Spacecraft Radiators Research Articles

Numerical investigation on high-temperature thermoacoustic heat pump with a work recovery displacer

Spacecraft commonly dissipate heat into space through radiation. In the current development of spacecraft radiators, two major challenges are encountered: effective dissipation of heat in high-temperature environments and the heat waste by the thermal control system. Thermoacoustic heat pumps have emerged as a promising solution, capable of increasing the dissipating temperature of the radiators and reusing the waste heat. This paper presents a novel work-recovery thermoacoustic heat pump (WRTAHP) that incorporates a displacer, which serves the function of phase shifter and acoustic power recovery. One-dimensional numerical simulations are conducted to investigate the influence of the regenerator, thermal buffer tube, heat exchangers, and displacer on the system performance. The results reveal that WRTAHP can raise the temperature of waste heat sources from 50 °C up to 120 °C and obtain 511 W heating capacity with an overall relative Carnot efficiency of 56.4%. Furthermore, with the utilization of the heat pump, the surface area of the radiator is reduced to 60% of its original size. This work demonstrates the potential of WRTAHP for space applications.

Effects of dust attachment on the spectral emittance of spacecraft radiators

In recent years, the method used to collect planetary samples has entailed launching a projectile from a spacecraft onto the surface of a planet at touchdown and collecting the sample raised by the impact. However, there is concern that the dust that is raised at touchdown would adhere to the radiator and affect radiative emissions from the radiator into deep space and radiative reflectance against irradiance from the sun and planets into the radiator. In other words, the dust could affect the thermal control of the spacecraft. Using electromagnetic field analysis, a new evaluation parameter was introduced in this study, and the effect of dust particles on the radiation heat transfer of a SiO2 substrate surface, which is commonly used in spacecraft radiators, was calculated. The electromagnetic field analysis was validated experimentally by spectroscopy. The effects of dust particle size, adhesion, and material on the changes in radiative properties were quantified and analyzed. It was suggested that dust particles could change the radiative properties of the radiator and adversely affect thermal control. This effect increased with increasing particle adhesion.

Effect of Solar Panel on Performance of Spacecraft Body-Mounted Fluid Tube Radiator

Abstract The body-mounted fluid tube radiator (BMFTR) is a highly efficient heat rejection device for spacecraft. However, the heat rejection rate of the BMFTR is negatively impacted by the presence of solar panels mounted on the exterior of the spacecraft. In this study, a heat transfer model for the BMFTR was developed, and a simulation method was created to investigate the effect of solar panels on the radiator’s performance. The accuracy of both the heat transfer model and simulation method was verified using on-orbit data from the China Tianhe module. It was found that external heat is absorbed by the solar panels, which in turn reduces the performance of the radiator. Furthermore, the decrease in the heat rejection rate was quantitatively evaluated, and it was found to be closely related to the spacecraft’s attitude and the view factor between the solar panel and the radiator. The findings of this study on the impact of solar panels on the BMFTR’s performance are meaningful for future research on spacecraft radiators and on-orbit operations.

Optimization design of surface microstructure of high-efficiency space radiation heat dissipation fins

With the continuous progress of deep space exploration, the need to develop high-power spacecraft has become urgent. The mass and volume of high-powered spacecraft radiators account for a large percentage. Therefore, an efficient and lightweight space radiation cooling system is one of the key research directions that need to be developed in the future. In the present study, from the perspective of strengthening the radiant heat flow rate unit mass (Φ/m), the improvement idea of adding “triangular rib”, “arc rib” and “wave rib” types of surface microstructure on the traditional plate radiation fins is proposed. The heat conduction and the radiation process were simulated by COMSOL Multiphysics®. The effects of parameters, such as microstructure thickness, top angle, heat source spacing and environment temperature on index Φ/m were analyzed. The optimal parameter arrangement of the surface microstructure was obtained, and the mechanism was revealed from the view of thermal conductivity and radiation heat dissipation.

Investigation on Thermal Analysis of Spacecraft Radiators

In this research, the main objective is to compare the thermal properties of the rectangular and honeycomb structured space radiators used in spacecraft. The comparison of radiators was done by conducting steady state thermal analysis on these radiators by applying varying heat loads over it to analyse the thermal properties acting over them. The selection of appropriate material for the radiators was based on tensile strength, resistance to high temperature, and the type of working fluid considered. From the simulation results, the honeycomb structures of spacecraft radiator could withstand to a higher temperature gradient, and the rate of heat dissipation was much higher in comparison with rectangular fin type radiator, and hence it can be considered as a great replacement in near future.

Method of providing energy resources to a circumlunar satellite for passing longduration shadow zones

Researches of the possibilities of creating a lunar navigation and communication system have revealed features of the sun's illumination of near-lunar orbits: the annual passage of orbits through a long cycle of about 55 days, containing shadow sections of the orbit from the Moon and a pause of up to 185 days with possible overlays of penumbra and shadow sections of the orbit from the Earth. At the same time, the penumbra and shadow zones from the Earth near the Moon have significant differences in size and can cover the entire orbital grouping of the lunar navigation and communication system. As a result, the problem arises of calculating the energy resources of a circumlunar satellite for passing long-duration shadow zones and maintaining the spacecraft's thermal regime for the period of passing the shadow section of the orbit from the Earth. The energy balance of the spacecraft is modeled for various modes of its operation during the passage of long-duration shadow zones: regular, duty, storage. It is proposed to use blinds to regulate the heat radiation from the spacecraft radiators when passing the shadow sections of the orbit in the considered modes. To reduce the cost of spacecraft mass it is recommended to switch the spacecraft to storage mode, which reduces power consumption in comparison with standby mode. The efficiency of the proposed scheme for passing the shadow zones of the lunar navigation and communication system spacecraft was evaluated for three spacecraft sizes according to the criterion – the minimum amount of mass spent on increasing the energy intensity of the battery and installing blinds.

Experimental demonstration of heat loss and turn-down ratio for a multi-panel, actively deployed radiator

Origami-inspired, dynamic spacecraft radiators have been proposed which utilize an expandable/collapsible surface capable of large variations in emitting surface area. In this work, an experimental prototype of this concept is realized and its performance is analyzed. In particular, we demonstrate the capability of maintaining a spacecraft component at a desired operating temperature through the expansion and contraction of a collapsible radiator to control radiative heat loss. Four aluminum panels are connected via a flexible hinge constructed from interwoven copper wires and suspended from an actuating framework. The radiator panels are connected to a heated aluminum block. The radiator is placed in a vacuum environment with cooled surroundings (173 K) and the total radiative cooling power is determined as a function of radiator actuation position for a constant aluminum block temperature. As the radiator actuates from extended to collapsed, the heat transfer decreases and the fin efficiency increases. For a limited actuation range, the four-panel radiator exhibits a turn-down ratio (largest cooling power / smallest cooling power) of 1.31. A numerical model validated in this work predicts a turn-down ratio of 2.27 for actuation over the full range of radiator positions in surroundings at 4 K. Future revisions that exhibit an increase in panel and hinge thermal conductivities and utilizing eight panels would yield a turn-down ratio of 6.01. Assuming infinite thermal conductivity and infinite hinge conductance, the turn-down ratios for two, four and eight panel radiators, respectively, are 2.00, 3.98, and 7.92.

Coupled behavior of shape memory alloy-based morphing spacecraft radiators: experimental assessment and analysis

Thermal control is an important aspect of spacecraft design, particularly in the case of crewed vehicles, which must maintain a precise internal temperature at all times in spite of significant variations in the external thermal environment and internal heat loads. Future missions beyond low Earth orbit will require radiator systems with high turndown ratios, defined as the ratio between the maximum and minimum heat rejection rates achievable by the radiator system. Current radiators are only able to achieve turndown ratios of 3:1, far less than the 12:1 turndown ratio requirement expected for future missions. An innovative morphing radiator concept uses the temperature-induced phase transformation of shape memory alloy (SMA) materials to achieve turndown ratios that are predicted to exceed 12:1 via substantial geometric reconfiguration. Developing mathematical and computational models of these morphing radiators is challenging due to the strong two-way thermomechanical coupling not present in traditional fixed-geometry radiators and not widely considered in the literature. Although existing simulation tools are capable of analyzing the behavior of some thermomechanically coupled structures, general problems involving radiation and deformation cannot be modeled using publicly available codes due to the complexity of modeling spatially evolving boundary fields. This paper provides important insight into the operational response of SMA-based morphing radiators by employing computational tools developed to overcome previous shortcomings. Several example problems are used to demonstrate the novel radiator concept. Additionally, a prototype morphing radiator was designed, fabricated, and tested in a thermal environment compatible with mission operations. An associated finite element model of the prototype was developed and executed. Model predictions of radiator performance generally agree with the experimental data, giving confidence that the tools developed are able to accurately represent the thermomechanical coupling present in morphing radiators and that such tools will be useful in future designs.

Исследование применимости технологии лазерного управляемого термораскалывания для изготовления элементов термооптического покрытия радиаторов космических аппаратов

In view of a responsible destination and hard operation conditions strong technical requirements are made to glass ele-ments of a thermo-optical coating for spacecraft radiators where a basic requirement of them is absence of chips and micro-cracks. There are carried out investigations of the influence of laser radiation parameters upon end face quality in the in glass element obtained through the method of controlled thermo-splitting. A quality considerable increase is shown in the surfaces of division at the use of the method of the end-to-end laser controlled thermo-splitting in comparison with the methods of part-through laser controlled thermo-splitting and scribing with a diamond cutter with the further after-break.

Thermal Vacuum Evaluation of Simulated Spacecraft Radiators with Discretized Emissivity Surface Properties

Incorporating variable emissivity electrochromic devices onto spacecraft radiators offers a unique potential for modulating passive heat rejection, but implementation challenges exist. Although high-/low-end states of these devices are readily achievable, uncertainties remain with reproducibility at intermediate states and also with stability in a thermal vacuum environment. An average intermediate heat rejection rate can be obtained by discretizing the radiator surface into mixed high- and low-emissivity values. We emulated this capability by constructing test articles with two fixed-emissivity states divided into four sections. Coupons were constructed from aluminum 6061 and stainless steel 304 to characterize performance variations resulting from differences in thermal conductivity. Tests were devised to maintain either a constant surface temperature or constant heat flux. The results showed that this approach provided a predictable area-averaged intermediate emissivity regardless of the material’s thermal conductivity or the heat rejection scheme used. When operating in a constant flux mode, however, the stainless steel coupon experienced larger lateral temperature gradients across the surface due to its lower thermal conductivity. Performance of a variable emissivity radiator must, therefore, take into account not only surface properties, but also consider the desired system heat rejection control scheme and localized thermal gradient tolerance.

Shaded Spacecraft Radiators to Be Used on the Daytime Surface of the Mercury Planet, the Moon, and Asteroids of the Solar System Inner Part

During the daytime a surface of the Moon, Mercury planet, and asteroids of the Solar system inner part, significantly heats up, and infrared radiation of the local soil becomes essential. At the same time direct solar radiation and reflected from the surface solar radiation reach the maximum too. These radiation fluxes can significantly decrease the efficiency of spacecraft radiators in the daytime. This effect is especially strong on the Mercury surface where direct solar radiation is 10 times stronger than solar radiation near the Earth. As a result, on the daytime surface of the Mercury the conventional low-temperature radiators become completely disabled. The article describes the development of the special shaded spacecraft radiators to be used in daytime on the Mercury and other atmosphereless bodies of the Solar system inner part. To solve this task are used mirror shades. The shape of these shades is developed to improve operation conditions of the spacecraft radiator through the appropriate scheme of radiation reflection. The task is discussed in 2D and 3D cases. A new design of shaded spacecraft radiators is proposed, and reasonable proportions of radiators are determined. The performance capability of proposed radiators for environments of the Mercury and the Moon is estimated using the zonal method in view of partial mirror reflection. The calculations showed that the developed shaded spacecraft radiators are capable to work on the Mercury surface as the low-temperature radiators even during the daytime. New radiators provide minimum accepted operating temperature of 241К (-32°С), meanwhile radiators of common design have minimum operating temperature of 479К (206°С). Using such radiators on the Moon enables us to increase effectiveness of spacecraft radiators and to decrease their minimum operating temperature from 270К (-3°С) to 137К (-136°С).

Node-based spacecraft radiator design optimization

Spacecraft radiators can be designed through thermal analysis of a thermal model divided into nodes. The radiator is thus designed discretely in unit nodes; then, the radiator node distribution over the node division of a candidate radiator region indicates the radiator design as radiator node combinations. In particular, the radiator sizes and the topologies of shapes and locations are key design factors for efficient thermal design. These design factors can be considered, to some extent, at the typical resolution levels for the node division of the thermal model. This paper proposes two radiator design optimization methods that are based on node division of the thermal model; these methods find the optimal solutions of radiator node combinations in different ways. The first method uses an integrated optimization analysis that combines an optimization algorithm with thermal analysis; binary design variables are assigned to each node division to represent the radiator node combination and serve as the interface between two sets of software. The optimization problem is formulated as a multi-objective problem and improved through thermal design heuristics. The second method is a stepwise approach that adds a radiator node with the highest temperature sensitivity until the temperature limits are satisfied. A thermal model of a small spacecraft was developed to verify the proposed optimization methods, and test problems of various versions of the thermal model were appropriately defined. The numerical optimal solutions for the test problems using these methods showed good agreement with the analytic solutions. Therefore, the applicability and feasibility of the present methods for practical radiator design were confirmed.

Optimum Design of Spacecraft Radiators With Longitudinal Rectangular and Triangular Fins

In the present study the optimum dimensions of longitudinal rectangular and triangular radiating fins with mutual irradiation are determined. The basic assumptions are one-dimensional heat conduction and gray diffuse surface radiation. The governing equations are formulated by means of dimensionless variables and solved numerically in order to carry out the required minimization procedure. The optimum fin dimensions, thickness and height, are presented in generalized dimensionless form and correlations are provided in order to assist the spacecraft thermal systems designer. The results are analyzed and expressed in explicit correlations. Several diagrams, are also included, that give insight to the operational characteristics of the heat rejection mechanism. Moreover, special attention is given to the error analysis of the numerical methods used, since the accuracy and the reliability of the algorithms employed for the solution of the integro-differential equation is important for the calculation of the heat dissipation at the fin base and its subsequent optimization.

Tube-wall fin effects in spacecraft radiators

Tube-wall fin effects in spacecraft radiators