This isn't new, there's been many discussions. But generally you spend billions making lasers, on the ground, in orbit, and on the moon has been suggested. Yo

This isn't new, there's been many discussions. But generally you spend billions making lasers, on the ground, in orbit, and on the moon has been suggested. You make the space craft with a sail a few atom thick surface tuned for the frequency of the laser to minimize weight and maximize thrust. However even 1% of the speed of light means it's going to be too far to accelerate significantly on the order of 10 minutes to 10 hours. Sure we could put laser arrays on the outer planets, but that's not particularly feasible today. So what do you do with your $billions of lasers once post launch ... of course launch more. Especially since you are likely to lose some due to radiation and space dust. Launch once an hour and hopefully your communication system can handle hops of 4 or more ships, which would be 4 hours * 0.01C = 0.04 light hours or about 1/3rd the way to mars. With some fancy encoding that doesn't seem so hard. People get across the earth on a few watts with signals 20db below the noise floor, no line of site, and a message energy sapping atmosphere and bounces off not particularly reflective soil. For some idea on the difficulty, with 1970s tech (45 years ago), voyager 1 has a 22 watt transmitter and is still communicating from well past pluto.