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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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Technicians working on tiny fuel leak in Discovery pod
BY WILLIAM HARWOOD
STORY WRITTEN FOR CBS NEWS "SPACE PLACE" & USED WITH PERMISSION
Posted: October 18, 2010;
Updated @ 4:15 p.m. with additional torque checks/leak test ordered


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Engineers troubleshooting a small fuel leak aboard the shuttle Discovery decided Monday to carry out additional tests before more invasive and time-consuming work to replace a suspect seal, officials said.


Credit: Justin Ray/Spaceflight Now
 
After an afternoon review, troubleshooters were asked to double-check the torque on six bolts around a presumably leaky flange fitting and tighten if necessary. If subsequent leak tests show no more signs of seepage, a NASA spokeswoman said, Discovery could be cleared for launch as is.

Otherwise, engineers likely will be forced to evacuate launch pad 39A and drain the on-board propellants Wednesday before work to change out a suspect seal. NASA officials say enough contingency time remains in the processing schedule to complete the work in time for launch Nov. 1 as planned if no major problems are encountered.

The trouble involves seepage of toxic monomethyl hydrazine, or MMH, fuel at a crossfeed flange in the propellant plumbing of the shuttle's right-side orbital maneuvering system rocket pod. The shuttle is equipped with two such rocket pods, one on either side of the ship's vertical tail fin, that burn monomethyl hydrazine with an oxidizer, nitrogen tetroxide, to carry out maneuvers in orbit.

After testing over the weekend, engineers were able to trace the leak to a specific area of a large flange where two sections of propellant line come together. But it is not yet clear whether the seepage involves a loose bolt, a seal in the flange or the flange itself.

The right-side OMS pod was removed after Discovery's most recent flight in April to repair a helium isolation valve in another part of the system. After the pod was re-installed in July, leak checks were normal and no obvious loss of pressure has been noted. But insulation around the flange was found to be damp with MMH over the weekend.

Because the propellants are extremely toxic, the OMS pod tanks must be emptied and the propellant lines drained before any invasive repair work.

With Discovery in the vertical orientation at the launch pad, removing residual propellant from the lines is expected to be difficult. Even so, engineers believe they can replace the seal, if necessary, and reload the system in time to make the current launch date. Replacing the flange itself at the pad would be much more difficult, engineers say, requiring lines to be cut and welded.

As of Monday, the launch processing schedule included four days of contingency time to handle unexpected problems.

Discovery is scheduled for launch on a space station resupply mission at 4:40 p.m. EDT (20:40 GMT) on Nov. 1. If the shuttle is not off the pad by Nov. 5 or 6, the flight will be delayed at least to early December because of conflicts with other launches, already planned space station spacewalks and temperature restrictions due to the station's orbit.

Senior NASA managers plan to attend an executive-level flight readiness review at the Kennedy Space Center next Monday to review ground processing and to set an official launch date. Updates will be posted here as warranted.

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Additional coverage for subscribers:
VIDEO: ASTRONAUTS EGRESS SHUTTLE AFTER COUNTDOWN PLAY

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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