Mongoose has used their version of Traveller in a variety of different settings as well as giving support for the traditional Third Imperium. Recently a number of OGL supplements have dealt near future and relatively hard SF settings such as Orbital by Zozer games.
While working on my Microlite20 setting I received a request to run a pulp SF game using a setting I'd pitched a while ago. Basically humans use unobtainium from a disastrous meteor strike to build atomic rockets and voyage to a pulp solar system. Action is going to center on a Venus full of swamps and dinos. I pondered what system to use and decided to use Mongoose Traveller. It already has good rules for generating and running modern/SF characters and combat, rules for weapons, encounter systems with critters of all sizes (I can just port dinos in) and spaceships of various tech levels. Psionics can provide some mad science as well.
Using Traveller in a pulp setting provides some challenges. I'll have to read the combat rules very carefully before tweaking them for larger than life characters. They could use a mook rule for starters or maybe more uses for tactical points. Like I said I'd have to look it over.
The real question is which of the two games I'll be able to run with life doing what it usually does. Gamers schedule games and God laughs.