Talk:Mini-magnetospheric plasma propulsion
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Some explanation of the specific impulse claim would be nice. The system seems to need no reaction mass (and in fact the article says this) but a specific impulse is given. It looks like what's actually going on is that arcs need to be extended to collect thrust, the bigger the more thrust; these arcs leak ions, the bigger the more. Taking the ratio gives a sort of specific impulse, namely ion leakage per Newton of thrust. Is this correct? It should be explained. Andrew 06:25, Apr 13, 2004 (UTC)
Also, can the direction be controlled? The solar wind streams only directly away from the Sun, but since it's charged it may be possible for the system to redirect it, allowing tacking. Andrew 06:25, Apr 13, 2004 (UTC)
This turns out to be possible; in fact, this propulsion system is simply a way of making a magnetic sail out of loose ions instead of wire. --Andrew 06:39, Apr 23, 2004 (UTC)
I'm skeptical of the claim that these systems produce the same thrust throughout the heliopause. ~Can we assume half acceleration = thrust beyond the heliopause/My guess is the ions are less numerous in semi radom directions, but much faster beyond the heliopause.~ If the power for the system comes from solar panels, then that power will fall with the square of the distance from the sun. Thus, you either need very large solar panels as you recede from the sun, or else your propulsion system's effectiveness is diminished.
~the pressure of the magnetic feild and the solar wind are in dynamic equalbrium. As the pressure of the solar wind falls of at 1/r^2, the field increses in cross sectional radius, maintaing constat force.
Any comments? --P3d0 16:33, 4 May 2004 (UTC) IMHO solar panels are useless just inside the heliopause, but it may take a hundred years to reach the heliopause. A space craft designed for 100 years will have several electric power sources, most of which will have failed, so the choice may be propulsion or transmitting data back to Earth, if either propulsion, or transmitting are still functional.
~it would take 10 years to get to the heliopause at 50 km/s and m2p2 is expected to run between 50 and 80 km/s.
- If the power comes from solar power, then you're right (outside a certain distance). But the statement is for a constant power; perhaps this is generated by a nuclear reactor, or perhaps there is sufficient solar cell area to accomodate the propulsion system at any distance of interest.
- It would be nice to have some estimate of the amount of power needed to run such a system (both for this and for magsails). --Andrew 22:10, May 4, 2004 (UTC) The super conducting magsail needs considerable = gigawatt-hours of energy to establish the magnetic field; negligible energy to maintain the magnetic field, however there may be reasons why we would want to shut down the magnetic field. It might be practical to store half of the energy stored in the magnetic field for other uses. Can someone explain where the other half is disapated? It occurs to me that it may difficult to shutdown (non-distructively) a magnetic field in space that is produced by a super conducting loop.
In any case re-activating the super conductive magnetic field requires considerable energy.
~there is no superconducting loop anywhere in this system.
If there are fewer ions, the magnetic field increases in size until a certain amount of ions start hitting it. Therefore, even if there are fewer ions it will maintain it's speed. Another interesting point that someone might want to add is that if heading towards a star, it would act as a brake, and would bring it back down and stop it at a distance where the force of gravity equals the force that the engine can handle.
~If anybody would like further reading the Journal of Geophysical Research, vol 105, NO. A9, pages 21,067-21,077, september 1, 2000 has an easy to read paper by the creators of this technology.
