The Black Horse was a study concept for a proposed winged spaceplane that would use aerial refueling to greatly reduce the size of the spacecraft, to about the size of an F-16 Fighting Falcon. The original concept was proposed in 1993 by US Air Force Captain Mitchell Burnside Clapp, who was familiar with the Air Force's use of aerial refueling to extend the performance of combat aircraft. The concept was further developed by others, including a smaller concept developed by Robert Zubrin, named the Black Colt. Clapp left the Air Force in 1996 and partnered with Zubrin to form Pioneer Rocketplane, who proposed a slightly larger version known as Pathfinder.