Is a Purely magnetic (NO CABLING) Space elevator possible?

[choff]

What would be nice would be if they could levitate the six coils of the Polywell into the cubic position and provide power to them without cabling, no more nubs and supports to worry about.

[alexjrgreen]

Drag losses are minor at 40,00 feet, for low Mach speeds, but not at sea level. Even at 40,000 feet the drag will melt aircraft wings at 3-4 Mach if given enough time.

Not sure where 40,000 feet came from. 40 km is over 130,000 feet - slightly lower than the Helium balloon that Google exec Alan Eustace parachuted from in October.

[hanelyp]

What would be nice would be if they could levitate the six coils of the Polywell into the cubic position and provide power to them without cabling, no more nubs and supports to worry about.

Reference the levitated dipole fusion reactor experiment, but with a more complex configuration. It would solve some of the problems with standoffs.

[Betruger]

Accelerate the vehicle from land. Perhaps ionize the air in front of the rocket to momentarily rarify the air to avoid heating of the rocket from drag. Just brain storming. Probably just too crazy.

The crazier the riddle...

[DeltaV]

What would be nice would be if they could levitate the six coils of the Polywell into the cubic position and provide power to them without cabling, no more nubs and supports to worry about.

Reference the levitated dipole fusion reactor experiment, but with a more complex configuration. It would solve some of the problems with standoffs.

Balance radially-outward wiffleball magnetic pressure on the coils with radially-inward electrostatic repulsion from special wall electrodes (or perhaps even direct converter electrodes)?

Pass one in freefall... g could be an issue.

[D Tibbets]

....
A rocket only spends a short time in the dense atmosphere and then it does not matter anymore.

A rocket, yes. It is at relative slow speed as it climbs out of the vast majority of the atmosphere, with most of the acceleration once it is out of the atmosphere. A gun, or magnetic rail is different . It has to obtain full speed by the time it exits the rail/ barrel. This is not a concern on the Moon or Ceres, and less of a concern on Mars because there is no or little atmosphere to deal with. On Earth it is a concern, though admittedly I may be exaggerating the problem.

Dan Tibbets

[JoeP]

Learn how to shield gravity (HG Wells) and the problem is solved. OK, not likely...fun story though.

A huge advance in materials science to make a cable practical will probably come before any kind of magnetic levitation technology that is strong enough and could be contained in a tight enough column as described. So I like the prospects of a real cable. For example, we have the recent various carbon fiber and nanotube material advancements that have revolutionized many industries; e.g. bicycle frames. Take it to the next level. Imagine if something like that could be made stronger by an order of magnitude by some sort of electrical/powered reinforcement or nano-machines that strengthens or reinforces the chemical bonds on a nearly molecular level? Like the materials used in the story Neutron Star by Larry Niven to construct nearly indestructible spacecraft hulls.

[AcesHigh]

....
A rocket only spends a short time in the dense atmosphere and then it does not matter anymore.

A rocket, yes. It is at relative slow speed as it climbs out of the vast majority of the atmosphere, with most of the acceleration once it is out of the atmosphere. A gun, or magnetic rail is different . It has to obtain full speed by the time it exits the rail/ barrel. This is not a concern on the Moon or Ceres, and less of a concern on Mars because there is no or little atmosphere to deal with. On Earth it is a concern, though admittedly I may be exaggerating the problem.

Dan Tibbets

however, because Mars has lower gravity, Mars atmosphere extends much farther than Earth. While at ground level Mars atmosphere is 600 pascals vs Earth's 101 THOUSAND pascals (0.6%), at the height of the Olympus Mons (28km) the atmosphere of Mars is already the same as Earth at 56km.

At orbital velocities, even those low pressures are already enough to create big shockwaves and attrict.

[D Tibbets]

....
A rocket only spends a short time in the dense atmosphere and then it does not matter anymore.

A rocket, yes. It is at relative slow speed as it climbs out of the vast majority of the atmosphere, with most of the acceleration once it is out of the atmosphere. A gun, or magnetic rail is different . It has to obtain full speed by the time it exits the rail/ barrel. This is not a concern on the Moon or Ceres, and less of a concern on Mars because there is no or little atmosphere to deal with. On Earth it is a concern, though admittedly I may be exaggerating the problem.

Dan Tibbets

however, because Mars has lower gravity, Mars atmosphere extends much farther than Earth. While at ground level Mars atmosphere is 600 pascals vs Earth's 101 THOUSAND pascals (0.6%), at the height of the Olympus Mons (28km) the atmosphere of Mars is already the same as Earth at 56km.

At orbital velocities, even those low pressures are already enough to create big shockwaves and attrict.

There is still atmosphere, but the heating will be less. Of course your final peak of the ballistic arc has to be at stable orbital height past all but the most very rare atmosphere. The fall of the ballistic arc is now equal to the fall of the horizon of the round planet/ moon, or round enough astereroid so that free fall is maintianed.

Dan Tibbets

[choff]

Another try would be a virtual polywell, six spheromaks arranged in a cube, using the 6 generated torus as magrids, no worries about first wall, the confinement is consumed in the reaction.

[DeltaV]

Another try would be a virtual polywell, six spheromaks arranged in a cube, using the 6 generated torus as magrids, no worries about first wall, the confinement is consumed in the reaction.

Simultaneously fire FRCs toward the center after injecting electrons through the corners of the polyhedron, followed by the ions after a transient wiffleball forms. Through the corners, unless a hollow FRC is possible. Sort of a blend of Polywell, Helion and General Fusion.

[D Tibbets]

Using an arrangement of spheromaks or rather tokamaks as the magrid might work, but only if you ignor the losses in these confining confiners. A copper electromagnet has losses, a tokamak or spheromak also has copper magnets with associated losses. Also the plasma confinement and energy confinement losses add to this. With super conductors the losses may be much less. But, you are multiplying several loss stages instead of only one. This is a losing proposition.

As for suspending the magnets, well and good, but you also have to actively cool them. Even with superconductors, you have to cool against incident heat from Bremsstruhlung and ExB diffusion. This can add up to 10s of MW of heating to the magrid. There has to be cooling plumbing, unless you some how keep the magnets cool by some radiative process. Even if the target is several 100 degrees C for a superb high temperature superconducter, the magrids would quickly exceed this temperature (and melt/ fail) before a radiation based cooling reached equilibrium. Either short pulses with long cooling periods between would be possible, and that is not very practical; or some form of super radiative cooling would be required. Conductive or convective cooling might keep up, but radiative cooling is much less profound, unless the temperature gradient is so great that black body radiation catches up and that would probably be at tens of thousands of degrees C.

Now, if you had some magical 99.9% efficient thermocouple cooling incorporated into the magrid with the resultant electricity feeding into the magnet power or being radiated off by magic high efficiency lasers......


Dan Tibbets

[krenshala]

Do you think thermo-electric conversion would provide enough oomph to run the required e-guns for the polywell?

[D Tibbets]

Do you think thermo-electric conversion would provide enough oomph to run the required e-guns for the polywell?

I don't know. From a "what if'''" perspective, I suppose you could assume this. One thing I did not mention about thermocouples is that, just like any heat transfer mechanism, there has to be a hot side and a cold side. So I'm not sure how it would be applied to an isolated hot source like a suspended magrid in vacuum. Current thermocouple efficiencies may have managed to pass ~ 5% efficiency recently. There is a long way to go before they can be used for anything more than marginal cooling or thermal energy to electrical energy conversion. In the Galleo prob to Jupiter, I think a radioactive thermal source was converted to electricity with thermocouples at perhaps ~ 2-3 percent efficiency. Six percent efficiency could have led to ~ 1/2 the radioactive element mass, smaller radiaters, less weight and still delivered more useful electricity. In this comparison small improvements are profound. Compared to steam conversion though, there is still a long way to go before thermocouples can be applied as the primary conversion scheme, except for special situations like interstellar probes. Even there, a Sterling engine would have been better, but apparently not chosen for other reasons. Also, Solar panels, with evolving improvements, can be used at greater distances from the Sun.

Note that the Galleo prob was in a vacuum and 'suspended' like an isolated magrid. The difference is that only a ~ KW of heat had to be disposed of through a relatively large radiator. Compare this to a Magrid where MW of heat would have to be disposed of and/ or converted to useful electricity.

Dan Tibbets

[choff]

I think it's the LPP fofu plasma's that have the electron beam out one axis, would save on e guns for a virtual polywell made from six of them. Losses could be plugged by firing additional toroidal plasmas directly into the cusps. Just a fun experiment if tok funding ever got transferred to iec, may be needed if nubs are a show stopper.