Talk-Polywell.org

http://www.centauri-dreams.org/?p=29341

Making it possible, in Bae’s view, was the use of laser methods in combination with tethers, but the work has grown beyond that original concept into what is being described as a ‘photonic laser thrust system,’ in which a laser is generated in a cavity between two mirrors. The resultant beam is fired from a space-based launch platform stabilized by conventional thrusters, and now we’re in territory made familiar by Robert Forward, who envisioned enormous laser installations firing beams to departing ‘lightcraft,’ sails pushed by laser light all the way to nearby stars.

And from the comments:
http://iopscience.iop.org/1063-7818/28/ ... C34D823.c1

The mass of a photon beam, equivalent to its energy, forms a gravitational potential well (an induced waveguide) in vacuum and this leads to the appearance of a self-sustained photon jet in free space. A calculation of this effect, which is analogous to the familiar self-focusing of light in nonlinear material media, is made in the paraxial approximation.

Unfortunately the meat is behind a paywall.

hanelyp wrote:http://www.centauri-dreams.org/?p=29341

Making it possible, in Bae’s view, was the use of laser methods in combination with tethers, but the work has grown beyond that original concept into what is being described as a ‘photonic laser thrust system,’ in which a laser is generated in a cavity between two mirrors. The resultant beam is fired from a space-based launch platform stabilized by conventional thrusters, and now we’re in territory made familiar by Robert Forward, who envisioned enormous laser installations firing beams to departing ‘lightcraft,’ sails pushed by laser light all the way to nearby stars.

And from the comments:
http://iopscience.iop.org/1063-7818/28/ ... C34D823.c1

The mass of a photon beam, equivalent to its energy, forms a gravitational potential well (an induced waveguide) in vacuum and this leads to the appearance of a self-sustained photon jet in free space. A calculation of this effect, which is analogous to the familiar self-focusing of light in nonlinear material media, is made in the paraxial approximation.

Unfortunately the meat is behind a paywall.

Cool stuff. Laser propulsion has been around for a while. Arthur Kantrowitz has been doing experiments as long as I can remember:
http://en.wikipedia.org/wiki/Laser_propulsion
Maybe lasers are in forefront again. Light sources have gotten more efficient than they have been in the past.

hanelyp wrote:http://www.centauri-dreams.org/?p=29341

Making it possible, in Bae’s view, was the use of laser methods in combination with tethers, but the work has grown beyond that original concept into what is being described as a ‘photonic laser thrust system,’ in which a laser is generated in a cavity between two mirrors. The resultant beam is fired from a space-based launch platform stabilized by conventional thrusters, and now we’re in territory made familiar by Robert Forward, who envisioned enormous laser installations firing beams to departing ‘lightcraft,’ sails pushed by laser light all the way to nearby stars.

And from the comments:
http://iopscience.iop.org/1063-7818/28/ ... C34D823.c1

The mass of a photon beam, equivalent to its energy, forms a gravitational potential well (an induced waveguide) in vacuum and this leads to the appearance of a self-sustained photon jet in free space. A calculation of this effect, which is analogous to the familiar self-focusing of light in nonlinear material media, is made in the paraxial approximation.

Unfortunately the meat is behind a paywall.

Actually this is practical, if there's a laser at the far end, or if the payload can redeploy its lightsail to use the star at the end to stop. But it's pretty much permanent; there better be someplace to live at the far end or they better be prepared to build one. And you aren't making this trip with stored oxygen; we better know how to live in space.

As far as previous writers, Pournelle and Niven's Mote books, and Niven's description of the Outsiders who sold humanity the FTL hyperdrive come immediately to mind. And Pournelle has written about laser launchers for Earth-to-orbit vehicles. Bova also has explored this in his Moonwar books.