VASIMIR successfully tested

On Jul 12, 4:02 am, (Derek Lyons) wrote:
Do a google on "inverse square law".

Google light weight 200kW vacuum compatible power sources...

Sure its not a case of get a laser pointer from toys'r'us and
pointing. But the numbers can work with some reasonable technology
limits.

Using a Gaussian beam with a ~20 meter "spot" size at 300 000km with a
IR laser, needs a aperture of about ~28 meters. You still have a spot
size of ~28 meters at 600 000 km. Things get better with shorter
wavelengths. The numbers don't look much worse when we take a quality
factor into account (ie finite aperture etc).

And even if the collector is smaller than the spot size and we loose a
bunch of energy, we still end up with a much more light weight power
source on the craft which then has much better performance
parameters...

But its not near term.