BRIEF GLOSSARY OF SUCCESSFUL ROCKET PROPULSION
1) NUCLEAR FISSION ROCKETS (solid core nuclear rockets):-
Solid core nuclear rockets work by taking liquid hydrogen and pumping it to the reactor through a jacket surrounding the rocket engine. This pumping process helps cool the rocket, and it also preheats the liquid hydrogen. Hundreds of narrow channels pass through the nuclear reactor. As the liquid hydrogen flows through these channels, heat from the reactor changes the fuel into rapidly expanding gas. The gas flows through the exhaust nozzle at speeds up to 35,400 kilometers per hour. A diagram of a solid core rocket. Several tests were carried out during the 1960s with nuclear rockets. The most well known of these are the Nuclear Engine for Rocket Vehicle Applications (NERVA) tests. NERVA involved the Los Alamos laboratory, Westinghouse, Aero jet, and other industrial partners. Together, they were able to build and test a solid core rocket with a thrust of 250,000 pounds, and a specific impulse (Isp) of 850 seconds, nearly twice the best Isp of chemical rockets (specific impulse is a "miles per gallon" for rockets). Research into nuclear rockets proceeds at a slow but steady pace. Most of the work is done at Los Alamos, where nuclear rockets originated. Most of the problems that the scientists are trying to solve now are how to build a nozzle and combustion chamber that can withstand the high temperatures of a gas core rocket, and how to contain the uranium plasma that forms. If viable nuclear rockets are ever developed, they would have the possibility of opening the solar system to manned space flight. A trip to Mars would easily be within our grasp.
2) ION ROCKETS:-
The ion rocket does away with the hot, fiery blast of chemical and nuclear rocket engines. Instead, it uses a small electrostatic grid to accelerate ions to very high exhaust velocities. By doing so, it can achieve an Isp of thousands of seconds. To operate the engine, xenon gas is supplied into the discharge chamber where the xenon atoms are ionized by bombardment with electrons emitted from the main hollow cathode. The resulting ions are accelerated electro statically with an ion accelerating grid system to produce thrust. Magnetic rings on the walls of the discharge chamber act to contain the ions as they are accelerated. The ion accelerating system consists of two grids with many small holes. A positive voltage, usually 1000 V, is applied to the inner grid (the screen grid) and a negative voltage to the outer grid (the accelerator grid). The neutralizer emits electrons into the ion exhaust to prevent the spacecraft from acquiring an electric charge. This allows very high exhaust velocities and specific impulses. Unfortunately, the amount of thrust that an ion engine produces is very small. The engine exerts about as much force as a sheet of paper does. However, because ion engines have a high specific impulse they can thrust for very long periods and slowly build up substantial velocity.
3) CHEMICAL ROCKET:-
Gas carried by the rocket is heated by a chemical reaction and expelled to provide thrust. At least 1 trillion (1012) U.S. dollars have been spent over nine centuries on rocket research. Unfortunately, rocket launchers remain expensive and prone to failure due to temperature extremes, enormous heat flux in the throat of the thrust chamber, severe vibration, low reliability of high-performance turbo pumps, and the use of corrosive and flammable chemicals. Hot oxygen corrodes most structural materials in a matter of seconds. Refractory materials survive a few minutes. It takes extraordinary amount of research and experimentation to prevent meltdown and explosion of a newly designed rocket launcher. Most rocket launchers are expendable (disposable). The Space Shuttle is salvageable. Reusable rocket launchers do not exist. Cargo transported by rockets is called payload. The accent is on pay because it costs about $10,000 to launch 1 kilogram of cargo to a low Earth orbit. The ratio of cargo mass to the total mass of the rocket including its cargo and propellant is called payload fraction. Its value ranges from 6 percent for liquid propellant rockets to 0.2 percent for solid propellant rockets. The minimum mass of a chemical rocket launcher (for 1-ton cargo) is about 20 tons. There are eight types of chemical rockets
A) Liquid Propellant Rocket:-
It burns a mixture of liquid fuel and liquid oxidizer, e.g., hydrogen and oxygen. Commercial quantities of hydrogen are made in a process called reforming: natural gas reacts with steam, producing hydrogen and carbon dioxide. The cost of making hydrogen is about 0.7 $/kg. The cost of liquefying and transporting hydrogen from the oil refinery to the user rises its cost to about 3 $/kg. Hydrogen, like chlorine, is a destroyer of the ozone layer. The cheapest and the least toxic fuels are methane, ethane, and propane. They are stored as liquids and cost about 0.4 $/kg. Liquid oxygen is the cheapest and the least toxic oxidizer. It costs only 0.05 $/kg. 98% hydrogen peroxide (H2O2) is not as energetic as liquid oxygen and is much more expensive (20 $/kg), but it can be stored at room temperature and it is better regenerative coolant. 70% hydrogen peroxide is much cheaper (1.4 $/kg) and easier to transport because it cannot explode, even when boiling at atmospheric pressure. Diluted hydrogen peroxide can be concentrated up to 90-98% by distillation and up to 100% by crystallization. Cheap grades of hydrogen peroxide are contaminated with hydrocarbons, which make them unstable; they spontaneously break down into water and oxygen. A mixture of the cheap hydrogen peroxide and a stabilizing compound does not break down, but the stabilizing compound contaminates the catalyst beds. Surfaces that are in contact with hydrogen peroxide must be passivated to prevent decomposition of the hydrogen peroxide. Kerosene fuel and its purified form known as RP-1 (Rocket Propellant-1) can also be stored at room temperature and they go well with the hydrogen peroxide. Unlike kerosene, RP-1 has uniform density, high coking temperature, and is free of sulfur. Coking produces tarry residue at elevated temperatures. Sulfur corrodes some metals and alloys. The overall density of the peroxide/kerosene combination is 1312 kg/m^3, better than overall density of liquid oxygen/methane, which is only 828 kg/m^3. On the other hand, the liquid oxygen/methane combination has 12% higher specific impulse and these propellants can be self pressurized, which means that their vapor pressure forces them into the rocket engine. The self pressurized rocket has simpler design and lower dry weight than a rocket using conventional pressurization system made of a helium tank and a flexible bladder separating the helium and the propellant. Small rocket engines are usually pressure-fed, which means that there is no pump and the pressure in the fuel tank and the oxidizer tank is high enough to deliver the propellants to the combustion chamber. The fuel and oxidizer are mixed and burned in the combustion chamber. To speed up the mixing, high-pressure fuel jets impinge on high-pressure oxidizer jets. The jets come out of holes drilled at acute angles in the injector and impinge on each other at a distance of about 6 hole diameters. (It is easy to break the bit while drilling the tiny holes at acute angles.) A misaligned jet spilling oxygen on the combustion chamber makes a hole in the chamber in less than one minute. The outermost injector holes inject only fuel to protect the combustion chamber with a layer of cold gas. This is called "curtain cooling." The exhaust gas rich in hydrocarbon fuel deposits protective layer of soot on the inner surface of the combustion chamber. The liquid propellant rocket using one kind fuel and one kind of oxidizer is called biprop rocket. The biprop rocket has a high specific impulse (3.0-5.3 km/s) but requires expensive engine. To reduce the size and cost of the engine, turbo pumps are used to feed fuel and oxidizer at high pressure (2-40 MPa) to the combustion chamber. Turbo pumps are the most expensive and the least durable parts of the rocket engine. Furthermore, the high pressure produced by the turbo pumps necessitates the use of very efficient regenerative cooling and implies the use of weak propellant tanks which cannot survive reentry.
B) Liquid Rocket in Tube:-
It is a liquid propellant rocket which flies inside a steel tube or a tunnel. The tube is filled with hydrogen gas to reduce friction between the tube, the rocket, and its exhaust gas. Liquid propellant tanks are surrounded by hot exhaust gas under high pressure. To reduce the rate of vaporization, the tanks are lined with thermal insulation. Liquid methane fuel and liquid oxygen are pressure-fed into the combustion chamber without the aid of turbo pumps. Tank walls are thin and light-weight because pressure inside the tanks is only slightly higher than pressure outside the tanks.
C) Solid Propellant Rocket :-
Solid propellant rocket burns a solid block made of fuel, oxidizer, and binder (plastic or rubber). The block is called grain. Ammonium per chlorate oxidizer and other chlorine compounds are toxic, corrosive, and damage the ozone layer. Ammonium nitrate oxidizer is hygroscopic, but is usually more desirable, because it is safe, cheap, and smokeless. Solid propellant rocket is inexpensive, but has a low specific impulse (2-3 km/s), has to carry heavy casing, and cannot be throttled or stopped; it burns until all the grain is exhausted. When used in outer space, they may produce space junk in the form of micrometer-size aluminum oxide particles and centimeter-size slag. Mixing ingredients of the grain is dangerous because the mixing tool may scrape a solid surface and thus make a spark which ignites the grain. The liquid grain is cast into the rocket case and allowed to harden and cure. Extreme care must be taken during casting to ensure good bonding of the grain to the case wall and to avoid the formation of cracks and voids. The larger the rocket, the more susceptible it is to the formation of the cracks. A fast burning solid propellant may explode while it burns.
D) Candle Rocket :-
It is a solid propellant rocket without the heavy steel casing. The grain burns at one end like a candle rather than inside out. It slides under its own weight into the exhaust nozzle throat and burns there. Spiral grooves in the grain ensure uniform burning of the grain. The candle rocket cannot match the specific impulse of the solid propellant rocket unless it matches its combustion pressure, which is 5-10 MPa. The high pressure implies either high acceleration of the rocket, or a very tall rocket.
E) Solid Rocket in Tube:-
It is a solid propellant rocket which burns on the outside and flies inside a steel tube or a tunnel. Heavy casing of the ordinary solid propellant rocket is not needed because the tube holds the exhaust gas. The tube is filled with hydrogen gas to reduce friction between the tube, the rocket, and its exhaust gas.
F) Hybrid Rocket :-
Hybrid rocket burns a mixture of solid fuel and liquid or gaseous oxidizer, usually synthetic rubber and oxygen. The rubber is perforated to ensure thorough mixing of the fuel and oxidizer. Hybrid rocket is exceptionally safe. It almost matches the high specific impulse of liquid propellant rocket, and requires only half the number of expensive turbo pumps. Most designs forgo turbo pumps; liquid oxygen is fed into the combustion chamber by tank pressure.
G) Inverse Hybrid Rocket :-
Inverse hybrid rocket burns a mixture of solid oxidizer and liquid or gaseous fuel. It is much less popular than hybrid rocket because the liquid fuel is highly flammable.
H) Pulse Detonation Rocket :-
It periodically detonates a mixture of liquid fuel and liquid oxidizer in a straight tube that has one end closed. Because the mixture is injected into the tube at a low pressure, turbo pumps are not needed. Detonations do not bode well for the durability of this novel rocket. The specific impulse is about 10 percent higher than that of the liquid propellant rocket.
4) LASER ROCKETS:-
Modern era in rocket propulsion engineering research and developments on the way……. This paper is eye sight on this vision.
BACK GROUND ON PROPULSION:-
Propulsion is the act of pushing or driving an object forward. Often through a force called thrust machines like airplanes and rockets take advantage of Newton’s 3rd law of action and reaction to produce thrust. Thrust can be expressed with the following equation If Pe doesn't equal Po: F thrust = meve - movo + Ae (pe - po)
The subscript e denotes trait at the exit of propulsion device, and o denotes a trait prior to the entrance of propulsion device (unaffected fluid). v = velocity, p = pressure, A = area, and m = mass flow rate (mass / time or density x velocity x area).
INTRODUCTION TO LASER ROCKET PROPULSION:-
Using laser as a propellant which is placed as base (on the earth) and the only rocket will be placed on upper side of the laser. when the laser is powered on, the black plastic which placed in the rocket will be absorbing the light. And this light will help the black plastic to heat up, as a result there will be a large threshold done inside. Due to this threshold inside, makes the rocket to bloom upwards On a bad day which is called more humidity atmosphere time only most of the rockets will be sent into the space. On this type of climates clouds (air) will be absorbing more laser light than a propellant. A power intensity laser beam heats up the air and thus reduces its co-efficient of refraction. This effect is termed as blooming.
LASER PROFILES:-
Any given laser - be it a He Ne, argon ion, CO2, or other CW laser; or a pulsed laser like an Nd:YAG, Ti:Sapphire, or excimer, will have two, maybe three, power or energy ratings:
The manufacturer's power rating based on model. This is the one you find in the catalog or spec sheet and will be the minimum output produced during the warranted life of the laser under a given set of operating conditions.
o For He Ne lasers, there is a single rating since these are generally operated at their nominal tube current all the time. Example (Spectra-Physics He Ne laser model 105-1 He Ne laser): 5 mW.
o For CW lasers which have variable output power like argon ion and CO2, there will be a chart of output power for several typical sets of operating conditions (e.g., tube current). Example: See the chart in the section: Argon/Krypton Ion Laser Tube Life.
o Similarly, pulsed lasers like flash lamp pumped Nd:YAG may have a chart of output pulse energy and power as a function of input flash lamp energy. However, note that pulse-to-pulse variations of 10 percent or more are common with pulsed lasers.
The actual measured power output at the time of manufacture. This value or chart may be provided with a certification document or hand printed somewhere inside the laser or on the laser tube itself. As the laser gets older (with or without use depending on type), this value may change. Example (for the Spectra-Physics model 105-1 HeNe laser): 6.6 mW.
The CDRH sticker rating. This is the MAXIMUM power rating for the classification for this particular laser (though it may be less than the maximum permitted by the actual CDRH designation). However, a much higher value than the catalog rating doesn't mean that the laser is necessarily capable of this power level or even close to it under any conditions.
o A He Ne laser produces its maximum output power at the nominal operating current - there is no way to boost it. Example (for the Spectra-Physics model 105-1 He Ne laser): 10 mW Max, Class III b Laser Product.
Where the output power of a laser increases with increasing tube current or input energy, it is conceivable that under conditions that would not be ordinarily possible (e.g., very high tube current at the instant it starts or increased energy storage capacitance or voltage), this rating could be exceeded momentarily or continuously.
BLACK PLASTIC PROFILE:-
The following are the explanation of black plastic characteristics.
1) A process for producing carton black by the pyrolytic decomposition of hydrocarbon feedstock comprising,
A) Introducing a hydrocarbon feedstock selected from the group of liquid and gaseous hydrocarbons into a carbon black reactor.
B) combusting a normally liquid fuel having dissolved there in a normally solid polymer selected from the group consisting of polyethylene, polypropylene, polyvinyl chloride and polystyrene and mixtures there of with a gaseous oxidant selected from the group consisting of air. Oxygen enriched air, and oxygen to produce hot combustion gases,
C) Contacting the hydrocarbon feedstock in the carbon black reactor with the hot combustion gases
D) Pyrolytically decomposing said feedstock in the heat created by the combustion of step (b) such as to convert said feedstock into a carbon black-containing smoke.
E) Separating said carbon black from said smoke, and
F) Recovering said carbon black.
2) A process in accordance with claim 1 where in said normally liquid fuel is a paraffin fuel and is preheated to about 1200 to 1400, up to about 10wt percentage of said polymer is dissolved in said preheated fuel to form a preheated solution, and said preheated solution is combusted with said oxidant to form said hot combustion gases.
3) A process in accordance with claim 1 where in said normally liquid fuel is an aromatic fuel and is preheated to about 1200 to 1400, up to 40wt percentage of said polymer is dissolved in said aromatic liquid fuel to form a preheated solution and said preheated solution is combusted with said oxidant to form said hot combustion gases.
WORKING PRINCIPLES
The cargo is placed above a curve mirror, and when the laser is fired the mirror focuses the beam under the rim. This then heats up the air to around 30,000 degrees, causing the air to explore which in turn pushes the vehicle up.
10-kilowatt, pulsed carbon dioxide laser is on deck to send light craft high over the desert scenery. Light craft fly a top a beam of laser light, harnessing its energy and converting it into propulsive thrust.
V = (exhaust gas velocity) natural logarithm (total mass / dry cargo mass)
The total mass includes everything: rocket engine, structural parts, propellant, and cargo. The dry cargo mass is the mass of the rocket engine, structural parts and cargo. The ratio of total mass to dry cargo mass is called mass ratio (MR). According to the above formula, which is known as the rocket equation, a high velocity of exhaust gas is needed to launch massive cargo. Dividing the rocket launcher into several stages also helps, but it makes the staged launcher more complex than the single stage launcher.
Specific impulse describes propulsive efficiency of all contraptions, which generate thrust by consuming fuel or rocket propellant. The specific impulse is defined as impulse produced by one kilogram of fuel or propellant. Metric units of the specific impulse are Ns/kg or m/s (meter per second). The specific impulse of a rocket is the same as its exhaust gas velocity, but the specific impulse of an air-breathing engine is one order of magnitude greater. Most racketeers express the specific impulse in seconds and calculate it by dividing the exhaust gas velocity by 9.8. All values of specific impulse given in this publication pertain to rockets immersed in a vacuum.
The maximum velocity of the exhaust gas is about twice its speed of sound: U max = A0 (2 / (G-1))^0.5
Where:
A0 is the initial speed of sound of the exhaust gas
G is the ratio of specific heat at constant pressure to specific heat at constant volume
The high exhaust gas velocity calls for high pressure in the combustion chamber, high expansion ratio, and a hot gas having low molecular mass. The ratio of the exhaust nozzle exit area to the throat area is called the expansion ratio or the nozzle area ratio. To maximize the specific impulse, some researchers attempt to build rockets propelled by pure hydrogen heated either by electric current, or a laser, or microwaves, or a nuclear reactor.
PHOTONS THEORY OF LASER
This is a simple calculation based on knowing the energy of each photon (based on wavelength):
E = 1.602*10-19 J *1,240 nm/Lambda,
Where:
Lambda = wavelength of your light source.
1,240 nm = photon wavelength with an energy of 1 eV.
Then, photon flux = P/E where P is the beam power.
For example, a 1 mW, 620 nm source will produce about:
1*10-3 / 1.60210*10-19 * 2 = 3*1015 photons/second.
INTENSITY OF LASER BEAM/ INVERSVE SQUARE LAW
I’m having a real tough time with this one, may be I can get a little help.
A small helium neon laser emits red visible light with a power of 3.2mW in a beam that had a diameter of 2.5mm. What is the intensity of the laser beam? Does this intensity obey the inverse square law?
Now I have for an answer an intensity of 0.652w/m2 and that is does not obey the inverse square law.
For the intensity,
I thought: I= power / (4 pi (diameter /2)^2)
But that gives me an intensity of only 0.163. And I thought that all light obeyed the inverse square law. I’ve done research for this on the net, but I can’t fine any thing. A shove in right direction would be appreciated.
The inverse square law applies to light radiant in all directions the reduction in intensity is because the same amount of light is covering an ever expanding area. With a laser, you’re sending the light in a straight line (theoretically, at least). The light beam covers the same amount of area 10 miles from its source as it did when it first left the laser.
WORKING PRINCIPAL :
As experimentally hydrogen propellant is the highest specific impulse it will not absorb laser light well. So by using a metal heat exchanger, we can raise the hydrogen temperature to 3700K. Molecules of CO, CO2, CH4, and H2O absorb infrared light produced by carbon dioxide laser. A mixture of hydrogen and one of these chemicals can be heated by the carbon dioxide laser to 5000-6000 K. The surrounded laser beam will heat up the atmospheric air so much. By that the air become less intensity and also reduces its coefficient of refraction. Unseeded hydrogen absorbs light via inverse bremsstrahlung absorption when it is heated to 15000K. More threshold in the rocket can be done by compression of hydrogen or nitrogen with molecules of CO, CO2, CH4, and H2O.
BREMSSTRAHLUNG : Radiation emitted by a charged particle under acceleration. In particular, the term is used for radiation caused by decelerations (the word is German for braking radiation) when passing through the field of atomic nuclei (external bremsstrahlung). Radiation emitted by a charged particle moving in a magnetic field is called synchrotron radiation.
ROLE OF BLACK PLASTIC:-
The laser from the pulsed carbon dioxide will heat up the black plastic which is placed at high compressed state. Due to the heat formed from black plastic inverse thrust done and the rocket moves upward. Black plastic is made of combusting a normally liquid fuel having dissolved there in a normally solid polymer selected from the group consisting of polyethylene, polypropylene, polyvinyl chloride and polystyrene and mixtures there of with a gaseous oxidant selected from the group consisting of air, oxygen-enriched air, and oxygen to produce hot compression gas. Black plastic can heat up atmospheric air more than 5000K; the air can be nitrogen, hydrogen or carbon. Black plastic is mainly used because it is having less wait and highly compressive. Eg:-paraffin fuel is twice as stronger as conventional solid propellants. The paraffin fuel can be preheated to about 1200 to 1400, up to about 10%wt of total wt. The first test of this laser propellant done on 1996 and on 1997 a successive distance of 90 feet was flew but this light crafts can be so much heated by the laser beam. And the laser beam will be passed through central axis of light craft which can damage the cargo because of smaller rocket. Due to this problem the project got dispersed in 1999.
CALCULATION FOR THRUST AND SPECIFIC IMPULSE
Thrust is the amount of force generated by the rocket.
Specific impulse is a measure or engine performance (analogous to miles per gallon). Units are seconds
Isp = F/W
Where as
F= Rocket thrust
W= weight flow rate of propellant
Where g = 9.8m /s2
Mi = mass of vehicle before burn
Mf = mass of vehicle after burn
Mp = mass of propellant for
Mp = Mi (1-e^((-DelV)/(GIsp))
Mission (duration) ΔV(Km/Sec)
Earth surface to LEO 7.6
LEO to Earth Escape 3.2
Using permanent launching pad’s-
->reduce the cost.
->increase the performance.
Mass of pay load can be considerably reduced.
Frequency of launch and number of cargo (satellite) can be increased cost effective.
Eco –friendly.
Demolition or recovery of aged/damaged/distractive satellites.
Reflection of generated laser power for other applications.
1) NUCLEAR FISSION ROCKETS (solid core nuclear rockets):-
Solid core nuclear rockets work by taking liquid hydrogen and pumping it to the reactor through a jacket surrounding the rocket engine. This pumping process helps cool the rocket, and it also preheats the liquid hydrogen. Hundreds of narrow channels pass through the nuclear reactor. As the liquid hydrogen flows through these channels, heat from the reactor changes the fuel into rapidly expanding gas. The gas flows through the exhaust nozzle at speeds up to 35,400 kilometers per hour. A diagram of a solid core rocket. Several tests were carried out during the 1960s with nuclear rockets. The most well known of these are the Nuclear Engine for Rocket Vehicle Applications (NERVA) tests. NERVA involved the Los Alamos laboratory, Westinghouse, Aero jet, and other industrial partners. Together, they were able to build and test a solid core rocket with a thrust of 250,000 pounds, and a specific impulse (Isp) of 850 seconds, nearly twice the best Isp of chemical rockets (specific impulse is a "miles per gallon" for rockets). Research into nuclear rockets proceeds at a slow but steady pace. Most of the work is done at Los Alamos, where nuclear rockets originated. Most of the problems that the scientists are trying to solve now are how to build a nozzle and combustion chamber that can withstand the high temperatures of a gas core rocket, and how to contain the uranium plasma that forms. If viable nuclear rockets are ever developed, they would have the possibility of opening the solar system to manned space flight. A trip to Mars would easily be within our grasp.
2) ION ROCKETS:-
The ion rocket does away with the hot, fiery blast of chemical and nuclear rocket engines. Instead, it uses a small electrostatic grid to accelerate ions to very high exhaust velocities. By doing so, it can achieve an Isp of thousands of seconds. To operate the engine, xenon gas is supplied into the discharge chamber where the xenon atoms are ionized by bombardment with electrons emitted from the main hollow cathode. The resulting ions are accelerated electro statically with an ion accelerating grid system to produce thrust. Magnetic rings on the walls of the discharge chamber act to contain the ions as they are accelerated. The ion accelerating system consists of two grids with many small holes. A positive voltage, usually 1000 V, is applied to the inner grid (the screen grid) and a negative voltage to the outer grid (the accelerator grid). The neutralizer emits electrons into the ion exhaust to prevent the spacecraft from acquiring an electric charge. This allows very high exhaust velocities and specific impulses. Unfortunately, the amount of thrust that an ion engine produces is very small. The engine exerts about as much force as a sheet of paper does. However, because ion engines have a high specific impulse they can thrust for very long periods and slowly build up substantial velocity.
3) CHEMICAL ROCKET:-
Gas carried by the rocket is heated by a chemical reaction and expelled to provide thrust. At least 1 trillion (1012) U.S. dollars have been spent over nine centuries on rocket research. Unfortunately, rocket launchers remain expensive and prone to failure due to temperature extremes, enormous heat flux in the throat of the thrust chamber, severe vibration, low reliability of high-performance turbo pumps, and the use of corrosive and flammable chemicals. Hot oxygen corrodes most structural materials in a matter of seconds. Refractory materials survive a few minutes. It takes extraordinary amount of research and experimentation to prevent meltdown and explosion of a newly designed rocket launcher. Most rocket launchers are expendable (disposable). The Space Shuttle is salvageable. Reusable rocket launchers do not exist. Cargo transported by rockets is called payload. The accent is on pay because it costs about $10,000 to launch 1 kilogram of cargo to a low Earth orbit. The ratio of cargo mass to the total mass of the rocket including its cargo and propellant is called payload fraction. Its value ranges from 6 percent for liquid propellant rockets to 0.2 percent for solid propellant rockets. The minimum mass of a chemical rocket launcher (for 1-ton cargo) is about 20 tons. There are eight types of chemical rockets
A) Liquid Propellant Rocket:-
It burns a mixture of liquid fuel and liquid oxidizer, e.g., hydrogen and oxygen. Commercial quantities of hydrogen are made in a process called reforming: natural gas reacts with steam, producing hydrogen and carbon dioxide. The cost of making hydrogen is about 0.7 $/kg. The cost of liquefying and transporting hydrogen from the oil refinery to the user rises its cost to about 3 $/kg. Hydrogen, like chlorine, is a destroyer of the ozone layer. The cheapest and the least toxic fuels are methane, ethane, and propane. They are stored as liquids and cost about 0.4 $/kg. Liquid oxygen is the cheapest and the least toxic oxidizer. It costs only 0.05 $/kg. 98% hydrogen peroxide (H2O2) is not as energetic as liquid oxygen and is much more expensive (20 $/kg), but it can be stored at room temperature and it is better regenerative coolant. 70% hydrogen peroxide is much cheaper (1.4 $/kg) and easier to transport because it cannot explode, even when boiling at atmospheric pressure. Diluted hydrogen peroxide can be concentrated up to 90-98% by distillation and up to 100% by crystallization. Cheap grades of hydrogen peroxide are contaminated with hydrocarbons, which make them unstable; they spontaneously break down into water and oxygen. A mixture of the cheap hydrogen peroxide and a stabilizing compound does not break down, but the stabilizing compound contaminates the catalyst beds. Surfaces that are in contact with hydrogen peroxide must be passivated to prevent decomposition of the hydrogen peroxide. Kerosene fuel and its purified form known as RP-1 (Rocket Propellant-1) can also be stored at room temperature and they go well with the hydrogen peroxide. Unlike kerosene, RP-1 has uniform density, high coking temperature, and is free of sulfur. Coking produces tarry residue at elevated temperatures. Sulfur corrodes some metals and alloys. The overall density of the peroxide/kerosene combination is 1312 kg/m^3, better than overall density of liquid oxygen/methane, which is only 828 kg/m^3. On the other hand, the liquid oxygen/methane combination has 12% higher specific impulse and these propellants can be self pressurized, which means that their vapor pressure forces them into the rocket engine. The self pressurized rocket has simpler design and lower dry weight than a rocket using conventional pressurization system made of a helium tank and a flexible bladder separating the helium and the propellant. Small rocket engines are usually pressure-fed, which means that there is no pump and the pressure in the fuel tank and the oxidizer tank is high enough to deliver the propellants to the combustion chamber. The fuel and oxidizer are mixed and burned in the combustion chamber. To speed up the mixing, high-pressure fuel jets impinge on high-pressure oxidizer jets. The jets come out of holes drilled at acute angles in the injector and impinge on each other at a distance of about 6 hole diameters. (It is easy to break the bit while drilling the tiny holes at acute angles.) A misaligned jet spilling oxygen on the combustion chamber makes a hole in the chamber in less than one minute. The outermost injector holes inject only fuel to protect the combustion chamber with a layer of cold gas. This is called "curtain cooling." The exhaust gas rich in hydrocarbon fuel deposits protective layer of soot on the inner surface of the combustion chamber. The liquid propellant rocket using one kind fuel and one kind of oxidizer is called biprop rocket. The biprop rocket has a high specific impulse (3.0-5.3 km/s) but requires expensive engine. To reduce the size and cost of the engine, turbo pumps are used to feed fuel and oxidizer at high pressure (2-40 MPa) to the combustion chamber. Turbo pumps are the most expensive and the least durable parts of the rocket engine. Furthermore, the high pressure produced by the turbo pumps necessitates the use of very efficient regenerative cooling and implies the use of weak propellant tanks which cannot survive reentry.
B) Liquid Rocket in Tube:-
It is a liquid propellant rocket which flies inside a steel tube or a tunnel. The tube is filled with hydrogen gas to reduce friction between the tube, the rocket, and its exhaust gas. Liquid propellant tanks are surrounded by hot exhaust gas under high pressure. To reduce the rate of vaporization, the tanks are lined with thermal insulation. Liquid methane fuel and liquid oxygen are pressure-fed into the combustion chamber without the aid of turbo pumps. Tank walls are thin and light-weight because pressure inside the tanks is only slightly higher than pressure outside the tanks.
C) Solid Propellant Rocket :-
Solid propellant rocket burns a solid block made of fuel, oxidizer, and binder (plastic or rubber). The block is called grain. Ammonium per chlorate oxidizer and other chlorine compounds are toxic, corrosive, and damage the ozone layer. Ammonium nitrate oxidizer is hygroscopic, but is usually more desirable, because it is safe, cheap, and smokeless. Solid propellant rocket is inexpensive, but has a low specific impulse (2-3 km/s), has to carry heavy casing, and cannot be throttled or stopped; it burns until all the grain is exhausted. When used in outer space, they may produce space junk in the form of micrometer-size aluminum oxide particles and centimeter-size slag. Mixing ingredients of the grain is dangerous because the mixing tool may scrape a solid surface and thus make a spark which ignites the grain. The liquid grain is cast into the rocket case and allowed to harden and cure. Extreme care must be taken during casting to ensure good bonding of the grain to the case wall and to avoid the formation of cracks and voids. The larger the rocket, the more susceptible it is to the formation of the cracks. A fast burning solid propellant may explode while it burns.
D) Candle Rocket :-
It is a solid propellant rocket without the heavy steel casing. The grain burns at one end like a candle rather than inside out. It slides under its own weight into the exhaust nozzle throat and burns there. Spiral grooves in the grain ensure uniform burning of the grain. The candle rocket cannot match the specific impulse of the solid propellant rocket unless it matches its combustion pressure, which is 5-10 MPa. The high pressure implies either high acceleration of the rocket, or a very tall rocket.
E) Solid Rocket in Tube:-
It is a solid propellant rocket which burns on the outside and flies inside a steel tube or a tunnel. Heavy casing of the ordinary solid propellant rocket is not needed because the tube holds the exhaust gas. The tube is filled with hydrogen gas to reduce friction between the tube, the rocket, and its exhaust gas.
F) Hybrid Rocket :-
Hybrid rocket burns a mixture of solid fuel and liquid or gaseous oxidizer, usually synthetic rubber and oxygen. The rubber is perforated to ensure thorough mixing of the fuel and oxidizer. Hybrid rocket is exceptionally safe. It almost matches the high specific impulse of liquid propellant rocket, and requires only half the number of expensive turbo pumps. Most designs forgo turbo pumps; liquid oxygen is fed into the combustion chamber by tank pressure.
G) Inverse Hybrid Rocket :-
Inverse hybrid rocket burns a mixture of solid oxidizer and liquid or gaseous fuel. It is much less popular than hybrid rocket because the liquid fuel is highly flammable.
H) Pulse Detonation Rocket :-
It periodically detonates a mixture of liquid fuel and liquid oxidizer in a straight tube that has one end closed. Because the mixture is injected into the tube at a low pressure, turbo pumps are not needed. Detonations do not bode well for the durability of this novel rocket. The specific impulse is about 10 percent higher than that of the liquid propellant rocket.
4) LASER ROCKETS:-
Modern era in rocket propulsion engineering research and developments on the way……. This paper is eye sight on this vision.
BACK GROUND ON PROPULSION:-
Propulsion is the act of pushing or driving an object forward. Often through a force called thrust machines like airplanes and rockets take advantage of Newton’s 3rd law of action and reaction to produce thrust. Thrust can be expressed with the following equation If Pe doesn't equal Po: F thrust = meve - movo + Ae (pe - po)
The subscript e denotes trait at the exit of propulsion device, and o denotes a trait prior to the entrance of propulsion device (unaffected fluid). v = velocity, p = pressure, A = area, and m = mass flow rate (mass / time or density x velocity x area).
INTRODUCTION TO LASER ROCKET PROPULSION:-
Using laser as a propellant which is placed as base (on the earth) and the only rocket will be placed on upper side of the laser. when the laser is powered on, the black plastic which placed in the rocket will be absorbing the light. And this light will help the black plastic to heat up, as a result there will be a large threshold done inside. Due to this threshold inside, makes the rocket to bloom upwards On a bad day which is called more humidity atmosphere time only most of the rockets will be sent into the space. On this type of climates clouds (air) will be absorbing more laser light than a propellant. A power intensity laser beam heats up the air and thus reduces its co-efficient of refraction. This effect is termed as blooming.
LASER PROFILES:-
Any given laser - be it a He Ne, argon ion, CO2, or other CW laser; or a pulsed laser like an Nd:YAG, Ti:Sapphire, or excimer, will have two, maybe three, power or energy ratings:
The manufacturer's power rating based on model. This is the one you find in the catalog or spec sheet and will be the minimum output produced during the warranted life of the laser under a given set of operating conditions.
o For He Ne lasers, there is a single rating since these are generally operated at their nominal tube current all the time. Example (Spectra-Physics He Ne laser model 105-1 He Ne laser): 5 mW.
o For CW lasers which have variable output power like argon ion and CO2, there will be a chart of output power for several typical sets of operating conditions (e.g., tube current). Example: See the chart in the section: Argon/Krypton Ion Laser Tube Life.
o Similarly, pulsed lasers like flash lamp pumped Nd:YAG may have a chart of output pulse energy and power as a function of input flash lamp energy. However, note that pulse-to-pulse variations of 10 percent or more are common with pulsed lasers.
The actual measured power output at the time of manufacture. This value or chart may be provided with a certification document or hand printed somewhere inside the laser or on the laser tube itself. As the laser gets older (with or without use depending on type), this value may change. Example (for the Spectra-Physics model 105-1 HeNe laser): 6.6 mW.
The CDRH sticker rating. This is the MAXIMUM power rating for the classification for this particular laser (though it may be less than the maximum permitted by the actual CDRH designation). However, a much higher value than the catalog rating doesn't mean that the laser is necessarily capable of this power level or even close to it under any conditions.
o A He Ne laser produces its maximum output power at the nominal operating current - there is no way to boost it. Example (for the Spectra-Physics model 105-1 He Ne laser): 10 mW Max, Class III b Laser Product.
Where the output power of a laser increases with increasing tube current or input energy, it is conceivable that under conditions that would not be ordinarily possible (e.g., very high tube current at the instant it starts or increased energy storage capacitance or voltage), this rating could be exceeded momentarily or continuously.
BLACK PLASTIC PROFILE:-
The following are the explanation of black plastic characteristics.
1) A process for producing carton black by the pyrolytic decomposition of hydrocarbon feedstock comprising,
A) Introducing a hydrocarbon feedstock selected from the group of liquid and gaseous hydrocarbons into a carbon black reactor.
B) combusting a normally liquid fuel having dissolved there in a normally solid polymer selected from the group consisting of polyethylene, polypropylene, polyvinyl chloride and polystyrene and mixtures there of with a gaseous oxidant selected from the group consisting of air. Oxygen enriched air, and oxygen to produce hot combustion gases,
C) Contacting the hydrocarbon feedstock in the carbon black reactor with the hot combustion gases
D) Pyrolytically decomposing said feedstock in the heat created by the combustion of step (b) such as to convert said feedstock into a carbon black-containing smoke.
E) Separating said carbon black from said smoke, and
F) Recovering said carbon black.
2) A process in accordance with claim 1 where in said normally liquid fuel is a paraffin fuel and is preheated to about 1200 to 1400, up to about 10wt percentage of said polymer is dissolved in said preheated fuel to form a preheated solution, and said preheated solution is combusted with said oxidant to form said hot combustion gases.
3) A process in accordance with claim 1 where in said normally liquid fuel is an aromatic fuel and is preheated to about 1200 to 1400, up to 40wt percentage of said polymer is dissolved in said aromatic liquid fuel to form a preheated solution and said preheated solution is combusted with said oxidant to form said hot combustion gases.
WORKING PRINCIPLES
The cargo is placed above a curve mirror, and when the laser is fired the mirror focuses the beam under the rim. This then heats up the air to around 30,000 degrees, causing the air to explore which in turn pushes the vehicle up.
10-kilowatt, pulsed carbon dioxide laser is on deck to send light craft high over the desert scenery. Light craft fly a top a beam of laser light, harnessing its energy and converting it into propulsive thrust.
V = (exhaust gas velocity) natural logarithm (total mass / dry cargo mass)
The total mass includes everything: rocket engine, structural parts, propellant, and cargo. The dry cargo mass is the mass of the rocket engine, structural parts and cargo. The ratio of total mass to dry cargo mass is called mass ratio (MR). According to the above formula, which is known as the rocket equation, a high velocity of exhaust gas is needed to launch massive cargo. Dividing the rocket launcher into several stages also helps, but it makes the staged launcher more complex than the single stage launcher.
Specific impulse describes propulsive efficiency of all contraptions, which generate thrust by consuming fuel or rocket propellant. The specific impulse is defined as impulse produced by one kilogram of fuel or propellant. Metric units of the specific impulse are Ns/kg or m/s (meter per second). The specific impulse of a rocket is the same as its exhaust gas velocity, but the specific impulse of an air-breathing engine is one order of magnitude greater. Most racketeers express the specific impulse in seconds and calculate it by dividing the exhaust gas velocity by 9.8. All values of specific impulse given in this publication pertain to rockets immersed in a vacuum.
The maximum velocity of the exhaust gas is about twice its speed of sound: U max = A0 (2 / (G-1))^0.5
Where:
A0 is the initial speed of sound of the exhaust gas
G is the ratio of specific heat at constant pressure to specific heat at constant volume
The high exhaust gas velocity calls for high pressure in the combustion chamber, high expansion ratio, and a hot gas having low molecular mass. The ratio of the exhaust nozzle exit area to the throat area is called the expansion ratio or the nozzle area ratio. To maximize the specific impulse, some researchers attempt to build rockets propelled by pure hydrogen heated either by electric current, or a laser, or microwaves, or a nuclear reactor.
PHOTONS THEORY OF LASER
This is a simple calculation based on knowing the energy of each photon (based on wavelength):
E = 1.602*10-19 J *1,240 nm/Lambda,
Where:
Lambda = wavelength of your light source.
1,240 nm = photon wavelength with an energy of 1 eV.
Then, photon flux = P/E where P is the beam power.
For example, a 1 mW, 620 nm source will produce about:
1*10-3 / 1.60210*10-19 * 2 = 3*1015 photons/second.
INTENSITY OF LASER BEAM/ INVERSVE SQUARE LAW
I’m having a real tough time with this one, may be I can get a little help.
A small helium neon laser emits red visible light with a power of 3.2mW in a beam that had a diameter of 2.5mm. What is the intensity of the laser beam? Does this intensity obey the inverse square law?
Now I have for an answer an intensity of 0.652w/m2 and that is does not obey the inverse square law.
For the intensity,
I thought: I= power / (4 pi (diameter /2)^2)
But that gives me an intensity of only 0.163. And I thought that all light obeyed the inverse square law. I’ve done research for this on the net, but I can’t fine any thing. A shove in right direction would be appreciated.
The inverse square law applies to light radiant in all directions the reduction in intensity is because the same amount of light is covering an ever expanding area. With a laser, you’re sending the light in a straight line (theoretically, at least). The light beam covers the same amount of area 10 miles from its source as it did when it first left the laser.
WORKING PRINCIPAL :
As experimentally hydrogen propellant is the highest specific impulse it will not absorb laser light well. So by using a metal heat exchanger, we can raise the hydrogen temperature to 3700K. Molecules of CO, CO2, CH4, and H2O absorb infrared light produced by carbon dioxide laser. A mixture of hydrogen and one of these chemicals can be heated by the carbon dioxide laser to 5000-6000 K. The surrounded laser beam will heat up the atmospheric air so much. By that the air become less intensity and also reduces its coefficient of refraction. Unseeded hydrogen absorbs light via inverse bremsstrahlung absorption when it is heated to 15000K. More threshold in the rocket can be done by compression of hydrogen or nitrogen with molecules of CO, CO2, CH4, and H2O.
BREMSSTRAHLUNG : Radiation emitted by a charged particle under acceleration. In particular, the term is used for radiation caused by decelerations (the word is German for braking radiation) when passing through the field of atomic nuclei (external bremsstrahlung). Radiation emitted by a charged particle moving in a magnetic field is called synchrotron radiation.
ROLE OF BLACK PLASTIC:-
The laser from the pulsed carbon dioxide will heat up the black plastic which is placed at high compressed state. Due to the heat formed from black plastic inverse thrust done and the rocket moves upward. Black plastic is made of combusting a normally liquid fuel having dissolved there in a normally solid polymer selected from the group consisting of polyethylene, polypropylene, polyvinyl chloride and polystyrene and mixtures there of with a gaseous oxidant selected from the group consisting of air, oxygen-enriched air, and oxygen to produce hot compression gas. Black plastic can heat up atmospheric air more than 5000K; the air can be nitrogen, hydrogen or carbon. Black plastic is mainly used because it is having less wait and highly compressive. Eg:-paraffin fuel is twice as stronger as conventional solid propellants. The paraffin fuel can be preheated to about 1200 to 1400, up to about 10%wt of total wt. The first test of this laser propellant done on 1996 and on 1997 a successive distance of 90 feet was flew but this light crafts can be so much heated by the laser beam. And the laser beam will be passed through central axis of light craft which can damage the cargo because of smaller rocket. Due to this problem the project got dispersed in 1999.
CALCULATION FOR THRUST AND SPECIFIC IMPULSE
Thrust is the amount of force generated by the rocket.
Specific impulse is a measure or engine performance (analogous to miles per gallon). Units are seconds
Isp = F/W
Where as
F= Rocket thrust
W= weight flow rate of propellant
Rocket Equation:-
DelV =GIspInMi/MfWhere g = 9.8m /s2
Mi = mass of vehicle before burn
Mf = mass of vehicle after burn
Mp = mass of propellant for
ΔV
=Mi - MfMp = Mi (1-e^((-DelV)/(GIsp))
MISSION ΔV REQUIREMENT
Mission (duration) ΔV(Km/Sec)
Earth surface to LEO 7.6
LEO to Earth Escape 3.2
The commonly accepted definition for LEO is between 160 Km(99mi) and 2,000Km(1,200mi) above the Earth's Surface
ADVANTAGES AND VISION
Generation of power- through nuclear fusion.Using permanent launching pad’s-
->reduce the cost.
->increase the performance.
Mass of pay load can be considerably reduced.
Frequency of launch and number of cargo (satellite) can be increased cost effective.
Eco –friendly.
Demolition or recovery of aged/damaged/distractive satellites.
Reflection of generated laser power for other applications.
CONCLUSION
Idea of laser technology in rocket propulsion engineering is a dream, which will be reality in near future. This will be a better footage in space and defense missions. Laser technology will reduce the cost and error. No doubt laser technology will be the future in rocket propulsion engineering
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