Study of a thermal drill head for the exploration of subsurface planetary ice layers

The recently discovered water vapor plumes on Saturn's moon Enceladus, the polar caps of planet Mars and the possible ice volcanism on the Jovian satellites call for suitable techniques to explore deep ice layers of the solar system bodies. This paper presents a novel approach to deliver scientific probes into deeper layers of planetary ice. Several existing locomotion concepts and techniques for such probes are presented. After studying the mathematical framework of the melting locomotion process, melting tests with different head forms were done to evaluate the influence of the head's geometry on the melting process. This work led to a novel concept of a thermal drill head, using heat and mechanical drill in combination to penetrate the ice. We compare the performance of such a hybrid concept versus the melting penetration alone by a mathematical model and tests in ice with a prototype of the melting drill head.     

Applying the circuit theory to the development of an algorithm for designing the pneumohydraulic system of a spacecraft powertrain

This article considers the application of circuit theory methods for developing a mathematical model of the branched pneumohydraulic system (PHS) of a spacecraft powertrain (PT). The parts of the PHS are treated as elements with lumped constants. The design principles are defined. The methodology for developing a mathematical model for the PHS is described.     

Modeling the Comet Nucleus Interior

Numerical simulation of the structure and evolution of a comet nucleus is reviewed both from the mathematical and from the physical point of view. Various mathematical procedures and approximations are discussed, and different attempts to model the physical characteristics of cometary material, such as thermal conductivity, or permeability to gas flow, are described. The evolution and activity of comets is shown to depend on different classes of parameters: Defining parameters, such as size and orbit, structural parameters, such as porosity and composition, and initial parameters, such as temperature and live radio isotope content. The latter are related to the formation of comets. Despite the large number of parameters, general conclusions, or common features, appear to emerge from the numerous model calculations — for different comets — performed to date. Thus, the stratified structure of comet nuclei, volatile depletion, and the role of crystallization of ice in cometary outbursts are discussed. Finally, an evolution model applied to comet C/1995 O1 Hale-Bopp — using different assumptions — is described and analysed in the light of observations.     

Design principles of descent vehicles with an inflatable braking device

A new type of descent vehicle (DVs) is described: a descent vehicle with an inflatable braking device (IBD DV). IBD development issues, as well as materials needed for the design, manufacturing, and testing of an IBD and its thermal protection, are discussed. A list is given of Russian integrated test facilities intended for testing IBD DVs. Progress is described in the development of IBD DVs in Russia and abroad.     

Distribution of minor constituents in a thermal interface

A non-steady, two-dimensional, compressible mathematical model of a fluid with constant viscosity and thermal conductivity is given in order to represent a thin atmospheric layer located at 60 km height, as a function of a known initial vertical distribution of temperature, chemical concentrations of minor components and assumed free boundary conditions.The purpose of this paper is to determine the influence of convective laminar processes in the vertical distribution of minor constituents in a thermal interface. Only three minor components are considered, atomic oxygen, molecular oxygen and ozone. Numerical solutions of the stated timedependent convection problem for different Rayleigh numbers show a marked influence of the established flow pattern upon the distribution of minor constituents. In all cases, an enhancement of mean concentration gradients in relatively small regions adjacent to the warmer and colder boundaries was observed.     

Developing Diagnostic Tools for X-Wind Jets

Here we outline the development of a diagnostic tool for probing the jet phenomena from YSOs. We adopt the X-wind model for jets and winds as our background framework. We review the basic dynamical model, the crucial physics that affects the thermal structure and excitation condition of such flows, and interpretation and predictions of radiation based on such approaches. We also suggest possible diagnostics suitable for probing physical conditions that arise in YSO jets.     

Revised model calculations for the thermal histories of ordinary chondrite parent bodies

Abstract— Recent measurements of ordinary chondrite physical and thermal properties along with new geothermometry studies have provided the necessary parameters for updating a previously proposed model (Miyamoto et al., 1981) for the thermal evolution and internal structure of ordinary chondrite parent bodies. Model calculations assumed a heat source term derived from the decay of ²⁶Al (justification is provided). Differences from the previous model include: varying the thermal diffusivity parameter with increasing temperature (and decreasing porosity), using variable physical and thermal parameters to provide end member models, and incorporating a shortened thermal history of 60 Ma (obtained from new Pb-Pb chronology of phosphates) rather than 100 Ma. Times of isotopic closure in chondrite phosphates overlap the thermal model estimates, and postmetamorphic cooling rates from the model approximately coincide, in both trend and magnitude, with metallographic and fission track cooling rate data. Model calculations attempt to match peak metamorphic conditions in the central portions of these bodies and yield accretion ages between 1.4 to 3.1 Ma after calcium-aluminum inclusion (CAI) formation. Model calculations also predict that both the H and the L chondrite parent asteroids consisted of ～80% equilibrated and 20% unequilibrated chondritic material and that their original radii ranged from 80 to 95 km.     

Thermal effect on the pulses of the rotating Sun

In this paper, a theoretical investigation is undertaken of the group travel-time for the Sun's pulses to travel from the source of the pulse to the solar surface. For mathematical simplicity, we consider a simple ionized model of the Sun that includes the thermal effect and rotation with uniform angular velocity. The expression for the group travel time gives two terms: the term arising from the linear theory which varies inversely to (2-)^1/2 and the term introduced by the thermal effect which is inversely proportional to (2-)^7/2. The thermal effect variation has been shown and an estimation of the temperature of the medium has been made. Furthermore, the velocity distribution and the amplitude of the magnetic field of the wave, arising from the damping of ionized particles, have been calculated.     

A comparison study between the newly-born ion effect and the thermal effect on the whistlers in the ionosphere

We have considered an ionospheric plasma model that includes the thermal effect along with the newly born ionic effect and derived a group travel time for the low-frequency whistlers with a view to employing it as a diagnostic tool in the ionosphere. The mathematical development shows that the thermal effect contribution varies with ( _i – )_–7/2 whereas that of the newly born ionic effect varies with _i – )_–5/2. Both the effects are discussed separately. It is concluded that the effects are reasonably countable in the ionosphere. The investigations finally conclude that both the effects should be taken into the whistler waves, otherwise the method might cause a discrepancy in the results, which could affect their accuracy.     

Characteristics of damping of the pulses in the Sun

This paper is a sequel to our earlier paper on the mathematical modelling in determining the rotational frequency and the density of an ionized medium. The technique is based on the measurement of the group travel time for a wave propagating in a rotating ionized medium and finally a simple approximate formula determines the rotation and the density of the medium. The present paper calculates the damping of the pulse-waves in the rotating Sun and leads to a mathematical development to estimate more physical parameters of the solar system.     

Infrared studies of the lunar terrain

This paper presents an infrared study of thermal anomalies during the lunar night. From observations of the most intense anomalies at several wavelengths it is deduced that fields of boulders are responsible for the thermal enhancement; the cooling curves of the remainder are consistent with such a model. High resolution Lunar Orbiter photographs of some of the thermal anomalies reveal boulders to be present within them in just the right numbers. The ages and distribution of thermal anomalies are discussed in the light of this model.     

斜轴式望远镜动力学建模与鲁棒控制

斜轴式望远镜是一种新颖的望远镜结构, 其独特的结构设计更适合南极等极端气候环境, 但目前国内外缺乏针对斜轴式望远镜详细的动力学建模与控制研究. 提出一套斜轴式望远镜动力学建模与鲁棒控制方法, 首先, 对斜轴式望远镜进行了动力学分析, 采用拉格朗日法建立望远镜2自由度刚体模型; 接着, 结合望远镜驱动系统的柔性和所受干扰, 完成了斜轴式望远镜的干扰情况下刚柔耦合系统数学模型的推导; 然后, 针对抗干扰问题, 根据所建数学模型, 设计了基于干扰观测器的滑模控制器, 对于所受干扰进行抑制, 实现了斜轴式望远镜的鲁棒控制; 最后, 仿真结果显示, 在考虑模型的非线性外部干扰的情况下, 相比于传统的比例-积分-微分控制器, 基于干扰观测器的滑模控制器使得系统具有更好的动态性能和抗干扰特性.     

Relativistic gravitational collapse of a cool white dwarf with allowance for the neutronization kinetics

We consider and numerically solve the problem of the relativistic gravitational collapse of a spherically symmetric cool nonrotating white dwarf with allowance for the neutronization kinetics. We propose a model equation of state and analyze the neutronization kinetics under simplifying assumptions. A comprehensive mathematical model is constructed for the phenomenon. The system of equations is integrated numerically. The gravitational collapse of a white dwarf that lost its stability is shown to lead to the envelope ejection and to the final state of a hot static neutron star. For comparison, we solve the problem with an equilibrium equation of state. We show that in this case, the entire mass ultimately goes under the gravitational radius to form a black hole.     

Artificial electron clouds—VI Low altitude study, release of cesium at 69, 82 and 91 km

There is reported a series of three artificial electron clouds created at Holloman Air Force Base, New Mexico at 69, 82 and 91 km in May 1958 by the day-time thermo-chemical release of cesium. The electron cloud was created by both thermal and photo-ionization. A lower limit for the effective duration of electron clouds for this kind of release was found to be 70 km. The short duration at low altitudes is caused by both the rapid chemical consumption of the cesium atoms thereby preventing photo-ionization and the rapid electron attachment followed by mutual neutralization. The coefficient of mutual neutralization is estimated to be 10⁻⁷−10⁻⁸ cm³ sec⁻¹. The mathematical model employed appears to be reasonably valid.     

Rushing to equilibrium: a simple model for the collisional evolution of asteroids

A simple mathematical model for the evolution of a system of collisionally interacting bodies—such as the asteroid population—consists of two coupled, nonlinear, first-order differential equations for the abundances of “small” and “big” bodies. The model easily allows us to recover Dohnanyi's value for the exponent of the equilibrium mass distribution. Moreover, the model shows that any initial value for the ratio of “big” to “small” bodies rapidly relaxes to the equilibrium ratio, corresponding to the exponent, and that integrating the evolution equations backward in time—an attractive possibility to investigate the mass distribution of primordial planetesimals—leads to strong numerical instability.     

Latitudinal gradients in the electron temperature of the lower F-region at mid- to low latitudes

In this paper we present the results of a study of the thermal balance of the lower F-region at mid- to low latitudes. By using a mathematical model with input data based on in situ measurements along AE-C orbits 457, 666 and 677 (26 January, 1974, 14 February, 1974 and 15 February, 1974, respectively) we demonstrate that electron heat conduction along the magnetic field lines has to be included in the model if good agreement between the calculated and observed electron temperatures is to be achieved. This gives support to the suggestion made by Hoegy and Brace (1978), that the discrepancy in the shape of the electron heating and electron cooling rate distributions reported by Brace et al. (1976) resulted mainly from neglecting heat conduction in the electron gas. In addition, our results indicate that the currently used plasma heating and plasma cooling rates and the photoelectron heating rates calculated by Brace et al. (1976) for the orbits used in this study are consistent with the AE-C in situ measurements.     

Numerical modeling of impact heating and cooling of the Vredefort impact structure

Abstract— Large meteorite impacts, such as the one that created the Vredefort structure in South Africa?2 Ga ago, result in significant heating of the target. The temperatures achieved in these events have important implications for post‐impact metamorphism as well as for the development of hydrothermal systems. To investigate the post‐impact thermal evolution and the size of the Vredefort structure, we have analyzed impact‐induced shock heating in numerical simulations of terrestrial impacts by projectiles of a range of sizes thought to be appropriate for creating the Vredefort structure. When compared with the extent of estimated thermal shock metamorphism observed at different locations around Vredefort, our model results support our earlier estimates that the original crater was 120–160 km in diameter, based on comparison of predicted to observed locations of shock features. The simulations demonstrate that only limited shock heating of the target occurs outside the final crater and that the cooling time was at least 0.3 Myr but no more than 30 Myr.     

Quasi-linear model for the plasma mechanism of narrow-band microwave burst generation

Characteristic features of the plasma model for radio emission from the extending fronts of solar flare energy release are studied. It is shown that the electron distribution is formed near the thermal fronts as stationary beam injection through the boundary into the cold plasma semi-space. A principal new result is a conclusion about the localization of a plasma turbulence region — the source of emission in a narrow layer before the thermal front, that makes it possible to explain the burst narrow-band feature in a natural way. Wide capabilities of the flare loop structure analysis using the narrow-band emission parameters are demonstrated.