laser(or flashlight) propelled spaceship?

[omelaw]

if we shot big-S laser (let's say, 150GW) to behind of a spaceship, then it would push ship with 500N(f=p/v), isn't it?

Is it an electromagnetic drive? (a really terrible one, admitally)

[HebaruSan]

Here's a reference on photon sails on the excellent Atomic Rockets web site maintained by KSP forum user @nyrath, helpfully situated among hours' worth of other equally fun reading.

http://www.projectrho.com/public_html/rocket/enginelist.php#id--Sail--Photon_Sail

[magnemoe]

One interesting idea is to put an mirror around the laser if you make the solar sail adaptive and well you could bounche the beam back and forward multiple times giving an far larger initial acceleration. 

[Findthepin1]

Mirror Drive

[cantab]

Yes, shining a light out the back of a spaceship will produce thrust. It will give acceleration that makes an ion drive look like a top fuel dragster, but it will work.

If you power it using fuel stored on the ship, though, it's not the most efficient method. Much better is to contrive a way to use the spent fuel as propellant.

If you power it using solar panels, I'm pretty sure the radiation pressure on the solar panels will necessarily be several times the thrust of the light.

[Temstar]

52 minutes ago, cantab said:

If you power it using fuel stored on the ship, though, it's not the most efficient method. Much better is to contrive a way to use the spent fuel as propellant.

It's not a bad idea the other around though, where you carry propellant onboard but no fuel or power system to energise the propellant. Then you just shoot a stream of propellant behind you and the laser stations vaporise it and you ride the blast up to orbit.

Whoever control this laser launch array will hold enormous political power, he/she would be able to shoot spacecraft out of orbit with impunity when the array is not busy launch crafts.

[RainDreamer]

Well there is this: https://en.wikipedia.org/wiki/Photonic_laser_thruster