Assessment of safety in space power wiring systems

Wiring system failures have resulted from arc propagation in the wiring harnesses of many aircraft and space vehicles. These failures occur when the insulation becomes conductive upon the initiation of an arc. In some cases, the conductive path of the carbon arc track displays a high enough resistance such that the current is limited, and therefore may be difficult to detect using conventional circuit protection. Often, such wiring failures are not simply the result of insulation failure but are due to a combination of wiring system factors. Inadequate circuit protection, unreliable system designs, and careless maintenance procedures can contribute to a wiring system failure. This paper approaches the problem with respect to the overall wiring system, in order to determine what steps can be taken to improve the reliability, maintainability, and safety of space power systems. Power system technologies, system designs, and maintenance procedures which have contributed to past wiring system failures are discussed. New technologies, design processes, and management techniques which may lead to improved wiring system safety are introduced     

The dynamics of the object potential during electron beam injection and the possibility to control it

This review of the rocket and satellite experiments on electron beam injection in the height range of the ionosphere-magnetosphere shows a variety of manifestations of the positive charge potential on the body of the injector unit or in the space charge zone.

The possibilities of compensation are considered on the basis of theoretical models taking into account the beam-plasma collective interactions. The examples of numerical modeling of the charge-discharge dynamics are provided for the APEX conditions. It is shown that changing the pulse form and rise rate (dI/dt) one can change the structure of the space charge zone i.e. try to create the strong disturbance or resonance conditions in the time interval of πω_p≤ t ≤ t_ion. From these positions, we consider the APEX facilities used to control the inflow current, the spectrum of energetic particles, the high-frequency oscillations and the spatial distribution of optical emissions in the injector vicinity with high time resolution.     

Effects of heavy ions on visual function and electrophysiology of rodents: the ALTEA-MICE project.

ALTEA-MICE will supplement the ALTEA project on astronauts and provide information on the functional visual impairment possibly induced by heavy ions during prolonged operations in microgravity. Goals of ALTEA-MICE are: (1) to investigate the effects of heavy ions on the visual system of normal and mutant mice with retinal defects; (2) to define reliable experimental conditions for space research; and (3) to develop animal models to study the physiological consequences of space travels on humans. Remotely controlled mouse setup, applied electrophysiological recording methods, remote particle monitoring, and experimental procedures were developed and tested. The project has proved feasible under laboratory-controlled conditions comparable in important aspects to those of astronauts' exposure to particle in space. Experiments are performed at the Brookhaven National Laboratories [BNL] (Upton, NY, USA) and the Gesellschaft für Schwerionenforschung mbH [GSI]/Biophysik (Darmstadt, FRG) to identify possible electrophysiological changes and/or activation of protective mechanisms in response to pulsed radiation. Offline data analyses are in progress and observations are still anecdotal. Electrophysiological changes after pulsed radiation are within the limits of spontaneous variability under anesthesia, with only indirect evidence of possible retinal/cortical responses. Immunostaining showed changes (e.g. increased expression of FGF2 protein in the outer nuclear layer) suggesting a retinal stress reaction to high-energy particles of potential relevance in space.     

Enhancement of VLF-ducts under the action of high power radio wave on the ionospheric F-region

Wave effects are discussed pointing to improvement of whistler propagation in the ionosphere illuminated by a powerful radio wave. The large scale irregularities (ducts) responsible for these effects are formed in the illuminated ionospheric region by the process of electron heating by the fields of the pump wave and excited plasma oscillations. These irregularities may also be created in the ionosphere and plasmasphere by fluxes of suprathermal electrons accelerated by the plasma turbulence in the reflection region of the pump wave.     

Telescience testbed for biomedical experiments in space morphological and physiological experiments of rat musculoskeletal system.

As the second telescience testbed experiment we were examined sophisticated processes of biomedical experiment, such as an implantation of a transmitter into the hamster's abdominal cavity, non-stressful blood sampling, large amount of blood collection, muscle extirpation and biopsy from the hamsters on February 6-8, 1990. To make clear the differences between successful results obtained by an experienced hand and by a non-experienced one, three operators were selected for three successive experimental days; an engineer who had never experienced any biological experiment, a non-biology student, who experienced on biological experiments, and a veterinary surgeon. Surgical procedures need much experiences on maneuvering and understanding of theory to shorten the elapse time. Especially for a non-experienced hand, graphic instructions were much helpful to understand and to maneuver the procedures. Continuous recordings of ECG from a operator and PIs were of an advantage to grasp an extent of the mental strain, which was compared with their reports requested after end of each experimental day. The mental strain was not related to degrees of scientific achievement, but showed faithfully difficulty of each experimental procedure. Training effects on PIs in successive experimental days were found in their instructions for the operator to let understand the procedures.     

Land Warfare

The future conflicts that our nation may have to fight are more likely to be tactical than strategic. Land warfare forces, including the related elements of Tacair, play a pivotal role in our tactical combat capabilities, as evidenced by the fact that in World War II German production of virtually all critical material was still continuing to increase until Germany was on the verge of being physically overrun. Yet, our land warfare forces have been comparatively slow to embrace new technological developments, with such equipment as the tank, the rifle, and the cannon still playing major roles. Unfortunately, those instances wherein new technology has been adopted do not present a uniformly satisfying picture. One factor potentially contributing to this has been the inherent compartmentalization and fragmentation of our land warfare RDT&E efforts, with an overview of the interrelationships between aircraft and armor, rifles and rockets, and helicopters and howitzers seldom having been attempted.     

Hardware development and tests in the GIRL project

The German Infrared Laboratory GIRL is a liquid helium-cooled telescope with four focal plane instruments dedicated to astronomical and aeronomical observations.Hardware tests were performed with a thermal model of the cryostat and other components as active phase separator, optical switches, main mirror, baffle etc.In the test phase the thermal behavior of the system was checked out in a step by step procedure. The timeline of the individual experiments and of two representative orbits were simulated by electrical heaters. Temperatures and helium flow rates for the different operation modes were measured.An outlook shows that the project phase in 1982 is dedicated to further development and tests of hardware and complete definition and specification of all GIRL systems.     

Steady-state analysis of PWM DC-to-DC regulators

A new method for steady-state analysis of pulsewidth modulation (PWM) hard-switching DC-to-DC regulators is presented. The power stage and the feedback control circuit are analyzed as two interconnected blocks. The intersection of their open-loop DC steady-state characteristics with the ramp voltage provides a guess candidate steady-state solution (CS). An iterative process is used to validate it as true steady-state solution (TS) when the bias conditions of switching devices (SDs) are fulfilled everywhere in the switching period.     

Energetic particle observations at high heliographic latitudes

Energetic particles, accelerated in shocks which were associated with recurrent fast solar wind streams, were observed in high heliographic latitudes; fifteen such steams were included in the present study. Intensity variations ranged up to four orders of magnitude. Energy spectra were typically steeper near forward shocks than near reverse shocks. Electrons were observed only lated to the reverse shocks. Composition ratios in accelerated streams resembled those observed in fast CIR's. In periods between the recurrent acceleration regions elemental abundance ratios were similar to those of the anomalous cosmic rays (ACR). The intensity of the accelerated particles declined as the latitude of ULYSSES increased, probably due to the weakening of the shocks.     

On the Mean Frequency Measurement System Using Correlation Detection

This paper is concerned with the problem of measuring the mean frequency of the power spectrum of a zero-mean, stationary, narrowband Gaussian random signal in the presence of additive Gaussian noise. Signal-to-noise ratios at the output of the mean frequency measurement system using correlation detection are analyzed in terms of input signal-to-noise ratio, input signal and noise bandwidths, and integration time. The results obtained are verified experimentally, and a comparison with a conventional zero-crossing detector is also made.