Traditionally, astronauts and supplies have traveled to and from the space station via the space shuttles (now retired) and the Russian spacecrafts, Soyuz and Progress. The station, thought to cost between $35 and $100 billion, receives much of its power from a complicated solar array system. Boeing is the prime contractor for NASA for much of the station. The solar array system is roughly "38,400 square feet, which is large enough to cover eight basketball courts (94 ft x 50 ft x 8 = 37,600 square feet). The solar array surface area could cover the U.S. Senate Chamber three times over," according to Boeing. Pictured here, the space shuttle Discovery approaches the station to dock on Feb. 26, 2011.