Impressive forward External Tank (ET) separation bolt assembly from Space Shuttle Discovery flown on STS-103, measuring approximately 6.25" in diameter and 10.25" long, with a weight of 52 pounds, marked on the base: "Shear Bolt, SKD26100098-245, Mfg Date 09-93, SN-07140-00020-HCV." The forward ET shear bolt structurally ties together the Space Shuttle Orbiter and External Tank at the forward attach point; it has two threaded ports for pyrotechnic NASA Standard Initiator (NSI) pressure cartridges. When the cartridges are activated, the central piston fires and shears the attachment bolt, allowing the tank to be jettisoned. 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.