## Gaseous Propellants

Cold gas propellants have been used successfully for reaction control systems (RCS) for perhaps 50 years. The engine system is simple, consisting of one or more high-pressure gas tanks, multiple simple metal nozzles (often aluminum or plastic), an electrical control valve with each nozzle, a pressure regulator, and provisions for filling and venting the gas. The tank size will be smaller if the tank pressures are high. Pressures are typically between 300 and 1000 MPa (about 300 to 10,000 psi)....

## Info

Flow rate, kg sec 177 836 403.5 Mixture ratio, O F 53.8 54.3 21.5 Chamber pressure, kg cm2 325 546 243 Number of preburners 1 2 1 Flow rate, kg sec 177 836 403.5 Mixture ratio, O F 53.8 54.3 21.5 Chamber pressure, kg cm2 325 546 243 Number of preburners 1 2 1 Fuel flow to precombustor goes through a small second-stage pump. (Courtesy of NPO Energomash, Moscow.) meters (chamber pressure, thrust, specific impulse, weight, propellant combination, nozzle area ratio, dimensions, etc.) which...

## Thrust Chambers

The thrust chamber is the key subassembly of a rocket engine. Here the liquid propellants are metered, injected, atomized, vaporized, mixed, and burned to form hot reaction gas products, which in turn are accelerated and ejected at high velocity (see Refs. 6-1 and 6-2). This chapter describes thrust chambers, their components, cooling, ignition, and heat transfer. A rocket thrust chamber assembly (Figs. 8-1 and 8-2) has an injector, a combustion chamber, a supersonic nozzle, and mounting...

## Problems

How much total heat per second can be absorbed in a thrust chamber with an inside wall surface area of 0.200 m2 if the coolant is liquid hydrogen and the coolant temperature does not exceed 145 K in the jacket Coolant flow is 2 kg sec. What is the average heat transfer rate per second per unit area Use the data from Table 7-1 and the following Heat of vaporization near boiling point 446 kJ kg Thermal conductivity (gas at 21 K) 0.013 W m-K 2. During a static test a certain steel thrust chamber...

## Space Launch Vehicles

Between the first space launch in 1957 and the end of 1998 approximately 4102 space launch attempts have taken place in the world and all but about 129 were successful (see Ref. 1-17). Space launch vehicles or space boosters can be classified broadly as expendable or recoverable reusable. Other bases of classification are the type of propellant (storable or cryogenic liquid or solid propellants), number of stages (single-stage, two-stage, etc.), size mass of pay-loads or vehicles, and manned or...

## Starting And Ignition

The starting of a thrust chamber has to be controlled so that a timely and even ignition of propellants is achieved and the flow and thrust are built up smoothly and quickly to their rated value (see Ref. 6-1). The initial propellant flow is less than full flow, and the starting mixture ratio is usually different from the operating mixture ratio. A low initial flow prevents an excessive accumulation of unignited propellants in the chamber. The starting injection velocity is low, the initial...

## Propellant Characteristics

The propellant selection is critical to rocket motor design. The desirable propellant characteristics are listed below and are discussed again in other parts of this book. The requirements for any particular motor will influence the priorities of these characteristics 1. High performance or high specific impulse really this means high gas temperature and or low molecular mass. 2. Predictable, reproducible, and initially adjustable burning rate to fit the need of the grain design and the...

## Aerodynamic Effect Of Exhaust Plumes

The effect of rocket exhaust jets or plumes on the aerodynamic characteristics of a missile is usually to decrease the vehicle drag at supersonic missile speeds and to increase it at subsonic speeds. On subsonic vehicles, a supersonic rocket plume acts very much like an ejector and sucks adjacent air into its path. This affects vehicles where the rocket is located on a tapering aft end. The ejector action of the flame accelerates the adjacent air, thereby increasing the skin friction locally...

## Attitude Control And Side Maneuvers With Solid Propellant Rocket Motors

A clever attitude control (also called reaction control) system with solid propellants is used on some ballistic missiles. Its hot reaction gas has a low enough temperature so that uncooled hardware can be used for long durations. Ammonium nitrate composite propellant (mentioned as gas generator propellants in Tables 12-1 and 12-2) or a propellant consisting of a nitramine (RDX or HMX, described in Chapter 12) with a polymer binding are suitable. The version shown schematically in Fig. 11-27...

## Nozzle Alignment

When the thrust line or direction does not intersect the center of mass of a flying vehicle, a turning moment will tend to rotate a vehicle in flight. Turning moments are desirable and necessary for the controlled turning or attitude control of a vehicle as is routinely done by means of the deflection of the thrust vector, aerodynamic fins, or by separate attitude control rocket engines. However, this turning is undesirable when its magnitude or direction is not known this happens when a fixed...

## Chemical Rocket Propellant Performance Analysis

In Chapter 3, simplified one-dimensional performance relations were developed. They require a knowledge of the composition of the hot rocket gas and the properties of the propellant reaction products, such as their combustion temperature Tx, average molecular mass 93 , the specific heat ratio or the enthalpy change (hx h2). This chapter discusses several theoretical approaches to determine these thermochemical properties for a given composition of propellant, chamber pressure, nozzle shape, and...

## References

Design of Liquid Propellant Rocket Engines, Revised edition, AIAA, 1992, 437 pages. 6-2. G. G. Gakhun, V. I. Baulin, et ala., Construction and Design of Liquid Propellant Rocket Engines (in Russian), Konstruksiya i Proyektirovaniye Zhidkostniyk Raketnykh Dvigateley, Mashinostroyeniye, Moscow, 1989, 424 pages. 6-3. C. J. G. Dixon and J. G. B. Marshall, Mathematical Modelling of Bipropellant Combined Propulsion Subsystems, AIAA Paper 90-2303, 26th Joint...

## Engine Controls

All liquid propellant rocket engines have controls to accomplish some or all of the following tasks 4. Maintain programmed operation (predetermined constant or randomly varied thrust, preset propellant mixture ratio and flow). 5. When safety devices sense an impending malfunction or a critical condition of the vehicle or the engine, the control system will automatically change the engine operating conditions to remedy the defected defect, or cause a safe emergency engine shutdown. Only some of...

## Motor Case

The case not only contains the propellant grain, but also serves as a highly loaded pressure vessel. Case design and fabrication technology has progressed to where efficient and reliable motor cases can be produced consistently for any solid rocket application. Most problems arise when established technology is used improperly or from improper design analysis, understating the requirements, or improper material and process control, including the omission of nondestructive tests at critical...

## Ignition Process

This section is concerned with the mechanism or the process for initiating the combustion of a solid propellant grain. Specific propellants that have been successfully used for igniters have been mentioned in Section 12.5. The hardware, types, design, and integration of igniters into the motor are described in Section 14.4. Chapters 2, 5, and 6 of Ref. 13-1 review the state of the art of ignition, data from experiments, and analytical models, which have been found to be mostly unreliable. Solid...

## Chamber Pressure

Simplified view of the RS-68 rocket engine with a gas generator cycle. For engine data see Table 10-3. (Courtesy of The Boeing Company, Rocketdyne Propulsion and Power.) Regeneratlvely cooled thrust chamber and nozzle Regeneratlvely cooled thrust chamber and nozzle Fuel cooidown and pressure relief valve FIGURE 6-11. Schematic flow diagram of the RL10B-2 upper stage rocket engine. For data see Table 8-1. (Courtesy of Pratt & Whitney, a division of United Technologies.) Fuel...

## Solid Propellant Rocket Fundamentals

This is the first of four chapters on solid propellant rockets. It discusses the burning rates, motor performance, grain configurations, and structural analysis. In solid propellant rocket motors and the word motor is as common to solid rockets as the word engine is to liquid rockets the propellant is contained and stored directly in the combustion chamber, sometimes hermetically sealed in the chamber for long-time storage (5 to 20 years). Motors come in many different types and sizes, varying...

## Liquid Propellant Rocket Engine Fundamentals197

Propellant Feed Systems 203 6.3. Gas Pressure Feed Systems 205 6.6. Turbopump Feed Systems and Engine Cycles 221 6.7. Flow and Pressure Balance 227 6.8. Rocket Engines for Maneuvering, Orbit Adjustments, or Attitude Control 228 6.9. Valves and Pipe Lines 232 6.10. Engine Support Structure 235 Problems 236 Symbols 238 References 239

## Flight Vehicles

As mentioned, the vast majority of rocket propelled vehicles are simple, single stage, and use solid propellant rocket motors. Most are used in military applications, as described in the next section. This section discusses more sophisticated multistage space launch vehicles and mentions others, such as large ballistic missiles (often called strategic missiles) and some sounding rockets. All have some intelligence in their guidance and navigation system. The total number of multistage rocket...

## Other Rocket Propulsion Concepts

Several technologies exist for harnessing solar energy to provide the power for spacecraft and also to propel spacecraft using electrical propulsion. Solar cells generate electric power from the sun's radiation. They are well developed and have been successful for several decades. Most electric propulsion systems have used solar cells for their power supply. FIGURE 1-10. Simplified diagram of a rail accelerator for self-induced magnetic acceleration of a current-carrying plasma. When the...

## Engine System Calibration

Although an engine has been designed to deliver a specific performance (F, 7j, m, r), a newly manufactured engine will not usually perform precisely at these nominal parameters. If the deviation from the nominal performance values is more than a few percent, the vehicle will probably not complete its intended flight course. There are several reasons for these deviations. Because of unavoidable dimensional tolerances on the hardware, the flow-pressure profile or the injector impingement...

## Sample Thrust Chamber Design Analysis

This example shows how a thrust chamber is strongly influenced by the overall vehicle system requirements or the mission parameters and the vehicle design. As outlined in the Design Section of Chapter 10 and in the discussion of the selection of propulsion systems in Chapter 17, each engine goes through a series of rationalizations and requirements that define its key parameters and its design. In this example we describe how the thrust chamber parameters are derived from the vehicle and engine...

## Classification

Processed modern propellants can be classified in several ways, as described below. This classification is not rigorous or complete. Sometimes the same propellant will fit into two or more of the classifications. 1. Propellants are often tailored to and classified by specific applications, such as space launch booster propellants or tactical missile propellants each has somewhat specific chemical ingredients, different burning rates, different physical properties, and different performance....

## Basic Performance Relations

One basic performance relation is derived from the principle of conservation of matter. The propellant mass burned per unit time has to equal the sum of the change in gas mass per unit time in the combustion chamber grain cavity and the mass flowing out through the exhaust nozzle per unit time. The term on the left side of the equation gives the mass rate of gas generation from Eq. 11-1. The first term on the right gives the change in propellant mass in the gas volume of the combustion chamber,...

## Propellant Burning Rate

The rocket motor's operation and design depend on the combustion characteristics of the propellant, its burning rate, burning surface, and grain geometry. The branch of applied science describing these is known as internal ballistics the effect of grain geometry is treated in Section 11.3. The burning surface of a propellant grain recedes in a direction essentially perpendicular to the surface. The rate of regression, usually expressed in cm sec, mm sec, or in. sec, is the burning rate r. In...

## Dfx

Standard T-burner and its longitudinal mode standing waves (pressure and velocity). Use of the T-burner for assessing the stability of a full-scale solid rocket presupposes valid theoretical models of the phenomena occurring in both the T-burner and the actual rocket motor these theories are still not fully validated. In addition to assessing solid rocket motor combustion stability, the T-burner also is used to evaluate new propellant formulations and the importance of seemingly...

## Rocket Propulsion

Rocket propulsion systems can be classified according to the type of energy source (chemical, nuclear, or solar), the basic function (booster stage, sustained attitude control, orbit station keeping, etc.), the type of vehicle (aircraft, missile, assisted take-off, space vehicle, etc.), size, type of propellant, type of construction, or number of rocket propulsion units used in a given vehicle. Each is treated in more detail in subsequent chapters. Another way is to classify by the method of...

## Engine Design

The approach, methods, and resources used for rocket engine preliminary design and final design are usually different for each design organization and for each major type of engine. They also differ by the degree of novelty. 1. A totally new engine with new major components and some novel design concepts will result in an optimum engine design for a given application, but it is usually the most expensive and longest development approach. One of the major development costs is usually in...

## Propellant Grain And Grain Configuration

The grain is the shaped mass of processed solid propellant inside the rocket motor. The propellant material and geometrical configuration of the grain determine the motor performance characteristics. The propellant grain is a cast, molded, or extruded body and its appearance and feel is similar to that of hard rubber or plastic. Once ignited, it will burn on all its exposed surfaces to form hot gases that are then exhausted through a nozzle. A few rocket motors have more than one grain inside a...

## Injectors

The functions of the injector are similar to those of a carburetor of an internal combustion engine. The injector has to introduce and meter the flow of liquid propellants to the combustion chamber, cause the liquids to be broken up into small droplets (a process called atomization), and distribute and mix the propellants in such a manner that a correctly proportioned mixture of fuel and oxidizer will result, with uniform propellant mass flow and composition over the chamber cross section. This...

## Flight Maneuvers

In this section we describe different flight maneuvers and relate them to specific propulsion system types. The three categories of maneuvers are 1. In translation maneuvers the rocket propulsion thrust vector goes through the center of gravity of the vehicle. The vehicle momentum is changed in the direction of the flight velocity. An example of several powered (trans-lational maneuvers) and unpowered (coasting) segments of a complex space flight trajectory is shown in schematic, simplified...

## Propellant Tanks

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. There are also one or more high-pressure gas tanks, the gas being used to pressurize the propellant tanks. Tanks can be arranged in a variety of ways, and the tank design can be used to exercise some control over the change in the location of the vehicle's center of gravity. Typical...

## Conditions For 5000n Thrust

What is the ratio of the burning area to the nozzle area for a solid propellant motor with these characteristics Propellant specific gravity 1.71 Temperature sensitivity ap 0.007 (K)1 2. Plot the burning rate against chamber pressure for the motor in Problem 1 using Eq. 11-3 between chamber pressures of 11 and 20 MPa. 3. What would the area ratio Ab At in Problem 1 be if the pressure were increased by 10 (Use curve from Problem 2.) 4. Design a simple rocket motor for the conditions given in...

## Combustion Instability

There seem to be two types of combustion instability a set of acoustic resonances or pressure oscillations, which can occur with any rocket motor, and a vortex shedding phenomenon, which occurs only with particular types of grains. When a solid propellant rocket motor experiences unstable combustion, the pressure in the interior gaseous cavities (made up by the volume of the port or perforations, fins, slots, conical or radial groves) oscillates by at least 5 and often by more than 30 of the...

## System Integration And Engine Optimization

Rocket engines are part of a vehicle and must interact and be integrated with other vehicle subsystems. There are interfaces (connections, wires, or pipelines) between the engine and the vehicle's structure, electric power system, flight control system (commands for start or thrust vector control), and ground support system (check-out or propellant supply). The engine also imposes limitations on vehicle components by its heat emissions, noise, and vibrations. Integration means that the engine...

## Propellant Feed Systems

The propellant feed system has two principal functions to raise the pressure of the propellants and to feed them to one or more thrust chambers. The energy for these functions comes either from a high-pressure gas, centrifugal pumps, or a combination of the two. The selection of a particular feed system and its components is governed primarily by the application of the rocket, the requirements mentioned at the beginning of this chapter, duration, number or type of thrust chambers, past...

## Nuclear Rocket Engines

Three different types of nuclear energy sources have been investigated for delivering heat to a working fluid, usually liquid hydrogen, which subsequently can be expanded in a nozzle and thus accelerated to high ejection velocities (6000 to 10,000 m sec). However, none can be considered fully developed today and none have flown. They are the fission reacWr, the FIGURE 1-7. Elements of an air-launched missile with integral rocket-ramjet propulsion. After the solid propellant has been consumed in...

## Valves And Pipe Lines

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. Table 6-6 gives several key classification categories for rocket engine valves. Any one engine will use only some of the valves listed here. The art of designing and making valves is based, to a...

## Turbopump Feed Systems And Engine Cycles

The principal components of a rocket engine with one type of turbopump system are shown in the simplified diagram of Fig. 1-4. Here the propellants are pressurized by means of pumps, which in turn are driven by turbines. These turbines derive their power from the expansion of hot gases. Engines with turbopumps are preferred for booster and sustainer stages of space launch vehicles, long-range missiles, and in the past also for aircraft performance augmentation. They are usually lighter than...

## Combustion Chamber And Nozzle

The combustion chamber is that part of a thrust chamber where the combustion or burning of the propellant takes place. The combustion temperature is much higher than the melting points of most chamber wall materials. Therefore it is necessary either to cool these walls (as described in a later section of this chapter) or to stop rocket operation before the critical wall areas become too hot. If the heat transfer is too high and thus the wall temperatures become locally too high, the thrust...

## Propellant Grain Stress And Strain

The objective of stress analysis of rocket motors is to design the configuration of the grain, the liners, or the grain support in such a way that excessive stresses or excessive strains will not occur and so that there will be no failure. Static and dynamic loads and stresses are imposed on the propellant grains during manufacture, transportation, storage, and operation. Structurally, a rocket motor is a thin shell of revolution (motor case) almost completely filled with a vis- coelastic...

## Analysis Of Nozzle Expansion Processes

There are several methods for analyzing the nozzle flow, depending on the assumptions made for chemical equilibrium, nozzle expansion, particulates, or energy losses. Several are outlined in Table 5-3. Once the gases reach the nozzle, they experience an adiabatic, reversible expansion process which is accompanied by a drop in temperature and pressure and a conversion of thermal energy into kinetic energy. Several increasingly more complicated methods have been used for the analysis of the...

## Liquid Propellant Rocket Engine Fundamentals

This is the first of five chapters devoted to liquid propellant rocket engines. It gives an overview of the engines a definition of various propellants, engine performance, propellant budget , and of the smaller reaction control engines. It also presents several of their principal subsystems, such as two types of feed systems including engine cycles , propellant tanks and their pressurization subsystems, valves and piping systems, and engine structures. Chapter 7 covers liquid propellants in...

## Propellant Processing And Manufacture

The manufacture of solid propellant involves complex physical and chemical processes. In the past, propellant has been produced by several different processes, including the compaction or pressing of powder charges, extrusion of propellant through dies under pressure using heavy presses, and mixing with a solvent which is later evaporated. Even for the same type of propellant e.g., double-base, composite, or composite double-base the fabrication processes are usually not identical for different...

## Exhaust Velocity

The effective exhaust velocity as defined by Eq. 2-6 applies to all rockets that thermodynamically expand hot gas in a nozzle and, indeed, to all mass expulsion systems. From Eq. 2-14 and for constant propellant mass flow this can be modified to Equation 2-6 shows that c can be determined from thrust and propellant flow measurements. When p2 Pi, the effective exhaust velocity c is equal to the average actual exhaust velocity of the propellant gases v2. When p2 p3 then c v2. The second term of...

## Combinations of Ducted Jet Engines and Rocket Engines

The Tomahawk surface-to-surface missile uses two stages of propulsion in sequence. The solid propellant rocket booster lifts the missile away from its launch platform and is discarded after its operation. A small turbojet engine sustains the low level flight at nearly constant speed toward the target. A ducted rocket, sometimes called an air-augmented rocket, combines the principles of rocket and ramjet engines it gives higher performance specific impulse than a chemical rocket engine, while...

## Chemical Rocket Propulsion

The energy from a high-pressure combustion reaction of propellant chemicals, usually a fuel and an oxidizing chemical, permits the heating of reaction product gases to very high temperatures 2500 to 4100 C or 4500 to 7400 F . These gases subsequently are expanded in a nozzle and accelerated to high velocities 1800 to 4300 m sec or 5900 to 14,100 ft sec . Since these gas temperatures are about twice the melting point of steel, it is necessary to cool or insulate all the surfaces that are exposed...

## Symbols

C effective exhaust velocity, m sec ft sec cp specific heat at constant pressure, J kg-K Btu lbm-R cs specific heat of solid, J kg-K Btu lbm-R cv specific heat at constant volume, J kg-K Btu lbm-R c characteristic velocity, m sec ft sec CD discharge coefficient 1 c , sec m sec ft go standard sea level gravitational acceleration, 9.8066 m sec2 h enthalpy per unit mass, J kg Btu lbm Is specific impulse, sec or N-sec3 kg-m Ibf-sec lbm J mechanical equivalent of heat J 4.186 J cal in SI units or 1...

## Summary Of Thermodynamic Relations

In this section we review briefly some of the basic relationships needed for the development of the nozzle flow equations. Rigorous derivations and discussions of these relations can be found in many thermodynamics or fluid dynamics texts, such as Refs. 3-1 and 3-2. The principle of conservation of energy can be readily applied to the adia-batic, no shaft-work process inside the nozzle. Furthermore, without shocks or friction, the flow entropy change is zero. The concept of enthalpy is useful...

## Nozzle Theory And Thermodynamic Relations

Thermodynamic relations of the processes inside a rocket nozzle and chamber furnish the mathematical tools needed to calculate the performance and determine several of the key design parameters of rocket propulsion systems. They are useful as a means of evaluating and comparing the performance of various rocket systems they permit the prediction of the operating performance of any rocket unit that uses the thermodynamic expansion of a gas, and the determination of several necessary design...

## Ideal Rocket

The concept of ideal rocket propulsion systems is useful because the relevant basic thermodynamic principles can be expressed as simple mathematical relationships, which are given in subsequent sections of this chapter. These equations theoretically describe a quasi-one-dimensional nozzle flow, which corresponds to an idealization and simplification of the full two- or three-dimensional equations and the real aerothermochemical behavior. However, with the assumptions and simplifications stated...