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1. The rocket takes off with the main stage lifting the two above it.

3. The second stage fires its motors until all of its fuel is gone, then it is dropped, too.

2. When its fuel tanks are empty, the first stage is dropped

4 The final stage boosts the payioad into space.

3. The second stage fires its motors until all of its fuel is gone, then it is dropped, too.

2. When its fuel tanks are empty, the first stage is dropped another. Each rocket is called a stage.

In a multistage rocket, the first stage is the largest. This is because it must lift itself from the surface of Earth as well as lift all the stages above it. Once its fuel and oxidizer are used up, it is dropped and the next stage can start its engines. The second stage can be smaller than the first one because it only has to lift itself and the stages it carries. And as before, once its fuel and oxi-dizer are used up, it can be cast off. Each time an empty stage is dropped, the rocket becomes lighter and can go higher and faster. Stages can be stacked one atop the other, as in the Saturn V. They can also be mounted side by side, as on the space shuttle.

By discarding empty fuel tanks as it goes, the staged rocket (left) is able to travel much farther and faster than a single-stage rocket of the same size.

Although the U.S. Army Redstone missile (above) had been developed for military use in the 1950s, it played an essential role in the early U.S. space program. Versions of the rocket were used to launch the first U.S. satellite in 1958 and the first American into space in 1961.

The United States after World War II. This

When it hit, five minutes after takeoff, the WAC-Corporal was still climbing. It finally reached its peak altitude six-and-a-half minutes after launch and 244 miles (393 km) above the ground. It had reached outer space. By comparison, modern space shuttles typically orbit between 150 and 250 miles (240 and 400 km) above the planet.

By 1950 the U.S. V-2 was 5 feet (1.5 m) longer than the original and could carry five times the payload. The U.S. Army moved its rocket development to the Redstone Arsenal in Huntsville, Alabama. This is where the Army Ballistic Missile Agency was created. The Redstone of 1952 was the first large-scale U.S. rocket to evolve from V-2 technology. The Redstone was developed as a medium-range missile. Its most important role, however, was the part the 69-foot (21 m) rocket was to play in the beginnings of the U.S. space program.

The Jupiter-C, an improved version of the Redstone, launched the first U.S. satellite, Exploreri. The Redstone Mercury launched the first U.S. astronaut into space. The Jupiter-C eventually evolved into the Juno satellite launch vehicle. This launched Pioneer 3, the satellite that discovered the Van Allen Radiation Belt that surrounds Earth. was in a hurry to develop large-scale missiles is because the Soviet Union had acquired a number of German rocket scientists. While most of these scientists were not as capable as Wernher von Braun and his colleagues, they were still quite knowledgeable. The U.S. military knew that the Soviet Union was using the talents of these scientists to develop rockets able to reach the United States.

The United States tended to create an entirely new rocket for every special purpose. The Soviets, on the other hand, took a more evolutionary tack. They expanded upon and improved the V-2.

By 1950 advanced models were produced at an abandoned aircraft factory. The Soviets made two major improvements. They made the payload separable from the body of the rocket. They also constructed the shell of the rocket as a monocoque. Instead of having tanks for the liquid oxygen and fuel that were separate from the rocket, the skin of the rocket was the outside wall of the tanks. This saved an enormous amount of weight, allowing the rocket to achieve greater speeds and higher altitudes. The Soviet V-2, "stretched" and modified, became larger and more powerful with each improvement. It continued to be used up to the 1960s.

The Jupiter-C rocket takes off in January 1958, carrying Explorer I, the United States's first artificial satellite.

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ing the half century that followed World War II. Because of the Cold War (political and military tension between the Soviet Union and the United States lasting from 1945 until 1991), militaries were the most active in rocket development. The United States feared that the Soviet Union might be building missiles capable of carrying nuclear warheads (intercontinental ballistic missiles, or ICBMs) to the United States. This drove the United States to develop a series of large, high-powered rockets quickly. New types of rockets that use neither liquid nor solid fuels were also developed during this time.

While the U.S. Army developed the Redstone and Jupiter missiles, the navy was especially interested in large missiles that could be fired from ToP: Gloria, th<

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FIRST AMERICAN MJULROCKIT FLIGHT

Top: Gloria, the first rocket-powered mail plane, is being prepared for its maiden flight in the United States in 1936. Sponsored by a wealthy U.S. stamp collector, the rocket was stuffed with letters specially postmarked to commemorate the flight. Middle: The mail rocket takes off over a frozen lake. Bottom: This is the special cancellation stamp used for the first American Mailrocket Flight.

A navy Viking rocket ready for takeoff in the late 1950s

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underwater by submarines. This led to the Polaris and Poseidon missiles and the Viking sounding rocket.

Meanwhile, the air force developed its Atlas and Titan ICBMs. Although they were designed for war, rockets such as the Jupiter, Atlas, and Titan were never launched against an enemy. Instead, they played an important role in the history of peaceful space exploration.

Launch Vehicles

Launch vehicles are rockets that are designed to boost something else into space, such as another rocket, a satellite, or a space probe. They usually are not designed to carry any one particular payload. They can actually be adapted to carry a wide variety of payloads, making them very versatile, useful rockets.

Since the mid-1950s, the United States, the Soviet Union, France, and several other nations have produced a variety of launch

EARLY U.S. LAUNCH VEHICLES AND EXPERIMENAL ROCKETS

Explorer satellite

W AC-Corpora I

W AC-Corpora I

Redstone booster

Goddard and the first liquid-fuel rocket

Mercury capsule

These are some of the launch vehicles used by the United States in the early years of space exploration, compared with Robert Goddard's first liquid-fuel rocket. Left to right: The Project Bumper rocket consisted of two stages: a German V-2 and a WAC-Corporal. The Aerobee was a highly successful sounding rocket developed in the 1950s. The Viking was a research rocket developed by the U.S. Navy, and the first stage of the Vanguard was evolved from the Viking. The Vanguard was supposed to have launched the first U.S. satellite, but technical problems delayed success and the army's Juno 1 placed the first U.S. satellite into orbit instead. The Mercury-Redstone booster was not only used to launch the first U.S. satellite, it also put the first U.S. astronaut in space as part of the Mercury program.

vehicles. Many of the earliest U.S. launch vehicles were based on rockets originally developed as military ballistic missiles. The Jupiter-C, for example, placed the first U.S. satellite into orbit in 1958. The Atlas propelled the first U.S. astronaut into Earth orbit in 1962 as part of the Mercury program. A modified air force Titan II launched the spacecraft of the Gemini program that ran from 1964 to 1966.

A larger, more powerful version of the Titan was later used to place heavy satellites in orbit. This included many of the satellites that make things such as international communication and satellite television possible. Titan launch vehicles also propelled the two Viking probes to the planet Mars and the two Voyager probes to the outer solar system.

One of the workhorses of the U.S. fleet of launch vehicles has been the Delta rocket. The first Delta was 8 feet (2.4 m) in diameter and stood 91 feet (28 m) high. Originally called the ThorDelta, its first successful launch put a satellite called Echo 1 into orbit. Echo 1 was little more than an enormous silver balloon. It was used to

A converted Atlas missile takes off on February 20, 1962, carrying John Glenn on his historic flight into space as the first U.S. astronaut in orbit.

A Titan rocket boosts a two-man Gemini capsule into orbit. Ten Gemini flights took place between April 8, 1964, and November 11, 1966.

One of the highly successful Delta launch vehicles takes off from the Kennedy Space Center. The rocket—in many different versions—has placed hundreds of satellites into orbit and is still being used.

reflect radio signals from one place on Earth to another.

During the next three decades, thirteen more Delta-type rockets were built. The first of these could place a 100-pound (45 kg) satellite into a low Earth orbit—about 124 to 726 miles (200 to 1,170 km) above Earth. The final Delta I model was able to place a 2,292-pound (1,041 kg) satellite into orbit at 22,236 miles (35,785 km) above Earth's surface.

Delta rockets have carried hundreds of satellites into orbit. These satellites help people all over the world to communicate, predict the weather, and perform scientific investigations. The Delta III rocket can lift 8,400 pounds (3,814 kg) into orbit, which is more than twice the capacity of the Delta II.

The Scout, a low-cost launch vehicle, was first used in the 1960s. It was originally designed to place 132-pound (60 kg) satellites into 300-mile (483 km) orbits. But the three-stage, 72-foot-long (22 m) Scout gradually evolved into a larger, more powerful, and more useful rocket. Scouts have launched more than one hundred satellites, including many built outside the United States. Eventually, Scout rockets were capable of carrying 460-pound (209 kg) satellites to an orbit 300 miles (483 km) above Earth. Most of these were scientific satellites that measured such things as the

A Scout rocket is a relatively small 82-foot (25-m) four-stage rocket that is used to place small satellites into orbit. Unlike most other satellite launchers, the Scout is a solid-fuel rocket. Since introducing the rocket in 1960, the National Aeronautics and Space Administration (NASA) carried out more than one hundred Scout launches. Most of them placed satellites in Earth orbit for scientists, the U.S. Department of Defense, and customers from other nations. The last Scout was launched in 1994.

composition and density of Earth's upper atmosphere.

The largest and most powerful launch vehicle ever built was the monster Saturn V, which boosted the Apollo spacecraft to the Moon in 1969. It stood 363 feet (111 m) tall—almost forty stories. Fully fueled and loaded, it weighed more than 6 million pounds (2.7 million kg). Its cluster of five enormous first-stage engines could produce 7.5 million pounds (3.4 million kg) of thrust.

The stages of the giant Saturn V rocket were stacked together inside the enormous Vehicle Assembly Building (VAB), one of the largest buildings ever constructed. Here, the Saturn V is being moved from the VAB (located at the Kennedy Space Center in Florida) to its launch site.

To assemble such a large rocket, scientists constructed one of the world's largest buildings, the enormous Vehicle Assembly Building (still part of the space shuttle program). Unlike most other launch vehicles, the Saturn V was designed for one particular type of mission: boosting spacecraft to the Moon.

For more than thirty years, the Soviets relied on the R-7 to boost most of their satellites into orbit. In the 1960s, the Soviets also began to use the Proton to place heavy satellite loads into Earth orbit. The Proton rockets ranged from 171 to 195 feet (52 to 59 m) high and were about 30 feet (9 m) in diameter. In recent years, the Proton has also launched satellites for other nations.

The United States and the Soviet Union weren't the only countries that wanted to send vehicles into space. Many European nations were anxious to develop their own launch vehicles. This was mainly because both the United States and the Soviet Union were charging other countries high fees to launch satellites. Any country that could

The stages of the giant Saturn V rocket were stacked together inside the enormous Vehicle Assembly Building (VAB), one of the largest buildings ever constructed. Here, the Saturn V is being moved from the VAB (located at the Kennedy Space Center in Florida) to its launch site.

develop its own rockets could share in the profitable launch market.

Few countries possess the financial and industrial resources of the United States or the former Soviet Union. So a group of European countries including Belgium, Britain, France, Germany, Italy, and the Netherlands banded together in 1964 to form the European Launcher Development Organization (ELDO), headquartered in Paris, France. The group's first spacecraft was the Europa 1. It consisted of three stages. The first was a British Blue Streak missile, the second a French Coralie rocket, and the third a German Astris. Unfortunately, the Europa 1 failed in the first attempt to launch it in 1970.

In 1974 ELDO merged with the European Space Research Organization to form the European Space Agency (ESA). The ESA-de-veloped Ariane launch vehicle made its first flight in 1979. It began commercial service in 1984 when the first private U.S. satellite was launched on a non-U.S. launch vehicle. By the end of 2006, Ariane rockets had boosted a total of 290 satellites into orbit.

The Sounding Rocket

The earliest pioneers envisioned many uses for rockets. One, for example, included exploring the conditions of the upper atmosphere beyond the reach of high-altitude balloons. This is known as sounding. It was, in fact, the original purpose of Goddard's research.

Many of the captured V-2s launched by the United States gathered data on the upper atmosphere. Meanwhile, scientists and engineers were able to study the workings of the large rockets. Soviet scientists, too, took advantage of the military development of their own captured V-2 rockets by conducting nonmilitary research. The instruments they carried were mostly only riding piggyback during launches that were really intended for gathering information about the rocket. Consequently, larger, more efficient rockets could be developed.

The first U.S. rocket designed specifically for sounding the upper atmosphere was the WAC-Corporal. Originally conceived in 1936 by Frank Malina, it was developed in 1945 by Aerojet. This was a small company founded only three years earlier as an offshoot of the Jet Propulsion Laboratory (a research organization founded by the University of California and later operated by NASA).

The relatively small WAC-Corporal was 24 feet (7 m) long and 1 foot (0.3 m) in diameter. It could carry a 25-pound (11 kg) package of instruments to an altitude of 100,000 feet (30,480 m). On its first flight, the rocket achieved an altitude of 45 miles (72 km), twice what its developers expected.

The development of the WAC-Corporal slowed when captured V-2 rockets became available. But the stock of V-2s was not unlimited. When only a few were left, Aerojet was asked to develop a replacement for the WAC-Corporal. The result was the Aerobee, which could carry a payload of 150 pounds (68 kg) to an altitude of more than 50 miles (80 km).

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