The Lockheed Martin X-33 was an unmanned, sub-scale technology demonstrator suborbital spaceplane developed in the 1990s under the U.S. government-funded Space Launch Initiative program.
Lockheed Martin X-33 adalah spaceplane suborbital demonstran tak berawak, teknologi sub-skala dikembangkan pada 1990-an pada Program Space Launch Initiative di bawah pendanaan pemerintah AS.