Report Laser Sailing in Astronomy and Space Posted August 19, 2015 A ground based laser would not work. To quote: "To concentrate as much laser power as possible onto the reflector array, we must ensure that the beam leaving the telescope is as collimated (parallel, non-diverging) as possible. We use a laser both because we can get ultra-short pulses of light from a laser, and also because the light from a laser is extraordinarily directional—not diverging the way a flashlight, or even searchlight, would. Even so, the turbulent atmosphere distorts the beam, imparting a divergence of about one arcsecond (sometimes more). One arcsecond is 1/3600th of a degree, or the angular size of a quarter about five kilometers (about 3 miles) away. At the distance of the moon, this angle translates to 1.8 kilometers (just over a mile). Though this is large compared to the size of the reflector (most of the light is wasted—never hitting the reflector), it is still a challenge to point and maintain the laser beam on this tiny patch of the moon." As to space based lasers, E E "Doc" Smith in one of his SF books several decades ago pointed out that even if a space based heat ray is 99% efficient, it will be the devil to get rid of the cumulative effects in a space craft of heating from that 1% each time the weapon is fired. As I said elsewhere, perhaps a solar sail in a solar orbit for years, continually building up speed till it reaches target speed, then leave the Sun's orbit and as needed, use a conventional propulsion from there.