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I'm curious about the way the laser beam seems to curve inwards near the start of the particle beam. Is this a focusing effect?
![[Image: limbach_2018_phi.png]](https://www.nasa.gov/sites/default/files/thumbnails/image/limbach_2018_phi.png)
It reminds me slightly of the ray emitted by the Death Star, which always struck me as unphysical.
![[Image: O8AShm.png]](https://i.stack.imgur.com/O8AShm.png)
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Jordin Kare's Sailbeam proposal uses light sails accelerated by lasers as a kind of particle beam to transmit momentum; these can (in theory) be redirected to improve collimation.
The 'smart pellets' used by OA's Beamriders are also capable of 'homing in' onto the target spacecraft, but the details of this process are somewhat beyond predictable technology.
The 'PROCSIMA' waveguide concept might be an early version of this kind of tech, assuming it works.
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So if we can use these to accelerate a 1kg probe to 0.1c, then we could use a thousand of them to send a one tonne probe. A million of them would send a probe massing a thousand tonnes - maybe enough to decelerate into orbit around another star. They don't need to be accelerated in one big mass - the probes could assemble on route, like Legos.
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Final thought- this PROCSIMA laser/particle beam hybrid would make a good long-distance weapon.
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It might also be useful to add that any particle beam with decent range would have to incorporate an opposite-charge injector very near the main output; probably, in most cases, electrons being mixed with a positive-particle beam. Why? Because otherwise there would also be electrostatic mutual repulsion between beam particles to contend with, causing extremely severe beam spreading.
At any reasonable range from the device's output, the beam itself would probably have become a beam of atoms or molecules.
One more thing: Diffraction becomes less severe as the mass of the beam particles goes up. This might be thought to indicate that a beam of lead might be best, but on the other hand momentum transfer might be inhibited then as the spacecraft structure would likely be made of light elements. (Momentum transfer is most efficient when the particles colliding are of equal mass.)
For a spacecraft made of diamondoid, graphene and/or buckyfibres, this means a beam of carbon atoms - or maybe a beam of methane would be easier to deal with at the emitter. (Methane is easier to handle than gaseous carbon.)
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Agreed re the unphysical bit about the Death Star. I suspect the graphic is employing some artistic license re the laser beam. In a real system, I would suggest that the laser would consist of some kind of phased array - so a laser emitter as a disk with lots of lasing elements along its surface.
Re the smart pellets used by OA beamrides - G. David Nordley - who came up with our general style of beamrider - has a fairly detailed description of the smart dust in the article I have, including a very nice graphic. They are relatively straightforward devices, although they would almost certainly require middling advanced nanotech to manufacture complex (but tiny) devices in vast amounts. I've been toying with an update of the beamrider network article for some time to make it more our own (it currently owes a lot to the novel Permanence by Karl Schroeder, which originally inspired the addition of the BN to the setting). As part of that, I could include a more detailed description of how the smart dust works.
Re a laser/particle beam hybrid making a dandy weapon - agreed.
Re the makeup of the particle beam - I haven't read all the posted links yet, but it appears that they are talking in terms of some form of neutral particle beam, so what you describe sounds possible.
My 2c worth,
Todd
