NASA began using solar power to provide renewable energy to spacecraft as early as the 1950s. In 1958, the grapefruit-sized Vanguard 1 became the world's first solar-powered satellite. Its six primitive solar cells generated one total watt of energy, allowing the satellite to send radio orbital data to Earth from outer space for more than six years. Skylab, the first American space station, was launched in 1973 and also relied on solar power to enable astronauts to live in outer space for extended periods, hosting three missions of 28, 59, and 84 consecutive days. The International Space Station is outfitted with eight solar arrays to harness the sun's energy, with each 112-foot-by-39-foot array made up of 30,000 solar cells and able to produce 120 kilowatts of energy, enough to power 40 houses, while supplying the station's research and living quarters and storing power in batteries when it passes through Earth's orbital shadow.