INTRODUCTION

• What is Cryogenics ?

 cryogenics is the study of the production of very low temperature (below −150 °C, −238 °F or 123 K) and the behavior of materials at those temperatures

absolute temperature scales in Cryogenics These are Kelvin (SI units) or Rankine scale (Imperial & US units).

CRYOGENIC ENGINE INTRODUCTION

• The use of liquid fuel for rocket engines was considered as early as the beginning of 20th century. The Russian K.E.Ziolkowsky, the American H.Goddard and the German-Romanian H.Oberth worked independently on the problems of spaceflight and soon discovered that in order to succeed, rockets with high mass-flow were mandatory. Already then the combustion of liquid fuels seemed the most promising method of generating thrust

CRYOGENIC LIQUIDS

• Cryogenic fuels, mainly liquid hydrogen, have been used as rocket fuels. Liquid oxygen is used as an oxidizer of hydrogen, but oxygen is not, strictly speaking, a fuel.

Russian aircraft manufacturer Tuple developed a version of its popular design Tu-154 with a cryogenic fuel system, known as the Tu-155. The plane uses a fuel referred to as liquefied natural gas or LNG, and made its first flight in 1989.

PRINCIPLE:

• The principle of rocket propulsion depends on the following two laws: -

• (i) Newton 's third law of motion • (ii) Law of conservation of momentum

What is Cryogenic rocket engine?

A cryogenic rocket engine is a rocket engine that uses a cryogenic fuel or oxidizer, that is, its fuel or oxidizer (or both) is gases liquefied and stored at very low temperatures•At present, there are only five (US, Russia, France, China and Japan) countries which posses the necessary technology required to build these engines.

Components

The major components of a cryogenic rocket engine are:•combustion chamber•pyrotechnic igniter•fuel injector•gas turbine•rocket engine nozzle•Fuel tanks, etc.

WORKINGIn cryogenic engines, special insulated containers and vents are used to prevent gas from the evaporating liquids to escape. The liquid fuel and oxidizer are fed from the storage tank to an expansion chamber. Then it is injected into the combustion chamber. Here, they are mixed and ignited by a flame or spark. The fuel expands as it burns and the hot exhaust gases are directed out of the nozzle to provide thrust. 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 and rocket engine nozzle

WORKING(CONTD)

Cooling control systems

• A coolant control valve is mounted on the combustion chamber coolant bypass duct of each engine. The engine controller regulates the amount of gaseo

• . The chamber coolant valve is 100 % open before engine start. During engine operation, it will be 100 % open for throttle settings of 100 to 109 % for maximum cooling. us hydrogen

cryogenic engines

ADVANTAGES:•Non-toxic and non-corrosive propellants•High Specific Impulse•Non-hypergolic, improved ground safety

DISADVANTAGES:•Overall cost of propellants relatively high•Leakage•Transfer systems and operations

CONCLUSION:

• Present programs relate to Cryogenic Upper Stages for launch vehicles.

• Semi-cryogenic engines, Hypergolic engines are being developed

Cryogenics promises to be a field with lots of scope of improvement. As the temperature lowers further towards absolutezero, newer discoveries are bound to emerge