This seemed like the appropriate place to share my crazy-far-out vision for the future of space travel.

If you’ve looked at my SMAP proposal, or really any of my other posts on this forum, you’ll know I’m very enthusiastic about a propulsion technology called the plasma magnet sail, which is a magnetic sail design that in theory has a ridiculously high thrust to weight ratio, so much so that a high-performance spacecraft could use the solar wind to accelerate up to a terminal velocity of 300-800 km/s in a few days. This is very useful if you want to travel away from the sun, but the problem is stopping at your designation. There are a few ways of slowing down using the magnetospheres or atmospheres of planets, or using conventional propulsion, but none will work at hundreds of kilometers per second.

The answer is the magnetized plasma beam (Magbeam), developed by Robert Winglee report here. This is a self-focusing plasma beam produced by a helicon plasma source. Its range is not great in Earth’s magnetosphere, but in the solar wind, its expansion is diffusion-limited. A Magbeam could likely connect with a large dipole magnetic field like that generated by a plasma magnet at a distance of an AU or more. If it was using hydrogen (which is far from ideal), a Magbeam with an average ion energy of 10ev would need to have a beam power of about 200 megawatts to slow down a 100 ton spacecraft traveling at 450 km/s over a distance of less than an AU. The beam would need to fire continuously for about a week, expending 277 tons of hydrogen. Building a helicon system at this power level would be a massive engineering challenge, but I don’t see any physics limitations that would prevent it from being scaled up this far. A station like this would need a power supply on the order of a gigawatt, and probably be built into a small icy moon or asteroid to use as a heat sink and source of hydrogen.

A network of these stations across the solar system would allow travel to the outer planets on timescales of a few months, but only when the orbits of the origin and designation planets line up so that the route of travel is directly away from the sun. However, by dialing up the ion energy to 20ev, the Magbeam station could boost a stationary spacecraft to a speed of around 50 km/s in any direction. This is nowhere near solar wind speed, but still fast enough to cover an AU of distance in about a month.

Relatively simple and inexpensive spacecraft could travel between any two of these stations on timescales of weeks in the inner solar system and a few years in the outer solar system. This would allow large numbers of colonists to immigrate to established settlements in space, even ones in the outer solar system. It could also allow significant 2-way trade between colonies, maybe even to the point that their economies could specialize.