I wasn't talking about chemicals.

My computation assumed an antimatter engine. Any drive is bound by conservation of energy and momentum.

I guess you wanted to object to an propulsion drive. Sure, you can do some fly by maneuvers or use earth bound laser propulsion, but I'm not convinced that it will put a dent in it for a regular space ship.

Also, the starshot concept won't help you with slowing down. I was assuming you actually wanted to exit the spaceship upon arrival.