Houston, we have lift off!
All week long for World Space Week, we will be posting exclusive excerpts from Chris Impey and Holly Henry’s new book, Dreams of Other Worlds: The Amazing Story of Unmanned Space Exploration. Each day will include an excerpt from a different chapter(s) about a different unmanned spacecraft, along with a picture of the craft that doubles as an iPhone background!
Today we have two excerpts. The first is from Chapter 4, and our excerpt does its best to describe exactly how far away the Voyager spacecrafts are, and how completely wild that is. The second excerpt is from Chapter 5, which describes the way in which Cassini travels around Saturn without getting sucked into its gravitational pull.
Tomorrow will bring another chapter and another adventure, so stay tuned!
To see why these spacecraft represented such a leap in our voyaging through space, consider a scale model of the Solar System where the Earth is the size of a golf ball. On this scale, the Moon is a grape where the two objects are held apart with outstretched arms. That gap is the farthest humans have ever traveled, and it took $150 billion at 2011 prices to get two dozen men there. Mars on this scale is the size of a large marble at the distance of1,100 feet at its closest approach. As we’ve seen, it took an arduous effort spanning more than a decade before NASA successfully landed a probe on our nearest neighbor. A very deep breath is needed to explore the outer Solar System. In our scale model, Jupiter and Saturn are large beach balls 1.5 and 3.5 miles away from Earth, respectively, and Uranus and Neptune are soccer balls 7 and 12 miles from the Earth. This large step up in distance was a great challenge for spacecraft designers and engineers. On this scale, the Voyager 1 and 2 spacecraft are metallic “motes of dust” 48 and 37 miles from home, respectively.
Over its core mission, Cassini orbited Saturn 140 times. To see Saturn, its rings, its largest moons, and its magnetosphere from all conceivable angles, Cassini is using its rockets and seventy gravity-assist flybys of Titan to tweak its orbit size, period, velocity, and inclination from Saturn. As the largest moon, Titan isthe most useful in “steering” Cassini around the Saturnian system. Each Titan flyby is engineered to return Cassini into the proper trajectory for its next Titan flyby. Encounters with other moons are performed opportunistically with what’s called a targeted flyby. About fifteen are planned by the end of the mission, half to the intriguing small moon Enceladus. From 2004 through 2011, Cassini did a dizzying hundred flybys, with another dozen completed in 2012. NASA hosts a clock counting down the time until the next swooping visit to a moon and coyly calls these “Tour Dates” to appeal to a younger generation.26 By clever planning, NASA engineers have doubled the length of the mission even though just a quarter tank of fuel remains.Think you know all about these missions? Take our quiz and find out!
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