Seminar ReportCONTENTS: 1. INTRODUCTION 2. HISTORY OF THE SCRAMJET 3. THEORY 4. ABOUT THE ENGINE 5. OPERATIONS 6. ABOUT THE FUEL USED 7. APPLICATIONS 8. HYPERSONIC SCRAMJET VEHICLES 9. RECENT PROGRESS 10. CONCLUSION www.seminarstopics.com SCRAMJET Seminar Report SCRAMJET THE SCRAMJET ENGINE INTRODUCTION One thing has always been true about rockets: The farther and faster you want to go, the bigger you rocket needs to be. Why? Rockets combine a liquid fuel with liquid oxygen to create thrust. Take away the need for liquid oxygen and your spacecraft can be smaller or carry more pay load. That's the idea behind a different propulsion system called "scramjet," or Supersonic Combustion Ramjet The oxygen needed by the engine to combust is taken from the atmospheric air passing through the vehicle, instead of from a tank onboard Its mechanically simple as it has no moving parts. All this makes the craft smaller, lighter, faster and have more room to carry payload. www.seminarstopics.com and rocket-powered aircraft. the Concorde and Tupolev Tu-144 operated at a financial loss (with the possible exception of British Airways that never opened the accounts).seminarstopics. generally in the range of Mach 1 to Mach 2. and by the early 1960s. and Russia have also progressed in hypersonic propulsion research. aircraft top speeds have remained level. Presently. Because supersonic flight requires significant amounts of fuel.Seminar Report SCRAMJET HISTORY OF SCRAMJET During and after World War II. and low-level investigations have continued over the past few decades. www. however. In the realm of civilian air transport. tremendous amounts of time and effort were put into researching high-speed jet. airlines have favored subsonic jumbo jets rather than supersonic transports. the primary goal has been reducing operating cost. Except for specialized rocket research vehicles like the American X-15 and other rocket-powered spacecraft. Other nations such as Australia. Military aircraft design focused on maneuverability and stealth. The production supersonic airliners. the US military and NASA have formulated a "National Hypersonics Strategy" to investigate a range of options for hypersonic flight. Hypersonic flight concepts haven't gone away. France. rapid progress towards faster aircraft suggested that operational aircraft would be flying at "hypersonic" speeds within a few years.com . features thought to be incompatible with hypersonic aerodynamics. The Bell X-l attained supersonic flight in 1947. rather than increasing flight speeds. Seminar Report SCRAMJET Different U. organizations have accepted hypersonic flight as a common goal. NASA believes hypersonics could help develop economical.seminarstopics.S.S. The U. Army desires hypersonic missiles that can attack mobile missile launchers quickly. reusable launch vehicles. www.com . Currently research and development is going on for a craft that can break the Mach 10 barrier. the airflow in a pure scramjet remains supersonic throughout the combustion process and does not require a choking mechanism. Australia reported in 1995 the first development of a scramjet that achieved more thrust than drag[l] and in 2002 successfully tested the HyShot Scramjet system." The University of Queensland. Modern scramjet engines can function as both a ramjet and scramjet and seamlessly make the transition between the two. www. to supersonic speeds.Seminar Report SCRAMJET The Air Force is interested in a wide range of hypersonic systems. the mixture combusts. from air-launched cruise missiles to orbital spaceplanes. and exhaust gases accelerate through a narrow throat. THEORY What is a scramjet? In a conventional ramjet. which provides optimal performance over a wider operating range of Mach numbers. Fuel is added to the subsonic airflow. By contrast. the incoming supersonic airflow is slowed to subsonic speeds by multiple shock waves. created by back-pressuring the engine. or mechanical choke. that the service believes could bring about a true "aerospace force.com . And the most recent successful tests were achieved by NASA's Hyper-X project in 2004 (around Mach 10).seminarstopics. Mach number: Mach number is a quantity that defines how quickly a vehicle travels with respect to the speed of sound. The Mach number (M) is simply the ratio of the vehicle's velocity (V) divided by the speed of sound at that altitude (a). the air molecules near the aircraft are disturbed and move around the aircraft. an aircraft flying at Mach 0. Scientists have devised a standard atmosphere model that defines typical values for the speed of sound that change with altitude. a late 19th century physicist who studied gas dynamics.seminarstopics. Exactly how the air re-acts to the aircraft depends upon the ratio of the speed of the aircraft to the speed of sound through the air. Because of the importance of this speed ratio.com . the flight Mach number is nearly equal to 1. of sound (M<1) is said to be flying at subsonic speeds. M transonic: As the speed of the object approaches the = speed of sound. Different speed regions: on subsonic: A vehicle that is traveling slower than the speed e. such as air. Basic Definitions: speed of sound: The speed of sound is a basic property of the atmosphere that changes with temperature. For example. aerodynamicists have designated it with a special parameter called the Mach number in honor of Ernst Mach. For a given set of conditions. the speed of sound defines the velocity t which sound waves travel through a substance. www.8 is traveling at 80% of the speed of sound while a missile cruising at Mach 3 is traveling at three times the speed of sound.Seminar Report SCRAMJET About MACH Number and Speed of Sound As an aircraft moves through the air. seminarstopics. M > 5. the flow is said to be hypersonic. www. "breaking the sound barrier" is the process of accelerating through Mach 1 and going from subsonic to supersonic speeds.com .Seminar Report SCRAMJET and the flow is said to be transonic. supersonic: A vehicle that is traveling faster than the speed of sound (M>1) is said to be flying at supersonic speeds. In particular. hypersonic: For speeds greater than five times the speed of sound. sound barrier: The term sound barrier is often associated with supersonic flight. When the combustion process begins to separate the boundary layer. Unlike jet engines. The engine occupies the entire lower surface of the vehicle body. and aftbody. The air undergoes a reduction in Mach number and an increase in pressure and temperature as it passes through shock waves at the forebody and internal inlet.About the Engine The scramjet provides the most integrated engine-vehicle design for aircraft and missiles. It allows a supersonic flow to adjust to a static back-pressure higher than the inlet static pressure. The high-speed air-induction system consists of the vehicle forebody and internal inlet. which optimizes engine thrust. in which shock waves prevent airflow from entering the isolator. The propulsion system consists of five major engine and two vehicle components: the internal inlet. The forebody provides the initial compression. and fuel supply subsystem. internal nozzle. isolator. The combustor accepts the airflow and provides efficient fuel-air mixing at several points along its length. vehicles flying at high supersonic or hypersonic speeds can achieve adequate compression without a mechanical compressor. and the internal inlet provides the final compression. The isolator in a scramjet is a critical component. The isolator also enables the combustor to achieve the required heat release and handle the induced rise in combustor pressure without creating a condition called inlet unstart. a precombustion shock forms in the isolator. essential for air induction. and the craft's forebody. which is a critical part of the nozzle component. combustor. . which capture and compress air for processing by the engine's other components. Thus the heat released from combustion at Mach 25 is around 10% of the total enthalpy of the working fluid. Thus the design of a scramjet engine is as much about minimising drag as maximising thrust. boundarylayer effects. Changing from subsonic to supersonic combustion. consisting of the internal nozzle and vehicle aftbody. Depending on the fuel. . the kinetic energy of the freestream air entering the scramjet engine is large compared to the energy released by the reaction of the oxygen content of the air with a fuel (say hydrogen). nonuniform flow conditions. because it influences the craft's pitch and lift. The important physical phenomena in the scramjet nozzle include flow chemistry. the kinetic energy of the air and the potential combustion heat release will be equal at around Mach 8. controls the expansion of the highpressure. shear-layer interaction. and three-dimensional effects. The expansion process converts the potential energy generated by the combustor to kinetic energy. high-temperature gas mixture to produce net thrust. The design of the nozzle has a major effect on the efficiency of the engine and the vehicle.The expansion system. At arou . Here. and heat release. or the use of rockets. the use of supersonic combustion can provide higher performance . Engine efficiency dictates using the ramjet until Mach 5-6. The vehicle may utilize one of several propulsion systems to accelerate from takeoff to Mach 3. a weaker precombustion system is required. a scramjet transitions from low-speed propulsion to a situation in which the shock system has sufficient strength to create a region(s) of subsonic flow at the entrance to the combustor. This choke is created by the right combination of area distribution. In a conventional ramjet. which ensures complete combustion at subsonic speeds. At Mach 3-4.diverging nozzle behind the combustor creates a physical throat and generates the desired engine thrust. During the time a scramjet-powered vehicle accelerates from Mach 3 to 8. is provided within the combustor by means of a thermal throat. Two examples are a bank of gas-turbine engines in the vehicle.Operations An air-breathing hypersonic vehicle requires several types of engine operations to reach scramjet speeds. and the precombustion shock is pulled back from the inlet throat toward the entrance to the combustor. however. As speeds increase beyond Mach 5. The required choking in a scramjet. Consequently. either internal or external to the engine. the airbreathing propulsion system undergoes a transition between Mach 5 and 7. The total rise in temperature and pressure across the combustor begins to decrease. A converging. fuel-air mixing. the inlet and diffuser decelerate the air to low subsonic speeds by increasing the diffuser area. which needs no physical narrowing of the nozzle. a mixture of ramjet and scramjet combustion occurs. management of engine heat loads. which creates high ps. decelerating airflow to subsonic speeds for combustion pum results in parts of the airflow almost halting. When the vehicle accelerates beyond Mach 7.nd Mach 6. well Scramjet operation at Mach 5-15 presents several technical as problems to achieving efficiency. the high temperatures in the man combustor cause dissociation and ionization. and thermal sche management of the combustor. These factors— age coupled with already-complex flow phenomena such as supersonic men mixing. withstand hypersonic flight. increased heating on bust leading edges. including heating of the vehicle skin from subsystems such as s on . and the and engine operates in scramjet mode without a precombustion shock. physics dictates supersonic combustion because the engine cannot ics. These challenges include fuel-air com mixing. and developing structures and materials that can ion. survive the pressure and heat buildup caused by slowing the airflow as to subsonic speeds. and flame propagation— t pose obstacles to flow-path design. the combination of these factors indicates a switch to scramjet auli operation. isolator. Somewhere between Mach 5 and hydr 6.combustor interactions. which rma occurs at about Mach 12. fuel injection. combustion process can no longer separate the airflow. elec The inlet shocks propagate through the entire engine. When the velocity of the injected fuel The equals that of the airstream entering the scramjet combustor. mixing the air and fuel becomes difficult. Beyond Mach tron 8. mes Several sources contribute to engine heating during hypersonic focu flight. pressures and heat-transfer rates. l- And at higher Mach numbers. the cs. the engine in hypersonic vehicles because of its potential for extremely high heat loads. . vibration. fluctuating and thermally-induced pressures Erosion from airflow over the vehicle and through the engine . high-temperature materials and structural configurations that can withstand the extreme environment of hypersonic flight. temperatures in the combustor would exceed 5. mechanical.000 °F. The challenges include: Very high temperatures Heating of the whole vehicle Steady-state and transient localized heating from shock waves High aerodynamic loads High fluctuating pressure loads The potential for severe flutter. as well as a corrosive mix of hot oxygen and combustion products. Fortunately. If the engine is left uncooled. Hypersonic vehicles also pose an extraordinary challenge for structures and materials. The airframe and engine require lightweight. a combination of structural design. and acoustic loading. material selection. which is higher than the melting point of most metals.The engine represents a particularly challenging problem because the flow path is characterized by very high thermal. and active cooling can manage the high temperatures. One way to illustrate the differences between various fuels and their energy content is a measurement called the Lower Heating Value (LHV). the scramjet is significantly different from other kinds of jet engines. researchers must choose a fuel that can burn rapidly and generate a large amount of thrust. However. less than half that of hydrogen. The LHV for hydrogen is 119. . This process typically occurs in less than 1 millisecond (0. Furthermore. In order to make a scramjet work. meaning that it gets its oxygen from the surrounding air.600 kJ/kg. in one key way. The LHV describes the amount of energy released when a fuel is combusted and all of the remaining combustion products remain in gaseous form. remains supersonic. like turbojets and ramjets. The challenge of making a scramjet work is properly mixing the high-speed air with fuel while combusting and expanding that mixture before it exits the tail of the vehicle. however. has a LHV of only 43. the scramjet must burn enough fuel to generate an enormous amount of energy needed to overcome the tremendous drag forces experienced when flying at hypersonic speeds. Hydrogen meets these criteria. JP-8. the air pulled into the engines is slowed below Mach 1 and is combusted at subsonic speeds. The air within the scramjet combustion chamber.190 kJ/kg. another fuel commonly used in military aircraft. In most jets. or any other hydrocarbon fuel for that matter.About the Fuel used The scramjet is an airbreather.001 seconds). Simply put. hydrogen provides more "bang" per kilogram than JP-8. 09 kg/m3. Hydrogen is not a dense fuel.950 kPa) it will contain only a quarter of the chemical energy stored in an equivalent volume of JP-8. In addition. the cost and safety issues involved in manufacturing and storing cryogenically-cooled fuel is another major drawback. more energy can often be stored in . Compare that to the density of gasoline at 750 kg/m3 or JP-8 at 800 kg/m3. The density of hydrogen can be further increased by cooling and pressurizing the substance to the point that it becomes a liquid. Hydrogen also has a wide flammability range. At standard pressure and temperature. Since hydrogen is a gas. it mixes very easily with air allowing for very efficient combustion. there are some disadvantages to using hydrogen as a fuel in aerospace vehicles. but even in this form it will need a tank approximately twice the size of that required by JP-8. First of all.There are also other advantages to using hydrogen as a fuel. hydrogen is extremely flammable. it has a density of only 0. carbon dioxide (C02). it only takes a small amount of energy to ignite it and make it burn. While this low density is an advantage in terms of saving weight. meaning that it can burn when it occupies anywhere from 4% to 74% of the air by volume. or particulate matter during the combustion process. Nevertheless. It is for this reason alone that many researchers have promoted hydrogen as a fuel in the public transportation industry. hydrogen requires a large volume in order to store an adequate amount of chemical energy for practical use. Hydrogen gas is typically stored under pressure to increase its density. Another advantage over hydrocarbon-based fuels like JP-8 or gasoline is that hydrogen does not produce any harmful pollutants like carbon monoxide (CO).000 psi (68. but even at 10. Despite the clear advantages of hydrogen described earlier. . As a result. vehicles burning denser hydrocarbon fuels can usually fly longer distances than those using hydrogen.smaller volumes using denser fuels. APPLICATIONS Seeing its clear potential. but scramjets would take much longer to get to orbit which offsets the advantage. and there are obvious issues with sonic booms and acceptable g-loads on passengers. Whether this vehicle would be reusable or not is still a subject of debate and research. An aircraft using this type of jet engine could dramatically reduce the time it takes to travel from one place to another. since that application requires only cruise operation instead of net thrust production. . potentially permitting much cheaper access to space. potentially putting any place on Earth within a 90 minute flight. One issue is that scramjets are predicted to have exceptionally poor thrust to weight ratio. organizations around the world are researching scramjet technology. This is compensated for in scramjets partly because the weight of the vehicle would be carried by aerodynamic lift rather than pure rocket power (giving reduced 'gravity losses'). there are questions about whether such a vehicle could carry enough fuel to make useful length trips. Space launch vehicles may benefit from having a scramjet stage. Much of the money for the current research comes from governmental defence research contracts. Scramjets will likely propel missiles first. This compares unfavourably with a typical rocket engine that is usually 50-100. A scramjet stage of a launch vehicle theoretically provides a specific impulse with 1000 to 4000 s whereas a rocket provides less than 600 s whilst in the atmosphere [1].around 2 . However. air-breathing ramjet or scramjet engines would power the aircraft to hypersonic velocities (Mach 20 or more) and to the edge of the atmosphere. A small rocket system would provide the final push into orbit. The X-30 was intended to replace the Space Shuttle but was cancelled in the early 1990s due to escalating costs and lack of military support. Once the aircraft had reached sufficient speed. but data collected from these test flights will be used to develop practical hypersonic scramjet engines for future vehicles. unpiloted vehicle intended to test an integrated scramjet engine from Mach 7 to 10. which used an integrated scramjet propulsion system. To become airborne. but the attractiveness of the concept was using the atmosphere to provide most of the fuel needed to get into space. The proposed National Aerospace Plane (NASP) would take off from a standard runway using some kind of low speed jet engine.Hypersonic SCRAMJET vehicle applications National Aerospace Plane (NASP) and X-30: During the 1980s. The Hyper-X will only fly for a few seconds before falling into the ocean. The Pegasus will power the test craft to about 100. the Hyper-X is a small. . NASP eventually matured into the X-30 research vehicle.Looking much like a scaled-down X-30. now known as the X-43 will be the first vehicle using an air-breathing engine ever flight tested at hypersonic speeds. X-43 Hyper-X: NASA's Hyper-X project. the X-43 will be mounted on the nose of a Pegasus rocket carried aloft and released by a B-52. NASA began considering a hypersonic single-stage-to-orbit (SSTO) vehicle to replace the Space Shuttle.000 ft and the desired test speed before the X-43 separates and its scramjet engine engages. The RBCC engine is a new technology using a rocket engine fed by oxygen from the atmosphere rather than carried aboard the vehicle. an evolved version of the original X-43 A. The upgraded engine would provide 10 seconds of power and be capable of . Regardless of the engine eventually selected. The RTA engine would accerate to about Mach 5 where a HyTech engine like that used on the X-43C would take over. In addition. an alternative propulsion arrangement is being developed at NASA Glenn as part of the Revolutionary Turbine Accelerator (RTA) program. Both the RBCC and TBCC vehicles would be able to glide down for landing and reuse permitting up to 25 flights. Boeing.8 and accelerate to Mach 7 or 8 over 10 minutes. liquid-hydrogen-fueled scramjet. A final proposal is for an X-43D. and Rocketdyne.The first X-43 test flight. The RTA engine uses a turbine-based combined cycle (TBCC) to push turbojet technology to much higher speeds than is possible with current jet engines. The effort is being funded by NASA Marshall under the Integrated Systems Test of an Airbreathing Rocket (ISTAR) program. ended in failure after the Pegasus booster rocket became unstable and went out of control. conducted in June 2001. Two propulsion concepts are currently being considered for an X-43B model. three follow-on models are also being considered. First of these is the X-43C which will test a hydrocarbon-fueled dual mode scramjet being developed by Pratt & Whitney under the Air Force's HyTech program. Meanwhile. plans call for the vehicle to be air-launched at Mach 0. the X-43D would use a cooled. First of these is a rocket-based combined cycle (RBCC) engine under development by Aerojet. Pratt & Whitney. While the X-43 A is powered by an uncooled hydrogen-fueled scramjet engine. The HyTech engine is expected to accelerate the enlarged X-43C from Mach 5 to Mach 7. .accelerating to Mach 15. Although the trend soon fizzled and military planners looked to maneuverability and stealth for survival. many have conjectured about the existence of a Mach 5 spy plane. Trends of the 1950s and 1960s indicated that military aircraft had to fly faster and higher to survive. Military Applications: Probably the greatest proponent of hypersonic travel over the years has been the United States military.Commercial Transports: Hypersonic vehicles in general and waveriders in particular have long been touted as potential high-speed commercial transports to replace the Concorde. Most current concepts for high-speed missiles are simple cylinders with no relation to waveriders. the military has recently shown renewed interest in hypersonic flight. If so. militaries around the world will likely have hypersonic cruise missiles entering service by 2015. Some aerospace companies. so concepts for high-altitude fighters and bombers cruising at Mach 4 or more were not uncommon. the Aurora. Northrop Grumman has unveiled a concept for a hypersonic bomber designed using waverider principles. and government officials have proposed vehicles cruising at Mach 7 to 12 capable of carrying passengers from New York to Tokyo in under two hours. airlines. . Cruise Missiles: Though developing a man-rated hypersonic vehicle like those described above will likely require decades of work and enormous cost. For example. that may be under development or perhaps already flying. the Aurora may be a scramjet-powered design similar to the X-30 and X-43 research vehicles.More recently. As for the X-43A Hyper-X. the first to demonstrate a scramjet working in an atmospheric test was a shoestring project by an Australian team at the University of Queensland. Aerojet. While American efforts are probably the best funded. and Rocketdyne to join forces for development. Microcraft. and Glenn Centers are now all heavily engaged in hypersonic propulsion studies. . and the General Applied Science Laboratory (GASL) on the project. the engine was not designed to provide thrust to propel a craft. NASA's Marshall Space Propulsion Center has introduced an Integrated Systems Test of an Air-Breathing Rocket (ISTAR) program. The most advanced US hypersonics program is the US$250 million NASA Langley Hyper-X X-43A effort. Marshall. which has now been demonstrated in a wind-tunnel environment. The university's HyShot project demonstrated scramjet combustion in 2002. significant progress has been made in the development of hypersonic technology. This demonstration was somewhat limited. particularly in the field of scramjet engines. prompting Pratt & Whitney. which flew small test vehicles to demonstrate hydrogen-fueled scramjet engines. however. three follow-on projects are now under consideration. while the scramjet engine worked effectively and demonstrated supersonic combustion in action. The NASA Langley. The US Air Force and Pratt and Whitney have cooperated on the Hypersonic Technology (HyTECH) scramjet engine. NASA is worked with contractors Boeing.RECENT PROGRESS In recent years. The Glenn Center is taking leadership on a Mach 4 turbine engine of interest to the USAF. .CONCLUSION Imagine a jet engine that doesn't pollute the atmosphere. flies more than five times the speed of sound and carry more pay load. It will take years of work before scramjets are available for practical uses. This can be made into reality using Scramjet Engines that is powered by oxygen it scoops out of the air as it flies. Therfore Scramjets are truly the future of flight. but they could eventually revolutionize space launches and commercial flights.