It was unclear Friday whether an ongoing engineering analysis can be completed in time to give Endeavour and its crew a green light for a launch attempt Monday.
Said NASA Test Director Doug Lyons: "Its really too early to say."
Heres the situation:
Inspectors earlier this week found unusual wear on a metal alloy seal within a high-pressure turbopump on one of the three main engines that helped propel Discovery on a mission to repair NASAs Hubble Space Telescope.
The pump performed normally during Discoverys flight and its telescope-repair crew never was in danger, NASA officials said. But the damage found within Discoverys pump is considered greater than normal wear and tear.
"In this case, they saw a little more rubbing or scoring than they are used to seeing," said NASA Test Director Doug Lyons.
The seal is one of six that direct hot gases through the turbopump to increase engine efficiency. Inspections with a camera-tipped device known as a boroscope showed that turbine blades within the pump had cut a small groove in the seal.
A seal failure could trigger an engine shutdown in flight, forcing an astronaut crew to attempt a risky and unprecedented emergency landing either at KSC, or runways in Spain or North Africa. In a worst-case scenario, its conceivable that a seal failure could lead to a Challenger-like catastrophe in flight.
Consequently, mission managers ordered an extra round of extensive inspections to the turbopump seal in question. The pump was shipped to its California manufacturer, where it is being disassembled. The suspect seal then will be thoroughly inspected.
In the meantime, NASA engineers are reviewing all records from the manufacture, test and processing of the turbopump seals on Endeavours three engines.
"It certainly is a key component of the pump, and thats why were taking the extra precaution to go and do this thorough evaluation to make sure that while we dont think there is anything of significance there, we want to make sure were not overlooking anything," Lyons said.
About the size of a car engine, the pumps deliver as much horsepower as 28 locomotives. The main shaft within the pumps rotate at 37,000 rotations per minute and the discharge pressure from them could send a column of rocket fuel 36 miles into the air.
A detailed report on the situation will be presented to mission managers during a meeting now scheduled for 2 p.m. EST Saturday.
"Until that happens, [the pump problem] is a constraint to launch," Lyons said.
While the turbopump review is ongoing, mission managers also will be keeping a close eye on the weather.
The forecast for a Monday launch attempt is favorable. Shuttle weather officer Ed Priselac said there is a 70 percent chance conditions will be acceptable for flight.
The only concern: A chance of thick, electrically charged clouds that could trigger destructive bolts of lightning along the shuttles flight path.
NASA will have launch opportunities on both Monday and Tuesday. But a delay beyond those days would force NASA to postpone the flight until February 8 or 9.
The reason: Two rocket launches already are booked on the Air Force Eastern Range next week.
A Lockheed Martin Atlas rocket is scheduled to launch a commercial communications satellite February 3 and also has February 4 booked on the range for a backup launch opportunity.
A Boeing Delta rocket, meanwhile, is scheduled to launch four cellular telephone satellites on February 6 and also has the next day booked on the range.
A widespread network of ground stations, the range provides rocket tracking and safety services for all launches from Floridas Space Coast. It typically takes 36 to 48 hours to reset range systems between launches of different vehicles.
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