The ?-particles Induced Radar Stealth

As the effective electronic equipment for long-range detection,the radar has been widely used in various fields.With the development of the radar,the stealth technology of aircrafts and other military equipment is also rapid-developed.By the different operating principle,the regular stealth technologies are divided into four parts:the shape,the radar absorbing material(RAM),the active and the passive stealth technology.In recent years,the new principles of stealth are emerging in an endless stream,in which the "plasma stealth technology" is one of the new members in the family of stealth technologies.The plasma stealth technology comes from the RAM,and compared to traditional RAM or the shape stealth technology,it possess a variety of advantages,such as wide frequency band,strong absorption,convenience and long-term use and small effect on the flight performance,even might reduce the flight resistanceThere are many methods to produce the plasma,but most of them are within the limitation of the applications.In past years,several teams had worked out the radar cross section(RCS)value of objects coated with different plasma density and distributions by their own definitions,which might result in a pronounced gap with actual application.Using the ionization effect of the charged particles induced by the radionuclide layer(RNL)is one of the effective methods,and that had been reported by some research institutions in USA,etc.According to the actual situations,this paper aims to build a unified system of the radioactive substances,the plasma and the electromagnetic waves,and then calculate the influences of plasma induced by RNL on the RCS in the conditions of different shapes,radioactivity,temperature,pressure,heights,frequencies and wave forms of the electromagnetic waves.All these could provide an analysis reference for the practical applications.This paper is divided into six chapters,in which the first two chapters are the introductions,the research model and the algorithms,and the last four chapters are the calculation results.The major conclusions of present paper are as follows1.In Chapter 3,we analysis the influence of the ?-RNL,which is coated on a plate,on the radar echoes.When the radioactivity is 10Ci/cm2,the order of the maximum electron density outside the plate could reach 1011cm-3.An empirical formula is also summarized to calculate the electron density distribution in different conditions quickly.In the backscattering regions,the RNL can effectively decrease the RCS of the plane wave and the sine modulated with Gaussian pulse(SMGP),In troposphere,the stealth effects increase with the radioactivity,the flight altitude and the incident angle.The results show that,for the plasma stealth induced by ?-RNL,the stealth effect at high altitude is better than the ones at ground,which are reported by these research institutions in USA,etc.At 10km altitude,the decrease of the RCS along the direction of the strongest reflection wave is nearly 25.5dB when the incident angle is 60° and the surface radioactivity is 10Ci/cm2.2.The RCS of metal sphere coated with ?-RNL are simulated in Chapter 4.At ground,the maximum electron density outside the sphere is about 1010-1011cm-3 at the radioactivity of 10Ci/cm2,and the value can increase with the spherical radius and the altitude.The RNL coating can decrease the sphere RCS of plane wave and the stealth effect increase with the flight altitude in troposphere.The influences on the monostatic RCS increase with the decrease of radius for the same ratios of the radii to the electromagnetic wavelength.The calculation for the sphere indicates that the maximum of the amplitude of normalized bistatic RCS can be decreased to 10.9dB at 10km altitude for the radioactivity of 10Ci/cm2,the incident wave frequency of 1GHz and the radius of 1m.For SMGP,the different radii could induce some different conclusions,but in most space angles,the stealth effect of RNL coating is significant.3.In Chapter 5,the influences of the RNL on the RCS or the scattering width(SW)of metal cylinder.The maximum electron density can increase with the radius of the cylinder or the altitude.When the direction of the incident electromagnetic wave is vertical or oblique to the center line,the stealth effect can increase with the altitude,but the increase amplitude is not obvious when the direction is parallel.At vertical incidence,the maximum decrease amplitude of bistatic SW is about 5.78dB,when the altitude is 10km,the radius of cylinder is 0.125m,the frequency of incident wave is 1GHz and the radioactivity of the RNL is 10Ci/cm2;and at oblique incidence with small incident angle,the amplitude could reach 16.5dB.The RNL coating can effectively decrease the RCS of SMGP at vertical incidence,but at parallel incidence,the stealth effects are determined by the radius,the length of the cylinder and the pulse width,the beam radius of the SMGP waves.4.In Chapter 6,an inhomogeneous distribution function(I.D.F)method is summarized to calculate the electron density distributions in plasma induced by the RNL coating on the targets with complex structure.The method can reduce the simulation time greatly.Then,we simulate the influence of the RNL on the RCS of the cone,the ellipsoid and a small-sized missile model.Overall,by the RNL coating,the stealth effect on a cone is better than that on a cylinder at parallel incidence,while the results of a ellipsoid is also better than that of a sphere,when the sphere radius is same as the minor radius of the ellipsoid.The results might illuminate the design of shape-RNL combined stealth techniques.In the research of the missile model,considering the economy,the stealth effect of the RNL coating on the warhead only can reach about 40%to 50%of the results of the full-coating,but the cost of the radioactive substance is just 14%.So the appropriate coating position of the RNL can result to a better stealth effect with high cost performance for the target with complex shape.