#structural test article

Rockwell International workers install the left-hand forward payload bay door onto the Structural Test Article (STA-099) at Palmdale, California. After being used to test the launch stresses and verify the Space Shuttle design, it was later refurbished as an operational orbiter and named Challenger.

Date: February 1978

The Space Shuttle Structural Test Article (STA-099) being returned to Rockwell International's Palmdale Facility from Lockheed. STA-099 was used to test the launch and orbital stress an operational orbiter would experience. In January 1979, it was decided to convert the space frame into Challenger (OV-099), taking the operational orbiter slot intended for Enterprise (OV-101). There were many reasons NASA chose it over Enterprise, the major reasons were it was stronger, lighter and most importantly, there was less to disassemble.

Date: November 7, 1979

The Structural Test Article (STA-099) and a Lockheed L-1011 TriStar in the test rig at Lockheed facility in Palmdale, California.

The Space Shuttle Structure Test Article (STA-099) (later converted Challenger (OV-99)) being moved into the Lockheed facility for vibration stress testing.

The frame was tested for a year simulating all of the loads an operational orbiter would experience.

Date: February 14, 1978

Posted by Bill Roberts on the "STS-The Space Shuttle Legacy" Facebook group page: link

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Enterprise (OV-101) and STA-099 at Rockwell International's Plant 42 Site 1 in Palmdale, California. Parts from Enterprise were transferred to STA-099 for the conversion into the second operational orbiter, Challenger (OV-099).

Over the next several months the elevons, vertical stabilizer, payload bay doors, body flap, aft-fuselage, RCS module, and upper forward-fuselage were sent back to their respective factories for modifications.

Note: her forward fuselage is covered with a silver Mylar Insulation Blanket.

Date: November 8, 1979

Posted by Bill Roberts on the "STS-The Space Shuttle Legacy" Facebook group page: link

The Structural Test Article (STA-099) and Columbia (OV-102) under construction at Rockwell International's Plant 42 Site 1 in Palmdale, California.

Date: December 2, 1977

The structural test article (STA-099) is positioned in the test rig at Lockheed-Palmdale, California. The rig would simulate loads the orbiter would experience during launch, orbital and re-entry.

The frame was tested up to 120% of its maximum load. This was done to verify its 100-mission life expectancy.

Date: February-March 1978

"The structural test article (STA-099) is positioned in the test rig at Lockheed-Palmdale. The three large hydraulic cylinders used to simulate the SSMEs are visible at the rear."

Note: the actuators and bus attached to the upper surface of the wings. These are necessary to induce flight loads.

"The test rig was closed around STA-099 on March 15, 1978. For all the hi-tech equipment used to Test space shuttle, the flooring of the test stand was made of redwood planks."