all electromagnetic radiation consists of photons, they have momentum if not rest mass.

Let's sum up:

Assuming this is an object in free space, unless you come up with a magic space drive (something that shouldn't work based on known physics) either something external to the object must affect it (hits it, pushes it, grabs it with an electromagnet, whatever), or the object needs to throw something in one direction to go in another. That can be mass or energy. That's it. You can do anything you want to inside the object, but it won't matter a bit unless something is thrown away in some direction.

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The Leif Ericson Cruiser

Well thats the point of this discussion, a method to try to convert external energy, abundant in the universe, into movement in a vacuum. The conversion of Electro-magnetic radiation into a moving force.

They are both forms of energy, is there a way to convert one to the other?

As previously discussed, light sails will do that. You just need a star or other source of light handy. But it isn't a magic space drive, it is a spacecraft that is depending on an external energy source.

Again, as previously discussed, photons have momentum. Bounce the photons off the light sail and you add momentum to the light sail (and whatever it is carrying).

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The Leif Ericson Cruiser

I still don't get it. It works with a can, why not with a coil gun? Isn't it basically the same thing?

Here's how I did:

1) Get a can and attach an elastic on its bottom
2) Attach a heavy object in the other end of the elastic
3) Pull the elastic (this is equivalent to chargin the capacitor) some inches back
4) Quickly let it go in the air.

The can DOES move to the direction of the movement of the object hitting it, so momentum is transferred. Why wouldn't it work with a coil gun?

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It will work, as long as the gun is outside of the can. Then the gun will move on way, and your spaceship will move the other.

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As above, so below

Yes but only in one direction, I want full control.(am I a control freak?)

you want a flying saucer, I know how you feel.

Obvious Flatlander thinking! With that experiment, you have all sorts of opportunities for friction and external forces to come into play. Think of it this way: Take an electric car up in the Shuttle. Carefully place it outside the cargo bay and start it up. What happens?

It might wobble around a bit, but it isn't going to move off in any particular direction. A car depends on the friction against the tires for its motion. We're so used to it, it's hard to think about the world without it. Now take your experiment, add something to hold the elastic in place that can be disconnected by remote control. Do this experiment in orbit. What happens? It will shift position slightly with the change in the center of mass, it might wobble a bit, but that's it. It will not move off and continue moving.

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I say there is an invisible elf in my backyard. How do you prove that I am wrong?

Disclaimer: Avatar is not an official NASA image and does not imply any specific interplanetary or interstellar capability.

The Leif Ericson Cruiser

I think that it works in that the can will travel in the direction, but to reset it the ball would have to be pulled back, resulting in a null return

How about this one. I thought of this some time ago as part of a game, and won't be crushed in the least if it won't work, but if there were ever e a thread to ask...

The basic idea is three strong magnetic fields. The ship configuations would be roughly like this:

-
A
+

+
==========>
-

-
B
+

A and B are set on outriggers and could actually look like the ship used for Van Rijn's avatar. Each outrigger generates a strong magnetic field. Since the polaity is different, A and B are drawn together. Since the polarity on the ship, which is less, is the same at the outrigger on that side, it would be repelled. Placement of the centers of the fields would set the direction.

Bah... I just figured out why it won't work. The outriggers wouldnt come straight together, right? They would be pushed back as the ship is pushed forward.

nevermind...

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A Nerd can figure out how long it will take the original Enterprise traveling at warp 6.5 to travel from Regulus to Antares.
A Geek will think he can use that to pick up a girl in a bar.
A Dork knows he can't pick up the girl with it, but will hang around for hours anyway, just in case she asks.
She might. You never know.

He did mention that the drive mass was replaced for each shot. If that meant fed from a magazine rather than collected and carried, and the driving force was something other than a mechanical device, I can see where he's going with it.

I'd just hate to be in the engine room when the order for full speed came down.

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A Nerd can figure out how long it will take the original Enterprise traveling at warp 6.5 to travel from Regulus to Antares.
A Geek will think he can use that to pick up a girl in a bar.
A Dork knows he can't pick up the girl with it, but will hang around for hours anyway, just in case she asks.
She might. You never know.

There is no friction and external forces operating here (considering the ideal scenario for the sake of simplicity). All there is is the energy stored on the elastic being released as kinetic energy, which is turn transfered to the can.

Now THIS makes perfect sense. I never really thought about that part, hehe.

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But it doesn't matter if they are replaced or not. All that is important is that nothing can escape from the system. It won't work for the same reason that you can't pull yourself off the ground by pulling up on your belt, no matter how strong you are. Or why the astronauts can't get the Space Shuttle out of orbit by pushing against the back wall.

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As above, so below

????

Um, magnetic fields are stationary forces and wouldn't effect the position of the ship in any way unless they were pushing on some ionised particles which would be considered the fuel and are spent (affecting mass) which is what I want to avoid.

I was wrong. It's like Jens said, actually, I was just having difficulties understanding his statements the right way. I was also taking my childhood memories too seriously! :P

What I was failing to realize is that the kinetic energy I thought I was getting from the electromagnetic force after the hit also comes from the recoil (I was considering only the impulse when the coil is fired as the reaction from the recoil), so the collision just counters it and nullifies everything.

The coil, in the end, just splits the momentum in both directions for a while (so the resulting momentum is zero) and breaks the equilibrium of the system, until the projectile hits. The correct analogy would be tyeing two balls of different mass to each other via an elastic, pulling them apart and letting them collide. The outside energy used just keeps the system apart, and once it's dissipated the equilibrium is restored.

So I stand corrected. I apologize for the junk comments. I also feel embarrassed about the suggestion now :P

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Not as much as lifting a 50 lb gyroscope by one hand... what's going on here?

Just supposing a gyroscope is lighter when spinning (anticlockwise?) then accelerating it whilst spinning , stopping it , pulling back , repeat. Would that work?

The anti-clockwise detail suggests the spin axis must match the gravity vector, which means the effect wouldn't be very useful in deep space.

But uh, is this for real?

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My thoughts exactly - a resultant reduction in weight wouldn't be any help at all if the mass stays the same, anticlockwise is just a perception, keep it spinning and turn it upstide down, now it's clockwise.

Now I read this http://depalma.pair.com/GenerationOf...onalForce.html I think it must be bunk but can someone cite an experiment disproving this effect?