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A comment on LightSail 2 Spacecraft Successfully Demonstrates Flight by Light. Parent comment

Re:LightSail 2 Spacecraft Successfully Demonstrates Flight b... by umvi on Wednesday July 31, 2019 @06:16PM (#20579113)
Net effect is not zero if the photon bounces off of the sail
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Re:LightSail 2 Spacecraft Successfully Demonstrates Flight b... by comboy on Wednesday July 31, 2019 @06:24PM (#20579204)
Why use sail then? You can just shoot your photon the opposite way.
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Re:LightSail 2 Spacecraft Successfully Demonstrates Flight b... by seiferteric on Wednesday July 31, 2019 @06:55PM (#20579459)
That would be a "photon rocket" which is an existing idea, but requires a lot of energy, whereas this uses free energy from the sun.
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Re:LightSail 2 Spacecraft Successfully Demonstrates Flight b... by gitgud on Wednesday July 31, 2019 @06:26PM (#20579221)
If it bounces off in the opposite direction then the net effect would be actually be negative.
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