VentureStar was a single-stage-to-orbit reusable launch system proposed by Lockheed Martin and funded by the U.S. government. The goal was to replace the Space Shuttle by developing a re-usable spaceplane that could launch satellites into orbit at a fraction of the cost. While the requirement was for an unmanned launcher, it was expected to carry passengers as cargo. The VentureStar would have had a wingspan of 20.7 m, a length of 38.7 m, and would have weighed roughly 1000 t. VentureStar was intended to be a commercial single-stage-to-orbit vehicle that would launch vertically, but return to Earth as an airplane. Flights would have been leased to NASA as needed. After failures with the X-33 subscale technology demonstrator test vehicle, funding was cancelled in 2001.