Laser propulsion?

Can someone explain to me how it works? I read somewhere while ago that there were/are plans to use laser propulsion to reach orbit, and that it is more ecological than chemical propulsion. Now I don't understand how is such sytem suposed to work. I can imagine that solar sails could be "pushed" by a laser beam instead of solar wind, but how could someone use laser beam to get a ship into the orbit_.

[edit on 23-2-2005 by longbow]

The bottom end of a spacecraft is coated with a special ablative material that 'explodes' a little at a time when a laser is shined on it. The continuous 'explosions' push the craft upward.

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If you do a search for " Shiva Star", the worlds most powerful laser, and had a nice sized one of these, some time soon we go to orbit no problems...all it needs is a bit of time to mature...