From Earth to Orbit

Getting the orbiter into space follows a familiar pattern tested by earlier manned flights and hundreds of unmanned ones simply dropping off parts of the vehicle, as they run out of fuel, while the rest continues into orhit. 

The propellant looks and feels like the hard rubber of a typewriter eraser. It is a mixture of aluminum powder as fuel, aluminum perchlorate powder as an oxidizer, a dash of iron oxide as a catalyst to speed the burning rate, and a polymer binder that also served as a fuel. It is not sensitive to ignition by static, friction, or impact and it will not detonate during storage. 

After burning out, the solid rocket boosters are cut loose from the external tank by electrically fired explosive devices and are moved away by small rocket separation motors, four near the nose of each and four aft, fired by command from the orbiter. The spent boosters coast upward and then fall earthward for almost four minutes, reaching a speed of 2900 mph before being slowed by atmospheric drag. From about 3 miles each is lowered by a succession of parachutes to a splashdown of about 60 mph. 

Since the empty rocket enters the water with the nozzle down, air is trapped in the upper end to float it upright until one of two recovery vessels, summoned by a radio beacon and flashing light, attaches lines to tow it back to the launch center. There the booster is taken apart and the rocket segments are shipped to the Utah factory, where they are cleaned out, inspected for cracks, pressure-tested, relined, reloaded, and reshipped to the site. There the booster is refurbished and reassembled to fly again. 

The second element of the shuttle that is discarded during ascent to orbit, and the only major part not used again, is the external tank. As tall (153 feet) as a 15-story building and as big (27.5 feet in diameter) as a farm silo, the tank contains the liquid hydrogen and liquid oxygen that fuel the shuttle s three main engines in the stern of the orbiter. The external tank forms the backbone of the entire vehicle during launch. 

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Bryan Palaszewski s summary described the fiendishly difficult challenges to making these otherworldly materials in usable quantities, but also some of the promises of atomic hydrogen Modern experiments use nanogram samples of atomic hydrogen, whereas up to many hundred tons may be required for each launch from Earth to orbit, he wrote. 

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