Rocket motor tested as NASA plots next phase of program
BY STEPHEN CLARK
Posted: September 8, 2011
A stretched five-segment solid rocket motor sent a rumble across the Utah landscape Thursday, pushing engineers closer to completing the design of a next-generation booster to help propel astronauts on journeys deeper in space.
Thursday's demonstration, called Demonstration Motor-3, was the the third test firing of the five-segment motor by ATK. NASA and ATK officials say the next step is to move from demonstration tests to qualification motors, which would lead to flight testing in a few years.
"Given the great success we've had on these three tests, I think we're close to calling the design good," said Charlie Precourt, vice president and general manager of ATK space launch systems. "If we're successful at that, we could be saving quit a bit of money for the government."
Each test firing of the rocket motor costs about $75 million, according to NASA.
ATK is developing the solid rocket motor under a contract with NASA. Initially designed as the first stage of the canceled Ares 1 rocket, the motor's purpose was retooled to be a strap-on booster for the Space Launch System, a heavy-lift vehicle that will haul 130 metric tons to low Earth orbit and facilitate human expeditions to asteroids and Mars.
The motor's design is based on the four-segment booster from the space shuttle program. By adding an additional segment, the rocket generates more thrust during its two-minute burn. The motor measures 12 feet in diameter and stretches 154 feet long.
NASA has selected the design of the Space Launch System, or SLS, to include a hydrogen-fueled core stage, two strap-on five-segment boosters and a liquid-fueled upper stage. But the space agency has not publicly released details of the design, drawing the ire of lawmakers charging the White House is undermining the future of the U.S. manned space program.
"The program is being restructured and we expect some news not too far in the future," Precourt said.
At least for now, the agency is also withholding approval for the next step in the motor's development.
A NASA spokesperson said the next firing in the test sequence will be a qualification motor, beginning the process to verify a flight-like rocket booster is ready for launch.
The solid rocket motor is also planned to be the first stage for ATK's proposed Liberty rocket, a commercial launcher the company hopes will one day haul astronaut crews into orbit.
ATK probably has sufficient data from three demonstration firings to press on to the motor's critical design review, according to Precourt.
"We're looking into it in great detail to understand how it compares against [predictions] to see whether we're ready to freeze the design," Precourt said.
Fred Brasfield, ATK's vice president for the next-generation booster, said the first look at the test data looks great.
The DM-3 firing was designed to test the rocket motor with its pre-packed solid propellant warmed to approximately 90 degrees Fahrenheit. It follows tests that occurred at cold and ambient temperatures.
"We've bounded, if you will, the temperatures of the propellant on a given launch day," Precourt said, noting weather conditions can affect the rocket's performance.
Assuming NASA approves another test, Precourt said ATK could have another booster ready to fire in one year.
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