Pictured is an artist's concept of the experimental Reusable Launch Vehicle (RLV), the X-37 located in the cargo bay of a space shuttle with Earth in the background. The X-37 was designed to launch from the space shuttle's cargo bay as a secondary payload. Once deployed, the X-37 would remain on-orbit up to 21 days performing a variety of experiments before re-entering the Earth's atmosphere and landing. The X-37 program was discontinued in 2003.