Verification/Certification
Test
The verification
program demonstrates that the RSRM meets all design and performance
requirements, and that failure modes and hazards have been eliminated
or controlled. The verification program encompasses the following
program phases: development, certification, acceptance, preflight
checkout, flight and postflight.
Redesigned
SRM certification is based on formally documented results of development
motor tests; qualification motor tests and other tests and analyses.
The certification tests are conducted under strict control of environments,
including thermal and structural loads; assembly, inspection and
test procedures; and safety, reliability, maintainability and quality
assurance surveillance to verify that flight hardware meets the
specified performance and design requirements. The "Development
and Verification Plan" stipulates the test program, which follows
a rigorous sequence wherein successive tests build on the results
of previous tests leading to formal certification.
The test activities
include laboratory and component tests, subscale tests, full-scale
simulation and full-scale motor static test firings. Laboratory
and component tests are used to determine component properties and
characteristics. Subscale motor firings are used to simulate gas
dynamics and thermal conditions for components and subsystem design.
Full-scale hardware simulators are used to verify analytical models;
determine hardware assembly characteristics; determine joint deflection
characteristics; determine joint performance under short-duration
hot-gas tests, including joint flaws and flight loads; and determine
redesigned hardware structural characteristics.
Fourteen full-scale
joint assembly demonstration vertical mate/demate tests, with eight
interspersed hydro tests to simulate flight hardware refurbishment
procedures, were completed early for the redesigned capture-feature
hardware. Assembly loads were as expected, and the case growth was
as predicted with no measurable increase after three hydro-proof
tests.
Flight-configuration
aft and center segments were fabricated, loaded with live propellant,
and used for assembly test article stacking demonstration tests
at Kennedy Space Center. These tests were pathfinder demonstrations
for the assembly of flight hardware using newly developed ground
support equipment.
In a long-term
stack test, a full-scale casting segment, with live propellant,
has been mated vertically with a J-seal insulation segment and is
undergoing temperature cycling. This will determine the compression
set of the J-seal, aging effects and long-term propellant slumping
effects.
The Structural
Test Article (STA-3), consisting of flight-type forward and aft
motor segments and forward and aft skirts, was subjected to extensive
static and dynamic structural testing, including maximum prelaunch,
liftoff and flight (maximum dynamic pressure) structural loads.
Redesigned
SRM certification includes testing the actual flight configuration
over the full range of operating environments and conditions. The
joint environment simulator, transient pressure test article, and
the nozzle joint environment simulator test programs all utilize
full-scale flight design hardware and subject the RSRM design features
to the maximum expected operating pressure, maximum pressure rise
rate and temperature extremes during ignition tests. Additionally,
the Transient Pressure Test Article (TPTA) is subjected to ignition
and liftoff loads as well as maximum dynamic pressure structural
loads.
Four TPTA tests
have been completed to subject the redesigned case field and case-to-nozzle
joints to the above-described conditions. The field and case-to-nozzle
joints were temperature-conditioned to 75 F. and contained various
types of flaws in the joints so that the primary and secondary O-rings
could be pressure-actuated, joint rotation and O-ring performance
could be evaluated and the redesigned joints could be demonstrated
as fail safe.
Six of the
seven Joint Environment Simulators (JES) tests have been completed.
The JES test program initially used the STS 51-L configuration hardware
to evaluate the joint performance with prefabricated blowholes through
the putty. The JES-1 test series, which consisted of two tests,
established a structural and performance data base for the STS 51-L
configuration with and without a replicated joint failure. The JES-2
series, two tests, also used the STS 51-L case metal-part joint
but with a bonded labyrinth and U-seal insulation that was an early
design variation of the J-seal. Tests were conducted with and without
flaws built into the U-seal joint insulation; neither joint showed
O-ring erosion or blow-by. The JES-3 series, three tests, uses almost
exact flight configuration hardware, case field-joint capture feature
with interference fit and J-seal insulation.
Four of five
nozzle JES tests have been successfully conducted. The STS 51-L
hardware configuration hydro test confirmed predicted case-to-nozzle-joint
deflection. The other three tests used the radially bolted RSRM
configuration.
Seven full-scale,
full-duration motor static tests are being conducted to verify the
integrated RSRM performance. These include one engineering test
motor used to...
Provide a database for STS 51-L-type field joints
Evaluate new seal material
Evaluate the ply-angle change in the nozzle parts
Evaluate the effectiveness of graphite composite stiffener rings to reduce
joint rotation
Evaluate field-joint heaters
There were
two development motor tests and three qualification motor tests
for final flight configuration and performance certification. There
will be one flight Production Verification Motor that contains intentionally
induced defects in the joints to demonstrate joint performance under
extreme worse case conditions. The QM-7 and QM-8 motors were subjected
to liftoff and maximum dynamic pressure structural loads, QM-7 was
temperature-conditioned to 90 F., and QM-8 was temperature-conditioned
to 40 F.
An assessment
was conducted to determine the full-duration static firing test
attitude necessary to certify the design changes completely. The
assessment included establishing test objectives, defining and quantifying
attitude-sensitive parameters, and evaluating attitude options.
Both horizontal and vertical (nozzle up and down) test attitudes
were assessed. In all three options, consideration was given to
testing with and without externally applied loads. This assessment
determined that the conditions influencing the joint and insulation
behavior could best be tested to design extremes in the horizontal
attitude. In conjunction with the horizontal attitude for the RSRM
full-scale testing, it was decided to incorporate externally applied
loads. A second horizontal test stand for certification of the RSRM
was constructed at Morton Thiokol. This new stand, designated as
the T-97 Large Motor Static Test Facility, is being used to simulate
environmental stresses, loads and temperatures experienced during
an actual Shuttle launch and ascent. The new test stand also provides
redundancy for the existing stand.
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