Space Shuttle’s Second Redesigned External Tank to Ship from Michoud

NASA will ship its second redesigned Space Shuttle External Tank Saturday, March 5, from Michoud Assembly Facility, near New Orleans., marking the first step toward final launch preparations for the launch of STS-121, possibly this summer. The mission, on the Space Shuttle Atlantis, is the second test flight of the Space Shuttle following the Columbia accident.

The tank, designated ET-121, rolled out on its transporter March 4 at NASA’s Michoud Assembly Facility in New Orleans and loaded onto a covered barge for shipment to Kennedy Space Center. The trip from the Mississippi River Gulf of Mexico Outlet to Florida’s Banana River, which pours into the Atlantic Ocean, usually takes four to five days.

The first redesigned tank, ET-120, was shipped from New Orleans to Kennedy Space Center in December 2004. It will launch NASA’s STS-114 Return to Flight mission planned for May. It incorporated several safety improvements, including an improved bipod fitting that connects the tank to the Orbit; a video camera mounted on the liquid oxygen feed line to photograph liftoff; reversed bolts on the flange of the tank’s mid-section and a new process for spraying the thermal protection required there; redesign of the bellow, or “joints” for movement, along the liquid oxygen feed line, the 70-foot pipe that feeds liquid oxygen to the Main Engines; and a more defined spray procedure on the longeron, a structural support for the tank’s aft, orbiter attachment struts.

In addition to the ET-120 modifications, NASA’s second redesigned tank has been outfitted with temperature sensors and accelerometers, used to measure vibration, which will gather information about how it performs during flight.

Temperature sensors will be mounted on the tank’s two forward “bipods.” Each tank has two bipod fittings that connect the tank to the Orbiter at the Shuttle’s two forward attachment struts. These sensors will monitor the temperature of the bipod web, the flat section of the bipod located between the fitting and the attachment plate.

There also will be seven accelerometers on the tank. Three will be located in the intertank, the Tank’s midsection, near the bipods, to measure any vibration caused by changes in the aerodynamic load, or stress. The other four accelerometers will be located in the cable tray of liquid oxygen protuberance air load ramps and will be used to determine whether there is need for the ramps in future tank modifications.

“The instrumentation on ET-121 will confirm what our computer models tell us happens during launch and ascent,” said Sandy Coleman, manager of the External Tank Project, an element of the Space Shuttle Propulsion Office at NASA’s Marshall Space Flight Center in Huntsville, Ala. “Though computer models are invaluable, the information gained from an actual launch will give us an even better picture.”

During a launch, the External Tank delivers 535,000 gallons of liquid hydrogen and oxygen propellants to the three Main Engines, which power the Shuttle to orbit. The Tank is covered by a polyurethane-like foam that insulates the propellants, keeps ice from forming on the Tank’s exterior and protects its aluminum skin from aerodynamic heat during ascent. The Tank — the largest element of the Shuttle system — measures 27.6 feet wide and 154 feet tall and is the only Shuttle component that cannot be reused. The other elements include the Orbiter, the twin Solid Rocket Boosters, each consisting of four solid rocket motor segments, and the three Main Engines.

The seven-member crew of the STS-114 Return to Flight mission to the International Space Station in May is the first step in realizing the Vision for Space Exploration, which calls for a stepping stone strategy of human and robotic missions to achieve new exploration goals. The Shuttle will be used to complete assembly of the International Space Station, a vital research platform for human endurance in space and a test bed for technologies and techniques that will enable longer journeys to the Moon, Mars and beyond.

The Space Shuttle Propulsion Office at the Marshall Center manages the Tank project. Lockheed Martin Space Systems Co., in New Orleans, is the primary contractor.