How do I tell the difference between all NASA's space shuttles?

To distinguish between the various NASA space shuttles, you can look at several distinct features and modifications that were unique to each orbiter. Here are some key differences:

External Tile Patterns and Markings

• Each shuttle had a unique thermal protection system (TPS) tile pattern. For example, the tile patterns around the side hatch and the main gear doors varied. Atlantis had a distinctive dark border surrounding the main gear doors, while Discovery had strips of newer black tiles on the inner edges of the main gear doors2.

Visual Cues on the Fuselage and Wings

• Discovery: Had extra black tiles below window number 5 on the pilot side, whereas Atlantis and Endeavour had white tiles there. Discovery also had a mix of old and new Reinforced Carbon-Carbon (RCC) panels, giving it a distinctive dark, dark, light, dark appearance along the wings2.
• Atlantis: Virtually identical to the others but had a bright gray RCC wedge piece just behind the nose RCC cap, which was darker on Discovery and Endeavour2.
• Endeavour: Was the first shuttle built with a drag chute housing on the tail, which was later retrofitted to the other orbiters. Endeavour had two distinctive black "L" shaped patterns in front of the main gear doors, corresponding to the join seam between the wings and the main fuselage2.

Other Distinguishing Features

• Drag Chute Housing: Endeavour was the first to have this feature, but it was later added to the other orbiters during maintenance2.
• RCC Panels: The condition and color of the RCC panels varied among the shuttles. For instance, Discovery had a mix of old and new panels, while Atlantis and Endeavour generally had uniform appearances2.

Historical and Operational Differences

• Enterprise: Although not an operational orbiter, it was the first shuttle built and was used for atmospheric flight tests. It did not have the capability to reach orbit45.
• Challenger and Columbia: These orbiters were lost in mission accidents and had distinct early mission histories. Challenger was known for being the cleanest looking orbiter in its early flights, while Columbia was the first operational orbiter4.

By observing these specific features, particularly the tile patterns, RCC panels, and other visual cues, you can identify which NASA space shuttle you are looking at.