Bum-Seok Hyun

The Correlation of Satellite Thermal Mathematical Model using Results of Thermal Vacuum Test on Structure-Thermal Model

Because thermal design of satellite carrying out mission in space is performed by thermal analysis result using thermal mathematical model, accuracy of thermal mathematical model is important and it can be improved by model correlation. Correlation steps of satellite thermal math model are composed of modeling of satellite configuration placed in thermal vacuum chamber, verification of correspondence between thermal math model and real satellite configuration, and adjustment of modeling parameters from major part to minor part etc. In this study, correlation success criteria was established and correlation for satellite thermal math model was performed using result of thermal vacuum test of satellite structure-thermal model to meet the success criteria. The overall results satisfied the criteria and this correlated thermal model was applied for detailed thermal design of satellite.

Study on the Thermal Radiation Performance of the Multi-functional Structure Made of the Carbon Fiber Composite Material

The design strategy of the multi-functional structure is that the electrical components and the circuits are directly put on their supporting structural panel in which the radiation shields and the thermal control functions are integrated. Applying the multi-functional structure reduces the total mass and size of the space system and makes it possible to lower launch cost. In present study the performance of thermal radiation for six types of multi-functional structure are investigated by the numerical method. The effect of the rib configuration on heat transfer for the multi-functional-structure is not important alone but is meaningful considering with the structural stiffness, difficulty of manufacturing and mass increase. In heat spreading point of view, the thickness of the outer conductive layer is important rather than the rib configuration and the trade-off study with the mass and thickness is required for optimum design.

Conceptual Design of Multi-Functional Structure using Rectangular Grid-Stiffened Structure for Satellite

The MFS (Mlti-Functional Structure) concept, which integrates the electronics, thermal control and structure into a single packaging system, has been developed and applied to reduce the volume and weight of the satellite. Therefore, this MFS can eliminate the bulky chassis/frames, cables and connectors of the electronic equipment. The main point of this traditional MFS is the replacement of the electrical chassis/frames with MCMs (Multi-Chip Modules) that require much costs and efforts for developing. This paper shows the new MFS concept that effectively saves the volume and weight. The structure including the thermal control and radiation shielding elements will be designed and manufactured as the rectangular grid-stiffened structure. The rectangular grid-stiffened structure is the modification of the iso-grid structure, and provides the enough spaces for putting the general PCBs without the chassis/frames.

An Investigation in the Thermal Effect on a Low Earth Orbit Satellite under Yaw Motion for the Visibility of a Star Sensor

Thermal condition according to the operation attitude of a satellite in orbit would be essential to be known because the orbit attitude is a dominant factor to affect satellite thermal design. In this paper, the change in space thermal environment and the thermal effect in thermal design are studied for a low earth orbit satellite according to the yaw motion. The present satellite retains sun-pointing attitude during daylight due to the fixed type solar arrays. And it also moves along the orbit with constant yaw motion in a longitudinal axis so that a star tracker which is a star sensor for satellite`s attitude control always looks into the deep space. This attitude is considered in its better visibility to the stars for a successful mission operation. Also, it is required to access the corresponding thermal effects due to the yaw motion. Therefore, we try to verify these by the thermal analysis for the satellite thermal model with the yaw motion.

Numerical Study on the Thermal Control Device for Satellite Components Using the Phase Change Material Combined with Heat Pipe in Parallel

ABSTRACT The thermal control device for the periodic working component combinedsolid-liquidphasechangematerial(PCM)withheatpipesisdesignedandnumericallystudied.Duetohighlatentheatandretainingconstanttemperatureduringmeltingprocess the component peak temperature, not withstanding small radiator size, isreduced. The warm-up heater power consumption to keep the minimum allowedtemperature is also cut down since the accumulated thermal energy is releasedthroughthesolidification.Thethermalbuffermass(TBM)madeofAlcangivethesimilareffectbutthemassandpowerconsumptionofwarm-upheatershouldincreasecompared to PCM. The amount of PCM can be optimized depending on thecomponentheatdissipationandon/offdutytime. 초 록 주기적단속적으로작동하는위성부품의열제어를위하여고상-액상상변화물질(PCM,PhaseChangeMaterial)과열관을병렬로결합한열제어장치를제안하였으며,이의성능을수치해석을통하여검증하였다.상변화중큰잠열과일정하게유지되는온도에의하여작은방열판면적에서도부품의최고온도를제어할수있으며,냉각기에는PCM에축적된에너지가방출됨으로써보온히터소모전력을절약할수있다.동일한형태의AlTBM(ThermalBufferMass)을사용하면비슷한효과를기대할수있으나,질량과보온히터의소모전력이증가하므로PCM에비하여비효율적이다.설계된PCM열제어장치는발열량과작동시간에따라그양을최적화할수있다.KeyWords:PhaseChangeMaterial(상변화물질),Heatpipe(열관),LatentHeat(잠열)

Study on the Satellite Thermal Control Hardware Composed of Two Parallel Channels Working for Heat Pipe and Phase Change Material

ABSTRACT The satellite thermal control H/W composed of two parallel channels working for heat pipe (HP) and phase change material (PCM) is suggested for the high heat dissipating component which works intermittently with short duty. In a limited point of view, the HP-PCM device is a kind of off-the-shelf component that requires no dedicated configuration and thermal designs to PCM. Therefore, it can be used with less impact on the program cost and schedule different from most of the PCM applications. In present study the typical honeycomb structure radiator applying the HP-PCM device is designed and the detail thermal math model is developed for numerical analyses. The result comparison between without and with PCM shows that the HP-PCM device redistributes the peak heat around the whole mission period through the alternate melting and freezing of PCM, and, as a result, the maximum and minimum temperatures are effectively alleviated. The drawback of PCM application due to low thermal conductivity can be successfully resolved by means of parallel arrangement of HP channel.

Investigation on Thermal Effect for a Low Earth Orbit Satellite during Imaging Maneuvering

A low earth orbit satellite with a fixed solar array always has a sun-pointing attitude during daylight, and changes into a nadir-pointing attitude for a imaging mission. Since external heating sources to the satellite panels are Earth irradiation and Albedo during most of daylight in a sun-pointing attitude, the thermal environment condition is relatively stable. However, direct sunlight which is the greatest environmental heating has an affect on the satellite panels during a mission period (10% of one orbit) in a nadir-pointing attitude. In satellite thermal design, thermal effects of a nadir-pointing mission attitude due to this thermal environment change need to be evaluated although the duration of a nadir-pointing attitude is short. Therefore, a nadir-pointing attitude during a mission is incorporated into thermal model and by the thermal analysis result, thermal effects on the satellite are investigated.

Thermal Analysis on a Satellite Box during Launch Stage by Analytical Solution

Simple methods are developed to predict temperatures of a satellite box during launch stage. The box is mounted on outer surface of satellite and directly exposed to space thermal environment for the time period from fairing jettison to separation. These simple methods are to solve a 1st order ordinary differential equation (ODE) which is simplified from the governing equation after applying several assumptions. The existence of analytical solution for the 1st order ODE is determined depending on treatment of time-dependent molecular heating term. Even for the case that the analytical solution is not available due to the time dependent term, the 1st order ODE can be solved by relatively simple numerical techniques. The temperature difference between two different approaches (analytical and numerical solutions) is relatively small (Jess than along the time line) when they are applied to STSAT-I launch scenario. The present methods can be generally used as tools to quickly check whether a satellite box is safe against space environment during the launch stage for the case that the detailed thermal analysis is not available.