miniGunner

http://prntscr.com/7zyd6r This thing may be ugly but it brought me to Duna and back with just over 6400 dV. (Notice that this was unmanned rescue mission. First mission was with roughly same shuttle, but with a little bit less punch and more weight from science modules... Needed 300 more dV to get back to Kerbal. Poor Kerbanauts were waiting 3 years for rescue )