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Approaching asteroid? Is this THE one?
Feb 18, 2020
There is a very good article in Astronomy May 2021, entitled Breakthrough Starshot: A Voyage to the Stars.

Essential reading for anyone who thinks that this is a practical means of space travel.

"A necessary requirement for the Breakthrough Starshot mission is keeping the mass of each sail-equipped Starchip to just a few tenths of an ounce (a few grams). . . . . . . likewise the solar sail itself, which is expected to span up to around 13 feet (4 metres), will need to weigh in at less than 0.035 oz (1 gram). It will also need to be extremely thin, as otherwise the sail would absorb far too much heat and be vaporized by the barrage of laser light . . . . . . " the barrage of laser light to drive a few grams??
"Mass is the bane of accelerating objects to great speeds. To significantly increase the velocity of a heavy object takes a tremendous amount of energy. So, if the goal is to reach a distant star in a reasonable amount of time, say within a generation, a spacecraft must be extremely tiny and, therefore, robotic. Plus, it still requires an insanely energetic boost to get up to speed."
" . . . propelling a lightsail-equipped nanocraft, or Starchip, would require hundreds of individual lasers ,spanning roughly 200 acres (1 square kilometer). The array would also need access to enough energy to fire a coherent 100 gigawatt laser beam for several minutes during each . . . launch. That's roughly the amount of power generated by all the nuclear power plants in the U.S. in a given year."

Another problem occurred to me, which is not mentioned. 200 acres of individual lasers surely would not be very manoeuvrable. Would it be able to follow said Starchip, even for a few minutes (as the Earth turns)? Also, would it not be usable only at a fixed latitude - that at which it was built?

Not to mention stopping when it gets there!

Cat :)
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Mar 15, 2021
I like the idea of tiny light sails but the laser should be in space.
One satellite with a laser or lasers and dozens of solar sails racing to somewhere. The first one sponsored by Earth Space Scouts troop #2021. The Olympics could have a 13 meter class.
Twin sails on a chip containing all the episodes of the Star Trek TV show if I win the lottery.
Mar 21, 2021
I read the “breakthrough star shot” article. It’s a fun subject, but they seem to rely on Moore’s law like it’s a fundamental physical law of the universe. Their laser energy requirements of “a few gigawatt hours” is doable. I’ve developed grid-level energy storage plants with >100 MWh, but transmitting laser communications from a 1 gram probe that can be received from 4 light years away... very hard to believe given real atoms and real photons of optical wavelength.
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