Each NASA space shuttle designation is composed of a prefix and suffix separated by a dash. The prefix for operational shuttles is OV, for Orbiter Vehicle. The National Aeronautics and Space Administration (NASA) is an agency of the United States Government, responsible for that nations public space program. ... NASAs Space Shuttle, officially called Space Transportation System (STS), is the United States governments current manned launch vehicle. ...

The suffix is composed of two parts: the series and the vehicle number.

Series:

• 0 - Non-flight ready shuttles
• 1 - Flight Ready shuttles

The vehicle number is the sequentially assigned within the series, beginning with 1. Therefore, there can never be a OV-100 as it would read "Orbiter Vehicle Series 1 Vehicle 0".

Many proposals to build a second generation of orbiters, externally compatible with the current system but internally new, refer to them as "OV-200" or "OV-2xx" in order to differentiate them from the "current generation", the OV-100s. This terminology is informal, and it is unlikely that any Shuttle-derived vehicle built will be given such designation.

Orbiter Designations

• OV-098 - Space Shuttle Pathfinder, a structural mockup
• OV-099 - Space Shuttle Challenger, originally STA-099
• OV-101 - Space Shuttle Enterprise
• OV-102 - Space Shuttle Columbia
• OV-103 - Space Shuttle Discovery
• OV-104 - Space Shuttle Atlantis
• OV-105 - Space Shuttle Endeavour

Notes: Challenger was originally intended to be used as a Structural Test Article, rather than a flight-capable orbiter; as such, the numbering was changed when she was rebuilt. Enterprise, on the other hand, was intended to be rebuilt into a flight-capable orbiter; it was found to be cheaper to rebuild STA-099 than OV-101, so she remained unflown. The designations were not altered, despite this change in fortune. The Space Shuttle Orbiter Pathfinder (honorary Orbiter Vehicle Designation: OV-098) is a Space Shuttle simulator made of steel and wood. ... Space Shuttle Challenger (NASA Orbiter Vehicle Designation: OV-099) was NASAs second Space Shuttle orbiter to be put into service, after Columbia. ... The Space Shuttle Enterprise (NASA Orbiter Vehicle Designation: OV-101) was the first Space Shuttle built for NASA. It was constructed without engines or a functional heat shield and was therefore not capable of space operations; her purpose was to perform test flights in the atmosphere. ... Space Shuttle Columbia (NASA Orbiter Vehicle Designation: OV-102) was the first spaceworthy space shuttle in NASAs orbital fleet (Enterprise preceded Columbia, but Enterprise was a non-spaceworthy test article intended for later conversion to a flightworthy vehicle). ... Space Shuttle Discovery (NASA Orbiter Vehicle Designation: OV-103) is one of three remaining spacecraft in the Space Shuttle fleet belonging to the U.S. National Aeronautics and Space Administration (NASA), along with Atlantis and Endeavour. ... Space Shuttle Orbiter Atlantis (NASA Orbiter Vehicle Designation: OV-104) is one of the space shuttle fleet belonging to the U.S. National Aeronautics and Space Administration (NASA). ... Space Shuttle Orbiter Endeavour (NASA Orbiter Vehicle Designation: OV-105), is the fifth and final operational NASA space shuttle to be built. ...

Note that while Pathfinder is referred to as OV-098, she should not be confused with MPTA-098 - the Main Propulsion Test Article, a steel frame (looking nothing like an Orbiter) used to test the Space Shuttle Main Engines on. Pathfinder was originally a "fit check" unit, a simple mockup resembling the production Orbiters in size, shape and weight, intended to be used to ensure that ground handling facilities would be sized to handle Orbiters. She was later rebuilt to resemble them cosmetically, and is currently on display with the external tank used during the propulsion tests (designated MPTA-ET). To further add to the confusion, it appears that Pathfinder was never formally numbered, and the OV-098 designation is both unofficial and retroactive. MPTA-098 was later rebuilt into the Shuttle-C mockup during the 1990s; it is currently in storage at the Stennis Space Center. Main Propulsion Test Article being lifted onto its test stand in 1977. ... Space Shuttle Main Engine block The Space Shuttle orbiter has three main engines. ... The Space Shuttle External Tank (ET) on its way to the Vehicle Assembly Building. ... The Main Propulsion Test Article ET was built by NASA to be used in conjuction with MPTA-098 for structural tests of the Space Shuttle prior to construction of flyable craft. ... An artists conception of a Shuttle-C launching at night. ... The John C. Stennis Space Center (or SSC), located in Hancock County, Mississippi at the Mississippi/Louisiana border, is NASAs largest rocket engine test facility. ...

In keeping with this theme, other pieces of ground hardware used by the Space Shuttle program have been given OV-xxx designations; these include:

• OV-095 - a mockup in the Shuttle Avionics Integration Laboratory (SAIL) at Johnson Space Center.
• MPTA-098 - the Main Propulsion Test Article, as above
• OV-106 - an administrative name given to the set of structural components manufactured to replace those used in the construction of Endeavour; however, the contract for these was cancelled shortly afterwards, and they were never completed.