NASA Sets Out To Reinstall Engines On Fleet-Leader Discovery

NASA is embarking today on a four-day effort to reinstall engines on shuttle Discovery after removing and replacing a suspect turbopump.

The work is being done in Orbiter Processing Facility Bay No. 3 at Kennedy Space Center, where NASA's shuttle fleet-leader is being readied for a late October launch on a mission to the International Space Station. Discovery and six astronauts will haul up the Italian-built Leonardo cargo module, which will serve as a permanent storage unit at the outpost.

All three of Discovery's engines were removed last week so that a faulty Low Pressure Liquid Oxygen Turbopump could be replaced. Engineers noted during a standard torque test that the turbine in the pump was not spinning properly, so they recommended swapping it out.

The faulty pump was in Main Engine No. 1; Discovery's two other liquid-fueled main engines had to be removed first to avoid interference issues with the equipment used to do the job.

The pump is being shipped out to Pratt & Whitney Rocketdyne's Canoga Park facilities in California, where it will be inspected and tested in an effort to determine why it is not spinning properly.

A spare was delivered to KSC and installed on Engine No. 1, clearing the way for all three engines to be put back in place on Discovery. The reinstallation work is expected to be finished by by end of business on Friday.

The Low Pressure Oxidizer Turbopump is an axial-flow pump driven by a six-stage turbine that is powered by liquid oxygen. It boosts the pressure of the liquid oxygen from 100 psia to 422 psia, funneling the propellant to a High Pressure Oxidizer Turbopump. The increase in pressure enables the high-pressure pump to operate at higher speeds without running dry. The low-pressure pump, which is about 18 by 18 inches operates at about 5,150 rpm. The high-pressure pump operates at about 28,120 rpm.

A tri-engine removal after installation is a relatively infrequent operation. The last time was in May 2007 when all three engines were pulled from Atlantis in the KSC Vehicle Assembly Building. The removal in that case was required so engineers could perform inspections on main propulsion system feedlines.

NOTE ON IMAGES: Click to enlarge the top NASA photo, which shows Discovery's Main Engine No. 1 being removed from the ship in Orbiter Processing Facility Bay No. 3 last week so a suspect turbopump could be removed and replaced. The second NASA photo shows the faulty pump in the Space Shuttle Main Engine Processing Facility, which is located right next to OPF Bay No. 3. Photo credit: NASA/Jack Pfaller