rocket

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rocket,

any vehicle propelled by ejection of the gases produced by combustion of self-contained propellants. Rockets are used in fireworks, as military weapons, and in scientific applications such as space exploration.

Rocket Propulsion

The force acting on a rocket, called its thrust, is equal to the mass ejected per second times the velocity of the expelled gases. This force can be understood in terms of Newton's third law of motion, which states that for every action there is an equal and opposite reaction. In the case of a rocket, the action is the backward-streaming flow of gas and the reaction is the forward motion of the rocket. Another way of understanding rocket propulsion is to realize that tremendous pressure is exerted on the walls of the combustion chamber except where the gas exits at the rear; the resulting unbalanced force on the front interior wall of the chamber pushes the rocket forward. A common misconception, before space exploration pointed up its obvious fallacy, holds that a rocket accelerates by pushing on the atmosphere behind it. Actually, a rocket operates more efficiently in outer space, since there is no atmospheric friction to impede its motion.

Rocket Design

The key elements in designing a rocket are the propulsion system, which includes the propellant and the exit nozzle, and determining the number of stages required to lift the intended payload. Rocket navigation is usually based on inertial guidance; internal gyroscopes are used to detect changes in the position and direction of the rocket.

Rocket Propellants

The most vital component of any rocket is the propellant, which accounts for 90% to 95% of the rocket's total weight. A propellant consists of two elements, a fuel and an oxidant; engines that are based on the action-reaction principle and that use air instead of carrying their own oxidant are properly called jets. Propellants in use today include both liquefied gases, which are more powerful, and solid explosives, which are more reliable. The chemical energy of the propellants is released in the form of heat in the combustion chamber.

A typical liquid engine uses hydrogen as fuel and oxygen as oxidant; a typical solid propellant is nitroglycerine. In the liquid engine, the fuel and oxidant are stored separately at extremely low temperatures; in the solid engine, the fuel and oxidant are intimately mixed and loaded directly into the combustion chamber. A solid engine requires an ignition system, as does a liquid engine if the propellants do not ignite spontaneously on contact.

The efficiency of a rocket engine is defined as the percentage of the propellant's chemical energy that is converted into kinetic energy of the vehicle. During the first few seconds after liftoff, a rocket is extremely inefficient, for at least two unavoidable reasons: High power consumption is required to overcome the inertia of the nearly motionless mass of the fully fueled rocket; and in the lower atmosphere, power is wasted overcoming air resistance. Once the rocket gains altitude, however, it becomes more efficient. as the trajectory, at first vertical, curves into a suborbital arc or into the desired orbit.

Although all known rockets currently in use derive their energy from chemical reactions, more exotic propulsion systems are being considered. In ion propulsion, a plasma (ionized gas consisting of a mixture of positively charged atoms and negatively charged electrons) would be created by an electric discharge and then expelled by an electric field. The engine could provide a low thrust efficiently for long periods; on a lengthy flight this would produce very high velocities, so that if there is ever a trip to the outer planets an ion drive might be used. Deep Space 1, a space probe launched in 1998 to test new technologies, was propelled intermittently by an ion engine. Even nuclear power has been considered for propulsion; in fact, a nuclear ramjet was developed in the early 1960s before it was realized that because the exhaust gases would be highly radioactive such a drive could never be used in earth's atmosphere.

Design of the Exit Nozzle

A critical element in all rockets is the design of the exit nozzle, which must be shaped to obtain maximum energy from the exhaust gases moving through it. The nozzle usually converges to a narrow throat, then diverges to create a form which shapes the hypersonic flow of exhaust gas most efficiently. The walls of the combustion chamber and nozzle must be cooled to protect them against the heat of the escaping gases, whose temperature may be as high as 3,000°C;—above the melting point of any metal or alloy.

Staging of Rockets

Although early rockets had only one stage, it was early recognized that no single-stage rocket can reach orbital velocity (5 mi/8 km per sec) or the earth's escape velocity (7 mi/11 km per sec). Hence multistage rockets, such as the two-stage Atlas-Centaur or the three-stage Saturn V, became necessary for space exploration. In these systems, two or more rockets are assembled in tandem and ignited in turn; once the lower stage's fuel is exhausted, it detaches and falls back to earth. Soviet systems clustered several rockets together, operated simultaneously, to obtain a large initial thrust.

Development of Rockets

The invention of the rocket is generally ascribed to the Chinese, who as early as A.D. 1000 stuffed gunpowder into sections of bamboo tubing to make military weapons of considerable effectiveness. The 13th-century English monk Roger BaconBacon, Roger,
c.1214–1294?, English scholastic philosopher and scientist, a Franciscan. He studied at Oxford as well as at the Univ. of Paris and became one of the most celebrated and zealous teachers at Oxford.
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 introduced to Europe an improved form of gunpowder, which enabled rockets to become incendiary projectiles with a relatively long range. Rockets subsequently became a common if unreliable weapon. Major progress in design resulted from the work of William Congreve, an English artillery expert, who built a 20-lb (9-kg) rocket capable of traveling up to 2 mi (3 km). In the late 19th cent., the Austrian physicist Ernst MachMach, Ernst
, 1838–1916, Austrian physicist and philosopher, b. Moravia. He taught (1864–67) mathematics at Graz and later, until his retirement in 1901, was professor of physics at Prague and Vienna.
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 gave serious theoretical consideration to supersonic speeds and predicted the shock wave that causes sonic boom.

The astronautical use of rockets was cogently argued in the beginning of the 20th cent. by the Russian Konstantin E. TsiolkovskyTsiolkovsky, Konstantin Eduardovich
, 1857–1935, Russian inventor and rocket expert. He lost his hearing in childhood, and, as he could not attend the usual schools, he educated himself.
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, who is sometimes called the "father of astronautics." He pointed out that a rocket can operate in a vacuum and suggested that multistage liquid-fuel rockets could escape the earth's gravitation. The greatest name in American rocketry is Robert H. GoddardGoddard, Robert Hutchings,
1882–1945, American physicist and rocket expert, b. Worcester, Mass., grad. Worcester Polytechnic Institute (B.S., 1908), Ph.D. Clark Univ., 1911. From 1914 he was associated with Clark Univ., becoming a professor of physics in 1919.
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, whose pamphlet A Method for Reaching Extreme Altitudes anticipated nearly all modern developments. Goddard launched the first liquid-fuel rocket in 1926 and demonstrated that rockets could be used to carry scientific apparatus into the upper atmosphere. His work found its most receptive audience in Germany. During World War II, a German team under Wernher von Braunvon Braun, Wernher
, 1912–77, German-American rocket scientist and astronautics engineer, b. Germany, grad. Berlin Technological Institute (B.S., 1932), Univ. of Berlin (Ph.D., 1934).
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 developed the V-2 rocket, which was the first long-range guided missile. The V-2 had a range greater than 200 mi (322 km) and reached velocities of 3,500 mi (5,600 km) per hr.

After the war, rocket research in the United States and the Soviet Union intensified, leading to the development first of intercontinental ballistic missiles and then of modern spacecraft. Important U.S. rockets have included the Redstone, Jupiter, Atlas, Titan, Agena, Centaur, and Saturn carriers. Saturn V, the largest rocket ever assembled, developed 7.5 million lb (3.4 million kg) of thrust. A three-stage rocket, it stood 300 ft (91 m) high exclusive of payload and with the Apollo delivered a payload of 44 tons to the moon. The space shuttlespace shuttle,
reusable U.S. space vehicle (1981–2011). Developed by the National Aeronautics and Space Administration (NASA) and officially known as the Space Transportation System (STS), it was the world's first reusable spacecraft that carried human beings into earth
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, or STS (1981–2011), had main engines that used liquid propellant and boosters that were solid-fuel rockets.

Rockets presently being used to launch manned and unmanned missions into space include the Brazilian VSV-30; the Chinese Long March 2C, 2E, and 2F; the European Space Agency's Ariane 5 series and Vega; the Indian PSLV (Polar Satellite Launch Vehicle); the Israeli Shavit 2; the Russian Soyuz U, FG, and 2 and Proton K and M; the Japanese H-IIA, H-IIB, and Epsilon; the South Korean–Russian KSLV-1; the U.S. Athena 1 and 2, Taurus, Titan 2 and 4B, Delta 2, 3, and 4, and Atlas 2 ,3, and 5; the multinational, private Sea Launch Zenit-3SL, which uses a converted oil platform located some 1,400 mi (2,250 km) southeast of Hawaii; and Space Exploration Technologies' (SpaceX) Falcon 9 and Orbital ATK's Antares, both of which are used to launch resupply capsulses to the International Space Station. In 2015 the Falcon 9's main stage achieved a controlled return landing. The Ares I, a two-stage NASA rocket designed to replace the STS as a launch vehicle on manned missions, underwent its first test flight in 2009. Blue Origin's New Shepard, consisting of a capsule and a reusable rocket booster, which also is designed to land vertically under power, had its first successful test in 2015.

See also space sciencespace science,
body of scientific knowledge as it relates to space exploration; it is sometimes also called astronautics. Space science draws on the conventional sciences of physics, chemistry, biology, and engineering, as well as requiring specific research of its own.
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.

Bibliography

See G. P. Sutton, Rocket Propulsion Elements: An Introduction to the Engineering of Rockets (6th ed. 1992); F. H. Winter, Rockets into Space (1993); D. Baker, Spaceflight and Rocketry: A Chronology (1996); M. Stoiko, Pioneers of Rocketry (1997); R. Snedden, Rockets and Space (1998).


rocket,

in botany, popular name for several plants of the family Cruciferae (mustardmustard,
common name for the Cruciferae, a large family chiefly of herbs of north temperate regions. The easily distinguished flowers of the Cruciferae have four petals arranged diagonally ("cruciform") and alternating with the four sepals.
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 family). The dame's, or damask, violet, damewort, or sweet rocket is Hesperis matronalis, a hardy, herbaceous Old World perennial with four-petaled flowers, ranging from white to purple, that are especially fragrant in the evening. It grows wild in many parts of North America, where it has escaped from gardens. Rocket salad (Eruca sativa) is the roquette of France and Italy and is a coarse, weedy plant with whitish or creamy-yellow flowers that have an orange-blossom odor. Also known as tira and garden rocket, it is cultivated for salads. Yellow rocket (Barbarea vulgaris) is the name for a variety of winter cress or upland cress, a weedy plant sometimes cultivated for salads. Among the North American wildflowers called rocket are the prairie-rocket (Erysimum asperum), the purple rocket (Iodanthus pinnatifidus), and the sea rocket (Cakile edulenta). The latter, like related European species, grows along seacoasts. The unrelated dyer's rocket, or dyer's-weed, is Reseda luteola, a species of mignonettemignonette
, common name for some members of the Resedaceae, a small family of herbs and a few shrubs inhabiting arid regions. The main genus, the mignonettes (genus Reseda
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. Rockets are classified in the division MagnoliophytaMagnoliophyta
, division of the plant kingdom consisting of those organisms commonly called the flowering plants, or angiosperms. The angiosperms have leaves, stems, and roots, and vascular, or conducting, tissue (xylem and phloem).
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, class Magnoliopsida, order Capparales, family Cruciferae.

rocket

(rok -it) See launch vehicle; sounding rocket.

Rocket

 

a flight vehicle propelled through space by the reactive thrust that occurs when the rocket ejects a portion of its own mass (the working fluid).

A typical rocket includes the following subassemblies: one or more rocket engines, a source of primary energy, a store of working fluid, and a payload. No ambient medium is needed for rocket flight; this factor renders the rocket the only suitable vehicle for space flights. The basic energy and operating characteristics of a rocket depend on the type of rocket engine and the type of fuel. Practically all modern rockets have engines that operate on a chemical fuel. The thrust developed by the rocket engine and the exhaust velocity of the reactive jet are of primary importance in a rocket; the thrust of the rocket engines used to launch spacecraft can reach 10 meganewtons, and the exhaust velocity of the reactive jet is between 3,000 and 4,500 m/sec.

Rockets are used for military purposes and scientific research and also for launching spacecraft. They may be unguided, as in some types of antitank, antiaircraft, and aircraft missiles, or guided. Guided missiles are equipped with devices that force the missile to alter its motion during flight. Guided ballistic rockets include rockets that use their own flight momentum over a major portion of their trajectories after shutting off the engine; for example, within the earth’s gravitational field a rocket moves along a curve that is part of an ellipse and is called a ballistic curve (seeBALLISTICS).

Depending on their major structural features, rockets may be classified as single-stage or multistage rockets. A modern single-stage rocket usually consists of a nose section, an instrument section, a fuel section, and an engine section. The nose section contains the payload (in military rockets this is an explosive charge), and the instrument section contains the guidance systems and other instruments. In contradistinction to liquid-propellant rockets, solid-propellant rockets feature integrated fuel and engine sections, because the entire fuel supply is housed within the engine chamber.

L. A. GIL’BERG

What does it mean when you dream about a rocket?

A rocket in a dream may symbolize that the dreamer’s ideas or plans are about to take off like a rocket, very rapidly achieving orbit and bringing the dreamer the success he or she has been working for.

rocket

[′räk·ət]
(aerospace engineering)
Any kind of jet propulsion capable of operating independently of the atmosphere.
A complete vehicle driven by such a propulsive system.

rocket

1. a Mediterranean plant, Eruca sativa, having yellowish-white flowers and leaves used as a salad: family Brassicaceae (crucifers)
2. any of several plants of the related genus Sisymbrium, esp S. irio (London rocket), which grow on waste ground and have pale yellow flowers
3. yellow rocket any of several yellow-flowered plants of the related genus Barbarea, esp B. vulgaris
4. sea rocket any of several plants of the related genus Cakile, esp C. maritima, which grow along the seashores of Europe and North America and have mauve, pink, or white flowers
5. dame's rocket another name for dame's violet See also dyer's rocket wall rocket