• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.40 no.5
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• pp.439-445
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• 2012

The COMS(Communication, Ocean, and Meteorological Satellite) is subjected to shock loads when the stage or fairing of a launch vehicle is separated and the satellite is separated from the launch vehicle during the launch vehicle flight. And, after the satellite is separated from the launcher, the COMS is subjected to shock loads when the solar array is deployed, Ka-Band communication antenna is deployed, and meteorological imager radiator cover is released. In order to validate the satellite safety against these shock loads on ground, shock tests were performed. In this paper, the shock tests performed in the course of the COMS development are described, and the method to assess the test result is presented with an example of Geostationary Ocean Color Imager(GOCI). In Ariane-5 launch vehicle, the clampband release shock for satellite separation is lower than the fairing or stage separation. In this paper, the extrapolation method to take into account the maximum shock load from the launch vehicle by using the satellite separation shock test result is also introduced.

• Journal of Aerospace System Engineering
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• v.13 no.3
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• pp.78-86
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• 2019

This paper describes the stiffness optimization of the torsion spring hinge of the large SAR antenna considering the deployment performance. A large SAR antenna is folded in a launch environment and then unfolded when performing a mission in orbit. Under these conditions, it is very important to find the proper stiffness of the torsion spring hinge so that the antenna panels can be deployed with minimal impact in a given time. If the torsion spring stiffness is high, a large impact load at the time of full deployment damages the structure. If it is weak, it cannot guarantee full deployment due to the deployment resistance. A multi-body dynamics analysis model was developed to solve this problem using RecurDyn and the development performance were predicted in terms of: development time, latching force, and torque margin through deployment analysis. In order to find the optimum torsion spring stiffness, the deployment performance was approximated by the response surface method (RSM) and the optimal design was performed to derive the appropriate stiffness value of the rotating springs.

• Journal of Aerospace System Engineering
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• v.17 no.2
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• pp.86-93
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• 2023

Pyrotechnic separation devices have been widely used as holding and release mechanism for deployable appendage. However, pyro-shock can cause temporal or permanent damage on shock sensitive components such as electronics, mechanism, and brittle components. This study proposed a low-stiffness blade based passive shock absorber using a multi-layered stiffener laminated with viscoelastic acrylic tapes for reducing transmitted pyro-shock upon explosion of pyrotechnic separation devices. The multi-layered structure with viscoelastic tape has high-damping characteristics to effectively secure structural integrity of low-stiffness blades under the launch environment. The design effectiveness was verified through a shock test by dropping a pendulum. The structural integrity of the shock absorber under a launch environment was evaluated through structural analysis under load conditions with a deployable payload.

• Journal of Korean Society of Steel Construction
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• v.12 no.6
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• pp.639-648
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• 2000

A model analysis is used to predict the impact response of a simply supported elastic circular cylindrical shell composed of two bonded isotropic layers. The governing equations for a two-layered cylindrical shell are derived on the basis of an improved theory for the single-layer shell which includes the effects of transverse shear deformation and rotary inertia. Calculations are made for the specific case of the steel-concrete cylindrical shell subjected to a suddenly applied load. The solutions show that the method yields very good results. Therefore the proposed method is useful not only for a better investigating of the response characteristics of the shell but also available for a check on other numerical methods such a FEM.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.45 no.7
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• pp.539-549
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• 2017

In this paper, experimental studies on the shroud separation were performed to investigate characteristics of the shroud separation at mach 3. Shroud separation tests were carried out in the vertical free-jet wind tunnel that is capable of testing separable structures. A shroud model was miniaturized to meet test objectives and test section dimensions of the wind tunnel. Pneumatic Locking and separation mechanisms were designed considering external force due to free stream. High speed cameras were used to record the shroud motion and unsteady shock patterns over the deploying shrouds during the shroud separation process. Also, unsteady pressures on the nose surface were measured by using the pressure sensors. Through the tests, the measurement data necessary for researches on the shroud separation technology were obtained. Shroud separation behaviors and characteristics of unsteady pressure on the nose surface for each external flow conditions were analyzed.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.41 no.2
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• pp.150-155
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• 2013

We present a kevlar rope based Non-Explosive Actuator(NEA) device which has simple structure and is activated by burning Ni-Cr wire. Through performance test, we find it can be operated under various pre-load by simply changing turn number of Ni-Cr wire. It shows release time of 680ms and shock level of 110G under pre-load of 6.0kN. Launching environment and space environment tests are planned to verify performance of the NEA based on European Satellite Agency test manual. Conclusively, we expect the proposed NEA can be applicable to release solar panel and fairing separation.

• Journal of the Society of Naval Architects of Korea
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• v.35 no.4
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• pp.27-37
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• 1998

The sloshing is very important in a safe transport of the liquid cargo by a ship. With the increasing number of supertanker and LNG carriers, this problem has become increasingly more important. In order to study the magnitude and characteristics of impact pressures due to sloshing, experiments ware performed with a rectangular tank and compared with numerical results. Structural responses of tank wall under impulsive pressures were measured. Structural vibrations induced by the sloshing load were analysed by including hydroelastic erects in terms of added mass and damping. To check the validity of the numerical model, the natural frequencies of plate in air and water were compared with measurements, and a good agreement was found. In the case that a plate vibrates under impulsive loads, the pressure on the flexible plate is larger than that on the rigid plate without hydroelastic effects, which was confirmed experimentally. The frequency of oscillatory pressure as well as accel%pion coincides with the natural frequency of plate in water.

• Journal of the Korean Society for Aviation and Aeronautics
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• v.19 no.3
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• pp.10-15
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• 2011

The separation actuator for the small satellite should fix satellite appendages with high clamping force. After operation, it has to be separated from the satellite body without any damage on satellite system and release the appendages such as a solar panel and an antenna successfully. Therefore, we invent a non-explosive separation actuator for the small satellite which generates low shock and is resettable. In order to confirm performance of the proposed separation actuator, we carried out experiments for separation time, maximum preload for activation, and shock level.

• Journal of Aerospace System Engineering
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• v.16 no.6
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• pp.123-128
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• 2022

This paper proposes a non-explosive separation device for the deployable SAR antenna. This device utilises a Ni-Cr wire to restrain the antenna's belt mechanism, and joule-heating is used to minimise the impact of deployment. After the Ni-Cr wire has been cut, the device is deployed through the preload of the belt mechanism. Considering the design load(99g) and preload conditions, FEM analysis for AL7050 and Ti was performed. This analysis revealed that the amount of deformation for AL7050 was 0.256 mm with a margin of +0.09. In addition, by performing orbital thermal analysis, the temperature distribution for AL7050 in the worst cold case is confirmed as -50 to +2℃ and -10 to +90℃ in the worst hot case. This analysis confirmed that the separation device would remain stable even in the worst environment.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.36 no.11
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• pp.1473-1478
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• 2012

This paper presents the development of a fracture-type protector for carrying a reconnaissance robot to a remote target area. Instead of a conventional unlocking mechanism, a separation method based on the fracture of assembled parts was implemented in the proposed lightweight protector in order to improve the feasibility for a real battlefield. Simulations using the finite element model of the protector and the robot were performed to verify the fracture under the given loading conditions, and shock experiments using a drop table were performed to calculate shock transmittance through the protector to the robot. Several field tests for a 100-m flight proved that the proposed scenario (launching, flying, landing, and separation) was achieved successfully.