Contents
  1. NPTEL :: Mechanical Engineering - Rocket Propulsion
  2. inrangedi.cf
  3. Biblarz O., Sutton George P. (eds.) Rocket Propulsion Elements
  4. Physics of Electric Propulsion

NPTEL provides E-learning through online Web and Video courses various streams. The design process for solid propellant rocket motors is presented of the governing laws of rocket propulsion and utilization of important propulsion theories. Modules. 1. Rocket Propulsion Fundamentals. 2. LRE Applications. 3. Liquid Propellants. 4. Engine Power Cycles. 5. Engine Components.

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Rocket Propulsion Pdf

Rocket propulsion elements: an introduction to the engineering of This new edition concentrates on the subject of rocket propulsion, its basic. FUNDAMENTALS OF ROCKET PROPULSION Unit 2 1 2 Syllabus Operating principle, Rocket equation, Specific. Rocket Propulsion. In the section about the rocket equation we explored some of the issues surrounding the performance of a whole rocket. What we didn't.

A Delta IV Heavy during liftoff. Rockets create thrust by expelling mass backward at high velocity. The thrust produced can be calculated by multiplying the mass flow rate of the propellants by their exhaust velocity relative to the rocket specific impulse. A rocket can be thought of as being accelerated by the pressure of the combusting gases against the combustion chamber and nozzle , not by "pushing" against the air behind or below it. Rocket engines perform best in outer space because of the lack of air pressure on the outside of the engine. In space it is also possible to fit a longer nozzle without suffering from flow separation. As such, both an oxidizing agent and a reducing agent must be present in the fuel mixture. Decomposition, such as that of highly unstable peroxide bonds in monopropellant rockets, can also be the source of energy. As combustion takes place, the liquid propellant mass is converted into a huge volume of gas at high temperature and pressure. This exhaust stream is ejected from the engine nozzle at high velocity, creating an opposing force that propels the rocket forward in accordance with Newton's laws of motion. Solid rockets use propellant in the solid phase , liquid fuel rockets use propellant in the liquid phase , gas fuel rockets use propellant in the gas phase , and hybrid rockets use a combination of solid and liquid or gaseous propellants.

Turbopumps are particularly troublesome due to high performance requirements.

This combination is widely regarded as the most practical for boosters that lift off at ground level and therefore must operate at full atmospheric pressure. LOX and liquid hydrogen. LOX and liquid methane will be used on several rockets in development, including Vulcan and New Glenn.

Used in military, orbital, and deep space rockets because both liquids are storable for long periods at reasonable temperatures and pressures. This combination is hypergolic , making for attractively simple ignition sequences.

The major inconvenience is that these propellants are highly toxic and require careful handling. Monopropellants such as hydrogen peroxide , hydrazine , and nitrous oxide are primarily used for attitude control and spacecraft station-keeping where their long-term storability, simplicity of use, and ability to provide the tiny impulses needed outweighs their lower specific impulse as compared to bipropellants.

Hydrogen peroxide is also used to drive the turbopumps on the first stage of the Soyuz launch vehicle. In chemical rockets, unburned fuel or oxidizer represents the loss of chemical potential energy, which reduces the specific energy.

However, most rockets run fuel-rich mixtures, which result in lower theoretical exhaust velocities. The nozzle of the rocket converts the thermal energy of the propellants into directed kinetic energy. This conversion happens in the time it takes for the propellants to flow from the combustion chamber through the engine throat and out the nozzle, usually on the order of one millisecond. Molecules store thermal energy in rotation, vibration, and translation, of which only the latter can easily be used to add energy to the rocket stage.

Molecules with fewer atoms like CO and H2 have fewer available vibrational and rotational modes than molecules with more atoms like CO2 and H2O.

Consequently, smaller molecules store less vibrational and rotational energy for a given amount of heat input, resulting in more translation energy being available to be converted to kinetic energy. The resulting improvement in nozzle efficiency is large enough that real rocket engines improve their actual exhaust velocity by running rich mixtures with somewhat lower theoretical exhaust velocities.

High expansion rockets operating in a vacuum see a much smaller effect, and so are run less rich.

NPTEL :: Mechanical Engineering - Rocket Propulsion

Because fuel-rich combustion products are less chemically reactive corrosive than oxidizer-rich combustion products, a vast majority of rocket engines are designed to run fuel-rich.

This can be exploited with designs that adjust the oxidizer to fuel ratio along with overall thrust throughout a flight to maximize overall system performance. The fuel tankage, plumbing, and pump must be correspondingly larger.

This increases the vehicle's dry mass, reducing performance. Liquid hydrogen is also relatively expensive to produce and store, and causes difficulties with design, manufacture, and operation of the vehicle.

However, liquid hydrogen is extremely well suited to upper stage use where Isp is at a premium and thrust to weight ratios are irrelevant. This means that vehicles with dense-fueled booster stages reach orbit earlier, minimizing losses due to gravity drag and reducing the effective delta-v requirement.

Studies in the s proposed single stage to orbit vehicles using this technique. The main engines burned a fuel-rich hydrogen and oxygen mixture, operating continuously throughout the launch but providing the majority of thrust at higher altitudes after SRB burnout.

The fluid oxidizer can make it possible to throttle and restart the motor just like a liquid-fueled rocket.

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Hybrid rockets can also be environmentally safer than solid rockets since some high-performance solid-phase oxidizers contain chlorine specifically composites with ammonium perchlorate , versus the more benign liquid oxygen or nitrous oxide often used in hybrids. This is only true for specific hybrid systems. There have been hybrids which have used chlorine or fluorine compounds as oxidizers and hazardous materials such as beryllium compounds mixed into the solid fuel grain.

Because just one constituent is a fluid, hybrids can be simpler than liquid rockets depending motive force used to transport the fluid into the combustion chamber. Fewer fluids typically mean fewer and smaller piping systems, valves and pumps if utilized. The first, shared with solid rocket motors, is that the casing around the fuel grain must be built to withstand full combustion pressure and often extreme temperatures as well. However, modern composite structures handle this problem well, and when used with nitrous oxide and a solid rubber propellant HTPB , relatively small percentage of fuel is needed anyway, so the combustion chamber is not especially large.

In solid propellants, the oxidizer and fuel are mixed in a factory in carefully controlled conditions. Liquid propellants are generally mixed by the injector at the top of the combustion chamber, which directs many small swift-moving streams of fuel and oxidizer into one another. Liquid-fueled rocket injector design has been studied at great length and still resists reliable performance prediction.

In a hybrid motor, the mixing happens at the melting or evaporating surface of the fuel. The mixing is not a well-controlled process and generally, quite a lot of propellant is left unburned, [11] which limits the efficiency of the motor. The combustion rate of the fuel is largely determined by the oxidizer flux and exposed fuel surface area.

This combustion rate is not usually sufficient for high power operations such as boost stages unless the surface area or oxidizer flux is high. Too high of oxidizer flux can lead to flooding and loss of flame holding that locally extinguishes the combustion. Additionally, as the burn continues, the hole down the center of the grain the 'port' widens and the mixture ratio tends to become more oxidizer rich.

For military use, ease of handling and maintenance have driven the use of solid rockets. For orbital work, liquid fuels are more efficient than hybrids and most development has concentrated there. There has recently been an increase in hybrid motor development for nonmilitary suborbital work: Several universities have recently experimented with hybrid rockets.

This exhaust stream is ejected from the engine nozzle at high velocity, creating an opposing force that propels the rocket forward in accordance with Newton's laws of motion. Solid rockets use propellant in the solid phase , liquid fuel rockets use propellant in the liquid phase , gas fuel rockets use propellant in the gas phase , and hybrid rockets use a combination of solid and liquid or gaseous propellants.

Biblarz O., Sutton George P. (eds.) Rocket Propulsion Elements

Propellant combustion occurs inside the motor casing, which must contain the pressures developed. Solid rockets are typically have higher thrust, less specific impulse , shorter burn times, and a higher mass than liquid rockets, and additionally cannot be stopped once lit. This relationship is described by the rocket equation. Exhaust velocity is dependent on the propellant and engine used and closely related to specific impulse , the total energy delivered to the rocket vehicle per unit of propellant mass consumed.

Mass ratio can also be affected by the choice of a given propellant. Upper stages, which mostly or only operate in the vacuum of space, tend to use the high energy, high performance, low density liquid hydrogen fuel. These primary ingredients must include fuel and oxidizer and often also include binders and plasticizers.

All components are macroscopically indistinguishable and often blended as liquids and cured in a single batch. Ingredients can often have multiple roles. For example, RDX is both a fuel and oxidizer while nitrocellulose is a fuel, oxidizer, and plasticizer. In the case of gunpowder a pressed composite without a polymeric binder the fuel is charcoal, the oxidizer is potassium nitrate, and sulphur serves as a reaction catalyst while also being consumed to form a variety of reaction products such as potassium sulfide.

High propellant density makes for compact size as well. These features plus simplicity and low cost make solid propellant rockets ideal for military applications. The Space Shuttle and many other orbital launch vehicles use solid-fueled rockets in their boost stages solid rocket boosters for this reason. As a result, the overall performance of solid upper stages is less than liquid stages even though the solid mass ratios are usually in the.

The high mass ratios possible with these unsegmented solid upper stages is a result of high propellant density and very high strength-to-weight ratio filament-wound motor casings. Solid rockets can be vented to extinguish combustion or reverse thrust as a means of controlling range or accommodating warhead separation.

Casting large amounts of propellant requires consistency and repeatability to avoid cracks and voids in the completed motor. The blending and casting take place under computer control in a vacuum, and the propellant blend is spread thin and scanned to assure no large gas bubbles are introduced into the motor. The combustion process is dependent on the surface area of the fuel. Voids and cracks represent local increases in burning surface area, increasing the local temperature, which increases the local rate of combustion.

This positive feedback loop can easily lead to catastrophic failure of the case failure or nozzle. The Song Chinese first used gunpowder in during the military siege of Kaifeng. The mixture is formed as a thickened liquid and then cast into the correct shape and cured into a firm but flexible load-bearing solid. Historically the tally of APCP solid propellants is relatively small.

The military, however, uses a wide variety of different types of solid propellants some of which exceed the performance of APCP. A comparison of the highest specific impulses achieved with the various solid and liquid propellant combinations used in current launch vehicles is given in the article on solid-fuel rockets.

All solid-fueled ICBMs on both sides had three initial solid stages, and those with multiple independently targeted warheads had a precision maneuverable bus used to fine tune the trajectory of the re-entry vehicles. Advantages of liquid propellant[ edit ] Liquid-fueled rockets have higher specific impulse than solid rockets and are capable of being throttled, shut down, and restarted. Only the combustion chamber of a liquid-fueled rocket needs to withstand high combustion pressures and temperatures.

Cooling can be done regeneratively with the liquid propellant. On vehicles employing turbopumps , the propellant tanks are at very much lower pressure than the combustion chamber, decreasing tank mass. For these reasons, most orbital launch vehicles use liquid propellants. Several practical liquid oxidizers liquid oxygen , nitrogen tetroxide , and hydrogen peroxide are available which have better specific impulse than the ammonium perchlorate used in most solid rockets when paired with suitable fuels.

Some gases, notably oxygen and nitrogen, may be able to be collected from the upper atmosphere , and transferred up to low-Earth orbit for use in propellant depots at substantially reduced cost. Turbopumps are particularly troublesome due to high performance requirements.

Physics of Electric Propulsion

This combination is widely regarded as the most practical for boosters that lift off at ground level and therefore must operate at full atmospheric pressure. LOX and liquid hydrogen. LOX and liquid methane will be used on several rockets in development, including Vulcan and New Glenn. Used in military, orbital, and deep space rockets because both liquids are storable for long periods at reasonable temperatures and pressures.

This combination is hypergolic , making for attractively simple ignition sequences. The major inconvenience is that these propellants are highly toxic and require careful handling.

Monopropellants such as hydrogen peroxide , hydrazine , and nitrous oxide are primarily used for attitude control and spacecraft station-keeping where their long-term storability, simplicity of use, and ability to provide the tiny impulses needed outweighs their lower specific impulse as compared to bipropellants.

Hydrogen peroxide is also used to drive the turbopumps on the first stage of the Soyuz launch vehicle. In chemical rockets, unburned fuel or oxidizer represents the loss of chemical potential energy, which reduces the specific energy.

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