yee@ames.arc.nasa.gov (Peter E. Yee) (07/30/88)
Lisa Malone
Kennedy Space Center, Fla. July 28, 1988
KSC Release No. 56-88
FLIGHT READINESS FIRING OF STS-26 SHUTTLE VEHICLE SET FOR AUG. 1
KENNEDY SPACE CENTER, Fla. -- Launch Pad 39-B will be the stage
for Discovery's Wet Countdown Demonstration Test and Flight
Readiness Firing - two important events toward the next Space
Shuttle launch. The eastern sky will brighten when Discovery's
main engines are fired for approximately 22 seconds - scheduled
for no earlier than 7:30 a.m. Monday, August 1.
Test objectives include evaluating the performance of
various components of the shuttle, external tank, solid rocket
boosters as well as the launch facilities and support equipment.
In addition to verifying Shuttle system integrity and main
propulsion system performance, the test serves to verify
propellant delivery systems.
Some of the specific goals include: verifying the integrity
and performance of the shuttle main propulsion system (orbiter,
main engines and the external tank), verifying the capability of
the combined launch facility and new or modified shuttle systems
to provide propellants at the specified conditions, perform
external tank tanking test and ice formation evaluation,
determine the external tank's chill effect on the solid rocket
motor cases, assess the performance of the SRM field joint
heaters during tanking and monitor field joint heater
temperatures, assess the stiffness of combined SRM cases, aft
skirts and external tank attach ring and calculate loads on the
eight SRB hold down bolts.
In addition all members of the launch team designated to be
in the Firing Room on launch day are required to participate in
the Flight Readiness Firing activities. Members of the Mission
Management Team will be at their consoles in the Operations
Support Room in Firing Room 1 for both tests. Members of the
Office of Space Flight Management Council including RADM. Richard
Truly and NASA center directors, and NASA Administrator James
Fletcher will be in the Operations Management Room in Firing Room
1 for the FRF.
During the hiatus in launching over the past two and a half
years many modifications have been made to the Space Shuttle's
systems and launch facilities. Last year, officials decided to
incorporate the two tests into Discovery's processing flow to
provide engineering data to evaluate the various systems
modifications, and to provide an opportunity to exercise the
launch teams and revised procedures.
Over 700 pieces of instrumentation installed on the shuttle
vehicle and mobile launcher platform will provide engineers with
important data to be used during the test and for analysis after
the test.
For both tests, the countdown activities will parallel those
of a standard shuttle launch countdown. The flight crew will not
board Discovery during the tests and software inhibits (patches)
will prevent the ignition of the two solid rocket boosters.
WET COUNTDOWN DEMONSTRATION TEST (WCDDT)
This is the second Wet Countdown Demonstration Test (WCDDT)
to be conducted with the shuttle vehicle. The other time was
prior to STS-1 flight in 1981. The test began at the T-43 hour
mark at 11:33 p.m. Sunday, July 24 and is scheduled to culminate
at 5:30 a.m. Friday, July 29 at the T-10 second point.
Discovery's external tank will be filled with its flight
load of a half-million gallons of cryogenic propellants at the T-
6 hour mark in the countdown.
After the tank is full, the ice/debris inspection team will
proceed to Launch Pad 39-B. They will inspect the external tank
and assess the integrity of the thermal protective system
covering the tank while its loaded with cryogenic propellants. In
addition, they will characterize ice or frost formations on the
tank. The team will also look for possible debris on the launch
platform or Fixed Service Structure that could blow around during
launch and cause possible damage.
During these tests, the ice team will baseline a new
infrared shuttle thermal imaging system consisting of a portable
unit and two permanent units equipped with 10 power telescopes -
one on the top of the Rotating Service Structure and one at a
nearby camera site - to measure vehicle surface temperatures for
the duration of tanking, testing and drainback. The fixed devices
will be controlled remotely from consoles in Firing Room 2.
At the T-1 hour, 10 minute mark, the countdown will enter a
built-in hold for three hours and 45 minutes. During that time,
several tanking tests will be conducted on both the liquid
hydrogen and liquid oxygen systems. Important engineering data
will be gathered during these tests.
The countdown will proceed down to the T-10 second point
when a cutoff will be given. Inside the T-10 second mark is when
the shuttle's main engines are programmed to start. But for the
"wet" tanking test, the main engines will not be started and the
solid rocket boosters will not be ignited.
The SRB hydraulic power units, which are used to steer the
rockets, will be started just prior to the cutoff at T-10 seconds
and a gimbal profile of the SRB nozzles will be conducted prior
to their shutdown. In addition, the orbiter's auxiliary power
units will be run to high speed and shut down.
About 10 minutes after the cutoff, the external tank slowly
will be emptied of its liquid hydrogen and liquid oxygen as
scrub/turn around activities begin in preparation for the FRF.
The cryogenic propellants will be returned to their storage tanks
at the pad and will be reused for the FRF and launch.
FLIGHT READINESS FIRING (FRF)
Activities for this test, one of the most critical and
hazardous ground tests performed at KSC, will mirror most of the
operations in a 72-hour scrub\turn around launch attempt and
shuttle launch countdown.
Some of the "scrub\turn around" activities include draining
the external tank, removing special instrumentation from the
external tank inter tank area and inspecting the SRB hydraulic
power units for any hydrazine that may have leaked during the
test. The RSS will be moved back in place around the orbiter.
At the T-11 hour mark, the countdown will enter a planned
built-in hold for four hours, 10 minutes. During this time the
water tank for the sound supression water tower will be filled to
the top. The tower holds approximately 300,000 gallons of water
and all of it will be dumped during the FRF. Another event that
occurs at this time are preparations to roll the Rotation Service
Structure (RSS) back to the park position away from the vehicle.
When the countdown resumes at the T-11 hour mark, at about
6:10 p.m. Sunday, July 31, the RSS will be rotated away from the
vehicle and parked in the launch configuration.
Tanking begins with loading liquid hydrogen at about the T-6
hour mark. Thirty minutes later workers will start loading liquid
oxygen into the tank. Filling of the external tank will begin
slowly and then build to "fast fill" before going into the
"stable replenish" mode where the tank is constantly being topped
off as the cryogenic propellants boil away. The stable replenish
mode will continue until the tank is pressurized just minutes
before T-0.
After the tank is full, the ice/debris team will make
another trip to the launch pad for a two-hour inspection.
Afterwards they will report their findings to management. For the
FRF, the same infrared scan system will be augmented with three
additional units which, in addition to measuring vehicle surface
temperatures, will characterize the thermal environment of SSME
firing and shutdown. These infrared instruments will be located north
of the flame trench, and at two camera sites at the perimeter of the
pad to provide total coverage around the vehicle.
At the T minus three hour mark, the countdown will enter the
standard two-hour built-in hold. There are two 10-minute built-in
holds at the T-20 and T-9 minute points.
At T-6.6 seconds the ground launch sequencer will issue the
main engine start command. There will be a standard staggered
engine start sequence - main engine 3, 2, and 1 will be started
120 milliseconds apart in that sequence.
Cutoff of the main engines will be initiated by an induced
Redundant Set Launch Sequencer Abort.
The orbiter's onboard general purpose computers will detect
a failure of the main engines to have achieved a preset thrust
level of 150 percent and will command shutdown of the No. 1
engine about 19.4 seconds after the start command was given.
Cutoff of the No. 2 engine will be given at 20.6 seconds and the
No. 3 engine cutoff will occur at about 22 seconds.
Two of Discovery's engines have never flown before - engine
2022 in the No. 2 position and engine 2028 in the No. 3 position.
Engine 2019, in the No. 1 position, has flown three times and has
been through an FRF. All engines went through acceptance testing
at the Stennis Space Center, Bay St. Louis, Miss., prior to being
shipped to KSC. All three engines arrived and were installed in
January 1988.
After engine shutdown and initial safing, propellant
drainback and other post-FRF operations will begin to reconfigure
the ship and launch preparations will resume.
PREVIOUS STS FLIGHT READINESS FIRINGS
KSC's launch processing team has conducted five previous
FRFs. Each was conducted from Launch Pad 39-A to qualify the
Columbia, Challenger, Discovery and Atlantis for their maiden
voyages into space.
Two test firings were required on Challenger because of an
elusive hydrogen leak detected during the initial FRF. There are
no requirements to conduct an FRF before STS-27 or STS-28,
Atlantis' and Columbia's first post-Challenger flights.