Millimeter wave radar with clutter measurements

A portable millimeter wave test radar system, also suitable for battery operation, gives interesting possibilities for clutter recordings at hard-to-reach sites. The designed system covers all common radar frequencies from the Ka- to V-bands and enables spatial detection of targets or clutter elements within an adjustable time gate, whereby spatial clutter profiles of rain can be analyzed. The construction allows full operation with non-scanning antennas as well. This is advantageous when measuring temporal RCS variations of selected targets or surface clutter from snow dunes.     

The Fine Structure of the AKR Electromagnetic Field as Measured by the Interball-2 Satellite

The fine structure of the Auroral Kilometric Radiation (AKR) is studied using multicomponent measurements of the electric component of the electromagnetic field in the frequency band 4 kHz–1 MHz (the POLRAD experiment onboard the INTERBALL-2 satellite). Special attention is paid to the measurements near the source of the AKR: under conditions when the lower boundary of the emission range descended sufficiently low, down to the local gyrofrequency of electrons. From the analysis of the electric field structure the conclusion is drawn that the bulk of the AKR power is carried by the signal component fast variable in time and frequency (flickering component). The power of a constant component (continuum) is lower by at least an order of magnitude. During strong bursts of the AKR, the relative contribution of the flickering component increases. The spatial structure of the zone of generation has at least three characteristic scales along and across the magnetic field.     

Power anomaly effects and costs in low-voltage mobile power systems

Electric power anomalies or disturbances can disrupt the normal operation of equipment, accelerate aging, or even cause outright failures thus resulting in increased costs of maintenance and reduced system reliability. Past research on the effects caused by power anomalies has been mostly focused on industrial, commercial, or residential systems, or on power distribution equipment. A literature survey reveals that there is no comprehensive review related to low-voltage (LV) power systems and utilization equipment applicable to military combat vehicles, such as aircraft and ships. This paper summarizes the results of a new literature survey that focused on the causes, effects, and mitigation methods for power anomalies typical of LV mobile power systems. Electric power anomaly cost data collected from the literature are also presented, from which the costs of anomalies to the national defense are estimated using some simple rationales.     

Operational testing of valve regulated lead acid batteries incommercial aircraft

Valve regulated lead acid (VRLA) batteries provide electrical performance that is virtually identical to sintered plate nickel-cadmium battery systems. In addition, the VRLA batteries offer the user a no-maintenance battery and other enhanced features that make this a very desirable battery for aircraft applications. In field trials, where VRLA batteries were substituted for nickel-cadmium batteries, the VRLA provided the user with a high reliability turbine engine starting battery under a wide variety of climatic conditions     

Ground-based simulations of galactic cosmic ray fragmentation and transport.

Since mean free paths for nuclear fragmentation are of the order of the ranges of primary Galactic Cosmic Ray (GCR) nuclei, determination of the radiation field produced by successive fragmentations of nuclei in material and tissue is essential to accurate assessment of GCR radiation risk to humans on long-duration missions outside the geomagnetosphere. We describe some recent measurements made at the Bevalac of heavy ion transport through materials, with representative results and examples of how they may be applied to aspects of the space radiation problem, including efforts to devise analytical tools for predicting biological effects and for designing spacecraft shielding.     

The conceptual design of a hybrid life support system based on the evaluation and comparison of terrestrial testbeds.

This report summarizes a trade study of different options of a bioregenerative Life Support System (LSS) and a subsequent conceptual design of a hybrid LSS. The evaluation was based mainly on the terrestrial testbed projects MELISSA (ESA) and BIOS (Russia). In addition, some methods suggested by the Advanced Life Support Project (NASA) were considered. Computer models, including mass flows were established for each of the systems with the goal of closing system loops to the extent possible. In order to cope with the differences in the supported crew size and provided nutrition, all systems were scaled for supporting a crew of six for a 780 day Mars mission (180 days transport to Mars; 600 days surface period) as given in the NASA Design Reference Mission Scenario [Hoffman, S.J., Kaplan, D.L. Human exploration of Mars: the Reference Mission of the NASA Mars Exploratory Study, 1997]. All models were scaled to provide the same daily allowances, as of calories, to the crew. Equivalent System Mass (ESM) analysis was used to compare the investigated system models against each other. Following the comparison of the terrestrial systems, the system specific subsystem options for Food Supply, Solid Waste Processing, Water Management and Atmosphere Revitalization were evaluated in a separate trade study. The best subsystem technologies from the trade study were integrated into an overall design solution based on mass flow relationships. The optimized LSS is mainly a bioregenerative system, complemented by a few physico-chemical elements, with a total ESM of 18,088 kg, which is about 4 times higher than that of a pure physico-chemical LSS, as designed in an earlier study.     

Distinguished Lecturers Program

One of the general trends of the MEMS sensors business is the utilization of the technology to satisfy harsh environment requirements (temperature, shock, vibration, environment security). The conjunction of material (standard Silicon, SiC or SOI), with complex micromachining techniques and advanced assembly techniques are the key to provide robust sensors with a miniimum concession on specification. The goal of this paper is to present progress on gun hard (> 20,000 g) and wide temperature range MEMS accelerometers (-120°C to +180°C). Concrete solutions and results (out of more than 500 tested products)) will be presented and discussed in detail.     

Generating requirements for complex embedded systems using State Analysis

It has become clear that spacecraft system complexity is reaching a threshold where customary methods of control are no longer affordable or sufficiently reliable. At the heart of this problem are the conventional approaches to systems and software engineering based on subsystem-level functional decomposition, which fail to scale in the tangled web of interactions typically encountered in complex spacecraft designs. Furthermore, there is a fundamental gap between the requirements on software specified by systems engineers and the implementation of these requirements by software engineers. Software engineers must perform the translation of requirements into software code, hoping to accurately capture the systems engineer's understanding of the system behavior, which is not always explicitly specified. This gap opens up the possibility for misinterpretation of the systems engineer's intent, potentially leading to software errors. This problem is addressed by a systems engineering methodology called State Analysis, which provides a process for capturing system and software requirements in the form of explicit models. This paper describes how requirements for complex aerospace systems can be developed using State Analysis, using representative spacecraft examples.     

Synthesis of biomass and utilization of plants wastes in a physical model of biological life-support system

The paper considers problems of biosynthesis of higher plants' biomass and "biological incineration" of plant wastes in a working physical model of biological LSS. The plant wastes are "biologically incinerated" in a special heterotrophic block involving Californian worms, mushrooms and straw. The block processes plant wastes (straw, haulms) to produce soil-like substrate (SLS) on which plants (wheat, radish) are grown. Gas exchange in such a system consists of respiratory gas exchange of SLS and photosynthesis and respiration of plants. Specifics of gas exchange dynamics of high plants--SLS complex has been considered. Relationship between such a gas exchange and PAR irradiance and age of plants has been established. Nitrogen and iron were found to the first to limit plants' growth on SLS when process conditions are deranged. The SLS microflora has been found to have different kinds of ammonifying and denitrifying bacteria which is indicative of intensive transformation of nitrogen-containing compounds. The number of physiological groups of microorganisms in SLS was, on the whole, steady. As a result, organic substances--products of exchange of plants and microorganisms were not accumulated in the medium, but mineralized and assimilated by the biocenosis. Experiments showed that the developed model of a man-made ecosystem realized complete utilization of plant wastes and involved them into the intrasystem turnover.