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This paper experimentally and analytically evaluates the heat rejection/retention performance of a reversible thermal panel (RTP) which can autonomously change thermal performance depending on its own thermal conditions. The RTP is considered as a candidate methodology for thermal control of Venus mission, PLANET-C, in order to save survival heater power. An RTP prototype was tested and evaluated. An analytical thermal model of the RTP was also developed, and basic performances of the RTP were evaluated. Thermal performance of the RTP when applied to the longwave camera (LIR) of the PLANET-C was evaluated with an analytical thermal model as functions of fin deployment directions and rear surface properties of the RTP's fin. The analytical results showed that the RTP can save heater power in comparison to a conventional radiator.

A lightweight 100 W-class deployable radiator with environment-adaptive functions has been investigated. This radiator - Reversible Thermal Panel (RTP) - is composed of flexible high thermal conductive materials and a passive reversible actuator, and it changes its function from a radiator to a solar absorber by deploying/stowing the reversible fin upon changes in the heat dissipation and thermal environment. The RTP is considered one of the candidates of thermal control methodology for the Japanese Venus mission “Planet-C”, which will be launched in 2010 to save its survival heater power. In this paper, design and fabrication of the RTP proto-model (PM) and the test results of deployment/stowing characteristics in an atmospheric condition are reported. Thermal performance estimation with thermal analytical model of the RTP PM is also presented.

This paper describes a new passive thermal control device-a Reversible Thermal Panel (RTP)-which changes its function reversibly from a radiator to a solar absorber by deploying/stowing the radiator/absorber reversible fin. The RTP consists of Highly Oriented Graphite Sheets (HOGSs), which have characteristics of high thermal conductivity, flexibility and light weight, as thermal transport units, which can transport the heat from equipment to reversible fin, and of a Shape - Memory Alloy (SMA) as a passively rotary actuator to deploy/stow the reversible fin. The RTP prototype model was designed and fabricated using HOGSs, a honeycomb base palate, and a prototype reversible rotary actuator. The heat rejection performance of the RTP as a radiator and the heat absorption performance as an absorber were evaluated by thermal vacuum tests and thermal analyses. The autonomous thermal controllability achieved using the prototype rotary actuator was also evaluated.

New thermal control material named Smart Radiation Device (SRD) has been studied to apply for spacecraft. Infrared radiative properties of the SRD change depending on its own temperature without electrical or mechanical instruments. The SRD however shows too high solar absorptance to apply it as a radiator. To overcome such drawback, it is necessary to design and apply the mutilayer films on the SRD for reflecting solar radiation, keeping infrared radiative properties of the SRD. To perform optimum design of the multilayer films, the genetic algorithm (GA) was employed. In this paper, we propose a design of the thermal radiative properties of the SRD with the multilayer films.

A method for measurement of total hemispherical emittance of metals at cryogenic temperatures is described. The principle of the measurement is based on calorimetric method and total hemispherical emittance as a function of temperature is obtained by measuring the equilibrium temperature of a specimen corresponding to different heat input, which is given to a heater attached to the specimen. Measurements of total hemispherical emittance and specific heat have been carried out on the specimen of lead over a temperature range of 10∼40 K. In order to verify the measurement method, uncertainty on heat loss is discussed.