# More EM Drive Stuff

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##### Roger Smith
A wheel spinning due to inertia will keep spinning. As soon as you draw energy from it (from the generator you attached) it will slow down. If the system is efficient it will take a long time to stop. If it is inefficient it will stop quite quickly. The EM drive is not particularly efficient, but either way the wheel will stop.
You are describing reality, not the EM Drive. The EM Drive supposedly produces thrust without giving up mass. Basically, the spinning wheel becomes a super-efficient battery, storing energy in the form of momentum. If you hook a regular electric motor to a wheel and connect it to a battery, the wheel will spin at a constant speed until you disconnect the motor. The momentum of the wheel will not increase. With the EM Drive, the speed of the wheel will constantly increase. So, there has to be a point at which the spinning wheel has enough momentum to generate enough energy to produce enough thrust to overcome the losses in the system.

If you were to power the wheel with an ion thruster, for example, you could not create a perpetual motion machine. Once you switched over to using the generator, the system would begin losing mass (therefore momentum) and slow down.

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#### Lowpuller

##### Well-Known Member
Dream on...dream on.......dream until your dreams come true&#127925;&#127925;&#127925;&#127925;&#127925;&#127925;&#127925;

#### Incongruent

##### Well-Known Member
Give it a few years (decades) and jet packs will be examples of very quaint technology.
Not to be a killjoy or anything, but remember what the predictions of technology in 2012 would be? Flying cars, etc.etc.

Depending on economic (demand) and feasibility, what could be accomplished (if every government and human pooled their resources) usually won't be.

#### Incongruent

##### Well-Known Member
You are describing reality, not the EM Drive. The EM Drive supposedly produces thrust without giving up mass. Basically, the spinning wheel becomes a super-efficient battery, storing energy in the form of momentum. If you hook a regular electric motor to a wheel and connect it to a battery, the wheel will spin at a constant speed until you disconnect the motor. The momentum of the wheel will not increase. With the EM Drive, the speed of the wheel will constantly increase. So, there has to be a point at which the spinning wheel has enough momentum to generate enough energy to produce enough thrust to overcome the losses in the system.

If you were to power the wheel with an ion thruster, for example, you could not create a perpetual motion machine. Once you switched over to using the generator, the system would begin losing mass (therefore momentum) and slow down.
What if you think of the EM drive as a laser and the wheel as a pinwheel that gains momentum when hit by the laser. Well, the wheel would continue to accelerate (until light speed), but only in a frictionless environment and hooking up a generator with the capability to power the laser (and the laser's power hooked up to the generator) would quickly deaccelerate the wheel back to 0.

The EM drive needs a lot of energy to add a little momentum and the generator needs at best an equal amount of momentum as energy produced.

#### Zebedee

##### Well-Known Member
You are describing reality, not the EM Drive. The EM Drive supposedly produces thrust without giving up mass.
But requires energy as input.

Basically, the spinning wheel becomes a super-efficient battery, storing energy in the form of momentum.
OK. If (big if) you have a completely frictionless environment you can store the energy as long as you want but it's a finite amount of energy which is determined by how much energy you put into the EM drive.

If you hook a regular electric motor to a wheel and connect it to a battery, the wheel will spin at a constant speed until you disconnect the motor. The momentum of the wheel will not increase.
In the same frictionless environment (keeping this consistent) you would only need to input energy until you've reached the top speed that the motor can spin the wheel - then you can stop and you still have a flywheel with stored energy.

With the EM Drive, the speed of the wheel will constantly increase.
Only while you supply energy to the EM drive.

So, there has to be a point at which the spinning wheel has enough momentum to generate enough energy to produce enough thrust to overcome the losses in the system.
Nope - this is where your argument fails. If you use the spinning wheel to power something you decrease it's energy and since the EM drive takes more energy in than it outputs in thrust using the spinning wheel to power the EM drive results in a net decrease in the energy stored in the wheel (the speed of the wheel is irrelevant).

If there is a logical argument to this, you've not quite captured it properly - do you have a source for this argument.

##### Roger Smith
What if you think of the EM drive as a laser and the wheel as a pinwheel that gains momentum when hit by the laser. Well, the wheel would continue to accelerate (until light speed), but only in a frictionless environment and hooking up a generator with the capability to power the laser (and the laser's power hooked up to the generator) would quickly deaccelerate the wheel back to 0.

The EM drive needs a lot of energy to add a little momentum and the generator needs at best an equal amount of momentum as energy produced.
You're still missing the point that the EM Drive is supposed to be reactionless. In the laser example, the photons hit the target on the wheel and are re-emitted. The energy from them is lost to the system. The EM Drive supposedly doesn't emit anything, so the energy is not lost.

Anyway, people with a much better understanding of physics have used the same example (and several others) that illustrate that the EM Drive is unlikely to operate as described. Once you start violating the laws of physics, a lot of amazing things are possible.

-- Roger

#### Incongruent

##### Well-Known Member
You're still missing the point that the EM Drive is supposed to be reactionless. In the laser example, the photons hit the target on the wheel and are re-emitted. The energy from them is lost to the system. The EM Drive supposedly doesn't emit anything, so the energy is not lost.

Anyway, people with a much better understanding of physics have used the same example (and several others) that illustrate that the EM Drive is unlikely to operate as described. Once you start violating the laws of physics, a lot of amazing things are possible.

-- Roger
But energy is turned to heat whenever a photon strikes a surface, because no mirror is perfect.

And heat is.... energy and gets emitted

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#### Incongruent

##### Well-Known Member
You're still missing the point that the EM Drive is supposed to be reactionless. In the laser example, the photons hit the target on the wheel and are re-emitted. The energy from them is lost to the system. The EM Drive supposedly doesn't emit anything, so the energy is not lost.

Anyway, people with a much better understanding of physics have used the same example (and several others) that illustrate that the EM Drive is unlikely to operate as described. Once you start violating the laws of physics, a lot of amazing things are possible.

-- Roger
By reactionless, you mean thrust is produced without expelling anything in the direction opposite the thrust. However, when the photons "push", they themselves lose energy which is transferred to the drive. In other words, the photons are supposedly using more of their energy to push on the front of the drive than on the back. Energy is emitted, since the photons also create heat when they bounce off, but not to propel the craft.

#### Incongruent

##### Well-Known Member
1) Can it be used in model rockets?
A: No

2) Can it be used in high power rockets?
A: No

3) Then why are we arguing about it?

#### Lowpuller

##### Well-Known Member
In micro format it could be used to power your rocketry electronics.

#### ThirstyBarbarian

##### Well-Known Member
TRF Supporter
I think the idea of the flywheel is confusing the issue. The key point made in this article is that if you apply a constant force, you get a constant acceleration, a constant linear increase in velocity. Kinetic energy increases as the square of the velocity. So with a reactionless drive, you have a system where you can put energy in LINEARLY, but increase the kinetic energy QUADRATICLY. Eventually you reach a break even point where the kinetic energy of the mass being pushed along by the EM drive EXCEEDS the energy put into running the drive. That violates thermodynamics.

##### Roger Smith
I think the idea of the flywheel is confusing the issue. The key point made in this article is that if you apply a constant force, you get a constant acceleration, a constant linear increase in velocity. Kinetic energy increases as the square of the velocity. So with a reactionless drive, you have a system where you can put energy in LINEARLY, but increase the kinetic energy QUADRATICLY. Eventually you reach a break even point where the kinetic energy of the mass being pushed along by the EM drive EXCEEDS the energy put into running the drive. That violates thermodynamics.
I was trying to translate it into something you can picture without the math. But, the math in that paper actually isn't too overwhelming.

-- Roger

#### rocket_troy

##### Well-Known Member
No. You're forgetting that the EM Drive is reactionless. The rotating wheel can eventually reach a point where its momentum is great enough to allow the generator to generate enough power to overcome all of the losses in the system and still continue to accelerate the wheel. That's one of the problems that you run into when you start violating the laws of physics.

Another way to think about it ... if you set a wheel spinning in space, Newton's First Law says that it will continue to spin at the same speed. If the generator hooked up to the wheel provides enough energy to allow the EM Drive to produce any thrust at all, the wheel will continue to speed up. So, the wheel will always speed up regardless of losses in the generator.

Granted, there is no way to hook a generator up to the wheel in space and have it generate electricity. But, even a real-world example would work if you just waited until the wheel was spinning fast enough to generate enough power to overcome the losses in the system. At that time you could hook up the generator and make Newton cry.

-- Roger
Roger,
The premise of your argument is correct, it's just the way you explained it needs some fine tuning. The reason why you can generate perpetual motion from a reactionless device such as this is that yes, you can drive a generator with a wheel or balanced arms because providing your drive is reactionless, you can theoretically extend the length of the arms or diameter of the wheel so the amount of force produced from the drive has enough leverage to exceed the force required to drive the generator. Remember you can turn any generator with your little finger provided you have enough leverage. Again, because the drive is reactionless, it will never run out of fuel (reaction mass) or require reaction mass to be transferred from the core so it can theoretically keep accelerating as the only drag on it is the force required to turn the generator.
There's also nothing stopping you from hooking a generator up to a wheel in space and generating power from it - you just need another wheel rotating in the opposite direction to counterbalance the torques.

Troy