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They include cryogenic and storable bipropellant & monopropellant systems, hybrid systems.

Compare to bipropellant engines , monopropellant engines is sufficient low.

BASIC ELEMENTS

1.Oxidiser tanks

2.Fuel tank

3.Control valves

4.Rocket motor

Here ROCKET MOTOR is the heart of rocket engine

The basic rocket motor comprises of injection plate I, a

combustion chamber B, & discharge nozzle N.

The main functn of injection plate is to receive the liquid

oxidiser & fuel and direct them in liquid streams so that they mix

with one another and produce chemical reactn in c.c

When they get reacted with each other a very high pressure &

temp gases are produced which in turn are expanded in nozzle

to produce a high supersonic exit velocity(1500-4500m/s)

A cooling is also provided to prevent the walls of the

motor from melting becoz the temp of reactn often

exceeds 2700 deg.

Main there are two transporting system of propellants

from storage tanks to the rocket motor . They are :

1)Gas pressurization system

2)pump pressurization system

Mainly there are three liquid bipropellant combinations. They are: (1) The cryogenic oxygen-hydrogen propellant system, used

in upper stages and sometimes booster stages of space launch vehicles; it gives the highest specific impulse for a non-toxic combination, which makes it best for high vehicle velocity missions;

(2) the liquid oxygen-hydrocarbon propellant combination, used for booster stages (and a few second stages) of space launch vehicles; its higher average density allows a more compact booster stage, when compared to the first combination; also, historically, it was developed before the first combination and was mainly used for ballistic

missiles;

(3) several storable propellant combinations, used in large rocket engines for first and second stages of ballistic missiles and in almost all bipropellant low-thrust, auxiliary or reaction control rocket engines (this term is defined below); they allow long-term storage and almost instant readiness to start without the delays and precautions that come with cryogenic propellants.

A inert gas which will not react nor be excessively soluble with the fuel & oxidiser which are stored in tanks at high pressure as possible and is supplied through pressure-regulator valves to force the liquid propellants through the lines, bipropellant ctrl valves , injector plate into c.c.

The system is first energized by opening the system –energizing valve ,& then rocket motor is turned on by opening the bipropellant valve.

In order to increase of propellant tank wt with motor duration , inert gas vol & consequently the inert gas tank wt will also increase .

The gas pressurization system applicable only to short duration

The development of pump press system is for long-range rocket flight .

In this liquid oxidiser & fuel are stored in tanks at low pressure & forced into rocket at high pressure by the fuel & oxidiser pumps.

The power required for driving the pumps is supplied with steam & oxygen which is obtained by decomposing liquid hydrogen peroxide by catalyst such as Ca or Na permanganate.

The design of pumps that will handle the liquids safely & without leaks. Leaks cannot be tolerated becoz of the possibilities of fires or explosions.

The liquid oxidiser consists of acids,liquid oxygen,orconc hydrogen peroxide .

A bipropellant rocket unit has two separate liquid propellants, an oxidizerand a fuel. They are stored separately and are not mixed outside the combustion chamber. The majority of liquid propellant rockets have been manufactured for bipropellant applications.

A monopropellant contains an oxidizing agent and combustible matter in a single substance. It may be a mixture of several compounds or it may be a homogeneous material, such as hydrogen peroxide or hydrazine.

Monopropellants are stable at ordinary atmospheric conditions but decompose and yield hot combustion gases when heated or catalyzed.

In liquid bipropellant rocket engine systems propellants are stored in one or more oxidizer tanks and one or more fuel tanks.

Monopropellant rocket engine systems have, of course, only one set of propellant tanks.

Tanks can be arranged in a variety of ways, based on the location of the vehicle's center of gravity.

Common tank materials are aluminum, stainless steel, titanium, alloy steel, and fiber-reinforced plastics with an impervious thin inner liner of metal to prevent leakage through the pores of the fiber-reinforced walls.

There are several categories of tanks in liquid propellant propulsion systems:

1. For pressurization feed system the propellant tanks typically operate at anaverage pressure between 1.3 and 9 MPa or about 200 to 1800 lbf/in. 2.these tanks have thick walls and are heavy.

2. For high-pressure gas (used to expel the propellants) the tank pressures are much higher, typically between 6.9 and 69 MPa or 1000 to 10,000 lbf/in. 2. These tanks are usually spherical for minimum inert mass.

3. For turbopump feed systems it is necessary to pressurize the propellant tanks slightly (to suppress pump cavitation as explained in Section 10.1)to average values of between 0.07 and 0.34 MPa or 10 to 50 lbf/in. These low pressures allow thin tank walls, and therefore turbo pump feed systems have relatively low tank weights

Valves control the flows of liquids and gases and pipes conduct these fluids to the intended components. There are no rocket engines without them. There are many different types of valves. All have to be reliable, lightweight, leakproof, and must withstand intensive vibrations and very loud noises.

Two valves commonly used in pressurized feed systems are isolation valves (when shut, they isolate or shut off a portion of the propulsion system) and latch valves.

The SSME is normally closed, rotary actuated, cryogenic, high pressure, high flow, reusable ball valve, allowing continuous throtting, a controlled rate of opening through a crank and hydraulic piston (not shown), with a position feedback and anti-icing controls as shown in fig.

The propellant combination is a compromise of various factors , such as those listed below:

Corrosion.

Common physical hazard

Economic factors

Explosion hazard

Fire Hazard.

Accidental Spills.

Health Hazards.

Material Compatibility.

Some of the physical properties of propellant are given below:

Low Freezing Point.

High specific gravity.

Stability.

Heat transfer property.

Pumping Properties.

Temperature variation.

Ignition combustion and flame properties.

Many different types of storable and cryogenic liquid oxidizer propellants have been used, synthesized, or proposed .Several commonly used oxidizers are listed below.

>Liquid Oxygen (02)

>Hydrogen Peroxide (H202)

>Nitric Acid (HNO3)

>Nitrogen Tetroxide (N204)

These include aniline, furfuryl alcohcol, xylidine, gasoline, hydrazine hydrate, borohydrides,-methyl and/or ethyl alcohol, ammonia, and mixtures of some of these with one or more other fuels.

>Hydrocarbon Fuels

>Liquid Hydrogen (H2)

>Unsymmetrical Dimethylhydrazine

[(CH3)2NNH2]

>Hydrazine (N2H4)

>Monomethylhydrazine (CH3NHNH2)