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 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.

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.

Note that whilst 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 has not surfaced since.

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 Integrated 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.