From the web:
Star Frontiers is TSRs early foray into the realm of Science Fiction
RPGs. It was a system different than D&D in many important ways -
first there was no leveling of characters... you are given a set number
of hit (health) points and there was no increase as the adventures
progressed. Experience was used to buy skills - a nice simple skill
system where each skill you bought/earned could be advanced from level 1
(beginner) to level 6 (expert). As such, you could be a techie - taking
Computer Skill (lv 1-6), Technician Skill (lv 1-6), etc. Or you could
be doctor - taking Medical (lv 1-6). There were, of course, skills to
increase your proficiency with weapons, driving vehicles, etc.
The boxed set had two rule sets - a basic rule set which was,
admittedly, fairly simple but enough to get you into the game. The
Expanded Rules is where things really pick up. There are four playable
races in the game: Dralasite, Humans, Vrusk, and Yazirian - they have
come together to form a United Planetary Federation (shades of Star
Trek).
The game runs on percentile dice - two d10s are rolled to produce a
number between 1 and 100. This is used for almost all checks in the game
- including combat. Damage is also done using one or more d10 dice.
The box sets came with plastic d10 dice which you filled in with a white
crayon (also included).
Star Frontiers saw two major publications of box sets - though they
were essentially identical except for the cover artwork. There were a
number of high-quality adventure modules as well.