khayo@sonia.math.ucla.edu (Eric Behr) (05/06/88)
SPACE SHUTTLE TRANSIENT PRESSURE TEST ARTICLE-4 FIRING SCHEDULED
RELEASE: 88-61
May 5, 1988
NASA's Marshall Space Flight Center will test fire the
fourth in a series of transient pressure test articles (TPTA),
May 9 at 2 p.m. EDT at its East Test Area in Huntsville, Ala.
The test is part of the Space Shuttle solid rocket motor (SRM)
redesign program and the final required TPTA test prior to
resumption of Shuttle flights.
This test will have intentional flaws in the insulation of
all three test joints and flaws in the capture feature, wiper and
primary 0-rings in each test joint. Seals in the safety and
arming/igniter joints also will be intentionally flawed.
This test utilizes the second test article of the TPTA test
series which incorporates the flight design field joint
insulation configuration.
The TPTA test program consists of short-duration, hot-fire,
dynamic-load tests of full-scale hardware in a short stack
configuration.
The test article is a segmented solid rocket motor, 52 feet
long and 12 feet in diameter. The tests are designed to evaluate
the effects of temperature, pressure and external loads
encountered by the solid rocket motor primarily during ignition
transients.
The test motor, designated TPTA 2.2, will be fired for six-
tenths of a second (0.6), achieving an expected maximum pressure
of 950 pounds per square inch, and then will be vented to outside
air conditions after approximately 120 seconds.
Upon ignition, dynamic strut loads will be applied to the
motor from a separate load tower. The induced loads will
simulate flight loads from the Shuttle's external tank near the
rear of the motor. Also, a million pound weight will be placed
on top of the forward segment to simulate the loads associated
with the external tank and orbiter.
For this test, flaws have been intentionally incorporated in
both of the test article's field joints, the case-to-nozzle joint
and the safety and arming/igniter joints.
The two field joints have intentional flaws in the J-Seal
insulation, the capture feature o-ring and the primary o-ring to
permit pressure to reach the secondary o-ring.
The nozzle-to-case joint has intentional flaws in the
polysulfide adhesive, the wiper o-ring and the primary o-ring to
permit pressure to reach the secondary o-ring.
The safety and arming/igniter joint has intentional flaws in
the o-rings, gask-o-seals and putty to permit pressure to reach
the secondary seals.
These intentional flaws simulate multiple failures of joint
sealing features and therefore, demonstrate the fail safe nature
of the redesigned solid rocket motor joints.
Both the case-to-nozzle joint and safety and arming/igniter
joints will be heated to 70 (plus/minus 5) degrees farhenheit at
time of test. All non-test joints will have a minimum
temperature of 75 degrees farhenheit.
There are 1,000 channels of recorded instrumentation on the
motor for engineers to verify the structural performance, thermal
response and sealing capability of the redesigned field and case-
to-nozzle joints.
The TPTA series of tests is a joint effort between Morton
Thiokol Inc, United Space Boosters Inc., Wyle Laboratories and
the Marshall center. Wyle conducts the tests for Marshall, which
manages the redesigned solid rocket motor program for NASA.
TRANSIENT PRESSURE TEST ARTICLE (TPTA) PROGRAM FACT SHEET
TPTA Purpose
As part of the overall redesign program for the Space
Shuttle solid rocket motor (SRM), a series of tests of the
effects of pressure transients and loads encountered by the
redesigned solid rocket motor during ignition is required. The
Transient Pressure Test Article (TPTA) tests, to be conducted in
the East Test Area of NASA's Marshall Space Flight Center in
Huntsville, Ala., will provide data to verify the sealing
capability of the redesigned SRM field and case-to-nozzle
joints.
Four TPTA tests are mandatory prior to resumption of Space
Shuttle flights. Additional tests may be conducted prior to the
STS-26 mission to further assess the redesigned joints under
external loads.
Test Article Configuration Description
The TPTA is a short-stack, mostly inert, solid rocket motor
test article. It is more than 52 feet long (633 inches) and 12
feet in diameter. The motor weighs 548,144 pounds, including
approximately 400 pounds of propellant to simulate the pressure
rise for ignition.
The TPTA consists in part of two case segments loaded with
inert propellant connected by two redesigned field joints. The
field joints are of the redesigned capture feature tang and
clevis design with fluorocarbon (Viton (TM)) o-rings. The mating
insulation surfaces at each field joint for this fourth test
consist of a flight type J-shaped seal bonded with an adhesive
that utilizes motor internal pressure to increase the sealing
action of the bonded surfaces.
For this test, flaws have been intentionally incorporated in
both the test article's field joints, the case-to-nozzle joint
and the safety and arming/igniter joints.
The two field joints, designated as test joints A and B,
have intentional flaws in the J-Seal insulation, the capture
feature o-ring and the primary o-ring to permit pressure to reach
the secondary o-ring.
The nozzle-to-case joint, designated as joint D, has an
intentional flaw in the polysulfide adhesive, the wiper o-ring
and the primary o-ring to permit pressure to reach the secondary
o-ring.
The safety and arming/igniter joint, designated as joint G,
has intentional flaws in the o-rings, gask-o-seal and putty to
permit pressure to reach the secondary seals.
With these intentional flaws through the primary seals,
which will permit pressure to reach the secondary o-rings, this
test is designated as a fail-safe test for joints A, B, D and G.
Both field joints, the case-to-nozzle joint and S&A/igniter
joints will be heated to 70 (plus/minus 5) degrees Farhenheit at
time of the test. All non-test joints will have a minimum
temperature of 75 degrees Farhenheit.
The case-to-nozzle joint is the redesigned configuration
with 100 7/8-inch diameter radial bolts added to minimize the
amount of joint opening during motor pressurization. The joint
also incorporates adhesively bonded insulation surfaces, a shaped
relief slot and an added Viton "wiper" o-ring designed to keep
the adhesive on the insulation surfaces during assembly.
A standard aft skirt is fitted to the motor. For the TPTA
tests, the aft skirt is attached to actual launch pad hold-down
posts.
What Happens During the Test
During the TPTA test, pressure is produced by a standard
solid rocket motor igniter and approximately 400 pounds of
propellant to duplicate the maximum pressure rise of the motor.
Maximum expected pressure of 950 PSIA is achieved in about six-
tenths of a second (0.6). The gas producing the pressure is
contained in the test article for 120 seconds to simulate the
duration of the motor burn. During the pressure cycle, dynamic
strut loads will be applied to the motor from a specially
designed external tank attach (ETA) load tower. Three connecting
load lines or actuators will induce loads which will simulate the
three struts that attach the SRM to the Shuttle's external tank
at the base of the motor.
At the same time, the test article is subjected to a million
pound weight attached above the forward segment. This weight
simulates the remainder of the Shuttle elements on the launch
pad. The strut loads are synchronized with the ignition pressure
transient to recreate joint loading conditions that occur after
ignition when the pressure in the motor increases, causing the
case to bulge and rotate. The TPTA test article includes
instrumentation to record 1,000 channels of data to measure
strain, deflection, temperature, pressure data and other
conditions.
Upon completion of each test, the test article will be
refurbished in a facility adjacent to the test stand. A large
crane will destack segments from the test stand and place them in
the refurbishment facility. Each test motor will be taken apart,
inspected, refurbished and new propellant added before being
fired again. The last test in this series was March 21.
TPTA Test Objectives
The primary test objectives are:
* Certify the ability to the field and nozzle-to-case joint
seal systems, in a fail-safe mode with pressure to the secondary
o-ring, to provide a pressure seal with no erosion or blow by and
accommodate structural deflections during the ignition transient
and simulated motor operation.
* Certify the ability of the igniter joint sealing system,
in a fail-safe mode with pressure to the secondary o-ring, to
provide a pressure seal with no erosion or blow by and
accommodate structural deflections during the ignition transient
and simulated motor operation.
* Certify the reliability of the field, nozzle-to-case and
S&A/igniter joints.
* Certify in a fail-safe mode the sealing capability of
the redundant and verifiable vent port plug seal system in the
field and nozzle-to-case joints
* Simulate the SRM maximum pressure rise rate.
* Simulate external loading influences on the sealing
capability of the redesigned SRM joint.
* Provide high temperature gas and pressure to determine
effects of J-seal insulation and O-rings.
* Obtain reliable, repeatable SRM joint deflection data.
* Verify static and dynamic models of the field and case-
to-nozzle joints.
* Demonstrate design solutions for the field and nozzle
joints.
* Verify the redesigned ETA ring model.
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Eric