Leaving Earth In this book we're taking the trip of a lifetime exploring what it's like to be an astronaut We'll learn how spacecrafts leave the Earth and travel out across the solar system and what we have learned from space exploration so far We'll also be taking a look at the challenges and dangers astronauts may face in the future BREAKING FREE The edge of space is just 60 miles 100 km straight above your head But Earth's gravity is a powerful force that pulls you and everything else down onto its surface and prevents it from leaving You will have to overcome this gravitational pull first and for that you will need a rocket Once out in space you will orbit the Earth at hundreds of miles per hour in weightless conditions in a completely airless vacuum Looking down you will be able to see the thin shell of air that surrounds Earth the atmosphere This layer of gases supports life on the surface but makes returning from space very difficult Any object entering the atmosphere at high speeds will be heated to extreme temperatures and your spacecraft will need heat shields to stop it from being burned to a crisp The Mercury Atlas 9 rocket lifted off from Cape Canaveral Florida on May 15 1963 It was piloted by astronaut Gordo Cooper who was the last American to fly a solo mission to space III
BEY O N D THE E AR TH Despite all these dangers space is an amazing place and well worth the risk The ability to put satellites in orbit has helped to shape our modern society and our robot space probes have changed our view of the solar system One day soon human colonists on the Moon and other planets will open a new stage in the history of the human race TRAVELER S TALES ESCAPE VELO CITY Rocket scientists often talk about the Earth's escape velocity which is the speed you need to achieve in order to entirely escape Earth's gravity This is roughly 7 miles per second 11 2 km sec but you don't need to travel that fast to go into orbit a couple hundred miles up An orbit is a circular or oval path that one object follows around another such as a satellite going around the Earth A spacecraft such as a space shuttle see below needs to be pushed upward with a force or thrust that's strong enough to overcome Earth's gravity and speed the vehicle up enough to go into orbit In order to put a couple pounds of material into space a typical rocket has to use 100 200 pounds 50 100 kg of
Rockets are engines that work using a principle called action and reaction The rocket’s exhaust escapes in one direction and the rocket itself is pushed the other way A rocket produces its exhaust by a process called combustion This is an explosive chemical reaction in which a fuel a solid or liquid chemical burns to produce an expanding cloud of hot gases Engines on Earth burn their fuel using oxygen from the air around us Rockets carry tanks containing a chemical called an oxidizer so that they will work in space where there is no air BLASTING INTO SPACE 6 The only practical way of getting into space is by using a chemical rocket Only these amazing engines have the power to overcome Earth’s gravity with their steady long-lasting force which starts slowly but builds up to send a spacecraft on its way to orbit and beyond Rockets This space shuttle is blasted into orbit by the combined thrust from its three main engines and two huge rocket boosters Fuel is supplied by the central rust-colored tank TRAVELER’S TALES ROCKET MAN Russian and German scientists were among the first to work out many of the principles of rocket-powered spaceflight The man who put these principles into practice was Robert Goddard an American professor of physics Until Goddard’s time rockets had been limited to glorified fireworks that used solid fuels and oxygen from the air Goddard pioneered liquid-fueled rockets that carried their own oxidizer on board His ideas were mocked by many people who did not understand how a rocket could work in space but he proved himself right when his tiny rocket Nell shown left made its first experimental flight in 1926 to a grand height of 43 feet 13 m Since Goddard’s time both liquid fuel and solid fuel rockets have made huge advances
STAGES TO ORBIT A rocket engine can produce huge amounts of thrust to overcome the pull of gravity However a rocket burns through fuel or propellant very quickly and so has to carry huge amounts to reach space To avoid carrying the excess weight of empty fuel tanks most rockets use a multistage design Several separate stages each fitted with its own engines and fuel tanks burn in sequence They are released when their fuel runs out and are then dropped back to Earth Booster stages attached to the sides of the rocket can also provide extra thrust during liftoff The space shuttle uses booster rockets to help lift it into orbit The third stage of the Saturn V rocket which took astronauts to the Moon had its own engine 7 These opening panels allowed access to the lunar module the craft that landed on the Moon
