The solid rocket booster that will propel NASA’s skyscraper-size, 300-plus-foot-tall Space Launch System (SLS) rocket and its Orion spacecraft in the coming years marked off a significant development milestone in March 2015, and again today (June 28, 2016), unleashing its fury on a barren mountainside at Orbital ATK’s test stand in Promontory, Utah, for the Qualification Motor-2 test fire (QM-2). The 154-foot-long booster, the largest of its kind in the world, ignited to verify its performance at a cold motor conditioning target of 40 degrees Fahrenheit—the colder end of its accepted propellant temperature range. When ignited, temperatures inside the booster reached nearly 6,000 degrees.
More than 530 instrumentation channels were used to help evaluate 82 defined test objectives that will support certification of the booster for flight.
“This final qualification test of the booster system shows real progress in the development of the Space Launch System,” said William Gerstenmaier, associate administrator for the Human Exploration and Operations Mission Directorate at NASA Headquarters in Washington. “Seeing this test today, and experiencing the sound and feel of approximately 3.6 million pounds of thrust, helps us appreciate the progress we’re making to advance human exploration and open new frontiers for science and technology missions in deep space.”
With hardware testing to support qualification of the boosters for flight now complete, and assuming the test was as much a success as QM-1, Orbital ATK is now ready to proceed toward the first flight of the SLS, an uncrewed mission to validate the entire integrated system, currently scheduled to fly on the Exploration Mission-1 (EM-1) in late 2018 (at the earliest, and likely to slip further).
Small voids were previously discovered prior to QM-1 between the propellant and outer casing of the booster’s aft segment, which demanded a lengthy investigation and trouble-shooting effort by Orbital ATK and NASA to determine root cause(s) and corrective actions before they could move forward with booster testing for QM-1 (which had been significantly delayed due to the issue). The problem which significantly delayed QM-1, however, was not an issue with the QM-2 booster.
“Finding no defects in the segment insulation we’ve inspected is a huge accomplishment for our teams, and something that hasn’t been done on past NASA programs,” said Bruce Tiller, deputy manager of the SLS Boosters Office at NASA’s Marshall Space Flight Center in Huntsville, Ala. Marshall manages the SLS Program for the agency. “That’s a testament to the work we’ve put in on refining our manufacturing processes and materials.”
With QM-2 there have been five fully developed, five-segment SRBs fired up on Orbital ATK’s Promontory, Utah, T-97 test stand since 2009, with the most recent prior to QM-1 (March 2015) having been conducted in 2011, and all performed fine. The first three tests, known as the Development Motor test series (DM-1, DM-2, and DM-3), helped engineers measure the new SRB’s performance at low temperature, verify design requirements of new materials in the motor joints, and gather performance data about upgrades made to the booster since the space shuttle program.
The five-segment SLS boosters will burn for the same amount of time as the old shuttle boosters—two minutes—but they will provide 20 percent more power, while also providing more than 75 percent of the thrust needed for the rocket to escape the Earth’s gravity.
“Ground tests are very important – we strongly believe in testing before flight to ensure lessons-learned occur on the ground and not during a mission,” said Charlie Precourt, Vice President and General Manager of Orbital ATK’s Propulsion Systems Division and four-time space shuttle astronaut. “With each test we have learned things that enable us to modify the configuration to best meet the needs for the upcoming first flight.”
“Today’s test is the pinnacle of years of hard work by the NASA team, Orbital ATK and commercial partners across the country,” said John Honeycutt, SLS Program manager at NASA’s Marshall Space Flight Center in Huntsville, Ala. “SLS hardware is currently in production for every part of the rocket. NASA also is making progress every day on Orion and the ground systems to support a launch from Kennedy Space Center in Florida. We’re on track to launch SLS on its first flight test with Orion and pave the way for a human presence in deep space.”
The first of 10 flight segments for the boosters that will be employed on that first SLS flight, EM-1, was recently cast as well. Earlier this year workers filled the insulated metal case of a booster aft segment with propellant and let it solidify, or “cure,” for several days.
The five-segment solid rocket booster has been in development for years, having been initially designed to launch NASA’s Ares rockets for the agency’s cancelled Constellation program. The booster is similar to the four-segment SRBs that helped launch NASA’s now retired space shuttle fleet, but it’s larger and incorporates several upgrades and improvements.
Orbital ATK also received a $47 million contract from the U.S. Air Force earlier this year for development of something similar: “a solid rocket propulsion system prototype to support the EELV program for national security space missions.” The rocket, if it ever manifests into reality, would use VAB high-bay 2 at KSC and launch off pad 39B—the same pad as SLS.
Although the boosters themselves will provide 75 percent of the power needed to break Earth’s hold, the SLS will still employ four engines of its own—former (upgraded) liquid-fueled space shuttle RS-25 engines—which are currently at NASA’s Stennis Space Center in Mississippi undergoing their own series of tests.
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