This gets gradually more difficult as the relativistic mass of the protons gets larger. Relativistic mass is a concept physicists don’t like because it’s misleading, but it’s calculated from rest mass * Lorentz factor, and the Lorentz factor depends on *relative* motion.. 2/5

Here’s the Python I used to work it out. 2 solutions are given, one for accelerating all the way, and one for Expanse style flip-and-burn at the half way point. This is more practical if you want to stop at your destination! 2/5