NASA's Journey to Mars mission got a step closer on Tuesday with the successful ground test of what will be the launch booster on the agency's Space Launch System (SLS), the world's most powerful rocket. It's the second and final qualification ground test on the booster before SLS's first crewless test flight in late 2018 with NASA's Orion spacecraft. Built by NASA contractor Orbital ATK, the booster was tested at the company's facilities in Promontory, Utah, and is now qualified for flight.
Data collected by more than 530 instrumentation channels on the booster, including ballistic performance, insulation performance, nozzle vectoring and nozzle plug performance, will now be analyzed by engineers. The fourth and final review of the SLS design and concept was completed in October, 2015.
Dubbed QM-2 (Qualification Motor-2), the full-scale, two-minute test of the 154-foot-long (47 m) solid rocket booster had 82 qualification objectives to pass when conducted at a target temperature of 40° F (4.5° C), which is the cold end of the acceptable propellant temperature range. The first test, QM-1, was conducted in March in 93° F (34° C) conditions at the highest end of the temperature range. Tests conducted at the two temperature extremes experienced on the launch pad will help engineers understand their effects on how the propellant burns in various environmental conditions.
The temperature inside the booster is considerably hotter when ignited – 6,000° F (3,315° C) – producing up to around 3.6 million pounds (16 million N) of thrust. Two of these five-segment boosters, along with four RS-25 main engines, will provide the needed power to propel the SLS on its missions to deep space. Operating for the initial two minutes of flight, and in tandem with the main engines, the boosters will provide 75 percent of needed thrust for both rocket and Orion spacecraft to achieve escape velocity.
The power upgrade of the boosters is needed for the size and scope of SLS.
"The previous generation of boosters – those used on space shuttle – were four solid rocket motor segments," Orbital ATK spokesperson, Kay Anderson, explained to Gizmag. "The boosters for NASA's Space Launch System are five segments, so they are about 20 percent longer. Loads and requirements of boosting the SLS are much greater and different than required for space shuttle, requiring advances in manufacturing and design. A bigger rocket is required for the Journey to Mars, requiring more power to boost the rocket from the launch pad."
The current SLS configuration will have a 70-tonne (77-ton) minimum lift capability, while the next planned upgrade will have 105-tonne (115-ton) lift capability for more ambitious missions. The same core stage and four RS-25 main engines will be used for both.
"SLS hardware is currently in production for every part of the rocket," says John Honeycutt, SLS program manager at NASA's Marshall Space Flight Center in Huntsville, Alabama. "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."
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