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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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Underlying metal cracks found on Discovery's tank
BY WILLIAM HARWOOD
STORY WRITTEN FOR CBS NEWS "SPACE PLACE" & USED WITH PERMISSION
Posted: November 10, 2010


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Cracked foam insulation on the shuttle Discovery's external tank was cut away overnight, revealing serpentine cracks in an underlying structural rib, or stringer. Based on experience repairing similar cracks on other tanks, sources said, engineers believe the damage can be fixed at the pad before the next launch window opens at the end of the month.


After the cracked foam was removed overnight, engineers discovered a crack in an underlying stringer. Credit: NASA
 
Working in parallel, another team of engineers is continuing work to disassemble a leaking hydrogen vent line quick-disconnect fitting that delayed Discovery's planned launching last Friday. Replacement hardware is expected to be installed by the end of the week, but it's not clear when testing and analysis to pin down the cause of last week's leak will be complete.

In any case, NASA managers are expected to order a tanking test to make sure the new hardware is leak free before moving forward with another countdown, sources said. And that assumes the crack repair work goes well. To minimize the impact of a fueling test on other pad operations, only liquid hydrogen would be loaded into the external tank's lower section to confirm the replacement vent line attachment is working properly.

Taking advantage of the launch delay, engineers also plan to replace a circuit breaker panel in Discovery's cockpit that may have played a role in a subtle electrical glitch that triggered a delay earlier last week. Panel L4, equipped with 18 replacement breakers, is expected to be re-installed in the cockpit by early next week.


The crack in the foam insulation was found after launch was called off Friday. Credit: NASA
 
The crack in the external tank's insulation occurred just after 7 a.m. EDT Friday, about an hour into the fueling procedure and shortly before the hydrogen leak was detected. The crack, located near the top of the ribbed intertank section that separates ET-137's liquid oxygen and hydrogen tanks, is similar to a backward question mark, measuring 46 inches from end to end.

Overnight, engineers at pad 39A cut away the foam insulation in the area of the crack, revealing underlying cracks in a structural stringer that is part of the vertical ribbing that makes up the intertank section. The cracks appear to run in a wavy line from bolt to bolt in the stringer.

It is not yet clear what caused the underlying cracks. They presumably could have been triggered by temperature-induced stress as the tank was loaded with supercold liquid oxygen and hydrogen rocket fuel. But a similar crack was found in ET-138, scheduled for use by the shuttle Atlantis next summer, and that tank has not yet been subjected to cryogenic temperatures. The cracks may be related to the use of lightweight materials in the latest generation of tanks.

The crack in Atlantis' tank was repaired and engineers likely will follow a similar approach with Discovery's tank, possibly installing so-called doublers to reinforce the damaged stringer or a replacement section. Assuming management clearance to proceed and no other problems, fresh foam will be sprayed on, cured and sanded to match the surrounding insulation.


Credit: Justin Ray/Spaceflight Now
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The year's final shuttle launch window opens Nov. 30 and closes Dec. 5 or 6. If Discovery is not off the pad by then, the flight will slip to the end of February because of conflicts with other space station missions; a prohibition against flying over New Year's to avoid possible year-end rollover issues with the shuttle's software; and because of temperature constraints related to the space station's orbit.

Whether Discovery's launch team can complete the leak repair and fix the crack damage in time for a Nov. 30 liftoff is not yet known, but engineers are cautiously optimistic. The schedule is considered "success oriented," however, and there is little margin for error.

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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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