Wow, it's been some time since I've seen this thread, and the "first unread" bug caught me. Anyway, I answered this a year ago:

Unless energy or mass leaves the system, it doesn't matter. You can't get something for nothing. It's that simple.

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The Leif Ericson Cruiser

Well that is a sort of many times proposed but currently impossible to construct and maintain; the antimatter drive.

The only known way is to open the system, either leveraging a planet's magnetic field, or using solar wind.

Otherwise, Antoniseb is correct - all means using a closed system suffers from the conservation of momentum. You can move the elements around relative to one another, but the center of mass of the system will go absolutely nowhere (gyroscopes or not).

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Well forgive me that just sounds like dogma!
Sure I know Conservation of Momentum is like a physical Law, look at my opening thread!

This is questions and answers so when I make a new proposal for a drive that breaks the law I would prefer an answer to why my latest theory is wrong.

Some facts: The production of antimatter from energy is a known physical effect, fast moving protons with high energy are collided with stationary atoms and the kinetic energy is converted to mass (protons and anti protons) which did not exist before. E=Mc2 a whole lot of energy is turned into a small amount of mass. The mass of protons and anti-protons can be separated with magnetic fields as they are ions ( and anti ions ) Mass that undergoes acceleration will make an equal and opposite reaction as it is accelerated to the other physical end of the ship. Protons and anti-protons will annihilate with each other on contact to make photon energy.

Where is the countering force? Is it true to say the energy which is transferred through the ship counteracts with the mass? As I see it this is just an equal flow of electrons along wires with no appreciable effect on the ships position. I just want to understand why I am wrong here!

Because it sounded like you were trying to get around conservation of momentum, and that isn't possible, as you said yourself. Whatever trick you try, it won't work, so the answer is the same. And it isn't dogma: conservation of momentum has been verified over and over again.

Matter/anti-matter rockets are theoretically possible. However, they would still be rockets, and would work by the same principles as any other rocket. You could make this a chemical rocket, and the results would be the same.

Which would put stress on the rest of the ship, but unless that rocket is directed so that the thrust leaves the ship, it isn't going anywhere. The way I read your idea, you were suggesting firing a rocket inside the ship, then somehow sending the energy from the thrust back to the rocket again. And as I said, you can do anything you want to inside the ship, but it won't matter a bit unless something leaves it in some direction. If you are going to build a rocket, there's no point trying to reuse the energy. Point it outside in some direction and be done with it.

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The Leif Ericson Cruiser

http://www.orionsarm.com/ships/Reactionless_Drives.html
Here are some more scientific and maybe possible systems.

Please note that "Orion's Arm" is a science fiction universe.

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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

That's right; the reactionless drives in OA would only work if momentum is not conserved on a large scale, or if such a thing as negative inertia were possible- both concepts are unlikely but not yet proved to be impossible.

The Breakthrough Physics Program, initialy funded by NASA, came up with a lot of different reaction-free drive possibilities, some of which OA has adapted to suit our purposes; but each of these concepts requires the laws of physics to be subtly (or not-so-subtly) different to the physics currently known.

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I understand why there is no net thrust from an oscillating mass ,fast one way then slowly the other way but the pop pop boat engine and the valveless pulse jet engine
both suck and blow mass slowly in and quickly out through the same pipes.

Not efficient but very simple.

Must be some interaction with the surrounding fluid (water for the pop pop and air for the pulse jet).
Can an oscillating mass interact with the aether (OK space time) in a similar way.
Mass already interacts this way but EXACTLY in proportion to the acceleration of the
mass.That is why it adds to zero though a full cycle.
There is the problem.How can we make it not exactly in proportion?.

in deep space the solar sail would be exposed to light from all directions. Controlling a sail with approaching uniform loading seem difficult. Controlling a sail to sail windward is possible but only easy in the solar-wind density near a single source.