Many years ago, during my college days, I took an astronomy course that was taught by Carl Sagan. This was during the early part of his career, before he became quite so famous.
One of our lab assignments was to figure out a launch date, necessary velocity and trajectory, plot the course, and figure the arrival date to get a spacecraft from Earth to Mars in a minimal amount of time. Sounded very hard when first described, but it was surprisingly easy to do. We had only slide rules to calculate with - there were no pocket calculators back in those days. Fortunately, we didn't have to figure out the hard part - how to land it. We only had to put it into orbit.
That class left me with a life long interest in Mars, and I'm always pleased to see NASA achieve a new success.