March 13, 2015 – The largest, most powerful rocket booster ever built successfully fired up Wednesday, March 11 for a major-milestone ground test in preparation for future missions to help propel NASA’s Space Launch System (SLS) rocket and the Orion spacecraft to deep space destinations, including an asteroid and Mars.
The booster fired for two minutes, the same amount of time it will fire when it lifts the SLS off the launch pad, and produced about 3.6 million pounds of thrust. The test was conducted at the Promontory, Utah test facility of commercial partner Orbital ATK, and is one of two tests planned to qualify the booster for flight.
“The work being done around the country today to build SLS is laying a solid foundation for future exploration missions, and these missions will enable us to pioneer far into the solar system,” said William Gerstenmaier, NASA’s associate administrator for human exploration and operations. “The teams are doing tremendous work to develop what will be a national asset for human exploration and potential science missions.”
It took months to heat the 1.6 million pound booster to 90 degrees Fahrenheit to verify its performance at the highest end of the booster’s accepted propellant temperature range.
“The booster is so large at 177 feet long, and other than the metal case around the propellant, it’s basically made up of mostly rubber-like materials,” said Mat Bevill, deputy chief engineer in the SLS Boosters Office at NASA’s Marshall Space Flight Center in Huntsville, Alabama, where the program is managed for the agency. “With that much mass, it takes about a month to affect the temperature and get it uniform all the way through.”
The booster’s propellant burn rate is temperature-dependent, so the hotter it is, the faster it burns. That propellant burn rate affects the performance of the booster both at launch and in flight.
To get the temperature to 90 degrees, the thermostat is turned up inside the test stand where the booster is housed. Sensors inside the booster measure the temperature, and analytical models also predict the time it takes for the booster to be “done” at 90 degrees.
The day of the hot fire, the test stand cover, which is on rails, is rolled out of the way.
“Outside temperatures are something we have to watch, but just like it takes a long time to heat the booster, it takes a long time to get the temperature back down,” Bevill said. “That’s why we target the highest temperature condition for testing. This isn’t a new concept – we’ve always conditioned to a certain temperature. We basically know ahead of time how the booster will respond, but we still watch and make sure it performs the way we think it will.”
During the test, temperatures inside the booster reached more than 5,600 degrees.
More than 531 instrumentation channels on the booster were measured to help assess some 102 design objectives. The test also demonstrated the booster meets applicable ballistic performance requirements, such as thrust and pressure. Other objectives included data gathering on vital motor upgrades, such as the new internal motor insulation and liner and an improved nozzle design.
“This test is a significant milestone for SLS and follows years of development,” said Todd May, SLS program manager. “Our partnership with Orbital ATK and more than 500 suppliers across the country is keeping us on the path to building the most powerful rocket in the world.”
A cold-temperature test, at a target of 40 degrees Fahrenheit, the low end of the propellant temperature range, is planned for early 2016.
These two tests will provide a full range of data for analytical models that inform how the booster performs. Once qualified, the flight booster hardware will be ready for shipment to NASA’s Kennedy Space Center in Florida for the first SLS flight.
When completed, two five-segment boosters and four RS-25 engines will be used for the first two, 70-metric-ton flights of the SLS. The rocket boosters operate in parallel with the main engines for the first two minutes of flight and allow SLS to lift more weight and reach a higher altitude before the boosters separate from the core stage. The boosters provide more than 75 percent of the thrust needed for the rocket to escape the gravitational pull of the Earth.
The first flight test of the SLS will carry an uncrewed Orion spacecraft beyond low-Earth orbit to test the performance of the integrated system.
As the SLS evolves, it will provide an unprecedented lift capability of 130 metric tons (143 tons) to enable missions even farther into our solar system, like to an asteroid and ultimately to Mars.
NASA and Orbital ATK are making major modifications to the solid rocket boosters that will power NASA’s new rocket, the Space Launch System, to deep space destinations, like an asteroid and ultimately Mars. Credit: Orbital ATK