Monte Carlo scattering of sunlight by high altitude rocket plumes

A comprehensive model for the scattering of sunlight by high altitude rocket plumes is presented. The model consists of a Monte Carlo simulation of the multiple absorption-emission of solar photons by plume molecules. The physical and optical properties of high altitude plumes are discussed. It is shown that the expansion of rocket exhaust gases into a vacuum produces a highly nonequilibrium distribution of quantum state populations. As an example, the terminal translational and rotational temperatures for CO₂, for a 1 kN thrust engine, are predicted to be 10 and 15 K, respectively. Because these very low rotational temperatures result in a molecular absorption spectrum which consists of only several rotational lines, the optical opacity of both i.r. and u.v. transitions can be of order unity at large distances from the nozzle exit. For a 1 kN thrust engine, the centerline optical diameter equals unity at axial distances of approx. 10 m for CO₂ (4.3 μm) and 100m for CO (2,0) A → X. Detailed Monte Carlo calculations are presented for i.r. [CO₂(4.3 μm), H₂O (2.7 μm), and CO (4.6 μm)] and u.v. [H Lyα and CO A → X, B → X, C → X] transitions which demonstrate the dependence of scattered solar power on engine thrust, plume length and solar illumination angle. In general, plumes characterized by thrusts greater than 10 kN and lengths less than 0.1 km are optically opaque for i.r. transitions. However, u.v. transitions for H Lyα are quite optically thick even for a thrust as small as 1 kN and a plume length of 1 km. The u.v. transitions for CO can be optically opaque for 1 kN thrust and a plume length less than 1 km.     

Core noise from gas turbine exhausts

There is abundant evidence to show that the exhaust noise from gas turbines contains components which exceed the jet mixing noise at low jet velocities. This paper describes results of a theory developed to calculate the acoustic power produced by temperature fluctuations from the combustor entering the turbine. With the turbine Mach numbers and flow directions at blade mid-height, and a typical value for the fluctuation in temperature, as parameters it has been possible to predict the acoustic power due to this mechanism for three different engines. In all three cases the agreement with measurements of acoustic power at low jet velocities is very good. Similarly, based on a measured spectrum of the temperature fluctuation, the prediction of the acoustic power spectrum agrees quite well with that measured.     

Characteristics of target interaction with high power UV laser radiation

Thermal conduction, mass ablation rate, pressure and preheat were investigated in the interaction of a frequency tripled Nd: glass laser of power 0.-0.2 TW with flat targets. In the range $\text{10}{}^{13}\text{?10}{}^{15}\text{W}\text{cm}{}^2$ for 400 ps pulses we find: (a) thermal conduction may be described by a flux limiter f = 0.04 ± 0.01; (b) the mass abaltion rate depends on the incident laser irradiance as $\text{m}\text{?}\text{= 4.4 × 10}{}^5\text{(I/10}{}^{14}\text{)}{}^{0.53}\text{g cm}{}^{-2}\text{s}{}^{-1}$; (c) the pressure near the ablation surface increases approximately linearly with irradiance and is about 70 Mbar at 10¹⁵ W/cm², and (d) preheat as evidenced by K_α X-ray line emission is significantly lower than in λ = 1.05 μm irradiation.     

高空核爆炸形成人工辐射带的数值模拟

基于Stmer关于带电粒子在地球磁场中运动的理论模型,分析得出高能电子在地球周围的运动区域.结合高空核爆形成放射性烟云的经验模型,推断高空核爆在地球周围形成人工辐射带的基本区域.进而利用高空核爆裂变特性和辐射带中高能粒子的分布特性,计算得到高空核爆形成人工辐射带的电子密度通量,并对高空核爆激发的人工辐射带特征与核爆炸的爆点纬度、高度及当量之间的关系作了初步的定量分析.数值模拟结果表明,在一定的条件下,0.1—1Mt TNT当量的高空核爆,预计在地球周围可形成电子通量密度比自然辐射带高3—4个量级的人工辐射带.形成的人工辐射带中心位置主要受核爆爆点地磁纬度的影响,核爆的爆高和核爆的当量则对人工辐射带的厚度及其中高能电子的通量密度有一定的影响. 关键词： 高空核爆 人工辐射带 高能电子通量 爆炸当量     

Intense Cherenkov-type terahertz electromagnetic radiation from ultrafast laser-plasma interaction

A Cherenkov-type terahertz electromagnetic radiation is revealed, which results efficiently from the collective effects in the time-domain of ultrafast pulsed electron current produced by ultrafast intense laser--plasma interaction. The emitted pulse waveform and spectrum, and the dependence of laser pulse parameters on the structure of the radiation field are investigated numerically. The condition of THz radiation generation in this regime and Cherenkov geometry of the radiation field are studied analytically.     

Measurements of broad-band millimeter-wave radiation from anIREB-plasma interaction system

High-power broad-band millimeter-wave radiation is emitted from a plasma in a strong Langmuir turbulence state driven by an intense relativistic electron beam. We measured directivity and spectrum of this radiation with a filter-bank spectrometer, a heterodyne spectrometer, and a filter-waveguide-combination spectrometer covering 18-140 GHz. The directivity measurement indicated that the radiation was relativistically beamed. The observed spectra were nearly flat up to about 40 GHz and declined steeply above 40 GHz. Discussion is given on the experimental results in connection with the collective Compton boosting model proposed by Benford and Weatherall (1992)     

Determination of 3,4-benzpyrene in diesel exhausts from fluorescence spectra

Fluorescence in frozen solutions is applied to quantitative analysis of 3, 4-benzpyrene in diesel exhausts; the amount is found to be related to the operating conditions.     

Conversion of electrostatic field of atmosphere to ELF radiation of launched rocket

Conversion of the atmosphere's electrostatic field to the ELF radiation of a launched rocket is examined. An ELF field is produced by natural or artificial changes in the length of the conductor formed by the rocket main body and the flame plasma in the external electrostatic field of the atmosphere. Numerical estimates of ELF fields show that they can be detected and used for studies of the altitude profile of the atmosphere's electrostatic field as well as for remote monitoring of motor operation.Radio-Astronomy Institute, Academy of Sciences of Ukraine. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 34, No. 9, pp. 975–981, September, 1991.     

孤子和辐射场的非线性相互作用

利用穿衣服的方法推导出了在纯辐射场情况下Jost函数对的显式,由此得到了孤子与辐射场相互作用的解析表达式,发现脉冲在传输过程中,由于受到辐射场的作用,其振幅的演化在传播方向上是按照幂指数的负的平方根的规律衰减,并且将最终演化成一个类孤子的形式,且阐明了因子γ对光脉冲输出的光谱特性将会产生重要影响;并对辐射场的存在对类孤子演化的动力学行为作了分析. 关键词： 穿衣服方法 类孤子 孤子 辐射场     

Inter-particle interaction induced by broadband radiation

The recent fabrication of optical traps using super-continuum light impresses the need for a theory of inter-particle interactions under such conditions. Development of the theory provides a basis for calculation of the observations expected under experimental conditions. An expression for the inter-particle potential energy induced by continuum states of light is first derived using quantum electrodynamics. This energy expression is cast as a function of the spectral irradiance of the light, and the electric susceptibility of the interacting particles. Specific results are derived for light with a Lorentzian spectrum. It is shown that by filtering part of the spectrum, it is possible to exert control over the length of linear particle chains organized along the Poynting vector. The results exhibit scope for the optical fabrication of moldable structures using broadband light.     

HF/DF激光传输的大气衰减特性

 大气中的水汽对DF激光主要强线的吸收相对较小，而HF激光的大多数谱线受水汽和CO₂分子等的吸收较大。利用较新的HITRAN96数据库和我国不同地区的气象资料，采用逐线积分法计算了HF/DF 激光的大气衰减情况。所选的谱线中，在合肥地区（年平均）， HF的水汽吸收系数最大值可达到10km^-1的数量级，二氧化碳吸收系数最大可达10^-4~10^-3km^-1量级，P2(8)线吸收最弱；DF激光水汽吸收系数最大值可达到10^-1km^-1,比HF低2个量级，且随高度衰减很快，10km处就到10^-5~10^-4km^-1量级，P2(8)线吸收最弱。在我国，由南向北，由夏季到冬季，水汽浓度减少，大气对HF/DF激光的吸收率也相应地递减。     

HF/DF激光传输的大气衰减特性

大气中的水汽对DF激光主要强线的吸收相对较小,而HF激光的大多数谱线受水汽和CO2分子等的吸收较大。利用较新的HITRAN96数据库和我国不同地区的气象资料,采用逐线积分法计算了HF/DF 激光的大气衰减情况。所选的谱线中,在合肥地区（年平均）, HF的水汽吸收系数最大值可达到10km-1的数量级,二氧化碳吸收系数最大可达10-4~10-3km-1量级,P2(8)线吸收最弱;DF激光水汽吸收系数最大值可达到10-1km-1,比HF低2个量级,且随高度衰减很快,10km处就到10-5~10-4km-1量级,P2(8)线吸收最弱。在我国,由南向北,由夏季到冬季,水汽浓度减少,大气对HF/DF激光的吸收率也相应地递减。     

Numerical simulation of the early-time high altitude electromagnetic pulse

In this paper, the finite difference method is used to develop the Fortran software MCHII. The physical process in which the electromagnetic signal is generated by the interaction of nuclear-explosion-induced Compton currents with the geomagnetic field is numerically simulated. The electromagnetic pulse waveforms below the burst point are investigated. The effects of the height of burst, yield and the time-dependence of γ-rays are calculated by using the MCHII code. The results agree well with those obtained by using the code CHAP.     

Coupled radiation and turbulent multiphase flow in an aluminised solid propellant rocket engine

We present in this paper numerical simulations of coupled radiative transfer and turbulent flows at high temperature and pressure, typical of multiphase flows encountered in aluminised solid propellant rocket engines. The radiating medium is constituted of gases and of liquid or solid particles of oxidised aluminum. The turbulent flow of the gaseous phase is treated by using a four equation, low Reynolds number, boundary-layer-type turbulence model. The distributions of concentrations, temperatures, and temperature fluctuation variances of particles are calculated from a Lagrangian approach and a turbulence dispersion model. Thermal and mechanical non-equilibrium between the gas and different classes of particles is allowed. A locally one dimensional, iteratively based, radiative transfer solver is developed to compute wall fluxes and radiative source terms. It is shown that the thermal boundary layer attenuates significantly the radiative fluxes coming from the outer regions. Particle radiation is found to be much more important than gas radiation. Turbulent dispersion of particles in the boundary layer induces a decrease of particle concentration in the region of maximum turbulent kinetic energy, and then, decreases the attenuation effect of wall fluxes due to the boundary layer. The effects of turbulent temperature fluctuations are found to be small in the problem under consideration.     

Impact of rocket propulsion technology on the radiation risk in missions to Mars

Exposure to cosmic radiation is today acknowledged as a major obstacle to human missions to Mars. In fact, in addition to the poor knowledge on the late effects of heavy ions in the cosmic rays, simple countermeasures are apparently not available. Shielding is indeed very problematic in space, because of mass problems and the high-energy of the cosmic rays, and radio-protective drugs or dietary supplements are not effective. However, the simplest countermeasure for reducing radiation risk is to shorten the duration time, particularly the transit time to Mars, where the dose rate is higher than on the planet surface. Here we show that using nuclear electric propulsion (NEP) rockets, the transit time could be substantially reduced to a point where radiation risk could be considered acceptable even with the current uncertainty on late effects.     

用玻意耳定律测量高海拔地区的大气压强

由于海拔较高的高原地区,大气压低于福庭式水银气压计的指示范围.为此设计了用玻义耳实验仪测定大气压强的方法.该方法测得的大气压强是7.01×10<'4>Pa,与当地所对应的水的沸点与气压的关系基本一致,证明了该实验方法可行.