This is a stretch..
I'm not sure how the human body could handle that accerleration.
Actually, the acceleration would be quite gentle - it would just be constant which would result in much higher speeds than rocket technology can achieve.
As long as there is a constant accelleration of 1G, they could get there much faster than 90 days. So the human body could easily survive the trip. However, the beam technology is suspect. The 'station' would not be able to maintain a stationary position if it's indeed sending a stream of plasma to the ship. That's simply not going to work. NASA is already working on plasma propulsion (I have a good friend working on plasma propulsion) which will be the way to explore our system. There is more than enough propulsion energy to get us around the solar system using plasma engines (like the impulse engines in Star Trek). Problem is, you need nuclear generators on the ship (like our subs have). Some people don't like nuke power in space. We *will* explore our system with manned missions, it is simply too important not too. I believe no matter who is president this will be true, but let's face it, we need to be fiscally responsible about our current spending. This is why I am very much in favor of privatization of space exploration (though we need military organization as well).
I'm not sure how the human body could handle that accerleration.
The acceleration is probably a few tenths of a G. A plain solar sail is about .01G.
What gives you the speed is the amount of time you apply that 0.2G. For a few minutes, you exceed the highway speed limit. For a few days, you get up into the tens of thousands of MPH.