28-12-2010, 04:34 PM
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INTRODUCTION
Cryogenics originated from two Greek words “kyros” which means cold or freezing and “genes” which means born or produced. Cryogenics is the study of very low temperatures or the production of the same. Liquefied gases like liquid nitrogen and liquid oxygen are used in many cryogenic applications. Liquid nitrogen is the most commonly used element in cryogenics and is legally purchasable around the world. Liquid helium is also commonly used and allows for the lowest temperatures to be reached. These gases can be stored on large tanks called Dewar tanks, named after James Dewar, who first liquefied hydrogen, or in giant tanks used for commercial applications.
The field of cryogenics advanced when during world war two, when metals were frozen to low temperatures showed more wear resistance. In 1966, a company was formed, called Cyro-Tech, which experimented with the possibility of using cryogenic tempering instead of Heat Treating, for increasing the life of metal tools. The theory was based on the existing theory of heat treating, which was lowering the temperatures to room temperatures from high temperatures and supposing that further descent would allow more strength for further strength increase. Unfortunately for the newly-born industry the results were unstable as the components sometimes experienced thermal shock when cooled too fast. Luckily with the use of applied research and the with the arrival of the modern computer this field has improved significantly, creating more stable results.
Another use of cryogenics is cryogenic fuels. Cryogenic fuels, mainly oxygen and nitrogen have been used as rocket fuels. The Indian Space Research Organization (ISRO) is set to flight-test the indigenously developed cryogenic engine by early 2006, after the engine passed a 1000 second endurance test in 2003. It will form the final stage of the GSLV for putting it into orbit 36,000 km from earth.
Cryogenic Engines are rocket motors designed for liquid fuels that have to be held at very low "cryogenic" temperatures to be liquid - they would otherwise be gas at normal temperatures.
The engine components are also cooled so the fuel doesn't boil to a gas in the lines that feed the engine. The thrust comes from the rapid expansion from liquid to gas with the gas emerging from the motor at very high speed. The energy needed to heat the fuels comes from burning them, once they are gasses. Cryogenic engines are the highest performing rocket motors. One disadvantage is that the fuel tanks tend to be bulky and require heavy insulation to store the propellant. Their high fuel efficiency, however, outweighs this disadvantage. The Space Shuttle's main engines used for liftoff are cryogenic engines. The Shuttle's smaller thrusters for orbital maneuvering use non-cryogenic hypergolic fuels, which are compact and are stored at warm temperatures. Currently, only the United States, Russia, China, France, Japan and India have mastered cryogenic rocket technology.
All the current Rockets run on Liquid-propellant rockets. The first operational cryogenic rocket engine was the 1961 NASA design the RL-10 LOX LH2 rocket engine, which was used in the Saturn 1 rocket employed in the early stages of the Apollo moon landing program.
The major components of a cryogenic rocket engine are:
the thrust chamber or combustion chamber
pyrotechnic igniter
fuel injector
fuel turbo-pumps
gas turbine
cryo valves
Regulators
The fuel tanks
rocket engine
nozzle
Among them, the combustion chamber & the nozzle are the main components of the rocket engine.
HISTORY
The only known claim to liquid propellant rocket engine experiments in the nineteenth century was made by a Peruvian scientist named Pedro Paulet. However, he did not immediately publish his work. In 1927 he wrote a letter to a newspaper in Lima, claiming he had experimented with a liquid rocket engine while he was a student in Paris three decades earlier.
Historians of early rocketry experiments, among them Max Valier and Willy Ley, have given differing amounts of credence to Paulet's report. Paulet described laboratory tests of liquid rocket engines, but did not claim to have flown a liquid rocket.
The first flight of a vehicle powered by a liquid-rocket took place on March 16, 1926 at Auburn, Massachusetts, when American professor Robert H. Goddard launched a rocket which used liquid oxygen and gasoline as propellants. The rocket, which was dubbed "Nell", rose just 41 feet during a 2.5-second flight that ended in a cabbage field, but it was an important demonstration that liquid rockets were possible.
SPACE PROPULATION SYSTEM
Spacecraft propulsion is any method used to accelerate spacecraft and artificial satellites. There are many different methods. Each method has drawbacks and advantages, and spacecraft propulsion is an active area of research. However, most spacecraft today are propelled by forcing a gas from the back/rear of the vehicle at very high speed through a supersonic de Laval nozzle. This sort of engine is called a rocket engine.
All current spacecraft use chemical rockets (bipropellant or solid-fuel) for launch, though some have used air-breathing engines on their first stage. Most satellites have simple reliable chemical thrusters. Soviet bloc satellites have used electric propulsion for decades, and newer Western geo-orbiting spacecraft are starting to use them for north-south station keeping. Interplanetary vehicles mostly use chemical rockets as well, although a few have used ion thrusters to great success.
Presentation by
Roshan. S
[attachment=7702]Roshan. S
OBJECTIVES
Introduction of Propulsion.
Classification of Propulsion System.
Cryogenic Propulsion System.
Classifications of Cryogenic Engines.
References.
WHAT IS PROPULSION?
•Initiating or changing the motion of a body
–Translational(linear, moving faster or slower)
–Rotational(turning about an axis)
•Space propulsion
–Rocket launches
–Controlling satellite motion
–Maneuvering spacecraft
•Jet propulsion
–Using the momentum of ejected mass (propellant) to create a reaction force, inducing motion
WHY CRYOGENIC ENGINES?
The engine has high performance.
High specific impulse.
Most important is reusability.
CRYOGENIC PROPULSION ENGINE.
The propulsion system for Cryogenic Stage consists of two major subsystems:
The rocket engine.
The propellant feed system.
