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This paper is intended to address the process of System Analysis in the area of Advanced Life-Support Systems (ALSS). Particular attention is given to Controlled Ecological Life Support Systems (CELSS) architectures. The process of System Analysis is an iterative one in which “trade-offs” of various system elements are executed to evaluate system functionality and structure. In the process, consideration is given to factors such as system requirements, potential architectures and design concepts, integration issues and system operations. The emphasis of the paper is on developing a consistent framework for the analysis process. It is anticipated that by developing a formal framework, particularly for the systems analysis of a CELSS, comparisons of approaches and of quantitative assessments will be made easier.

The MELISSA (Microbial Ecological LIfe Support System Alternative) project has been set up to be a model for the studies on ecological life support systems for long term space missions. The compartmentalisation of the loop, the choice of the micro-organisms and the axenic conditions have been selected in order to simplify the behaviour of this artificial ecosystem and allow a deterministic and engineering approach. In this framework the MELISSA project has now been running since beginning 1989. In this paper we present the general approach of the study, the scientific results obtained on each independent compartment (mass balance, growth kinetics, limitations, compound conversions,..), the tests of toxicity already performed between some compartments and their effect on the growth kinetics. The technical results on instrumentation and control aspects, and the current status of the ESA/ESTEC hardware are also reviewed.

One way to increase thermal software performance has been developed at AEROSPATIALE Cannes by means of a condensation algorithm for conductive models (EQUIVALE). The benefit of this improvement is exportable to other software packages by developing specific interfaces. Therefore, two gateways are now available to perform ESATAN conductive models condensation: the first (ESAEQU) translates the initial ESATAN input deck into the different files required by EQUIVALE; the second (EQUESA) generates a new ESATAN input deck including the equivalent conductances provided by EQUIVALE. Three examples of application are described hereafter: the first (RADIATOR PANEL) illustrates the condensation processing coupled to ESATAN, the second (TV-SAT/TDF), more realistic, refers to a flight model in the frame of the AEROSPATIALE Thermal Software environment and the third (TÜRKSAT) shows the optimum use of EQUIVALE with the combination of both PLATEAU and EQUIVALE software packages.

Prototype bioreactor using internal lighting mechanism was manufactured for biological CO2/O2 conversion system. Microalgae culturing experiments were carried out on Chlorella ellipsoidea C-27 to estimate the effect of light intensity on photosynthetic activity in the reactor. The light energy source used was an Xe(xenon) lamp, from which light is transferred through optical fibers and diffused from the surface of rods made of acrylic resin. Total surface area of the rods was 0.12m2. Tests under the continuous lighting (600W) condition indicated a highest specific growth rate of 8.54 (h-1), a highest cell density of 1.3 × 108 (cells/ml), and a maximum overall photosynthetic rate (CO2 absorption rate) of 171.84 (mg-CO2 absorption/Ir-medium/day). In contrast, the maximum CO2 absorption per chlorophyll content (mg-CO2 absorption/mg-chl/h) was reached under the alternating lighting condition.

As a consequence of the continuously increasing complexity of design, development and qualification of modern spacecraft subsystems, computer aided tools become increasingly important for solving the various engineering tasks in these fields. In the framework of development tasks for satellites and space stations, e.g. ERS-I/II, ROSAT, CLUSTER, SOHO, COLUMBUS-ECLSS, and HERMES a software environment has been developed at Dornier GmbH in recent years, which allows thermal analysis, thermal control and space environment control for system simulation as well as for detained component level simulation, monitoring and testdata evaluation. COSITHERM is a modular software package for the prediction of thermal radiation effects. SIMTAS can be used for detailed analysis of single system components as well as for the prediction of system response of arbitrarily connect components.

The most important CELSS engineering parameters are, in order of decreasing importance, manpower, mass, and energy (1). The plant component is a significant contributor to total system equivalent mass. In this report, a generic plant component is described and the relative equivalent mass and productivity are derived for a number of instances taken from the KSC CELSS Breadboard Project data and the literature. Typical specific productivities (edible biomass produced over 10 years divided by system equivalent mass) for closed systems are of the order of 0.2.

The first part of this paper concerns the presentation of CEDRIC. CEDRIC (Code d'Etudes Dynamique de Réseaux Inter Connectés) is a one dimensional thermalhydraulic software which is capable of modelling single and two phase flow for steady state and transient conditions. It has been developed by CEA/TECHNICATOME (French national nuclear agency) for nuclear cooling system design and failure analysis. It is a “3+1” equations software (mass, momentum, energy for the fluid and energy for the walls linked to fluid). These equations are solved using a finite difference method with a fully implicit resolution, which allows the use of large time steps in comparison to the ones imposed by the Courant limit. In order to fulfil the requirements of spaceborne fluid loop analysis, CNES required some adaptations such as new fluids and new elements (radiators for example).

The Microcomputer Spacecraft Thermal Analysis Routines (MSTAR) software package is being developed for NASA/Goddard Space Flight Center by Swales and Associates, Inc. (S&AI). Thermal analysis of large-scale spacecraft are currently being performed with industry standard programs such as SSPTA1, VIEW2, and TRASYS3. These software packages, however, are based on solution algorithms developed as much as 25 years ago. Many of the algorithms used in these programs are based on software and hardware available at that time. In recent years, the computer industry has made tremendous technological advances in providing powerful yet inexpensive desktop computers capable of competing with small mainframe computers. In December 1992, S&AI was awarded a Phase I Small Business Innovative Research contract from NASA to develop a microcomputer based thermal analysis program to replace the current SSPTA and TRASYS programs.

Manned space laboratories like the US Space Station Freedom or the european COLUMBUS APM are equipped with so-called racks for subsystem and payload accommodation. An important resource is air for cooling the unit internal heat sources, the avionics air. Each unit inside the rack must be supplied with sufficient amount of air to cool down the unit to the allowable maximum temperature. In the course of the COLUMBUS ECLSS project, a thermohydraulic mathematical model (THMM) of a representative COLUMBUS rack was developed to analyse and optimise the distribution of avionics air inside this rack. A sensitivity and accuracy study was performed to determine the accuracy range of the calculated avionics air flow rate distribution to the units. These calculations were then compared to measurement results gained in a rack airflow distribution test, which was performed with an equipped COLUMBUS subsystem rack to show the pressure distribution inside the rack.

This paper discusses the design and implementation of an interactive graphic modeling system for finite difference thermal analysis. It reviews the current state of affairs with respect to finite element modeling systems and then presents the requirements for a new modeling system. Progress towards a finite difference modeling system is also reviewed.

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.