(FORTUNE Small Business) – Jim Benson isn't the only computer entrepreneur to found a space company. Meet four other techies who have succumbed to the lure of the final frontier.

PAUL ALLEN The billionaire who co-founded Microsoft has invested more than $20 million into SpaceShip One, a space plane crafted by aerospace designer Burt Rutan and powered by Benson's hybrid rocket motor. On June 21, 2004, SpaceShip One became the first private craft to reach suborbital space.

ELON MUSK The e-commerce wunderkind made his fortune before age 30 by selling Zip2 to Compaq for $307 million in cash and PayPal to eBay for $1.5 billion in stock. He went on to found SpaceX in El Segundo, Calif. The firm is developing low-cost ways to launch small payloads into space using liquid oxygen and kerosene-powered rockets.

JEFF BEZOS For the past three years Amazon.com founder Bezos, 40, has been pouring greenbacks into Blue Origin, a Seattle-based rocket-building company. Bezos hasn't been forthcoming about the company's mission, but Blue Origin is known to have financed research on wave rotor rocket motors and other exotic technologies.

JOHN CARMACK The 33-year-old Carmack founded id Software, maker of the popular Doom and Quake videogames (featured in FSB's July/August issue). Three years ago Carmack launched Dallas-based Armadillo Aerospace to develop hydrogen-peroxide-fueled rockets. —JOI PRECIPHS