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.     

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.     

Time-Optimal Control of a Bounded Phase-Coordinate Process II: High-Order Systems with Multiple Control Inputs

This paper considers the problem arising from the design of an autopilot for a large booster. The motion-controlling actuators of the booster have both position and rate limits. The problem is formulated as a bounded phase-coordinate problem and analyzed by the ``backing out of the target' procedure. A method of constructing the optimal control is presented. An example of an oscillatory system with two control inputs is given, and the optimal control is expressed as an explicit time function.     

Comments on the Communication and Data Problems Associated with a Mars Trip During a Conjunction Phase

The analysis and comments presented in this paper are meant to establish the general communication parameters associated with Martian flyby probes and with lander and manned vehicles. Fundamental data transfer problems are reviewed to define comparisons and trends of tradeoffs for future studies. Selected focal points are based upon the long propagation path length, with inherent time delays, and the high noise produced by the sun. These problems are magnified because large quantities of data must be obtained to satisfy the needs of the scientific community and the curiosity of an interested public. A comparison of two communication systems is provided: the microwave spectrum and the optical spectrum, as represented by the microwaves at 2.3 GHz and the laser at 6328 ?. A method of cost effectiveness or value received from space missions (a criterion of power input for data quantity received) is also presented.     

Ground and on-orbit command and data handling architectures for the Active Rack Isolation System microgravity flight experiment

The Active Rack Isolation System [ARIS] International Space Station [ISS] Characterization Experiment, or ARIS-ICE for short, is a long duration microgravity characterization experiment aboard the ISS. The objective of the experiment is to fully characterize active microgravity performance of the first ARIS rack deployed on the ISS. Efficient ground and on-orbit command and data handling [C&DH] segments are the crux in achieving the challenging objectives of the mission. The objective of the paper is to provide an overview of the C&DH architectures developed for ARIS-ICE, with the view that these architectures may serve as a model for future ISS microgravity payloads. Both ground and on-orbit segments, and their interaction with corresponding ISS C&DH systems are presented. The heart of the on-orbit segment is the ARIS-ICE Payload On-orbit Processor, ARIS-ICE POP for short. The POP manages communication with the ISS C&DH system and other ISS subsystems and payloads, enables automation of test/data collection sequences, and provides a wide range of utilities such as efficient file downlinks/uplinks, data post-processing, data compression and data storage. The hardware and software architecture of the POP is presented and it is shown that the built-in functionality helps to dramatically streamline the efficiency of on-orbit operations. The ground segment has at its heart special ARIS-ICE Ground Support Equipment [GSE] software developed for the experiment. The software enables efficient command and file uplinks, and reconstruction and display of science telemetry packets. The GSE software architecture is discussed along with its interactions with ISS ground C&DH elements. A test sequence example is used to demonstrate the interplay between the ground and on-orbit segments.     

One year old and growing: a status report of the International Space Station and its partners.

The International Space Station (ISS), as the largest international science and engineering program in history, features unprecedented technical, cost, scheduling, managerial, and international complexity. A number of major milestones have been accomplished to date, including the construction of major elements of flight hardware, the development of operations and sustaining engineering centers, astronaut training, and eight Space Shuttle/Mir docking missions. International partner contributions and levels of participation have been baselined, and negotiations and discussions are nearing completion regarding bartering arrangements for services and new hardware. As ISS is successfully executed, it can pave the way for more inspiring cooperative achievements in the future.     

Solar particle events and the International Space Station

The high inclination orbit for the International Space Station poses a risk to astronauts on EVA during occasional periods of enhanced high energy particle flux from the sun known as Solar Particle Events. We are currently unable to predict these events within the few-hour lead time required for evasive action. Compounding the threat is the fact that station construction occurs during increasing solar activity and through the peak of the solar cycle. In this paper we present an overview of the risk, the current methods to provide forecasts of SPEs, and potential risk mitigation options.     

Control-structure interaction study of the proposed space station freedom

A relatively general formulation for studying the dynamics and control of an arbitrary spacecraft with interconnected flexible bodies has been developed accounting for transient system properties, shift in the center of mass, shear deformations, rotary inertias and geometric nonlinearities. This self-contained, comprehensive, numerical algorithm using system modes is applicable to a large class of spacecraft configurations of contemporary and future interests. Here, versatility of the approach is demonstrated through the dynamics and control studies aimed at the evolving Space Station Freedom.