Science: Space: Launch
Explosively Compressed Coil Gun   (+1, -1)  [vote for, against]
A space cannon, powered by EMP.

In this paper a new method of speeding a projectile to orbital velocities is introduced. This method is based on utilizing the power of an Explosively Pumped Flux Compression Generator. Due to great magnetic fields generated by the EPFCG, thrusts in the order of 1 x 108 N can be produced using its direct application on a target. The projectile in ECCG has a circuit that is also be powered by the EPFCG through induction. Sample calculations showed that a 6.1 kg projectile could be accelerated to 14.3 km/s within 0.001 seconds and a length of 4.67 m, well enough to launch it into space.
-- xkuntay, Aug 29 2013

Explosive magnetic generators for feeding rail-gun launchers for solid projectiles http://labs.adsabs....1986FizGV..22...76A
Unfortunately only the abstract is available. The full text is in Russian anyway. [xaviergisz, Aug 30 2013]

Explosive magnetic generators for feeding rail-gun launchers for solid projectiles - English version http://link.springe.../10573/22/4/page/1#
Looks like there is an English version; you can see the first two pages for free but costs $39 to get the full copy. [xaviergisz, Aug 30 2013]

Uh, is this the intro to some random paper you found on the internet?

Is this a halfbakery idea?
-- Custardguts, Aug 29 2013

No I think this is just presented that way.

This guy is thinking about this, or was at the time.
-- rcarty, Aug 29 2013

This is the abstract of a paper I just submitted.
-- xkuntay, Aug 29 2013

To whom, may I ask?
-- Custardguts, Aug 29 2013

To a scientific conference.. about space.
-- xkuntay, Aug 29 2013

Cool but there's quite a bit missing from the idea (inquiring minds and all that).

- how much of what explosive
- efficiency of explosive energy -> magnetic flux
- efficiency of magnetic flux -> bullet
- bullet material
- g-force

Umm... at least one of the figures given for terminal velocity, acceleration time or distance is incorrect. [edit:or not]
-- FlyingToaster, Aug 29 2013

As a passenger service, I can see one slight problem.
-- not_morrison_rm, Aug 29 2013

Yes indeed, the drinks service may be less than adequate.
-- 8th of 7, Aug 29 2013

Is the force distributed evenly throughout the projectile?

I'm thinking that a molten blob comes out of the end...
-- Ling, Aug 29 2013

Continuing the paper:

We propose a payload launcher called the Explosively Compressed Coil Gun (“ECCG”) that can accelerate payloads to velocities sufficient to escape Earth’s gravity. The ECCG is composed of a Helical Generator, which has proven to produce magnetic fields in excess of 200 Teslas. The center of the Helical Generator proposed is empty, as shown in Figure 1. There is a metal armature under the solenoid and explosives, such as TNT, in the metal armature. The target is to be sent at an initial speed of 10 m/s using a conventional gun.

The operation of the ECCG involves a preliminary current in the metal ring on the projectile supplied by a small capacitor on the projectile. Once the projectile passes the center point of the helical generator, the explosives are ignited. This causes the solenoid to be short-circuited by the metal armature, thereby increasing the current. As the circuit shortens, it strives to conserve the magnetic field. This in turn increases the current flowing in the solenoid. The target circuit experiences rapid magnetic flux changes. Therefore, a current that is reverse to that in the solenoid is generated in the ring. This creates a repulsive force between the solenoid and projectile. As the projectile moves towards the exit of the helical generator, so does the explosion head. The explosion is controlled so that center of the solenoid is always behind the projectile, as shown in Figure 3. Since the solenoid is not restricted by the resistance of a conductive wire, very large currents can be generated in the solenoid and induced in the ring. The electromotive force in the ring is proportional to the rate of change of the magnetic field, which in turn is proportional to the rate of explosion of the metal armature. In this paper, example calculations will be given to show the potential of the ECCG method. In the next section, the equations used for this example and results of the calculations will be explained.

The calculations are based on equations the following equations: (1)

where is the EMF in volts, ÖN is the net magnetic flux through the circuit in webers, and t is time is seconds. The current generated in the target ring is from Ohm’s law:


The force on the ring is calculated using the magnetic force expression: (3) Once force is determined, acceleration, velocity, and position are calculated using Newton’s standard equations:




3. NUMERICAL CALCULATIONS In order to see if we could reach orbital speeds using ECCG, we performed the calculations on an example case of a 6.1 kg projectile with a radius of 0.25 m. A helical generator with a 200 Tesla/m2 maximum flux was examined. For simplicity and being conservative, the projectile was assumed to be at rest when the generator was ignited and the resistance of the projectile ring was assumed to be constant at 0.07 ohms/m. Assuming the rate of change of magnetic flux as constant at 200,000 Teslas/second, the result of induced current calculation is 560,714 Amps flowing through the ring. Since the rate of magnetic flux increase is also constant, the force on the projectile linearly increases from 0 to 1.78 x 108 N in 0.001 seconds. Given the mass of the projectile at 6.1 kg, the projectile speed at the time the flux is 200T is 14.287 km/s, as shown in Figure 4. All this happens within a total distance of 4.67 meters as calculated from Equation 6.
-- xkuntay, Aug 29 2013

Maybe you should redraft this as an HB post - I'm not sure just copy-and-pasting from your m/s works.
-- MaxwellBuchanan, Aug 29 2013

And I'm rarely satisfied with this category.
-- normzone, Aug 29 2013

ah, messed up my velocity criticism, sorry.

//as the circuit shortens// [marked-for-tagline]

I'm pretty sure a space conference is going to be critical about efficiencies.
-- FlyingToaster, Aug 29 2013

//as shown in Figure 1//

is a bit of a let down...
-- 2 fries shy of a happy meal, Aug 29 2013

Yeah look it all sounds very interesting, but given the simplistic approach you've taken to modelling it, I'd brace for dissapointment if I were you, as you're about to get cut to shreds by people pointing out all of the things you're not taking into account.

This is 622 megajoules of energy. At whatever incredibly low efficiency you're going to be operating at here, that's going to be a hell of a lot of TNT.

Also, what're you going to have the 6.1kg do, anyway. Are you wanting to shoot holes in orbital space stations?

What hardware aboard your projectile will survive the 22 million G's?

Lastly, I'm pretty sure it's hard if not impossible to achieve orbit from a ballistic trajectory, because of the requirement for more horizontal velocity than vertical. So, what's this thing meant to do, anyway?
-- Custardguts, Aug 29 2013

//it's hard if not impossible to achieve orbit from a ballistic trajectory//

That is true. Gravitationally speaking, a ballistic launch is equivalent to firing something from the surface of an infinite, flat plain (or, indeed, plane) - just that the whole trajectory gets curled around.

So, if you launch ballistically, there are only three options:

(1) You exceed escape velocity, and just keep on going forever

(2) Your projectile completes an orbit that brings it right back through the launch point or

(3) Your orbit is intercepted by the earth.

You cannot launch something purely ballistically into orbit. You might be able to do something fancy with aerodynamics to deflect the projectile away from its purely ballistic trajectory; or you can of course use additional thrust to alter the trajectory.
-- MaxwellBuchanan, Aug 29 2013

All of which could be discerned by watching a few 1960's/70's era cartoons. Throw something up, it comes back down. Throw something hard enough horizontally and it flies around the earth to hit you in the back of the head.
-- FlyingToaster, Aug 29 2013

I welcome all the attacks. Not as much fun here without them. So, it is not that inefficient, or at least no more than a rail gun. Good thing is it does not require expensive capacitors.

I do not intend to send monkies in those obviously. It is meant for payload, basic electronics, etc.

I would be worried about G if Darpa had not achieved putting a guiding system in a bullet. The G in a 50 caliber is comparable. It goes to 0.3km/s in 0.5m. You can put a guide system to put it in orbit or have a space shuttle catch it.
-- xkuntay, Aug 29 2013

It seems like a lot of trouble just to build a gigantic PIAT.
-- Alterother, Aug 29 2013

//It seems like a lot of trouble just to build a gigantic PIAT.// Didn't the PIAT have a reputation of being as or more dangerous to the operators, as it was to the enemy?

...Probably an apt analogy. Look, I'm not saying the idea's a bad one - I suppose I'm just having a bit of fun here. But I am curious whether you think the science here should be taken seriously, as I think there's some gaps in the analysis.

I've even posted a superficially similar idea, called the explosively confined gun barrel. Which was my idea for concentrating explosive energy into a projectile, but without switching to, and then back from, electrical/magnetic energy.
-- Custardguts, Aug 29 2013

There is no science here. There are assumptions and calculations. This is the simplest analysis for this concept. The details are I am sure more than any theory can handle. It would have to be tested.

Concentrating explosion is nice, but you will be limited to mach speed, 0.3 - 1.5 km/s dependibg on gas.
-- xkuntay, Aug 30 2013

//but you will be limited to mach speed, 0.3 - 1.5 km/s dependibg on gas// - Ah, no. Even bullets in barrels aren't confined to that.

An EFP (we've done this before on this site, go look up explosively formed penetrators/projectiles, the wiki article is good enough for a start) can easily achieve 4+ km/sec, do so reliably, and are reasonably efficient at putting holes in things specifically designed to be hole resistant.

Similarly, the payload of a rocket is not limited to the exhaust velocity of the propellant - it's the compounding nature of the rocket equation that limits velocity.

I would contend that some clever arrangement of EFP's/rockets, explosively confined gun barrels, etc ie directly mechanical means would be simpler, cheaper, more efficient and more likely to work, as opposed to a system such as you are proposing, which exchanges mechanical energy into electrical and magnetic, and then back to mechanical.
-- Custardguts, Aug 30 2013

Hmmm interesting. It does say the EFP launched a 6 pounder at 2km/s. Imagine the G on that one. That conflicts with what I know and what Wiki writes on light gas guns. Heck, maybe thete is some quantum physics going on.

Either way, I think 4km/s is your limit with an EFP. At least until proven otherwise. I do not claim mine is more efficient, but it is one option out there. There is always the HARP cannon too.
-- xkuntay, Aug 30 2013

Good links. Similar concept, except ECCG directly employs the explosive generator, so in theory should be more efficient.
-- xkuntay, Aug 30 2013

I don't see how an unpowered projectile could ever be launched into space. The drag from the thick atmosphere near the surface (even from a tall mountain) would so large that the initial velocity would need to be insane. In all the projectile launch proposals I've seen, I've never seen any discussion of this issue, besides maybe a cursory note hat they'll need to improve heat shield technology. Considering that an orbital vehcle reentering the atmosphere rapidly decelerates and get extremely hot when hitting the upper atmosphere, makes any attempt to penetrate the lower atmosphere at a much higher speed seem completely ludicrous to me. It seems like you've got to traverse the lower atmosphere relatively slowly then accelerate as it thins out.
-- scad mientist, Aug 30 2013

I think that, if the described process did manage to get something moving at 14 km/sec, tidal forces and induced heat from magnetic flux would ensure that what came out would be a not-particularly-well-directed plasma stream.

Not that that's necessarily a bad thing, mind.
-- FlyingToaster, Aug 30 2013

//It seems like a lot of trouble just to build a gigantic PIAT//

I agree... I would suggest a 1958 Fiat as an alternative. They're smaller, but there is a surprising amount of space for feral cats.
-- Grogster, Aug 30 2013

//you will be limited to mach speed, 0.3 - 1.5 km/s dependibg on gas//

Velocity is indeed limited by the speed of sound in the propelling gas, but that gas may be *very hot*. The speed of sound is proportional to the square root of temperature.
-- spidermother, Aug 30 2013

//        There is no science here. //

That much at least is obvious.
-- Alterother, Aug 30 2013

/The speed of sound is proportional to the square root of temperature./

Perhaps one could induce a lightning bolt, then use the plasma channel as a track for the projectile. The gas/plasma should be much less dense and so offer less resistance.

The bolt might serve double duty in that it could also fill the role of the capacitor in providing juice.
-- bungston, Aug 30 2013

//There is no science here.//

Did that stop Philo T. Farnsworth?!?!

Oh, wait... never mind.
-- Grogster, Aug 30 2013

Science is solving the wave equation for the thousand something particles that erupt during the collision of nuclei at near the speed of light and trying to discern never seen before patterns in a universe of data or figuring out the meanings of dna sequences etc. There is no science here or anywhere else except a few institutes. The rest is technoogy, a much different avenue.
-- xkuntay, Aug 30 2013

Where do you get your delusions? I'm in the market for some new ones, and yours are real top-shelf stuff.
-- Alterother, Aug 30 2013

-- MaxwellBuchanan, Aug 30 2013

I eat at the same place as Yelon Muzk. They have burgers with magic mushrooms.

Technoogy. That's right. What new technology has there been in the last two decades that were truly novel?

Lightning bolt is an interesting idea. I had a similar one. Or you could point 100 lasers from different directions that intersect right before the nose of the rocket to heat up the air. There is a chance you might hit the rocket tho.
-- xkuntay, Aug 30 2013

//What new technology has there been in the last two decades that were truly novel? //

Well, given the choice between living in 2013 and living in 1993, I'd go for now. Maybe it's not the same where you are.

And 'truly novel' excludes everything; there is no possibility of inventing anything which is _truly_ novel. Pretty much everything uses old atoms.
-- MaxwellBuchanan, Aug 30 2013

[FT] You might be right. There is a pic of a railgun firing. It came out with a plume of plasma. Then again, the slug was intact.
-- xkuntay, Aug 31 2013

The navy slug had about 3% of the kinetic energy that you want to imbue yours with and came out of a timed energy-release, ie: much more efficient process, railgun.
-- FlyingToaster, Aug 31 2013

random, halfbakery