Hard Vacuum is a fast and fun game of primitive rocket combat. The game is set during an alternate history where just enough weird science exists to push World War II into space. The two main books, Hard Vacuum and Science Gone Mad are still available at Sierra Madre Games and or (if you’re lucky) your local game store’s dusty bargain bin.
Other than the setting, three things set Hard Vacuum apart when it came out in 2001. It used simultaneous orders system similar to today’s Flight Path games that added layers to trying to outguess and outmaneuver your opponent. It had a very elegant vector movement system that I can’t believe hasn’t been appropriated by other games. And it used exploding d6’s numbered from 0-5 because exploding dice are awesomely fun, but it always bugged me that you couldn’t get a “6” result on one.
A quick start guide is up at How It Plays over at the publisher’s website: Fat Messiah Games. Rumor has it the designer is tinkering with an updated version that will advance the game’s timeline all the way to the far flung year 2000!