If you get good at Kerbal Space Program, you can install the RSS (Real Solar System) mod that is a 1:1 scale of our solar system, and is correspondingly harder. You'll need to build things with about 7800-8000 m/s of delta-V to get to LEO.
It doesn't simulate more than two bodies at a time, so gravitation influence of multiple planets and moons on an orbit are not simulated, however, you can do multiply sequential gravity assist missions.
It doesn't simulate more than two bodies at a time, so gravitation influence of multiple planets and moons on an orbit are not simulated, however, you can do multiply sequential gravity assist missions.