May 28, 2015

— And then there was one.

When NASA retired the space shuttle in 2011, there were three orbiters to place in museums and parts enough to assemble 16 solid rocket boosters. But there was only one flight-qualified external tank remaining: ET-94.

Originally built to fly a science-dedicated mission with the orbiter Columbia, ET-94 instead helped NASA recover from the loss of the spacecraft in 2003, becoming a test article for improvements to the external tanks through the end of the program.

ET-94 was briefly considered for use with NASA's Space Launch System, its next heavy lift rocket, but ultimately was retired. Now, it will be reunited with the space shuttle, being stacked with the retired orbiter Endeavour for a one-of-a-kind exhibit at the California Science Center in Los Angeles.

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NASA's last space shuttle external tank to complete Endeavour L.A. exhibit

NASA's last remaining external tank, ET-94, as seen in 2004 after its transition from a flight to test article at NASA's Michoud Assembly Facility outside of New Orleans. As a testbed, ET-94 helped NASA return the space shuttle to flight after the loss of Columbia.

(NASA/MAF)

As the space shuttle flew out its remaining missions leading up to its retirement in 2011, NASA used ET-94 to test improvements to the external tanks. The foam that was removed as part of this work will be replaced before ET-94 departs for Los Angeles.

(NASA/MAF)

ET-94 inside the Vehicle Assembly Building at the Michoud Assembly Facility. In September 2012, it was lowered from the vertical and gently placed horizontally into its wheeled carrier, which it has sat in since.

(NASA/MAF)

ET-94, as it appears parked outside at the Michoud Assembly Facility in Louisiana today.

(California Science Center/Dennis Jenkins)

A composite nose cone like the type used in flight will be fitted on ET-94 in the final display.

(California Science Center/Dennis Jenkins)

NASA removed more of ET-94's foam during its evaluations of the tank for use with the Space Launch System, its next heavy-lift rocket. These areas will be repaired prior to ET-94 being displayed with Endeavour.

(California Science Center/Dennis Jenkins)

One of two forward attach points for the solid rocket boosters. These will serve as the main structural path for the display.

(Dennis Jenkins)

All of the hardware used to attach the shuttle orbiter to ET-94 is already at the California Science Center, having earlier been donated by NASA for use with the center's planned (but never built) replica tank. ET-94 currently has yellow ground support equipment sling adapters on the structure where the orbiter attach hardware fits.

(California Science Center/Dennis Jenkins)

The remaining feedline hardware missing from ET-94 will be transferred at the same time as the tank.

(California Science Center/Dennis Jenkins)