RADAR Development

RADARDevelopment

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RADARDevelopment

Radarwas extensively used to detect enemy war planes and bombers throughthe World Wars and ever since. It has also found widespread usage inmodern airports to detect and direct planes wishing to land, andespecially in cases of blind- landing where the pilots have limiteduse of primary sight. Thus, Radar has become a revolutionary aspectof aviation, and a technology likely to find active usage for manymore decades to come1.The application of radar for military purposes, however, hasundergone more rapid evolution since the inception of radar, to thedeclaration of inefficiency of basic radar technologies as anintruder detection system during the rise of stealth technology2.Thousands of enemy aircraft were felled through radar guidance in thelong history of military warfare, but the introduction of radardetection avoidance, such as through the wave dispersion techniquesused by the US B2 Spirit has made radar efficiency very low or zero.This paper will explore the development, usage and the decline ofradar as an essential tool in the modern military

Conceptof Radar

Radaris basically a technology that uses radio waves to detect objects inspace within the range of a transmitting device. Most types of waveshave the property that they can be reflected off the surfaces ofobjects, in paths that obey the law of reflection such that the anglethat the incoming wave forms with a general tangent of the reflectingsurface is equal to the angle that the reflected wave also forms withthe same tangent in the opposite side of the normal line, and on thesame plane. Radio waves are in the lower half of the electromagneticwave spectrum, but other parts of the spectrum such as visible light,X-Rays, TV waves VHF and UHF spectra are also subject reflection, butall to within different levels. The traditional sense of radarapplies waves in the radio range of frequencies3.The reason for the exclusive use of radio waves is due to theirinherent property of lower attenuation by weather factors, air orother medium density, among other agents of scattering. This is incontrast to other portions of the spectrum such as visible light,infra-red and ultra violet, all of which are relatively more easilyscattered by non intended targets such as mist, fog, atmosphericdust, and rain- which in most military operations are not intended astargets.

Inoperation, a powerful transmitter (in the range of 30KW) casts apowerful beam of radiation into the space in the radar’s range. Most radar systems scan a circular or spherical region in 360degrees. Initial radar designs developed in the early and mid 20thcentury typically broadcast at 30KW and used wavelengths comparablein size to their most frequent targets, such as big fighters andbombers4.Once the radio beam hit the target, a considerable amount wasreflected back to the transmitter, whereby the size and distance ofthe object was determined by the amount of reflected radiation andthe time taken to re-capture the radiation so broadcast5.Poor selection of broadcast wavelength, as well as atmosphericattenuation and poor equipment, led to reception of very poorlydetailed reflected beams. The result was reflected waves that werescattered and vague, thereby giving only the most general guidance asto the presence and estimated location of targets in space.

Inaddition, little capability to detect and differentiate object motionwas available. As a result, extremely limited action was preciselypossible, and numerous misguided counter attack instances werelogged. Towards the latter half of the 20thcentury, more precise radar modifications were possible and shorterwavelengths typically the sizes of large birds were used. This meantthat objects within space were easier to map and identify. Typicalbombers ranged between 10-50 meters, while civilian aircraft weremostly larger, and other objects such as birds were less than a meterin length.

Inaddition to detecting the presence, possible identity, and theposition of intruders, the newer, more advanced systems alsoincorporated intelligent systems to determine the direction and speedof movement of intruders. To accomplish this, systems used DopplerEffect, or wave round-time differential or both. Using Doppler Effectrelies on the property that the frequency of a wave will tend tobecome higher if the emitter is moving towards an observer or tend tobecome lower if the emitter is moving away. Thus, an intelligentcounter in the radar system would pick up the rate at which thefrequency was changing and calculate the rate of motion of the objectaccordingly. The same calculations obtained from comparing thedifference in time of arrival of two successive signals that arereflected by the object are equally accurate6.

Actingon these projections, it was also possible to determine the manner inwhich to counter an attacker, many times to within very accuratedimensions. Radar was not only used in the airfield, but was alsoextensively used in other areas such as the marine security forces.In this use, submarines and vessel carriers were equipped with radarto scan the waters to within hundreds of kilometers for possibleintrusion. These systems were tuned to detect not just large vessels,but also smaller objects such as torpedoes fired towards the vessel.Weather radar and radar astronomy were other applications of radartechnologies. Radar altimeters were also designed to determine thealtitude of aircraft by ground control towers, an importantpossession in events where pilots were to be blind-landed by airtraffic controllers, or where a pilot’s onboard altimeter failedand they had to rely on control directions.

Historyof Usage

Radarwas developed mainly in the 1920-1930 period when two researchers,Leo Young and Hoyt Taylor, experimenting for the US Navy, noted thatwaves passing between a transmitter and receiver tended to fade outwhen an obstacle was in the direct line between them. As such, thetwo researchers recommended the possibility of use of this fadepattern to discover objects not directly visible as long as theirabsorption was low. This speculation was especially important fordetection of ships during bad weather. In the decade, numerousresearchers experimented with different materials in the atmosphere,including fog, mist, the ionosphere, aircraft, birds and otherobjects in space in order to come up with a usability report forradar signals.

Beforethe Second World War, most developed countries today including theUS, UK, France, Germany, Soviet Union, Japan and Italy independentlyworked to model their own versions of radar. The French linerNormandie was designed using radar technology to aid in navigationduring poor visibility. In addition, a soviet engineer designed theRAPID, a system to detect aircraft intruders within 3km. however, itwas not until 1934 that a fully capable radar system was designed bythe US Naval Research Laboratory. In this system, pulse generationwas used to demonstrate radar capability to detect obstacles inspace. The US Army then developed a radar guided strobe light systemin the coastal borders. At the same time, the Great Britain andGermany were experimenting with similar pulse radar systems. Theseexperiments yielded great results, and the first fully operationalradar detection system with aircraft detection efficiency wasdesigned by Watson Watt in Great Britain, in tracking points calledChain Homes. This system was timely as by 1938, the World War II wasimminent and the Royal Air Force was in high alert. This radar systemgreatly aided Britain in the Battle of Britain7.Chain Home CH radar systems relied on strong beams that broadcast inthe entire area of focus, and separate receivers that tracked thedirection of the incoming signals. This meant that very expensiveinstallations had to be made in order for the system to work. In theinitial application, radar was almost entirely ground operated. Asdevelopment commenced, radar was also applied onboard the aircraftand used effectively to scan the airspace surrounding the aircraft.This application is still in place today. This advancement found manyuses, including early warning systems for intruder or approachingenemy aircraft, as well as weapons in pursuit of the aircraft. Italso found widespread usage in ground tower to aircraft or aircraftto tower communications, a well as in emergency land in conditions ofpoor visibility8.This application is still in use today.

StealthTechnology

Radartechnology advanced tremendously since the original invention of1935. Some of the major breakthroughs included the use of mono-pulsetechnology to concentrate the beam only in a limited portion of thetotal scan space. This breakthrough enables power saving on militaryand civil radar installations, as well as reduction of installationcosts for the units. As well, the development of this technologyenabled the combination of transmitter and receiver in one terminal,as signal floodlighting was no longer required. The detailing of thetarget was also much more efficient as the radio wavelengths usedwere now variable9.

Inthe 1970s, however, the results of numerous researches made itpossible to significantly avoid detection by radar systems. One suchtechnology was development of stealth. Already, German aircraft inthe First World War attempted detection avoidance by applyingCellulose Acetate. Even though at the time radar was not commerciallyused, the issue of sight detection avoidance was a key research area.Before 1945, when radar was already in use, Germany attempted onceagain to avoid radar detection. The development of H Ho Flying Wing229 towards the end of the war was the most successful attempt todefeat radar, and possibly successful too. The German authorities haddiscovered that avoiding radar would be possible only through eitherabsorbing all or most of the radiation incident on the aircraft, orby avoiding the entire scan space of radar signals. As the later wasnot possible, they focused on absorption capability. The Ho 229 wascovered with carbon lining, and, as later experiments proved, theaircraft would not have been detected at low altitude (50-100 ft) andhigh speed (900Km/h) to CH scanners in Britain.

In1970, true radar stealth was developed independently by variousscientists and researchers over the world. Lockheed employee DenysOverholser developed a formula of facet alignment on the body of anaircraft that would aid in radar signature distortion beyondauthenticable levels. Thus, radiation falling on a body is dispersedtoo much that the amount returning to the radar receiver is solittle. Heat signature distortion was also possible. The mostsuccessful project to beat radar was the US military B-2 Spiritdevelopment, even though other successful aircraft such as the F-117and F-22 are stealth capable. The development of the aircraft bomberwas initiated in 1970s by the Northrop Company. The aircraft has amultifaceted body which is flattened and made of heat dispersing bodyto hide the craft’s heat signature. The multiple facets enabledispersion of radar beams so effectively that radar is completelyunable to detect it. These developments were the dusk days of theradar as initially conceptualized. Radar is still a very key elementof today’s military world. The section below highlights some commonapplications of radar today

Radarin Military World Today

Radaris still in widespread primary operation today. The first and perhapsfundamental application of radar in military is still for targetdetection. Overall, only a very small percentage of military vesselsare stealth efficient. Thus, for the basic military operations, radarstill provides security against the larger percentage of possibleattacks or boundary intrusions. Radar is in use in airspace, land andwater intrusion detection systems, and still delivers excellentdependability. Only a limited number of countries have stealthweaponry10.

Theother application of radar in the military is in aircraft navigationsystems. This application is common even for non-military operators.Pilots basically rely on radar to detect objects in their airfieldwith good dependability. It can help avoid collisions with otheraircraft or objects in space, or even crashing on the ground. Theground towers use radar to communicate with pilots, while pilots canalso use them to map the airport’s topology11.

Radaris also used in the military guided weaponry. Heat seeking missilesapply radar integrated technology to seek targets. On the oppositehand, radar capability is also efficient in detecting missilesincoming towards a vessel or aircraft, and therefore helps incountering this attack. Radar guns are also in use in monitoringapproach speeds of objects such as at border patrol points. Therefore, radar continues to be a major necessity in the militaryapplications today, despite the fact that its applications arelimited in conditions of stealth enabled weaponry.

Bibliography

KellerJohn. Radartechnology looks to the future.2008. Available athttp://www.militaryaerospace.com/articles/print/volume-19/issue-6/features/special-report/radar-technology-looks-to-the-future.html

Pickering, W. Radar-MilitaryWeapon or Civilian Lifesaver?2012. Available athttp://calteches.library.caltech.edu/119/1/Pickering.pdf

RaemerHarold R. RadarSystems Principles.CRC Press, 1996

Watson,Raymond C. RadarOrigins Worldwide: History of Its Evolution in 13 Nations ThroughWorld War II.Trafford Publishing. 2009.

1 Keller John. Radar technology looks to the future. 2008 p. 1

2 Ibid

3 Pickering , W. Radar-Military Weapon or Civilian Lifesaver? 2012

4 Keller p. 1

5 Raemer Harold R. Radar Systems Principles. CRC Press, 1996 p. 4

6 Ibid

7 Ibid

8 Watson, Raymond C. Radar Origins Worldwide: History of Its Evolution in 13 Nations Through World War II. Trafford Publishing. 2009. P. 5

9 Watson, Raymond C. Radar Origins Worldwide: History of Its Evolution in 13 Nations Through World War II. Trafford Publishing. 2009. P. 6

10 Keller, p. 1

11 Harold, p. 5