It seems to me that a T20 version of this game could potentially be very D&D-like, at least with the sort of creatures you'd encounter on Venus and Mars. Venus had lizardmen, and Dinosaurs. Mars has humanoid aliens, no magic of course, but its kind of counterintuitive to expect any sort of space opera set in 1889 to be realistic. One thing about it, is the setting is on a smaller scale than any of the other versions of Traveller besides Twilight 2000. There is no need for any sort of UWP. The rules for building spaceships will be a little different, with steam drived either propellers to move the ships around