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298 points Teever | 1 comments | 24 Aug 25 17:54 UTC | HN request time: 0.266s | source

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habibur ◴[26 Aug 25 22:08 UTC] No.45032963[source]▶

This won't enable perpetual space travel in case anyone thought so.

Rockets need to eject particles to generate force. And to eject 1 kg of fuel, its photo synthesis system has to lose 1 km of mass in one way or another.

The solution is to find a way to generate thrust without rocket fuel ejection.

replies(2): >>45033094 #>>45033506 #

Buttons840 ◴[26 Aug 25 22:22 UTC] No.45033094[source]▶

>>45032963 #

Can we "swim" through space? Collect particles from space, add energy, expell them backwards to generate a net thrust.

replies(5): >>45033121 #>>45033235 #>>45033248 #>>45033348 #>>45033987 #

1. o11c ◴[26 Aug 25 22:41 UTC] No.45033235[source]▶

>>45033094 #

There's a huge density difference if you aren't close to a planet or star.

Solar sails are probably more practical.

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Chinese astronauts make rocket fuel and oxygen in space