> No, my question was if it is possible to produce thrust just
> by electricity. Maybe shooting a lot of photons? :D
>=20
> Seriously, if we shoot n photons, we could measure how much
> energy they had. Now, if we convert this energy into mass
> (thanks to Albert's E=3Dmc=B2), would (that very small equivalent
> mass) it have produced the same thrust as if we shooted
> mass instead of energy?

That would work.  I recall seeing a model where a highly reflective
metal cone on a rod was propelled up the rod by very bright very
brief pulses of laser light.

That implies that laser light could be used as a propulsive force,
you just need something to push off of.  The question I have is,
was the "equal and opposite" force pushing the laser itself down,
or were the photons the ones losing the energy.  In the first case,
you could "zap" the Earth with a laser to push the spacecraft along
(seems unlikely), or hit the spacecraft with a laser.  In the second
case, a large sail with a laser emitter being towed along behind it
could push the whole works forward.

Mike H.

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