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Multiple environmental factors associated with space flight can increase the risk of infectious illness among crewmembers thereby adversely affecting crew health and mission success. Host defenses can be impaired by multiple physiological and psychological stressors including: sleep deprivation, disrupted circadian rhythms, separation from family, perceived danger, radiation exposure, and possibly also by the direct and indirect effects of microgravity. Relevant human immunological data from isolated or stressful environments including spaceflight will be reviewed. Long-duration missions should include reliable hardware which supports sophisticated immunodiagnostic capabilities. Future advances in immunology and molecular biology will continue to provide therapeutic agents and biologic response modifiers which should effectively and selectively restore immune function which has been depressed by exposure to environmental stressors.

Manned Spacecraft are equipped with an Environmental Control Subsystem which assures that an environment is provided in which the crew finds optimum conditions to work in nominal conditions. Furthermore, in case of emergency this subsystem has to assure survivable conditions for the crew. One of the most important functions of an Environmental Control and Life Support Subsystem is to control the pressure and composition of the atmosphere. The pressure of the atmosphere is influenced by temperature changes, consumption of one or more constituents of the atmosphere by crew metabolism or other thermophysical processes and by eventually occurring gas losses due to leaks or punctures of the structure. In the paper presented a simulation model is described, which allows to analyse the thermophsyical behaviour of the Atmosphere Pressure Control Section of an ECLSS under simultaneous changing boundary conditions.

Clinical-microbiological investigations are an important aspect of the crew health stabilization program. To ensure that space crews have neither active nor latent infections, clinical specimens, including throat and nasal swabs and urine samples, are collected at 10 days (L-10) and 2 days (L-2) before launch, and immediately after landing (L+0). All samples are examined for the presence of bacteria and fungi. In addition, fecal samples are collected at L-10 and examined for bacteria, fungi and parasites. This paper describes clinical-microbiological findings from 144 astronauts participating in 25 Space Shuttle missions spanning STS-26 to STS-50. The spectrum of microbiological findings from the specimens included 25 bacterial and 11 fungal species. Among the bacteria isolated most frequently were Staphylococcus aureus, Enterobacter aerogenes, Enterococcus faecalis, Escherichia coli, Proteus mirabilis and Streptococcus agalactiae.

An advanced capability for modeling multi-link mechanisms has been developed for the TRASYS (Thermal Radiation Analyzer System) program. This capability, which has been implemented as a library software routine, allows a mechanism's configuration to be automatically updated during the calculation of either thermal radiation gray-body shape factors or external heat fluxes. This allows for accurate modeling and analysis of Spacecraft mechanisms including Antenna Pointing Systems, Solar Arrays, or Robot Arms such as those contemplated for use on the Space Shuttle or Space Station Freedom.

Spacecraft which are designed for Mars exploration are exposed to different severe thermal environments. The Thermal Control Design for small Mars landers which are being developed for the MARSNET mission is described. During transfer from Earth to Mars they experience large variations of the incident solar radiation, caused by solar aspect angle variations and the decreasing solar radiation intensity. The entry phase into the Martian atmosphere is characterized by a short aerothermodynamic heating, requiring a dedicated Thermal Protection System. Arrived on the Mars surface, the landers are exposed to an extreme thermal environment with large diurnal and seasonal variations of the atmospheric temperature and the incident solar radiation. The main emphasis is put on the description of the Martian thermal environment and the Thermal Control design for the Mars operation phase.

The hyperbaric environmental control assembly (HECA) monitors and controls temperature, humidity, and CO2 levels in the Space Station Freedom airlock when the airlock is used for EVA prebreathing campouts and as a hyperbaric treatment facility. Prebreathing is required prior to extravehicular activity due to the differential between the station nominal pressure and the EVA suit pressure. Hyperbaric treatment is required in the event of decompression sickness. The HECA consists of an atmosphere recirculation circuit which provides air circulation and temperature control, and a separate CO2 and humidity control circuit. Temperature is controlled by transferring heat from the airlock to the station thermal control system through a compact heat exchanger. CO2 and humidity are removed using a dual-bed, regenerable, molecular sieve system. While one bed is adsorbing, the other bed is being desorbed by venting to space vacuum.

Complex Compounds are solid-gas sorption media with the coordinative bond (sharing one or more electrons) established between metal inorganic salt-based adsorbents and polar refrigerants, such as ammonia, sulfur dioxide, and water. Complex compounds utilize this unique bond to sorb large amounts of refrigerant in a process that is reversible and provides large temperature lifts in single-stage hardware, allowing for their application to heat pump processes under adverse conditions. This paper describes the ongoing development of a solid-vapor complex-compound prototype heat pump suitable for lunar base operation. Working conditions are 4-15°C cooling and 82-93°C heat rejection.

A model has been developed for quantitative examination of the integrated operation of a lunar base power system, employing regenerative fuel cell technology, which would lead to incorporation into a lunar base life support system. The model employs methods developed for technology and system trade studies of the Life Support System configuration for the National Aeronautics and Space Administration (NASA). This paper describes the power system and its influence on life support while comparing various technologies, including pressurized gas storage and cryogenic storage, and different operation conditions. Based on preliminary assumptions, the mass, power, and thermal requirement estimates are made at the level of major components. The relative mass contribution and energy requirements of the components in various configurations are presented.

A parametric analysis is performed to compare different heat pump based thermal control systems for a Lunar Base. Rankine cycle and absorption cycle heat pumps are compared and optimized for a 100 kW cooling load. Variables include the use or lack of an interface heat exchanger, and different operating fluids. Optimization of system mass to radiator rejection temperature is performed. The results indicate a relatively small sensitivity of Rankine cycle system mass to these variables, with optimized system masses of about 6000 kg for the 100 kW thermal load. It is quantitatively demonstrated that absorption based systems are not mass competitive with Rankine systems.

Long duration human exploration missions to the Moon will require active thermal control systems which have not previously been used in space. The relatively short duration Apollo missions were able to use expendable resources (water boiler) to handle the moderate heat rejection requirement. Future NASA missions to the Moon will require higher heat loads to be rejected for long periods of time near the lunar equator. This will include heat rejection during lunar noon when direct radiation heat transfer to the surrounding environment is impossible because the radiator views the hot lunar surface. The two technologies which are most promising for long term lunar base thermal control are heat pumps and radiator shades. Heat pumps enable heat rejection to space at the hottest part of the lunar day by raising the radiator temperature above the environment temperature.

The future deployment of a network of measurement stations on the surface of MARS is presently prepared. The MARS environment is characterised by large daily and seasonal temperature fluctuations in low density atmosphere with carbondioxide as its main constituent. Typical environmental conditions for some locations are presented. Due to geometrical and mass constraints highly efficient and reliable thermal insulations are required for the thermal control of MARS stations which are powered by solar energy. ERNO has investigated the thermal performance of two candidate porous insulations in the frame of an ESTEC technology contract. The paper presents methods to predict the heat transfer modes of both insulations in a Martian environment analytically. Experimental measurements have been performed and evaluated in order to validate the analytical predictions. Based on these results the insulation design concept is reviewed.

The stringent mass targets of the Hermes spaceplane require the design of extremely compact plate & fin heat exchangers, hence with a very low fin height, operating at low Reynolds numbers. These parameters, low Re (10-500 range) and low fin height (0.8 mm), have so far been little investigated and never applied to heat exchanger hardware development in Europe. Moreover, almost no relevant test data is available in the public domain, and what exists has been obtained from tests with gases rather than liquids. A programme, involving the design, manufacture and performance testing of a HX representative of the Hermes Interloop Heat Exchanger requirements, has been set up in order to explore manufacturing difficulties associated with such low height fins and to verify by test the fin thermo-hydraulic performance.

Cooling infrared and sub-millimeter detectors to temperatures less than 120 K can significantly improve their performance. However, space-based sensors historically have not used active cooling because of the long life requirement as well as demanding requirements for low weight, power, size, and vibration. Sorption refrigerators have the potential to meet these requirements. These refrigerators use a closed cycle Joule-Thomson expansion to produce cooling. High pressure gas compression is produced through thermally-driven chemisorption or physisorption processes. This paper reviews Aerojet's involvement in the development of sorption coolers. System configurations for producing various temperatures, sorbent materials, performance enhancing regeneration techniques, and associated component technologies are included. Finally, some recent efforts at bringing sorption to the commercial market are reported.

The thermo-optical properties of optical solar reflectors (OSRs) can be modified by thin films. Development activity has produced a mirror with a solar absorptance of 0.04. The UV reflector has also been combined with a conductive layer for electrostatic discharge resistance, and functions over a range of solar flux incidence angles. This paper will provide an update on work that has been carried out.

A centrifugal pump concept was elaborated for a multiple application in future spacecrafts. Based on this concept a prototype of a small centrifugal pump was manufactured and comprehensively tested. The model pump has been approved in different test series with the fluids liquid ammonia and demineralized water. The design of the model pump was driven by the strict requirements of COLUMBUS, namely long life, noiseless operation, minimum mass and low energy consumption. Because of its modular design and as a result of selected materials of multiple compatibility, this pump is suited for the delivery of various further fluids, such as freons, hydrocarbons, propellants (hydrazine) etc.. It is also capable of pumping corrosive or toxic fluids for laboratory processes in space. The wide speed range from about 1,000 to 20,000 rpm which corresponds to a flow from about 1 to 20 l/min, permits an energy saving adaption and flow control.

For the determination of the solar absorptance αs and the thermal emittance ε preferably optical methods are utilized. To these methods belong spectral reflectance αs and ε measurements and / or emission measurements (only ε), whereby for αs must be measured in the common range 0,3 μm to 2,5 μm and ε in the range 5 μm to 35 μm with an essentially better resolution than 10 nm. Besides so-called integrated reflectance measurements are known, for which special detectors are used, in the above indicated spectral ranges. These optical measuring procedures are relatively exact. They deliver also information about a perhaps spectral selective behavior of surfaces, however, special measuring equipment is required.

Integral black anodizing and gold plating on Mg-Li alloys were developed for spacecraft thermal control applications. The influence of various process conditions have been investigated to optimise the process. The deposits were characterized by morphological studies, adhesion test, thickness measurement, microhardness evaluation and porosity inspection. The space worthiness of the coatings has been evaluated by humidity, thermal cycling, and thermovacuum tests and measurement of optical properties. The high solar absorptance and infrared emittance (αs = 0.95, εIR = 0.93) value of black anodic film showed that these can be effectively utilized to improve heat radiation characteristics. The gold coating on the other hand provides the infrared emittance as low as 0.03, is extremely suitable in minimising the radiative coupling with other components within the spacecraft.

The MELISSA (Microbial Ecological Life Support System Alternative) project, conceived as a microorganism based ecosystem, is an early simplified model of a future biological life support system for manned space missions. The driving element is the recovery of edible biomass from waste, CO2 and minerals with direct use of light as a source of energy for photosynthesis. MELISSA is composed of four axenic compartments colonised by microorganisms and of a fifth compartment that is the crew on board the craft. This paper reports on the solution of mass balances over the entire MELISSA loop. The compartments within MELISSA are first analysed separately, each compartment being described by one or more stoichiometric equations derived from knowledge of the cells metabolic pathways. For each stoichiometric equation a key substrate entering a compartment is assumed to be completely exhausted at the outlet; process kinetics such as rates of biological reactions and mass transfer are ignored.

The NASA Controlled Ecological Life Support System (CELSS) Program has the goal of developing life support systems for humans in space based on the use of higher plants. The program has supported research at universities with a primary focus of increasing the productivity of candidate crop plants. To understand the effects of the space environment on plant productivity, the CELSS Test Facility (CTF) has been developed as an instrument that will permit the evaluation of plant productivity on Space Station Freedom. The CTF will maintain specific environmental conditions and collect data on gas exchange rates and biomass accumulation over the growth period of several crop plants grown sequentially from seed to harvest. To better understand the systems needed to support plants and maintain the environmental conditions required by CTF, an Engineering Development Unit (EDU) is being constructed at NASA Ames Research Center in the Advanced Life Support Division.

This paper describes a newly designed, 2.7 Kg (6 pound) capacity, laundry machine called the Single Phase Space Laundry (SPSL). The machine was designed to wash and dry crew clothing in a micro-gravity environment. A prototype unit was fabricated for NASA-JSC under a Small Business Innovative Research (SBIR) contract extending from September 1990 to January 1993. The unit employs liquid jet agitation, microwave vacuum drying, and air jet tumbling, which was perfected by KC-135 zero-g flight testing. Operation is completely automated except for loading and unloading clothes. The unit uses about 20 percent less power than a conventional household appliance.