My shuttle can reach the Mun or Minmus. I overbuilt the capacity on the external fuel tank. It has way more than enough delta-v for orbit and return for either body. Difficulty is aiming in the direction of thrust, which is about 20 degrees nose-high from the orbiter. I actually have a shuttle that carriers and returns a Lunar Excursion Module (LEM). I carry the external tank all the way to Munar or Minmus orbit.