Rocket History Future See Also External Links

In military terminology, a rocket generally uses solid propellant and is unguided. These rockets can be fired by ground-attack aircraft at fixed targets such as buildings, or can be launched by ground forces at other ground targets. During the Vietnam era, there were also air launched unguided rockets that carried a nuclear payload designed to attack aircraft formations in flight.

In military terminology, a missile, by contrast, can use either solid or liquid propellant, and has a guidance system.

Rockets range in size from tiny models that can be purchased at a hobby store, to the enormous Saturn VThis article is about the rocket. Saturn V may also refer to the numerical designation of Rhea, the moon of Saturn. The Saturn V (popularly known as the Moon Rocket) was a multistage liquid-fuel expendable rocket used by NASA's Apollo and Skylab programs. used for the Apollo program.

There are many different types of rockets, and a comprehensive list can be found in spacecraft propulsionStennis Space Center in Hancock County, Mississippi Spacecraft propulsion is used to change the velocity of spacecraft and artificial satellites, or in short, to provide delta-v. There are many different methods. Each method has drawbacks and advantages,.

Rockets are also used for deceleration, to transfer to a lower-energy orbit, for example to enter into a circular orbit from outside, to de-orbit for landingLanding is the last part of a flight where a flying animal or aircraft returns to the ground. Hitting the ground too hard is prevented by wings (including rotor wings), a parachute or rockets or a vertically directed jet engine; in the case of a balloon t, for the whole landing if there is no atmosphere (e.g. for landing on the MoonFor other moons in the solar system see natural satellite. For other uses see Moon (disambiguation). The Moon is the only natural satellite of Earth. It has no formal name other than "The Moon" although it is occasionally called Luna ( Latin for moon to d, the rocket of the descent stage of the Apollo Lunar ModuleThe Apollo Lunar Module was the lander portion of the Apollo spacecraft built for the US Apollo program to achieve the transit from Moon orbit to the surface and back. The module was also known as the LM from the manufacturer designation (yet pronounced " was applied), and sometimes to soften a parachute landing.

Most current rockets are chemical rockets. A chemical rocket engine may use solid propellant, such as the Space Shuttle's SRBs, or liquid propellant, like the Space Shuttle's main engines, or a hybrid. A chemical reaction is initiated between the fuel and the oxidizer in the combustion chamber, and the resultant hot gases accelerate out of a nozzle (or nozzles) at the rearward facing end of the rocket. The acceleration of these gases through the engine exerts force ('thrust') on the combustion chamber and nozzle, propelling the vehicle (in accordance with Newton's Third Law). See rocket engine for details.

Rockets must be used when there is no other substance (land, water, or air) that a vehicle may push against, such as in space. In these circumstances, it is necessary to carry all the propellant within the vehicle.

Rockets are particularly useful when very high speeds are required, such as orbital speed (mach 25 or so). The speeds that a rocket vehicle can reach can be calculated by the rocket equation; which gives the speed difference (' delta-v') in terms of the exhaust speed and ratio of inital mass to final mass ('mass ratio').

Common mass ratios for vehicles are 20/1 for dense propellants such as liquid oxygen and kerosene, 25/1 for dense monopropellants such as hydrogen peroxide, and 10/1 for liquid oxygen and liquid hydrogen. However, mass ratio is highly dependent on many factors such as the type of engine the vehicle uses and structural safety margins.

Sometimes, particularly in launch scenarios, the required velocity (delta-v) for a mission is unattainable because the propellant, structure, guidance and engines weigh so much as prevent the mass ratio from being high enough. This problem is frequently solved by staging - the rocket sheds excess weight (usually tankage and engines) to attain a higher effective mass ratio thus permitting a higher delta-v.

Typically the acceleration of a rocket increases with time due to applying the same thrust to a decreasing mass, with discontinuities when stages burn out, and starting at a lower acceleration with the new stage firing.

1 History

Historically, rockets were first developed by the Chinese as early as B.C. 300, using gunpowder. These were initially developed for entertainment, the precursors to modern fireworks, but were later adapted for warfare in the 11th century. Because the pressures on the rocket walls are lower, the use of rockets in warfare preceded the use of the gun, which required a higher level of metal technology. It was in this role that rockets first became known to Europeans following their use by Ottomans at the siege of Constantinople in 1453. For several more centuries they remained curiosities to those in the West.

At the end of the 18th century, rockets were used militarily in India against the British by the Mahrattas. The British then took up the practice and developed them further during the 19th century. The major figure in the field at this time was William Congreve. From there, the use of military rockets spread throughout Europe. The rockets' red glare helped to inspire the US national anthem.

Early rockets were highly inaccurate. Without any spinning up of the rocket, nor any gimballing of the thrust, they had a strong tendency to veer sharply off course. The early British Congreve rockets reduced this tendency somewhat by attaching a long stick to the end of a rocket (similar to modern bottle rockets) to make it harder for the rocket to change course. The largest of the Congreve rockets was the 32 pound (14.5 kg) Carcass, which had a 15 foot (4.6 m) stick. Originally, sticks were mounted on the side, but this was later changed to mounting in the center of the rocket, reducing drag and enabling the rocket to be more accurately fired from a segment of pipe.

The accuracy problem was mostly solved in 1844 when William Hale modified the rocket design so that thrust was slightly vectored to cause the rocket to spin along its axis of travel like a bullet. The Hale rocket removed the need for a rocket stick, travelled further due to reduced air resistance, and was far more accurate.

Early rockets were also remarkably inefficient. Modern rockets were born when, after receiving a grant in 1917 from the Smithsonian Institution, Robert Goddard attached a de Laval nozzle to a rocket engine's combustion chamber, doubling the thrust and enormously raising the efficiency, giving the real possibility of practical space travel.

This technique was soon used on the V-2 rockets, designed by Wernher Von Braun who became one of the principal players in modern rocket development. V2s were deployed extensively by Adolf Hitler in the latter stages of World War II as terror weapons against the British population, each successful launch reaching high up into the vacuum of space and auguring the beginning of the Space Age.

Rockets remain a popular military weapon. The use of large battlefield rockets of the V-2 type has given way to guided missiles, but rockets are often used by helicopters and light aircraft for ground attack, being more powerful than machine guns, but without the recoil of heavy cannon. In the 1950s there was a brief vogue for air-to-air rockets, including the formidable AIR-2 'Genie' nuclear rocket, but by the early 1960s these had largely been abandoned in favor of air-to-air missiles.

2 Future

Nuclear thermal rockets have also been developed, but never deployed, they are particularly promising for interplanetary use. Nuclear pulse propulsion rocket concepts give very high thrust and exhaust velocities.

Another class of rocket-like thrusters in increasingly common use are ion drives, which use electrical rather than chemical energy to accelerate their reaction mass.

3 See also

4 External Links:

Governing Agencies

Software

Manufacturers and Part Suppliers

Other

Rockets and missiles Spacecraft propulsion

<Hide>

Home > Rocket