The mighty Titan — a pillar in American rocketry for five decades — flew into orbit for the final time Wednesday, capping a distinguished career of heavy-lifting that has spanned the nation’s space age.
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
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.
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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Additional coverage for subscribers: VIDEO:
GASEOUS HYDROGEN VENT ARM DETACHED FROM SHUTTLE PLAY
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
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
FLIGHT READINESS REVIEW SETS LAUNCH DATE PLAY
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
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
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
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
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
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
TIME-LAPSE SHOWS DISCOVERY ASCENDING IN VAB PLAY VIDEO:
TIME-LAPSE SHOWS THE MOVE TO ASSEMBLY BUILDING PLAY
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
THE HISTORY OF SHUTTLE DISCOVERY PLAY VIDEO:
THE HISTORY OF SHUTTLE ENDEAVOUR PLAY VIDEO:
THE HISTORY OF SHUTTLE ATLANTIS PLAY
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
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