Solar Sail

[Ian]

I know that Cosmos Studios and the Babikin Space Center in Russia are going to launch a Solar Sail into space. They were talking about someday using lasers to propell the Solar Sail into space. I think that there should be a laser on the back of the Solar Sail that's aimed at the sails on it that can store energy and recharge in the Solar System using energy from the sun to power the laser instead of firing the laser at the Solar Sail directly from Earth.

 

[Johnny Pneumatic]

it could not move.

 

[sorgoth]

Yeah, there's a silly thing called physics.

 

[rockoon]

Yeah, there's a silly thing called physics.

However there might be something said for -collecting- the reflected energy from a laser beam sent from earth after its done its reflecting off the sail. This energy could be used to power/recharge onboard systems like radio transmitters and so forth.

 

[ceptimus]

However there might be something said for -collecting- the reflected energy from a laser beam sent from earth after its done its reflecting off the sail. This energy could be used to power/recharge onboard systems like radio transmitters and so forth.

If you collect all the energy, rather than letting it bounce back, you reduce the thrust.

 

[Soapy Sam]

You could mount the laser pointing backwards

 

[rockoon]

If you collect all the energy, rather than letting it bounce back, you reduce the thrust.

I think that depends. Surely if the collector was oriented at the same angle as the sail surface, then you would get equally proportional force in the opposite direction as you collected it. But what if you play with the angles?

Also, there is a temporal difference here that shouldnt be neglected. Consider that we take turns pushing on a bowling ball and we both push with equal force. I push first and the ball starts moving then you push from the opposite direction and the ball stops then I push and the ball starts moving and then you push and the ball stops. While this may be inefficient (the ball will go farther faster if you never reply to my pushes) it does indicate that while the energies cancel out, the 'work' does not.

 

[ceptimus]

You get twice the thrust from a (stationary) 100% reflective surface than you do from a (stationary) 100% absorbtive one. Also, a reflective surface can produce thrust at an an angle relative to the impinging radiation. An absorbtive surface can only provide thrust in the same direction as the radiation is travelling.