The NASA Space Shuttle (SS) Orbiter Vehicle (OV) portion of the Space Transportation System (STS) comprises a series of spaceplanes numbered by OV-100 series. These have also been referred to as Constitution-class space shuttles, due to the fact the first anticipated working example was originally named Constitution, prior to being renamed Enterprise. These spaceplanes were originally provisioned with turbofans for in-atmosphere propulsion after re-entry, but these were deleted early in the design stage, and the shuttles are purely gliders during their atmospheric operation phase.
The class comprises:
- MPTA-ET, the external tank fit test article
- MPTA-098, an engineering test skeleton for testing the main engines
- OVTA-098, an engineering fit test article
- OV-098 Pathfinder, the combination of MPTA-098 and TA-098 as an integrated display item
- STA-099, a structural test article
- OV-099 Challenger, originally STA-099, refit for spaceflight
- OV-100 Independence (ex-Explorer), a high fidelity mockup
- OV-101 Enterprise (ex-Constitution), the atmospheric flight test vehicle, originally planned to be refit for space
- OV-102 Columbia, the spaceflight test vehicle, refit for standard operation
- OV-103 Discovery, the first production shuttle
- OV-104 Atlantis, the final initial production shuttle
- OV-105 Endeavour, the supplementary production run shuttle