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Space Planes
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MirariNefas
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PostPosted: Tue Aug 14, 2007 9:45 pm 
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I was actually think of microwave beams from orbital solar power stations - and possibly only coming into play after a space plane has delivered the craft to 20km.


So, we're talking about fantastically expensive infrastructure that only allows some benefit after the heavy lifting has already been accomplished and paid for elsewhere. I'm not sure I see the benefit.

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Couldn't multiple beams be focussed from one parabolic reflector?


For a target that is not a fixed distance from the reflector? No. And if we need a long wavelength (I'm not sure how high up you'll need to go to use really short ones) the focal point will still be huge.
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Doesn't it make a difference if there are two magnets - one say like a disc, the other like a life saver around the disc and they extend at different times, in rythmn?


It'll just extend and contract without moving.

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I thought if the electricity input was powerful enough to drive a powerful motor that the magnetised disc or ring would be powerful enough to pull things with a larger mass.


And pull itself to the larger mass. The strength of the motor determines the overall force of attraction, which will be evenly distributed between the two bodies. When the force is distributed across a smaller mass, that mass will move more than the larger mass - they will both contract towards the center, but the smaller one more than the larger one. And of course, when you make them extend again, all that effort will be for nothing.

The kind of motion you are describing is essentially impossible, pushing off of nothing.
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louis
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PostPosted: Wed Aug 15, 2007 4:28 am 
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Mirari -

I wasn't taking this too seriously so cost wasn't much of a concern! Just wondered whether it was technically feasible.

OK - here's a different approach...

What if the craft has extendable rods which have ratchets on them. Leaving aside the problem of how much power we can get from this, couldn't the craft "climb" the ratchets. And we could alternate between two sets of rods.

Maybe to make it more efficient it could be some sort of vacuum system - so the electricity creates some vaccuum in the rods which the space craft, with a rod insertm, then moves into, to fill the vacuum. And so it goes on quickly alternating between two sets of rods and the spacecraft always moving forward to fill the vacuum. .

Surely suction doesn't lead to motion in both directions does it?

Is that any better?

I promise it's my last tom fool idea for today.
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MirariNefas
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PostPosted: Wed Aug 15, 2007 11:06 am 
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Move into a vacuum? It's already in space. That's a vacuum.

Anyway, vacuums don't suck. It's the pressure behind an object that pushes it into a vacuum.

Look, I'm going to flat out say that anything of this nature is impossible. When you're ratcheting an object in front of the craft, or using vacuum pumps to retrieve air from a pressurized area, you'll be causing the opposite motion to what you desire. You'd have a system that moves part of the craft, but in setting up again for the next move, pushes it back into its original position.

Keep in mind that every action has an equal but opposite reaction. What we need to do is separate that reaction from the ship - meaning that it must interact with something that it doesn't bring with it. Either that's venting propellant, being pushed by a laser, or pushing off a planetary magnetic field, but it can't push off itself and keep that part for another go.
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PostPosted: Wed Aug 15, 2007 11:56 am 
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A SSTO Reusable Launch Vehicle has been discussed at length by engineers over at the NASA spaceflight forum:

http: forum nasaspaceflight com forums thread-view asp?tid=1184&posts=307&start=1

Apparently the US was well on its way to designing one but it was canceled when the new administration took office in 2001.
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louis
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PostPosted: Wed Aug 15, 2007 5:39 pm 
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http: science howstuffworks com electromagnetic-propulsion1 htm

Mirari - The above link does suggest that some scientists think that magnetic propulsion is a possibility, though I don't really understand the process described.
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MirariNefas
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PostPosted: Wed Aug 15, 2007 9:01 pm 
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I've heard of this. And you'll also notice that they are very uncertain that such a thing could actually work. And I think that's the point - the experts think that such a thing might be possible with an exotic and high energy set up. Leave the unconventional to the professionals, because they're the only ones who understand the rules well enough to break or bend them.
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PostPosted: Thu Aug 16, 2007 2:17 am 
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louis wrote:
http://science.howstuffworks.com/electromagnetic-propulsion1.htm


The idea of electromagnetically "rectifying" an oscillatory motion is intriguing, but every description I've seen of Goodwin's scheme, or any of the electromagnetic inertia modification schemes for that matter, ends up requiring non-standard physics or having the same basic problem as the ideas you posted earlier.

For example, the howstuffworks article says the asymmetry-causing (i.e., rectifying) plate is going to be charged and drained in the presence of this huge magnetic field, but no mention is made about the forces (and thus motion) associated with that. 1 gets you 10 that any net motion resulting from rectifying the oscillatory motion during power-up of the electromagnet will be exactly canceled when you decharge the plate for the electromagnet power-down.

Check out his testing plan ...

Goodwin, A Propellantless Propulsion Experiment Design and Testing Plan, 2004
http: adsabs harvard edu abs 2004AIPC 699 1175G

Goodwin wrote:
1. Confirm uni-directional motion (net external force) is produced (e.g., not limited to oscillations).

2. Confirm momentum is conserved without pushing off or pulling toward other objects


Those are some pretty significant checkboxes.
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louis
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PostPosted: Thu Aug 16, 2007 4:16 am 
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Yes - that's an "if" wearing maybe boots and a suit of assumption.

Still - intriguing.
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louis
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PostPosted: Thu Aug 16, 2007 9:49 am 
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A further thought:

If the problem is to ensure that the force goes on way and another way, as with a rocket...

Is there anyway you could have a situation where the attracting electro- magnet was being fed by an orbital power station but the equal and opposite reaction force was being converted into electric power which was somehow captured by a ground station beam or otherwise dispersed ? Wouldn't that leave the craft free to be attracted toward the extended magnet?
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MirariNefas
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PostPosted: Thu Aug 16, 2007 4:11 pm 
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Wouldn't that leave the craft free to be attracted toward the extended magnet?


The craft is always free to move towards a magnet, the problem is only that the magnet is pulled towards the craft as well. And as long as the two objects are attached, the kinetic energy cancels. So what you're saying is that you want one end to be attracted to the other, but the other to generate a current instead of experiencing an equal attraction? I don't think that's possible. As long as one end is attracted to the other, there must be a magnetic field for both. When two objects have magnetic fields, they both experience kinetic attraction, and, in a free situation, movement. When they move you can generate a current, but that current itself produces a magnetic field and decreases the moving force. This would apply to both sides equally. I'm just not sure I can imagine how such a situation world work.

Of course, you can always dump energy by firing a beam down to a ground station. That's essentially like having a rocket made out of a laser. There wouldn't be any need for magnetics in such a situation though. A proposal that I've heard before is that rather than the craft or the station firing a laser into a receiver and having it end there, you set up a mirror between the two objects. That way, the laser continuously shines back and forth between the two, gradually accelerating them. In reality the angle of refraction wouldn't be perfect and you'd lose the initial round of photons after awhile, but with precision engineering and a wavelength that penetrates atmosphere well, you might get quite a bit of work out of it.
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louis
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PostPosted: Thu Aug 16, 2007 7:10 pm 
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Thanks for the clarification - very useful.
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Fridamimi
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PostPosted: Sun Nov 20, 2016 8:13 pm 
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He said several things.....definitely as he was getting closer to kicking the bucket. What the #%&@ was the government going to do to him for speaking out....kill him??
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