Armadillo Aerospace is a US rocket company founded by John Carmack. He is well known as the programmer who created the Doom and Quake computer games. It was the success of these games that has allowed him to fund research into rocketry.
Armadillo was founded in 2000 and has since been working on developing reusable suborbital VTVL (vertical takeoff, vertical landing) rocket vehicles. They have seven full-time employees and are located in Mesquite, Texas. Their small VTVL vehicles are similar to the vehicles developed separately by Masten Space Systems and both companies competed in NASA's Northrop Grumman Lunar Lander Challenge, though Armadillo was competing much earlier than Masten and won the Level 1 $350,000 prize (while Masten took the Level 2 prize).
In 2008, the Rocket Racing League announced that Armadillo Aerospace engines would be used in second-generation X-Racer aircraft. As of March 2010, the Rocket Racing League is utilizing a highly modified Velocity XL FG airframe and an Armadillo Aerospace 2,500 pound thrust liquid oxygen (LOX) and ethanol rocket engine in both the Mark-II X-Racer and Mark-III X-Racer demonstration vehicles.