[Tuna-Fish]

Going to mercury on rockets alone is a non-starter, because when you drop your perihelion low enough to rendezvous with it, your velocity near Mercury will be ridiculous, and there is not enough atmosphere at Mercury to shed the velocity so you have to do it the hard way.

However, there is a very efficient trajectory that could be used by solar sailing ships for a fast, cheap route to Mercury once every 16 months. You leave Earth for Venus, where you do a gravity assist to drop your perihelion significantly below the orbit of Mercury, just to get low enough that a reasonable solar sail can get reasonable thrust even with significant cargo. Then you can use your infinite delta-v to match your aphelion with Mercury, and can do an efficient capture trajectory.

[cattlemansgold]

Is there an estimate for how long that would take with a solar sail? If the window is every 16 months and the flight time is another year or more, I would imagine a large scale mission with multiple re-supply trips would be pretty difficult.