Re:An Alfvenic reconnecting plasmoid thruster
by Gravityloss on Tuesday July 13, 2021 @03:12AM
(#27818319)
The power source has been the big limiting factor in electric propulsion. If your exhaust velocity is several times the mission delta vee, your propellant amount becomes really small. But your power source is probably going to be big. If you use a lower exhaust velocity, you need more reaction mass, yes, but you need less power also. This might in aggregate be better!
Ie, higher exhaust velocity can result in worse performance.
It all depends on your power source, mission delta vee and required acceleration.
«Because the system-size plasmoid is an Alfvenic outflow from the reconnection site, its thrust is proportional to the square of the magnetic field strength and does not ideally depend on the mass of the ion species of the plasma.»
[Edit: a bit more detail] The exhaust velocities are 20 to 500 km/s, the plasma is relatively low-temperature and density, the exhaust speed depends on the magnetic field (B^2). A device a couple meters long is predicted to produce thrust up to 100N with 10MW of electric power. All this with lightweight ions to conserve both energy and mass. (To compare, current best ion drives produce exhaust at 20-50 km/s only with heavy ions, with thrust well below 1N.)
If this works, this is a big deal. Even if it does not completely remove the tyranny of the rocket equation, it may greatly alleviate its influence. It might allow to quickly move around the Solar system using moderate amounts of reaction mass, provided that a powerful enough nuclear electric plant can fit on board.
This of course isn't going to work for liftoff from Earth or Mars, but alternative mass orbital transit solutions exist at least in theory (space elevator), while there were no alternatives for proper space travel.