WASHINGTON — A successful two-minute test of a five-segment solid rocket booster June 28 is the final development milestone for the shuttle-derived boosters before their use on the first flight of the Space Launch System.
The test, known as Qualification Motor 2 (QM-2), demonstrated the booster’s performance when cooled to approximately 5 degrees Celsius, the lower end of its range of operating temperatures. NASA swiftly declared that the booster firing, conducted at an Orbital ATK test site near Promontory, Utah, was a success.
“It’s not just a test firing, it’s really a qualification motor test firing, which fits into a sequence that essentially says this design is ready to go fly,” said Bill Gerstenmaier, NASA associate administrator for human exploration and operations, in a media teleconference an hour after the test.
Analysis of data collected during the test, which was delayed by an hour to replace a failed hard drive in ground support equipment, is still in its initial phases. Agency officials, though, appeared pleased. “We’ve had a chance to look at just some very, very preliminary data,” said Alex Priskos, manager of the SLS Boosters Office at the Marshall Space Flight center, “and everything looks great so far.”
The QM-2 test, and the QM-1 test in 2015 that verified the booster’s performance at the upper end of its temperature range, are the final tests of the solid rocket booster. Two of the five-segment boosters will be used on the SLS, along with four RS-25 engines previously used on the space shuttle.
The data collected from QM-2 and other tests will feed into a design certification review for the booster in the summer of 2017. “For those of us worried about delivery schedules and that, it’s just around the corner,” Priskos said.
The first launch of the SLS, on a flight known as Exploration Mission 1 (EM-1), is currently scheduled for late 2018. Three of the ten solid motor segments needed for that launch have already been produced at the Orbital ATK facility near the test site. All ten of the motors should be completed by next fall, said Charlie Precourt, vice president and general manager of Orbital ATK’s Propulsion Systems Division.
Gerstenmaier said that the official target date for EM-1 is September 2018, but that date is likely to slip slightly. “We’re trending more towards maybe the October-November timeframe,” he said, not singling out any particular component of that mission as the cause of that slip. “Really almost all of our components are on the critical path to some extent.”
He said that work should not be affected by the uncertainty NASA’s overall exploration program faces by the upcoming presidential election, which brings with it the potential for significant changes by the next administration.
“I think if we can show with our evidence, by just direct work of our folks of steady progress moving forward, I think that helps build support for our program,” he said. “I think the best thing we can do is just kind of stay focused on what we’re doing” and not overreact to outside developments.
Orbital ATK, in addition to its work developing and testing the solid rocket boosters, is also in the initial phases of a U.S. Air Force-funded study of a large launch vehicle that would use similar booster motors in its lower stages.
“All of these developments feed upon each other,” Precourt said when asked how the SLS works aids that vehicle design study. That includes improvements in manufacturing capabilities and the speed at which the company can assemble booster components. “Whatever we do with a given concept or a given motor system, we will use the best of that on the next design.”