I've actually said this in stores to young 3.5 ed guys, who saw me toting LBBs to the cash register, and asked:
This game was made in the old days, 1977. Simple to play, all you need is 2 six sided dice. With those and pwncil and paper, you can make a character in a half hour. There are no levels, you get a lot of skills, and can start out as a new guy, a soldier straight out of boot camp, or a ship captain, or a general, or admiral, depending on the power level your referee wants. With a little work, as a referee, you can design alien creatures, planets, and your own starships, ranging from a small scout craft to a huge battleship with nuclear missiles and screens. A Subsector of space averages about 40 worlds, which you can roll out in a week or less, a few hours a day, and add as much detail as you want or need, with a bit more time.
No other books needed, just these three, or the one book, the Traveller Book.
The Setting is 10,000 worlds. Feels like a huge empire, with the good guys in small ships, usually merchants, sometimes fighting against the empire, sometimes against corporations, sometimes against criminals and pirates.
If you don't want to use the game setting you can use Aliens, Dune, Pitch Black, Farscape, Red Dwarf, or Star Trek (with some work, and other games do it better).
You can fly through asteroids, crash land on a water world, blow a 10 tentacled monster to hell, board a ship in vacuum by storming the airlocks, and save the princess all in one scenario.
Sometimes I get a player out of that, who is sick of...orc bash, from an uninspired referee who gets his ideas by cracking open the monster manual, and was not trained up in "The Old-School Ways."