Phys.org has an article about a NASA paper that proposes a way to propel spacecraft without rockets. It would use directed photons to push the spacecraft along. They think it could be used for fast interplanetary travel, and other things such as protecting the ISS from debris.

Sounds like one more of those unlikely things. It would be nice if it could work though.

Bill Gill
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C is not the speed of light in a vacuum.
C is the universal speed limit.