Jeff Greason proposes extending power beaming using the magnetic pinch phenomenon. The quasar 3C273 produces a plasma jet that is 100,000 light years long. This distance would span the Milky Way. It may be possible for humans to produce pinched relativistic electron jets over the much smaller distances needed to propel a spacecraft out of the Solar System. Charged beams in a low-density plasma can confine themselves over long distances. The beams carrying a current creates a circular axial magnetic field which in turn confines the beam. Pinching is a means of self-confinement of the beam that has been studied since the 1930s. A pinch forming a jet explains why solar proton events can strike the Earth despite the 1 AU distance, and why galaxy-spanning jets like that in the image above can form.
Centauri Dreams described Greason’s proposal.
The extended beam could strike a plasma-filled waveguide which can couple to backwards plasma wave modes. This effect would launch plasma in the opposite direction as reaction mass. This keys to existing work on plasma accelerators (so-called “wakefield” accelerators), which use similar physics. We would need experiments to explore how much beamed energy can be returned in this way.
If we can increase the range of a beam from 0.1 AU to 1000 AU, this means we could send much larger spacecraft. The spacecraft could be 100,000 times larger, at the same power levels. The one gram-sized spacecraft proposed by Breakthrough Starshot’s laser methods could become 10 kilograms. The acceleration time from minutes to months. That increased payload size is particularly useful when it allows a braking system aboard for long-term study of the target.
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This is what LPPfusion does for their fusion reactor
On a different (or maybe the same) angle as Brett, I think that a charged particle beam — be the particles electrons, or protons, or various nucleons — will inherently have realtime insidious instabilities that scale with the length of the beam.
The Earth is bathed every second of the day in a vast, chaotic Solar Wind. Itself a big ol’ charged particle(s) plasma gas phenomenon. That SW wiggles all over the place, and inasmuch as I’ve read and researched, apparently neatly unpredictably in detail. Generally (like predicting where the Earth’s jet stream will go in the next hour or two), the Solar Wind CAN be predicted with some general fidelity. But over days, weeks? Not a chance.
And the point there is one of scale fidelity. Say you’re trying — to use this article’s numbers — to direct your particle beam at a receding spacecraft whizzing off some direction or another which is 100 meters across (pretty big, but not huge) and ‘just’ 10 AU away (or about 1,500,000,000,000 meters distant), you’re trying to ‘aim’ at the spacecraft with an angular precision that is mind-bogglingly accurate … in a Solar Wind field that is maddenly chaotic and changing every second as well. Good luck!
It might seem hyperbole to envision this example, but imagine trying to hit a FLY with a rifle bullet, at the other end of a long beach, in the middle of a windstorm. Even if your rifle is on a computer controlled hyper-accurate targeting stand, one simply cannot know WHAT winds are between you and the fly 5 kilometers distant, in that windstorm.
0.5 cm fly, 5 km distant … the angular ‘extent’ is 1 µrad. By comparison, the spacecraft at 10 AU is 6.67×10⁻¹¹ radians, or 15,000 TIMES smaller in angular extent. Requiring beam aiming accuracy 15,000 times better than the rifleman and his targeted fly.
Anyway, beams and spacecraft. Very good ideas, minus the problems with them.
But the same might be said of most any popular idea, neh? Fusion is awesome minus the fact that it hasn’t been harnessed productively (yet). Solar power is magnificent except when the weather’s bad, or at night, or seasonally, or when the panels get dirty, or when a passing hailstorm breaks a whole field of them. And hurricanes are bad too. Tornadoes. Copper thieves are worse than ravens. Shall we go on?
Lovely to talk about the beams though.
Good Science Fiction stuff.
⋅-⋅-⋅ Just saying, ⋅-⋅-⋅
⋅-=≡ GoatGuy ✓ ≡=-⋅
Tiny target indeed!
Needs to be more a moth than a fly.
Maybe by having, say, four coils arranged around the craft, each producing a field, the craft could detect the drift of the beam.
If the beam goes off center, it will impose on the field of that sides coil, and the craft can respond by inflating that field, re-centering the craft.
A moth to a flame.
Perhaps the coils can be powered mostly by tapping into the beams charge.
Charged particle beams are certainly unstable. Neutral particle beams and photon beams, in a vacuum, not so much.
What do we need here?
1. Beam must carry momentum.
2. Must be able to transfer that momentum to craft.
3. Must be able to efficiently generate the beam.
4. Has to remain in focus for an extremely long distance.
5. Has to have pointing stability comparable to beam diameter at that distance.
Light carries momentum, and can transfer that momentum, and can be generated efficiently. In principle it could, with a large enough aperture, remain in focus across astronomical distances, and retain pointing stability if you used a remote phase reference. But the ratio of momentum to energy is very low, so it’s not actually an efficient way to deliver momentum. And “in principle” is doing a lot of work here, the phase control needed is literally astronomically precise. Might even be precluded by inherent quantum noise…
Charged particle beams are really good at carrying momentum, transferring it, and can be generated efficiently, but suffer badly on remaining in focus and probably pointing stability. I don’t think that’s curable.
Neutral particle beams are good at carrying momentum, decent at transferring it, and decent at efficiency. Retaining focus is challenging, as is pointing stability.
I like the combination of a neutral particle beam and a photon beam, as has been proposed before, because each can focus the other, and the difference in velocity should stabilize the beam and enhance pointing stability. But there may be hidden instabilities lurking there. Worth doing some real world testing.
A couple suggestions:
You could use a neutral particle beam, and space along the beam focusing stations, using photon cooling to progressively zero out the lateral component of the particle velocity while correcting beam drift and focus. Effectively they would add huge angular inertia to the beam, so pointing stability would be good, and the beam would be passing through a hole in the station, which a craft could also pass through. In theory if you got the lateral velocity low enough, it would gravitationally self-focus.
Another possibility is to use really large “particles”, capable of course correction; Maybe Starshot sails, or tiny craft launched from a REALLY long mass driver. Basically Orion that doesn’t have to carry bombs. Or only carries them for the deceleration phase of the trip, anyway…
Any way you do this, the infrastructure demands are enormous, of course. Which is why I’m continually harping on the need to develop self reproducing factories. It’s the only way we’re going to become wealthy enough to afford manned interstellar travel, given current physics knowledge of course. It WOULD be nice to find a quark nugget out in the asteroid belt…
I think the earlier proposal to combine a neutral particle beam and an EM beam, which would focus each other, has more promise. Because the particles and photons have different velocities, you get shear stabilization and enhanced pointing stability.
Charged particle beams have a tendency towards what’s known as “sausage” instabilities, which I guess is easy to envision. It’s a common problem with Z-pinch fusion reactors, same phenomenon.
And how do you stabilize it against that? Shear.