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The Mission




Orbiter: Discovery
Mission: STS-133
Payload: Leonardo
Launch: Feb. 24, 2011
Time: 4:53 p.m. EST
Site: Pad 39A, Kennedy Space Center
Landing: March 9 @
11:57 a.m. EST
Site: KSC's Shuttle Landing Facility

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Apparent seal problem found in leaking shuttle vent line
BY WILLIAM HARWOOD
STORY WRITTEN FOR CBS NEWS "SPACE PLACE" & USED WITH PERMISSION
Posted: November 11, 2010;
Updated @ 12:25 p.m. with foam repair plan and adding NASA statement


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A leaking hydrogen vent line attachment fitting on the side of the shuttle Discovery's external tank was removed and disassembled overnight, revealing an unevenly compressed internal seal, engineers reported. The quick-disconnect hardware also may have a less concentric fit than pre-fueling measurements indicated. An analysis is underway to determine if the defects are responsible for the gaseous hydrogen leak that grounded Discovery last Friday.


At pad 39A, a worker begins to remove the ground umbilical carrier plate's 7-inch quick disconnect. Credit: NASA
 
A replacement ground umbilical carrier plate, or GUCP, was previously fit-checked on Discovery's tank during its assembly and measurements indicated a better fit. Engineers plan to carry out a detailed comparison of the two mounting plates before deciding how to proceed.

But barring any other surprises, they likely will be cleared to install the replacement GUCP on Discovery's tank. A meeting is scheduled for Friday to discuss an expected fueling test to make sure the vent line is leak free under cryogenic conditions.

In the meantime, another team of engineers is refining plans for repairing a structural brace on the side of the tank that experienced two cracks during Discovery's fueling Friday. The defects were found after engineers cut away cracked foam insulation covering a vertical stringer, part of the ribbed structure of the compartment that separates the liquid hydrogen and oxygen tanks.

Based on past experience with a similar crack on external tank 138, scheduled for use by the shuttle Atlantis next summer, engineers believe they can repair Discovery's tank, ET-137, by attaching a so-called doubler on a replacement section of bracing. Fresh foam insulation can then be applied and shaped to fit.

In a statement posted on NASA's web site Thursday, the agency said the cracks may be the result of using a lightweight aluminum-lithium alloy in the latest generation of external tanks.

"While the material is stronger and lighter in weight, it is more brittle and has resulted in increased cases of cracked stringers in the areas noted," the statement said. "The cracked stringer section matches well with the area of foam that cracked, which indicates the stringer crack was the root cause of the foam crack.

"Analysis shows the intertank has sufficient structural capability for the launch and ascent environments with the cracks in a single stringer," the statement said. "Although the foam was firmly attached to the damaged structure, it is undesirable to launch in this configuration. This area is clearly visible during the pre-launch inspections and would have been detected by the final inspection team."


After the cracked foam was removed overnight, engineers discovered a crack in an underlying stringer. Credit: NASA
 

To fix the cracks, engineers likely will cut out the damaged section of the stringer and replace it with another piece that exactly matches the removed section. The doubler then will be attached to add additional strength followed by an application of BX foam. The insulation will require four days to cure.

"Exact schedules and repair options still are being evaluated," NASA said. "Engineers will meet Friday to discuss the status of the three repair activities underway, the external tank stringer and foam repair, the ground umbilical carrier plate and the cockpit panel L4 removal and replacement."

The latter is a circuit breaker panel in Discovery's cockpit that may be responsible for a subtle electrical glitch blamed for an earlier launch delay last week. While the system appears sound, NASA managers decided to replace the panel while the other repair work is underway.

The engineering community is hopeful the repair work can be completed before the opening of the year's final shuttle launch window Nov. 30.


The ground umbilical carrier plate's 7-inch quick disconnect is removed from the external fuel tank. Credit: NASA
 


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Spaceflight Now Plus
Additional coverage for subscribers:
VIDEO: GASEOUS HYDROGEN VENT ARM DETACHED FROM SHUTTLE PLAY

VIDEO: STS-133 MISSION PREVIEW MOVIE PLAY | HI-DEF
VIDEO: SHUTTLE DISCOVERY CREW BIOGRAPHIES PLAY | HI-DEF
VIDEO: ISS EXPEDITION 25-26 PREVIEW MOVIE PLAY | HI-DEF
VIDEO: SPACE STATION CREW BIOGRAPHIES PLAY | HI-DEF

VIDEO: POST-SCRUB NEWS BRIEFING ON LEAK PLAY
VIDEO: GASEOUS HYDROGEN LEAK SCRUBS LAUNCH PLAY | HI-DEF
VIDEO: BAD WEATHER DELAYS DISCOVERY LAUNCH PLAY
VIDEO: ELECTRICAL ISSUE NO LONGER A CONCERN FOR DISCOVERY PLAY
VIDEO: LAUNCH POSTPONED BY ELECTRICAL CONCERN PLAY
VIDEO: TUESDAY MORNING'S COUNTDOWN STATUS CHECK PLAY
VIDEO: DISCOVERY'S PRE-LAUNCH NEWS CONFERENCE PLAY
VIDEO: COUNTDOWN PREVIEW BRIEFING AND WEATHER FORECAST PLAY
VIDEO: ANOTHER 24-HOUR DELAY ORDERED TO FINISH REPAIRS PLAY
VIDEO: LAUNCH DELAYED 24 HOURS BY LEAK REPAIRS PLAY

VIDEO: ASTRONAUTS ARRIVE FOR LAUNCH PLAY | HI-DEF

VIDEO: FLIGHT READINESS REVIEW SETS LAUNCH DATE PLAY

VIDEO: SHUTTLE AND STATION PROGRAM BRIEFING PLAY
VIDEO: THE STS-133 MISSION OVERVIEW PRESENTATIONS PLAY
VIDEO: PREVIEW BRIEFING ON MISSION'S SPACEWALKS PLAY
VIDEO: IN-DEPTH BACKGROUND ON ROBONAUT 2 HUMANOID PLAY
VIDEO: THE ASTRONAUTS' PRE-FLIGHT NEWS BRIEFING PLAY

VIDEO: PAYLOAD BAY DOORS CLOSED FOR LAUNCH PLAY | HI-DEF
VIDEO: CREW LEAVES KSC FOR TRIP TO HOUSTON PLAY | HI-DEF
VIDEO: ASTRONAUTS INSPECT THE PAYLOAD BAY PLAY | HI-DEF
VIDEO: SHUTTLE EVACUATION PRACTICE PLAY | HI-DEF
VIDEO: ASTRONAUTS EGRESS SHUTTLE AS SEEN LIVE PLAY
VIDEO: ASTRONAUTS BOARD DISCOVERY PLAY | HI-DEF
VIDEO: SUN RISES ON LAUNCH PAD 39A PLAY | HI-DEF
VIDEO: LAUNCH DAY REHEARSAL BEGINS PLAY | HI-DEF
VIDEO: COMMEMORATIVE WALL SIGNING IN VAB PLAY | HI-DEF
VIDEO: CREW BRIEFED ON EMERGENCY PROCEDURES PLAY | HI-DEF
VIDEO: IN SHUTTLE TRAINING AIRCRAFT'S COCKPIT PLAY | HI-DEF
VIDEO: TEST-DRIVING AN EMERGENCY ARMORED TANK PLAY | HI-DEF

VIDEO: PRE-LAUNCH INTERVIEW WITH STEVE LINDSEY PLAY
VIDEO: PRE-LAUNCH INTERVIEW WITH ERIC BOE PLAY
VIDEO: PRE-LAUNCH INTERVIEW WITH AL DREW PLAY
VIDEO: PRE-LAUNCH INTERVIEW WITH TIM KOPRA PLAY
VIDEO: PRE-LAUNCH INTERVIEW WITH MIKE BARRATT PLAY
VIDEO: PRE-LAUNCH INTERVIEW WITH NICOLE STOTT PLAY

VIDEO: PAYLOADS INSTALLED INTO DISCOVERY PLAY | HI-DEF
VIDEO: MISSION PAYLOADS ARRIVE AT LAUNCH PAD PLAY | HI-DEF
VIDEO: CANISTER HAULING PAYLOADS TURNED UPRIGHT PLAY | HI-DEF
VIDEO: MODULE HOISTED INTO SHIPPING CANISTER PLAY | HI-DEF
VIDEO: WEIGHING NEW SPACE STATION MODULE PLAY | HI-DEF

VIDEO: GANTRY PLACED AROUND DISCOVERY PLAY | HI-DEF
VIDEO: SHUTTLE ATLANTIS REACHES PAD 39A PLAY | HI-DEF
VIDEO: CROWDS WATCH DISCOVERY'S FINAL ROLLOUT PLAY | HI-DEF

VIDEO: SHUTTLE HOISTED FOR ATTACHMENT TO TANK PLAY | HI-DEF
VIDEO: CRANE ROTATES THE ORBITER VERTICALLY PLAY | HI-DEF
VIDEO: DISCOVERY DEPARTS ITS HANGAR PLAY | HI-DEF

VIDEO: TIME-LAPSE SHOWS DISCOVERY ASCENDING IN VAB PLAY
VIDEO: TIME-LAPSE SHOWS THE MOVE TO ASSEMBLY BUILDING PLAY

VIDEO: DISCOVERY'S MAIDEN FLIGHT: FIRST TRIP TO VAB PLAY
VIDEO: DISCOVERY'S MAIDEN FLIGHT: ROLLOUT TO PAD 39A PLAY
VIDEO: DISCOVERY'S MAIDEN FLIGHT: TEST-FIRING ENGINES PLAY
VIDEO: DISCOVERY'S MAIDEN FLIGHT: ASSORTED VIEWS OF FRF PLAY

VIDEO: THE HISTORY OF SHUTTLE DISCOVERY PLAY
VIDEO: THE HISTORY OF SHUTTLE ENDEAVOUR PLAY
VIDEO: THE HISTORY OF SHUTTLE ATLANTIS PLAY

VIDEO: INSPECTION OF THE MISSION PAYLOADS PLAY | HI-DEF
VIDEO: ROBONAUT ARRIVES AT KENNEDY SPACE CENTER PLAY | HI-DEF
VIDEO: SPACE STATION'S SPARE THERMAL RADIATOR PLAY | HI-DEF
VIDEO: BLANKETING LEONARDO WITH INSULATION PLAY | HI-DEF
VIDEO: RACK INSERTED INTO LEONARDO FOR LAUNCH PLAY | HI-DEF
VIDEO: LEONARDO RETURNS FROM ITS PREVIOUS FLIGHT PLAY | HI-DEF
VIDEO: STATION'S SPARE PARTS DEPOT ARRIVES PLAY | HI-DEF

VIDEO: ORBITER'S PAYLOAD BAY CLOSED FOR ROLLOUT PLAY | HI-DEF
VIDEO: ASTRONAUTS VISIT THEIR SPACECRAFT PLAY | HI-DEF
VIDEO: CREW INSPECTS LEONARDO MODULE PLAY | HI-DEF
VIDEO: DISCOVERY RECEIVES ITS MAIN ENGINES PLAY | HI-DEF
VIDEO: FUEL TANK MATED TO SOLID ROCKET BOOSTERS PLAY | HI-DEF
VIDEO: HOISTING FUEL TANK INTO CHECKOUT BAY PLAY | HI-DEF
VIDEO: EXTERNAL FUEL TANK UNLOADED FROM BARGE PLAY | HI-DEF
VIDEO: MISSION'S FUEL TANK ARRIVES AT SPACEPORT PLAY | HI-DEF

VIDEO: POST-FLIGHT DESERVICING: OMS POD PLAY | HI-DEF
VIDEO: POST-FLIGHT DESERVICING: OBSS BOOM PLAY | HI-DEF
VIDEO: POST-FLIGHT DESERVICING: ENGINES PLAY | HI-DEF
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