been the lack of material with sufficient strength to hold it together.

The magnetic railgun is another. I would believe that even with the problems that are discussed here that we are much closer to the reality of the railgun than to the beanstalk.
I am glad you enjoyed it O wet1. Actually I was not thinking about the magnetic gun to put payloads in the orbit. I know that is doable. What I was wondering is if we can use the same technology with added supercavitation to propel small depleted uranium based (super heavy) projectiles (the size of a 30mm round) to destroy ICBMs?

not a one round but like a shotgun that will fan out and cover a wide area...The pwer supply will be the capacitor banks to provide high Tesla magnetic power. Presently the problem is, too high Tesla destroys the coil, but with right configuration it may be doable.

Just wondering....

BTW, somewhere I read, if we can build a winch system using carbon fiber nanotubes, we can put payloads up like the beanstalk....
The monkey wrench

In use for ballistic purposes, you run into the problem of barrel length for accuracy and distance. With a background in artillery, I can also say the weather conditions play an important part in the arrivial of projecticle to target. Given the distances where weather is a factor in two different locations adds to the problem, if your thinking of entry/rentry. Among other conditions considered are air density, wind direction, and temperature. How close a "pattern" the shot gun approach gives is related to these factors also. (food for thought)