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What is a Rocket

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					What is a Rocket?
A rocket is a type of engine that pushes itself forward or upward by producing thrust. Unlike a jet engine,
which draws in outside air, a rocket engine uses only the substances carried within it. As a result, a rocket
can operate in outer space, where there is almost no air. A rocket can produce more power for its size than
any other kind of engine. For example, the main rocket engine of the space shuttle weighs only a fraction as
much as a train engine, but it would take 39 train engines to produce the same amount of power. The word
rocket can also mean a vehicle or object driven by a rocket engine.

Rockets come in a variety of sizes. Some rockets that shoot fireworks into the sky measure less than 2 feet
(60 centimeters) long. Rockets 50 to 100 feet (15 to 30 meters) long serve as long-range missiles that can
be used to bomb distant targets during wartime. Larger and more powerful rockets lift spacecraft, artificial
satellites, and scientific probes into space. For example, the Saturn 5 rocket that carried astronauts to the
moon stood about 363 feet (111 meters) tall.

Rocket engines generate thrust by expelling gas. Most rockets produce thrust by burning a mixture of fuel
and an oxidizer, a substance that enables the fuel to burn without drawing in outside air. This kind of rocket
is called a chemical rocket because burning fuel is a chemical reaction. The fuel and oxidizer are called the
propellants.

A chemical rocket can produce great power, but it burns propellants rapidly. As a result, it needs a large
amount of propellants to work for even a short time. The Saturn 5 rocket burned more than 560,000 gallons
(2,120,000 liters) of propellants during the first 2 3/4 minutes of flight. Chemical rocket engines become
extremely hot as the propellants burn. The temperature in some engines reaches o 6000 degrees F (3300
degrees C), much higher than the temperature at which steel melts.

Jet engines also burn fuel to generate thrust. Unlike rocket engines, however, jet engines work by drawing in
oxygen from the surrounding air. For more information on jet engines, see Jet propulsion.

Researchers have also developed rockets that do not burn propellants. Nuclear rockets use heat generated
by a nuclear fuel to produce thrust. In an electric rocket, electric energy produces thrust.

Military forces have used rockets in war for hundreds of years. In the 1200's, Chinese soldiers fired rockets
against attacking armies. British troops used rockets to attack Fort McHenry in Maryland during the War of
1812 (1812-1815). After watching the battle, the American lawyer Francis Scott Key described "the rocket's
red glare" in the song "The Star-Spangled Banner." During World War I (1914-1918), the French used
rockets to shoot down enemy observation balloons. Germany attacked London with V-2 rockets during
World War II (1939-1945). In the Persian Gulf War of 1991 and the Iraq War, which began in 2003, United
States troops launched rocket-powered Patriot missiles to intercept and destroy Iraqi missiles.

Rockets are the only vehicles powerful enough to carry people and equipment into space. Since 1957,
rockets have lifted hundreds of artificial satellites into orbit around Earth. These satellites take pictures of
Earth's weather, gather information for scientific study, and transmit communications around the world.
Rockets also carry scientific instruments far into space to explore and study other planets. Since 1961,
rockets have launched spacecraft carrying astronauts and cosmonauts into orbit around Earth. In 1969,
rockets carried astronauts to the first landing on the moon. In 1981, rockets lifted the first space shuttle into
Earth orbit.

This article discusses Rocket (How rockets work) (How rockets are used) (Kinds of rocket engines)
(History).

How rockets work

Rocket engines generate thrust by putting a gas under pressure. The pressure forces the gas out the end of
the rocket. The gas escaping the rocket is called exhaust. As it escapes, the exhaust produces thrust
according to the laws of motion developed by the English scientist Isaac Newton. Newton's third law of
motion states that for every action, there is an equal and opposite reaction. Thus, as the rocket pushes the
exhaust backward, the exhaust pushes the rocket forward.
The amount of thrust produced by a rocket depends on the momentum of the exhaust -- that is, its total
amount of motion. The exhaust's momentum equals its mass (amount of matter) multiplied by the speed at
which it exits the rocket. The more momentum the exhaust has, the more thrust the rocket produces.
Engineers can therefore increase a rocket's thrust by increasing the mass of exhaust it produces.
Alternately, they can increase the thrust by increasing the speed at which the exhaust leaves the rocket.

Parts of a rocket include the rocket engine and the equipment and cargo the rocket carries. The four major
parts of a rocket are (1) the payload, (2) propellants, (3) the chamber, and (4) the nozzle.

The payload of a rocket includes the cargo, passengers, and equipment the rocket carries. The payload may
consist of a spacecraft, scientific instruments, or even explosives. The space shuttle's payload, for example,
is the shuttle orbiter and the mission astronauts and any satellites, scientific experiments, or supplies the
orbiter carries. The payload of a missile may include explosives or other weapons. This kind of payload is
called a warhead.

Propellants generally make up most of the weight of a rocket. For example, the fuel and oxidizer used by the
space shuttle account for nearly 90 percent of its weight at liftoff. The shuttle needs such a large amount of
propellant to overcome Earth's gravity and the resistance of the atmosphere.

The space shuttle and many other chemical rockets use liquid hydrogen as fuel. Hydrogen becomes a liquid
only at extremely low temperatures, requiring powerful cooling systems. Kerosene, another liquid fuel, is
easier to store because it remains liquid at room temperature.

Many rockets, including the space shuttle, use liquid oxygen, or lox, as their oxidizer. Like hydrogen, oxygen
must be cooled to low temperatures to become a liquid. Other commonly used oxidizers include nitrogen
tetroxide and hydrogen peroxide. These oxidizers remain liquid at room temperature and do not require
cooling.

An electric or nuclear rocket uses a single propellant. These rockets store the propellant as a gas or liquid.

The chamber is the area of the rocket where propellants are put under pressure. Pressurizing the
propellants enables the rocket to expel them at high speeds.

In a chemical rocket, the fuel and oxidizer combine and burn in an area called the combustion chamber. As
they burn, the propellants expand rapidly, creating intense pressure.

Burning propellants create extreme heat and pressure in the combustion chamber. Temperatures in the
chamber become hot enough to melt the steel, nickel, copper, and other materials used in its construction.
Combustion chambers need insulation or cooling to survive the heat. The walls of the chamber must also be
strong enough to withstand intense pressure. The pressure inside a rocket engine can exceed 3,000 pounds
per square inch (200 kilograms per square centimeter), nearly 100 times the pressure in the tires of a car or
truck.

In a nuclear rocket, the chamber is the area where nuclear fuel heats the propellant, producing pressure. In
an electric rocket, the chamber contains the electric devices used to force the propellant out of the nozzle.

The nozzle is the opening at the end of the chamber that allows the pressurized gases to escape. It converts
the high pressure of the gases into thrust by forcing the exhaust through a narrow opening, which
accelerates the exhaust to high speeds. The exhaust from the nozzle can travel more than 1 mile (1.6
kilometers) per second. Like the chamber, the nozzle requires cooling or insulation to withstand the heat of
the exhaust.

Multistage rockets
Many chemical rockets work by burning propellants in a single
combustion chamber. Engineers refer to these rockets as
single-stage rockets. Missions that require long-distance travel,
such as reaching Earth orbit, generally require multiple-stage
or multistage rockets. A multistage rocket uses two or more
sets of combustion chambers and propellant tanks. These
sets, called stages, may be stacked end to end or attached
side by side. When a stage runs out of propellant, the rocket
discards it. Discarding the empty stage makes the rocket
lighter, allowing the remaining stages to accelerate it more
strongly. Engineers have designed and launched rockets with
as many as five separate stages. The space shuttle uses two
stages.

How rockets are used

People use rockets for high-speed, high-power transportation
both within Earth's atmosphere and in space. Rockets are
especially valuable for (1) military use, (2) atmospheric
research, (3) launching probes and satellites, and (4) space
travel.

Military use

Rockets used by the military vary in size from small rockets
used on the battlefield to giant guided missiles that can fly
across oceans. The bazooka is a small rocket launcher carried     A two-stage rocket carries a propellant and one
by soldiers for use against armored vehicles. A person using a    or more rocket engines in each stage. The first
bazooka has as much striking power as a small tank. Armies        stage launches the rocket. After burning its
use larger rockets to fire explosives far behind enemy lines      supply of propellant, the first stage falls away
and to shoot down enemy aircraft. Fighter airplanes carry         from the rest of the rocket. The second stage
rocket-powered guided missiles to attack other planes and         then ignites and carries the payload into earth
ground targets. Navy ships use guided missiles to attack other    orbit or even farther into space. A balloon and
ships, land targets, and planes.                                  a rocket work in much the same way. Gas
                                                                  flowing from the nozzle creates unequal
Powerful rockets propel a type of long-range guided missile       pressure that lifts the balloon or the rocket off
called an intercontinental ballistic missile (ICBM). Such a       the ground. Image credit: World Book diagram
missile can travel 3,400 miles (5,500 kilometers) or more to bomb an enemy target with nuclear explosives.
An ICBM generally employs two or three separate stages to propel it during the early part of its flight. The
ICBM coasts the rest of the way to its target.

Atmospheric research

Scientists use rockets to explore Earth's atmosphere. Sounding rockets, also called meteorological rockets,
carry such equipment as barometers, cameras, and thermometers high into the atmosphere. These
instruments collect information about the atmosphere and send it by radio to receiving equipment on the
ground.

Rockets also provide the power for experimental research airplanes. Engineers use these planes in the
development of spacecraft. By studying the flights of such planes as the rocket-powered X-1 and X-15,
engineers learned how to control vehicles flying many times as fast as the speed of sound.

Launching probes and satellites

Rockets carry crewless spacecraft called space probes on long voyages to explore the solar system. Probes
have explored the sun, the moon, and all the planets in our solar system except Pluto. They carry scientific
instruments that gather information about the planets and transmit data back to Earth. Probes have landed
on the surface of the moon, Venus, and Mars.
Rockets lift artificial satellites into orbit around Earth. Some orbiting satellites gather information for scientific
research. Others relay telephone conversations and radio and television broadcasts across the oceans.
Weather satellites track climate patterns and help scientists predict the weather. Navigation satellites, such
as those that make up the Global Positioning System (GPS), enable receivers anywhere on Earth to
determine their locations with great accuracy. The armed forces use satellites to observe enemy facilities
and movements. They also use satellites to communicate, monitor weather, and watch for missile attacks.
Not only are satellites launched by rockets, but many satellites use small rocket engines to maintain their
proper orbits.

Rockets that launch satellites and probes are called launch vehicles. Most of these rockets have from two to
four stages. The stages lift the satellite to its proper altitude and give it enough speed -- about 17,000 miles
(27,000 kilometers) per hour -- to stay in orbit. A space probe's speed must reach about 25,000 miles
(40,000 kilometers) per hour to escape Earth's gravity and continue on its voyage.

Engineers created the first launch vehicles by altering military rockets or sounding rockets to carry
spacecraft. For example, they added stages to some of these rockets to increase their speed. Today,
engineers sometimes attach smaller rockets to a launch vehicle. These rockets, called boosters, provide
additional thrust to launch heavier spacecraft.

Space travel

Rockets launch spacecraft carrying astronauts that orbit Earth and travel into space. These rockets, like the
ones used to launch probes and satellites, are called launch vehicles.

The Saturn 5 rocket, which carried astronauts to the moon, was the most powerful launch vehicle ever built
by the United States. Before launch, it weighed more than 6 million pounds (2.7 million kilograms). It could
send a spacecraft weighing more than 100,000 pounds (45,000 kilograms) to the moon. The Saturn 5 used
11 rocket engines to propel three stages.

Space shuttles are reusable rockets that can fly into space and return to Earth repeatedly. Engineers have
also worked to develop space tugs, smaller rocket-powered vehicles that could tow satellites, boost space
probes, and carry astronauts over short distances in orbit. For more information on rockets used in space
travel, see Space exploration.

Other uses

People have fired rockets as distress signals from ships and airplanes and from the ground. Rockets also
shoot rescue lines to ships in distress. Small rockets called JATO (jet-assisted take-off) units help heavily
loaded airplanes take off. Rockets have long been used in fireworks displays. Kinds of rocket engines

The vast majority of rockets are chemical rockets. The two most common types of chemical rockets are
solid-propellant rockets and liquid-propellant rockets. Engineers have tested a third type of chemical rocket,
called a hybrid rocket, that combines liquid and solid propellants. Electric rockets have propelled space
probes and maneuvered orbiting satellites. Researchers have designed experimental nuclear rockets.
Solid-propellant rockets burn a rubbery or plastic-like material
called the grain. The grain consists of a fuel and an oxidizer in
solid form. It is shaped like a cylinder with one or more
channels or ports that run through it. The ports increase the
surface area of the grain that the rocket burns. Unlike some
liquid propellants, the fuel and oxidizer of a solid-propellant
rocket do not burn upon contact with each other. Instead, an
electric charge ignites a smaller grain. Hot exhaust gases from
this grain ignite the main propellant surface.

The temperature in the combustion chamber of a solid-
propellant rocket ranges from 3000 to 6000 degrees F (1600 to
3300 degrees C). In most of these rockets, engineers build the
chamber walls from high-strength steel or titanium to withstand
the pressure and heat of combustion. They also may use
composite materials consisting of high-strength fibers
embedded in rubber or plastic. Composite chambers made
from high-strength graphite fibers in a strong adhesive called
epoxy weigh less than steel or titanium chambers, enabling the
rocket to accelerate its payload more efficiently. Solid
propellants burn at a rate of about 0.6 inch (1.5 centimeters)
per second.                                                           A solid-propellant rocket burns a solid
                                                                      material called the grain. Engineers design
Solid propellants can remain effective after long storage and         most grains with a hollow core. The propellant
present little danger of combusting or exploding until ignited.       burns from the core outward. Unburned
Furthermore, they do not need the pumping and injecting               propellant shields the engine casing from the
equipment required by liquid propellants. On the other hand,          heat of combustion. Image credit: World Book
rocket controllers cannot easily stop or restart the burning of       diagram by Precision Graphics
solid propellant. This can make a solid-propellant rocket difficult to control. One method used to stop the
burning of solid propellant involves blasting the entire nozzle section from the rocket. This method, however,
prevents restarting.

Rocket designers often choose solid propellants for rockets that must be easy to store, transport, and
launch. Military planners prefer solid-propellant rockets for many uses because they can be stored for a long
time and fired with little preparation. Solid-propellant rockets power ICBM's, including the American
Minuteman 2 and MX and the Russian RT-2. They also propel such smaller missiles as the American
Hellfire, Patriot, Sparrow, and Sidewinder, and the French SSBS. Solid-propellant rockets often serve as
sounding rockets and as boosters for launch vehicles and
cruise missiles. They are also used in fireworks.
Liquid-propellant rockets burn a mixture of fuel and oxidizer        A liquid-propellant rocket carries fuel and an
in liquid form. These rockets carry the fuel and the oxidizer        oxidizer in separate tanks. The fuel circulates
in separate tanks. A system of pipes and valves feeds the            through the engine's cooling jacket before entering
propellants into the combustion chamber. In larger engines,          the combustion chamber. This circulation preheats
either the fuel or the oxidizer flows around the outside of          the fuel for combustion and helps cool the rocket.
the chamber before entering it. This flow cools the chamber          Image credit: World Book diagram by Precision
and preheats the propellant for combustion.                          Graphics

A liquid-propellant rocket feeds the fuel and oxidizer into the combustion chamber using either pumps or
high-pressure gas. The most common method uses pumps to force the fuel and oxidizer into the combustion
chamber. Burning a small portion of the propellants provides the energy to drive the pumps. In the other
method, high-pressure gas forces the fuel and oxidizer into the chamber. The gas may be nitrogen or some
other gas stored under high pressure or may come from the burning of a small amount of propellants.

Some liquid propellants, called hypergols, ignite when the fuel and the oxidizer mix. But most liquid
propellants require an ignition system. An electric spark may ignite the propellant, or the burning of a small
amount of solid propellant in the combustion chamber may do so. Liquid propellants continue to burn as long
as fuel and oxidizer flow into the combustion chamber.

Engineers use thin, high-strength steel or aluminum to construct most tanks that hold liquid propellants.
They may also reinforce tanks with composite materials like those used in solid-propellant rocket chambers.
Most combustion chambers in liquid-propellant rockets are
made of steel or nickel.

Liquid propellants usually produce greater thrust than do
equal amounts of solid propellants burned in the same
amount of time. Controllers can easily adjust or stop burning
in a liquid-propellant rocket by increasing or decreasing the
flow of propellants into the chamber. Liquid propellants,
however, are difficult to handle. If the fuel and oxidizer blend
without igniting, the resulting mixture often will explode easily.
Liquid propellants also require complicated pumping
machinery.

Scientists use liquid-propellant rockets for most space launch
vehicles. Liquid-propellant rockets serve as the main engines
of the space shuttle as well as Europe's Ariane rocket,
Russia's Soyuz rocket, and China's Long March rocket.

Hybrid rockets combine some of the advantages of both
solid-propellant and liquid-propellant rockets. A hybrid rocket
uses a liquid oxidizer, such as liquid oxygen, and a solid-fuel
grain made of plastic or rubber. The solid-fuel grain lines the
inside of the combustion chamber. A pumping system sprays
the oxidizer onto the surface of the grain, which is ignited by
a smaller grain or torch.

Hybrid rockets are safer than solid-propellant rockets            Launch vehicles used by European nations
because the propellants are not premixed and so will not          include the European Space Agency's Ariane 5
ignite accidentally. Also, unlike solid-propellant rockets,       rocket and Russia's A class and Proton rockets.
hybrid rockets can vary thrust or even stop combustion by         These vehicles carry space probes and artificial
adjusting the flow of oxidizer. Hybrid engines require only half  satellites into outer space. The A Class rocket
the pumping gear of liquid-propellant rockets, making them        has also carried people into space, and the
simpler to build.                                                 Proton rocket has carried International Space
                                                                  Station modules. Image credit: World Book
A key disadvantage of hybrid rockets is that their fuel burns     illustrations by Oxford Illustrators Limited
slowly, limiting the amount of thrust they can produce. A hybrid rocket burns grain at a rate of about 0.04
inch (1 millimeter) per second. For a given amount of propellant, hybrid rockets typically produce more thrust
than solid rockets and less than liquid engines. To generate more thrust, engineers must manufacture
complex fuel grains with many separate ports through which oxidizer can flow. This exposes more of the
grain to the oxidizer.

Researchers have used hybrid rockets to propel targets used in missile testing and to accelerate
experimental motorcycles and cars attempting land speed records. Their safety has led designers to attempt
to develop hybrid rockets for use in human flight. One such rocket would launch from an airplane to carry
people to an altitude of about 60 miles (100 kilometers). Researchers have not yet developed hybrid rockets
powerful enough to launch human beings into space. Hybrid rockets can produce enough thrust, however, to
boost planetary probes or maneuver satellites in orbit. Hybrid rockets could also power escape mechanisms
being developed for new launch vehicles that would carry crews.

The safety of hybrid rockets has led engineers to develop them for use in human flight. The Scaled
Composites company of Mojave, California, developed a hybrid rocket called SpaceShipOne that launched
from an airplane. On June 21, 2004, SpaceShipOne became the first privately funded craft to carry a person
into space. It carried the American test pilot Michael Melvill more than 62 miles (100 kilometers) above
Earth's surface during a brief test flight.

Researchers have also used hybrid rockets to propel targets used in missile testing and to accelerate
experimental motorcycles and cars attempting land speed records. In addition, they have worked to develop
hybrid rockets to boost planetary probes, maneuver satellites in orbit, and power crew escape mechanisms
for launch vehicles.

Electric rockets use electric energy to expel ions
(electrically charged particles) from the nozzle. Solar
panels or a nuclear reactor can provide the energy.

In one design, xenon gas passes through an electrified
metal grid. The grid strips electrons from the xenon
atoms, turning them into positively charged ions. A
positively charged screen repels the ions, focusing them
into a beam. The beam then enters a negatively charged
device called an accelerator. The accelerator speeds up
the ions and shoots them out through a nozzle.

The exhaust from such rockets travels extremely fast.
However, the stream of xenon ions has a relatively low
mass. As a result, an electric rocket cannot produce
enough thrust to overcome Earth's gravity. Electric
rockets used in space must therefore be launched by
chemical rockets. Once in space, however, the low rate
of mass flow becomes an advantage. It enables an
electric rocket to operate for a long time without running
out of propellant. The xenon rocket that powered the U.S.
space probe Deep Space 1, launched in 1998, fired for a         An ion rocket is a kind of electric rocket. Heating
total of over 670 days using only 160 pounds (72                coils in the rocket change a fuel, such as xenon, into
kilograms) of propellant. In addition, small electric rockets   a vapor. A hot platinum or tungsten ionization grid
using xenon propellant have provided the thrust to keep         changes the flowing vapor into a stream of
communications satellites in position above Earth's             electrically charged particles called ions. Image
surface.                                                        credit: World Book diagram by Precision Graphics

Another type of electric rocket uses electromagnets rather than charged screens to accelerate xenon ions.
This type of rocket powers the SMART-1 lunar probe, launched by the European Space Agency in 2003.
Nuclear rockets use the heat energy of a nuclear reactor,
a device that releases energy by splitting atoms. Some
proposed designs would use hydrogen as propellant. The
rocket would store the hydrogen as a liquid. Heat from the
reactor would boil the liquid, creating hydrogen gas. The
gas would expand rapidly and push out from the nozzle.

The exhaust speed of a nuclear rocket might reach four
times that of a chemical rocket. By expelling a large
quantity of hydrogen, a nuclear rocket could therefore
achieve high thrust. However, a nuclear rocket would
require heavy shielding because a nuclear reactor uses
radioactive materials. The shielding would weigh so much
that the rocket could not be practically used to boost a
launch vehicle. More practical applications would use
small nuclear engines with low, continuous thrust to
decrease flight times to Mars or other planets.

Nuclear rocket developers must also overcome public
fears that accidents involving such devices could release
harmful radioactive materials. Before nuclear rockets can
be launched, engineers must convince the public that such      A nuclear rocket uses the heat from a nuclear
devices are safe.                                              reactor to change a liquid fuel into a gas. Most of
                                                               the fuel flows through the reactor. Some of the fuel,
History                                                        heated by the nozzle of the rocket, flows through
                                                               the turbine. The turbine drives the fuel pump.
                                                               Image credit: World Book diagram by Precision
Historians believe the Chinese invented rockets, but they      Graphics
do not know exactly when. Historical accounts describe
"arrows of flying fire" -- believed to have been rockets -- used by Chinese armies in A.D. 1232. By 1300, the
use of rockets had spread throughout much of Asia and Europe. These first rockets burned a substance
called black powder, which consisted of charcoal, saltpeter, and sulfur. For several hundred years, the use
of rockets in fireworks displays outranked their military use in importance

During the early 1800's, Colonel William Congreve of the British Army developed rockets that could carry
explosives. Many of these rockets weighed about 32 pounds (15 kilograms) and could travel 1 3/4 miles (2.7
kilometers). British troops used Congreve rockets against the United States Army during the War of 1812.
Austria, Russia, and several other countries also developed military rockets during the early 1800's.

The English inventor William Hale improved the accuracy of military rockets. He substituted three fins for the
long wooden tail that had been used to guide the rocket. United States troops used Hale rockets in the
Mexican War (1846-1848). During the American Civil War (1861-1865), both sides used rockets.

Rockets of the early 1900's

The Russian school teacher Konstantin E. Tsiolkovsky first stated the correct theory of rocket power. He
described his theory in a scientific paper published in 1903. Tsiolkovsky also first presented the ideas of the
multistage rocket and rockets using liquid oxygen and hydrogen propellants. In 1926, the American rocket
pioneer Robert H. Goddard conducted the first successful launch of a liquid-propellant rocket. The rocket
climbed 41 feet (13 meters) into the air at a speed of about 60 miles (97 kilometers) per hour and landed
184 feet (56 meters) away.

During the 1930's, rocket research advanced in Germany, the Soviet Union, and the United States.
Hermann Oberth led a small group of German engineers and scientists that experimented with rockets.
Leading Soviet rocket scientists included Fridrikh A. Tsander and Sergei P. Korolev. Goddard remained the
most prominent rocket researcher in the United States.
During World War II, German engineers under the
direction of Wernher von Braun developed the powerful V-
2 guided missile. Germany bombarded London and
Antwerp, Belgium, with hundreds of V-2's during the last
months of the war. American forces captured many V-2
missiles and sent them to the United States for use in
research. After the war, von Braun and about 150 other
German scientists moved to the United States to continue
their work with rockets. Some other German rocket
experts went to the Soviet Union.

High-altitude rockets

For several years after World War II, U.S. scientists
benefited greatly by conducting experiments with captured
German V-2's. These V-2's became the first rockets used
for high-altitude research.

The first high-altitude rockets designed and built in the
United States included the WAC Corporal, the Aerobee,
and the Viking. The 16-foot (4.9-meter) WAC Corporal
reached altitudes of about 45 miles (72 kilometers) during
test flights in 1945. Early models of the Aerobee climbed
                                                              The vehicles shown here helped the United States
about 70 miles (110 kilometers). In 1949, the U.S. Navy
                                                              and the Soviet Union achieve milestones in the
launched the Viking, an improved liquid-propellant rocket
                                                              exploration of space. The United States no longer
based chiefly on the V-2. The Viking measured more than
                                                              builds these rockets, but Russia continues to use the
45 feet (14 meters) long, much longer than the Aerobee.
                                                              Soviet A Class design in the Soyuz rocket.
But the first models of the Viking rose only about 50 miles
                                                              • Jupiter C, U.S. Lifted Explorer I, the first U.S.
(80 kilometers).
                                                              satellite, in 1958. 68 feet (21 meters)
                                                              • Mercury-Redstone, U.S. Launched Alan Shepard
Rockets developed by the U.S. armed forces during the         in 1961. 83 feet (25 meters)
1950's included the Jupiter and the Pershing. The Jupiter     • A Class (Sputnik), Soviet. Boosted Sputnik 1, the
had a range of about 1,600 miles (2,600 kilometers), and      first artificial satellite, in 1957. 98 feet (29 meters)
the Pershing could travel about 450 miles (720                Image credit: WORLD BOOK illustrations by
kilometers).                                                  Oxford Illustrators Limited
The vehicles shown here helped the       The U.S. Navy conducted the first successful launch of a Polaris
United States and the Soviet Union       underwater missile in 1960. United States space scientists later used
achieve milestones in the exploration    many military rockets developed in the 1950's as the basis for launch
of space. The United States no           vehicles.
longer builds these rockets, but
Russia continues to use the Soviet A     Rocket-powered airplanes
Class design in the Soyuz rocket.
• A Class (Vostok), Soviet. Carried
Yuri Gagarin, the first person to        On Oct. 14, 1947, Captain Charles E. Yeager of the U.S. Air Force made
orbit the earth, in 1961. 126 feet (38   the first supersonic (faster than sound) flight. He flew a rocket-powered
meters)                                  airplane called the X-1.
• Saturn 5, U.S. Launched Neil
Armstrong, the first person to set       A rocket engine also powered the X-15, which set an unofficial airplane
foot on the moon, in 1969. 363 feet      altitude record of 354,200 feet (107,960 meters) in 1963. In one flight, the
(111 meters) Image credit: WORLD         X-15 reached a peak speed of 4,520 miles (7,274 kilometers) per hour --
BOOK illustrations by Oxford             more than six times the speed of sound. A privately owned and
Illustrators Limited                     developed rocket-powered plane called the EZ-Rocket began piloted test
flights in 2001.

The space age began on Oct. 4, 1957, when the Soviet Union launched the first artificial satellite, Sputnik 1,
aboard a two-stage rocket. On Jan. 31, 1958, the U.S. Army launched the first American satellite, Explorer
1, into orbit with a Juno I rocket.

On April 12, 1961, a Soviet rocket put a cosmonaut, Major Yuri A. Gagarin, into orbit around Earth for the
first time. On May 5, 1961, a Redstone rocket launched Commander Alan B. Shepard, Jr., the first American
to travel in space. On April 12, 1981, the United States launched the rocket-powered Columbia, the first
space shuttle to orbit Earth. For more information on the history of rockets in space travel, see Space
exploration.

Rocket research

In the early 2000's, engineers and scientists worked to develop lightweight rocket engines that used safer
propellants. They also searched for more efficient propellants that did not require refrigeration. Engineers
began designing and testing smaller rocket engines for use in smaller vehicles, such as tiny satellites that
may weigh only a few pounds or kilograms when fully loaded.

Contributor: Stephen Heister, Ph.D., Professor of Aeronautics and Astronautics, Purdue University.

How to cite this article: To cite this article, World Book recommends the following format: Heister, Stephen.
"Rocket." World Book Online Reference Center. 2005. World Book, Inc.
http://www.worldbookonline.com/wb/Article?id=ar472580.

				
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