Rocket nozzleclassification

ROCKET NOZZLE

Component of a rocket or air-breathing engine that produces thrust Accomplished b converting the thermal energy of the hot chamber gases into kinetic energy Common for both solid and liquid propellant rocket motor

ROCKET NOZZLE CLASSIFICATION

Rocket nozzles are classified into two groups

1) Conventional nozzles I ) Conical nozzles conventionally

adopted

ii) Bell nozzles or contoured configurations

nozzles

2) Advanced concept nozzles I ) Aero spike nozzle ii) Expansion deflection (E – D) nozzles

CONICAL NOZZLES

Wall diverge at a constant angle. The exit i.e., the supersonic portion is straight The conical nozzles with a 15° divergent half angle is standard.

• The conical nozzle is the oldest and simplest configuration.

• It is relatively easy to fabricate.• When momentum equation is applied the thrust

is reduced by a factor. λ= (1+ cos α)/2 for rockets λ = 1.0 thus α = 15° known as half angle of the nozzle.• Gives high specific impulse.• Small cone nozzle leads to excessive length.

Advantages Fabrication simplicity

Application SLV – 3 Booster nozzles is a conical nozzles Most of the warfare applications

BELL NOZZLES OR CONTOURED NOZZLES

Nozzles shape is contoured , not a straight one To gain higher performance and shorter length To contour the nozzle to avoid oblique shockAPPLICATIONS Upper stage propulsion systems Satellite on broad propulsion systems

• Most common type of nozzle used today.• It has a high expansion section(20° to 50°) due to

high relative pressure , large pressure gradient and rapid expansion of working fluid.

• Separation does not occur until discontinuities are there in nozzle contour.

• More efficient than cone nozzle of similar configuration as contour is designed to minimize losses.

• NOTE: Remember method of characteristics.

TWO STEP NOZZLES• Modification of bell shaped nozzle.• Aims to achieve maximum performance at more

than a single altitude.• Concept of extendible nozzle. actuators ,power supply and mechanisms come into picture.• Dual bell nozzle-two shortened nozzles combined

into one with a bump or inflection point.• Very little practical experience.

ADVANCED CONCEPTS NOZZLES

In the contour nozzles , there is a danger of nozzles flow separation In the advanced concepts nozzles, this flow separation is avoided Nozzles can be operated for wider altitude operations , for different conditions of chamber pressure

AEROSPIKE AND EXPANSION DEFLECTION NOZZLE

• To offset the thrust loss associated with overexpansion.

• Flow from the combustion chamber passes through an annular throat.

• For plug nozzle(aero spike) the flow expands around a corner at the throat to ambient pressure on one side and the central body or plug on the other side.

• For expansion deflection nozzle the same is achieved but by using an inverse geometry.

• A gas boundary is created-is an interface between the hot air and ambient pressure.

• During ascending flight the gas boundary expands outward , causes a change in pressure distribution.

• This allows for automatic and continuous altitude compensation.

• Nozzle modifications include truncated plugs , wall contour alteration.

Advantages It can be operated for different altitude conditions without danger of nozzle flow separation Here no over expansion losses are encountered High thrust performance over a wide range of

altitude

ApplicationsVenture star American 2 stage- to- orbit vehicle using Aero spike nozzle

Lighter nozzle Less cooling problems