On September 22, engineers successfully tested the booster thrust vector control and avionics systems during an off-motor hot-fire test at ATK. The hot-fire test simulated the test cycle that will be used in the second qualification test, which will closely resemble flight conditions.
The thrust vector control system steers the rocket nozzle based on commands passed through the booster avionics system — made up of hardware, software and operating systems that will communicate with the SLS avionics system and ground operations. The avionics also will control booster operations, like motor firing and separation motor ignition.
When completed, two five-segment boosters and four RS-25 main engines will power the SLS on deep space missions, including to an asteroid and ultimately to Mars. The solid rocket boosters — measuring 177 feet long and producing 3.6 million pounds of thrust — operate in parallel with the main engines for the first two minutes of flight. The boosters provide more than 75 percent of the thrust needed for the launch vehicle to escape the gravitational pull of the Earth.
The second qualification test, planned for spring 2016, will test the booster’s performance at a cold motor conditioning target of 40 degrees and also demonstrate that it meets applicable ballistic requirements.
“We are making significant progress in preparation for the second qualification test,” says Bruce Tiller, deputy manager of the SLS Boosters Office at NASA’s Marshall Space Flight Center in Huntsville, Alabama. Marshall manages the SLS Program for the agency. “The completion of these qualification tests is crucial in getting the boosters certified for the first two flights of SLS and staying the course for the journey to Mars.”
Four of the five segments of the booster also have been cast at Orbital ATK’s facilities. The final segment is scheduled to be cast in late September. Two of the cast segments have undergone rigorous inspections, with the other two following suit in the next two months.
“The rear and forward segments have successfully completed all non-destructive evaluation with no defect indications and are currently in final assembly,” says Fred Brasfield, Orbital ATK vice president for NASA programs. “The next major event for the rear segment will be installation of the nozzle, which is expected to happen in November.”
“Finding no defects in the segment insulation we’ve inspected so far is a huge accomplishment for our teams, and something that hasn’t been done on past NASA programs,” says Tiller. “That’s a testament to the work we’ve put in on refining our manufacturing processes and materials.”
The first booster qualification test was successfully completed in March 2015. For that test, the booster was heated to 90 degrees Fahrenheit to demonstrate how it performs in high-temperature conditions. Similar to the first test, some of the objectives of the second test include data gathering on vital motor upgrades, such as the new insulation and booster case liner and the redesigned nozzle, which increases the robustness of the design. The nozzle — the most complex part of the booster — controls expansion of chamber pressures and includes the thrust vector control system, which guides and controls the rocket.
The first flight test of the SLS will feature a Block I configuration for a 70-metric-ton (77-ton) lift capacity and carry an uncrewed Orion spacecraft, built by Lockheed Martin, 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.