Launch Vehicles, Expendable

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Launch Vehicles, Expendable

Expendable launch vehicles (ELVs) are rockets that carry satellites, people, and space probes but are not recovered or reused. These rockets are expendable, meaning that they are thrown away after their flights are completed. Expendable rockets can take many forms, but the most commonly used ones are powered by either liquid fuel or solid fuel and use multiple stages to propel their cargoes of spaceships, probes, or satellites into outer space.

Each of the rocket's stages consists of a self-contained rocket engine or motor and the fuel such as hydrogen, kerosene, or a solid fuel that looks a lot like the eraser on a pencil. Along with the engine and fuel are tanks to hold the materials, lines and pumps, and electrical systems to move the engine while in flight. Once the fuel in the stage has been used up, the stage is usually dropped away and the next stage ignited. These rockets continue to burn stage by stage until the right altitude or speed for its designated space mission has been reached.

Evolution from Military Missiles

Expendable rockets are used today by the United States, France, China, Brazil, Russia, India, and Israel to place satellites into Earth orbit and toward the Moon and planets. Most of the rockets now in use as launching vehicles evolved from missiles developed during military conflicts such as World War II (1939-1945). Beginning with a German missile called the V-2, these weapons were created to carry large high-energy explosives tohit cities or troop encampments. Later, after World War II ended, larger and more powerful missiles were created to carry nuclear weapons to targets on the other side of Earth.

Two nations, the United States and the Soviet Union, were the first to develop these large bomb-carrying missiles. After World War II ended, the German scientists who designed the V-2 missile fled Germany. Some of them surrendered to the United States, while others escaped to the Soviets. Each group of German scientists, engineers, and technicians sought to continue the development of rocketry and missiles in their new countries. In the Soviet Union, missile development was made a top priority by the Communist government. Part of the reason for the emphasis on missiles was the Soviet Union's lack of jet-powered bombers that could carry atomic bombs from Russia to targets in the United States. If large missiles could be built successfully, they could carry the bombs to their targets.

In America, Wernher von Braun headed the group of German rocket and missile experts. Von Braun was the head of the German missile program and was considered to be the most advanced expert on rocketry designs during and after the war. In the Soviet Union, his counterpart was Sergei Korolev, who was designated by the Soviet government as the "Chief Designer" of human-carrying and large expendable rockets.

Korolev became the head of a large central design bureau, and his "customers" were the specific missions assigned to his bureau. These included the design, manufacture, and test of the first Soviet intercontinental ballistic missile, the R-7; the first-and second-generation human-carrying space capsules, called Vostok and Soyuz; and a series of larger and more advanced liquid-powered expendable rockets, called Proton and N-1. These latter rockets were to be used in the Soviet lunar-landing program. The original purpose for the Proton, however, was as a very large missile that could fly from Russian bases and attack targets in the United States. The missile version of Proton was never developed, and instead it became a launching rocket for heavy payloads and space probes to the planets. Proton was also designated as the carrier rocket for the Soviet piloted lunar space capsule, called Zond.

In America, von Braun developed a series of liquid-fueled rockets called Juno and a large army missile called Redstone. These rockets were adapted for scientific space missions by von Braun's team working at the Redstone Arsenal in Huntsville, Alabama. By emplacing a small basket of solid rockets on the nose of the Juno II, von Braun was able to insert a small U.S. satellite into Earth orbit on January 31, 1958, marking the first U.S. artificial Earth satellite. Korolev did the same with the R-7, launching the Sputnik satellite three months earlier, on October 4, 1957.

Improvements to U.S. and Soviet Rockets

Increasingly, both the United States and the Soviet Union made improvements to their missiles that made them capable satellite and space capsule launchers. The U.S. equivalent to the Soviet R-7 was an intercontinental ballistic missile named Atlas. Developed initially for the U.S. Air Force to carry atomic warheads to targets in the Soviet Union, the air force and the newly created National Aeronautics and Space Administration (NASA) modified the missile's design to replace its bomb-carrying nosecone. In the nosecone's place, with reinforced nose sections, the Atlas could carry an additional liquid-fueled rocket stage that could send payloads—satellites, capsules, or space probes—into orbit or to the Moon or Mars.

In 1959 the Atlas missiles were modified to carry Project Mercury one-person space capsules, just as Korolev had done with the R-7 and its Vostok and Soyuz capsules. Eventually the Atlas and R-7 each received more powerful engines and larger upper stages. While the Mercury and Vostok projects have long since ended, both the Atlas and R-7 rockets are still in service, using advanced subsystems and powerful upper stages. Both are being sold today on the commercial space launch market, competing with each other for commercial sales.

The Atlas and R-7 were not the only throwaway rockets to evolve during the Cold War. The United States took a smaller and more limited intermediate range rocket called the Thor and adapted it for launching scientific space probes, beginning in 1960. Eventually the Thor grew to become, under the name Delta, one of the most reliable space launchers in history. In its Delta II, III, and IV variants it is still in government, military, and commercial use today.

Von Braun also developed the only U.S. throwaway rocket that was created from scratch and not evolved from missiles. From October 1961 until May 1973 three versions of a rocket called Saturn were used by NASA to support the man-on-the-Moon program called Project Apollo. The larger of these rockets, the Saturn V, sent Apollo astronauts to the surface of the Moon from 1969 to 1972 and lifted America's first space station, Skylab, in May 1973. Skylab itself was developed from the upper stage of the Saturn V rocket.

Briefly, the Soviet Union developed an expendable rocket called Energyia that was not developed from a missile. It flew in 1988 and 1989, in one flight carrying the unpiloted Buran space shuttle. The collapsing economic situation in Russia forced the abandonment of the Energyia program after those two flights.

The Evolution of Other Nations' Expendable Rockets

The launch vehicles used by China also evolved from ballistic missile designs. But the expendable rockets developed and flown by Japan, Brazil, and India are all new designs that had no direct missile ancestor, although all were strongly influenced by missile systems in use at the time. Israel's expendable rocket, a small booster named Shavit, is believed to have evolved from that nation's Jericho missile program.

France's fleet of commercial Ariane rockets were also created entirely apart from any missile project. Since 1979, Ariane rockets have been launching commercial satellites for customers worldwide, French military and government payloads, and payloads for the European Space Agency and the French Space Agency, CNES.

Today, expendable rockets are the mainstay of civil, military, and commercial satellite launches. The R-7 is still flying as the booster that lifts the Soyuz piloted space capsules. A commercial version is also for sale, flying from the same launching pad where the first satellite, Sputnik 1, and the first human, aboard Vostok 1, were launched in 1957 and 1961, respectively. The U.S. Atlas and Delta rockets are expected to be flying well into the twenty-first century, as are the Chinese missile-derived space boosters. The era of the expendable rocket may prove to be a long one in the evolving history of the space age.

see also Launch Facilities (volume 4); Launch Vehicles, Reusable (volume 1); Reusable Launch Vehicles (volume 4); Rockets (volume 3); Spaceports (volume 1); von Braun, Wernher (volume 3).

Frank Sietzen, Jr.