Wakes and differential charging of large bodies in low Earth orbit

Highlights of earlier results using the Inside-Out WAKE code on wake structures of LEO spacecraft are reviewed. For conducting bodies of radius large compared with the Debye length, a high Mach number wake develops a negative potential well. Quasineutrality is violated in the very near wake region, and the wake is relatively empty for a distance downstream of about one half of a Mach number of radii. There is also a suggestion of a core of high density along the axis. A comparison of rigorous numerical solutions with in situ wake data from the AE-C satellite suggests that the so called neutral approximation for ions (straight line trajectories, independent of fields) may be a reasonable approximation except near the center of the near wake. This approximation is adopted for very large bodies. Work concerned with the wake point potential of very large nonconducting bodies such as the shuttle orbiter is described. Using a cylindrical model for bodies of this size or larger in LEO (body radius up to 10 to the 5th power Debye lengths), approximate solutions are presented based on the neutral approximation (but with rigorous trajectory calculations for surface current balance). There is a negative potential well if the body is conducting, and no well if the body is nonconducting. In the latter case the wake surface itself becomes highly negative. The wake point potential is governed by the ion drift energy

Calculation of sheath and wake structure about a pillbox-shaped spacecraft in a flowing plasma

A computer program was used for studies of the disturbed zones around bodies in flowing plasmas, particularly spacecraft and their associated sheaths and wakes. The program solved a coupled Poisson-Vlasov system of nonlinear partial differential integral equations to obtain distributions of electric potential and ion and electron density about a finite length cylinder in a plasma flow at arbitrary ion Mach numbers. The approach was applicable to a larger range of parameters than other available approaches. In sample calculations, bodies up to 100 Debye lengths in radius were treated, that is, larger than any previously treated realistically. Applications were made to in-situ satellite experiments

Enhancing Christian School Experiences for Pre-Service Teachers through Service-Learning Partnerships

The mission of the Teacher Licensure Program at Liberty University is to develop competent professionals with a Christian worldview for Christian, public, and private schools. To be consistent with the mission, classroom experience in both Christian and public schools should be required for each teacher candidate who successfully completes Liberty’s program. One of the challenges in the implementation of the mission has been an inadequate number of field experience placements available in Christian school settings

A computer program for calculating the charge distribution about a space vehicle

Computer program for charge distribution around ionospheric space vehicl

Elderly Health and Salaries in the Mexican Labor Market

Little work exists on elderly health, work and salaries in developing countries. This paper aims to contribute to this literature in the areas of health and income of the elderly. The main purpose of this paper is to investigate the determinants of elderly health in the context of a developing country, Mexico,and the relationship between these health indicators and earnings in the labor market. We analyze the determinants of elderly health in Mexico, considering a number of different measures of health status, and we use these indicators to evaluate the impact of health on the income of working elderly individuals. We use the National Mexican Aging Survey of 1994, which contains detailed self-reported indicators of health as well as labor market information, to tease out these potential relationships. The results find that health measures have a strong negative effect on wages for male elderly workers. Our lowest point estimations demonstrate that poor health lowers hourly earnings by 58 percent. These are sizable effects, particularly within the context of a developing country, which does not have a universal social security system and may therefore imply that many elderly individuals work, whether or not their health level permits it. Poor health may also prevent others from working, and thereby contribute to high poverty rates among the elderly.

Thundercloud electrification models in atmospheric electricity and meteorology

A survey is presented of presently-available theoretical models. The models are classified into three main groups: (1) convection models, (2) precipitation models, and (3) general models. The strengths and weaknesses of the models, their dimensionalities and degrees of sophistication, the nature of their inputs and outputs, and the various specific charging mechanisms treated by them, are considered. In results obtained to date, the convection models predict no significant electrification enhancement based on conductivity gradients and convection alone, with the assumed air circulation patterns. Results of the precipitation models show that the initial electrification can occur rapidly and stably through noninductive collision mechanisms involving ice, and breakdown-strength electric fields can relatively easily be achieved subsequently through the collisional-inductive mechanism. A critical difficulty of the collision mechanisms is imprecise knowledge of relaxation times versus contact times, which can easily lead to overestimates of electrification. The general model results tend to support those of the precipitation models in emphasizing the high potential effectiveness of the collisional-inductive mechanism

Computer program for afterheat temperature distribution for mobile nuclear power plant

ESATA computer program was developed to analyze thermal safety aspects of post-impacted mobile nuclear power plants. Program is written in FORTRAN 4 and designed for IBM 7094/7044 direct coupled system