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Technical Paper

Permeable Membrane Experiment

1993-07-01
932161
The purpose of the Permeable Membrane Experiment is to gather flight data on three areas of membrane performance that are influenced by the presence of gravity. These areas are: (1) liquid/gas phase separation, (2) gas bubble interference with diffusion through porous membranes and (3) wetting characteristics of hydrophilic membrane surfaces. These data are important in understanding the behavior of membrane/liquid/gas interfaces where surface tension forces predominate. The data will be compared with 1-g data already obtained and with predicted microgravity behavior. The data will be used to develop designs for phase separation and plant nutrient delivery systems and will be available to the life support community for use in developing technologies which employ membranes. A conceptual design has been developed to conduct three membrane experiments, in sequence, aboard a single Complex Autonomous Payload (CAP) carrier to be carried in the Shuttle Orbiter payload bay.
Technical Paper

A Centrifugal Pump Concept Designed for Multiple Use in Space

1993-07-01
932120
Abstract 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.
Technical Paper

Technology Improvements to Optical Solar Reflectors

1993-07-01
932121
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.
Technical Paper

A Thermal Method for the Determination of Solar Absorptance and Thermal Emittance of Spacecraft Coatings

1993-07-01
932122
I. Abstract 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.
Technical Paper

Thermal Control Coatings on Mg-Li Alloys

1993-07-01
932123
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.
Technical Paper

Thermal, Mass, and Power Interactions for Lunar Base Life Support and Power Systems

1993-07-01
932115
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.
Technical Paper

Survey and Evaluation of Multilayer Insulation Heat Transfer Measurements

1993-07-01
932117
About 40 papers treating multilayer insulations were studied and compared. Most of these papers present heat transfer measurements in addition to thermal analysis. Here the equations are given which are required for an evaluation of the measurements and in particular for comparisons. Equations are presented which are required to predict the influences of the packing density, temperatures, fraction of perforation area and interstitial pressure. The equation giving gas conductivity versus pressure is modified according to measurements. In space the interstitial pressure is usually below 0.01 Pa und the heat transfer can be expressed as the sum of a conductive and a radiative term. The equation finally proposed for spacecraft permits to consider the influence of temperature, number of layers, blanket size and perforation area.
Technical Paper

Porous Insulation Performance Under Martian Environment

1993-07-01
932116
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.
Technical Paper

Investigation of Lunar Base Thermal Control System Options

1993-07-01
932112
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.
Technical Paper

A Low Fin Height Heat Exchanger Technology Demonstrator for Hermes

1993-07-01
932119
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.
Technical Paper

Moderate Temperature Control Technology for a Lunar Base

1993-07-01
932114
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.
Technical Paper

Condensing Heat Exchanger Microbial Growth and Control Study-Phase II

1993-07-01
932107
The Space Station Temperature and Humidity Control Condensing Heat Exchangers will be utilized to collect and remove atmospheric water vapor generated by the metabolic and hygienic activity of crew members. The porous hydrophilic coating within the heat exchangers will always be wet. Cabin air will continuously flow through the heat exchangers during system operation which makes them a potential site for microbial colonization. This paper summarizes the findings from an ongoing study which evaluates biofilm formation on wet hydrophilic coated panels compared to panels to which microbial control measures have been applied. The control measures evaluated are an antimicrobial agent within the coating and periodic drying.
Technical Paper

Sorption Refrigerators A Review of Current Development Status

1993-07-01
932118
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.
Technical Paper

Space Station Freedom Carbon Dioxide Removal Flight Design

1993-07-01
932108
Boeing is responsible for Space Station Freedom (Work Package (WP) 01) which includes the Habitat and U.S. Laboratory modules, which includes the integration of the Environmental Control and Life Support System (ECLSS). Included as part of the ECLSS is the Atmosphere Revitalization (AR) subsystem. The AR subsystem provides for removal of metabolic carbon dioxide, removal of trace contaminants, and continuous monitoring of the cabin atmosphere major constituent composition during the Manned Tended Configuration (MTC) phase of station operations. The focus of this paper is on the Carbon Dioxide Removal Assembly (CDRA) flight design aspects of the Space Station Freedom (SSF) AR subsystem. A Four Bed Molecular Sieve (4BMS) has been selected by Boeing as the CDRA for SSF. The CDRA removes carbon dioxide from an air slip stream pulled from the Cabin Air Temperature & Humidity Control (THC) assembly.
Technical Paper

Hyperbaric Environmental Control Assembly for the Space Station Freedom Airlock

1993-07-01
932109
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.
Technical Paper

Thermal Environment and Thermal Control Aspects for Mars Landers

1993-07-01
932111
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.
Technical Paper

The Development of Advanced Thermal Analysis Modelling Systems

1993-07-01
932137
Abstract 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.
Technical Paper

Microcomputer Spacecraft Thermal Analysis Routines (MSTAR) Phase I: The User Interface

1993-07-01
932136
Abstract 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.
Technical Paper

Space Station Microscopy: Beyond the Box

1993-07-01
932143
Microscopy aboard Space Station Freedom poses many unique challenges for in-flight investigations. Disciplines such as materials processing, plant and animal research, human research, environmental monitoring, health care, and biological processing have diverse microscope requirements. The typical microscope not only does not meet the comprehensive needs of these varied users, but also tends to require excessive crew time. To assess user requirements, a comprehensive survey was conducted among investigators with experiments requiring microscopy. The survey examined requirements such as light sources, objectives, stages, focusing systems, eye pieces, video accessories, etc. The results of this survey and the application of an Intelligent Microscope Imaging System (IMIS) may address these demands for efficient microscopy service in space.
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