Active Thermal/Fluids/Life Support
TFAWS2020-AT-200-Togaru: Design of Exoskeleton for Musculoskeletal Support of Human Body Under Low Gravity Conditions and its Performance Evaluation by Fluid Dynamic Analysis
Author(s): Lavanith Togaru and Karthik Naganathan
The human body has evolved and adapted to the environmental conditions it lives in. Any drastic changes in these conditions may affect its normal functioning. This makes space travel a potential hazard to the astronauts due to its harsh environment. To achieve a safe travel in either long commute to a planet or a short trip to ISS and the moon, the environmental conditions have to be controlled. The cabin of spacecraft and the spacesuit are designed to control the temperature and pressure according to the requirements of the astronauts. But problems arise due to the prevailing low-gravity and microgravity conditions in space. Compared to other issues, the loss of bone mineral density, hydrostatic pressure reduction, and orthostatic hypotension are badly affecting the astronauts from the past. Although there are some curative adoptions, many of them are not quite effective. This paper summarizes the use of a specially designed exoskeleton for the human body which can be used in space travel to lower some of the health risks which arise due to change in gravity. The exoskeleton was designed considering different joints and their Range of Motions (ROM) to support normal functional movements of the body in space. It covers from shoulders to foot which contains fluid-carrying tubes embedded into it. These fluid lines and different biomimicked joints form as functional elements in the exoskeleton. Fluid dynamic analysis is used to evaluate the nature of fluid flow and to check its biomechanical performance. The results obtained are used to investigate its biological and medical relevance in the areas of musculoskeletal and cardiovascular systems. In view of the complexity in the fabrication of embedded fluid lines, this design was made compatible with additive manufacturing for ease of
TFAWS2020-AT-201-Nishikawara: Pore-scale Approach to Developing High-Performance Capillary Evaporator in Loop Heat Pipe
Author(s): Masahito Nishikawara
Two-phase state in the porous media of loop heat pipe (LHP) evaporator, which is induced by nucleate boiling, is key to enhance the evaporator performance but complicated. To investigate the liquid-vapor phase behavior and the relationship with the evaporator heat-transfer coefficient, this work visualizes the liquid-vapor phase distribution at the contact surface between the evaporator casing and wick and simulates the two-phase thermal hydraulics in the evaporator by pore network model. The visualization study shows evolution of the liquid-vapor phase distribution with changing the heat load and the relationship between the length of the three-phase contact line (TPCL) within the casing, liquid and vapor phase and the heat-transfer coefficient. The simulation work shows effect of pore size distribution of the wick on the heat-transfer coefficient which will be presented in the paper.
A sapphire tube having the thermal conductivity comparable to metal was used for the cylindrical evaporator casing that has a wick inside. A transparent conductive film of indium tin oxide to the same length as the groove was formed on the surface of the evaporator, and the heat flux was applied by electric heating. This makes it possible to perform visualization experiments. Since the constructed LHP visualizes with practical thermal materials, the observed vapor-liquid interface behavior can be closer to the actual behavior. The images of the vapor-liquid phase interface at the contact surface between the wick and casing were taken with a single-lens reflex camera, and the captured images were distinguished between the vapor and liquid phase region by binarization.
TFAWS2020-AT-203-Ems: Turbulent Drag Reduction/Enhancement in a 304 Stainless Steel Rectangular Channel Functionalized with a Femtosecond Laser
Author(s): Henry Ems, Aaron Ediger, Alfred Tsubaki, Craig Zuhlke, Dennis Alexander, and George Gogos
In this paper, we present methods for enhancing or reducing drag experienced by metallic surfaces (304 stainless steel) functionalized with a femtosecond laser. Experiments were conducted with purified water (0.2 μm filtration). Femtosecond laser surface processing (FLSP) was performed on 304 stainless steel plates to create angled microstructures, which mimic those of shark skin. Data were collected at different Reynolds numbers by varying the mass flow rate. Data were recorded after steady state was reached. The processed plates were superhydrophilic and were used to obtain the friction factor in a rectangular channel test section over Reynolds numbers ranging from 8,000 to 13,000. For a superhydrophilic rectangular channel with angled structures, drag enhancement was measured with respect to smooth (unprocessed) surfaces over the total range of Reynolds numbers tested. After superhydrophilic testing was completed, the surfaces were coated with fluorinated silane using evaporative deposition that made the plates hydrophobic. The hydrophobic plates were then tested in the rectangular channel setup to obtain the friction factor. With the addition of an acrylic viewport, the presence of an air layer (plastron) was observed that sheds light to the friction factor data obtained for hydrophobic plates. Drag reduction was shown for Reynolds numbers that were accompanied with a thin plastron. When the plastron fully degraded, the surface was fully wetted, and the friction factor value shifted towards just below the superhydrophilic value.
TFAWS2020-AT-204-Robinson: Flow Boiling in Microgap Coolers—Suborbital Flight Results
Author(s): Franklin L. Robinson
Flow Boiling in Microgap Coolers (FBMC) is a thermal management technique that provides embedded, on-site heat removal for power dense electronic components and systems. The dielectric coolant undergoes liquid-to-vapor phase change as it passes through channels integrated within or between devices. By facilitating direct contact between the coolant and heat-generating devices and relying on phase change, the system provides tight temperature control, hot spot mitigation, very high heat transfer coefficients, and low pumping power. Ground tests demonstrated removal of high heat fluxes (up to 500 kW/m2), very high coefficients of performance (up to 40 W of heat transferred per W of pumping power), and consistent performance across five evaporator orientations under the appropriate conditions. As a follow-on study and to better assess the role of gravity on such two-phase systems, the FBMC payload was developed and flown twice aboard the Blue Origin New Shepard space vehicle in January and May 2019. Each flight exposed the payload to weightlessness (150 seconds below 0.01 g) and shorter periods of high-g during ascent (up to 3 g) and descent (up to 5 g). The flow boiling performance was consistent independent of the acceleration levels, which provides confidence that such systems will provide consistent performance when tested on the ground, orbiting or traveling through weightlessness, and operating on the surface of the Moon, Mars, and other planetary bodies. Details of the flight results, payload development, flight environment, and planned future testing will be presented.
TFAWS2020-AT-206-Hasan: Development of a Numerical Solver for Phase-Change and Two-Phase Flow in Porous Media
Author(s): M. Iffat Hasan, Kegan Rahe, and Mustafa Hadj-Nacer
Porous media are used in several thermal management systems, such as loop-heat-pipes, to control the temperature of electronics and other components. It is important to understand the mechanisms of flow and phase-change in porous media to better control/increase the performance of those systems. In this work, we develop a unique computational fluid dynamics (CFD) solver in the object-oriented OpenFOAM architecture that can simulate most of all the relevant physics of flow and phase-change in porous media. Available commercial and open-source solvers lack many of the capabilities to simulate important characteristics of flow and phase-change in porous media. The developed solver is based on a flow solver in which the IMPES (Implicit Pressure, Explicit Saturations) method is employed to solve the pressure and saturation equations due to the nonlinearity of the capillary and relative permeability models. The solver is then modified to include the energy equation and phase-change models (empirical and interface equilibrium models) that can simulate temperature and phase-change, respectively. Hydrodynamic and thermal coupling of flow and phase change in porous media is complex numerically, and, this complexity is achieved in the present study by coupling between all the governing equations and the phase-change models using the VOF (Volume of Fluid) approach. Different effective thermal conductivity models are implemented to calculate an effective thermal conductivity between the three phases (solid, liquid, and vapor) in every cell. The solver also uses temperature-dependent properties for density, thermal conductivity, and viscosity. The results obtained from this solver are compared with a one-dimension semi-analytical solution to validate the solver. Results from flow and phase-change simulations in the porous media of a loop heat pipe will also be presented.
TFAWS2020-AT-207-Brendel: Similar Fluids as a Means to Experimentally Predict the Performance of Two-Phase Flow Systems at Reduced and Microgravity
Author(s): Leon P. M. Brendel, Eckhard A. Groll, and James E. Braun
Extraterrestrial habitats are an emerging research topic, mostly because of the desire to establish human bases on the Moon and the Mars. These habitats will be supported, among others, by thermal systems, many of which ideally use two-phase systems. Examples are refrigeration cycles, pumped two-phase loops, Rankine power-cycles or distillation for waste water recovery. The performance prediction is very important but two-phase systems in microgravity or reduced gravity are poorly understood and the testing opportunities are scarce and expensive. One research approach is to select a fluid for terrestrial testing such that another fluid at reduced gravity will be approximated, a process mostly relying on selected dimensionless numbers. This research field has received some attention during the design of the International Space Station, but a large-scale approach to finding similar fluids has not been presented. This paper groups fluids that are similar according to different requirement-sets and at different gravity levels. Researchers that design buildings for reduced gravity can use these results to consider similarity studies in their terrestrial experiments.
TFAWS2020-AT-208-Islam: Experimental and simulation analysis of flat plate loop heat pipes sink temperature
Author(s): Md Sahidul Islam, Yang guang, and Wu jing yi
TFAWS2020-AT-209-Naganathan: Thrust Performance Evaluation of Chemical Rocket Engine by Thermal and Fluid Dynamic Analysis for Exhaust Gas Flow Subjected to Cooling
Author(s): Karthik Naganathan and Lavanith Togaru
Chemical rocket engines play an important role in space travel as they produce high thrust, required for initial lift- off of the rocket. Deep space exploration mission is very expensive, as most of the engines in use are chemical rocket engines and they operate with low efficiency. Even if electric propulsion systems are used, they cannot replace the solid or liquid propellant rocket engines, as only they are capable of generating high thrust. The thrust is essentially generated by combustion process of propellant and oxidizer. But the thrust is fundamentally a function of mass flow rate, pressure and velocity of the exhaust gas and the temperature gained due to the combustion does not contribute to the generation of thrust. By the conversion of a property, such as exhaust gas temperature, which cannot contribute to increase of thrust into a useful property such as the exhaust gas pressure, the efficiency of thrust generated by the rocket engine at the nozzle chamber exit can be improved. The cooling systems that are currently in use mainly focus on prevention of overheating of rocket engine structure but do not serve to cool the exhaust gas.
This paper studies the feasibility of achieving isenthalpic flow of exhaust gas in the engine nozzle chamber to convert temperature of the exhaust gas into exhaust pressure. This is achieved by cooling the exhaust gas. Thermal analysis of the temperature distribution is performed to evaluate the thrust characteristics before and after cooling of exhaust gas. The design requirements for the cooling mechanism as well as the effect of geometric modifications are discussed. Fluid dynamic analyses for flow regimes of subsonic, sonic and supersonic conditions are done for geometries to evaluate the thrust performance. Improvement of thrust efficiency can greatly reduce the cost of space travel.
TFAWS2020-AT-210-Hansen: Laser Processed Condensing Heat Exchanger Technology Development
Author(s): Scott Hansen
Current state-of-the-art Condensing Heat Exchangers (CHXs) require non-permanent coatings which have a history of degrading over time, becoming hydrophobic, and potentially contributing to dimethylsilanediol (DMSD) production on a spacecraft. Ultimately, this type of heat exchanger must be uninstalled and sent back to earth for refurbishment, which is not an option for spaceflight beyond low earth orbit. These significant technical issues must be solved for deep-space spaceflight. In continued pursuit of a high reliability CHX, a silver, dimpled sub-scale Laser Processed CHX (LP-CHX) was designed and manufactured. The LP-CHX does not require a coating, but rather relies only on a femtosecond laser processed silver surface for condensing. This paper highlights the design, development, manufacturing, and testing of the LP-CHX as well as the laser processing of the silver surfaces. Additionally, further microbial growth testing and long duration laser processed condensing tests are reported. These studies conclude that silver laser processed surfaces significantly minimize microbial growth and fungal growth when compared to plain silver and stainless steel metals.
TFAWS2020-AT-211-Popok: Thermal Design Challenges Posed by the Four Bed CO2 Scrubber COTS Air-Save Pump
Author(s): Daniel P Popok
The Four Bed Carbon Dioxide (4BCO2) scrubber Air-Save Pump (ASP) operates as part of the adsorbent bed regeneration cycle. The ASP removes residual air from the bed for return to the cabin prior to heat and vacuum exposure which drives out the CO2 regenerating the bed. 4BCO2 employs a Commercial Off-the-Shelf (COTS) scroll type air pump, repackaged in an acoustically insulated enclosure to reduce noise and mounted to a cold plate. The International Space Station (ISS) Low Temperature Loop (LTL) flow (operating between 38°F and 50°F) first cools the process air, and then flows through the cold plate, cooling the pump. This results in competing ASP thermal design goals: (1) to keep the pump and motor sufficiently cool and (2) to avoid forming condensation due to over-cooling. Surfaces below 60°F typically warrant careful consideration of condensation. A test-calibrated thermal model demonstrates such a balanced design is feasible with temperatures above 60°F. A separate, coupled fluid model predicts the potential for condensation formation, allowing risk assessment of flying with the unmodified design.
TFAWS2020-AT-212-Wall: A Thermal Review of the Sample Cartridge Assembly (SCA) Gravitational Effect of Distortion in Sintering (GEDS) Experiment Flight Processing
Author(s): David L. Wall and Deborah Hernandez
NASA’s Sample Cartridge Assembly (SCA) first flight experiment, Gravitational Effect of Distortion in Sintering (GEDS), was processed on the International Space Station (ISS) between 2019 and 2020. The SCA was heated in the European Space Agency’s (ESA) Low Gradient Furnace (LGF) that is housed inside the Material Science Research Rack (MSRR) located in the U.S. Laboratory Module. This summary will give a review of the design and flight experiment development for the GEDS SCA. It describes flight processing and the role of thermal engineering support. Lessons learned and future Principle Investigators (PI) will be discussed.
TFAWS2020-AE-400-Brown: A Study Into Validating a Coupled Method of Characteristics and Direct Simulation Monte Carlo Method Against Empirical Data
Author(s): Andrew Brown
TFAWS2020-CT-100-Naganathan: Evaluation of Additive Manufacturing Compatible Cryogenic Loop Heat Pipe Design by Computational Fluid Dynamic Analysis
Author(s): Karthik Naganathan and Lavanith Togaru
The human body has evolved and adapted to the environmental conditions it lives in. Any drastic changes in these conditions may affect its normal functioning. This makes space travel a potential hazard to the astronauts due to its harsh environment. To achieve a safe travel in either long commute to a planet or a short trip to ISS and the moon, the environmental conditions have to be controlled. The cabin of spacecraft and the spacesuit are designed to control the temperature and pressure according to the requirements of the astronauts. But problems arise due to the prevailing low-gravity and microgravity conditions in space.
Compared to other issues, the loss of bone mineral density, hydrostatic pressure reduction, and orthostatic hypotension are badly affecting the astronauts from the past. Although there are some curative adoptions, many of them are not quite effective. This paper summarizes the use of a specially designed exoskeleton for the human body which can be used in space travel to lower some of the health risks which arise due to change in gravity.
The exoskeleton was designed considering different joints and their Range of Motions (ROM) to support normal functional movements of the body in space. It covers from shoulders to foot which contains fluid-carrying tubes embedded into it. These fluid lines and different biomimicked joints form as functional elements in the exoskeleton. Fluid dynamic analysis is used to evaluate the nature of fluid flow and to check its biomechanical performance. The results obtained are used to investigate its biological and medical relevance in the areas of musculoskeletal and cardiovascular systems. In view of the complexity in the fabrication of embedded fluid lines, this design was made compatible with additive manufacturing for ease of fabrication.
TFAWS2020-CT-101-Baldwin: Boiling Channel Modeling in Generalized Fluid System Simulation Program (GFSSP)
Author(s): Michael Baldwin
TFAWS2020-CT-102-Moradikazerouni: 0D/3D Computational Modeling of a Pressurized Cryogenic Tank in Normal Gravity Condition
Author(s): Alireza Moradikazerouni, Mehdi Vahab, and Kourosh Shoele
TFAWS2020-CT-103-Wilhite: Solar White Thermal Coating for Cryogenic Propulsion Systems
Author(s): Jarred Wilhite and Jason Wendell
NASA is currently conducting research into the potential of storing cryogenic fluid in low Earth orbit (LEO). Having cryogenic propellant readily available for high-performance propulsion systems can be very beneficial for deep space missions in the near future. One of the key challenges to storing cryogenic fluid in LEO is minimizing boil-off. To address the challenge, NASA is evaluating new concepts in thermal insulation. One recent experimental study evaluated the feasibility of using Yttrium Oxide (Y2O3), formed into tiles or spray coating that can potentially be used as a thermal coating for cryogenic propellant storage applications in deep space. Due to its temperature and wavelength dependent optical properties, this “solar white” material can reflect a vast majority of the Sun’s radiative energy while having a very high infrared emissivity for rejecting heat to deep space.
As a part of the material development and proof of concept testing, multiple tests have been run at KSC and GRC to demonstrate the performance of the material. At GRC, the tests were run using the Deep Space Solar Simulator (DS3) which contains a thermal vacuum chamber in which the solar white sample was exposed to a deep space environment (< 10 K, optically dense walls) while under full illumination via solar lamp. In order to improve the use of the test results and apply them to spacecraft, there is a need to be able to model the material properties within NASA’s standard thermal modeling tools. As such, it was set out to verify a thermal model of one of the experiments using Thermal Desktop with Sinda. The thermal model of the DS3 test setup includes the solar white sample along with a solar lamp simulator capable of outputting heat at varying wavelengths. The model was developed in order to validate the test results and also to help predict results that will be obtained in future tests. This paper will review the modeling methods and thermal analysis results for various test cases that were run within the DS3 facility.
TFAWS2020-ID-500-Biswas: Model Development of Jet Fuel Production From Hydropyrolysis Using Artificial Neural Network
Author(s): M.A. Rafe Biswas and Fernando Resende
The possibility of producing jet fuels from renewable resources has been a topic of interest in recent years. If accomplished, this production would contribute to our energy independence and bring significant environmental benefits. Within this context, the hydropyrolysis process has significant potential to accomplish this goal, by converting solid biomass into jet fuels in a single step. Hydropyrolysis is the thermal conversion of biomass into hydrocarbons in the presence of pressurized hydrogen and a heterogeneous catalyst. The hydrocarbons from hydropyrolysis make up a liquid fuel of similar composition to jet fuels. However, comprehensive information about how hydropyrolysis conditions, such as temperature, pressure, and catalyst characteristics affect the yield and composition of the products are still lacking.
In this project, we developed and trained a three-layer artificial neural network (ANN) to model and predict the yield of liquid products and the hydrocarbon content in the liquid products from hydropyrolysis. The model results were an excellent fit compared to the experimental data for the hydrocarbon content, with coefficient of determination in the range of 0.8 to 0.95 and mean squared error less than 6. Simultaneously, the results of most models for the liquid product prediction were a reasonable fit with coefficient of determination within 0.75 to 0.85 and mean squared error less than 15. The ANN model showed that the yield of liquid products increased with temperature increase from 350oC to 500oC. The models developed in this work can assist in the design and optimization of hydropyrolysis systems for the production of jet fuels in aerospace application.
TFAWS2020-ID-501-Mauro: Generating Payload Environments for a Lunar Lander Mission
Author(s): Stephanie Mauro
In today’s space industry many organizations develop payloads or other components that will fly on a vehicle or lander developed by a different organization. This creates a challenge for the payload developers of knowing the thermal environment, including effects from the spacecraft, of their instrument because the payload engineers will not have continuous access to an up-to-date thermal model of the spacecraft. To circumvent the vehicle developer having to provide a thermal model of the spacecraft to payload developers for detailed thermal analysis, the vehicle developer can provide environmental data to the payload engineers to apply to their payload model, instead. This data must include the boundary temperatures where the payload is mounted, sink temperatures, and both incident solar and infrared thermal flux. This paper will describe the method used to generate thermal environments for payloads on the Astrobotic Lunar Lander and how those environments were applied to an example payload, the Neutron Measurement at the Lunar Surface (NMLS) instrument. This work is unique because a standard method for generating and delivering payload environments does not exist. Benefits and drawbacks of using this method will also be discussed.
TFAWS2020-ID-502-Hengeveld: Reduced-order modeling for rapid mission planning of the Mars 2020 Helicopter
Author(s): Derek Hengeveld, PhD, PE, Jacob Moulton, and Stefano Cappucci
The Mars Helicopter is a technology demonstration to be conducted during the Mars 2020 mission. The primary mission objective is to achieve several 90-second flights and capture visible light images via forward and nadir mounted cameras. In addition, these flights could possibly provide reconnaissance data for sampling site selection for other Mars surface missions. The helicopter is powered by a solar array, which stores energy in secondary batteries for flight operations, imaging, communications, and survival heating. The helicopter thermal design is driven by minimizing survival heater energy while maintaining compliance with allowable flight temperatures in a variable thermal environment (i.e.. wide range of sky/ground/air temperatures, solar irradiance, and wind speed).
A Thermal Desktop® model was developed to help with mission planning for the next Sol (solar day on Mars). The model predicts eight component temperatures (e.g. battery, camera, etc.) and available battery energy as a function of environmental/convection conditions and a battery set-point profile. Given the broad range of input/output factors and limited time in which to perform simulations and evaluate the results, a reduced-order model (ROM) was developed. The ROM, created with the Veritrek software, was used to quickly find a battery set-point profile which optimized battery energy for rapidly changing environmental conditions. As a result, the ROM will be used during mission operations to provide engineers with the proper battery set-point profile to use for the next Sol’s helicopter flight, based on measured telemetry data from the previous Sol.
This paper describes the Mars Helicopter mission, Thermal Desktop® model, and development of the ROM. A description of how the ROM will be used in mission planning for this upcoming mission will be provided.
TFAWS2020-ID-503-Vass-Varnai: Thermal Transient Testing of Semiconductor Components – Fundamentals
Author(s): Andras Vass-Varnai, Ph.D.
The presentation covers the fundamentals of thermal transient testing of semiconductor devices and packages for thermal characterization and how to enhance electronics thermal design of reliable products to achieve goals for size, weight, power and cost by combining use of test and thermal simulation.
The topics will include the application of electrical test methods to determine thermal metrics with confidence, how achieve highest accuracy in package to system level thermal simulation accuracy through model calibration, and how to use thermal transient testing for failure diagnosis during thermal reliability studies and also in quality assessment.
As the functionality of thermal simulators gets more and more complex, measurement techniques also improve. Thermal engineers face an increasingly difficult task to make the right selection from the existing tools. Beside this problem the precise determination of thermal performance indicators such as RthJC or RthJB is becoming more and more difficult as the package geometries become more complex. The thermal characterization of novel power packages hosting a number of dies is a major issue where the standard definitions cannot be applied anymore.
The answer to these challenges may lie in a combined measurement and simulation approach. Measurements yield a structure description of materials having different conductivities; simulation gives the clue what certain sections in the measured structure correspond to. TIM materials are very difficult to model, as neither their conductivity nor their thickness can be defined with high accuracy even by the designer of a given package. Well planned thermal measurements are suitable tools to measure the in-situ resistance of these materials so that they can be later on used for accurate model creation.
As the measurement and simulation techniques mutually support each-other the ultimate solution for package thermal characterization may be the simulation model creation based on real measurements. In the final presentation we will discuss these approaches in details and demonstrate their applicability for designing more reliable electronics for aerospace applications.
TFAWS2020-ID-504-Heersema: Feasibility of Waste Heat Utilization for Electrified Aircraft Wing Anti-Ice Systems
Author(s): Nic Heersema
As the drive for increased efficiency and decreased emissions drives the aviation world towards more electrified aircraft, the availability of excess power or engine bleed air for anti-ice/de-ice of wing leading edges diminishes. The heat requirements necessary for icing protection of the wing should be considered early in the design process to assist in the sizing and design of electric propulsion components and the engines or batteries that drive them.
The heat requirements are primarily dependent on the conditions of the freestream and the shape of the wing. Analysis was performed for the High-efficiency Electrified Aircraft Thermal Research (HEATheR) project. Three representative aircraft configurations were considered in the project: Single-aisle Turboelectric AiRCraft with Aft Boundary Layer propulsion (STARC-ABL), Revolutionary Vertical Lift Technology (RVLT) Tiltwing, and Parallel Electric-Gas Architecture with Synergistic Utilization Scheme (PEGASUS). Initial analysis was performed using LEWICE, a software developed by NASA GRC, to determine the heat requirements necessary to maintain an ice-free surface from the leading edge through the 10% chord. These calculated heat requirements will be used to select an appropriate anti-ice/de-ice architecture and determine the system-level impacts on weight, power, and performance. Initial analysis is complete for the 3 HEATheR aircraft. Results and proposed future work will be presented.
TFAWS2020-ID-506-Szloh: MHK Turbine Theoretical Design
Author(s): Bryan Szloh and Annie Pluse
Different types of marine hydrokinetic turbines were researched and an axial flow design that was presented in a paper by A.S Bahaj, W.M.J. Batten and G. McCann was selected for a theoretical installation at a location around the Hawaiian island of Oahu. This site was selected based upon the availability of surface velocity data, optimal current velocity for turbine operation, relative proximity to the shore, and location in the United States. The experimental Coefficient of Performance (C_p) and Coefficient of Thrust (C_t) curves were compared with the theoretical calculations performed in the software package AeroDyn that was provided with the software download. A point was selected that provided the maximum C_p before the onset of cavitation and was used in conjunction with the Tip Speed Ratio (λ) and Coefficient of Performance to scale the turbine to an outer blade diameter of 18 m. Our results were compared with the scaling done in the paper by Bahaj, Batten, and McCann. A theoretical power output and turbine RPM were obtained at a flow velocity of 1.9 m/s and compared with RPM values in various other papers for aquatic sea life safety. The turbine design is bare (no duct) and is a floating design to capture the higher current velocities near the top of the boundary layer.
TFAWS2020-ID-507-Fabijanic: Supersonic Flow Diagnostics using Optical Nozzles
Author(s): Charles Fabijanic, Ullah Al Habib, and Dr. Jordi Estevadeordal
Optical flow diagnostic techniques have become critical to conduct complex flow diagnostics research. Some of these methods include Particle Image Velocimetry (PIV), both 2D and 3D, Schlieren, Shadowgraphs, and pressure sensitive paints (PSP). For supersonic and hypersonic research, data gathering typically involves using a high-speed wind-tunnel, but some of the issues with wind-tunnels are that they restrict optical access to be able to utilize these visual techniques. To tackle this an innovative glass blown supersonic Mach 2 nozzle is being used to test its ability for these flow diagnostic techniques. To conduct testing for this experiment, a Mach 2 blowdown to atmosphere wind-tunnel was used.
The PSP technique has developed into an important diagnostic tool. It has been shown to be a strong instrument to take measurements in a supersonic and hypersonic flow regime to view surface pressure on test objects, etc. In this investigation, for taking measurements in the wind-tunnel setup, a range of stagnation pressures have been used ranging from 30 PSI to 120 PSI, where 120 PSI would be the required stagnation pressure to isentropically expand to atmospheric conditions. A diamond wedge was used as a test vehicle, and a 3D printed insert was used to match the shape of the supersonic expansion section of the nozzle so inner wall pressures can be measured. Using the wedge shape at a range of up to 60 PSI, potential oblique shock wave pressure trends were able to be observed along with possible shock reflections on the surface at higher pressures. Using the insert compressible flow expansion pressure was seen, with a sudden high-pressure zone occurring at the end of the expansion, also a potential normal shock occurring with used testing conditions.
Some other preliminary results have also been taken using shadowgraphs and 2D PIV. PIV results were taken using 5 micron hollow spheres for seeding. Due to their large diameter particle lag is prevalent with these results, but still show flow trends in the wind-tunnel. Water condensation from air humidity was also observed and it can be used as flow seeding. At this low inlet pressure, the flow velocity was observed to be up to 400 m/s or a Mach number of 1.2 in our supersonic nozzle. Observable in some preliminary results are normal shock waves forming in the expansion of the nozzle due to low inlet pressure (20 PSI inlet testing conditions). Shadowgraph results seem to confirm this hypothesis as well.
Overall results show that it is possible to obtain results using a glass blown nozzle for optical diagnostics of high-speed test targets and of the inner walls. Compressible flow trends are observable using PSP testing along with some preliminary PIV and Shadowgraphs. Mainly PSP has been used with this investigation to generate pressure maps showing the change from subsonic to supersonic based on the inlet pressure. By investigating some of the preliminary results, it is possible to see the application of the glass blown nozzle for supersonic research in the future.
TFAWS2020-ID-508-Burbridge: Development of the Lunar Environment Monitoring Station Thermal Control Subsystem Design
Author(s): Ethan Burbridge, Rommel Zara, and Alan Kopelove
The Lunar Environment Monitoring Station (LEMS), funded by NASA’s Development and Advancement of Lunar Instrumentation (DALI) program, aims to operate instrumentation delivered to the surface of the moon by a Commercial Lunar Payload Services (CLPS) lander for 24 lunar days, or 2 Earth years, at a mass of 35 kg. The current LEMS TRL-6 development at the Goddard Spaceflight Center effort baselines a mass spectrometer and seismometer for scientific instrumentation but the LEMS has been designed to accommodate a variety of scientific payloads. The design of the LEMS Thermal Control Subsystem (TCS) addresses the extremes of the lunar thermal environment with a novel solution.
Despite its proximity as Earth’s nearest neighbor, the lunar surface is one of the most extreme thermal environments in the solar system. With the moon tidally locked to Earth, surface spacecraft must contend with a day of 354 hours and eclipse of 354 hours. Long solar days and regolith optical properties result in surface temperatures from -160°C to 80°C at a latitude of 45°, the current baseline for CLPS landers. Electronic components typically have operational temperature limits from -35°C to 60°C. Daytime regolith temperatures and electronics heat dissipations necessitate heat rejection through radiating surfaces but extended sun exposure at a variety of angles due to the sun transiting the sky throughout the day limit radiator effectiveness to mitigate high temperatures. Additionally, the extended eclipse duration makes the mass of the power subsystem sensitive to small milliwatt changes in continuous power consumption like from heaters.
Long term Apollo instrumentation relied on radioisotope materials to generate power and maintain temperature limits. However, use within a compact system like the LEMS creates a positive design loop where increasing radioisotope heat to survive eclipse necessitates a larger radiator to dissipate that heat during the day which requires further heat during eclipse and so on. The result is a system design that exceeds thermal switch mechanical limits, instrument field of view requirements, and mass limits. Additionally, political hurdles and dwindling supply have limited the attainability of radioisotope heaters and generators.
The LEMS TCS addresses these challenges by mitigating electronic heat loads, incorporating recent developments in thermal control technology, and detailed modeling of all parasitic heat leaks. Scientific operations for high power instrumentation like the mass spectrometer and communications transponder are limited to short windows while all other command and data handling are kept to the bare minimum to mitigate heat loads. Environmental heat loads have been minimized through the use of Integrated MLI with an e* of 0.0020 developed by the QUEST Thermal Group that provides lower heat flux and mass than traditional MLI, helping meet critical thermal and mass goals. IMLI is a robust structural insulation, able to span open spaces and supported on an external frame. New solutions reduce edge and seam heat leaks, and provide lightweight grounding. Surviving launch loads requires a strong mechanical connection to the lander which would result in heat leaks beyond the capability of the TCS so a pyrotechnic mechanism to decouple the launch legs is under development that will reduce the heat leak 4 to 6 times compared to a non-mechanistic solution. Heat transfer through the radiator is controlled by a variable conduction heat switch with an on/off conductance ratio of 100, sold by the Sierra Nevada Corporation. Finally, a trade study has been conducted to select harnessing materials to minimize heat leaks from externally mounted components like the solar arrays. The resulting design is a spacecraft that is able survive surface temperatures through the lunar day and eclipse with the use of 0 to 2 radioisotope heaters units, totaling 0 to 1.6 Watts, depending on scientific payload.
TFAWS2020-ID-509-Bourgeois: Multiphysics Optimization and Applications of Surrogate Thermal Models Using SIMCENTER 3D Space Systems Thermal, SIMCENTER NASTRAN and HEEDS
Author(s): Zouya Zarei, Loic Bourgeois, Jean-François Labrecque-Piedboeuf, Chris Blake, and Christian Semler
Thermal engineers leverage Thermal Math Models to design spacecraft systems, understand the response of such systems to the harsh environment of space, and perform design trade studies to choose amongst various alternatives. However, even conservatively sized models with only a few thousand nodes/elements can be lengthy to simulate, considering long transient maneuvers and mission cycles.
Surrogate models or response-surface models approximate the actual response of a design to the chosen design parameters, using simpler basis functions. Such models can be evaluated very fast, as they are essentially an algebraic computation of the response on the surface fit. They can be used to understand the sensitivity of the design to the different parameters, and save a tremendous amount of time when optimizing the design.
This presentation will elaborate on the usage of surrogate models in comparison to other reduced model techniques, and will demonstrate how a multiphysics surrogate model can be created from a Simcenter 3D Space Systems Thermal (SST) and Simcenter Nastran model using the multi-disciplinary optimization software called HEEDS. This combination of software suite uniquely chained within one environment allows close collaboration between the thermal and the structural analysts to reach simultaneously multiple objectives.
The thermal model of a microsatellite is created in Simcenter 3D SST, with the key design parameters (e.g. radiator dimensions, optical properties, unit mounting resistances) represented as expressions. These expressions are recognized automatically by HEEDS and used to drive a Response Surface DOE study, where the design space is sampled using a Latin Hypercube space filling algorithm. From a thermal point of view, maximum, minimum, or average temperatures, and heat loads can be extracted from Simcenter 3D SST group reports. At the same time, automatic mapping of the temperatures onto a detailed structural model for each iteration allows quick evaluation of the deformation and eccentricity of the optical assembly that needs to stay within specific bounds to meet optical requirements.
Several response-surface model types may be selected in HEEDS, including Kriging and Radial Basis Functions. The response-surface model can then be exported in various languages, such as
TFAWS 2020 – August 17-21, 2020 2
C#, Python, Matlab for further processing, or Modelica for reuse in model-based systems simulation programs.
This demonstrated automatic thermo-elastic/multiphysics evaluation combining a dedicated thermal solver for space applications (SST), a widely accepted structural solver in the industry (Simcenter Nastran) as well as the multi-disciplinary optimization software (HEEDS), all within one environment, is unique and saves a considerable amount of time for the design and validation of new spacecraft.
TFAWS2020-ID-510-Rittenberg: Modeling Cough Droplets in Cabin Environments: How simulation can increase safety in air-travel
Author(s): Durrell Rittenberg, Ph.D.
Improving the safety of air travel is of the utmost importance to the aerospace industry. Although the exact mechanism of the current pandemic transmission is not fully understood, integrators are leveraging computational methods to understand the behavior of coughs in an enclosed environment. To improve the fidelity of these models requires a detailed representation of the physics of the human cough including the distribution and velocities of droplets, evaporation of the water content, the impingement of the droplets of nearby surfaces, and the impact of gravity on the propagation. In this presentation, we will discuss the current state of the art of cough modeling and the extension to air cabins as well as the impact of a standard mask on droplet transmission.
TFAWS2020-ID-511-Blake: Reduced Order Models and Machine Learning Algorithms to Develop Predictive Thermal Tools for Spacecraft Simulations
Author(s): Chris Blake, Christian Semler, Vahid Abdollahi, Martin Kenward, Chris Jackson, and Alexander Kuzmin
In the spacecraft industry, particularly for satellites, accurate predictions of transient thermal behaviour of their components is critical. Unfortunately, such simulations are very time consuming and computationally expensive. As a result, there is a great need to reduce simulation time as much as possible to be able to analyse the full transient thermal behaviour of spacecraft. Reduced Order Models (ROMs) and machine learning techniques can thus be very useful to address these challenges while maintaining the high level of accuracy required in thermal spacecraft analysis.
In this paper, we review the various techniques and concepts of ROMs, and detail a novel method for coupling thermal modelling tools (commercial software Simcenter™ 3D Space Systems Thermal (SST) developed by Maya HTT) with machine learning (ML) algorithms to develop predictive thermal tools for spacecraft simulations. Additionally, we utilize a model reduction method to reduce the complexity of the models, the results of which can then be mapped back onto the original high fidelity models. The ML are trained on existing or generated simulation data and used as a predictive tool to drive thermal physics solutions without the need to explicitly resolve the conductance networks over the entire lifetime of the simulation, thus greatly reducing the burden to run explicit simulations.
TFAWS2020-ID-512-El-Nenaey: Performance Evaluation of Hybrid Vertical Axis Wind Turbine
Author(s): Khaled.M. El-Nenaey, Yehia.A. Eldrainy, Ahmed A. Eissa, and Sadek.Z. Kassab
Since Savonius wind turbine is known by its self-starting ability at a low wind speed while Darrieus characterized by its high efficiency, the present study aims to combine the favor characteristics of Savonius and Darrieus turbine by producing a hybrid vertical axis wind turbine and evaluate its performance. A numerical model was built up by using ANSYS Fluent 17.1 software to simulate the flow over the wind turbine blades. The model was based on 3-dimentional, incompressible and unsteady assumptions. This numerical model was validated by comparing its results with a previous published experimental work for other researchers. The validated model was used to evaluate the performance of the hybrid turbine. Three different configurations of Savonius, Darrieus and combination of them (hybrid turbine) were compared. The simulation results showed that vertical axis hybrid turbine which its Savonius rotor is located inside Darrieus rotor hybrid VAWT can achieve a higher starting torque than that of a conventional Darrieus, Savonius type VAWT. Besides at high Tip Speed Ratio (TSR) the hybrid take advantage of its drag type blades as a guide for the flow to Darrieus blades.
TFAWS2020-ID-513-Sivathanu: A Modular Sensor Suite for Propulsion Testing
Author(s): Yudaya Sivathanu, Jongmook Lim, Marcus Wolverton, Vinoo Narayanan, and Jason Green
Industrial process tomography is widely used for the characterization of a wide variety of physical processes. One of the drawbacks of process tomography equipment is that they are specific to a particular application and process. Therefore, different instruments are required for characterizing turbulent sprays and flames. A modular sensor suite is developed to characterize flames and sprays used in the propulsion industry. The sensor suite enables the user to select from a range of plug and play emitter and sensor modules to estimate several physical characteristics of the system under study. The sensor suite developed in this study is capable of measuring planar temperatures, radical species concentrations (such as OH, AlO, CH, C+), and particulate volume fractions in flames and planar surface area densities and drop sizes in sprays. The modular suite also has a configurable algorithm with an embedded database that includes many of the radiative properties, such as wavelength and line width, gas species, and particulate volume fractions. The sensor suite is a monolithic structure that can be mounted in any orientation around the physical process. Sample soot and temperature data from ethylene and propulsion diffusion flames ,and OH concentrations from a hydrogen flame are presented to highlight the capabilities of the sensor suite in characterizing turbulent diffusion flames. In addition, sample surface area densities and drop sizes from a water spray are presented to highlight the capability of the sensor suite to characterize sprays. The data obtained from the sensor suite is validated using data from published literature for flames and using Phase Doppler Interferometry in sprays. The current sensor suite can accommodate flames and sprays that are up to 250 mm in diameter, making it a valuable diagnostic for the propulsion industry.
TFAWS2020-ID-514-Shehata: Performance Evaluation of Reverse Osmosis (RO) Pre-Treatment Technologies for Brackish Ground Water
Author(s): Ali I Shehata, Mohamed Mahmoud, Ismail Ayman abo-bakr, and Mohamed M. Abo Elazm
Desalination of brackish groundwater in Egypt has great potential with respect to the availability of the resource. All major aquifer systems in Egypt contain huge quantities of brackish groundwater. The exploitation of this resource is still limited. With the current cheap price of brackish water desalination, there is a growing interest towards its exploitation. Brackish water RO plants in Egypt confirm the potential of this solution. This paper presents the study of the effect of variation of different operating conditions on the performance of brackish groundwater RO unit. This was achieved experimentally by using brackish water RO (Reverse Osmosis) desalination test rig constructed to simulate environmental conditions and operational parameters for coastal Mediterranean brackish groundwater RO units. Results of experiments at constant feed water parameters showed that: Feed water pressure increases the permeate flow rate and the recovery ratio increase while brine rejected, permeate TDS and specific energy consumption decrease. Feed water TDS increases the permeate flow rate and the recovery ratio decrease while brine rejected, permeate TDS and specific energy consumption increase. Feed water temperature increases the permeate flow rate, permeate TDS and the recovery ratio increase while brine rejected and specific energy consumption decrease. Samples of experimental output parameters were used as ROSA input parameters to check the accuracy of experimental results. However, there were deviations between the experimental results and ROSA results that did not exceed 10 %.
TFAWS2020-PT-300-Anderson: Case Study of Using FLOCAD to Model a Ground Test Station LN2 Heat Exchanger
Author(s): Kevin R. Anderson, Ph.D
This paper will present a case study of using FLOCAD to model the heat transfer and boiling flow behavior of a LN2 ground station equipment heat exchanger. The unique aspect of this work is that is one of very few studies documenting the use of FLOCAD in the spacecraft thermal control community. The status of the state of the work is completed study which used the results of the simulation in order to guide and plan the execution of the thermal vacuum testing of the spacecraft hardware. The paper will review the theory of two-phase boiling flow and correlations used by SINDA/FLUINT as well as the terminology and nomenclature used within Thermal Desktop / FLOCAD regarding two-phase boiling flow heat transfer modeling and simulation. Results for using the ground station heat exchanger as a heat sink in a thermal vacuum test set up are shown in order to demonstrate the set-up and execution of a typical FLOCAD model. Results indicate that properly modeling of the two-phase behavior is critical in order to ascertain the time constant associated with the heat exchanger, as well as understanding the temperature distribution across the test equipment and prediction of required LN2 flowrates to be used during testing. The paper is meant to augment the FLOCAD user’s manual and serve as a tutorial for thermal engineers and analysts wishing to learn and apply FLOCAD to industrial problems.
TFAWS2020-PT-301-Ruel: Thermal Design and TVAC Test Correlation of a Lunar Rover Prototype
Author(s): Jean-Frédéric Ruel, Jean-François Labrecque-Piedboeuf, Josh Newman, Donatas Mishkinis, and Guanghan Wang
The lunar surface thermal environment is particularly harsh amongst planetary bodies in the solar system. Lunar nights last over 14 Earth days, and without a radioactive heat source (RHU or RTG), all components must survive with limited heater power. During the equally long lunar days, constant solar radiation bakes the surface regolith, and the need for solar cells limits real estate for radiators, further constraining the thermal design.
To further develop the thermal design of rovers and other assets destined for the moon, Canadensys Aerospace and Maya HTT partnered with the Canadian Space Agency to carry out the Mobility & Environmental Rover Integrated Technology (MERIT) program. This work included the development and test of a Thermally Regulated Electronics Enclosure (TREE) in a thermal vacuum environment.
To survive this environment, the TREE uses thermally-insulated modules within the rover body. Four thermostatically-controlled loop heat pipes (LHP) developed by Allatherm SIA evacuate the heat during the day, and isolate the modules during the extended nights. Each LHP is equipped with a Bi-metallic Valve Thermostatic Switch (BVTS), a totally passive element which provides system temperature control to switch off the LHPs below a setpoint temperature. Additional insulation is provided by MLI and thermal standoffs.
The TREE assembly was TVAC tested at the CSA’s David Florida Laboratory. The lunar environment was simulated by flooding the TVAC shroud with liquid nitrogen, driving it down to -190°C. Test results showed a better than expected thermal performance during lunar night and that the equipment would well survive. Results from the hot daytime operations provided valuable data for the future development of the loop heat pipe systems, and underscored the challenges of modelling loop heat pipe behavior especially in transient conditions.
Test results were used to correlate the thermal model. The correlation of the lunar night proved to be challenging, with minimal dissipations, high thermal resistances and a cryogenic environment in which the temperatures had not settled after several days. Some imponderables, such as the heat brought in by test harnesses, could not be ignored. Furthermore, the temperature-dependency of the thermal standoffs had to be factored in. The test results were correlated with adequate accuracy, and a lunar night transient simulation provided reliable estimates for the temperatures and power consumption.
TFAWS2020-PT-302-Sahai: Modelling of Lunar Lander’s Thruster’s Exhaust Plume Impingement In Vacuum
Author(s): Mrigank Sahai
TFAWS2020-PT-303-Cannon: Passively Actuated, Triangular Radiator Fin Array
Author(s): Josh R. Cannon, Webin Song, Rydge B. Mulford, and Brian D. Iverson
Thermal control is a challenge for spacecraft as they must maintain internal components within operating limits despite significant fluctuations in external and internal thermal loads. Satellites often rely on active thermal control to manage internal temperatures depending on the thermal environment. However, many of these systems are actively managed, relying on the satellite’s internal electronics to control the radiator’s behavior. The problem of thermal control can be compounded for small satellites, such as CubeSats, which may have high power dissipation per unit surface area, stringent size/weight restrictions, and reduced thermal mass. Passive thermal control is particularly attractive for such small systems, potentially offering increased reliability and simplicity. Efforts to achieve passive, dynamic thermal control of spacecraft radiators has been demonstrated in the literature using louvers actuated by bimetallic coils and radiators deployed by shape memory alloys. In this work, we propose a passive, dynamic thermal control method for CubeSats by using bimetallic coils to deploy an array of four triangular radiator fins that, when folded, comprise the external face of a CubeSat. The advantages of this design include reduced complexity, cost, volume, and weight when compared to traditional deployable radiators in addition to redundancy by using an array of panels. An experimental demonstration of the performance of the proposed design is presented indicating the ability to passively deploy a single radiator fin using custom bimetallic coils at a rate of 2° of angular rotation per 1 °F with minimal hysteresis. A preliminary model of our design indicates the ability to achieve a turndown ratio of greater than 7:1. Experimental and numerical prediction results are presented as motivation for exploration of the proposed design in ongoing work.
TFAWS2020-PT-304-Diebold: Variable View Factor Two-Phase Radiator
Author(s): Jeff Diebold, Calin Tarau, Andrew Lutz, and Srujan Rokkam
During spaceflight missions, a variable view factor radiator can be used to maintain the temperature of electronics within a target band over widely varying power and heat sink conditions. Under a NASA Phase I SBIR program, Advanced Cooling Technologies, Inc. successfully demonstrated a lab-scale prototype of a novel vapor-pressure-driven variable-view-factor radiator two-phase radiator (VVFTPR). The radiator consists of hollow curved and straight panels, filled with a two-phase fluid. An increase in internal vapor-pressure, due to an increase in fluid temperature, results in elastic bending of the curved panel and an increase in view-factor. A lab-scale prototype demonstrated a turndown ratio of thermal resistance to the sink greater than 37:1. While the Phase I prototype was constructed from stainless steel, aluminum alloys offer the potential for improved flexibility and mass savings. This paper extends previous 2D structural simulations to three dimensions. A set of important geometric variables are identified and their influence on the view factor is parametrically investigated. In addition, a thermal model of the variable-view-factor two-phase radiator is introduced and used to demonstrate the passive thermal control capabilities of the concept.
This work has been performed under NASA Small Business Innovation Research (SBIR) Phase II contract 80NSSC18P2187.
TFAWS2020-PT-305-Akka: Cubesats: A Passive Thermal Analysis Approach
Author(s): A. Akka and F. Benabdelouahab
A CubeSat typically consists of a few important subsystems that control attitude determination and control, communication, power, command and data handling, and thermal control. Indeed, regarding this last point Orbital spacecrafts face the problem of high thermal gradients or different thermal loads mediated by differential illumination from the sun. Thermal control of a spacecraft ensures that the temperature of its various parts are kept within their appropriate ranges. The simulation and prediction of temperatures in a spacecraft during a mission are usually carried out by commercial codes. These software packages employ “lumped parameter” models that describe the spacecraft as a discrete network of nodes, with one energy-balance equation per node.
The purpose of the paper is to present the passive thermal control subsystem for a nano-satellite at a precise altitude in the Low Earth Orbit. Miniaturization of components enabled small scale satellite projects, such as the CubeSat, to be used for scientific research in space. Although the integration of compact electronics allowed sophisticated scientific experiments and missions to be carried out in space, the thermal control options for such small satellites were limited.
To minimize the mass of the thermal control subsystem while keeping the electronics at safe operating conditions, this paper presents a study of the thermal environment and passive thermal control system of a nano-satellite using code that develops and markets finite element analysis, used to simulate engineering problems.
The purpose of this work is mainly based on the application of thermal loads, especially, Sun loads, albedo and infrared Earth loads on a simple nano-satellite geometries and accurately simulate the heat flow in it, in order to predict its response to orbital conditions. Thermal mathematical equation is evolving as and when variables are added, like emissivity and absorptivity, to approach real state of space environment.
A transient thermal analysis was also considered to find out the distribution of the temperature, whereas the nano-satellite is on its trajectory. Therefore, it is possible that the internal heat could increase the temperature of the CubeSat such that it will fall within the required operational and survival temperature ranges.
TFAWS2020-PT-306-Bauer: Passive Thermal Coating Observatory Operating In Low-Earth Orbit (PATCOOL)
Author(s): Kevin Bauer
Long-term presence on the moon, mars, and beyond necessitates the transport of liquid oxygen (LOX). Resources are limited in space and LOX not only servers as an oxidizer for fuel, but can also be utilized in the production of breathable air for space habitats. A cryogenic thermal control coating, developed by scientists at Kennedy Space Center (KSC), is getting ready to demonstrate it has the potential to answer these challenges. Aluminum samples coated with the cryogenic thermal control coating and AZ-93 white paint will be launching to the International Space Station (ISS) and deployed on a CubeSat into a low-earth orbit. This work covers the predicted sample temperatures in a simulated space environment and a review of the Thermal Desktop model.
TFAWS2020-PT-308-Koser: Heat Rejection Analysis Process for Early Thermal Assessment
Author(s): Alanna Koser
SNC has developed a Heat Rejection Analysis process for use at the very beginning of space programs or during proposal efforts in order to quantify the heat rejection capability of each spacecraft panel. This analysis is used to provide early identification of likely thermal problems and early inputs on desired spacecraft bus component locations and approximate heater power needs without needing to build a detailed thermal model. This is useful because if thermal engineers begin building their detailed model too early in a program, they end up designing to a moving target. On the other hand, if the detailed thermal model is not started until the spacecraft design has somewhat settled out, this can lead to missed opportunities to get thermal inputs on the design.
This paper will detail the process of building a model for a heat rejection analysis, how to use the results to inform early thermal design inputs, and limitations of the method.
TFAWS2020-PT-309-Taylor: Model Validation for Bigelow Expandable Activities Module (BEAM) with Stowage
Author(s): Sydney Taylor, Zaida Hernandez, and John Iovine
The Bigelow Expandable Activities Module (BEAM) was a collaboration between NASA and Bigelow Aerospace to develop an expandable habitat technology that could be used for future space exploration missions such as the Artemis program. On April 26, 2016, the Bigelow Expandable Activities Module (BEAM) was launched and berthed to the International Space Station on the aft port of Node 3. The present work builds on the previous 2017 model validation to flight data that demonstrated that BEAM could generally accommodate cargo stowage without adversely affect BEAM thermal control, primarily for condensation management. After the originally planned two-year mission life, BEAM was approved for utilization as a stowage module for a 109-cargo transfer bag equivalent (CTBE) to alleviate stowage limitations onboard the ISS. Once stowage was configured in early 2019 model validation efforts resumed. The thermal model revisions included the CTBE stowage and updated CFD-derived heat transfer coefficient for various intra-module ventilation (IMV) flow rates. The coefficients were provided by the Crew and Thermal Systems Division (EC) at NASA JSC and Jacobs Technology. The model is now revalidated and able to predict minimum temperatures with good agreement to flight temperatures (within 1 °C) for both historic and recurring minimum values. Additionally, the model is partially validated for reduced flow rates. With this model, the team was able to provide new flight rule recommendations for condensation and IMV operations management.
TFAWS2020-PT-310-Dwivedi: Modification of Spaceflight Radiator Coating Pigments by Atomic Layer Deposition for Thermal Applications
Author(s): Vivek Dwivedi and Mark Hasegawa
The optical and physical properties of spacecraft radiator coatings are dictated by orbital environmental conditions. For example, coatings must adequately dissipate charge buildup when orbital conditions, such as polar, geostationary or gravity neutral, result in surface charging. Current dissipation techniques include depositing a layer of ITO (indium tin oxide) on the radiator surface in a high temperature process. The application of these enhanced coatings must be such that the properties in question are tailored to mission-specific requirements.
The deposition of thin films by atomic layer deposition is a natural technological fit for manufacturing spacecraft components where weight, conformality, processing temperature, and material selection are all at a premium. Indium oxide (IO) and indium tin oxide (ITO) are widely used in optoelectronics applications as a high quality transparent conducting oxide layer . In this work, we present the thickness-dependent electrical and optical properties of IO thin-films synthesized by ALD with the aim of finding the optimum condition for coating a variety of substrates from Si(100) wafers, glass slides, and especially radiator pigments . Radiators are given surface finishes with high IR emittance to maximize heat rejection and low solar absorptance to limit heat loads from the sun. The surface finish is typically a white paint composed of nano/micron particle sized pigments with a silicate binder. It is the encapsulation of these particles that dictate the charge bleed off properties of the finished coating. Trimethylindium and ozone were used as precursors for IO, while a tetrakis(dimethylamino)tin(IV) source was used for Sn doping to produce ITO. As-deposited IO films prepared at 140°C resulted in a growth per cycle of 0.46 Å/cycle and relatively low film resistivity.
For the case of ITO thin-films, an ALD process supercycle consisting of 1 Sn + 19 In cycles was shown to provide the optimum level of Sn doping corresponding to the 10 wt.% widely reported in the literature. By using the inherent advantage of ALD in coating high aspect ratio geometries conformally, modification of these pigments can be accomplished during coating application preprocessing. The preprocessing is rendered directly on the dry pigment/particle before binding and not on the finished coated radiator geometry thus saving reactor volume.
Samples of our coating were recently launched into space and are currently onboard the International Space Station (ISS) as part of the one-year MISSE-10 materials test mission where the IO coated pigments are exposed to the harsh environment of space.
 T. Asikainen, M. Ritala, and M. Leskela, J. Electrochem. Soc. 142 (1995) 3538
 H. Salami, A. Uy, A. Vadapalli, C. Grob, V. Dwivedi, R. A. Adomaitis, J. Vac. Sci. Tech. A 37 (2019) 010905
TFAWS2020-PT-313-Lutz: Development of High Heat Flux Titanium-Water CCHPs
Author(s): Andrew Lutz, Calin Tarau, and Bill Anderson
CCHPs are the current method used for cooling almost all spacecraft, including NASA, DoD, and commercial satellites. The maximum heat flux for current aluminum-ammonia CCHPs is roughly 10-15 W/cm2. This limit will affect more and more spacecraft electronics systems as electronics continue to increase in power and decrease in size. Traditionally, CCHPs have achieved limited heat flux due to dry-out at the critical heat flux in the evaporator. During previous development, Advanced Cooling Technologies, Inc. (ACT) identified a hybrid wick configuration that allows an increased critical heat flux, and therefore increased maximum heat flux of the aluminum-ammonia CCHP. Under a NASA Phase IIX SBIR program, ACT demonstrated a hybrid wick (with grooves), high heat flux, titanium-water heat pipe capable of maintaining less than 10 K temperature difference from condenser to evaporator at heat flux values up to 90 W/cm2. Aluminum and ammonia were replaced by titanium and water because of a potential testing opportunity inside the ISS. The experiment was performed with the heat pipe operating against gravity to simulate a zero-gravity environment. The experimental performance of the hybrid wick heat pipe was compared to the performance of an otherwise identical baseline titanium-water heat pipe without the hybrid wick to enable high heat flux. The baseline heat pipe exceeded 10 K temperature difference at a heat flux less than 40 W/cm2.
This work has been performed under NASA Small Business Innovation Research (SBIR) Phase IIX contract NNX15CM03C.
TFAWS2020-PT-314-Lee: Fluid Management of Advanced Hot Reservoir Variable Conductance Heat Pipes
Author(s): Kuan-Lin Lee, Calin Tarau, Andrew Lutz, and Bill Anderson
The next generation of Lunar rovers and landers requires variable thermal links to maintain payload temperatures nearly constant over wide sink temperature fluctuations. It has been demonstrated on earth that a hot reservoir variable conductance heat pipe (VCHP) can provide a much tighter passive thermal control capability compared to a conventional VCHP with cold-biased reservoir. However, previous ISS test results revealed that the fluid management of a hot reservoir VCHP needs to be improved to ensure its long-term reliability. Under an STTR Phase I program, Advanced Cooling Technologies, Inc. in collaboration with Case Western Reserve University performed fundamental research to understand the complex transport phenomena within a hot reservoir VCHP. A novel loop VCHP configuration was developed during the program. This loop design allows a net flow to be induced and circulate along the NCG tubing system, which will continuously remove the excessive working fluid from the reservoir (i.e. purging) in a much faster rate compared to diffusion alone. Two potential mechanisms to induce net transport flow were identified:
1. By momentum transfer from vapor to NCG through shearing in the condenser/front region.
2. By filtering the pulses (via a tesla/check valve) generated in the heat pipe section of VCHP loop.
This paper presents the work performed in Phase I to proof the existence of momentum transfer flow (mechanism #1) and its effectiveness on VCHP purging. The work includes theoretical analysis, numerical modeling, prototype development and experimental demonstration.
TFAWS2020-PT-315-Tarau: Thermal Management Concept of Ice Melting Probe for Icy Moon Exploration
Author(s): Calin Tarau, Kuan-Lin Lee, and Bill Anderson
To support NASA future Ocean Worlds Exploration missions, Advanced Cooling Technologies, Inc (ACT) is developing an innovative thermal management concept for a nuclear-powered ice melting probe. The concept consists of multiple advanced thermal features that can offer the most efficient and reliable ice penetration process by maximizing the power fraction used for forward melting and mitigating a series of foreseen challenges related to icy-planetary missions. These thermal features include:
1) pumped two-phase (P2P) loop which collects the waste heat from the cold end of the thermoelectric convertors, transports and focuses the waste heat at the front end of the vehicle for ice melting with minimal thermal resistance
2) front vapor chamber for forward heat focusing and melting
3) variable conductance side walls to enable lateral melting capability (only when the probe gets stuck because of refreezing or other obstacles in its path)
4) side high-pressure liquid water displacement for probe maneuverability and steering
Under an SBIR Phase I program, ACT developed a preliminary full-scale probe design and assessed the technical feasibility of features (1) through (4). A lab-scale ice melting probe prototype with selected features was developed. Ice penetration and thermal behavior of the prototype were experimentally demonstrated in an ice environment system. Functionailties of variable conductance wall and vapor chamber were successfully proven.