STS-133

2011 American crewed spaceflight to the ISS and final flight of Space Shuttle Discovery

The mission transported several items to the space station, including the Permanent Multipurpose Module Leonardo, which was left permanently docked to one of the station's ports. The shuttle also carried the third of four ExPRESS Logistics Carriers to the ISS, as well as a humanoid robot called Robonaut. The mission marked both the 133rd flight of the Space Shuttle program and the 39th and final flight of Discovery, with the orbiter completing a cumulative total of a whole year (365 days) in space. The mission was affected by a series of delays due to technical problems with the external tank and, to a lesser extent, the payload. The launch, initially scheduled for September 2010, was pushed back to October, then to November, then finally to February 2011.

On October 14, 2010, engineers at the launch pad first discovered a small leak in a propellant line for Discovery's orbital maneuvering system (OMS) engines. The leak was detected after they noticed a fishy smell coming from the aft of the shuttle, thought of as a sign of fuel vapor in the air. Upon inspection, the leak was found at a flange located at the interface where two propellant lines met in Discovery's aft compartment. The line carried monomethyl hydrazine (MMH) propellant, one of two chemicals (the other is an oxidizer, nitrogen tetroxide) used to ignite the OMS engines. Engineers replaced an Air Half Coupling (AHC) flight cap. However, the new cap failed to solve the problem since vapor checks still showed signs of a leak. An aspirator was activated to collect the vapor at the leak site allowing work to continue in other locations around the aft segment of Discovery. It was believed that the leak was in the crossfeed flange area – a problem with associated seals. On October 18, 2010, after an afternoon review, engineers were asked to double check the torque on six bolts around the suspected leaky flange fitting and tighten if necessary. Subsequent leak tests showed again signs of seepage, and the task of solving the issue required the draining of both the left and right OMS tanks of the shuttle and a unique in situ repair at the pad to avoid a rollback. On October 23, 2010, engineers completed the removal and replacement of the two seals on the right OMS crossfeed flange, after the education (a vacuum related procedure, used to completely clear the plumbing of the toxic MMH) of the plumbing was completed ahead of the schedule by over a day. Later, testing indicated that the new seals were properly seated and holding pressure with no signs of additional seepage. Normal pad operations commenced soon after allowing managers to press forward with the confirmation of a November 1, 2010, target launch date, with fuel reloading into the OMS tanks beginning on the morning of October 24, 2010.

On November 2, while readying Discovery for launch, engineers reported an electrical issue on the backup Main Engine Controller (MEC) mounted on Engine No. 3 (SSME 3). Earlier in the morning, engineers said that the problem had been solved, however, another glitch in the system raised concerns and additional troubleshooting was ordered. Troubleshooting followed and indicated the problem was related to "transient contamination" in a circuit breaker. NASA Test Director Steve Payne, addressing reporters, told that after troubleshooting and power cycles, the controller powered up normally. However, at the same time the problem was thought to be a non issue, an unexpected voltage drop was observed. In a Mission Management Team (MMT) meeting held later that day, managers decided to scrub the launch for at least 24 hours to work towards flight rationale.

On November 5, 2010, Discovery's launch attempt, a hydrogen leak was detected at the Ground Umbilical Carrier Plate (GUCP) during the fueling process. The plate was an attachment point between the external tank and a 17 inch pipe that carried gaseous hydrogen safely away from the tank to the flare stack, where it was burned off. All had been proceeding to plan with the tank "fast filled" during tanking, until the first leak indication was revealed. Firstly, a 33,000 ppm leak then reduced to a level below 20,000 ppm was recorded. The Launch Commit Criteria limit was 40–44,000 ppm. The leak was only being observed during the cycling of the vent valve to "open" to release the gaseous hydrogen from the tank to the flare stack. Controllers decided to stop valve cycling in order to increase the pressure and attempt to force a seal before attempting to complete the fast fill process. At this stage, the leak spiked and remained at the highest 60,000 ppm level (likely even at a higher value), indicating a serious problem with the GUCP's seal. Shuttle launch director Mike Leinbach characterized the leak as "significant," similar to what was seen on STS 119 and STS 127, although the rate was higher in magnitude and occurred earlier in the fueling process. After the day required to make the tank safe by purging remaining hydrogen gas with helium gas, NASA engineers prepared for the disconnection of the vent arm and the significant number of lines prior to taking their first look at the GUCP. On the night of November 9, technicians began disconnecting the GUCP by unhooking and lowering the hydrogen vent line. Teams performed an initial inspection of the flight seal and a quick disconnect prior to sending them to labs for thorough engineering analysis. Engineers reported an unevenly (asymmetrically) compressed internal seal and the quick disconnect hardware also seemed to have a less concentric fit than pre fueling measurements indicated. Inspections also confirmed the condition of the hardware did not match the observations documented when it was installed on the external tank inside the VAB. On the morning of November 12, teams began installing a new GUCP and completed the GUCP work over the next two days. The new plate was previously fit checked on the external tank at the Michoud Assembly Facility and yielded substantially better concentricity values than was obtained with the old and removed GUCP. Technicians took extra measurements to ensure the best possible alignment of the newly installed GUCP. Teams began installing the flight seal and quick disconnect on November 15.

Additional inspection of the tank revealed cracks in foam insulation in the flange between the intertank and liquid oxygen tank. The cracks are believed to have occurred about an hour after super cold propellants began flowing into the external tank for the November 5 launch attempt. The cracks in the tank were the first to be found at the launch pad. In December 2010, with the Shuttle still on the launch pad, a full tanking test was performed to understand that failure modes of the SOFI foam fracturing. The ET Tanking Test involved a full flight loading of the ET (External Tank) with liquid hydrogen and liquid oxygen fuels, while monitoring the ET near the SRB Thrust Beam where the fracture(s) occurred. External Tank Photogrammetry Team used two full field Optical Strain systems, specifically configured for the tests by NASA Glenn and Trilion Quality Systems. The Trilion Optical Strain systems (ARAMIS) measured the full field displacements and strains of the ET from the cryogenic fuel loading during the 6 hour test (see data images). The Trilion Optical Strain cameras were fiber optically linked to the control room in the Launch Control Center 3 miles away from the launch pad, where the data was monitored during the test. Trilion Quality Systems worked with NASA Marshall over the next week to understand the data, compare with ET computer models, allowing NASA to understand the failure modes and to be able implement the repairs. The Optical Strain patterning was still on the ET during launch on February 24, 2011, travelling with it into space. The External Tank Photogrammetry Team was, later that year, awarded the Space Flight Awareness Award, and Trilion's Tim Schmidt, the Silver Snoopy Award, by astronaut Mike Foreman. The insulation was cut away for additional inspection, revealing two additional 9 inch metal cracks on either side of an underlying structural rib called "stringer S 7 2". NASA managers then decided to cut away additional foam and observed two more cracks on a stringer known as S 6 2 adjacent to the two original cracks. They were found on the far left of removed foam on the flange area between the intertank and the liquid oxygen tank. However, these cracks appeared to have suffered less stress than the others found. No cracks were found in stringers on the right side. NASA suspected the use of a lightweight aluminum lithium alloy in the tanks contributed to the crack problem. Repairs commenced while the shuttle remained on the pad. An environmental enclosure was erected around the known damage site to facilitate the ongoing repairs and eventually to apply fresh foam insulation. On November 18, as part of the repairs, technicians installed new sections of metal, called "doublers" because they are twice as thick as the original stringer metal providing additional strength, to replace the two cracked stringers on Discovery's external tank. Scanning of the stringers on the liquid oxygen/intertank flange was completed on November 23. NASA also performed backscatter scanning of the lower liquid hydrogen/intertank flange stringers on November 29. Program managers identified the analysis and repairs that were required to safely launch the shuttle, and this analysis was reviewed at a special Program Requirements Control Board (PRCB) held on November 24. Managers announced at that meeting that the launch window available in early December would be passed up, with a new target of December 17 set, but cautioned that the launch could slip into February 2011. After reviewing the space station's December traffic model following the realigned Johannes Kepler ATV's launch date, NASA had identified a potential launch window in mid /late December 2010. The December 17, 2010, date was preferred because it would have allowed the shuttle to carry more stored oxygen to the International Space Station to help it deal with oxygen generation issues, which the crew had dealt with for several months. "What we've told the agency leadership is that clearly we're not ready for the 3 to 7 December window that's coming up next week," John Shannon, NASA's SSP manager, said in a news conference held after the special PCRB. "We'll leave the option open for a launch window for 17 December, but a lot of data has to come together to support that".

The launch date of February 24, 2011, was officially set after the Flight Readiness Review meeting on February 18, 2011. Reviews of previous problems, including the GUP vent line connection, external tank foam and external tank stringer cracks, were found to be positive. Additionally, flight rules which required a 72 hour separation between dockings at the International Space Station threatened to delay the launch by at least a day due to the delayed launch of the ESA's uncrewed Johannes Kepler ATV supply craft. Managers instead decided to press ahead with the countdown allowing for a possible stand down; had docking issues arisen with the ATV, STS 133 would have stood down for 48 hours. The Kepler ATV docked successfully at 10:59 UTC, February 24, 2011.

All times Eastern Time, first 5 are while daylight saving time was in effect (EDT), attempt 6 is during outside of daylight saving (EST). Because of this, the final "turnaround" category should be 111 days, 2 hours, 49 minutes, it is not due to automatic formatting.

Section source: NASA Press Kit and NASA TV Live These losses also occurred after aerodynamic sensitive times when debris could seriously damage the shuttle, and so were deemed non threatening. NASA's engineers accounted for the foam losses to a condition called "cryo pumping". When the external tank is loaded with liquid hydrogen, the air trapped in the foam first liquifies. During the ride into orbit, as the hydrogen level in the tank drops, it warms up and the liquefied air turns back into a gas. The pressure generated due to the state change of hydrogen can cause parts of foam in the tank to come off. Once on orbit, the crew of STS 133 opened the payload bay doors and activated the Ku band antenna for high speed communications with Mission Control. While the Ku band antenna was being activated, Alvin Drew and Pilot Eric Boe activated the Shuttle Remote Manipulator System (SRMS), also known as the Canadarm. Later in the day, imagery of the External Tank during launch was downlinked for analysis.

Flight Day 2 saw the crew of Discovery begin their preparations to dock with the International Space Station (ISS). The day started with a firing of the Orbital Maneuvering System (OMS) engine, called the NC2 burn, to help Discovery catch up to the ISS. Commander Steve Lindsey, Pilot Eric Boe and Mission Specialist Al Drew began the day performing an inspection of the Re enforced Carbon Carbon (RCC) panels with the Orbital Boom Sensor System (OBSS). Lindsey and Boe started the inspection on the starboard wing and nose cap, and continued on with the port wing; the whole survey took about six hours to complete. Drew joined up with Michael Barratt and Steve Bowen to checkout and get their two Extravehicular Mobility Units (EMUs) ready for the two spacewalks that would be conducted during the mission. Later in the day, the crew checked out the rendezvous tools to ensure they were operational. At the end of the day, another OMS engine firing, known as the NC3 burn, took place.

The orbiter docked to the ISS on Flight Day 3, marking the 13th time Discovery had visited the ISS. The docking occurred on time at 19:14 UTC. A hard mate between the two vehicles was delayed by about 40 minutes because of relative motion between the station and shuttle, thus putting the crew behind the timeline for the day. The hatches were finally opened at 21:16 UTC, and the Expedition 26 crew greeted the crew of STS 133. After the welcome ceremony and safety briefing, the crew's main task of the day was to transfer the ExPRESS Logistics Carrier 4 (ELC 4). ELC 4 was taken out of Discovery's payload bay by the Space Station Remote Manipulator (SSRMS), also known as Canadarm2, which was operated by Nicole Stott and Michael Barratt. The SSRMS handed it to the Space Shuttle Remote Manipulator System (SSRMS), which was being controlled by Boe and Drew, while the SSRMS moved to the Mobile Base System (MBS). Once there, the SSRMS took ELC 4 back from the SSRMS, and installed it at its location on the S3 truss location. ELC 4 was installed in its final location at 03:22 UTC on February 27. While the robotic transfer was going on, Bowen and Lindsey were transferring items that were needed for Flight Day 4 and the spacewalk on Flight Day 5.

On Flight Day 4, Stott and Barratt grappled the Orbiter Boom Sensor System (OBSS) using the Canadarm2 and removed it from the starboard sill of Discovery's payload bay. Once it was grappled and out of the payload bay, the Shuttle Remote Manipulator System grappled the end of the OBSS and took a handoff from the Canadarm2. The OBSS was grappled by the space station arm, because the SRMS could not reach it due to clearance issues, and it needed to be moved out of the way so that the Permanent Multipurpose Module (PMM) could be removed from the payload bay. After the OBSS handoff, the entire STS 133 crew was joined by ISS Expedition 26 commander Scott Kelly and flight engineer Paolo Nespoli for a series of in flight media interviews. The interviews were conducted with the Weather Channel, WBZ radio in Boston, Massachusetts, WSB TV in Atlanta, Georgia, and WBTV in Charlotte, North Carolina. The crew also completed more cargo transfers to and from the ISS. Throughout the day, Drew and Bowen prepared tools that they would use on their spacewalk on Flight Day 5. Later in the day, they were joined by the shuttle crew and ISS commander Kelly and Flight Engineer Nespoli, for a review of the spacewalk procedures. After the review, Bowen and Drew donned oxygen masks and entered the crew lock of the Quest airlock for the standard pre spacewalk campout. The airlock was lowered to 10.2 psi for the night. This was done to help the spacewalkers purge nitrogen from their blood and help prevent decompression sickness, also known as the bends.

Steve Bowen and Alvin Drew performed the mission's first extra vehicular activity (EVA), or spacewalk, on Flight Day 5. After waking up at 06:23 EST, the crew immediately began EVA preparations. A conference was held between the crew of the station and Mission Control at about 08:20 EST, followed by further EVA preparation work, including the depressurization of the airlock. Bowen and Drew switched their spacesuits to internal battery power at 10:46 EST, marking the beginning of EVA 1. Furthermore, a photo shoot of the ISS with multiple spacecraft docked was considered, but rejected by mission planners.

NASA began a tradition of playing music to astronauts during the Gemini program, and first used music to wake up a flight crew during Apollo 15. Each track is specially chosen, often by the astronauts' families, and usually has a special meaning to an individual member of the crew, or is applicable to their daily activities. NASA opened the selection process to the public for the first time for STS 133. The public was invited to vote on two songs used to wake up astronauts on previous missions to wake up the STS 133 crew. Flight Day Song Artist Played for Day 2 "Through Heaven's Eyes" Brian Stokes Mitchell Michael R. Barratt Day 3 "Woody's Roundup" Riders in the Sky Alvin Drew Day 4 "Java Jive" The Manhattan Transfer Steven Lindsey Day 5 "Oh What a Beautiful Morning" Davy Knowles & Back Door Slam Nicole Stott Day 6 "Happy Together" The Turtles Stephen Bowen Day 7 "Speed of Sound" Coldplay Eric Boe Day 8 "City of Blinding Lights" U2 STS 133 Crew Day 9 "The Ritual/Ancient Battle/2nd Kroykah" Gerald Fried (Composer) STS 133 Crew Day 10 "Ohio (Come Back to Texas)" Bowling for Soup STS 133 Crew Day 11 "Spaceship Superstar" Prism STS 133 Crew Day 12 Theme to "Star Trek" Voice over by William Shatner Song by Alexander Courage STS 133 Crew Day 13 "Blue Sky" (Live) Big Head Todd and the Monsters STS 133 Crew Day 14 "Coming Home" Gwyneth Paltrow STS 133 Crew