Propulsion Exhausts

The combustion process is carried out in a thrust chamber or a motor case, and the reaction products are momentarily contained therein. The newly formed species are heterogeneous in composition and involve a wide variety of low molecular weight products. The temperature of these products is generally high, and it ranges from about 2,000°F (1,100°C) in gas generators to well over 8,000°F in advanced liquid propellant engines. The combustion products leave the chamber and are directed and expanded in a nozzle to obtain velocities from about 5,000 to 14,000 ft/sec. 

Cooling techniques Various methods have been developed to cope with high temperature and heating problems. They are based on absorptive, dissipative, and mass 

A form of cooling, and the one of prime interest, concerns ablative cooling. It is essentially a heat and mass transfer process in which mass is expended to achieve thermal dissipation, absorption, and blocking. The process is passive in nature, serves to control the surface temperature, and greatly restricts the flow of heat into the material substrate. As a result of these desirable attributes, ablative cooling (includes use of plastic compositions) has been widely used for thermal protection of solid propellant motors and less extensively in liquid propellant motors. 

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Plastics have found numerous uses in specialty areas such as hypersonic atmospheric flight and chemical propulsion exhaust systems. The particular plastic employed in these applications is based on the inherent properties of the plastics or the ability to combine it with another component material to obtain a balance of properties uncommon to either component. Some of the compositions and important properties of plastics are given in Tables 2-9 and 2-10 that have been developed over the years for use in flight vehicles and propulsion systems that are dependent upon chemical, mechanical, electrical, nuclear, and solar means for accelerating the working fluid by high temperatures. 

Control of nitrogen oxides ia aircraft exhaust is of increa sing concern because nitrogen oxides react with ozone ia the protective layer of atmosphere which exists ia the altitude region where supersonic aircraft operate. Research is under way to produce a new type of combustor which minimizes NO formation. It is an essential component of the advanced propulsion unit needed for a successflil supersonic transport fleet. 

Where propulsion is provided by diesel or gas turbine, it is common to use an auxiliary boiler in conjunction with a waste heat/heat recovery boiler (WH/HR boiler). The steam-HW mixture, produced by passing the exhaust engine gases over the HR boiler tubes, is piped to the auxiliary boiler steam drum and then mixes with auxiliary BW. All steam utilized by the ship is taken from the auxiliary boiler. 

Exhaust products and by-products that are discharged from a propulsion device form a moving cluster of gases and particles, called plume. High-temperature plumes emit electromagnetic waves over a wide spectrum of wavelengths. Since many propulsion devices operate fuel-rich in order to maximize the specific impulse, the plumes often contain some incompletely burned fuel species that may... 

Ducted rockets are intermediate between solid rockets and liquid ramjets in their propulsion characteristics. The propulsive force of soHd rockets is generated by the combustion of propellants composed of oxidizer and fuel components. Thus, no additional fuels or oxidizers need to be introduced from the atmosphere into the rocket motor. The momentum change of the exhaust gas from the nozzle attached to the aft-end of the combustion chamber is converted into the thrust for propulsion. On the other hand, the propulsive force of Hquid ramjets is generated by the combustion of a liquid hydrocarbon fuel with air introduced from the atmo-sphere.Ii] jjjg incoming air is compressed by a shock wave formed at the air-intake attached to the front end of the combustor. The air taken in from the atmosphere serves only as the oxidizer for the ramjets. The thrust is created by the momentum difference between the exhaust gas from the combustor and the air taken in from the atmosphere. 

BALLISTICS (INTERNAL) The science of internal ballistics is concerned with the propulsion of a projectile such as a shell along the tube of a mortar by gas pressure acting on the base of the shell, or, in the case of rockets, by the backward exhaust of the gas jet. 

Rocket Engine. A non-airbreathing reaction propulsion device that consists essentially of an injector, thrust chambers) and exhaust nozzle(s), and utilizes liquid fuels and oxidizers at controlled rates from which hot gases are generated by combustion and expanded thru a nozzle(s) (Ref 40a, p 125)... 

Introduction. In the absence of all contact with an external solid, a prime mover placed in a fluid of finite or even zero density can propel itself by ejecting a fluid or solid mass toward the rear. By convention we say that this mover is propelled by jet propulsion, although the propulsive thrust really results from the effects of pressure and friction exerted on the wall of the hollow interior of the mover by the solids or fluids moving in the interior toward the exhaust nozzle ... 

It is usually understood that a rocket motor is that part of the propulsion system in which the propellants are transformed into the exhaust jet, while a rocket engine is the entire system, ie, the rocket motor, the proplnt containers, pumps, etc. In conventional solid proplnt rockets, the motor and the engine happen to be the same piece of apparatus, but this is not so in liq proplnt rockets... 

Sufficient atomic particle research has been accomplished to warrant discussion of possible methods of applying energy available from particle mass annihilation to rocket propulsion. Complete conversion of matter to energy would allow exhaust velocities near that of light to be obtained from a propulsion device. Antimatter, by definition is matter made up of antiparticles, such as antineutrons, negatrons (antiprotons), and positrons (anheledrons). An annihilation property is known to exist between particles with one particle termed the anhparticle of the other. 

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