Both halves of a frangible nut from the External Tank (ET) umbilical plate of Space Shuttle Discovery flown on STS-103, measuring approximately 1.75" x 2" x 1", marked with part numbers: "SKD26100099-201, 11-93, 51998-00063-HRJ" and "S/N 066." Frangible nuts are designed to be explosively split apart in order to sever mechanical connections, and are most well-known for their use in the jettison of Solid Rocket Boosters (SRB). Prior to orbital insertion, they were also used for separation of the two aft structural attachments of the External Tank and the disconnection of the Liquid Hydrogen (LH2) and the Liquid Oxygen (LO2) umbilical plates. The attach bolts were driven by the explosive force of NASA Standard Detonators (NSDs) and a spring into a cavity in the tank strut. The nuts and all residual pieces of the NSDs were caught in a cover assembly within the Shuttle. This flown frangible nut, used on STS-103, is visually intriguing due to the 'puzzle piece' nature of the corresponding jagged edges. Originates from the collection of a retired NASA Astronaut and includes a signed letter of provenance.
STS-103, a Hubble Space Telescope Servicing mission, marked the 27th flight of Space Shuttle Discovery (OV-103). Launched on December 19, 1999, members of the STS-103 crew conducted three spacewalks to perform several maintenance tasks and upgrades. The astronauts replaced all six of the telescope's gyroscopes (four of which had failed, rendering it incapable of performing scientific observations), replaced a Fine Guidance Sensor, upgraded the Hubble's computer with a much faster model, installed a Voltage/Temperature Improvement Kit (VIK) to prevent battery overcharging, and replaced thermal insulation blankets.
