Launch from Cape Canaveral (
KSC
) and
landing on Cape Canaveral (
KSC
), Runway 15.
The
STS
-121 (
ISS
ULF
-1.1) test flight mission was originally to be
flown aboard Atlantis in September 2005, after Space Shuttle Discovery flew
STS-114
, but a problem with the landing
gear of Atlantis moved Discovery ahead to fly
STS
-121. After the return of Discovery to California
following the completion of
STS-114
,
scheduling again changed. Atlantis was moved up to fly the
STS-115
mission (whose launch was
planned for August 2006) and Discovery was to fly the
STS
-121 mission as originally planned. The launch of
the
STS
-121 mission was delayed until July 2006 as well,
due to an unresolved foam debris and the Engine Cut Off (ECO) sensor issue from
STS-114
.
The launch was delayed
twice due to bad unacceptable weather.
Thomas
Reiter
's position was previously planned to be filled by
Sergei
Volkov
before the launch of
STS
-121 was postponed until July 2006. Astronaut Piers
Sellers
replaced Carlos
Noriega
who was originally scheduled to be on the
STS
-121 mission
NASA
announced on July 15, 2004. This was due to an
undisclosed, temporary medical condition.
After the
Columbia accident
,
NASA
decided that two test flights would be required
and that activities that were originally assigned to
STS-114
would need to be divided into
two missions because of the addition of post Columbia safety tests.
The
main purposes of the mission were to test new safety and repair techniques
introduced following the
Columbia
disaster
of February 2003 as well as to deliver supplies,
equipment.
Discovery delivered with
ESA
astronaut Thomas
Reiter
a third crew member
to live aboard the station as
part of
Expedition 13
.
It was the first time a three-person crew resides on station for a long
duration since the
Expedition 6
crew returned to Earth May 04, 2003, in
Kazakhstan. Without the space shuttle to ferry equipment to the station after
the Columbia accident, only two people could be supported onboard until the
necessary provisions were in place. To help deliver tons of supplies, Discovery
carried an Italian-built pressurized cargo container called Leonardo, in its
cargo bay.
During and after launch much attention was paid to monitoring
the external tank for the loss of insulation foam. The shuttle was equipped
with a number of new cameras, and video was also taken from spotter planes.
Each solid rocket booster contained three cameras - one to monitor the
separation, and two focused on the leading edge. The video from these was not
to be broadcast, but recorded for later retrieval from the solid rocket
boosters. A further camera was placed on the external tank, as during
STS-114
, to broadcast live images on
NASA
TV during launch. The first thing two of the crew
from the mid-deck did when the main engines cut out were leave their seats to
take photographs and video of the external tank. One of the factors that were
potentially affecting the choice of day within the launch window was the
lighting conditions for this imagery, as the sun's slightly different angle on
the different days affected the location of shadows on the external tank.
However, the day to day difference in lighting was determined to be relatively
unimportant, particularly as the lighting conditions depended to a great degree
on a more unpredictable factor - the degree to which the external tank tumbles
on separation.
During the launch,
NASA
TV broadcast a view from the external tank camera
mounted between the Shuttle and the external tank. Unlike the previous two
missions, no foam breakage or foam pieces were easily seen falling off the
tank. However, upon close inspection of the many cameras covering the launch
NASA
has revealed several small pieces of debris were
seen jetting away from the tank. Generally, though, these were seen after the
time
NASA
was most concerned about.
About 23 minutes
into the flight, further debris was observed floating beside the orbiter as
reported by Mission Specialist Michael
Fossum
. His transmission was broadcast live on
NASA
TV. Michael
Fossum
initially described the debris as a 4-5-foot-long
(1.2-1.5 m) piece with straps attached, a description which would fit a thermal
protection system blanket. Such a blanket was noted to be flapping on the
previous mission,
STS-114
, but was not
of concern, as it protects a section of the vehicle which does not get
particularly hot. Analysis of video images on the ground has indicated that the
debris observed was strips of ice formed on the outside of an engine nozzle,
which sublimated and disintegrated during observation. Very similar ice
formations were seen on earlier missions.
En route to the
ISS
, the 50-foot (15 m)-long
Orbiter Boom Sensor
System (
OBSS
)
tipped with two types of lasers and a
high-resolution television camera was used to inspect the underside of the
shuttle for damage. Particular attention was paid to the leading edges of the
shuttle's wings.
The post mission management team briefing after flight day
2 revealed that the inspections had found that a gap filler was protruding on
the port side lower wing, not a location of particular concern. The gap filler
was not from an area which has been modified since
STS-114
; it had been with the vehicle
since 1982. The height and location of the gap filler was to be investigated
further and, if necessary, dealt with using the procedure established and
proven by
STS-114
, during a
spacewalk.
Discovery's approach to the International Space Station
during the
STS
-121 rendezvous and docking process included a
tricky maneuver first demonstrated on
STS-114
. The orbiter was commanded to conduct a back flip,
enabling station crew members to take digital, images of the shuttle's heat
shield.
With Commander Steven
Lindsey
at the controls, Discovery performed the 360-degree
pitch-around maneuver with the orbiter about 600 feet (182.9 meters) below the
station. The flip took about nine minutes to complete, offering
Expedition 13
Commander Pavel
Vinogradov
and
Flight Engineer
Jeffrey
Williams
time photograph tile surface imagery of Discovery.
The photos were then downlinked through the station's Ku-band communications
system for analysis by systems engineers and mission managers. The photos were
taken out of windows 6 and 7 in the
Zvezda
service module with Kodak DCS 760 digital cameras and 400 mm and 800 mm lenses.
The imagery during the
R-bar Pitch Maneuver (RPM)
were among several
inspection procedures instituted after the
Columbia accident
designed to detect and determine the extent
of any damage the orbiter's protective tiles and reinforced carbon-carbon
surfaces might have sustained.
The sequence of events that brings Discovery
to its docking with the station began with the precisely timed launch of the
shuttle, placing the orbiter on the correct trajectory and course for its
two-day chase to arrive at the station. During the first two days of the
mission, periodic engine firings gradually brought Discovery to a point about 9
½ miles (24.6 km) behind the station, the starting point for a final
approach.
About 2 ½ hours before the scheduled docking time on flight
day 3, Discovery reached that point, about 50,000 feet (15,240 meters) behind
the
ISS
. There, Discovery's jets were fired in a terminal
initiation (TI) burn to begin the final phase of the rendezvous. Discovery
closed the final miles to the station during the next orbit.
As Discovery
moved closer to the station, the shuttle's rendezvous radar system and
trajectory control sensor (TCS) began tracking the complex, and providing range
and closing rate information to the crew. During the final approach, Discovery
executed several small mid-course corrections at regular intervals with its
steering jets. That placed Discovery at a point about 1,000 feet (304.8 meters)
directly below the station where Steven
Lindsey
took over the manual flying of the shuttle up the
R-Bar, or radial vector toward the complex, the imaginary line drawn between
the station and the Earth.
He slowed Discovery's approach and flew to a
point about 600 feet (182.9 meters) directly below the station, and if
required, waited for the proper lighting conditions. The rendezvous was
designed to optimize lighting for inspection imagery as well as crew visibility
for critical rendezvous events. On verbal cue from Pilot Mark
Kelly
to alert the station crew, Steven
Lindsey
commanded Discovery to begin a nose-forward,
three-quarter of a degree per second rotational back flip. At
R-bar Pitch Maneuver (RPM)
start, the
ISS
crew began of series of photographs for
inspection. The sequence of photography mapping provided optimization of the
lighting conditions.
Both the 400- and 800-mm digital camera lenses were
used to photograph the required surfaces of the orbiter. The 400-mm lens
provided up to 3-inch (7.6 centimeters) resolution and the 800 could provide up
to 1-inch (2.5 centimeters) resolution as well as detect gap filler protrusions
of greater than .25 inch (6.4 mm). The imagery included the upper surfaces of
the shuttle as well as Discovery's belly, nose landing gear door seals, the
main landing gear door seals and the elevon cove with 1-inch analytical
resolution. Since the
STS-114
mission,
additional zones were added for the 800-mm lens to focus on the gap fillers on
Discovery's belly when the orbiter was at 145- and 230-degree angles during the
flip. There was enough time for two sets of pictures. When Discovery completed
its rotation, it returned to an orientation with its payload bay facing the
station.
Steven
Lindsey
then moved Discovery to a position about 400 feet
(121.9 meters) in front of the station along the V-Bar, or the velocity vector,
the direction of travel for both spacecraft. Mark
Kelly
provided Steven
Lindsey
with navigation information as he slowly inched the
shuttle toward the docking port at the forward end of the station's
Destiny
Laboratory.
Mission specialists Lisa
Nowak
and Stephanie
Wilson
also played key roles in the rendezvous. They operated
laptop computers processing the navigational data, the laser range systems and
Discovery's docking mechanism.
Using a view from a camera mounted in the
center of Discovery's docking mechanism as a key alignment aid, Steven
Lindsey
precisely aligned the docking ports of the two
spacecraft. He flew to a point where the docking mechanisms were 30 feet (9.14
meters) apart and paused to check the alignment.
For Discovery's docking on
July 06, 2006, Steven
Lindsey
maintained the shuttle's speed relative to the
station at about one-tenth of a foot per second (3 centimeters per second)
(while both Discovery and the station were traveling at about 17,500 mph =
28,163 km/h), and kept the docking mechanisms aligned to within a tolerance of
three inches (7.6 centimeters). When Discovery made contact with the station,
preliminary latches automatically attached the two spacecraft. Immediately
after Discovery docked, the shuttle's steering jets were deactivated to reduce
the forces acting at the docking interface. Shock-absorber-like springs in the
docking mechanism dampened any relative motion between the shuttle and the
station. Once that motion between the spacecraft had stopped, Stephanie
Wilson
secured the docking mechanism, sending commands for
Discovery's docking ring to retract and to close a final set of latches between
the two vehicles.
The docking set the stage for the opening of the
hatches and the start of joint operations, including the transition of Thomas
Reiter
to the
Expedition
13
.
International Space Station
Flight Engineer
Thomas
Reiter
, representing the European Space Agency (
ESA
), flew
to the space station aboard Discovery. He had to lead the transfer of supplies
from the shuttle's cargo module to the space station during the spacewalks and
he assisted with suit-up prior to the spacewalks. He was conducting his second
long-duration spaceflight mission. He spent 179 days in space in 1995-1996 on a
mission to the Russian MIR space station during which he conducted two
spacewalks and about 40 European scientific experiments. Thomas
Reiter
was the first
ESA
astronaut to live aboard the International Space Station for a long-term
mission. Thomas
Reiter
worked on the station as part of an agreement between
the Russian Federal Space Agency and
ESA
.
Thomas
Reiter
remained on the space station until the
STS-116
space shuttle.
The
Leonardo cargo carrier
housed in Discovery's payload bay was berthed to
the space station
Unity
module's Earth-facing port on flight day 4. This was the fourth trip to the
station for Leonardo, the first of three such Italian-built cargo carriers to
be put into service. Leonardo flew to space for the first-time aboard Discovery
during
STS-102
in February 2001.
The
Multi-Purpose Logistics Module Leonardo was mated to the space station's
Unity
module. It was carrying:
- 80 °C Freezer. This freezer is known as the
Minus Eighty Degree Laboratory Freezer for
ISS
(MELFI). The French built unit comprises four
independent drawers which can be set to operate at different temperatures.
Initially, temperatures of -80 °C, -26 °C, and +4 °C will be used
during on-orbit
ISS
operations. Both reagents and samples will be
stored in the freezer. As well as storage, the freezer is designed to be used
to transport samples to and from the
ISS
in a temperature-controlled environment. The total
capacity of the unit is 300 liters.
- The European Modular Cultivation
System (EMCS) for biological experiments. This consists of a gas tight
incubator in which there are two centrifuges, each able to carry four
experimental cartridges. Two "Ground controls" - exact copies of the equipment
and experiments - will be run on the ground, one in Europe and one at
NASA
's Ames Research Center.
- New oxygen
generation system. This device is considered a test for an equipment design
with potential for use on proposed future long durations to the Moon and Mars.
The system will initially run below its maximum capacity, though it is designed
for enabling the
ISS
to support a crew of six in the future. It will
supplement the Russian-built Elektron system operating in the
Zvezda
module.
- New cycling machine for the
ISS
crew. A Danish built device, the Cycle Ergometer
with Vibration Isolation System (CEVIS).
- Replacement common cabin air
assembly heat exchanger used to control the internal air temperature of the
ISS
.
Also carried in the payload bay: an
Integrated Cargo Carrier with the Trailing Umbilical System (TUS) for the
Mobile Transporter (returning old one); an EATCS/Pump Module (PM); and 2 Fixed
Grapple Bars for PM & TUS relocation during
EVA
,
as well as an
LMC
carrying the DTO-848 TPS Repair Box.
The
first
EVA
was performed by Piers
Sellers
and Michael
Fossum
on July 08, 2006 (7h 31m) for maintenance on the
stations mobile transporter and a test of astronaut movement on the end
of the robotic arm boom extension for possible heat shield repairs during
future flights.
During the first spacewalk, the crew members tested the
50-foot robotic arm boom extension, usually used for remote shuttle thermal
protection system (TPS) inspections, as a potential work platform for
hard-to-reach repair sites on the bottom of the orbiter for detailed test
objective (DTO) 849. They also began maintenance of the station's mobile
transporter (
MT
) by safing or replacing a cable cutter and routing
a cable on the
MT
to allow it to be moved before the second
spacewalk. The cable cutter, called an interface umbilical assembly (IUA), is
on the top, or zenith side of the
MT
. A duplicate device on the Earth-facing, or nadir
side, of the
MT
inadvertently cut the nadir cable in December 2005.
The crew first worked on keeping the zenith IUA from activating in the
future by either installing a device to block the cutter from the cable or
remove the IUA and replaced it with a new unit launched on Discovery. The
Expedition 12
crew had
tried to safe the zenith IUA during a spacewalk in March 2006 by installing a
safing bolt, but the bolt could not be inserted. To prevent the cable from
being inadvertently cut, that crew removed it from the IUA until the
STS
-121 crew could work on it. Piers
Sellers
and Michael
Fossum
re-routed the Trailing Umbilical System (TUS) cable
through the IUA, once it is configured safely, to allow the
MT
to be moved from worksite 4 (WS4) to worksite 5
(WS5 on the station's truss) in advance of
EVA
2.
The next objective of the spacewalk, was to test the new robotic boom as
an orbiter tile inspection or repair work platform.
For the test, first
Piers
Sellers
and then both crew members, worked on the end of the
boom. They simulated repair-related movements in at least three different
OBSS
positions. Sensors installed on the
OBSS
and imagery from various cameras provided
post-flight information to engineers that helped them evaluate the stability of
the boom.
Much of the test was dedicated to setting up tools and the
OBSS
for the movements and then reconfiguring at the
end. The movements of the spacewalkers for the tests in the three arm positions
were scheduled to take about 30 minutes each. The spacewalkers provided
comments about each movement, while the sensors in the load cell recorded
quantitative data for review following the mission.
After leaving the
Quest
airlock, Piers
Sellers
and Michael
Fossum
first safed the zenith IUA as described above. Then
they moved to the pressurized mating adapter (
PMA
)
1 to retrieve an articulating portable foot restraint (APFR) with a tool
stanchion (TS). Next, they worked their way down to Discovery's payload bay,
hand-over-hand to setup for the test. Once in the payload bay, Piers
Sellers
temporarily placed the APFR/TS on the integrated
cargo carrier (
ICC
) and Michael
Fossum
configured it.
Piers
Sellers
then continued set up by deploying a sensor, called a
load cell or instrumented worksite interface fixture (IWIF), which he installed
later on the
OBSS
. Commander Steven
Lindsey
used a laptop computer inside Discovery, with an RF
antenna installed, to activate the sensor.
Lisa
Nowak
and Stephanie
Wilson
then moved the shuttle's robotic arm so that the end
of the
OBSS
/
SRMS
hovers above the starboard sill of the payload
bay. There, Piers
Sellers
installed several safety tethers onto the
OBSS
. Lisa
Nowak
and Stephanie
Wilson
then moved the tip of the
OBSS
to just above the starboard sill of the payload
bay.
Piers
Sellers
installed the activated load cell and a portable foot
restraint attachment device (PAD). Since this was the first time that crew
members interact directly with the
OBSS
, Michael
Fossum
was on hand to physically stabilize the
OBSS
any time Piers
Sellers
is performing setup and cleanup activities with it.
Next, Piers
Sellers
and Michael
Fossum
worked together to move the APFR/TS onto the top of
the load cell now on the tip of the
OBSS
. Piers
Sellers
extended the TS and ingressed the APFR.
With setup
complete, Lisa
Nowak
and Stephanie
Wilson
maneuvered the robotic boom into the first test
position, with Piers
Sellers
riding at the end of the
OBSS
. Michael
Fossum
stayed in the payload bay and took digital photos
during the first test.
For the first position, the end of the boom is about
14 feet (4.3 meters) from the payload bay, directly above the position where
Piers
Sellers
got on the boom. Once the boom was in place, Piers
Sellers
performed several movements to simulate real
inspection or repair actions. The positions simulated movement of a crew member
on the tip of the boom during translation to, and while inspecting a potential
damage site on the bottom of the orbiter. They included Piers
Sellers
simulating taking photographs, laying back slightly
to retrieve a tool behind him, reaching for equipment in front of him, and
making positional changes to the APFR and TS.
The second position, where
Piers
Sellers
performed additional movements, had the end of the
OBSS
extending about 27 feet (8.2 meters) to the port
and aft of Discovery's payload bay. This position had the
SRMS
joints in a slightly "weaker" configuration which
should result in larger
OBSS
deflections. Piers
Sellers
went through three sets of movements similar to the
movements at the first test position. Michael
Fossum
repositioned himself in the payload bay to watch and
document the second round of tests.
Once the tests in the first position,
and second, were complete, Lisa
Nowak
and Stephanie
Wilson
moved the
OBSS
back to above the sill of the payload bay where
Michael
Fossum
was waiting. There, Piers
Sellers
moved off the APFR so Michael
Fossum
could get on. Then Piers
Sellers
hang onto the TS and both tethered themselves in
place. Lisa
Nowak
and Stephanie
Wilson
then moved the
OBSS
into an intermediate position and then the third
test position.
In the third position the end of the
OBSS
is 16 feet (4.9 meters) in front of the station's
P1
truss segment. The configuration of the
SRMS
joints provides a similar "weakness" to those of
position 2. The main difference was that both crew members were now on the tip
of the
OBSS
. During the position 3 evaluations, Michael
Fossum
made gestures similar to what Piers
Sellers
did at the first two positions with Piers
Sellers
now also on the boom. Both crew members moved
simultaneously for some of the test.
Once the movements at the third test
position were complete, Lisa
Nowak
and Stephanie
Wilson
moved the end of the
OBSS
with both Michael
Fossum
and Piers
Sellers
toward the station's
P1
truss segment for the final set of tests. At this test position Michael
Fossum
simulated repair movements on the
P1
truss structure. The
P1
truss was selected to represent a TPS damage location somewhere on the orbiter
that would need repair. This specific location was chosen because of the
SRMS
joints that are necessary to reach it. Once
again, the joints provide a "weak" configuration that allows for larger
OBSS
tip deflections. The data resulting from using a
"weaker" configuration were expected to provide the best information in order
to gauge the capability of performing a real repair from the
OBSS
. The movements performed by Michael
Fossum
simulated applying tile repair material with an
emittance wash applicator (EWA), drilling on an RCC panel, and using a spatula
with repair material on an RCC panel.
Once the testing was done in the final
OBSS
position, Lisa
Nowak
and Stephanie
Wilson
moved the arm so the spacewalkers could egress onto
Discovery's payload bay sill. With Michael
Fossum
's assistance, Piers
Sellers
had to cleanup the end of the
OBSS
by removing the APFR/TS, load cell, PAD and
safety tethers. The equipment was taken back to the airlock with the
spacewalkers. Once the
OBSS
was reconfigured, the arm was moved higher above
the payload bay out of the way.
The
second
EVA
by Piers
Sellers
and Michael
Fossum
occurred on July 10, 2006 (6h 47m) for installation of
a spare thermal control system pump on to the outside of the
Quest
Airlock and replacement of reel assembly for a cable that provides power and
data to the stations mobile transporter.
The second
EVA
consisted of installing the thermal control system's spare pump module and
replacing the nadir Trailing Umbilical System - Reel Assembly (TUS-RA). The TUS
provides power, data and video to the
MT
. During
EVA
1, the crew re-routed the zenith TUS cable thru the zenith IUA to allow the TUS
to be moved from position WS4 to WS5. Before
EVA
2, the
MT
must be moved from WS4 to WS5 because its current
position makes it difficult for the crew to change out the nadir TUS-RA.
At
the start of
EVA
2, both crew members translated down to the payload bay and prepared the pump
module for transfer. The first activity was for Michael
Fossum
and Piers
Sellers
to take the fixed grapple bar (FGB) from the
underside of the
ICC
and install it onto the pump module. The FGB
allowed Lisa
Nowak
and Stephanie
Wilson
to latch onto the pump module with the station's
robotic arm and moved it to the worksite at the external stowage platform 2 (
ESP
2) for installation. Once the FGB was installed, the crew released the pump
module from the
ICC
and lifted it up to present it to the robotic
arm.
During the arm's maneuver, Piers
Sellers
and Michael
Fossum
began preparation for removing and replacing the
TUS-RA. First, they prepared the payload bay by relocating some APFRs and
opening the TUS multi-layer insulation (MLI) cover. Then, they translated to
the starboard zero (
S0
)
truss segment, located above the
Destiny
Lab. Michael
Fossum
prepared the old TUS-RA for removal by releasing
electrical connectors and bolts, while Piers
Sellers
changed out the nadir IUA in preparation for routing
the new TUS cable.
Once complete, they both translated to
ESP
2 to install the pump module. Lisa
Nowak
and Stephanie
Wilson
presented the pump module with the robotic arm. Once
Piers
Sellers
and Michael
Fossum
had a hold, the arm released it and moved away so the
pump module could be set on
ESP
2 and bolted in place.
Next, Michael
Fossum
configured the robotic arm with an APFR and, along
with Piers
Sellers
, released and removed the old TUS from
S0
.
Michael
Fossum
, now mounted on the robotic arm, was maneuvered down
to the payload bay. Because this maneuver took some time, Piers
Sellers
translated to the payload bay and finished
preparation tasks for removal of the new TUS-RA. Once both were ready, Piers
Sellers
got into an APFR on the
ICC
and Michael
Fossum
handed Piers
Sellers
the old TUS-RA. Michael
Fossum
then maneuvered to the new TUS-RA, removed it from its
launch location and returned to Piers
Sellers
to swap the 330-pound (150 kg) TUS-RAs.
Michael
Fossum
handed Piers
Sellers
the new TUS-RA - Piers
Sellers
had a one in each hand - and then Piers
Sellers
handed Michael
Fossum
the old TUS-RA. Michael
Fossum
put the old reel assembly on the carrier and retrieved
the new one from Piers
Sellers
. Michael
Fossum
, who was still on the end of the robotic arm, took the
new TUS-RA and began to maneuver up to
S0
to install it. Piers
Sellers
completed installation of the old TUS onto its
stowage location with the flight support equipment, and then translated back up
to
S0
.
Together they installed the new TUS-RA into
S0
and routed the new cable to the nadir IUA. With the
EVA
complete, there were both a zenith and nadir TUS, assuring redundancy for
operation of the Mobile Transporter.
The
third and final
EVA
by Piers
Sellers
and Michael
Fossum
was conducted on July 12, 2006 (7h 11m) to demonstrate
on orbit heat shield repair techniques.
After leaving
Quest
,
Piers
Sellers
and Michael
Fossum
had to setup tools on the end of the station's robotic
arm,
Canadarm2
.
Piers
Sellers
installed an APFR on the end of
Canadarm2
.
Michael
Fossum
handed him supplies and tools to attach, including a
CRM bag and an Infrared camera.
Piers
Sellers
used the infrared (IR) camera as part of DTO 851 to
take about 20 seconds of IR video of RCC panels on Discovery's wing leading
edge while being transported on the end of
Canadarm2
to Discovery's payload bay.
The FLIR Systems ThermaCAM S60 Infrared Camera
is being assessed as a way to inspect RCC for damage on-orbit. Depending on how
far away the crew member is, the camera's field of view can cover 52 inches
(132 centimeters), or about two RCC panels, to 83 feet (25.3 meters), the
entire wing leading edge at a time. The camera can record temperature variances
from minus 400-degrees Celsius to 1,200-degrees Celsius. The video is recorded
at a 0.6 Hz frame rate and is saved on internal memory and then transferred to
a memory card.
Meanwhile, Michael
Fossum
travelled hand-over-hand to the cargo bay and began
setting up the worksite. The two worked side-by-side to test repair techniques
on a pallet of pre-damaged RCC samples. The pallet included twelve RCC samples.
Eight had various sized cracks and/or gouges, two were blank slates or
"palettes" to be used during repairs of the other samples, and two were
pre-damaged samples to be imaged with the IR camera. There were more samples
for the crew members to work with than what is required or expected to be
completed. The pallet was located in the aft portion of Discovery's cargo
bay.
Michael
Fossum
had to setup another APFR to position himself next to
the pallet and opened the pallet's lid. Once in the cargo bay, Piers
Sellers
got off the robotic arm to attach the CRM bag to the
inside of the pallet's lid and then got back on the arm to begin the repair
work.
The RCC crack repair tasks for DTO 848 involved using a pre-ceramic
polymer sealant impregnated with carbon-silicon carbide powder, together known
as NOAX (short for non-oxide adhesive experimental). The NOAX material is
temperature sensitive and the ideal condition for the repairs is when the
samples are between 100 and 35 degrees Fahrenheit, with the temperature
decreasing.
Therefore, the crew members were scheduled to work on the crack
repairs with the NOAX material during night portions of their orbit, beginning
the repair just after orbital sunset. Once setup for the spacewalk was
complete, if the temperature readings were acceptable, the crew began repairing
a cracked or gouged RCC sample.
For the tests, Michael
Fossum
assisted Piers
Sellers
as he used a space-hardened caulk gun to dispense the
NOAX material. Using one of three manual caulk guns in the crack repair kit, he
dispensed the material directly onto the sample. He then used one of many
spatulas, similar to a putty knife, to work the crack repair material into the
pre-damaged RCC sample mounted in the DTO pallet. Additional layers then were
added to the repair by first extruding the material onto the nearby RCC
palettes. He then used the spatula to manipulate the material onto the sample
being repaired.
Piers
Sellers
and Michael
Fossum
continued repairing the remaining cracked samples with
the NOAX material. If at least the two highest priority RCC impact damage
samples had been repaired, there was an additional task for DTO 851 for the
crew to complete. It involved taking about 60 seconds of video with the IR
camera of two damaged RCC samples on the pallet. Piers
Sellers
used the IR camera to record a temperature gradient
throughout each RCC sample itself. As with the actual RCC repair tasks, it was
preferred that the temperature is dropping. Therefore, the best imaging
occurred by Piers
Sellers
starting the imaging during direct sunlight and then
about 10 seconds later he shaded the samples to provide the desired temperature
gradient.
The astronauts also continued cargo transfers between the
shuttle, the International Space Station and the Leonardo multi-purpose
logistics module. Leonardo arrived with more than 7,400 pounds (3,357 kg) of
equipment and supplies for the station. Leonardo was returned to the payload
bay packed with more than 4,300 pounds (1,950 kg) of science experiment
results, unneeded items and trash.
Before undocking crew members also
used the robotic arm and the orbital boom sensor system to perform final
inspections of the starboard wing and shuttle nosecap for any damage that may
have been caused by orbital debris while docked with the International Space
Station. Troubleshooting of one of the Flash Evaporator Subsystem (FES) (FES
PRI B) was carried out, 'A' would be used during reentry but it is desirable to
have both functional. This was in addition to the usual extensive "checkout" of
all those systems required for reentry ensuring they were functional. The main
area of concern was
APU
-1, tests on
APU
-1 also increased confidence in its integrity to
the point where mission controllers decided to use the unit as normal for the
re-entry.
Once Discovery was ready to undock, Stephanie
Wilson
sent a command to release the docking mechanism. At
initial separation of the spacecraft, springs in the docking mechanism pushed
the shuttle away from the station. Discovery's steering jets were shut off to
avoid any inadvertent firings during the initial separation.
Once Discovery
was about two feet (61 centimeters) from the station, with the docking devices
clear of one another, Mark
Kelly
turned the steering jets back on and fired them to very slowly move away. From
the aft flight deck, Mark
Kelly
manually controlled Discovery within a tight corridor as the orbiter separated
from the station, essentially the reverse of the task performed by Steven
Lindsey
just before Discovery docked.
Discovery continued
away to a distance of about 450 feet (137.2 meters), where Mark
Kelly
initiated the first of two separation burns to fly the shuttle above the
station. A full flyaround of the station was no planned to conserve time for
further inspections of Discovery's heat shield. Once directly above the
station, Mark
Kelly
fired Discovery's jets to leave the station area. Discovery held station keep
at a distance of 40 nautical miles (74 km) from
ISS
until the late inspection imagery was reviewed and
the Mission Management Team cleared the orbiter for landing. This position
allowed Discovery the opportunity to redock to the station if
needed.