Marshall Eubanks wants to send a swarm of 1000 flyweight probes to the
nearest star, reaching it in 20 years.
https://www.researchgate.net/publication/373833951_Swarming_Proxima_Centauri_Optical_Communications_Over_Interstellar_Distances
However:
1. Sending just 1000 probes is fatally timid. We should think in terms of millions of identical probes. Produced in volume, their price-per drops to near nothing. The entire probe could have just one chip plus a couple of capacitors and coils.
2. Launching just one probe swarm would be wasteful: having built the solar-pumped launching laser/maser, we have no reason to turn it off: keep launching probes throughout the life of the mission. The cost of a million probes is small vs. the cost of the project overall. Over the next 20 years, launch 1000 probes (or more: 10,000, 50,000) each week. Having accelerated to cruising speed, probes turn to fly edge-on, minimizing collision risk.
3. With the launch apparatus operating throughout the mission, there is no need to accelerate to cruising speed immediately. This allows a much lesser beam intensity, and radically reduces G loading on the probes.
4. There is no value in having probes formed up in a plane at the destination. A dispersed cloud of a million probes flying through continuously for 20 years offers enormously greater value. The first few thousand through the system can identify interesting bodies, and subsequent swarms can tack against starlight and concentrate on those. This eliminates the "predict position of planetary bodies" problem.
5. Probes spend almost all their flight time close to zero K. This creates design opportunities denied to other projects. The sail surface may be an atomically thin wafer of superconductor, providing perfect reflection of any long-enough wavelength, stiffened by its own field.
6. Trying to transmit data home via laser would be a monumental blunder: the starlight behind the probes interferes with any optical signal. Worse, at optical frequency, phased-array transmission by clouds of probes is impossible; but at ordinary radio frequency, a cloud may transmit as a phased array with no difficulty, having triangulated their relative positions and synchronized to a pilot signal from home. Receivers throughout the asteroid belt may remain synchronized to operate as a phased array using atomic clocks (as was used to image M87).
7. There is no need for probes at the destination to transmit their data all the way home. They need only send to the next swarm coming up a light-day or light-week behind, which may relay data to the next.
8. Upon approaching the destination, the swarm may focus incident light (laser/maser/starlight) on a few, selected probes to slow them down enough to enter orbit. Subsequent swarms flying through can provide phased-array communication, and assist altering their orbits, with the occasional additional probe joining them.
9. A launch laser may be a simple laser cavity pumped with sunlight reflected from an array of monochromatic mirrors ranged around it, with no conversion loss. Monochromatic mirrors are easily produced by depositing alternating layers of transparent material with different dielectric constant but identical thickness. Given continuous operation throughout the mission, a much lower power output (10GW? 1GW?) becomes wholly adequate.
10. But consider the alternative of launching with an array of masers, instead. Masers are much more easily constructed and operated. An array of independent masers can be maintained in phase with the aid of atomic clocks.
11. With two swarms sent out in different directions, you get a phased-array radio telescope light-years across that can (e.g.) image the surface of a pulsar, using the pulsar itself to synchronize. The second swarm could get away with many fewer probes than the first, but you might better target another star with it.
Can this be improved upon?
