Neutron Space Drive

[Iggyz]

As the attached picture shows, the Neutron Space Drive consists of two neutron generators (A), two parabolic mirrors  (B) and a neutron absorber (C).

They are all fitted inside a vacuum container capable of shielding the surroundings from radiation.

The beams of the two neutron generators are reflected by their parabolic mirror and hit the neutron absorber.

The recoil of the lasers is negated when the neutrons hit the parabolic mirrors (black arrows).

Thrust (blue arrow) is generated when the neutrons hit the neutron absorber and transfer their momentum and kinetic energy to it.

Do you think this can this work?

[Ixokani]

The mirrors and absorber are superfluous. Just shoot the neutrons out the back, if you really want to use neutrons...

[sghill]

My layman's $0.02 is that a neutron rocket has the obvious advantages over a photon rocket that neutrons have mass, and "fast" neutrons have high energy (2MeV at 20,000km/sec.).

You still have to obtain your neutron beams though.  I only know three ways to do it: Nuclear fission, lasers striking a capture target, and particle accelerators.

If you go the nuclear fission route, I believe you'd be more efficient just using your reactor to either heat a propellant gas like hydrogen as in a thermal Nerva rocket, or a gas like Xenon in a nuclear/electric ion thruster instead of capturing and directing the wildly less massive neutrons produced in the reactor.

A laser/target system to create fast neutrons would still consume the target, so you are still carrying mass with you and throwing it out the back (see image below).

Let's all just agree that a particle accelerator just isn't practical as a vehicle engine.

[Iggyz]

The mirrors and absorber are superfluous. Just shoot the neutrons out the back, if you really want to use neutrons...

Thank you for the feedback Ixokani,

It is supposed to be a closed thruster like for instance the EmDrive. This would be safer and less polluting. Do you think it can function as a closed thruster?

[Iggyz]

This isn't "new physics" and should be under the advanced concepts threads.

My layman's $0.02 is that a neutron rocket has the obvious advantages over a photon rocket that neutrons have mass, and "fast" neutrons have high energy (2MeV at 20,000km/sec.).

You still have to obtain your neutron beams though.  I only know three ways to do it: Nuclear fission, lasers striking a capture target, and particle accelerators.

If you go the nuclear fission route, I believe you'd be more efficient just using your reactor to either heat a propellant gas like hydrogen as in a thermal Nerva rocket, or a gas like Xenon in a nuclear/electric ion thruster instead of capturing and directing the wildly less massive neutrons produced in the reactor.

A laser/target system to create fast neutrons would still consume the target, so you are still carrying mass with you and throwing it out the back (see image below).

Let's all just agree that a particle accelerator just isn't practical as a vehicle engine.

Thank you sghill for the feedback.

I agree that a particle accelerator is not as practical as for instance an ion rocket. I was just wondering if this setup can work as a closed thruster. Do you think that is possible?

[zubenelgenubi]

Moderator: Agreed and moved.

This isn't "new physics" and should be under the advanced concepts threads.

[cdebuhr]

The mirrors and absorber are superfluous. Just shoot the neutrons out the back, if you really want to use neutrons...

Thank you for the feedback Ixokani,

It is supposed to be a closed thruster like for instance the EmDrive. This would be safer and less polluting. Do you think it can function as a closed thruster?

No.  You're still just throwing massive particles around inside a closed box.  Ignoring for the moment the practical consideration of what you propose to use for a neutron mirror (we'll just give you that and assume you've got a magic perfect neutron reflector), how will this get around classical conservation of momentum?  Hint: it won't.  There's nothing here with even a prospect of violating Newtonian mechanics. 

[aceshigh]

Moderator: Agreed and moved.

This isn't "new physics" and should be under the advanced concepts threads.

He is proposing a reactionless drive, (no mass expelled) so I would think this IS "new" (and proven flawed in this case) physics.

[aceshigh]

As the attached picture shows, the Neutron Space Drive consists of two neutron generators (A), two parabolic mirrors  (B) and a neutron absorber (C).

They are all fitted inside a vacuum container capable of shielding the surroundings from radiation.

The beams of the two neutron generators are reflected by their parabolic mirror and hit the neutron absorber.

The recoil of the lasers is negated when the neutrons hit the parabolic mirrors (black arrows).

Thrust (blue arrow) is generated when the neutrons hit the neutron absorber and transfer their momentum and kinetic energy to it.

Do you think this can this work?

No, it canīt work.

The sum of the momentum in every vector there is zero.

why the mirrors? What difference do you expect them to make? Why not shoot directly at the neutron absorbers? It would make your arrows easier...

[ppnl]

To see why this will not work just replace the neutrons with rocks. Figure out why it will not work with rocks. It will not work with neutrons for the exact same reason. A neutron is just a tiny little rock with some other strange properties that just don't matter here.

[IRobot]

The mirrors and absorber are superfluous. Just shoot the neutrons out the back, if you really want to use neutrons...

Thank you for the feedback Ixokani,

It is supposed to be a closed thruster like for instance the EmDrive. This would be safer and less polluting. Do you think it can function as a closed thruster?

Now that's a new selling point for in-space rocket engines! Pollution reduction!

[gparker]

The recoil of the lasers is negated when the neutrons hit the parabolic mirrors (black arrows).

Your arrows at the mirrors show the momentum change as if the mirrors had absorbed the neutrons. If the neutrons are reflected then you need another pair of arrows at the mirrors parallel to the neutrons' outbound paths. (Imagine that the mirror absorbs a neutron (first arrow) and then emits a neutron (second arrow).) These new arrows negate the momentum change of the neutron absorber. Like this:

[edzieba]

Let's all just agree that a particle accelerator just isn't practical as a vehicle engine.

A minor point of order (given OP's concept is another unworkable reactionless drive): all rocket engines other than photon rockets are particle accelerators. They take particles sat in your propellant tanks, and accelerate them to a few km/s in a nice stream (and as close to collimated as practical without an infinite nozzle) pointed out the back. They're just a lot more efficient than cyclotrons, synchrotrons, or linacs.

[Crispy]

I think this is "shaking things around inside a box" drive number 6 from you Iggyz?
(unless the mods have deleted any, in which case it's more)

If no mass leaves the vehicle, it can't accelerate. No amount of mirrors, springs, pumps, lasers, or wheels can change this simple fact. Until you understand this, you will continue to get the same responses I'm afraid.

[sghill]

I think this is "shaking things around inside a box" drive number 6 from you Iggyz?
(unless the mods have deleted any, in which case it's more)

If no mass leaves the vehicle, it can't accelerate. No amount of mirrors, springs, pumps, lasers, or wheels can change this simple fact. Until you understand this, you will continue to get the same responses I'm afraid.

:>

[Iggyz]

Thank you all for your feedback. 

The neutron beams are reflected by the mirrors and they continue to move towards the absorbers.

This implies they have preserved some of their momentum and kinetic energy.

If this is correct, it probably also implies the recoil of the neutron generators is only partly negated when the neutrons are reflected by the mirrors, and this will enable the space ship to continue to move forward, but at a reduced speed.

Also, the remainder of the neutrons' momentum and kinetic energy will add to the thrust the moment the neutrons hit the absorbers.

P.S.,

When the neutrons are ejected by the neutron generator they have the same momentum as the recoiling neutron generators. Wouldn't the neutrons have to transfer all their momentum to the mirrors in order for the recoiling mirrors to negate the momentum of the neutron generators?

[etudiant]

I think this is "shaking things around inside a box" drive number 6 from you Iggyz?
(unless the mods have deleted any, in which case it's more)

If no mass leaves the vehicle, it can't accelerate. No amount of mirrors, springs, pumps, lasers, or wheels can change this simple fact. Until you understand this, you will continue to get the same responses I'm afraid.

:>

Not sure if this is relevant, but thought this was a somewhat similar situation:
https://en.wikipedia.org/wiki/Blackbird_(wind-powered_vehicle)

[cdebuhr]

I think this is "shaking things around inside a box" drive number 6 from you Iggyz?
(unless the mods have deleted any, in which case it's more)

If no mass leaves the vehicle, it can't accelerate. No amount of mirrors, springs, pumps, lasers, or wheels can change this simple fact. Until you understand this, you will continue to get the same responses I'm afraid.

:>

Not sure if this is relevant, but thought this was a somewhat similar situation:
https://en.wikipedia.org/wiki/Blackbird_(wind-powered_vehicle)

Blackbird is not similar in that it is not a closed system. 

[cdebuhr]

Thank you all for your feedback. 

The neutron beams are reflected by the mirrors and they continue to move towards the absorbers.

This implies they have preserved some of their momentum and kinetic energy.

If this is correct, it probably also implies the recoil of the neutron generators is only partly negated when the neutrons are reflected by the mirrors, and this will enable the space ship to continue to move forward, but at a reduced speed.

Also, the remainder of the neutrons' momentum and kinetic energy will add to the thrust the moment the neutrons hit the absorbers.

P.S.,

When the neutrons are ejected by the neutron generator they have the same momentum as the recoiling neutron generators. Wouldn't the neutrons have to transfer all their momentum to the mirrors in order for the recoiling mirrors to negate the momentum of the neutron generators?

It doesn't matter.  You're literally just shaking a box full of rocks, its just that you're rocks are neutrons.  There's is no way to generate thrust this way in the context of Newtonian mechanics.

[1]

The neutron beams are reflected by the mirrors and they continue to move towards the absorbers.

This implies they have preserved some of their momentum and kinetic energy.

If this is correct, it probably also implies the recoil of the neutron generators is only partly negated when the neutrons are reflected by the mirrors, and this will enable the space ship to continue to move forward, but at a reduced speed.

No. Momentum is conserved, not preserved.

A particle reflecting off of something has a component of its velocity completely reversed. This means the momentum of your particle has changed. Drastically. In order to redirect your neutrons backwards, the mirrors need to get a momentum kick forward. A particle reflecting dead-on has its momentum changed by -2x what it was before. That corresponds to a positive 2x momentum kick on the reflecting body.

You keep treating velocity and speed as interchangeable. This leads me to believe you don't have a grasp of vector algebra; which in turn explains why you have difficulty understanding why every single proposal you've made suffers from the same fatal flaw. And my advice is to forget about kinetic energy altogether for the time being; as it's actually a meaningless quantity by itself.

As your natural intuition is incorrect, you need to develop it. The only way to do this is to knuckle down and learn the subject. Rather than post a picture and notional arrows, try to actually run the math on your system. That makes it much easier to help you understand errors, and much less likely that your entire thread will end up being eaten by the grue.