Ultrahigh Acceleration Neutral Particle Beam-Driven Sails | Hacker News Reader

Ultrahigh Acceleration Neutral Particle Beam-Driven Sails

centauri-dreams.org

40 pointselorant10 comments

A 260-meter diameter magnetic sail weighing only 1kg would be quite fantastic to see. I wonder if something based on carbon tubes could withstand 100,000g. Acceleration at such levels would turn conventional metals liquid immediately.

Dumb question: how do you couple to a beam of neutral particles?

From the article:

> The rapidly moving magnetic field of the Magsail, seen in the frame of the beam as an electric field, ionizes the incoming neutral beam particles. Nordley and Crowl discuss on-board lasers to ionize the incoming beam, although this adds additional on-board mass and power

I like this idea. I was wondering if it would be possible to collect and focus solar wind close to the sun and use it as a high concentration beam.

Was also wondering if you could use the various gyroradii and charge of solar wind particles to “sort” them.

I believe plasma physics is hard

No. Any structure that could do that would itself be pushed by the wind. The energy/fuel needed for station keeping the focus unit would be better spent on the actual spacecraft ... unless you want some megastructure (ring) that wouldnt need fuel for station keeping.

Shouldn't there be some sort of "lagrange-like" point where the sun's gravitational pull balances out the push of the solar wind?

Not sure if such a balance exists for external bodies but there does exist a limit very similar that constrains the maximum size of a star [1].

[1]: https://en.wikipedia.org/wiki/Eddington_luminosity

No, or at least not any stable such point, because the solar wind is not constant. Plus it is orders of magnitude less powerful than the sun's gravity. It's only usable (in theory) for navigation because any ship is already in orbit around the sun and doesn't need to "cancel out" gravity in the sense that wings provide lift to an airplane or a rocket achieves orbit from the ground, but rather it needs to be able to gently and continuously nudge itself into higher or lower orbits.

The fast ion loss probe used in fusion energy research is relevant to your last point. See figure 1 of [1], or if you have access see [2] for a good explanation.

[1] https://w3.pppl.gov/~szweben/Papers/coauthorpapers/DarrowRSI...

[2] https://aip.scitation.org/doi/pdf/10.1063/1.5039311

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