. . "External tanks." . . "Actuators." . . "Bays (Structural units)" . . "Hatches." . . "Seals (Stoppers)" . . "Failure modes." . . . . . . . . . . . . . . . . . . . "Assessment of the mechanical actuation subsystem"@en . . . . . "Independent Orbiter assessment assessment of the mechanical actuation subsystem"@en . "Umbilical connectors." . . "Spacecraft reliability." . . "Elevons." . . "Vents." . . "Space shuttle orbiters." . . "Doors." . .