Pratt & Whitney Rocketdyne of Canoga Park, Calif., test fired a J-2X engine at NASA’s Stennis Space Center in Missouri in mid-July.

The successful test, which took place July 14, was disclosed by NASA in a July 15 press release. The J-2X was fired for 1.9 seconds, NASA said.

Another test of the same engine was to have taken place July 7. However, that test “was terminated at start minus six-seconds due to a minor software glitch which has since been corrected,” Walt Janowski, J-2X program manager for Pratt & Whitney Rocketdyne, said July 20.

Pratt & Whitney Rocketdyne is building nine J-2X engines: seven for development tests and two for certification tests, Janowski said. Of the seven development engines, only the one on the test stand at Stennis is complete. “Hardware for the remaining development engines is being manufactured and more than 50 percent complete,” Janowski said.

The J-2X engine, a derivative of the Apollo-era J-2, is the baseline engine for the upper stage of the congressionally mandated Space Launch System — the next U.S.-owned heavy rocket. The J-2X, a liquid hydrogen/liquid oxygen engine, would also have been the upper stage engine for the Ares 5, the heavy-lift component of the canceled Constellation program.

Congress has prescribed capabilities for SLS that are similar to those of Ares 5. Lawmakers told NASA to use Constellation contracts and shuttle infrastructure to build SLS whenever possible.

While no contracts were awarded for Ares 5, Pratt & Whitney Rocketdyne holds a contract to develop the J-2X for the Ares 1 — a crew-launcher that was to be the companion rocket to Ares 5 under Constellation.