Effect of variable thermal properties of the solid phase on composite solid propellant combustion

Effects of variable thermal properties (specific heat and thermal conductivity) of the solid phase on the combustion of composite solid propellants are studied analytically. Both steady and unsteady burning are considered. It is shown that the effects of variable thermal properties are small and can be accounted for by choosing proper average values of specific heat and thermal conductivity.     

Improving GPS-Based Landing System Performance using an Empirical Barometric Altimeter Confidence Bound

This paper develops an empirical confidence bound for barometric altimeter altitude errors and shows how this bound may improve the performance of GPS-based approach and landing systems. This empirical bound is developed using historical meteorological data collected at a set of geographically diverse locations over a thirty year period. The confidence bound developed is shown to provide a Gaussian overbound on altimeter altitude errors in standard atmospheric conditions between a 10-5 and 10-6 confidence level. This confidence bound is integrated into the standard methodology for analyzing the performance of GPS-based landing systems and the results of a performance trade study using the confidence bound are presented. The results show that incorporating the empirical barometric altimeter confidence bound provides an increase in the coterminous United States (CONUS) service volume for lateral precision with vertical guidance (LPV) type approaches. While this increase is approximately 2% for an L1 single-frequency GPS user, it jumps to roughly 40% for an L5 single-frequency user.     

Security Systems Research and Testing Laboratory at Edith Cowan University

The testing and evaluation of sophisticated security systems has remained in the domain of governments in national facilities and the commercial security industry through manufacturers and engineering consultants. As well, the production of testing protocols and industry standards has been developed by national organisations, professional security, and engineering bodies in the appropriate security fields. The Security Systems Research and Testing Laboratory in the School of Engineering and Mathematics at Edith Cowan University (ECU), Perth, Western Australia has commenced operations in research, testing, and evaluation of security systems. This paper wir describe the first year of operation of the Security Systems Research and Testing Laboratory, and will describe the role that testing and evaluation of security systems plays in the education and training of Security Science graduates, as well as the benefits that the Laboratory brings to the security industry through its testing programme.     

A novel resonant converter topology for DC-to-DC power supply

A class-E DC-to-DC converter with half-wave controlled current rectifier is proposed. Its output voltage is controlled by the conduction angle of the rectifier switch at constant switching frequency. Zero voltage switching for all the switches can be maintained from full load to no load. Its steady state characteristics are analyzed and the effects of the circuit parameters are studied. Some extensions of the proposed converter are also discussed. The analysis is verified by PSPICE simulation and an experimental prototype     

Near-Earth radiation model deficiencies as seen on CRRES.

The Space Radiation (SPACERAD) experiments on the Combined Release and Radiation Effects Satellite (CRRES) gathered 14 months of radiation particle data in an 18 degrees inclination orbit between 350 km and 36000 km from July 1990 to October 1991. When compared to the NASA radiation belt models AP8 and AE8, the data show the proton model (AP8) does not take into account a second belt formed after major solar flare/shock injection events, and the electron model (AE8) is misleading, at best, in calculating dose in near-Earth orbits. The second proton belt, although softer in energy than the main proton belt, can produce upsets in proton sensitive chips and would produce significant dose in satellites orbiting in it. The MeV electrons observed on CRRES show a significant particle population above 5 MeV (not in the AE8 model) which must be included in any meaningful dose predictions for satellites operating between L-shells of 1.7 and 3.0 RE.     

Cell biology of plant gravity sensing.

The debate about whether gravity sensing relies upon statoliths (amyloplasts that sediment) has intensified with recent findings of gravitropism in starchless mutants and of claims of hydrostatic gravity sensing. Starch and significant plastid sedimentation are not necessary for reduced sensing in mutant roots, but plastids might function here if there were a specialized receptor for plastid mass e.g. in the ER. Alternatively, components in addition to amyloplasts might provide mass for sensing. The nucleus is dense and its position is regulated, but no direct data exist for its role in sensing. If the weight of the protoplast functioned in sensing, why would there be specific cytological specializations favoring sedimentation rather than cell mass? Gravity has multiple effects on plants in addition to gravitropism. There may be more than one mechanism of gravity sensing.     

Solar-interplanetary circumstances associated with the major events in March and June 1991 and comparison with similar events of previous solar cycles.

The solar activity and geomagnetic storm events of March and June 1991 were associated with the appearance of an enhanced particle flux in the trapped radiation belts as discovered by the CRRES satellite observations and later measured by shuttle radiation detectors. The solar-interplanetary conditions associated with these events appear to be a major sequence of activity near the sun's central meridian generating powerful fast interplanetary shocks resulting in major perturbations to the magnetosphere. The solar-interplanetary events in 1991 are discussed and compared to similar activity in the past such as the events in February 1986, August 1972, July 1961, November 1960, and July 1959.     

Effects of heavy ions on inactivation and DNA double strand breaks in Deinococcus radiodurans R1.

Inactivation and double strand break (dsb) induction after heavy ion irradiation were studied in stationary phase cells of the highly radiation resistant bacterium Deinococcus radiodurans R1. There is evidence that the radiation sensitivity of this bacterium is nearly independent on energy in the range of up to 15 MeV/u for lighter ions (Ar). The responses to dsb induction for charged particles show direct relationship between increasing radiation dose and residual intact DNA.     

Dark matter in the outer solar system.

There are now a large number of small bodies in the outer solar system that are known to be covered with dark material. Attempts to identify that material have been thwarted by the absence of discrete absorption features in the reflection spectra of these planetesimals. An absorption at 2.2 micrometers that appeared to be present in several objects has not been confirmed by new observations. Three absorptions in the spectrum of the unusually red planetesimal 5145 Pholus are well-established, but their identity remains a mystery.     

ERA-experiment "Space Biochemistry".

The general goal of the experiment was to study the response of anhydrobiotic (metabolically dormant) microorganisms (spores of Bacillus subtilis, cells of Deinococcus radiodurans, conidia of Aspergillus species) and cellular constituents (plasmid DNA, proteins, purple membranes, amino acids, urea) to the extremely dehydrating conditions of open space, in some cases in combination with irradiation by solar UV-light. Methods of investigation included viability tests, analysis of DNA damages (strand breaks, DNA-protein cross-links) and analysis of chemical effects by spectroscopic, electrophoretic and chromatographic methods. The decrease in viability of the microorganisms was as expected from simulation experiments in the laboratory. Accordingly, it could be correlated with the increase in DNA damages. The purple membranes, amino acids and urea were not measurably effected by the dehydrating condition of open space (in the dark). Plasmid DNA, however, suffered a significant amount of strand breaks under these conditions. The response of these biomolecules to high fluences of short wavelength solar UV-light is very complex. Only a brief survey can be given in this paper. The data on the relatively good survival of some of the microorganisms call for strict observance of COSPAR Planetary Protection Regulations during interplanetary space missions.