Light-Beam Powered Spacecraft

[livefree75]

If you had enough electricity and a powerful enough light source, would it be possible to direct photons a certain way to produce thrust? Basically aiming a very powerful flashlight at a deflector plate to thrust a spacecraft forward? The design would be similar to that of a solar sail except the light source would come from the craft itself.

[EzinX]

Yes. You could even just aim your flashlight like a rocket engine. The problem is that the thrust per energy is very very low. You need some method of generating bat.... insane methods of energy. Essentially you need to be able to release all of the mass-energy present in matter itself.

Antimatter drives do this (although they get some of the thrust from other particles than just photons) and black hole drives work this way.

[RainDreamer]

We also have this: http://en.wikipedia.org/wiki/Laser_propulsion

[NERVAfan]

Specifically, you have to use 300 megawatts of power per newton of thrust.

You can do twice as well if you separate the laser from the spacecraft and point it at a reflective solar sail (since the light bounces off in the opposite direction so the momentum transferred is doubled) but then you're limited by the laser (eventually diffraction spreads it out so that not all the beam is hitting the solar sail).

[AngelLestat]

You can multibounce the beam, which you extract F(Newtons)=[2P(watts)/c] * bounce times.

This work for distances close to 1000km

Another way to see this, is that the proppelent you burn, only push the payload without waste too much speed to accelerate the proppelent and engine mass.

Edited December 5, 2014 by AngelLestat