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Release: 01-342

Space Shuttle engineering motor test will ‘push envelope’ to demonstrate component capabilities

A full-scale static test of an engineering test motor for the Space Shuttle’s Solid Rocket Booster is scheduled to fire for 123.1 seconds Thursday, Nov. 1, at a Utah test facility.

Results from the test — conducted at the Promontory, Utah, facilities of ATK Thiokol Propulsion, an Alliant Techsystems Inc., company — will be used to demonstrate the capabilities and limits on process, material, component and design in the Shuttle’s Reusable Solid Rocket Motor.

The Reusable Solid Rocket Motor Project Office at NASA’s Marshall Space Flight Center in Huntsville, Ala., fires engineering test motors as part of Shuttle’s on-going safety program to verify materials and manufacturing processes. The Marshall Center requires the static – or stationary – test before new materials or processes are included in motors flown on the Space Shuttle.

On the motor currently being tested, there are 72 test objectives, with a total of 446 instrumentation channels that collect data for evaluation of these objectives. The two-minute test duration is the same length of time that the motors perform during Shuttle flights.

An engineering test motor offers the opportunity to spot any flaws, as well as to conduct “push-the-envelope” testing to gauge the components’ ability to meet flight requirements.  The test simulates many of the conditions that would be experienced in flight.

There are 10 principal objectives for the test of Engineering Test Motor–2 (ETM-2).  One is to demonstrate a new low temperature seal (O-ring) material in the aft, or bottom, field joint.  This material has demonstrated higher resiliency at lower temperatures in laboratory tests than the current Viton O-ring material.  To test the material, channels have been cut through the ETM-2’s aft field joint J-leg – named for its J-shape – so that gases reach the new material to demonstrate flaw tolerance.

Another noteworthy test on the ETM-2 is an asbestos-free nozzle flexible boot – a thermal barrier that keeps hot gases off the nozzle's gimballing, or guiding, mechanism. The current boot contains asbestos.

The firing also will test, or retest, several potential nozzle improvements, including: a new adhesive that bonds metal parts to phenolic parts; new environmentally friendly solvents; a new nozzle ablative insulation; carbon fiber rope thermal barriers in three of the six nozzle joints; and a modified bolted assembly design on the No. 5 nozzle joint.

Following the test, the data will be analyzed and the results for each objective provided in a final report. 

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.

The Marshall Center is NASA's lead center for development of space transportation and propulsion systems and advanced large optics manufacturing technology, as well as microgravity research — scientific research in the unique low-gravity environment inside the International Space Station and other spacecraft.