So far it is the only spacecraft to have made such journeys. In 1986 Voyager 2 became the first spacecraft to fly past Uranus three years later it passed Neptune. Not a bad record, all in all, considering that the Voyager missions were originally planned to last just four years.Įarly in their travels, four decades ago, the Voyagers gave astonished researchers the first close-up views of the moons of Jupiter and Saturn, revealing the existence of active volcanoes and fissured ice fields on worlds astronomers had thought would be as inert and crater-pocked as our own moon. They are the first human-made objects to do so, a distinction they will hold for at least another few decades. And they have crossed into interstellar space, according to our best understanding of the boundary between the sun's sphere of influence and the rest of the galaxy.
They have traveled farther and lasted longer than any other spacecraft in history. After nearly 45 years in space, they are still functioning, sending data back to Earth every day from beyond the solar system's most distant known planets. Voyager 1 and Voyager 2, identical in every detail, were launched within 15 days of each other in the summer of 1977. Credit: NASA/JPL-CaltechĪs it turned out, NASA would build two space vehicles to take advantage of that once-in-more-than-a-lifetime opportunity. The spacecraft lifted off on August 20, 1977. READY FOR LAUNCH: Voyager 2 undergoes testing at NASA’s Jet Propulsion Laboratory before its flight ( left). To reach the planets while the lineup lasted, a spacecraft would have to be launched by the mid-1970s. There was just one catch: the alignment happened only once every 176 years. Flandro calculated that the repeated gravity assists, as they are called, would cut the flight time between Earth and Neptune from 30 years to 12. This coincidence meant that a space vehicle could get a speed boost from the gravitational pull of each giant planet it passed, as if being tugged along by an invisible cord that snapped at the last second, flinging the probe on its way. Using a favorite precision tool of 20th-century engineers-a pencil-he charted the orbital paths of those giant planets and discovered something intriguing: in the late 1970s and early 1980s, all four would be strung like pearls on a celestial necklace in a long arc with Earth. Flandro, who was working part-time at NASA's Jet Propulsion Laboratory in Pasadena, Calif., had been tasked with finding the most efficient way to send a space probe to Jupiter or perhaps even out to Saturn, Uranus or Neptune. It was 1965, and the era of space exploration was barely underway-the Soviet Union had launched Sputnik 1, the first artificial satellite, only eight years earlier. The first person to call attention to it was an aeronautics doctoral student at the California Institute of Technology named Gary Flandro. For a while the rare planetary set piece unfolded largely unnoticed. Some 60 years ago they were slowly wheeling into an array that had last occurred during the presidency of Thomas Jefferson in the early years of the 19th century. In this case, the stars were actually planets-the four largest in the solar system.
If the stars hadn't aligned, two of the most remarkable spacecraft ever launched never would have gotten off the ground.
0 kommentar(er)
