Spacecraft Thermal Control Applications Research Articles

Experimental Investigation of the Effect of Phase Change Material in Mitigation of Heat

The use of a latent heat storage system using phase change materials (PCMs) is an effective way of storing thermal energy and has the advantages of high-energy storage density and the isothermal nature of the storage process. PCMs have been widely used in latent heat thermal storage systems for heat pumps, solar engineering, and spacecraft thermal control applications. The uses of PCMs for heating and cooling applications for buildings have been investigated within the past decade. There are large numbers of PCMs that melt and solidify at a wide range of temperatures, making them attractive in a number of applications. This paper also summarizes the investigation and analysis of the available thermal energy storage systems incorporating PCMs for use in different applications.

Enhancing infrared emissivity of GdCoO3 with Ca doping: Potential for advanced thermal control materials

The high infrared emissivity material Gd1-xCaxCoO3 was synthesized using the sol-gel method. The structure and composition of Gd1-xCaxCoO3 were investigated through X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and Fourier transform infrared spectroscopy (FTIR). Scanning Electron Microscopy (SEM), Energy Dispersive X-ray Spectroscopy (EDS), specific surface area analysis, Brunauer-Emmett-Teller (BET) method for void analysis, and Ultraviolet-Visible-Near-Infrared (UV-Vis-NIR) diffuse reflection spectrum were employed to analyze the surface morphology, elemental composition, specific surface area, pore size distribution, and band gap of the prepared powders. The average infrared emissivity of samples with different doping concentrations at various temperatures (8-14 μm and 3-5 μm) was determined using a dual-band emissivity meter. At room temperature, the infrared emissivity of the doped powders is generally higher, exceeding 0.75 in comparison to the undoped sample powder. As the test temperature increases, the infrared emissivity of all samples shows a significant rise. The infrared emissivity of all samples surpasses 0.91 at 500 °C, with the emissivity of the samples reaching as high as 0.988-14μm (0.993-5μm) with a Ca doping concentration of 5 %. These findings indicate that Ca-doped GdCoO3 powder represents a promising high-emissivity material with broad potential in spacecraft thermal control applications.

Flat Absorber Black PEO coatings on Ti6Al4V for spacecraft thermal control application

Black appearance and flat absorber, i.e., high solar absorptance (αs) and high IR emittance (εir) surfaces, are essential for optical benches and optical mounts in astronomical and scientific payloads/spacecraft. Generally, these optical benches and optical mounts are fabricated by Ti6Al4V alloy due to its superior mechanical and thermal properties. However, bare Ti6Al4V is restricted for spacecraft thermal control applications due to its low emittance, intermediate absorptance, and moderate corrosion resistance behaviors. Hence, plasma electrolytic oxidation (PEO) technique was utilized to develop black and flat absorber coatings on bare Ti6Al4V alloy. Sodium silicate (SS), sodium hypophosphate (SHP), and potassium fluoride (KF) were used for the preparation of the electrolytic bath. Process parameters such as current density, duty cycle, frequency, the concentration of electrolytes, and duration were judiciously altered to get uniform PEO coatings with the flat absorbing property. Six numbers of PEO coatings were finally chosen for further in-depth characterizations as they showed adequate flat absorbing property. The phase composition, microstructure, roughness, and wettability of those PEO coatings were thoroughly studied by X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), profilometry, and water contact angle measuring techniques, respectively. Thermo-optical properties viz., εir and αs of the coatings were recorded by portable IR emissometer and solar reflectometer, respectively, and electrical sheet resistance was measured by two probe method. The Nanomechanical properties of the coatings, such as modulus (E) and nanohardness (H), were evaluated by the nanoindentation technique. The PEO coatings were also investigated with respect to potentiodynamic polarization to investigate corrosion resistance of the PEO coatings. The highest εir value of PEO coating was achieved as 0.87 for a 20% duty cycle with a combination of SS + SHP electrolytes, while the maximum αs value was achieved as 0.83 for the same 20% duty cycle with a combination of SS + SHP + KF electrolytes.

Analytic characterization and operational limits of a hybrid two-phase mechanically pumped fluid loop based on the capillary pumped loop

Two-phase mechanically pumped fluid loops have the potential to provide numerous benefits for spacecraft based applications. Here a hybrid two-phase capillary and mechanically pumped fluid loop that shows promise for spacecraft thermal control applications is analyzed and its operational limits are characterized. Data from an experimental system that incorporates a 3D printed evaporator is correlated to several models that together provide a comprehensive characterization of the system behavior. The loop performance is analyzed using pointwise as well volume-averaged governing equations and resistance network models, to predict flooding and dryout limits. Also, system-level numerical (including 3-D CFD simulations) transient and linear-response analyses are performed predicting the changing loop phase distributions and the observed time-dependent behavior. With the 3D-printed evaporator, a notably high evaporator conductance of 30 W/cm2-K and heat flux over 10 W/cm2 over large area are achieved with negligible temperature non-uniformity.

Silicate Spray-Coated Nickel-Plated Titanium Alloy for Space Applications: Corrosion Resistance and Thermo-optical Properties

An inorganic silicate black spray coating (BSC) is employed on the blackened electroless nickel (ENB)-plated Ti-6Al-4V to enhance thermo-optical properties as well as corrosion resistance for use in spacecraft thermal control applications. The composite coating (BSC-coated ENB) is characterized with respect to impedance spectroscopy and potentiodynamic polarization to evaluate corrosion resistance. The results indicated that the corrosion resistance of the ENB specimen could be improved by post-spray coating due to reduction in porosity rate from 8.4 to 1.7. Further to ascertain the space worthiness of the composite coating, thermo-optical properties before and after the environmental tests (humidity, thermo-vacuum and thermal cycling tests) were measured. The composite coating showed a marked enhancement in solar absorptance (αs≥ 0.94) and infrared emittance (eIR≥0.84) values as compared to ENB specimen. Hence, the proposed composite coating demonstrated greater potential to be used in advanced thermal control applications in spacecraft where enhanced corrosion resistance and thermo-optical properties are essential.

Space qualification and characterization of high emittance black nickel coating on copper and stainless steel substrates

Black nickel coatings exhibiting high infrared emittance were developed on copper and stainless steel substrates by pulse electrodeposition using a modified Fishlock bath. The uniform jet black coating is intended to provide passive thermal control of spacecraft components. Space worthiness of the coating was evaluated by conducting a series of space environmental tests such as humidity, thermal stability, thermal cycling and thermo-vacuum performance tests. The thermo-optical properties namely solar absorptance (αS) and infrared emittance (εIR) of the coatings were measured before and after each environmental test. No significant change in thermo-optical properties was observed after environmental tests showing their high stability for spacecraft thermal control applications. The coatings were characterized by cross-sectional SEM and EDX, XRD, XPS, Nanoindentation and Nano Vision analysis. X-ray diffraction pattern reveals the amorphous nature of the coating with possible presence of ZnS. XPS analysis confirms the chemical and electronic state of the elements. Average modulus and hardness of the coating was recorded using Nanoindentation method and a high resolution 3D image of the surface was generated using Nano Vision scan.

Flat Absorber Coating for Spacecraft Thermal Control Applications

SolarBlack is a bone-char-based surface developed as a flat absorber (black) thermal control surface for use on spacecraft. The surface, originally developed for use on the front shield of “ESAs” Solar Orbiter, is deposited using a technique known as CoBlast, developed by ENBIO Ltd. The resulting surface makes use of the material’s highly stable ratio of solar absorptance to near-normal thermal emissivity () as well as its low electrical resistivity to regulate both temperature and electrostatic dissipation in service. SolarBlack is suitable for use on rigid and flexible metallic substrates, including titanium, aluminum, copper, stainless steel, nitinol, Inconel, and magnesium alloys. This work describes the thermo-optical properties, stability, and qualification of this surface for use on spacecraft components, as well as material characterization of the coating and bone char itself. The thermooptical stability of SolarBlack was determined using the Synergistic Temperature Accelerated Radiation facility space environment simulator in the European Space Research and Technology Centre, having previously qualified for use on Solar Orbiter. Material characterization was carried out using simultaneous thermal analysis, scanning electron microscopy, ultraviolet/visible/near-infrared spectrometry, and infrared emissometry.

Solar Water Distillation Using Three Different Phase Change Materials

In recent years with the exacerbation of energy shortage, water crisis increases around the world. With the continuous increase in the level of greenhouse gas emissions, the use of various sources of renewable energy is increasingly becoming important for sustainable development. Due to the rising oil price and environmental regulations, the demand of utilizing alternative power sources increased dramatically. Alternative energy and its applications have been heavily studied for the last decade.Energy and water are essential for mankind that influences the socioeconomic development of any nation. Pure water resources become more and more scarce every day as rivers, lakes wells and even seawater pollution rapidly increases. Solar energy is one promising solution to secure power and potable water to future generation. The process of distillation can be used to obtain fresh water from salty, brackish or contaminated water. Water is available in different forms such as sea water, underground water, surface water and atmospheric water. Clean water is essential for good health.The search for sustainable energy resources has emerged as one of the most significant and universal concerns in the 21st century. Solar energy conversion offers a cost effective alternative to our traditional usages. Solar energy is a promising candidate in many applications. Among the alternative energy sources used for electricity production, wind and solar energy systems have become more attractive in recent years. For areas where electricity was not available, stand alone wind and solar systems have been increasingly used.The shortage of drinking water in many countries throughout the world is a serious problem. Humankind has depended for ages on river, sea water and underground water reservoirs for its fresh water needs. But these sources do not always prove to be useful due to the presence of excessive salinity in the water. To resolve this crisis, different methods of solar desalination have been used in many countries. Distillation is a well known thermal process for water purification, most importantly, water desalination. Most of the conventional water distillation processes are highly energy consuming and require fossil fuels as well as electric power for their operation.Single basin solar still is a popular solar device used for converting available brackish or waste water into potable water. Because of its lower productivity, it is not popularly used. Numbers of works are under taken to improve the productivity and efficiency of the solar still.There are large numbers of PCMs that melt and solidify at wide range of temperatures, making them attractive in a number of applications. PCMs have been widely used in latent heat thermal storage systems for heat pumps, solar engineering and spacecraft thermal control applications. The use of PCMs for heating and cooling applications for buildings has been investigated within the past decade. The experimental results computed in the field of water distillation process using solar energy in the presence of energy storage materials Potassium Dichromate (K2Cr2O7),Sodium Sulphate(Na2SO410H2O) and Sodium Acetate (CH3COONa) are discussed in this paper.

Solar Water Distillation Using Two Different Phase Change Materials

In recent years with the exacerbation of energy shortage, water crisis increases around the world. With the continuous increase in the level of greenhouse gas emissions, the use of various sources of renewable energy is increasingly becoming important for sustainable development. Due to the rising oil price and environmental regulations, the demand of utilizing alternative power sources increased dramatically. Alternative energy and its applications have been heavily studied for the last decade. Energy and water are essential for mankind that influences the socioeconomic development of any nation. Pure water resources become more and more scarce every day as rivers, lakes wells and even seawater pollution rapidly increases. Solar energy is one promising solution to secure power and potable water to future generation. The process of distillation can be used to obtain fresh water from salty, brackish or contaminated water. Water is available in different forms such as sea water, underground water, surface water and atmospheric water. Clean water is essential for good health. The search for sustainable energy resources has emerged as one of the most significant and universal concerns in the 21st century. Solar energy conversion offers a cost effective alternative to our traditional usages. Solar energy is a promising candidate in many applications. Among the alternative energy sources used for electricity production, wind and solar energy systems have become more attractive in recent years. For areas where electricity was not available, stand alone wind and solar systems have been increasingly used. The shortage of drinking water in many countries throughout the world is a serious problem. Humankind has depended for ages on river, sea water and underground water reservoirs for its fresh water needs. But these sources do not always prove to be useful due to the presence of excessive salinity in the water. To resolve this crisis, different methods of solar desalination have been used in many countries. Distillation is a well known thermal process for water purification, most importantly, water desalination. Most of the conventional water distillation processes are highly energy consuming and require fossil fuels as well as electric power for their operation. Single basin solar still is a popular solar device used for converting available brackish or waste water into potable water. Because of its lower productivity, it is not popularly used. Numbers of works are under taken to improve the productivity and efficiency of the solar still. There are large numbers of PCMs that melt and solidify at wide range of temperatures, making them attractive in a number of applications. PCMs have been widely used in latent heat thermal storage systems for heat pumps, solar engineering and spacecraft thermal control applications. The use of PCMs for heating and cooling applications for buildings has been investigated within the past decade. The experimental results computed in the field of water distillation process using solar energy in the presence of energy storage materials sodium sulphate and sodium acetate are discussed in this paper. Keywords: solar energy, saline water, distillation, phase change material.

Development of Novel Polymer Phase Change Material for Heat Storage Application

Polymer Phase change material (PCM's) are materials used to store Energy for a broad range of Applications. Unlike conventional storage materials, PCM absorbs and release heat at a nearly constant temperature. They store 5–14 times more heat per unit volume than sensible storage materials. Increasing demand in solar engineering and spacecraft thermal control applications; require the continuous development of such materials to maximize its efficiency. One of the options is to develop energy storage devices, which are as important as developing new sources of energy. In This paper we can show that combination of low Density Polyethylene (LDPE) paraffin wax and glycerin is an alternative material that can be used as PCM's. Differential Scanning Calorimeter (DSC); Melt Flow Index test and FTIR technique were used to characterize the new developed Compound. Results obtained indicate that a reduction of more than 10°C in melting temperature (Tm) of the pure LDPE-resin was achieved.

Studies on black electroless nickel coatings on titanium alloys for spacecraft thermal control applications

A process of blackening of electroless nickel coating is investigated to produce ultra black coating on titanium alloys with higher optical properties. Process optimization was carried out by investigating the influence of various operating conditions, namely, processing time of etching solutions, thickness of electroless nickel deposit, temperature of blackening solutions, and pH of electroless nickel solution on the physico-optical properties of the black coating. It was observed that an optimum thickness of 35 + 5 μm of electroless nickel is required to achieve the ultra high optical properties after blackening. Energy dispersive X-ray spectroscopy studies suggested that films containing ~7% phosphorous are good for further blackening. Scanning electron and optical microscopic studies confirmed that the surface morphology played the major role to get the ultra high optical properties. The environmental tests, namely, humidity, corrosion resistance, thermal cycling, thermo vacuum performance, and thermal stability tests were used to evaluate the space worthiness of the coating. Optical properties of the coating were measured before and after each environmental test to ascertain its stability. The blackened electroless nickel provides higher optical properties in the order of ~0.85; this coating has good adhesion, uniformity, and stability in adverse space conditions. Hence, these coatings were extremely suitable for spacecraft thermal control applications.