Spaceflight Insider

SLS’ boosters complete aft skirt motor test

Space Launch System SLS aft skirt off-motor hot fire test Orbital ATK photo posted on SpaceFlight Insider

Photo Credit: Orbital ATK

NASA came one step closer to having the agency’s new super heavy-lift Space Launch System (SLS) booster send crews to locations further out into the Solar System than has ever been attempted before. On Sept. 22, 2015, NASA and Orbital ATK carried out a more reserved test than the solid rocket test firings that normally light up the deserts of Utah.

Space Launch System SLS aft skirt off-motor hot fire test Orbital ATK 2 photo posted on SpaceFlight Insider

Engineers in Promontory, Utah, carry out the Aft Skirt Off Motor Hot Fire Test for the five-segment solid rocket motor planned for use on the new Space Launch System. Photo Credit: Orbital ATK

Known by the rather unwieldy name of the “aft skirt off-motor hot fire test” the review checked out the avionics and Thrust Vector Control (TVC) elements of the five-segment solid rocket boosters that are planned for use on the first versions of SLS.

A prototype SLS avionics command and control system was used during the recent test and worked to validate the booster’s TVC system.

The new avionics system is a critical aspect of SLS’ twin boosters. It controls power distribution, steers the boosters themselves, initiates the motor’s pyrotechnic devices, and communicates with the flight computers.

The SRB’s avionics package is new, but the thrust vector control system it controls is the same that the boosters that NASA’s space shuttles utilized during the thirty-year course of the program.

If everything continues to go according to plan, one of these solid rocket motors will undergo the second Qualification test leading up to the first planned test flight of SLS – Exploration Mission 1. The QM-2 test is currently slated to take place in the Spring of next year (2016). It is hoped that this steady drumbeat of testing and verification will lead to the first flight of the Space Launch System. A fact noted by one of Orbital ATK’s representatives.

“With the help of our outstanding suppliers, we have been able to design, develop, test and streamline operations as we prepare for the first launch in 2018,” said Charlie Precourt, vice president and general manager of Orbital ATK Propulsion Systems. “We are progressing toward actually putting humans on Mars – not just talking about it.”

Space Launch System SLS aft skirt off-motor hot fire test Orbital ATK 2 photo posted on SpaceFlight Insider

Instrumentation used for the test can be seen on the right-hand side of the skirt in this image. Photo Credit: Orbital ATK

As mentioned, the Aft Skirt Off-Motor Hot Fire Test will pave the way for the QM-2 test; as such, Tuesday’s test mimicked the test cycle that the SRB will undergo. Precourt provided further information about this and upcoming events that will lead to the first flight of SLS.

“Orbital ATK is on schedule with manufacturing NASA’s solid rocket boosters for its new Space Launch System. This test is one more milestone that helps us meet the EM-1 launch date, and it occurred on time within our standard static test motor build-up sequence,” Precourt, a four-time space shuttle astronaut, told SpaceFlight Insider. “Our next major milestone will be our full-scale, five-segment booster test – QM-2 – which is planned for May 2016. The QM-2 static test is the second of two qualification tests of the SLS Booster verifying booster performance requirements in support of the NASA SLS maiden flight.”

In terms of the testing carried out this week, Precourt noted that the checks were a normal step on the road to launch.

“The off-motor aft skirt hot fire is a standard check-out to ensure thrust vector command and control functionality in preparation for the QM-2 static test,” Precourt said.

The avionics checked out were developed by Orbital ATK, as well as NASA’s Marshall Space Flight Center, located in Huntsville, Alabama, along with contractors L-3 Cincinnati Electronics and Southern California Braiding.

NASA and its partners in the aerospace industry have stated SLS will be used to send astronauts on their way to the planet Mars and other, exotic locations. Precourt also noted that these efforts help pay a more terrestrial dividend.

“We pursue human space exploration because of the inspiration it provides for us to improve our capabilities across the board,” Precourt said. “Systems developed to transport humans to space, and support their activities in space, continually result in improvements in our everyday lives.”


Jason Rhian spent several years honing his skills with internships at NASA, the National Space Society and other organizations. He has provided content for outlets such as: Aviation Week & Space Technology,, The Mars Society and Universe Today.

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