At 9:28 p.m. EST, NASA started to fill the external tank attached to Discovery with liquid hydrogen and liquid oxygen.
The tank is used to fuel the shuttles three main engines weighing at 58,500 pounds and 1,668,500 pounds after it is filled with the propellants. The tank estimates at three hours to complete fueling.
The external tank is known as the “backbone” for the shuttle during launch, holding a structural support with the solid rocket boosters and orbiter. It is the only unusable module in the shuttle mission. At an approximate of 8.5 minutes after reaching orbit with all propellants used, the tank disintegrates in the atmosphere and the remainder falls into the ocean.
The external tank is manufactured at NASA’s Michoud Assembly Facility in New Orleans by Lockheed Martin Space Systems and takes about a month to prepare.