Engineers test a new material for the nozzle of the Space Shuttle's Reusable Solid Rocket Motor at Marshall. Photo: NASA/MSFC

A scaled-down version of the Space Shuttle's Reusable Solid Rocket Motor was successfully fired for 21 seconds last Thursday at one of the Marshall Center test stands. More than 100 spectators, including crew members of the Space Shuttle Endeavour STS-111 mission, which flew in June, watched as Marshall Center's Space Transportation Directorate tested a new material that may be used on the Solid Rocket Motor's nozzle.

Engineers from the Marshall Center Space Transportation Directorate, who conducted the test, used a 24-inch solid rocket motor to ensure a replacement material will meet the criteria set by the Shuttle's Solid Motor Project Office. The current material is a rayon-based carbon-cloth phenolic, resistant to heat, used as insulating material for the motor's nozzle. The new material, Lycocel, is expected to perform better under the high temperatures experienced during launch.

Use of the scaled-down version of the Shuttle's Solid Rocket Motor allows for a versatile, quick-turnaround, low-cost way to determine the performance of new materials.

The test, which replicates launch conditions, is part of Shuttle's ongoing verification of components, materials and manufacturing processes required by the Marshall Center, which oversees the Reusable Solid Rocket Motor project. ATK Thiokol Propulsion Division in Promontory, Utah, manufactures the Shuttle's Solid Rocket Motor.

A baseline test to provide information on how the material currently being used performs was executed in June by Space Transportation Directorate engineers at Marshall.

Lycocel, a brand name for Tencel, is a cousin to rayon and is an exceptionally strong fiber made of wood pulp produced by a special "solvent-spinning" process using a non-toxic solvent. It will also be impregnated with a phenolic resin.

The motor test -- used to qualify any proposed upgrades or changes to the motor -- is a stepping stone to a Flight Support Motor test performed at Thiokol Propulsion Corporation's Test Services facility in Promontory. The motor's 21-second test duration is the approximately one-sixth the length of time that the motors perform during Shuttle flights.

"Testing is a key element in our program, providing valuable information on design, process and material changes," said Mike Rudolphi, manager of the Reusable Solid Rocket Motor Project Office.

Following the test, the data will be analyzed and the results for each objective will be used to better understand the motor's performance. The next step for qualification of the new material will be testing on a 48-inch solid rocket motor.

At 126 feet (38.4 meters) long and 12 feet (3.6 meters) in diameter, the Shuttle's Reusable Solid Rocket Motor is the largest solid rocket motor ever flown and the first designed for reuse. During its two-minute burn at liftoff, each motor generates an average thrust of 2.6 million pounds (1.2 million kilograms).

The Marshall Center is a key leader for development of space transportation and propulsion systems.