Spacecraft Propulsion/talk

I heard that solar sails are propelled by photons hitting the 'sails'. But photons have no mass and therefore no momentum, so in a collision they provide no impulse? -- sodium yes the photons do provide the impulse to the sails. According to the Planetary Society ho have built the first solar sail powered craft 99% of its propulsion should come from reflecting photons, only 1% from the solar wind. See http://www.u3p.net/tipe/phot_jp.htm --rmhermen

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What about future methods like matter-antimatter propulsion? --mike dill