Here are my tug, explorer, and unmanned prove(with Mechjeb 2 part, if the pilot was transferred out. And oops, the designation doesn't seem to be unique xD Hercules 1B-10 This twin Rocketmax tank hauler ended up a most versatile craft from refueling a mothership, space station, and even some stranded SSTOs due to my design failures and lack of flight skill. Actually, there was A model with 4 Rocketmax tanks but they were not detachable and was too heavy to perform any space operation, even simple station docking. Actually, B-1~9 was a total failure even with less payload due to shortage of delta V. But B-10 was the first one hit the nail and operational. Although this shot was taken on a one way mission to Duna, to refuel a stranded mothership with weird orbital plane(almost 90 degree...), it can return to Kerbin. Hercules 1B-25 A usual day of Hercules 1B-25 with part number optimization, removing redundant central ASAS module and RCS thrusters which causes huge lagging when it operates around a space station. But this model still suffers from unwanted rolling when SAS is not operational(Also, I'm not sure that Rocketmax size ASAS are working correctly...), So, I've managed a bit more lightened version. Hercules 1C-2 Early variant of C model. It still suffers from redundant part system performance drag, but has better delta V than B variant when running a tug mission. Also, if one decides to feed from Rocketmax tank, it can reach Jool.. in theory. Still grinding for better designs!