Converting Solar Wind and Interstellar Plasma Drag into Propulsion

The Plasma Magnet work sponsored by NIAC in 2004-2005 developed a means of producing drag against the interplanetary solar wind or interstellar medium with high drag-to-mass ratio.

A new class of reaction drive is discussed, in which reaction mass is expelled from a vehicle using power extracted from the relative motion of the vehicle and the surrounding medium, such as the solar wind. The physics of this type of drive are reviewed and shown to permit high-velocity

changes with modest mass ratio while conserving energy and momentum according to well-established physical principles. A comparison to past propulsion methods and propulsion classification studies suggests new mission possibilities for this type of drive. An example of how this principle might be embodied in hardware suggests accelerations sufficient for outer solar system missions, with shorter trip times and lower mass ratios than chemical rockets.

A detailed design would be required to estimate mass but a sizing study, based on peak currents in superconducting MgB2 tapes at 20K of 2.5 x108 A/m2, suggests that accelerations in the 0.025-0.05 m/s2 range may be feasible using this approach. The long tether, carrying oscillating currents in the 1 kHz range from end to end, modulated by a reciprocating frequency in the 20 Hz range, is admirably suited to form a Wideröe style ion accelerator, thus providing an integrated method for converting the resulting electric power to thrust.

SOURCES- Tau Zero Foundation, Interstellar Research Group
Written by Brian Wang,

35 thoughts on “Converting Solar Wind and Interstellar Plasma Drag into Propulsion”

  1. Robert Zubrin discussed this years ago in a book. He demonstrated that a magsail would be very performant around the solar system, being able to beat any conventional propellant. It is limited for interstellar travel. However, if you want to stop at a star of your choice, then you can use a magsail to brake from any velocity.

    That solves half the delta V problem. One attractive concept is to use a laser pushed light sail to accelerate to high speed, but the method for slowing – turning the sale into a reflector onto a smaller sail is cumbersome. So the magsail provides a neeat way to brake.

  2. Not quite right. In orbit around the sun, you have the gravitational gradient, and the solar wind. To "tack" all the spacecraft has to do is slow it's orbital speed, and it falls in towards the sunA.

  3. Yep, any telescope exactly or near 542 AU will have strong noise problems with the solar photosphere and corona, probably being unusable.

    For these telescopes, the farther, the better.

  4. Yep, there is plenty to do in space near Earth or on the Moon.

    Space telescopes (maybe some land-based ones, stretching their capabilities) will bring us the first legit Earth-like planet pictures (even if pixel sized).

    Then, after having some actual inventory of nearby Earth-like planets, we will have targets of interest for a Solar Gravity Lens mission, which will be very high cost. Assuming we have the tech to do it!

  5. It's the farthest planet, and one we don't have quick ways to take something there.

    And as others said, Pluto got demoted and would be a tough sell for another mission anytime soon.

  6. Cool presentation.

    And a big result, if they show they can continue increasing speed in exchange of momentum after all real world losses are factored in. A working model on the solar system would be more than worth the try.

    And it could end up being in the same league as the invention of the rocket equation and Goddard's work on rockets.

    Because with this, interstellar travel would be solved once someone produces a way to gain enough momentum with a sizable mass (the ship and its propellant). At least for probes with an useful payload.

    And as the presenter say: there are envisageable ways to move a spaceship at about 3-6% c.

  7. If we've going on about wind travel analogies, you do have wind turbine powered vehicles going directly upwind, wind turbine vehicles going faster than the wind going dead downwind (yes you read that right, a lot of people thought that was a scam but it was proven), and potentially going faster than sailboats when going orthogonal to the wind (depends on how apparent wind plays out). This has interesting implications, as you want to provide propulsive force orthogonal to the solar wind, along the tangent of the orbit.

    Which reminded me of a recent conversation regarding counterrotating heligyros around a central hub, operating similarly to a wind turbine…

  8. It was Pluto until recently, of course. Neptune is ironically used both for an example of how unimaginably large the distance to it is, the scale of the solar system, and as a scale reference. While it seems cruel to demote Pluto from planethood, it turns out that Pluto is the brave interloper from a much larger group of objects. The first!

  9. Throwing this out there:

    It would be neat to use the Xenon byproducts of the fission reactor as reaction mass for the particle accelerator. Get rid of the neutron poison by using it as propellant.

  10. "standard stuff we do now", that is, big Keck type stuff, radio and optical interferometry. Not using the Sun as the lens, just really big standard stuff we do now.

  11. 542 AU is the radius to Sol's focal point. Neptune's orbital radius is a bit more than 30AU.
    Presumably, you'd want your observatory a bit past the focal point.

  12. Observatories on the moon would identify candidates for full time GL observatories. You would certainly want to deploy for the most interesting targets. Lunar, and GL observatories do not compete, they complement each other.
    A GLO could presumably image objects within something of similar size to our solar system. Likely, the observatory would have a larger node for communication with Terra, and smaller imaging nodes that would move around to image planets, or whatever else piques our attention within the system. It would be interesting to image individual objects in distant galaxies, other than supernovas. In particular galaxies with energetic centers would be good targets. It would be nice to see exactly what produces those beams.
    I assume GL works both ways, so it would be the perfect way to communicate with an interstellar probe, whether on the way, at the target, or after flyby, whether communication is by radio, microwave, or optical frequencies. It would enable continuous communication at higher bandwidth, or lower transmission power than anything else I can think of. Mass of transmitter, and energy to run it will be at a premium in any conceivable interstellar probe.
    Gain is good, giga-Gain is fabulous!
    If we do find an extra solar entity able to communicate with us, or just doing "local" broadcasts, like we do, this would be the technique of choice to get enough data to understand transmissions.

  13. Here's the thing: In sailing, you have two media, wind AND water, and both of them can be induced to allow motion in one direction, AND resist it in another. The ship with a keel moves very easily through the water in the direction it's pointed, resists perpendicular movement. The air similarly responds to the sail.

    This allows you to extract energy without expending mass, and even to travel faster than either medium. In theory, were it not for friction, you could accelerate almost endlessly.

    The sailplane can travel endlessly, even extract energy, so long as the wind is going UP. But it can't gain altitude faster than the wind, its direction of travel is quite restricted.

    Gravity plus solar wind IS like the sailplane, allows you to do orbital maneuvers, but gravity doesn't care which way you're going, there's no gravity keel. So you can't ever get going faster than the wind, and your choice of directions to thrust is limited.

  14. Still doesn't let you exceed the speed of the solar wind, let alone accelerate while traveling in the same direction.

    OK, looking at it closer, my reasoning applies to systems that don't throw away mass. This one does.

    Basically what is going on here is that you're taking some of the mass you carried along, having it interact with the solar wind to slow down without drag on the *rest* of your ship, this generates energy that you use to throw away still more mass to produce thrust.

    Physically, THAT can work. Until you run out of mass to throw away, anyway.

  15. Well, you would go back and forth, but that is slower than straight ahead. Tacking in the water has both wind, water and the keel to work with. The two hardest things about computer programming are naming, casting, and index off by one problems.

  16. You don't need two media, you just need two opposing forces. Think of a sailplane, flying through a current of rising air. It is immersed in only one medium. As long as the force of the rising air is enough to oppose the force of gravity, then the sailplane will maintain altitude. The wing doesn't just oppose gravity, it also generates a small forward vector by deflecting the rising air backwards. This forward vector is enough to counter aerodynamic drag, so the sailplane can maintain speed and altitude.
    Now let give our sailplane magnetic wings, and throw it into outer space. Substitute the solar wind for the rising air current. At the Earth's orbital distance, the force of solar gravity is pretty darn small. But a well designed solar 'sailplane' should be able to maintain radial distance from the Sun (altitude), and generate a very small forward thrust (orbital velocity). In some directions, you might be able to substitute the opposing inertia force of the sailplane for the force of gravity.
    Whether or not this would be practical is a different question.

  17. I am a bit fuzzy on the dynamics, but it seems to me that you could use the inertia of the spacecraft as the opposing force, and allow limited 'tacking' across the solar wind. This would work as long as the solar wind speed was much lower than the spacecraft velocity.

  18. 10x beyond Neptune x2 for baseline standard stuff we do now should be quite nice. Unlimited optical bench.

  19. Really only if you have a specific target to look at. Once there it is hard to reposition to view another star.

    While gravitational lensing telescopes sound amazing I suspect that we can do much better once we industrialize outer space and the moon.

  20. Inaccurate, too.

    The reason a sailing ship can actually exceed wind speed moving across, not with, the wind, is that it has access to TWO media, the air AND the water, which are moving relative to each other.

    In space you've only got the one medium, so you can't do that.

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