Flying devices called rockets come in many sizes, from simple fireworks to the engines that are used to launch missiles, satellites, and spacecraft. The vehicles driven by rockets are often called rockets themselves. How rockets workLike jet airplanes, rockets are jet-propelled. All jet-propelled vehicles rely on a chemical reaction called combustion to provide the force to move them through the air. A fuel onboard the craft is mixed with oxygen. The combustion occurs when that mixture is ignited, or set on fire. The fuel burns in a chamber with an open end. As the fuel burns it lets off hot gas, which shoots out the opening. The force of the gas moving backward pushes the vehicle forward. Jet airplanes rely on oxygen from the air, but rockets carry both the fuel and their own oxygen supply. This makes rockets valuable in outer space, where there is no oxygen. Rocket fuel can be liquid or solid. The space shuttle uses both types of fuel in its five main rocket engines. Its two solid-fuel booster rockets launch the shuttle into space. Once in space, the shuttle's three liquid-fuel rocket engines allow it to move in and out of orbit. HistoryRockets in ChinaRockets may have been first used in 13th-century China. The Chinese had probably used gunpowder for about a thousand years before that time. They made rockets by filling bamboo cases with gunpowder. When they lit the gunpowder, it exploded. The gas from the explosion sent the rocket into the air. The Chinese used rockets during religious ceremonies. The noise of the rockets was believed to frighten off evil spirits. The Chinese also used rockets as weapons. They shot rockets at Mongol invaders, who called the rockets “fire arrows.” Rockets as weaponsThe use of rockets as weapons soon spread from China to Europe. The development of guns, however, slowed the development of better rockets until the 18th century. At that time a prince in India started to use metal cases for rockets. The metal cases made them more stable and effective. Rocket technology continued to improve. It spread throughout Europe and to North America. Rockets were used as weapons in many 19th- and 20th-century wars, especially World War II. Rockets in space travelIn the late 19th century a Russian scientist named Konstantin E. Tsiolkovsky proposed the idea that rockets could be used to travel into space. Tsiolkovsky was influenced by the stories of space travel by the French writer Jules Verne. Tsiolkovsky knew that enormous power would be needed to carry human beings beyond Earth's pull of gravity. He did not actually build rockets, but his theories about rockets remain in use today. Robert H. Goddard, a U.S. engineer, built the first liquid-fuel rocket in 1925. The Soviet Union launched the first rocket into space. The spacecraft, called Sputnik 1, entered space in October 1957. Rockets carried dogs and monkeys into space until humans felt ready to make a space trip themselves. By 1969 rockets had carried men to the moon. (See also space exploration.) |