Successful tests will
lead way for safer shuttle engine
NASA's Space Shuttle program successfully fired a full-scale
Reusable Solid Rocket Motor at a Promontory, Utah, test facility on
Thursday, June 10, testing modifications that will enhance the
safety and integrity of the Space Shuttle.
One of the modifications is a slightly different propellant
grain that changes the shape of the propellant in the forward
segment of the Space Shuttle's motor to increase the propellant's
strength. The new design improves flight safety by decreasing the
risk of cracks in the propellant during storage and transportation,
according to Jody Singer, manager of the Reusable Solid Rocket
Motor Project, part of the Space Shuttle Propulsion Office, located
at NASA's Marshall Space Flight Center in Huntsville, Ala.
Final results from the test are not immediately available. The
results will be used to qualify the modification for production and
flight.
"Even though the modification is only a slight change from what
we have flown on the Shuttle, it still requires a rigorous
certification and verification process that includes testing," said
Mike Rudolphi, manager of the Space Shuttle Propulsion Office. The
motor is one of the four Shuttle propulsion elements.
"NASA has long adhered to the maxim, 'Test what we fly; fly what
we test,'" added Rudolphi. "This test is one in a series of tests
performed to ensure this modification will perform as we
expect."
The propellant grain modification was one of 76 test objectives;
24 of those objectives will allow the Project Office to reevaluate
materials, components and manufacturing processes that are
currently in use such as nozzle bondlines, liner-to-housing
bondlines, internal insulation, pressure transducers, and
solvents.
The test will also provide additional information on a proposed
safety enhancement to the motor's nozzle. A new bolted assembly on
the nozzle's joint 5 is being tested for its strength.
The full-scale static - or stationary - test was performed at
ATK Thiokol Propulsion Division, an Alliant Techsystems Inc.,
company in Promontory, Utah, north of Salt Lake City. ATK Thiokol
manufactures the Space Shuttle's Reusable Solid Rocket Motor.
Static firings of flight support motors are part of the ongoing
verification of components, materials and manufacturing processes
required by the Space Shuttle program. Flight support motors are
tested annually to evaluate, validate and qualify any proposed
improvements or changes to the motor. The two-minute test duration
is the same length of time that the motors perform during Space
Shuttle flights.
Data from the test will be analyzed and the results for each
objective provided in a final report. The flight support motor's
metal case segments and nozzle components will be refurbished for
reuse.
This is the second test motor firing in less than a year for the
Reusable Solid Rocket Motor Office. A five-segment engineering test
motor demonstrated in October 2003 pushed the motor to its limits
so engineers could validate the safety margins of the four-segment
motor currently used to launch Space Shuttles.
At 126 feet (38.4 meters) long and 12 feet (3.6 meters) in
diameter, the Space Shuttle's Reusable Solid Rocket Motor is the
largest solid rocket motor ever flown and the first designed for
reuse. The motor, which is part of the Shuttle's Solid Rocket
Booster, is composed of four segments, each 30 feet long and filled
with propellant. During liftoff, each motor generates an average
thrust of 2.6 million pounds (1.2 million kilograms).