What if we built an electromagnetic track around the circumference of the moon? We could then accelerate a spacecraft to a very high speed. In theory it would only be limited by the strength of the materials holding the craft to the track and the centripetal acceleration that the craft/people could endure. The energy could come via the sun via a solar sail that would be positioned with it's reflective side face toward the sun. In that scenario you would not even need the track to be an electromagnet. You could simply keep it like a simple rail track. Or if you did do the electromagnetic rail you could simply gather the energy via solar panels. Since there is very little atmosphere around the moon I don't think friction would be much of a concern. Based upon my calculations for people (tolerate ~20g), radius of the moon is 1,737m, then the velocity that would be achieved would be 5888 m/s...which means that the craft would arrive at mars in 1.2 years. Now that isn't exactly quick but...if we could increase the tolerance for acceleration or used robots the time required would quickly drop. Or if we added an additional propulsion system. The best part is that you could make the craft as large as you want and accelerate it as fast as you want. Thoughts?