The task of placing satellites into orbit has proven formidable, and current technology dictates that rockets be used to access space. A rocket is a cylindrical metal object containing inflammable material, which, when ignited, propels the rocket to a significant height or distance. Rocket-powered vehicles are quite different from jet aircraft, in that jets use the atmosphere as a source of oxidizer (oxygen in the air) with which to burn the fuel. Rocket-propelled vehicles must carry along all propellants (both fuel and oxidizer).
Pre-Space Age Rocketry Developments
Many centuries ago the Chinese first employed crude rockets using solidified propellants to scare their enemies with the resulting loud noises and flashing overhead lights. Later, rockets became popular for displays and celebrations. Early devices, however, were crude, used low-energy propellants, and were largely uncontrollable. It was not until the 1900s that major technological advances in rocketry were realized.
Around the turn of the twentieth century, Konstantin Tsiolkovsky, a Russian schoolteacher, discovered the fundamental relationship between the amount of propellant needed in a rocket and the resulting change in speed. This remains the most fundamental relationship of rocketry and is referred to as the "rocket equation." In the 1920s American physicist Robert H. Goddard designed and built the first liquid-propelled rocket motor and demonstrated its use in flight. This was a significant step toward the development of modern missiles and space launchers.
The onset of World War II (1939-1945) created a sense of urgency in advancing the development and deployment of long-range, rocket-propelled artillery projectiles and bombs. In both Germany and the United States major efforts were begun to create rocket-propelled guided bombs, that is, missiles. By 1944 operational V-2 missiles were being launched by Germany toward England. Although these were the first successfully guided bombs, they lacked good terminal guidance and usually missed their primary targets. They were, however, very effective as instruments of mass intimidation.
After the war, one group of German rocket engineers and scientists defected to the United States and another to the Soviet Union. Wernher von Braun led the group that went to the United States. The mission of these scientists was to continue work on missile technology, and by the 1950s, the V-2 had been improved and transformed into a variety of missiles. In orderto create an intercontinental ballistic missile (ICBM) that could travel several thousand miles, however, improved guidance systems and multistage booster designs were needed, and these two areas of technology became the focus of 1950s rocketry research. Precise guidance systems ensure accurate trajectories and precision targeting, while two-stage vehicles can overcome the pull of Earth's strong gravity and low-propellant energies to achieve great distances. These same technologies were needed for orbital launcher vehicles.
Rocketry Advances During the Late Twentieth Century Space Age
When the Soviets launched the first artificial satellite in 1957 (Sputnik 1), the United States quickly followed by modifying its ICBM inventory to create orbital launchers, and the "space race" between the two countries was on in earnest. By 1960 both the United States and the Soviet Union were producing launch vehicles at will. In 1961 President John F. Kennedy challenged America to send humans, before the end of the decade, to the surface of the Moon and return them safely. As amazing as it seemed at the time, two American astronauts, Neil Armstrong and Buzz Aldrin, walked on the Moon in July 1969. By the end of Project Apollo, in 1972, a total of twelve astronauts had walked on the lunar soil and returned safely to Earth, and the United States was well established as the dominant spacefaring nation.
During the 1960s and 1970s both the Soviet Union and the United States developed several families of space launchers. The Soviet inventory included the Kosmos, Proton, Soyuz, and Molniya, and the U.S. inventory included the Titan, Atlas, and Delta. In terms of the number and frequency of satellite launches, the Soviets were far more prolific, until the breakup of the Soviet Union in 1991. Whereas the Soviets focused on putting large numbers of relatively crude satellites in orbit, the United States focused on sophistication and reliability. Thus, the West was very successful in collecting a good deal more science data with fewer satellites.
Early in the 1970s President Richard Nixon approved the development of the Space Transportation System, better known as the space shuttle. This was to be a reusable system to replace all U.S. expendable launch vehicles . Thus, when the shuttle started flying in 1981, production lines for the Delta and Atlas boosters were shut down. They stayed shut down until the 1986 Challenger disaster.* At that point it became clear that expendables were still needed and would be needed for a long time to come. By 1989 the shuttle and several expendables were back in business. The three-year U.S. launch hiatus, however, permitted other countries to enter the commercial launcher business. The most prominent of these is the European Space Agency's launcher family, Ariane, which launches roughly 40 percent of the world's largest communications satellites. Other competitors in the marketplace include Russia, Ukraine, China, and Japan. Even Israel, Brazil, and India have been active in developing and launching small booster vehicles.
The Future of Rocketry in the Twenty-First Century
As the twenty-first century begins, there are more than twenty families of expendable launchers from Europe and eight countries outside Europe. Nevertheless, there remains only one operational reusable vehicle, the space shuttle. The high cost of space access continues to propel the launch industry toward better solutions. Thus, new vehicles are expected to be developed in the future, including a few more expendables and a new generation of reusables . While the new expendables should offer some relief in terms of launch prices, reusable vehicles hold the promise for the significant cost reductions that are needed for extensive expansion of applications, such as space tourism. In pursuit of this objective, a half-dozen companies are trying to develop a fully reusable vehicle. Some of them propose to build a single-stage system in which the entire vehicle travels from the launch pad all the way to orbit, separates from the satellite, and returns to the launch site. Others propose two-stage vehicles in which a booster/ orbiter combination leave the launch pad together and return separately. By 2010, at least one of these systems could be operating.
see also Aldrin, Buzz (volume 1); Apollo (volume 3); Armstrong, Neil (volume 3); Goddard, Robert Hutchings (volume 1); Launch Vehicles, Expendable (volume 1); Launch Vehicles, Reusable (volume 1); Reusable Launch Vehicles (volume 4); Space Shuttle (volume 3); Tsiolkovsky, Konstantin (volume 3); von Braun, Wernher (volume 3).
Marshall H. Kaplan
Anderson, John D., Jr. Introduction to Flight. New York: McGraw-Hill, 1978.
Harford, James. Korolev: How One Man Masterminded the Soviet Drive to Beat America to the Moon. New York: John Wiley & Sons, 1997.
Heppenheimer, T. A. Countdown: A History of Space Flight. New York: John Wiley &Sons, 1997.
Isakowitz, Steven J., Joseph P. Hopkins Jr., and Joshua B. Hopkins. International Reference Guide to Space Launch Systems, 3rd ed. Reston, VA: American Institute of Aeronautics and Astronautics, 1999.
*On January 28, 1986, space shuttle Challenger was destroyed by a technical malfunction approximately 72 seconds after lift-off.