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A space shuttle main engine test April 21, 2006, at NASA Stennis Space Center marked the 40th anniversary of the first rocket engine test at the site. The firing also marked the 25th anniversary of NASA's STS-1, the first space shuttle mission. Then called the Mississippi Test Facility, the center conducted its first test on April 23, 1966. That historic test was on an S-II (second) stage, a cluster of five J-2 engines that powered the Saturn V rockets that took America's Apollo missions to the moon.
