Colonial Troopers: Original Edition Rules for Hard Sci-Fi Games (2016)

From publisher blurb:

What if the first RPG was inspired by hard Science Fiction as written by Robert Heinlein, Poul Anderson, Isaac Asimov, and Frank Herbert instead of Tolkienesque fantasy?

Colonial Troopers is a science fiction RPG. If your tastes run towards battle hardened combat armor, some attention to real physics, and explorations of just what it is to be human, you’ve found the right book. As in the fiction of the above writers, the Player Characters (PCs) are confronted with an unforgiving universe full of wonders and deadly quirks of science ready to astound and enchant, and cull the unwary.

The rules are based, in their most basic form, on the original fantasy roleplaying game; all elements are intended to be mostly compatible with that system, its successive editions and versions, and with other old school retro-clones. The rules presented here are intended to be either a complete game, in and of itself, or to serve as a companion to other games using the same overall system. This book is a resource for Game Masters to pick and choose from, whichever suits your fancy. These other books are not necessary to enjoying this one, but elements of those books combined with this one is sure to result in a truly unique experience suited to each group’s taste.