Author Topic: Propulsion idea based on the MEDUSA spacecraft using nuclear pulse propusion  (Read 4601 times)

Offline Iggyz

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The attachment describes propulsion based on the MEDUSA spacecraft concept by Johndale Solem.

If you are not familiar with the MEDUSA nuclear pulse propulsion concept I suggest you first read https://en.wikipedia.org/wiki/Nuclear_pulse_propulsion#Medusa before you read the attachment.

Hopefully, after reading, you will not have the feeling that you have wasted your time. If so, I offer you my apologies upfront.

Have a nice weekend.

Offline rakaydos

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What is an "electromagnetic explosion"?

Offline ZChris13

What is an "electromagnetic explosion"?
disclaimer: I haven't read the pdf
Presumably an "electromagnetic explosion" is a very, very bright light.

Offline meberbs

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What is an "electromagnetic explosion"?
Nothing. All this concept seems to be is tossing something forward (with a poorly designed rail gun) attached to a tether and then pulling it back. It is entirely missing the "material from the nuclear explosion is expelled backwards" portion of a MEDUSA type nuclear propulsion. This concept would not work.

Offline cdebuhr

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The trouble with this concept, if I've read it correctly, is that it is incapable of producing sustained, net acceleration without violating the conservation of momentum.  At most, a spacecraft would wobble back and forth as the projectile was launched and then reeled back in.  You're using your magnetic projectile as a reaction mass (effectively a mass driver based propulsion scheme) ... but then you reel you're reaction mass back in, which would have the effect of exactly cancelling the momentum initially imparted to our putative spacecraft.  Virtually every known effective propulsion scheme (exc. light sails and mag-tethers, which aren't exactly in widespread use) involves some sort of reaction mass (gas from chemical rockets  or cold gas thrusters, plasma from ion drives) ejected in one direction which pushes the spacecraft in the other direction (Newton's third law).  But for this to work, you've got to let the reaction mass go ... you can't reel it back in, or you'll end up right where you started (in the spacecraft's initial inertial reference frame).

There are a few ideas floating around in the advanced propulsion concepts arena regarding potential reaction-less drive systems (EM drive, various space drive schemes, various schemes involving the manipulation of gravity, etc.), but these are still very much on the fringe and depend on new physical principals that may or may not actually have anything to do with reality.  Perhaps one of these will one day pan out, although the odds on this are likely quite long.  What none of these schemes do is try to re-use the same conventional reaction mass over and over - that clearly won't get you anywhere (unless you were already heading that way anyway!).

You also mentioned the possibility of generating net power from the winch motor/generator.  Unfortunately, this is also a non-starter, as you're violating conservation of energy.  If this worked, forget using it for propulsion ... you've made a working perpetual motion machine with a non-zero power output.  Your physics Nobel is on the way.  Hint: machines of this sort are forbidden by the laws of physics as we currently understand them.

Sorry!  Nice try though.

Offline Iggyz

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What is an "electromagnetic explosion"?
Nothing. All this concept seems to be is tossing something forward (with a poorly designed rail gun) attached to a tether and then pulling it back. It is entirely missing the "material from the nuclear explosion is expelled backwards" portion of a MEDUSA type nuclear propulsion. This concept would not work.

What is important is that the rail gun has hardly any or no recoil.

Offline Iggyz

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The trouble with this concept, if I've read it correctly, is that it is incapable of producing sustained, net acceleration without violating the conservation of momentum.  At most, a spacecraft would wobble back and forth as the projectile was launched and then reeled back in.  You're using your magnetic projectile as a reaction mass (effectively a mass driver based propulsion scheme) ... but then you reel you're reaction mass back in, which would have the effect of exactly cancelling the momentum initially imparted to our putative spacecraft.  Virtually every known effective propulsion scheme (exc. light sails and mag-tethers, which aren't exactly in widespread use) involves some sort of reaction mass (gas from chemical rockets  or cold gas thrusters, plasma from ion drives) ejected in one direction which pushes the spacecraft in the other direction (Newton's third law).  But for this to work, you've got to let the reaction mass go ... you can't reel it back in, or you'll end up right where you started (in the spacecraft's initial inertial reference frame).

There are a few ideas floating around in the advanced propulsion concepts arena regarding potential reaction-less drive systems (EM drive, various space drive schemes, various schemes involving the manipulation of gravity, etc.), but these are still very much on the fringe and depend on new physical principals that may or may not actually have anything to do with reality.  Perhaps one of these will one day pan out, although the odds on this are likely quite long.  What none of these schemes do is try to re-use the same conventional reaction mass over and over - that clearly won't get you anywhere (unless you were already heading that way anyway!).

You also mentioned the possibility of generating net power from the winch motor/generator.  Unfortunately, this is also a non-starter, as you're violating conservation of energy.  If this worked, forget using it for propulsion ... you've made a working perpetual motion machine with a non-zero power output.  Your physics Nobel is on the way.  Hint: machines of this sort are forbidden by the laws of physics as we currently understand them.

Sorry!  Nice try though.

This excerpt from Solem's paper might make it easier to understand his idea and my idea and why Solem thought he might be able to generate excess electricity. I have attached his paper.
"When the explosive is detonated, a motorgenerator powered winch will pay out line to the spinnaker at a rate programmed to provide a constant acceleration of the space capsule. The motorgenerator will provide electrical power during this phase of the cycle, which will be conveniently stored. After the space capsule has reached the same speed as the spinnaker, the motorgenerator will draw in the line, again at a rate programmed to provide a constant acceleration of the space capsule. The acceleration during the draw-in phase will be less than during the pay-out phase,which will give a net electrical energy gain.  The gain will provide electrical power for ancillary equipment in the space capsule. I have not yet worked out the details of this approach. I will reserve it for a future paper."

It is not a mass driver in the conventional sense because there is little or no recoil when the projectile propelled into space. The moment it is propelled it starts to pull at the cable that is rolled out by the winch at a programmed rate.

I don't think I will end up where I started. As Solem writes the spinnaker (projectile) is not drawn-in until spacecraft and spinnaker (projectile) have the same speed. So both will have traveled a distance before the draw-in phase starts. Basically the spacecraft and spinnaker (projectile) are pulling at each other because the spinnaker (projectile) has kinetic energy and still wants to go forward. Just because the winch on the spacecraft is pulling at the spinnaker (projectile) won't make the spacecraft and spinnaker projectile move backwards.



Offline cdebuhr

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What is an "electromagnetic explosion"?
Nothing. All this concept seems to be is tossing something forward (with a poorly designed rail gun) attached to a tether and then pulling it back. It is entirely missing the "material from the nuclear explosion is expelled backwards" portion of a MEDUSA type nuclear propulsion. This concept would not work.

What is important is that the rail gun has hardly any or no recoil.
The rail gun will have recoil.  That is completely non-negotiable, and how you're electromagnets are arranged will have no effect whatsoever on this.  This is a simple question of conservation of momentum.  If you can get around this, you're deep into very new, cutting edge physics concepts that may or may not match up with actual reality.  But your not going to get there with an electromagnetic rail-gun.




Offline Barrie

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What is an "electromagnetic explosion"?
Nothing. All this concept seems to be is tossing something forward (with a poorly designed rail gun) attached to a tether and then pulling it back. It is entirely missing the "material from the nuclear explosion is expelled backwards" portion of a MEDUSA type nuclear propulsion. This concept would not work.

Would it be fair to summarise it as 'propulsion by yoyo'?

Offline cdebuhr

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This excerpt from Solem's paper might make it easier to understand his idea and my idea and why Solem thought he might be able to generate excess electricity. I have attached his paper.
"When the explosive is detonated, a motorgenerator powered winch will pay out line to the spinnaker at a rate programmed to provide a constant acceleration of the space capsule. The motorgenerator will provide electrical power during this phase of the cycle, which will be conveniently stored. After the space capsule has reached the same speed as the spinnaker, the motorgenerator will draw in the line, again at a rate programmed to provide a constant acceleration of the space capsule. The acceleration during the draw-in phase will be less than during the pay-out phase,which will give a net electrical energy gain.  The gain will provide electrical power for ancillary equipment in the space capsule. I have not yet worked out the details of this approach. I will reserve it for a future paper."
The key difference you seem to be missing here is that the "spinnaker" is really just a sail catching the photon pressure and particle flux coming off the nuclear explosions detonating behind it.  It's not providing the reaction mass - that comes from the nuclear explosives, which are lost from the system allowing momentum to be conserved. 

It is not a mass driver in the conventional sense because there is little or no recoil when the projectile propelled into space. The moment it is propelled it starts to pull at the cable that is rolled out by the winch at a programmed rate.
See my previous post.  You don't get to fire projectiles in space without recoil.  Ever.  Not without "new physics".

I don't think I will end up where I started. As Solem writes the spinnaker (projectile) is not drawn-in until spacecraft and spinnaker (projectile) have the same speed. So both will have traveled a distance before the draw-in phase starts. Basically the spacecraft and spinnaker (projectile) are pulling at each other because the spinnaker (projectile) has kinetic energy and still wants to go forward. Just because the winch on the spacecraft is pulling at the spinnaker (projectile) won't make the spacecraft and spinnaker projectile move backwards.
I'm not going to give you an introductory physics course here, but it really all boils down to conservation of momentum.  It's not too hard to come up with radical new concepts when unbound by physics.  For example, long, long ago, I thought I could make a perpetual motion machine by using a small electric motor to turn a much larger generator to produce more power than the motor turning it required.  Simple!  Then I learned the relevant physics.  You clearly have an interest and enthusiasm for this stuff, which is commendable, but you're missing some pretty basic concepts.  Don't get me wrong here ... I love crazy ideas.  The vast majority of the time they're totally unworkable, but every once in a great while, someone comes up with something revolutionary.  But it helps a lot to learn enough of the basics (and then some) to evaluate new ideas as you come across them.

Offline Pete

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Great Idea.
You just have to repeal TWO of the laws of thermodynamics, also repeal one of Newton's laws of motion, and fiddle a bit with another of Newton's laws.

Easy!

Offline Iggyz

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What is an "electromagnetic explosion"?
Nothing. All this concept seems to be is tossing something forward (with a poorly designed rail gun) attached to a tether and then pulling it back. It is entirely missing the "material from the nuclear explosion is expelled backwards" portion of a MEDUSA type nuclear propulsion. This concept would not work.

What is important is that the rail gun has hardly any or no recoil.
The rail gun will have recoil.  That is completely non-negotiable, and how you're electromagnets are arranged will have no effect whatsoever on this.  This is a simple question of conservation of momentum.  If you can get around this, you're deep into very new, cutting edge physics concepts that may or may not match up with actual reality.  But your not going to get there with an electromagnetic rail-gun.
The attached picture might or might not convince you otherwise, but I think it shows how one can negate recoil and still let every action have an equal and opposite reaction.

Offline rakaydos

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What is an "electromagnetic explosion"?
Nothing. All this concept seems to be is tossing something forward (with a poorly designed rail gun) attached to a tether and then pulling it back. It is entirely missing the "material from the nuclear explosion is expelled backwards" portion of a MEDUSA type nuclear propulsion. This concept would not work.

What is important is that the rail gun has hardly any or no recoil.
The rail gun will have recoil.  That is completely non-negotiable, and how you're electromagnets are arranged will have no effect whatsoever on this.  This is a simple question of conservation of momentum.  If you can get around this, you're deep into very new, cutting edge physics concepts that may or may not match up with actual reality.  But your not going to get there with an electromagnetic rail-gun.
The attached picture might or might not convince you otherwise, but I think it shows how one can negate recoil and still let every action have an equal and opposite reaction.
the direction of the magnets does not matter. Every action has an equal reaction, even at a cosine.

Offline cdebuhr

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The attached picture might or might not convince you otherwise, but I think it shows how one can negate recoil and still let every action have an equal and opposite reaction.
It didn't, and it doesn't.  I don't know what else to tell you.  Like I said, I'm not offering introductory physics courses here.  You're missing so many of the basics of both mechanics and electromagnetics that you've got basically no hope of ever getting this thing to work.  Because it can't ... ever.  Doesn't matter how you arrange the magnets (or electromagnets), or what sort of suspensions you use, this thing just doesn't work.  Magnets just don't work that way. 

By all means, stay curious and enthusiastic about this stuff.  We need more people like that.  But there are nor shortcuts here when it comes to understanding the basics of the principals you're trying to apply.

Offline meberbs

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The attached picture might or might not convince you otherwise, but I think it shows how one can negate recoil and still let every action have an equal and opposite reaction.
No, it doesn't, it only shows a complete lack of understanding of Newton's laws.

The momentum (mass times velocity) indicated by the purple arrow is exactly equal, and in opposite direction to the total momentum in the black arrows. There is simply no such thing as a magic suspension system like in the 2nd picture, you simply ignore the downward force on it. In reality, the entire spacecraft is attached to the magnets one way or another, so there will be more mass, but less velocity, and mass times velocity will still equal the momentum of the projectile in magnitude. You have posted multiple ideas like this which violate simple physics for simple reasons. If you have an actual interest in physics, you are overdue to take an intro physics course, there are free resources available online.

Offline Iggyz

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Well you all are unanimous in saying it won't work. Am a bit disappointed of course, but I think learned something. I forgot to mention that the dual opposed magnets idea was inspired by the dual opposed pistons technology used in spring-piston air rifles, which seems to eliminate recoil and increase power.

Thank you all for your time, and apologies if I got on your nerves.

Whiscombe rifles and barrel harmonics – Part 1 Introduction | Air gun blog - Pyramyd Air Report - https://www.pyramydair.com/blog/2006/11/whiscombe-rifles-and-barrel-harmonics-part-1-introduction/

 

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