STS-3 was the first shuttle launch with an unpainted orange external tank.
The Space Shuttle’s first two missions, STS-1 and STS-2, used white-painted external tanks. NASA initially worried that ultraviolet exposure during long periods on the launch pad could damage the tank’s spray-on foam insulation. For STS-3, engineers determined the paint was unnecessary, so the tank’s natural rust-orange insulation was left visible.
The change saved roughly 600 pounds (272 kilograms), increasing the shuttle’s available payload capacity. The orange color was not paint: it came from the tank’s spray-on polyurethane foam insulation, which helped protect the cryogenic propellant tanks and maintain their thermal performance.
STS-3 launched Columbia on March 22, 1982, with astronauts Jack Lousma and Gordon Fullerton. A common mix-up is assuming STS-1 or STS-2 had the familiar orange tank; both used white-painted tanks. STS-3 also carried out testing of the shuttle’s Canadian-built Remote Manipulator System and became the only shuttle mission to land at White Sands Space Harbor.