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The test stand was modified in 1986 to support the "Technology Test Bed engine," a modified Space Shuttle Main Engine, and again to support the 1998 test firing of a Russian RD-180 rocket engine

The TTB engine, with a much smaller diameter than the S-IC stage, was mounted here, south of center of the test stand, above the deck over the flame deflector (which would have been the level of the engines when an S-IC was loaded in the stand).