Human exposure to large solar particle events in space.

Whenever energetic solar protons produced by solar particle events traverse bulk matter, they undergo various nuclear and atomic collision processes which significantly alter the physical characteristics and biologically important properties of their transported radiation fields. These physical interactions and their effect on the resulting radiation field within matter are described within the context of a recently developed deterministic, coupled neutron-proton space radiation transport computer code (BRYNTRN). Using this computer code, estimates of human exposure in interplanetary space, behind nominal (2 g/cm2) and storm shelter (20 g/cm2) thicknesses of aluminum shielding, are made for the large solar proton event of August 1972. Included in these calculations are estimates of cumulative exposures to the skin, ocular lens, and bone marrow as a function of time during the event. Risk assessment in terms of absorbed dose and dose equivalent is discussed for these organs. Also presented are estimates of organ exposures for hypothetical, worst-case flare scenarios. The rate of dose equivalent accumulation places this situation in an interesting region of dose rate between the very low values of usual concern in terrestrial radiation environments and the high dose rate values prevalent in radiation therapy.     

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     

Advanced lithium ion battery charger

A lithium ion battery charger has been developed for four and eight cell batteries or multiples thereof. This charger has the advantage over those using commercial lithium ion charging chips in that the individual cells are allowed to be taper charged at their upper charging voltage rather than be cutoff when all cells of the string have reached the upper charging voltage limit. Since 30-60% of the capacity of lithium ion cells may be restored during the taper charge, this charger has a distinct benefit of fully charging lithium ion batteries by restoring all of the available capacity to all of its cells     

Modeling the Modification of the Nighttime High-Latitude F-Region by Powerful HF Radiowaves

A mathematical model of the high-latitude F-region, taking the ionospheric plasma convection into account, is used for modeling a response of the auroral F-region to irradiation by powerful high-frequency (HF) radiowaves. The model enables us to calculate the time variations in the profiles of the electron concentration, the velocity of positive ions, and the ion and electron temperatures in the part of a magnetic-flux tube moving over an artificial ionospheric heater under the action of a convective electric field. The modeling was carried out for a part of the magnetic flux tube intersecting the F-layer irradiated by the Norwegian heater at Tromsö when it is located near the midnight magnetic meridian. The calculations were made for the equinox conditions under the high solar and low geomagnetic activity. The results of our modeling show that substantial variations in the profiles of the electron temperature, the velocity of positive ions, and the electron concentration can be produced in the nighttime high-latitude F-layer due to HF heating. The perturbation caused by a 20 s rectangular pulse should exist for about 20 min at the level of the F-layer maximum. The disturbed plasma volume can leave the region irradiated by the heater and move away for over 500 km within the above-mentioned time period.     

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.     

Biogeochemical evidence of microbial activity on Mars.

We suggest a new interpretation of the data on so-called SNC meteorites and delta 13C values of the calcium carbonate minerals and organic matter discovered in them. The delta 13C value of calcite (up to 15 ppt) is accounted for by the microbial reaction CO2 + H2 ---> CH4 + H2O. Methane-forming bacteria also synthesize organic carbon (in the form of biomass) from CO2, and this process is accompanied by 12C fractionation. Therefore, the organic carbon of SNC meteorites is enriched with 12C (delta 13C as low as -35 ppt). The environmental conditions under which the calcite of SNC meteorites was formed were favorable for the activity of methanogens.     

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.     

Recent developments in micrometeoroid simulation

In the first part the state of the art of the most advanced micrometeoroid simulation techniques is reviewed. Then a new accelerator is described, which was developed jointly by the Technische Universität München and the N.A.S.A. George C. Marshall Space Flight Center. Finally the use of this new technique is indicated for basic research in fields other than astronautics.     

High-Sensitivity Quartz Accelerometer for Measurements of Small Accelerations of Spacecraft

A quartz sensor of small accelerations with a capacitive transducer is designed and produced, allowing one to measure spacecraft accelerations with a resolution of 10^–7 m/s² in the range ±10^–1 m/s². The results of calibration of the sensor by the method of inclinations are presented.     

How we will go to Mars

This article studies the efficiency of ejecting waste generated by the life support system (LSS) of a manned spacecraft to reduce initial mass on low earth orbit. The spacecraft is used for a long-duration interplanetary mission and is equipped with either a chemical or a nuclear-thermal propulsion system. For this study we simulate an optimal control problem for a given spacecraft maneuver. An impulsive approximation of the optimal interplanetary spacecraft trajectory is assumed, which allows us to reduce the general optimal control problem to hierarchic structure of 'outer' and 'inner' subproblems. This structure is analyzed using the Pontryagin's Maximum principle. Numerical results, illustrating the efficiency of waste ejection are shown for typical Earth-Mars transfer trajectories. This results confirm in theory that using a waste ejection system makes an early manned Mars mission possible without having to design and build new, advanced biological LSS.