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

Info

Neutral if ends are unrestricted, otherwise progressive. ftHas up to 4 or sometimes 8 sliver mass and thus a gradual thrust termination. NA not applicable or not available. Neutral if ends are unrestricted, otherwise progressive. ftHas up to 4 or sometimes 8 sliver mass and thus a gradual thrust termination. NA not applicable or not available. extended by alterations. The movement of the center of gravity influences the flight stability of the vehicle. Relative values of this CG shift are also...

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...

Oms

Thrust (per nozzle) (lbf) Number of thrusters per pod Thrust chamber cooling Chamber pressure, nominal (psi) Specific impulse (vacuum nominal) (sec) Nozzle area ratio Mixture ratio (oxide fuel mass flow) Burn time, minimum (sec) Burn time, maximum (sec) Burn time, cumulative (sec) Number of starts, cumulative (sec) Oxidizer (N204) weight in tank (lb) Fuel (MMH) weight in tank (lb) Number of oxidizer fuel tanks Propellant tank volume, each tank (ft3) Ullage volume, nominal (full tank) (ft3) Tank...

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

All Types Rocket Engine

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...

Gas Pressure Feed Systems

Space Shuttle Main Propulsion Engine

One of the simplest and most common means of pressurizing the propellants is to force them out of their respective tanks by displacing them with high-pressure gas. This gas is fed into the propellant tanks at a controlled pressure, thereby giving a controlled propellant discharge. Because of their relative simplicity, the rocket engines with pressurized feed systems can be very reliable. Reference 6-3 includes a design guide for pressurized gas systems. A simple pressurized feed system is shown...

Nuclear Rocket Engines

Diagram Solid Fuel Ram Jet

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

Flight Arc

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...

Tank Pressurization

Subsystems for pressurizing tanks are needed for both of the two types of feed systems, namely pressure feed systems and pump feed systems. The tank pressures for the first type are usually between 200 and 1800 psi and for the second between 10 and 50 psig. Refs. 6-1, 6-3 to 6-5 give further descriptions. Inert gases such as helium or nitrogen are the most common method of pressuriza-tion. In pump feed systems a small positive pressure in the tank is needed to suppress pump cavitation. For...

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

Propellant Dewetting

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

Casting Molds For Double Base Propellant

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...

Combinations of Ducted Jet Engines and Rocket Engines

Rocket Engine Fuel Tank

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

Solid Propellant Rocket Motors

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...

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...

Problems

Various Types Propulsion Systems

Acceleration in multiples of earth gravity g0 or thrust to vehicle weight ratio FIGURE 2-5. Exhaust velocities as a function of typical vehicle accelerations. Regions indicate approximate performance values for different types of propulsion systems. The mass of the vehicle includes the propulsion system, but the payload is assumed to be zero. Acceleration in multiples of earth gravity g0 or thrust to vehicle weight ratio FIGURE 2-5. Exhaust velocities as a function of typical vehicle...

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...