[sofon]

Project starshot does have a history, beyond this press release. And they have thought through the issues. There's a great youtube video here that goes into the details:

https://www.youtube.com/watch?v=bbi1hHPpTjY

They talk about using a 1km^2 earth based laser array to accelerate the craft. They also discuss using a 1W laser on the craft, and using that to transmit data back to earth (with a similar 1km^2 array to receive the signals).

They really seem to have thought through all the issues and come up with difficult, but plausible solutions.

[blacksmith_tb]

I was wondering how much of that 100gW is lost in Earth's atmosphere - my naive assumption would be quite a bit, but maybe not so much that it would make sense to try and get the laser into orbit (also orbiting gigawatt laser would make everyone nervous, I imagine...)

[sofon]

They suggest using a frequency that minimises absorption by the atmosphere, and run the numbers. It's pretty interesting.