Every radar produces a radio frequency (RF) signal with specific characteristics that differentiate it from all other signals and define its capabilities and limitations. Pulse width (pulse duration), pulse recurrence time (pulse repetition interval), pulse repetition frequency, and power are all radar signal characteristics determined by the radar transmitter. Listening time, rest time, and recovery time are radar receiver characteristics. An understanding of the terms used to describe these characteristics is critical to understanding radar operation.
PULSE WIDTH (PW)
PW, sometimes called pulse duration (PD), is the time that the transmitter is sending out RF energy. PW is measured in microseconds. It has an impact on range resolution capability, that is, how accurately the radar can discriminate between two targets based on range.
The pulse width of the transmitted signal is to ensure that the radar emits sufficient energy to allow that the reflected pulse is detectable by its receiver. The amount of energy that can be delivered to a distant target is the product of two things; the output power of the transmitter, and the duration of the transmission. Therefore, pulse width constrains the maximum detection range of a target.
Weapons-control radar, which requires great precision, should be able to distinguish between targets that are only yards apart. Search radar is usually less precise and only distinguishes between targets that are hundreds of yards or even miles apart. Resolution is usually divided into two categories; range resolution and bearing resolution.
Range resolution is the ability of a radar system to distinguish between two or more targets on the same bearing but at different ranges. The degree of range resolution depends on the width of the transmitted pulse, the types and sizes of targets, and the efficiency of the receiver and indicator. Pulse width is the primary factor in range resolution. A well-designed radar system, with all other factors at maximum efficiency, should be able to distinguish targets separated by one-half the pulse width time.
PULSE RECURRENCE TIME (PRT)
Pulse recurrence time is also known as pulse repetition time. PRT is the time required for a complete transmission cycle. This is the time from the beginning of one pulse of RF energy to the beginning of the next. PRT is measured in microseconds. PRT is the same as pulse repetition interval (PRI), which is used in radar warning receivers and other electronic warfare support (ES) assets to discriminate between radar systems. It also affects maximum radar range.
PULSE REPETITION FREQUENCY (PRF)
One of the most important characteristics of a pulse radar signal is pulse repetition frequency. PRF is the rate at which pulses or pulse groups are transmitted. Generally, PRF is the number of pulses generated per second and is expressed in hertz (Hz). PRF and PRI are related in that PRI is the inverse of PRF.
A word of caution does not confuse the operating frequency of the radar, which is measured in Hz, with the pulse repetition frequency, which is also measured in Hz. They are entirely different characteristics of a pulsed radar signal.
In order to build up a discernible echo, most radar systems emit pulses continuously and the repetition rate of these pulses is determined by the role of the system. An echo from a target will therefore be 'painted' on the display or integrated within the signal processor every time a new pulse is transmitted, reinforcing the return and making detection easier. The higher the PRF that is used, then the more the target is painted. However, with the higher PRF the range that the radar can "see" is reduced. Radar designers try to use the highest PRF possible commensurate with the other factors that constrain it.
There are two other facets related to PRF that the designer must weigh very carefully; the beamwidth characteristics of the antenna, and the required periodicity with which the radar must sweep the field of view. Radar with a 1° horizontal beamwidth that sweeps the entire 360° horizon every 2 seconds with a PRF of 1080 Hz will radiate 6 pulses over each 1-degree arc. If the receiver needs at least 12 reflected pulses of similar amplitudes to achieve an acceptable probability of detection, then there are three choices for the designer: double the PRF, halve the sweep speed, or double the beamwidth. In reality, all three choices are used, to varying extents; radar design is all about compromises between conflicting pressures.
Pulse radar operating at an unvarying PRF is called constant PRF radar. Pulse radar systems can employ PRF stagger or PRF jitter as an electronic protection (EP) technique against repeater or synchronous jammers. The time between each pulse is the PRI. PRF stagger is accomplished by assuring that no adjacent PRIs are equal. The number of different PRIs generated is called the “position” of the stagger. Two-position stagger would have two PRI values, for example, 300 microseconds and 500 microseconds. PRF jitter may be considered a random stagger. It is also an EP technique to counter synchronous jammers. PRF jitter has no repeating pattern of PRI values.
RADAR RECEIVER CHARACTERISTICS
Pulse repetition frequency, pulse recurrence time, and pulse width are determined by the transmitter. The pulse radar signal characteristics that relate to receiver operation are rest time, recovery time (RT), and listening time (LT).
Rest time is the time between the end of one transmitted pulse and the beginning of the next. It represents the total time that the radar is not transmitting. Rest time is measured in microseconds.
Recovery time (RT) is the time immediately following transmission time during which the receiver is unable to process returning radar energy. RT is determined by the amount of isolation between the transmitter and receiver and the efficiency of the duplexer. A part of the high power transmitter output spills over into the receiver and saturates this system. The time required for the receiver to recover from this condition is RT.
Listening time (LT) is the time the receiver can process target returns. Listening time is measured from the end of the recovery time to the beginning of the next pulse, or PRT minus (PW + RT). Listening time is measured in microseconds.
Duty cycle is the ratio of the time the transmitter operates to the time it could operate during a given transmission cycle. The duty cycle of radar can be computed by dividing the PW by the PRT, or by multiplying the PW times the
PRF. Duty cycle has no units. Continuous Wave radars have a duty cycle of
100%, while early warning radars may have a duty cycle of around 1%.
Duty cycle is the fraction of time that a system is in an “active” state. In particular, it is used in the following contexts: Duty cycle is the proportion of time during which a component, device, or system is operated. Suppose a transmitter operates for 1 microsecond, and is shut off for 99 microseconds, then is run for 1 microsecond again, and so on. The transmitter runs for one out of 100 microseconds, or 1/100 of the time, and its duty cycle is therefore 1/100, or 1 percent. The duty cycle is used to calculate both the peak power and average power of a radar system.
Basic Radar Frequency
The power output of radar is normally expressed in terms of peak power or average power. Peak power is the amplitude, or power, of an individual radar pulse. It is simply the power, measured in watts or megawatts that are radiated when the transmitter is on. The power, radar transmits is normally used to determine the maximum detection range of that radar. However, it is the energy in a radar pulse that determines maximum radar detection range. Since power is the rate of flow of energy, the energy in a radar pulse is equal to the peak power multiplied by the time the radar is transmitting, or pulse width.
Average power is the power distributed over the pulse recurrence time. It can be computed using the formula
Average Power = Peak Power *(PW/PRT)
The energy transmitted by average power can be computed by multiplying average power by PRT. Since the energy in a set of pulses determines detection range, average power or energy provides a better measure of the detection range of radar than does peak power. Average power can be increased by increasing the PRF, by increasing the pulse width, or by increasing peak power.
The characteristics of an RF signal must be changed in order to transmit information on the signal. This process is called modulation. Modulation is accomplished by combining a basic RF signal, called a carrier wave, with a modulating signal that contains the desired information. The resulting waveform is then used to transmit the desired information.
One basic modulation technique is amplitude modulation (AM). The carrier wave is combined with a modulating signal containing information of varying amplitude. Waveforms produced have the same frequency as the carrier wave but with varying amplitude based on the information from the modulating signal. AM is used extensively in communications and broadcast radio transmissions.
Frequency modulation (FM) is another means of impressing information on a carrier wave. Frequency modulation is accomplished by combining the carrier wave with a modulating signal containing information of varying frequency. The waveform produced has the same amplitude as the carrier wave, but the frequency varies based on the information from the modulating signal. FM is used extensively in communications and commercial radio. FM is also used with continuous wave (CW) radars to make them more resistant to jamming and to add range determination capability.
A type of amplitude modulation known as pulse modulation (PM) is used in pulse radars to produce the short, powerful bursts of RF energy. PM combines the carrier wave with a rectangular pulse that acts like a switch. PM turns the transmitter on, leaves it on for a predetermined time, and then turns it off. The result is a waveform that produces radar pulses that can be used to measure range and angle to the target
The radar signal characteristics of PW, PRI, PRF, and power determine the maximum range and the range resolution capability of specific radar. When combined with the frequency of the carrier wave of the radar signal, these parameters provide a unique signature to identify a specific radar signal.
Modulation is the method used to put information on an RF carrier wave. The primary modulation techniques used in radar signal generation include amplitude, frequency, and pulse modulation. The radar signal characteristics of PRF, PRI, power, and modulation are the keys to understanding radar operation and jamming techniques.
ELECTRONIC warfare (EW) is the systems approach to the exploitation and control, to the maximum extent possible, of the electromagnetic (EM) spectrum. It is an important capability that can advance desired military, diplomatic, and economic objectives or, conversely, impede undesired ones. The use by an adversary of the EM spectrum for communications, navigation, and radar functions can be challenged by the techniques and technology of EW systems. In a military application, EW provides the means to counter, in all battle phases, hostile actions that involve the EM spectrum—from the beginning when enemy forces are mobilized for an attack, through to the final engagement. EW exploits the EM environment by sensing and analyzing an adversary’s application of the spectrum and imposing appropriate countermeasures (CMs) to hostile spectrum use.
CHARACTERISTICS OF RF RADIATION
In order for a radar system to determine range, azimuth, elevation, or velocity data, it must transmit and receive electromagnetic radiation. This electromagnetic radiation is referred to as radio frequency (RF) radiation. RF transmissions have specific characteristics that determine the capabilities and limitations of a radar system to provide these target discriminants, based on an analysis of the characteristics of the target return. The frequency of transmitted RF energy affects the ability of a radar system to analyze target return, based on time, to determine target range. RF frequency also affects the ability of the transmitting antenna to focus RF energy into a narrow beam to provide azimuth and elevation information. The wavelength and frequency of the transmitted RF energy impact the propagation of the radar signal through the atmosphere. The polarization of the RF signal affects the amount of clutter the radar must contend with. The ability of a radar system to use the Doppler effect in analyzing the radar return impacts the velocity discrimination capability of the radar.
The output signal from a typical radar system has several important characteristics that affect the capabilities and limitations of radar systems. The first characteristic considered is usually RF. The frequency of the transmitted signal is the number of times per second the RF energy completes one cycle. The basic unit of measurement is the hertz (Hz). One hertz equals one cycle per second. Most radar has an RF in the millions of hertz.
A characteristic of any RF signal is wavelength. Wavelength is a measure of the physical distance between peaks of a sine wave propagated in space. Though wavelength is measured in meters, most radar signals have wavelengths measured in centimeters or millimeters. The wavelength of a radar signal can be computed using the equation.
Wave length = (Speed of Light/ Radar frequency)
Another characteristic of a radio frequency wave is polarization. Polarization is determined by the radar antenna and refers to the orientation of the RF wave as it travels through space. There are two types of polarization: linear and circular.
Traveling electromagnetic energy has two components: an electrostatic field and a magnetic field. These two fields are always perpendicular to each other and perpendicular to the direction of travel. The polarization of the wave is defined in terms of the orientation to the electrostatic field. Many radar antennas are linearly polarized, either vertically or horizontally.
Some radars use circular polarization to improve target detection in rain.
Circular polarization can be right-hand, or left-hand orientation. For circular polarization, the direction of the electrostatic field varies with time and traces a circular locus about a fixed plane perpendicular to the direction of propagation.
For a right-hand circular polarized signal, the electrostatic vector appears to rotate in a clockwise direction. For a left-hand circular polarized signal, the rotation is counterclockwise. Circular polarization can be visualized by pointing the thumb of either hand in the direction of propagation and curling the fingers in the direction of electrostatic field rotation.
The impact of polarization on receivers and transmitters is fairly straightforward. If an antenna is designed to receive a particular polarization, it will have difficulty receiving a signal with an opposite polarization. This situation is defined as cross polarization.
The impact of cross polarization on electronic combat can be dramatic. If a radar warning receiver antenna is polarized to receive vertically polarized signals, a threat system employing a horizontally polarized radar signal may not be detected, or may be displayed on the scope well after the threat has acquired the aircraft. In addition, if the jamming antenna on an electronic attack (EA) system is also vertically polarized, it may not be able to jam this system.
The “Doppler effect” takes advantage of the fact that the frequency of RF waves will be changed or shifted when reflected from a target moving relative to the radar. The shifted frequency of the returning RF wave depends on the movement of the aircraft in relation to the radar.
In Figures, fo is the transmitted frequency of the radar, and ft is the frequency of the reflected RF wave from the target. For a stationary target, the frequency of the reflected signal will equal the frequency of the transmitted signal.
For a target moving toward the radar, the frequency of the reflected signal will be higher than the transmitted signal.
The reflected frequency for a target moving away from the radar will be lower than the transmitted frequency
The portion of the electromagnetic spectrum that today's electronic combat systems must deal with starts with radio waves and encompasses microwaves, infrared, and a small portion of the ultraviolet region.
Communications systems generally operate in the HF, UHF, and VHF regions.
Some satellite communications operate in the SHF region. Radars operate in the microwave region, normally from 0.2 – 200 gigahertz. Infrared systems operate in the region just below visible light.
Propagation characteristics of RF energy are profoundly affected by the earth's surface and atmospheric conditions. Any analysis of radar performance must take into account the propagation phenomena associated with RF radiation in a “real world” environment. The most important propagation phenomena include refraction, anomalous propagation (ducting), and attenuation.
In a vacuum, RF waves travel in a straight line. However, RF waves propagating within the earth's atmosphere do not travel in a straight line. The earth's atmosphere bends, or refracts, RF waves. One impact of the atmospheric refraction of RF waves is an increase in the line of sight (LOS) of the radar. This increase in radar LOS effectively extends the range of the radar system.
Atmospheric refraction of RF energy can also induce elevation measurement errors in radar systems.
The refraction of RF waves in the atmosphere is caused by the variation in the velocity of propagation with altitude.
Next Section :- Signal Characteristics
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While official Chinese media have been quite reactive and open with the launched of the People's Liberation Army Navy (PLAN or Chinese Navy) first Type 055 Destroyer (they did publish official images of the ceremony just two hours after it took place), details on the specifications of the ship, especially its sensor suite, are still scarce. But with plenty of imagery of Type 055 sensors now available, Navy Recognition contacted two retired French Navy officers (a former frigate commander and a former electronic warfare specialist) in order to try and learn more about the PLAN's latest surface combatant's sensors.
Upmast of Type 055 during its launch (left) and upmast of the shore integration facility at Wuhan's 701 institute (right)
This analysis based on open source intelligence (and mainly images) is limited because of the limited sources of images. All information here are hypotheses or "guesses" to the best of our sources' knowledge.
Our experts first underline that the sensor fit aboard the vessel is not complete yet. In the image above, you may notice that what is likely a TACAN (tactical air navigation system ) antenna fitted on top of the mast at the shore integration facility (right) is not present on the destroyer's actual mast (left). Some elements above the pilot house / bridge appear to be reinforced and are likely future placements for various sensors including an electro-optic s fire control system for the main gun. Navigation radar appear to be missing too. Note also that the 055 mast appear to be fitted with some kind of RCS reduction shields compared to the bare mast on the right.
Here is the detailed analysis by the experts we contacted:
1: UHF/VHF transmitters or R-ESM interceptor antenna
2: UHF/VHF receiver or R-ESM radio direction finding antenna
3: UHF antenna or possible Tactical Data Link
4: X-Band fire control radar for the missiles. For this role, the location is ideal (i.e nothing in its way, low risk of interference with other sensors).
5: This could be an IFF, however these antennas located above the bridge have different sizes. The large ones are likely linked to IFF roles but the smaller ones may well be LPI radars, surface (or combined) search radars or even the aforementioned "missing" navigation radars.
6: Same thing: Likely an LPI surface search or navigation radar antenna...
7: While many people on Chinese forums claim that these are L-Band radar arrays, but our experts really doubt those claims. "They may look like long range radar arrays, but they are most probably not radar array, even less so L-band ones. Such a low position, close to the waterline, would render such arrays very much ineffective". While still unusual, these arrays are probably jammers. Their locations are perfect to cover the entire flanks of the vessel. Plus they would work perfectly in conjunction with the two CIWS (HP/J-11 gun forward and HQ-10 missiles on top of the helicopter hangar).
8: Type 346B AESA Radar
Taking a closer look at the integrated mast: If the UHF/VHF antennas are located up-mast (as indicated in the side by side mast pictures), the R-ESM sensors may be fitted right above the X-Band radar (4). These two locations, so close to an X-band fire control radar may be prone to electromagnetic interference however. The small cylinder shape right above them is a jammer (the same type is already present aboard Type 052D destroyers at pretty much the same location). Finally the "Round Box" may house an antenna, an IFF system or simply the various connectors for all the systems fitted up the mast.
Last but not least, some more information on the Type 055's Type 346B AESA radar emerged. According to this source, the Type 055 is equipped with advanced active phased array radar with a larger diameter than the Type 346A radar fitted aboard the Type 052C class. One Type 346B radar array is larger than the 4.3x4.3 meter of the Type 346A arrays. The transmitter and receiver unit (is also using the latest Chinese gallium nitride (GaN) technology. Finally this new radar system is reportedly capable of fire control as well.
Source : - Navy recognition
Link to the original Article :- http://www.navyrecognition.com/index.php/focus-analysis/naval-technology/5374-analysis-sensor-and-electronic-warfare-suites-aboard-china-s-type-055-destroyer.html
Study of the movement of a body in the presence of air is called aerodynamics and this study is vitally important for the design of aircraft, missiles and rockets. The atmosphere as we know is densest close to earth's surface at sea level. As we go higher it becomes thinner (i.e.? the pressure and density are lower). The sensible atmosphere is upto a height of about 80 kilometers. The temperature also varies with height. The layer of atmosphere nearest to earth is called troposphere. Above that is stratosphere which is further subdivided into lower stratosphere and upper stratosphere. Beyond that, is ionosphere or ozonosphere and the last is exosphere. The very high speed fighter aircraft fly upto altitudes of about 30 km, while transport jets fly upto about 10-11 km.
The aircraft and missiles are bodies that are heavier than air and so can support their weights only if they produce a force to counter it. This force can be either lift force generated by the flow of air over the wings and body or generated by means of an engine in the form of thrust. This is done by helicopters or by aircraft with swing-engines (vertical takeoff type) where main engines can be swiveled. In missiles (most are launched vertically or with an inclination), a part of the weight is countered by the rocket engine thrust.
When we have a body with wings or without wings moving through air, there are forces generated which act on the body to oppose its motion (drag). In other words, this force must also be countered by the engine's thrust. .The drag force depends upon the fineness or bluntness and size of the body. To minimize the drag force one has to choose the aerodynamic shape such that functional requirements are also met.
In the missiles aerodynamic surfaces called wings, fins, and control surfaces and body called fuselage (with suitable nose shape conical or ogival followed by cylindrical) are designed to provide the necessary lateral maneouvrabilitv. This is achieved by deflecting control surfaces through actuation mechanism and thereby altering the balance of forces and generating turning moments. This happens at a very rapid rate.
In cruise missiles wings are provided to generate lift force while the missile flies in horizontal level mode. Most of the aerodynamics is studied by mathematical analysis of flow and then further validated by tests on scaled-down models in wind tunnel where forces are measured and correlations generated. An experimental data bank is generated for subsequent designers.
Aerodynamic considerations and structural design factors are intimately related to the propulsion and guidance aspects. The external missile shape and design is finalized keeping in view the needs of other subsystems and performance criteria. Thus mechanical and electric missile system engineers take equally important part in the overall missile design. This calls for a need to have a good insight and appreciation on the part of these personnel for the overall missile design.
Aerodynamic characteristics of various external components and their configuration aid their selection towards an optimum missile performance with respect to its lift and drag characteristics, aerodynamic stability, maneuverability, etc. Comprehensive and accurate data to enable a missile technologist to zero-in on a particular configuration is not readily available since much of the essential data is classified. Moreover, the requirement of stupendous quality of data desirable and sufficient for a fairly efficient design is a deterring factor too. However, an important asset the missile engineer: must have in discharging any R&D assignment is a sound understanding and knowledge of the fundamental principles involved in all the subsystems. The fundamentals of many technically specialized areas-aerodynamics, thermodynamics (mainly heat transfer), kinematics, propulsion, structural design-are a necessity though it makes the task of the aeronautical design engineer rather complex. Some of the major considerations the latter should have for an optimization of design are enumerated here.
The body of the missile may be divided into three major sections the - fore body or the nose, the mid-section and the aft or boat-tail section.
The body of the missile may be divided into three major sections the forebody or the nose, the Mid-section and the aft or boat-tail section.
Forebodies may have many varieties of shapes, most common of which are conical, ogival, power series or hemispherical. These shapes are used primarily on the missiles of supersonic speeds and are generally selected on the basis of combined aerodynamic, guidance and structural considerations. A hemispherical nose has very high drag from the aerodynamic drag or performance standpoint, but it is excellent from the standpoint of sturctural integrity, resistence to aerodynamic heating and amenability to certain types of guidance like infrared guidance. Since the pressure or wave drag may be several times that due to friction at supersonic speeds, careful selection of the nose shape needs attention to assure satisfactory performance of the overall system.
Conical forebody has given way to other types because of relative disadvantages but the conical one is the basis for the study of aerodynamic characteristics due to its simplicity. Briefly some of the flow characteristics about which an aero engineer will have to be very familiar are the formation of a shock wave, the shock angle, streamlines or flow direction and air properties between the shock wave and surface of the body. The supersonic flow over a cone has characteristics which are similar in appearance as that of a conical one but are markedly different in nature from those corresponding to two-dimensional flow (i.e., flow over a wedge).
An ogive is similar to a cone except that the planform shape is formed by an arc of a circle instead of a straight line. The ogival shape has several advantages over the conical section.
The hemispherical forebody type of nose is more widely used particularly in rnissiles which use infrared
(IR) seekers as their homing head. 'The ease of manufacture of this shape is one of the major reasons and advantages for its use in spite of its extremely high drag penalty on the missile. This is a measure of the extent to which an aerodynamic engineer must compromise to achieve an optimum arid feasible missile system. Many modified ogives are sorne of the other shapes of noses used in present-day missiles.
The mid-section in most missile configurations is cylindrical in shape. This shape is advantageous from the standpoint of drag, ease of manufacturing and load carrying capability. It is known that the total reaction of the missile at any instant has two components, the lift (components at right angle to the direction of airflow) and drag (those parallel to the direction of airflow). These may be positive or negative. It becomes desirable to have a greater lift than the drag and this can be done by using a curved suface. Angle of attack is the direction of the reaction force with respect to the free stream direction. Even at zero angle of attack, called as the zero-lift drag (x = O), some lift can be obtained by using what are called as airfoil sections.
The effects of mid-section or afterbody extension on the aerodynamic charcteristics of the conical and ogival nose bodies have been investigatted and it is seen that the effect of afterbody extension is to increase the lift coefficient and move the centre of pressure toward aft end as a result of body carry over and viscous cross-flow effects.
Base drag is the drag resulting from the wake or “dead air” region behind the missile. Base drag is less of a problem during powered flight but during free flight it can account for as much as 50% of total drag. Base drag can be reduced by tapering the tail (boat tailing).
A boat-tail is the transition section at the tail of a rocket (or other vehicle) that gradually narrows the body down to the motor diameter. It thereby helps reduce base drag.
Base drag is a component of aerodynamic drag caused by a partial vacuum in the missile's tail area. The vacuum is the hole created by the rocket's passage through the air. Base drag changes during flight. While the motor is firing, the drag is minimal since the tremendous volume of gas generated by the motor fills this void. The drag takes a sharp jump at burnout when this gas disappears.
Base drag can be reduced by the use of a boattail to transition the main body diameter down to the motor diameter which helps direct air into the evacuated area. When properly designed, a boattail can reduce base drag below zero (i.e. actually generate a small amount of forward thrust) by making use of the "pumpkin seed" effect.
Boat tail is the tapered portion of the aft section of a body. The purpose of the boat-tail is to decrease the drag of a body which has a 'squared off base. By 'boat-tailing' the rear portion of the body, the base area is reduced and thus a decrease in base drag is realized. However, the decrease in base drag may be partially nullified by the boat tail-drag.
In a nutshell, regarding the aerodynamic characteristics of the complete body the following generalisations may be made:
This is something what a photonic radar sees, the world around it.
In a race of making fifth generation combat aircrafts nations have realised that stealth capability is a major game changer in both wartimes and peace times. The rumoured destruction of Syrian S-300 battery by Israeli F 35s and the claimed uncontested flight of American F 22 Raptor at engagement ranges of the glorious S 400 prompts the Russians ( and everyone else) to think out an effective counter to this low observability technology. They seem to have found solution in an old abandoned concept where detection happens with the help of light and not radio waves. It works in similar way as that radar but uses infrared light beams instead of radio waves. If stated capabilities are to be believed then this new system would be able to detect stealth aircrafts at long ranges. The stealth aircrafts have measures taken to reduce the reflection of X band radio waves. The Radio Optic Phased Array Radar makers claim that since it uses light and not radio waves the optimisation of reduced radio waves reflections is not going to work. In this article we have attempted to dig out weather the claim is true or just another bragging. How exactly this thing works, what are its specific capabilities and whom are working in this field. Do give your opinion at the end.
The Space Shuttle was a partially reusable low Earth orbital spacecraft system operated by NASA, as part of the Space Shuttle program. In this article, we examine the monumental technology behind America's shuttle program, the mission it was designed to carry out.
First, let's look at the parts of the space shuttle and a typical mission.
The space shuttle consists of the following major components:
A typical shuttle mission is as follows:
To lift the 4.5 million pound (2.05 million kg) shuttle from the pad to orbit (115 to 400 miles/185 to 643 km) above the Earth, the shuttle uses the following components:
Lasers have become an indispensable part of modern day battlefield. Depending on the wavelength and power; lasers have wide spectrum of military applications from dazzling human eye to shooting down a UAV, guiding munitions for precision strike, imaging enemy targets and detecting chemical, biological and explosive materials.
Laser Science and Technology Centre (LASTEC) is working for the development of laser source technologies for Directed Energy Weapon (DEW), dazzling and imaging applications. It is developing standalone sensor systems using different laser sources for applications like detection and location of optical targets and detection and identification of chemical, biological and explosive materials. Other laser systems developed by LASTEC include unexploded ordnance disposal system and different variants of dazzlers. LASTEC is also working in the area of electro-optic countermeasure systems and development of laser materials.
Over the years, LASTEC has acquired the expertise in designing, testing and evaluation of different types of laser sources and systems. Gas Dynamic Laser and Chemical Oxygen and Iodine Laser Sources of the order of tens to hundreds of kilowatts for DEW application have been successfully developed and demonstrated. Recently, single mode kW class Fiber Laser Source was realized in collaboration with foreign experts making India only the 6th (known) country to possess the requisite technological knowhow. Efforts are channelized in scaling the power levels of these laser sources.
Scientific principles and techniques like Raman scattering and its variants, laser photo acoustics, laser induced fluorescence, differential absorption, etc. have been aptly applied to develop a number of equipment for detection and identification of various chemical, biological and explosives warfare agents in field conditions. These equipments are at various stages of evaluation and have tremendous application in low intensity conflict operations.
A number of sub-system level technologies for building the most modern state-of-the-art laser systems for military applications have also been successfully developed. Expertise in associated technologies like beam pointing and tracking, embedded system design and thermal management has been achieved. FACET, a state-of-the-art facility for test and evaluation of laser systems has been established at Ramgarh, Chandigarh.
LASTEC is committed to provide world class laser sources and systems, using state-of-the-art technologies and complying to the world standards. The systems being developed are contemporary to those developed by the world leading military laser manufacturers and are appropriate to the Indian conditions.
The indigenous laser sources, equipment and associated technologies developed by LASTEC/ sucoF ygolonhceTDRDO have been covered in two issues of Technology Focus. I hope this issue of will be useful in generating awareness about the tireless efforts of DRDO in developing cutting-edge defence technologies in the area of Laser Sources.
In missiles the control function is to ensure stability of the missile and implement the guidance signals received from external sources or generated onboard. The control, after processing the guidance signals, actuates the aerodynamic surfaces or thrust vector to generate turn of the missile speed and direction as required.
The guidance system is to detect whether the missile is flying above or below, to the left or right, of the required path. It obtains these deviations or errors and sends signals to the control system to reduce these errors to zero. The task of the control system therefore is to manoeuvre the missile quickly and efficiently making use of these signals.
In order to appreciate controls we shall briefly describe the motion of the missile as a free body. The missile has a total of six degrees of freedom of movement. Out of this, three degrees are translational or linear about the three axes viz., x, y and z; while the other degrees are rotational movement about three axes termed as pitch, yaw and roll.
Pitch is the turn of missile when it climbs up or down. Yaw is its turn to left or right. The roll is when the missile rotates about its longitudinal axis, which is also called roll axis. The longitudinal axis is the one running from nose to tail. If a missile is resting horizontally then, the pitch axis is the one which is normal to longitudinal axis and parallel to the horizontal axis and pitch axis. Missiles can roll when in motion due to various reasons.
There are missiles in which roll is controlled. Roll can be sensed onboard using a free gyro sensor and eliminated through actuation of controls. Some missiles have roll induced by design to use it for stability. The other axes which are controlled for motion are pitch and yaw axes.
Tejas is a 4+ generation, supersonic, highly maneuverable, multi-role, smallest and lightest in its class contemporary combat aircraft designed for the Indian Air Force designed and developed by DRDO. It is considered ‘game changer’ for India’s air defense preparedness.
The LCA has been designed and developed by a consortium of five aircraft research, design, production and product support organizations pooled by the Bangalore-based Aeronautical Development Agency (ADA), under Department of Defense Research and Development Organization (DRDO). Hindustan Aeronautics Limited (HAL) is the Principal Partner in the design and fabrication of the LCA and its integration leading to flight testing. Several academic institutions from over the country have participated in the development of design and manufacturing software for LCA. National teams formed by pooling the talents and expertise in the country are entrusted with the responsibility of the development of major tasks such as development of carbon composite wing, design, design of control law and flight testing. Several private and public sector organizations have also supported design and manufacture of various LCA sub-systems.
The LCA design was finalized in 1990 as a small tail-less delta winged machine with relaxed static stability (RSS) to enhance maneuverability performance and a host of other advanced features. A review committee was formed in May 1989 which reported that Indian infrastructure, facilities and technology had advanced sufficiently in most areas to undertake the project. It was decided that the full-scale engineering development (FSED) stage of the programme would proceed in two stages.
An air-breathing engine is an engine that takes in air from its surroundings in order to burn fuel. All practical air breathing engines are internal combustion engines that directly heat the air by burning fuel, with the resultant hot gases used for propulsion via a propulsive nozzle. A continuous stream of air flows through the air-breathing engine. The air is compressed, mixed with fuel, ignited and expelled as the exhaust gas. Thrust produced by a typical air-breathing engine is about eight times greater than its weight.
The thrust results from the expulsion of the working gases from the exhaust nozzle. To expel the gases from the nozzle at high velocity, the air entering the combustion chamber of the engine is compressed.
There are so many arguments and debates related to the detection of stealth fighters are happening around. Here we are presenting a simple method to find the detection range of radars against stealth fighters.
Below you can see the radar equation, various parameters that affect the range of radar and how these variables individually affect the detection range.
R max = 4th root of ((Pt * G2*lamda 2 * RCS) / ((4 Pie) 3 * P Min))
The variables in the above equation are constant and radar dependent except target RCS.
Over the last decades, air forces have always been the first military component engaged in all crises or conflicts, from the Falklands to the Gulf, from Bosnia to Kosovo, from Afghanistan to Libya, and more recently Mali, the Central African Republic and Iraq.
Military aviation is undoubtedly the most strategic weapon today, both in terms of combat effectiveness and of critical technologies implemented. In modern warfare, air dominance from day one is a must, so that air-to-ground and air-to-sea operations can be conducted safely and efficiently. The decisive place of the air component in modern warfare is demonstrated by the defense strategies decided by those nations who want to keep a leading role on the world stage. The RAFALE, with its “OMNIROLE” capabilities, is the right answer to the capability approach selected by an increasing number of governments.
It fully complies with the requirement to carry out the widest range of roles with the smallest number of aircraft. The RAFALE participates in permanent “Quick Reaction Alert” (QRA) / air-defense / air sovereignty missions, power projection and deployments for external missions, deep strike missions, air support for ground forces, reconnaissance missions, pilot training sorties and nuclear deterrence duties.
Lessons learned from the latest conflicts where air power was used, can be summarized into four overarching expectations about weapon systems by political decision makers:
The “OMNIROLE” RAFALE combines all these advantages: it is relevant against both traditional and asymmetrical threats, it addresses the emerging needs of the armed forces in a changing geopolitical context, and it remains at the forefront of technical innovation.
Thanks to its versatility, its adaptability and its ability to meet all air mission requirements, the RAFALE is the “poster child” transformational fighter which provides a way forward to air forces confronted to the requirement of doing “more” with “less”, in an ever-changing strategic and economic environment.
Of a moderate size, yet extremely powerful, superbly agile and very discrete, the latest type of combat aircraft from DASSAULT AVIATION does not only integrate the largest and most modern range of sensors, it also multiplies their efficiency with a technological breakthrough, the “multi-sensor data fusion”.
Omnirole by design
When the RAFALE programme was launched, the French Air Force and French Navy published a joint requirement for an omnirole aircraft that would have to replace the seven types of combat aircraft then in operation.
The new aircraft would have to be able to carry out a very wide range of missions:
A fully optimized airframe
The RAFALE, a fully “OMNIROLE” fighter, is available in three variants:
All three variants share a common airframe and a common mission system, the differences between naval and land versions being mainly limited to the undercarriage and to the arresting hook.
The RAFALE features a delta wing with close-coupled canards. In-house research in computational fluid dynamics has shown the specific benefits of close coupling between the wings and the canards: it ensures a wide range of centre of gravity positions for all flight conditions, as well as excellent handling throughout the whole flight envelope. The close-coupled canards / delta wing configuration is key to the combat performance of the RAFALE: even at high angle-of-attack, it remains fully agile, and its range performance in strike missions with heavy weapon loads is unmatched for such a compact design. Close-coupled delta-canard wing offers significantly higher maximum lift coefficient and positive trim lift on all control surfaces. Further, canards and wing control surfaces overlap in their functionality, unlike with horizontal tail configuration, leading to improved damage resistance. Rafale’s close-coupled canards will allow purely aerodynamic spin recovery. Also Rafale’s close coupled canards will reduce pressure point shift with increased speed, allowing Rafale to remain aerodynamically unstable at higher speeds than non-canard configuration would.
The aircrafts a close-coupled design with two large canards, four leading-edge slats, four trailing elevons and one rudder to optimize lift/drag and reduce side-slip in all flight phases. The hydraulic system powering the flying controls operates at over 345bar (5,000lb/in2).
The aircraft is capable of withstanding from −3.6g to 9g (10.5g on Rafale solo display and a maximum of 11g can be reached in case of emergency). The Digital Fly by wire Control System is a "g" demand system with +9.0g/29° angle of attack (AoA) limit in air-to-air mode and +5.5g/20° AoA limit in both of the two air-to-ground/heavy stores modes (ST1 and ST2) to cater for forward or aft centre of gravity. The aircraft continuously "recognises" the load it carries, but indicates and leaves the final DFCS mode selection to the pilot. Minus g limit in all modes is -3.2.The Rafale is an aerodynamically unstable aircraft and uses digital fly-by-wire flight controls to artificially enforce and maintain stability. The aircraft's canards also act to reduce the minimum landing speed to 115 knots (213 km/h; 132 mph); while in flight, airspeeds as low as 15 knots (28 km/h; 17 mph) have been observed during training missions. According to simulations by Dassault, the Rafale has sufficient low speed performance to operate from STOBAR-configured aircraft carriers, and can take off using a ski-jump with no modifications.
The Dassault Rafale is a relatively small, light airplane. Therefore, it isn’t surprising that its wing loading ratio (the ratio of its weight compared to its wing space) is just 306 kg/sq m, the second lowest ratio on the market after the JAS-39 Gripen. Its combat radius is also impressive – 1,852 kilometers. The Rafale also has an excellent rate of climb – 304 m/s, i.e. 60,000 ft/min. This means the plane can climb to its service ceiling (55,000 ft) in a minute. Dassault Rafale has instantaneous turn rate of 30 deg/s, sustained turn rate of 24 deg/s and roll rate of 290 deg/s.
Flight Control Systems
An advanced digital “Fly-by-Wire” (FBW) Flight Control System (FCS) provides for longitudinal stability and superior handling performance. The FCS is quadruple redundant with three digital channels and one separately designed analogue channel, with no mechanical back-up: design independence between channels is key to avoiding simultaneous anomalies on all channels.
The Flight Control System of the RAFALE attains the highest level of flight safety by leveraging on the extensive experience of DASSAULT AVIATION in Fly-by-Wire technology: over one million flight hours without a single accident caused by the FCS. The RAFALE is safe and easy to fly in all flight regimes, featuring the same precise, yet benign handling performance in all load-out configurations throughout the flight envelope.
The flight control system of the RAFALE offers auto flight in terrain following mode in all weather conditions, allowing the RAFALE to fly unobserved in the opponent’s airspace: an important survivability factor in a high threat environment.
Thanks to the DASSAULTs unique know-how in finite element modeling, the RAFALE airframe fatigue is monitored with the same gauge-free concept which has proved its worth on the MIRAGE 2000 fleet. Composite materials are extensively used in the RAFALE and they account for 70% of the wetted area. They also account for the 40% increase in the max take-off weight to empty weight ratio compared with traditional airframes built of aluminium and titanium.
The M88 – a new generation engine
The M88-2 is a new-generation turbofan engine offering a high thrust-to-weight ratio with easy maintainability, high despatch reliability and lower operating costs. The M88-2 incorporates advanced technologies such as integrally bladed compressor disks (“blisks”), a low-pollution combustor with smoke-free emissions, single-crystal high-pressure turbine blades, ceramic coatings, and composite materials.
The M88-2 power plant is rated at 10,971 lbs dry and 16,620 lbs with afterburner. It is equipped with redundant “Full Authority Digital Engine Control” (FADEC), which provides for carefree engine handling anywhere in the flight envelope: the throttle can be slammed from combat power to idle and back to combat power again, with less than three seconds from idle to full afterburner. The aircraft has a fixed flight refuelling probe and its canards and elevons operate in conjunction to act as a fully variable airbrake, with both features intended to save weight. Maximum speed is M1.8/750kt (1,390km/h), service ceiling 55,000ft (16,800m), and typical approach speed at mid-weight (15t) and 16° AoA an indicated 125kt.Powerful carbon brakes allow for landing distances as short as 450m without the need for a brake parachute.
Launched in 2008, the M88 TCO (“Total Cost of Ownership”) programme was initiated to further improve engine durability and bring support costs down. Capitalizing on the ECO project, SNECMA was able to upgrade the high-pressure compressor and the high-pressure turbine of the M88-2: cooling is ameliorated and stronger components have been introduced, boosting durability by up to 50%. Life expectancy between overhaul has been considerably expanded for a number of modules, helping further minimize the impact of planned maintenance on engine availability. The M88 is the subject of a constant improvement effort by SNECMA, leading to the latest M88-4E version, which builds on the TCO programme. This version, which offers a longer engine life, is now fully operational. Production deliveries began in 2012, and RAFALE aircraft now comes out of the production line fitted with M88-4Es.The Snecma M88 turbofans have been optimized to limit infrared delectability. And it also received Hot Spot treatment, to reduce the InfraRed Signature.
Although not a full-aspect stealth aircraft, the cost of which was viewed as unacceptably excessive, the Rafale was designed for a reduced radar cross-section (RCS) and infrared signature . In order to reduce the RCS, changes from the initial technology demonstrator include a reduction in the size of the tail-fin, fuselage reshaping, repositioning of the engine air inlets underneath the aircraft's wing, and the extensive use of composite materials and serrated patterns for the construction of the trailing edges of the wings and canards. 70% of the Rafale's surface area is composite. Many of the features designed to reduce the Rafale's visibility to threats remain classified. The radar cross section of the airframe has been kept to the lowest possible value by selecting the most adequate outer mold line and materials. Most of the stealth design features are classified, but some of them are clearly visible, such as the serrated patterns on the trailing edge of the wings and canards.
To achieve Stealth Dassault combine four factors:
• RCS reduction of the most reflective parts of the structure
• Development of passive detections
• EW suite capable of jamming and decoying
• Terrain following system
The minimal RCS of Rafale, according to Dassault engineer (1/10~1/20 of Mirage-2000's frontal RCS), should be 0.05 to 0.1 m2 class.
Rafale makes extensive use of radar-absorbent material (RAM) in the form of paints and other materials. RAM forms a saw-toothed pattern on the wing and canard trailing edges, for instance. The aircraft is designed to, so that its untreated radar signature is concentrated in a few strong "spikes," which are then suppressed by the selective use of RAM.
75% of Rafale surface structure and 30% of its mass are made of composites. Besides, the high amount of composites and RAM materials, ducted air intakes, Rafale also has a sawtooth design feature all over the airframe and even in the air intakes. These sawtooth are made of RAM materials and meant to scatter and absorb radar waves. IRST surface of rafale is covered in gold shield which reflects very less radar energy and thus has stealth. The internals of the cockpit are RCS shaped as well as the canopy containing gold and RAM coat on the mounts which reflects very less radar reflection.
Terrain following system
The Rafale is fitted with a multisensory terrain-following system operating at the pilot's choice from the radar or from a digital terrain database: the RBE2 radar can detect even unreported obstruction and the digital terrain database does away with telltale emissions where total covertness is required. There is also a radar altimeter available in nap-of-the-earth flight over water or flat land. Data fusion is part of the system to cross-check the sensors before feeding their data to a flight path computation module whose development has been carried out per the exacting standards of safety-critical engineering.
The terrain-following function integrated with the Rafale's flight control system actually flies the aircraft closer to the ground or the sea than would be reasonable for the crew flying in manual mode - and it does so with a demonstrated safety level even in blind weather. Rafale is designed to fly a terrain-avoidance/threat- avoidance profile at 5.5 g and 100 feet in altitude.
It remains a valuable help to the crew even when flying higher above ground level, allowing them to concentrate on other mission tasks without the burden -and energy consuming anxiety - of maintaining terrain clearance during hi-speed/low-altitude legs. With its high thrust and low wing-loading, the Rafale is equally at ease flying at treetop height: its aerodynamics - delta wing and canards - is ideal for low-level agility and ride quality, and its canard fore-planes do not block downward visibility. Flying low and fast in the clouds then becomes a real option: high altitude SAMs are no longer an issue since you fly under the radar coverage, and short range optically-guided air defenses are powerless against a foe they cannot see. Other short range air defense systems can be dealt with by the Spectra EW suite capable of jamming and decoying. Speed is part of the game too, since air defense engagement zones are dramatically reduced against transonic targets, even in clear weather.
The Rafale core avionics systems employ an integrated modular avionics (IMA), called MDPU (modular data processing unit). This architecture hosts all the main aircraft functions such as the flight management system, data fusion, fire control, and the man-machine interface. The total value of the radar, electronic communications and self-protection equipment is about 30 percent of the cost of the entire aircraft.
The Rafale features an integrated defensive-aids system named SPECTRA, which protects the aircraft against airborne and ground threats, developed as a joint venture between Thales and MBDA. Various methods of detection, jamming, and decoying have been incorporated, and the system has been designed to be highly re-programmable for addressing new threats and incorporating additional sub-systems in the future. Operations over Libya were greatly assisted by SPECTRA, allowing Rafales to perform missions independently from the support of dedicated Suppression of Enemy Air Defenses (SEAD) platforms.
The Rafale's ground attack capability is heavily reliant upon sensory targeting pods, such as Thales Optronics's Reco New Generation/Areos reconnaissance pod and Damocles electro-optical/laser designation pod. Together, these systems provide targeting information, enable tactical reconnaissance missions, and are integrated with the Rafale's IMA architecture to provide analysed data feeds to friendly units and ground stations, as well as to the pilot. Damocles provides targeting information to the various armaments carried by the Rafale and is directly integrated with the Rafale's VHF/UHF secure radio to communicate target information with other aircraft. It also performs other key functions such as aerial optical surveillance and is integrated with the navigation system as a FLIR.
Thales' Areos reconnaissance pod is an all-weather; night-and-day-capable reconnaissance system employed on the Rafale, and provides a significantly improved reconnaissance capability over preceding platforms. Areos has been designed to perform reconnaissance under various mission profiles and condition, using multiple day/night sensors and its own independent communications data links
RBE2-AA / AESA – “Active Electronically Scanned Array” radar
The RAFALE is the first operational – and so far, the only – European combat aircraft to use an electronic scanning radar. Developed by THALES, the RBE2 radar has benefited from a massive research effort and from THALES’ unmatched know-how based on past experience. Compared to radars with conventional antennas, unprecedented levels of situational awareness are attained with earlier detection and tracking of multiple targets. With its superior beam agility and its enormous computing power, the RBE2 offers outstanding performance that cannot be replicated by mechanical scanning radars.
In October 2012, the first RAFALE fighter equipped with an “Active Electronically Scanned Array” (AESA) RBE2 radar was delivered to the French MoD. The AESA provides a wide range of functions:
The RBE2-AESA is fully compatible in terms of detection range with the upcoming long range METEOR air-to-air missile. The AESA offers an unprecedented growth-potential for the future. In those situations where discretion becomes the single most important tactical factor, the RAFALE can rely on several other sensor systems. RBE-2 has 120* angular coverage while RBE-2AA (AESA) has 140* angular coverage.
The RBE2-AA radar system is an active electronically scanned array (AESA) radar system derived from the Rafale’s RBE2 radar. It replaces the mechanically steered array antenna by electronically steering exerted by up to several thousand of transmit-receive modules which enable maximum performance and versatility as well as enhanced reliability. The radar is using about 1000 GaAs T/R modules and is reported to deliver a greater detection range of 200 km, improved reliability and reduced maintenance demands over the preceding radar. Active electronic scanning makes it possible to switch radar modes quickly, thereby enabling operational functions to run simultaneously.
Front Sector Optronics – FSO
Developed by THALES, the “Front Sector Optronics” (FSO) system is fully integrated into the aircraft. Operating in the optronic wavelengths, it is immune to radar jamming and it provides covert long-range detection and identification, high resolution angular tracking and laser range-finding for air, sea and ground targets. Using those two optronic channels, the FSO provides day/night, long-range detection, recognition and identification of air, sea and land targets. The FSO does not emit any radiation and is insensitive to jamming. Fully integrated in the aircraft’s nav-attack system, it provides tactical information and target engagement. Its infrared capacities are essential during night flights, in particular for long-range target recognition. The FSO’s powerful TV sensor (cued by the RAFALE’s active and passive sensors) is truly valuable to positively identify targets in situations where a visual contact is required by the rules of engagement.
Front Sector Optronics (FSO) provides a tele-lens picture of the target. It allows target tracking, through IR (Infra-red search and track) and visual sensors: air targets at ranges up to 100 kilometers, surface or sea targets at up to 6 kilometers. The covert approach capability of the FSO is especially valuable in air policing and intercepts, where the TV picture of the target provides early visual identification and detection of suspect manoeuvres. The IR Search and Track channel uses sophisticated processing algorithms for the automatic detection and tracking of airborne threats and targets on the ground.
Air-to-Air and Air-to-Surface Tracking
Infrared Search and Track (Growth potential):
Air-to-Air or Air-to-Surface identification and ranging:
Advantages and functions:
Identification and Tracking:
SPECTRA – internal Electronic Warfare suite
SPECTRA -Self-Protection Equipment to Counter Threats for Rafale Aircraft. Jointly developed by THALES and MBDA, the SPECTRA internal “Electronic Warfare” (EW) system is the cornerstone of the RAFALE’s outstanding survivability against the latest airborne and ground threats. It is fully integrated with other systems in the aircraft, and it provides a multi-spectral threat warning capability against hostile radars, missiles and lasers.
The SPECTRA system carries out reliable long-range detection, identification and localization of threats, allowing the pilot to instantly select the most effective defensive measures based on combinations of radar jamming, infrared or radar decoying and evasive maneuvers. The angular localization performance of the SPECTRA sensors makes it possible to accurately locate ground threats in order to avoid them, or to target them for destruction with precision guided munitions. Additionally, SPECTRA fulfils new functions in a combat aircraft, while significantly participating in the determination of the aircraft's tactical situation, and providing the crew with operational advantage by performing accurate threat location. By virtue of its fully passive situational awareness capability, SPECTRA are a major contributor to the low observability concept of Rafale. SPECTRA gives Rafale firing solution with 1* precision at 200 km.
The outstanding capability of SPECTRA regarding airborne threat localization is one of the keys of the RAFALE’s superior situational awareness. Also instrumental in SPECTRA’s performance is a threat library that can be easily defined, integrated and updated on short notice by users in their own country, and in full autonomy. SPECTRA now include a new generation missile warning system that offers increased detection performance against the latest threats.
Using sophisticated techniques, such as interferometry for high precision DOA and passive ranging, digital frequency memory for signal coherency and active phased-array transmitters for maximum effectiveness and covertness, the highly advanced multi-sensors and artificial intelligence data fusion capabilities of SPECTRA provide the Rafale aircraft with the best chance to survive in harsh and lethal environments. The Rafale combat aircraft and the SPECTRA system are fully operational onboard the French Navy's Rafale.
The SPECTRA system consists of two infrared missile warning sensors (Détecteur de Départ Missile Nouvelle Génération). A new generation missile warning system (DDM NG) is currently being developed by MBDA. DDM NG incorporates a new infrared array detector which enhances performance with regard to the range at which a missile firing will be detected (with two sensors, each equipped with a fish-eye lens, DDM NG provides a spherical field of view around the aircraft). The DDM-NG also offers improved rejection of false alarms and gives an angular localization capability which will be compatible with the future use of Directional Infrared Counter Measures (DIRCM). DDM-NG has an advanced Missile Warning System covering most of the sphere around the aircraft. In particular it provides the capability to detect Manpad missiles by detecting their burning engines. DDM-NG is a passive, imaging infrared Missile Warning System using the latest advances in sensor technology and processing algorithms. The DDM-NG system’s long detection range, spherical field of view and advanced software provides the highest level of performance.
Thales Group and Dassault Aviation have mentioned stealthy jamming modes for the SPECTRA system, to reduce the aircraft's apparent radar signature. It is not known exactly how this work or even if the capability is fully operational, it employs active cancellation technology, such as has been tested by Thales and MBDA. Active cancellation, a unique EW technique that locates an enemy radar in range and bearing, calculates the scatter that it will receive from the Rafale, and transmits an exact mimic of the aircraft’s actual echo — but one-half wavelength out of phase, so that the radar sees nothing.
SPECTRA is divided into different modules and sensors strategically positioned throughout the airframe to provide all-round coverage. The latest advances in micro-electronic technology have led to a new system which is much lighter, more compact and less demanding than its ancestors in terms of electrical and cooling powers.
Heart of the SPECTRA is the GIC computer (Gestion de l'Interface et CompatibilitÃ©) comprising 3 processors.
DBEM (DÃtection et Brouillage ElectromagnÃtique) - RWR/ECM
DDM (DÃ©tecteur infrarouge de DÃ©part de Missiles) - MLD
Data from all the sensor suites are fused and processed by a central computer, which prioritizes and activates the relevant countermeasures, based upon comparison between the received signals and an onboard threat library. RF jamming is transmitted through active phased array antennas. Employment of this advanced technology allows the jamming signal to be concentrated in the sector where it is needed, not only increasing its effectiveness, but also reducing the probability of intercept by the adversary’s own sensors. In addition to RF jammers, the SPECTRA system incorporates mechanical countermeasures for the dispensing of chaff and decoys that are effective in either electromagnetic or infrared domains. In addition to protecting the Rafale, SPECTRA also has a valuable offensive function. Fused data from the sensors provides threat tracks in the weapon system, which can be displayed in the cockpit. These tracks can be used for targeting in the defense suppression role. Additionally, the data product from the SPECTRA sensors is of very high quality, so that the system can be used for the gathering of Elint (electronic intelligence). Pop-up threats can be compared against the threat library, which can be updated with new information. The product of SPECTRA is also recorded and can be downloaded upon the aircraft’s return to base for more detailed analysis in the ground-based support centre. In this way master threat libraries can be updated, and revised data files produced for subsequent missions.
The net-centric capability of the RAFALE hinges on its open architecture, its data fusion software and its compatibility with a variety of data links, which “plug” the RAFALE into the integrated battlespace .A secure high-rate data link is provided to share data in combined air operations in real time with other aircraft in the formation, airborne and surface command and control centre’s, tactical air controllers or other friendly assets. The Link 16 data link is also available to those customers cleared to operate it. As a net-centric capable asset, the RAFALE can exchange images. The Rover (“Remotely Operated Video Enhanced Receiver”) is an element of this capability which allows aircrews and forward air controllers on the ground to share videos or images of the target. It helps prevent blue-on-blue incidents and collateral damage, a decisive advantage in peacekeeping operations.
DAMOCLES and TALIOS- Laser designation pods
The DAMOCLES laser designator pod designed by THALES brings full day and night laser designation capability to the RAFALE, with metric precision. It permits laser-guided weapons to be delivered at stand-off range and altitude. The IR sensor of the DAMOCLES pod operates in the mid-wave infrared band, allowing it to retain its effectiveness in warm and / or humid conditions. DAMOCLES is interoperable with all existing laser-guided weapons. THALES is now working on TALIOS, a new generation multifunction targeting pod.
TALIOS is an acronym for Targeting Long-range Identification Optronic System. It is follow-on from the company’s Damocles navigation and targeting pod, for which Thales took 120 orders, two-thirds of them for export.
Like other such pods from competing suppliers, operators found a new role for Damocles as an imagery sensor–the so-called Non-Traditional Intelligence, Surveillance and Reconnaissance (NTISR) role. Thales says that in designing TALIOS with the latest sensors and stabilization techniques, and by adding a third optical window, it has eliminated some of the shortcomings of previous pods when collecting imagery. For instance, it has a wide field of view, and is able to operate throughout the mission.
Further, Thales claims that TALIOS is the only pod to provide color imagery to NATO standards, while other new features include day or night operation from any altitude; scene-matching; and automatic detection and tracking of mobile targets. TALIOS was previously known as the Pod de Désignation Laser de Nouvelle Génération (PDL-NG). The TALIOS pod is the same shape as Damocles, and approximately the same weight, and can therefore be substituted easily.
AREOS – Recce pod with Quick Analysis Capability
AREOS - Airborne REcce Observation
For both strategic and tactical reconnaissance missions, the French Armed Forces have adopted the new generation THALES AREOS reconnaissance system for the RAFALE.As demonstrated in Libya, Mali, the Central African Republic and Iraq, this high-tech, day and night equipment can be used in a wide range of scenarios, from stand-off distance at high altitude down to high speed and extremely low-level. To shorten the intelligence gathering cycle and accelerate the tempo of operations, the AREOS pod is fitted with a data link which allows high resolution images to be transmitted back to military decision makers in real time. The outstanding performance of AREOS in stand-off reconnaissance makes it a sensor with a true pre-strategic value. It can flight up to 600 knots, and can withstand the shock of carrier operations.
The pod can be operated in fully autonomous mode, without any intervention by the crew. The AREOS Reco NG pod is 4.6 meters long (15 ft.) and weighs 1,100 kg (2,420 lb), making it compatible with the Rafale, as well as the Mirage 2000 if needed. Up front on the pod, the HA/MA (high altitude/medium altitude) optical sensor supports photography at medium range, or even long-range at standoff distance. The AREOS Reco NG offers an identification range of several tens of kilometres – two to three times the range of the Presto pod currently deployed on Mirage F1CR aircraft in Afghanistan.
Located aft in the AREOS pod, the low-altitude sensor supports horizon to horizon photography at an altitude of only 60 meters (200 ft) and very high speeds. The pod operates automatically, whether working in intermittent, zone coverage or terrain-following mode, and always knows its exact position in space, so that it can control the pointing of its optical sensors in both pitch and roll. Its control capability is based on data transmitted by its own inertial reference system, correlated with data from the nav-attack system on the aircraft itself. As soon as the shots are taken, they are automatically overlaid on a digital elevation model, geo-referenced and assembled to provide a complete mosaic of the target. For greater flexibility and coverage, the optics move fore-and-aft within the head of the rotating pod.
The images are then stored on a hard disk in the pod. They can be transmitted to a ground image receiving and processing station in real time, via a high-speed microwave link.The recce pod can also operate in video mode by using successive images and by measuring the displacement of a moving object from one image to another, it can estimate its speed. Battlefield trials based on a hundred test flights enabled the CEAM military aircraft test center to validate the operation of the sensors and their tactical use in conjunction with the Rafale. Test flights covered the full range of scenarios, from conventional to unusual, including tests of opportunity targets involving aircraft being reassigned in the middle of their sortie, through the L16 datalink.
The pod is very easy to operate the crew sees a pointer on their digital map with a mission request. All they have to do is indicate that they accept the mission and slave the pod to the pointer. It’s fast, easy, and there’s no risk of a misunderstanding, since no radio communications are involved.
One of the limitations of imaging-cum-targeting pods has been the need for aircrew to slew the pod-head to the area of interest, and then switch from wide to narrow field-of-view for positive identification and designation of targets. In so doing, situational awareness can be lost.
Thales claims that it has a unique solution, which it has named Permanent View, with geo-referenced imagery from a wide area that is likely to be covered on the mission is stored in the pod. If (for instance) a pilot sees an explosion on the ground or is informed of a target by troops-in-contact, he can arrange to see the surrounding terrain on a cockpit display, with the pod’s field-of-view indicated at center-screen.
This makes slewing the pod easier, and also helps the pilot avoid maneuvers that might temporarily mask the target.
The sheer power of multi-sensor data fusion
In essence, the “multi-sensor data fusion” concept implemented into the RAFALE allows the pilot to act as a true “tactical decision maker”, rather than being only a sensor operator.
PCWRITE - This combination of "letters" appears in the lower left corner of the HLD - Head Level Display, giving a real-time and instant confirmation of which sensors are signaling at that moment. Each letter representing either the RBE2 AESA radar, the Infrared / Laser / TV Front-Sector Optronics (FSO), the internal system of electronic warfare SPECTRA EW, IFF (identification friend-or-foe), and data link are merged into a unified and clear visual symbolism directly on the SA display (situational awareness), and that means keeping the pilot in the situational loop. Rarely (not witnessed at any time during our evaluations) would the pilot ever be unaware of the environment within the 360º “bubble” surrounding the aircraft. The core of these enhanced capabilities of the RAFALE lays in a new “Modular Data processing unit” (MDPU) incorporating “commercial off the shelf” (COTS) elements. It is composed of up to 19 flight “line-replaceable units” (LRUs), with 18 of them individually providing 50 times the processing power of a typical mission computer employed in previous generation fighters. The MDPU is the cornerstone of the upgradeability of the RAFALE. It allows a seamless integration of new weapons and new capabilities to maintain the war fighting relevance of the RAFALE over the years as tactical requirements evolve, and as the computer industry keeps rolling out new generations of processors and software.
The “multi-sensor data fusion” provides a link between the battle-space surrounding the aircraft and the pilot’s brain with its unique ability to grasp the outcome of tactical situations and make sensible decisions. It hinges on the computing power of the MDPU to process data from the RBE2-AESA radar, the “Front Sector Optronic” (FSO) system, the SPECTRA EW system, the IFF, the MICA infrared seekers, and the data link.
Implementation of the “multi-sensor data fusion” into the RAFALE translates into accurate, reliable and strong tracks, uncluttered displays, reduced pilot workload, quicker pilot response, and eventually into increased situational awareness.
It is a full automated process carried out in three steps:
A unique “Man-Machine Interface” (MMI)
DASSAULT AVIATION has developed a very easy to use pilot interface (MMI), combining the “Hands on Throttle and Stick” (HOTAS) control concept with touch screens. It relies on a highly integrated suite of equipment with the following capabilities:
The comprehensive design of the cockpit provides for everything that aircrews can expect from an “OMNIROLE” fighter: a wide field of view at the front, on both sides, and at the rear, a superior agility, an increased G-protection with 29° tilted seats, and an efficient air conditioning system demonstrated under all climates.
The Rafale's glass cockpit was designed around the principle of data fusion – a central computer intelligently selects and prioritizes information to display to pilots for simpler command and control. The primary flight controls are arranged in a hands-on-throttle-and-stick (HOTAS)-compatible configuration, with a right-handed side-stick controller and a left-handed throttle. The seat is inclined rearwards at an angle of 29° to improve g-force tolerance during maneuvering and to provide a less restricted external pilot view.An intelligent flight suit worn by the pilot is automatically controlled by the aircraft to counteract in response to calculated g-forces. Dassault also plans to introduce an automatic "g-loc" recovery mode. It has framed canopy providing 360* horizontal and 197,7* vertical visibility, including 16* over the nose, 1,7* over the tail and 27* over the sides, with a maximum of 54* over the side visibility.
Great emphasis has been placed on pilot workload minimization across all operations. Among the features of the highly digitized cockpit is an integrated direct voice input (DVI) system, allowing a range of aircraft functions to be controlled by spoken voice commands, simplifying the pilot's access to many of the controls. Developed by Crouzet, the DVI is capable of managing radio communications and countermeasures systems, the selection of armaments and radar modes, and controlling navigational functions. For safety reasons, DVI is deliberately not employed for safety-critical elements of the aircraft's operation, such as the final release of armaments.
For displaying information gathered from a range of sensors across the aircraft, the cockpit features a wide-angle holographic head-up display (HUD) system, two head-down flat-panel color multi-function displays (MFDs) as well as a central collimated display. These displays have been strategically placed to minimize pilot distraction from the external environment. Some displays feature a touch interface for ease of Human–computer interaction (HCI). A head-mounted display (HMD) remains to be integrated to take full advantage of its MICA missiles. The cockpit is fully compatible with night vision goggles (NVG).
Entry and exit to the B/C models is via a ground crew-positioned vertical ladder, but the M model has an integral drop-down step. Seat height and rudder pedal adjustment is electric, and the cockpit is a classic fighter "snug" fit, but with all the required flight switches forward of the 3-9 body line. The single throttle and sidestick controller contain over 34 separate switches, many with multifunctions, but the main switches such as airbrake, radio telecommunications, auto pilot and auto throttle were "chunky" and easy to differentiate.
The left and right lateral head-down display screens were touch sensitive with additional L/R rotary and L/R finger switches to designate and control display modes. The head-level display (HLD) allowed for a wide-angle view of the tactical situation and is focused at infinity, so there is no need to refocus your eyes when scanning rapidly between head-up and head-level. Advances in display technology may enable a future HLD to retain the same advantages in a more flat panel display and give more cockpit space.
The wide-angle (30° x 20°) holographic HUD meant the displayed symbology was delightfully uncluttered and sharply focused and could be viewed completely without any head movement away from a design eye point position.
After the sideways-hinged canopy (designed to allow for unrestricted ejection seat removal if required) was closed electrically and with a rapid engine start using the auxiliary power unit completed, it only take about 90s ready to taxi after engine stabilization. Taxi speed can easily control, because the residual ground thrust is limited by keeping both "mini-throttles" (acting as low-pressure cocks) in the "idle" position before setting them to "normal" for take-off. Ground steering was highly accurate and responsive, and the brakes were very smooth and progressive.
Safety of Pilots
Pilot safety is safeguarded by various systems of the Rafale. Starting with the seat, a tilt of 29º distributes the gravitational effect, preventing G-Loc; even at 9Gs that Dassault’s fighter can pull without surpass the operational load factors parameters, in air-to-air mode. The GPW - Ground Proximity Warning, alerts by audible and visual signals, to avoid colliding with the ground when the attitude and altitude of flight correspond to an approach to the surface. If needed, a pre-programmed recovery system can be accessed by the pilot, and in the case of spatial disorientation, there is an "anti-spin” feature even though the Rafale has not shown any tendency to spin, even in the corners of the envelope. Nevertheless, once anti-spin switch is activated, the flight computers redirect the aircraft to a safe flight regime with wings leveled, 5 degrees of climb, and 350 kts. In the absence of reaction by the pilot, GPW will also automatically initiate a maneuver leading back to the leveling of the airplane’s wings and a positive attitude to climb. If Rafale safety features prevents CFIT events (controlled flight into terrain), it is exactly on the low flight (close to the ground - hilly or flat - or water) that the fighter shows one of its greatest strengths. With a unique capability and clever use of Terrain Following mode is much more than an aid to agile piloting at very low altitude.It acts as an extra pilot in the cockpit, since the security in the fidelity of the system - which combines the redundancy of AESA radar and the digital database, leave pilot entirely focused on the tactical objective of the mission: namely, to deliver the "package" in the right place at the right time... and yet, track airborne targets and threats during the raid.
An on-board oxygen generating system, developed by Air Liquide, eliminates the need to carry bulky oxygen canisters. The Rafale's flight computer has been programmed to counteract pilot disorientation and to employ automatic recovery of the aircraft during negative flight conditions. The auto-pilot and auto throttle controls are also integrated, and are activated by switches located on the primary flight controls.
A full range of advanced weapons
Initial deliveries of the Rafale M were to the F1 ("France 1") standard, these had been equipped for the air-to-air interceptor combat duties, but lacked any armaments for air-to-ground operations. Later deliveries were to the "F2" standard, which added the capability for conducting both air-to-ground and reconnaissance operations; the first F2 standard Rafale M was delivered to the French Navy in May 2006. Starting in 2008 onwards, Rafale deliveries have been to the nuclear-capable F3 standard, and it has been reported that all aircraft built to the earlier F1 and F2 standards are to be upgraded to become F3s. The mission system of the RAFALE has the potential to integrate a variety of current and future armaments.
The RAFALE’s stores management system is Mil-Std-1760 compliant, which provides for easy integration of customer-selected weapons. With its 10-tonne empty weight, the RAFALE is fitted with 14 hard points (13 on the RAFALE M). Five of them are capable of drop tanks and heavy ordnance. Total external load capacity is more than nine tonnes (20,000 lbs.). “Buddy-buddy” refuelling missions can be carried out in portions of the airspace out of reach of dedicated and vulnerable tanker aircraft.
With its outstanding load-carrying capability and its advanced mission system, the RAFALE can carry out air-to-ground strikes, as well as air-to-air attacks and interceptions during the same sortie. It is capable of performing several actions at the same time, such as firing air-to-air missiles during a very low altitude penetration phase: a clear demonstration of the true “OMNIROLE” capability and outstanding survivability of the RAFALE.
Guns: 1× 30 mm (1.18 in) GIAT 30/M791 autocannon with 125 rounds
Rafale has the biggest gun on the market (ex aequo with Sukhoi aircraft): a hefty 30mm GIAT gun firing incendiary rounds. This makes the Rafale an excellent choice for both air to air and air to ground combat, as its 30mm rounds would provide excellent support for troops on the ground. 30mm is the caliber of the guns of most APCs and IFVs.
The MBDA MICA is an anti-air multi-target, all weather, fire-and-forget short and medium-range missile system. It is intended for use both by air platforms as individual missiles as well as ground units and ships, which can be equipped with the rapid fire MICA Vertical Launch System. It is fitted with a thrust vector control (TVC) system Range Air-launched 0.2–50 km at Mach 4.
Exocet AM39 is the airborne version of the Exocet anti-ship missile family. It can be launched from strike aircraft, Maritime Patrol Aircraft and helicopters. With a range of up to 70 km, depending on the altitude and speed of the aircraft, the Exocet AM39 enables the aircraft to remain at range from enemy air defenses. When carrying out a low altitude attack, the missile may also be launched under the target ship radar coverage. Ingress is at a very low altitude over the sea (sea skimming).
Built-in ssup portability
The RAFALE supportability and mission readiness claims are supported by the undisputed track record of the earlier generation of French fighters, such as the combat-proven MIRAGE 2000. From the early beginning of the development phase, the French MoD assigned very stringent “integrated logistic support” (ILS) requirements to the RAFALE programme. “Computer aided design” (CAD) with the Dassault Systèmes CATIA software suite, concurrent engineering and bold technological choices ultimately produced an ILS system that exceeds the original supportability requirements.
The following examples, selected from a range of unique and innovative features, demonstrate the advance in reliability, accessibility and maintainability brought by the RAFALE:
From 2006 to 2011, French Air Force and Navy RAFALE fighters were engaged in countless combat missions in Afghanistan where they demonstrated a very high proficiency and a tangible military value. The AASM/HAMMER precision-guided modular air-to-surface armament, PAVEWAY laser-guided bombs, and the 30 mm cannon were employed on many occasions, scoring direct hits with remarkable precision.
In 2011, French Air Force and French Navy RAFALE fighters were successfully engaged in coalition operations over Libya. They were the first fighters to operate over Benghazi and Tripoli, and they carried out the whole spectrum of missions the RAFALE was designed for: air-superiority, precision strikes with HAMMERS and laser-guided bombs, deep strike with SCALP cruise missiles, Intelligence, Surveillance, Tactical Acquisition and Reconnaissance (ISTAR) and Strike Coordination And Reconnaissance (SCAR). During the Libyan conflict, hundreds of targets – tanks, armored vehicles, artillery emplacements, storage dumps, command centres and air-defense systems (SA-3 Goa and SA-8 Gecko fixed and mobile SAM launchers) – were hit with devastating accuracy by RAFALE aircrews.
French Air Force RAFALES have taken a leading role in Mali, helping destroy enemy infrastructure and support friendly troops in contact. Four RAFALES undertook the longest raid in French Air Force history, taking off from Saint-Dizier, in eastern France, and landing in N’Djamena, in Chad, after hitting 21 targets and spending no less than 9 h 35 min airborne. The French Air Force quickly set up a forward operating base in Chad, and the RAFALE detachment later grew to eight aircraft. This represented the first time the RAFALE had operated from a FOB in Africa.
More recently, RAFALES were engaged in support of peace-keeping operations in the Central African Republic, and as part of a wide international coalition in Iraq.
Courtesy :- Official Websites of Dassault , Thales, MBDA
:- Wikipedia and many other internet resources
A rocket engine is a type of jet engine that uses only stored rocket propellant mass for forming its high speed propulsive jet. Rocket engines are reaction engines, obtaining thrust in accordance with Newton's third law. Rocket thrust results from the high speed ejection of material and does not require any medium to "push against", so they are well suited for uses at very high altitude and in space. There are two main categories of rocket engines; liquid rockets and solid rockets. Under normal temperature conditions, the propellants do not burn; but they will burn when exposed to a source of heat provided by an igniter.
A) Solid fuel rockets
Solid-fuel rocket engines were the first engines created by man. Solid rocket engines are used on air-to-air and air-to-ground missiles, on model rockets, and as boosters for satellite launchers. In a solid rocket, the fuel and oxidizer are mixed together and packed into a solid cylinder. Once the burning starts, it proceeds until all the propellant is exhausted. With a liquid rocket, you can stop the thrust by turning off the flow of propellants; but with a solid rocket, you have to destroy the casing to stop the engine. One of the biggest problems with solid fuel rocket engines is that once started, the reaction cannot be stopped or restarted. This makes them considered uncontrollable. Therefore, solid fuel rockets are more widely used for missiles, or as booster rockets. A solid rocket is much easier to handle and can sit for years before firing.
A hole through the cylinder serves as a combustion chamber. When the mixture is ignited, combustion takes place on the surface of the propellant. A flame front (the surface of the interface that faces reactants is often termed as the flame front. Similarly, the surface the faces the products can be termed as the flame back) is generated which burns into the mixture. The combustion produces great amounts of exhaust gas at high temperature and pressure. The amount of exhaust gas that is produced depends on the area of the flame front and engine designers use a variety of hole shapes to control the change in thrust for a particular engine. The hot exhaust gas is passed through a nozzle which accelerates
B) Liquid fuel rockets
In a liquid rocket, the propellants, the fuel and the oxidizer, are stored separately as liquids and are pumped into the combustion chamber of the nozzle where burning occurs. Liquid rockets tend to be heavier and more complex because of the pumps and storage tanks. The propellants are loaded into the rocket just before launch. Liquid rocket engines are used on the Space Shuttle to place humans in orbit, on many un-manned missiles to place satellites in orbit, and on several high speed research aircraft following World War II
All liquid rocket engines have tankage and pipes to store and transfer propellant, an injector system, a combustion chamber which is very typically cylindrical, and one (sometimes two or more) rocket nozzles. Liquid systems enable higher specific impulse than solids and hybrid rocket engines and can provide very high tankage efficiency.
Liquid rockets can be mono-propellant rockets using a single type of propellant, bi-propellant rockets using two types of propellant, or more exotic tri-propellant rockets using three types of propellant.
According to the type of propellants used in the rockets we can classify liquid fuel rocket engines into cryogenic, Semi cryogenic & hypergolic
A cryogenic engine uses cryogenic fuels. A cryogenic technology is the process of involvement or including of usage of rocket propellants at a cryogenic temperature. It can be combination of liquid fuels such as: liquid Oxygen (LOX), and liquid Hydrogen (LH2) as an oxidizer and fuel in the different mixtures or proportions. The mixture of fuels offer the highest energy efficiency for the rocket engines that produces very high amount of thrust. Here, the Oxygen remains liquid only at the temperature below (-183 C) and Hydrogen below (-253 C). This is a type of rocket engine that is functionally designed to use the oxidizer which must be refrigerated in the liquid state. Sometimes, the liquid nitrogen (LN2) is used as a fuel because the exhaust is also nitrogen.
The engine components are also cooled so the fuel doesn’t boil to a gas in the lines that feed the engine. The thrust comes from the rapid expansion from liquid to gas with the gas emerging from the motor at very high speed. The energy needed to heat the fuels comes from burning them, once they are gases. Cryogenic engines are the highest performing rocket motors. One disadvantage is that the fuel tanks tend to be bulky and require heavy insulation to store the propellants. Their high fuel efficiency, however, outweighs this disadvantage.
A Cryogenic rocket stage is more efficient and provides more thrust for every kilogram of propellant it burns compared to solid and earth-storable liquid propellant rocket stages. Specific impulse (a measure of the efficiency) achievable with cryogenic propellants (liquid Hydrogen and liquid Oxygen) is much higher compared to earth storable liquid and solid propellants, giving it a substantial payload advantage.
Dont forget to see this awesome video by ISRO - https://www.youtube.com/watch?v=nfZBIHGAiuk
Semi cryogenic engines using liquid oxygen and kerosene as propellants. They are considered relatively environment friendly, non-toxic and non corrosive. In addition, the propellants for semi-cryogenic engine are safer to handle & store. It will also reduce the cost of launch operations. Apart from this combination of Liquid oxygen (LOX) and alcohol (ethanol, C2H5OH) Liquid oxygen (LOX) and gasoline , Liquid oxygen (LOX) and carbon monoxide.
The main difference between cryogenic and semi cryogenic engine is its fuel. Cryogenic engine has better specific impulse than semi cryogenic engine so it is ideal for upper stages of rockets. Semi-cryogenic engines offer the best thrust to weight ratios , higher density of the exhaust gases of the semi-cryogenic contribute to high mass flow rates making it easier to develop high thrust engines. So semi cryogenic engine is ideal for lower stages.
A hypergolic propellant combination used in a rocket engine is one whose components spontaneously ignite when they come into contact with each other. The two propellant components usually consist of a fuel and an oxidizer. Although commonly used hypergolic propellants are difficult to handle because of their extreme toxicity and corrosiveness, they can be stored as liquids at room temperature and hypergolic engines are easy to ignite reliably and repeatedly.
Rocket engine, where a solid fuel is combined with a liquid oxidizer or vice versa, is known as a hybrid rocket. Hybrid rockets avoid some of the disadvantages of solid rockets like the dangers of propellant handling, while also avoiding some disadvantages of liquid rockets like their mechanical complexity.
Fuselage IR radiance consist of emission by virtue of its temperature, reflected earth shine, sky shine & sun light. For a low flying aircraft, even if the rear fuselage emissivity is made zero, the air craft can still be locked on by SAM, due to the reflected earth shine in 8-12 micrometer. In the absence of earth shine, negative contrast with the background sky radiance can be used for air craft detection & lock on. Matching of fuselage IR emissions with those of the background is a high potential technique for IR camouflage. The IRSS system for fuselage can be grouped in 2 categories
AIRCRAFT SKIN HEATING/COOLING
Air craft uses a system for electrical heating of the upper portion of the fuselage for background matching. The negative IR contrast of the aircraft with respect to the surroundings is minimized there by providing IR camouflage when viewed by aircraft flying at higher altitudes. However heating is less often applicable; instead cooling of the aerodynamically heated fuselage skin especially at high mach no is more often applicable. Cooling of the skin to a temperature near the ambient air will reduce the detection range by IR imaging scanners. Heat pipe cooling & liquid evaporative cooling of aircraft skin from inside & heating/cooling of surfaces by thermo couples were patented as IRSS system. In such systems the background temperature is sensed & the aircraft skin heated/ cooled to the same temperature resulting in IR camouflage. The skin is heated or cooled using a thermo electric module that converts electrical energy into a temperature gradient. By application of voltage across the modules one side of the module becomes hot & the other side becomes cold. The temperature of the adjacent surface can be controlled by varying the applied voltage.
The aircrafts IR radiance strongly depends on the emissivity of the radiating surface; which depends on surface temperature & surface physical & chemical properties. Most methods of IRSS are associated with performance penalties e.g. Increased drag, additional weight, increased RCS; increased nozzle back pressure etc. emissivity optimization of the aircraft surface is a viable option which does not impose performance penalties. Rear fuselage emissivity optimization in the 3-5 & 8-12 band emissivity reduction from 1.0 to 0.0 reduces peak aircraft spectral lock on range by almost 100% in the 8-12 micrometer bands. It is seen that lock on range is more sensitive in 8-12 band as compared to 3-5 band. Emissivity can be optimized by physical & chemical treatment of the radiating surfaces.
SOME TECHNIQUES TO EMISSIVITY OPTIMIZATION
LIMITATIONS OF IR SUPPRESSORS
Passive IRCM’s can be incorporated on an aircraft in the initial design or modification stage or later as retrofits/additives. First gen IR suppressors were simple & aimed to provide optical blockage of hot engine parts. 2nd gen IR suppressors involve a combination of optical blockage, metal cooling & exhaust gas cooling which add more complexity to the system. The major performance penalties associated with incorporation of IR suppressors are disclosed below
ACTIVE COUNTER MEASURES
These countermeasures include IR jammers and IR flares, which serve as decoys by luring away the approaching heat seeking missile. Saturation jammers introduce large amount of IR noise into the threat’s tracking system that damages the seeker optics. Smart jammers are either non-directional or directional (DIRCM), and deceive IR trackers by sending false target information. The IR flares were used first as active countermeasures against IR seekers in the Vietnam War in the 1960s. These decoys are easy to handle, reliable, and are made of cheap constituents like metal fuels and oxidizers. To imitate the tail-pipe IR spectrum, the decoy flares fired from the rear. Busting smoke of bronze–copper-lined flakes, bronze flakes, and mixture of flakes with chaff, serve as IR decoys for longer duration .However, the new generation of imaging IR detectors can discriminate IR flare (as point source) and target, making flares ineffective as IRCM. To counter this situation, decoys driven by liquid fuels that produce as large a radiating plume as that of aircraft were proposed. Such decoys use more energetic fuels like tri-ethyl-aluminum, tri-isobutyl-aluminum, di-ethyl-aluminum, etc., which are called as pyrophoric liquids
Development of a Missile Approach Warning System (MAWS) against IR-guided missiles is a formidable task. Typical MAWS should ideally have the following characteristics:
There are three technological options available for MAWS
COUNTER COUNTER MEASURES
CCMs are counter the active and passive IRCMs. Some examples of CCM are as follows
Its an attempt from us to find the best BVR missiles in the world. Very little data is available about different missiles. We made a lot of efforts to find the data and specifications. It takes more than a month to complete this article so everyone please read the article fully & leave your valuable comment.
The criteria followed here is, incorporated technology and effectiveness in battle.
These pictures are owned by Rajat Desai. Credits be given to him , if you want to repost these pics.
This article is about to give a brief idea about propulsion and different kinds propulsive devices. Here we just cover the very basics of different propulsion. A detailed article will publish sometime later.
What is propulsion and propulsion system?
Propulsion means to push forward or drive an object forward. A propulsion system is a machine that produces thrust to push an object forward. On airplanes, thrust is usually generated through some application of Newton's third law of action and reaction. A gas, or working fluid, is accelerated by the engine, and the reaction to this acceleration produces a force on the engine.
There are hundreds of different kinds of propulsion; here we only considering some of the Rocket propulsion, air breathing propulsion & electric propulsion.
Guidance is that aspect of a missile system which helps it to decide the direction in which the missile should move. Generally this decision has to be taken at very short intervals of time (1/50th of a second) during the flight of the missile.
For a specific mission, particular guidance technique is used. The different types of guidance are
Some missiles need more than one system of guidance. The requirement depends on the phase of guidance. The various guidance phases are the launch phase, the mid-course phase and the terminal phase.
Agni-VI is an intercontinental ballistic missile under development by the DRDO for the use of the Indian Armed Forces. Agni-VI will be a four-stage intercontinental ballistic missile. Agni-6 will carry a massive three-tonne warhead, thrice the weight of the one-tonne warhead that Agni missiles have carried so far. This will allow each Agni-6 missile to launch several nuclear warheads -Multiple Independently Targetable Re-entry Warheads (MIRVs) - with each warhead striking a different target. Each warhead - called Maneuverable Reentry Vehicle (MARV) - performs evasive maneuvers while hurtling down towards its target, confusing enemy air defence missiles that are trying to destroy them mid-air. And these maneuverable warheads will give Agni VI an extended range exact figure of which is currently classified. It will be taller than its predecessor Agni V, and is expected to be flight tested by 2017. Agni-VI missile is likely to carry up to 10 MIRV warheads and will have a strike range of 8,000 km to 12,000 km.
Guidance system of Agni 6 will include inertial navigation system with Ring laser gyroscope, optionally augmented by IRNSS. Terminal guidance with possible radar scene correlation (this is a kind of terrain contour mapping this improves the accuracy of missiles).
INFRARED COUNTER MEASUERS (IRCM)
IRCM can be classified into two categories passive (termed as IR suppression) & Active (Eg; decoys)
PASSIVE-(IR suppressors /Optimizers) – Minimizes the signature from aircraft
ACTIVE-(IR flares, IR jammers, Pyrotechnic IR Decoys (IR lamp on sacrificial structures)) –Confuses the IR seeker by IR jamming, Luring away towards fake target / sacrificial structure
Aircraft / Helicopters equipped with IR counter measures is not necessarily immune to attacks by IR guided missiles as counter counter measures (CCM)are also being currently developed
AMCA or the Advanced Medium Combat Aircraft is a fifth-generation fighter aircraft which will be manufactured by HAL. The AMCA programme is envisaged as replacement for a host of aircraft currently operated by the IAF as well as to fill gaps left by retirement of the Dassault Mirage 2000s, SEPECAT Jaguars and Mig-27s.ADA describes the AMCA as a "multirole combat aircraft for air superiority, point air defense, deep penetration/strike, special missions".
Unofficial design work on the AMCA started in 2008 with official work started in 2011 and completed in 2014. In 2008 Indian Navy also showed interest in the naval variant of AMCA. All the design work is completed and ADA is waiting for the approval of Indian government to develop the first prototype.
The broad requirements outlined for the AMCA are to incorporate a high degree of stealth, a high internal and external weapons payload, high internal fuel capacity, and the ability to swing from an air-to-air role to air-to-ground. It is also expected to have the ability to super cruise. This allows the aircraft to travel at supersonic speeds with greater endurance as the afterburners do not have to be used with the additional fuel usage. Even though future air combat has been envisaged as being beyond visual range excluding the likelihood of aerial dogfights as before, the AMCA is expected to sport a thrust vectoring engine. The ADA is designed the AMCA as a platform with high survivability, to meet the challenges of future air defense environments through a combination of moderate stealth, electronic warfare capability, sensors and kinetic performance. The design philosophy seeks to balance aerodynamics and stealth capabilities.
The aircraft will have a weight of 16-18 tons. 16-18 tons with 2-tons of internal weapons and 4-tons of internal fuel. Combat ceiling will be 15-km, max speed of 1.8-Mach at 11-km. The AMCA will be powered by 2 x 90KN engines with vectored nozzles.
The IRST ( infrared search and track) is a device used to detect targets. The IRST pics uo heat signals from a target. Heat is transferred in three modes, namely conduction, convection and radiation. The heat getting transferred via radiation to the surrounding us picked up by the IRST sensor. For ex. The F 22 Raptor when flying at it's normal cruising speeds emit hot gases from it's engine of the tempreture around 800° C. This much heat is enough to detect Raptor and engage it with a heat seeking missile. There are a large number of Four plus generation aircrafts that have IRST devices. QWIP IRST is the latest.
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ENGINE & REAL FUSELAGE IR SIGNATURE
The aircraft rear fuselage has a large surface area at relatively low temperature, which is primarily heated by the embedded power plant & external aerodynamic heating. Earth shine & sky shine reflections add to the IR emissions from the rear fuselage & become especially important in 8-12 micrometer band for low surface emissivities. The engine casing & nozzle act as grey bodies & emit radiation in all IR bands there by making IR detection easier. After burner flames further enhances IR emissions from the power plant due to much higher temperatures of chemically reacting species & the glowing carbon particles. After burning significantly increases the rear fuselage skin temperature & the temperature of the jet pipe almost doubles while the rear fuselage temperature almost increases by about 70K. Apart from the hot combustion products in the power plant, aerodynamic heating also has significant effect on the rear fuselage skin temp.
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