Rocket engineers at Stennis Space Center in Mississippi are slated to attempt a 500-sec. hot-fire test of the J-2X engine this week, running the Saturn-heritage upper-stage propulsion system through a full-duration burn for the first time.

Formerly the pacing item in the development of the terminated Ares I crew launch vehicle, testing of the human-rated J-2X is being slowed to free funds for development of a throwaway version of the space shuttle main engine (SSME) that is also baselined for the heavy-lift Space Launch System (SLS) that NASA is building in lieu of the Ares launch family started under the Constellation program. But the upcoming test is a critical milestone in the development of what is planned to be the next U.S. government space launch vehicle.

The test comes after an unexpected automatic shutdown earlier this month 140 sec. into a hot-fire test of the sole J-2X development engine. The shutdown was attributed to a programming error. Mike Kynard, a NASA manager for liquid-propellant engine developments on the SLS, says the problem occurred when a redline designed to protect hardware during some propellant-pressure variations that started at the 140-sec. mark in the test was entered as a maximum rather than a minimum. As a result, the redline triggered the shutdown at the beginning of the planned pressure excursion. “It was simply human error,” Kynard tells Aviation Week in an interview here.

With the redline reset and other specifics checked carefully, the program is ready to go for the full-duration burn on Nov. 9. “The engine was running strong, and we didn’t have any indication that the engine couldn’t have run for the full 500” sec. in the most recent test, Kynard says.

That test will set up a two-year trial series with four J-2X development engines and other test articles that will lead to a milestone the engine program calls “basic development complete.” After that, the J-2X development essentially will be put on hold until 2017-18.

The change of pace from rapid development of the J-2X for Ares will allow the reorganized liquid-fueled engines office here to stay within its expected $250 million annual budget as it completes the upper-stage engine, prepares the 15 surplus RS-25D reusable SSMEs for early flights of the SLS, and works with Pratt & Whitney Rocketdyne to develop a less-expensive RS-25E variant to power the core stage of the big new rocket.

“Because we don’t know exactly what SLS will need from a certification standpoint now, we’ve taken the certification segment and said we’ll push that out a little bit,” Kynard says. “That allows us to get the yearly budget profile down to the point that we can focus on 25D and E and get those guys up and going.”

The engine office will continue testing the J-2X at Stennis, running through the test series with the first engine — No. 10,001 — before moving on in January to detailed testing with a powerpack article consisting of the gas generator and turbomachinery.

After that work, which will push the powerpack to “the corners of the envelope,” Kynard says, the program will move on to testing with the next three development engines: 10,002, 10,003 and 10,004.