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

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.