Electromagnetic propulsion

[Urge]

A electromagnet can be used to propell something foreward, forexample it can make a metallball float above it, or it can shoot out something at high speed if you make a coil-gun.

So if a metal-plate is attached to a electromagnet that tryes to push it away, will not the metall-plate drag the electromagnet and its powersource with it? I wondered about this, and found out later that it might not work because of "the third law of Newton" that says that a something that pushes something will be pushed in the other direction - but im not sure if this applies for magnetism.

Another form of electromagnetic engine that can be created is a sort of electromagnetic rocket that shoots out metall-dust. This dust can perhaps be collected by another electromagnet that i positioned further down (if the dust is first shoot out backwards, and then pulled to the left or the right by another magnet and re-collected it shouldnt slow down the propulsion) and then be re-used later.

I have heard that the only form of electromagnetic propultion-system that is ready now is the ion-rocket, but there should be more efficient ways of using electromagnetism for propulsion.

 

[Lindley]

So if a metal-plate is attached to a electromagnet that tryes to push it away, will not the metall-plate drag the electromagnet and its powersource with it? I wondered about this, and found out later that it might not work because of "the third law of Newton" that says that a something that pushes something will be pushed in the other direction - but im not sure if this applies for magnetism.

It applies to everything on the macroscopic level. (I make no claims regarding the quantum level----Newton's laws never really worked there.)

The problem is that the magnetic force isn't pushing the plate away; it's trying to separate the plate from the magnet. In other words, it applies equally to both, and only if one of them isn't fixed does that one end up with net motion. (Technically it has to do with how large the thing each is fixed to is.) Attaching the two to each other doesn't cause anything interesting to happen, you've just got equal and opposite forces applied to different points on the same object.

Another form of electromagnetic engine that can be created is a sort of electromagnetic rocket that shoots out metall-dust. This dust can perhaps be collected by another electromagnet that i positioned further down (if the dust is first shoot out backwards, and then pulled to the left or the right by another magnet and re-collected it shouldnt slow down the propulsion) and then be re-used later.

You're proposing to use metal shards as rocket propellant, and then re-capture them later? Hmm. Neat idea, but I'm fairly sure it wouldn't work either. Even if you evenly distributed the horizontal pull in all directions to avoid deflecting the rocket, the shards would still have backwards-facing kinetic energy; and upon re-capture, the absorbtion of that energy would negate the kinetic energy produced by accelerating them in the first place.

I have heard that the only form of electromagnetic propultion-system that is ready now is the ion-rocket, but there should be more efficient ways of using electromagnetism for propulsion.

There are----most simple motors, including the engines of many light aircraft, use something called magnetos to power the engine. It's not a new idea.

 

[Bill Morris]

No matter how you configure it, there are force vectors that cancel out those in the opposite direction. It's like being in a box in space and trying to propel it by throwing a ball to bounce it off a wall. On the throw, you get force in one direction (Newton's Third Law), and then the force received by the wall cancels it out. And no matter how much the ball bounces around, it all comes out even: no propulsion, unless the ball leaves your closed system.

 

[Romulan_spy]

Newton's 3rd Law applies to every force. So, you can't take both the electromagnet and the metal plate with you as you move. One of the two has to stay behind for the other to be pushed forward.

 

[Urge]

No matter how you configure it, there are force vectors that cancel out those in the opposite direction. It's like being in a box in space and trying to propel it by throwing a ball to bounce it off a wall. On the throw, you get force in one direction (Newton's Third Law), and then the force received by the wall cancels it out. And no matter how much the ball bounces around, it all comes out even: no propulsion, unless the ball leaves your closed system.

I was kind of hoping that throwing a ball might help. A closed system of propulsion would be cool. In starwars episode 3 there is a scene at the beginning where a big spaceship is slowing down (trying to avoid diving into the atmosphere) by lowering metal-plates behind the rocket-engines, and then firering them against the plates, but I guess (with this annoying newtons third law) it wouldnt have slowed the ship down in real life, but it might have made the ship shake if its pushed in two directions at once - so then you turn milk into butter or something on the way down

Some youtube videos I found:
Something called the Hex-lifter

Hmhm... I didnt find this other video, it was a experimental engine where a small boat was propelled foreward by a strange spinning wheel that..... Never mind, impossible to explain, but it didnt have a propell or annything else that was in contact with water or air, just the odd spinning wheel in the box that was somehow managing to give a one-way push foreward, slow but intresting.

 

[Lindley]

(with this annoying newtons third law)

Annoying in space, highly useful in atmosphere. Airplanes wouldn't fly nearly so well as they do if they had to rely on Bernoulli's principle alone; quite a bit of lift is the result of air hitting the underside of the wings and being deflected downward.

 

[Iasius]

Maglev trains are in principle quite nice because the 'engine' is in the track, you don't have to carry it with the train. Also, at low speeds rolling resistance is much more important relative to friction from air than at high speeds. Maglev trains are really useful in areas where you want high speeds combined with frequent stops since because of its advantages maglev trains can have very high accelerations.
Of course, the downside is that you have to lay entirely new and expensive tracks which is the main reason why maglev trains never caught on.

 

[Brandonv]

There is also the magnetic sail (wikipedia).

A magnetic sail or magsail is a proposed method of spacecraft propulsion which would use a static magnetic field to deflect charged particles radiated by the Sun as a plasma wind, and thus impart momentum to accelerate the spacecraft [1] [2]. A magnetic sail could also thrust directly against planetary and solar magnetospheres.

You could also fire a particle beam at the sail.

 

[Urge]

Without the beam-gun stopping the propulsion somehow? If something like that could be done (avoiding the third law of newton somehow), it would be easier to use electricity for propulsion, without having to use something else (like hydrogen-plasma) as well.

 

[Jadzia]

Imagine sitting on a sledge on a frozen pond (slippy). Somebody (the sun) throws a football at you from where they are standing on the bank. You catch the ball and you feel a shunt from the impact that causes you to slide a little. Which way do you slide?

Next (because you're magnetic) you throw the ball back whence it came. You feel a recoil with the throw. Which way do you slide with that recoil?

Now imagine that happens repeatedly, and the pond is so slippery that once you're moving you don't slow down with friction. With each ball you deflect back towards the sender, you gain a little speed.

 

[Urge]

It works for a while, but as you slide the ball has to be thrown longer and longer, so it wont work for propulsion. Or perhaps? With some sort of sail, a laserbeam can work - but it has to be a very good one, so that it can shoot hundreds (or millions) of thousand kilometers without splitting into a broad, weak and useless beam. But will it work even better if the craft use the beam-energy to throw a laser back at the first one? Then the laser and the craft can exchange light in a energy-saving manner.

If not light, the idea can perhaps work with something physical as well, like balls of snow or metall. Then it will be two large rows of balls behind the spacecraft, one going back to the throwing-machine, and one going from the throwingmachine to the craft. The craft can use the kinetick energy from the ball to produce electricity while slowing it down (if it enters a hole in the craft that slows it down to its own speed), and then throw it back with slightly less speed, since some energy is lost, and other is transfered to acceleration in the craft.

A absurd form of propulsion

But fun to think about.

 

[Jadzia]

The electromagnetic propulsion uses the solar radiation in the same way as the person on the ice deflecting footballs.

This radiation travels a long long way out into space so throwing a long ball isn't an issue, but the sun would give a stronger push where that radiation is most dense, which is close to the sun. So a sail ship which makes a close pass of the sun would get the greatest push out into space.

The problem which emerges is that as you accelerate upto high speed, you're travelling almost as fast as the particles the sun is throwing out, so at that point they're going to be imparting very little momentum to you. That would be your terminal velocity. Whether you get close to that speed in any reasonable time depends on the amount of plasma you're deflecting, which depends on how powerful your magnets are.

 

[Lindley]

And then there's the question of how you slow down again...

 

[Birdog]

In starwars episode 3 there is a scene at the beginning where a big spaceship is slowing down (trying to avoid diving into the atmosphere) by lowering metal-plates behind the rocket-engines, and then firering them against the plates, but I guess (with this annoying newtons third law) it wouldnt have slowed the ship down in real life, but it might have made the ship shake if its pushed in two directions at once - so then you turn milk into butter or something on the way down

Those are called thrust reversers and are real world tech on a lot of jet aircraft. Basically it turns the engine thrust around so that it now is thrusting forward to act as a brake. AFAIK all civil transports have them. I thought it was quite cool to see them in action in that movie. It allowed retro thrust without flipping the ship end for end.

 

[Urge]

Never mind...

 

[Zachary Smith]

Actually, I've often wondered if the same force that drags an off-balance washing machine across a floor might be used for propulsion. If you had a series of rotating weights generating spin in coordination along a common direction at a common time and then had a "rest" spin through the remainder of the rotation, it seems like it would generate a "drive". A washing machine lurches across the floor in fits and stutters because there is only one source of "drive" but if you had a second rotational force keying in at the instant the "impulse" from the first weighted load ceased it's "push" you could get a smooth motion along an axis of drive. If you change the angle from horizontal to vertical, you get lift. If you had several working in series you could get lift AND directional control in all three planes of axis.

Just a thought . . ..

 

[Crazy Eddie]

[/I]I was kind of hoping that throwing a ball might help. A closed system of propulsion would be cool. In starwars episode 3 there is a scene at the beginning where a big spaceship is slowing down (trying to avoid diving into the atmosphere) by lowering metal-plates behind the rocket-engines, and then firering them against the plates, but I guess (with this annoying newtons third law) it wouldnt have slowed the ship down in real life, but it might have made the ship shake if its pushed in two directions at once - so then you turn milk into butter or something on the way down

Actually, those were thrust reversers. The planes just bent the exhaust component forward instead of flying out backwards as normal.

ETA: nm, birddog beat me to it.

 

[sojourner]

Actually, I've often wondered if the same force that drags an off-balance washing machine across a floor might be used for propulsion. If you had a series of rotating weights generating spin in coordination along a common direction at a common time and then had a "rest" spin through the remainder of the rotation, it seems like it would generate a "drive". A washing machine lurches across the floor in fits and stutters because there is only one source of "drive" but if you had a second rotational force keying in at the instant the "impulse" from the first weighted load ceased it's "push" you could get a smooth motion along an axis of drive. If you change the angle from horizontal to vertical, you get lift. If you had several working in series you could get lift AND directional control in all three planes of axis.

Just a thought . . ..

There have been alot of reactionless motors and perpetual motion machines that have attempted exactly this type of thing. None of them work. The example of a washing machine moving when in use is flawed because it is using an outside force. The motion of the mechanism inside is causing the entire machine to flex and vibrate, moving first one side, then the other which in turn inches it across the surface of the floor. If you suspended it in a the center of a weightless vacuum it would not move.

 

[Lindley]

So then the key to any kind of "space drive" would be to figure out how to create a friction-like force against space itself, it seems.

 

[Asbo Zaprudder]

Conservation of energy, linear momentum and angular momentum are the result of the fundamental displacement and rotational symmetries of spacetime (Noether's first theorem -- any differentiable symmetry of the action of a physical system has a corresponding conservation law). If you could somehow make spacetime exhibit asymmetry, then I guess you could exploit it to create a reactionless drive.