• Journal of the Korean Society for Aeronautical & Space Sciences
• /
• v.32 no.9
• /
• pp.153-161
• /
• 2004

• Transactions of the Korean Society of Mechanical Engineers B
• /
• v.34 no.2
• /
• pp.213-218
• /
• 2010

A cooling system utilizing liquid helium to chill the cryopanel (800 mm $\times$ 700 mm dimensions) down to 4.2 K was designed, implemented, and tested to verify the role of the cryopanel as a heat sink for the payload of a spacecraft inside the large thermal vacuum chamber (effective dimensions : 8 m ($\Phi$) $\times$ 10 m (L)) of KARI (Korea Aerospace Research Institute). Two LHe (Liquid Helium) Dewars, one for the main supply and the other for refilling, were used to supply liquid helium or cold helium gas into this cryopanel, and flow control for the target temperature of the cryopanel within requirements was done through fine adjustment of the pressure inside the LHe Dewars. The return helium gas from the cryopanel was reused as a thermal barrier to minimize the heat influx on the core liquid helium supply pipe. The test verified a cooling time of around three hours from the ambient temperature to 40 K (combined standard uncertainty of 194 mK), the capacity for maintaining the cryopanel at intermediate temperatures, and a 1 K uniformity over the entire cryopanel surface at around 40 K with 20 W cooling power.

• Journal of Hydrogen and New Energy
• /
• v.27 no.6
• /
• pp.642-650
• /
• 2016

One of the most feasible solution for reducing the excessive energy consumption and carbon dioxide emission is usage of more efficient fuel such as hydrogen. As is well known, there are three viable technologies for storing hydrogen fuel: compressed gas, metal hydride absorption, and cryogenic liquid. In these technologies, the storage for liquid hydrogen has better energy density by weight than other storage methods. However, the cryogenic liquid storage has a significant disadvantage of boiling losses. That is, high performance of thermal insulation systems must be studied for reducing the boiling losses. This paper presents an experimental study on the effective thermal conductivities of the composite layered insulation with aerogel blankets($Cryogel^{(R)}$ Z and $Pyrogel^{(R)}$ XT-E) and Multi-layer insulation(MLI). The aerogel blankets are known as high porous materials and the good insulators within a soft vacuum range($10^{-3}{\sim}1$ Torr). Also, MLI is known as the best insulator within a high vacuum range(<$10^{-6}{\sim}10^{-3}$ Torr). A vertical axial cryogenic experimental apparatus was designed to investigate the thermal performance of the composite layered insulators under cryogenic conditions as well as consist of a cold mass tank, a heat absorber, annular vacuum space, and an insulators space. The composite insulators were laminated in the insulator space that height was 50 mm. In this study, the effective thermal conductivities of the materials were evaluated by measuring boil-off rate of liquid nitrogen and liquid argon in the cold mass tank.

• Proceedings of the Korea Institute of Applied Superconductivity and Cryogenics Conference
• /
• 2000.02a
• /
• pp.48-51
• /
• 2000

The behavior of cryogenic liquid stored in a closed cryogenic tank has been studied at various liquid levels, as a function of pressure and temperature on time, assuming heat leak(NER) is 0.7%/day. The pressure depends, as expected, on the liquid-vapor ratio in a tank. The calculation shows that if liquid level is as high as 90%,much higher than the critical volume ration, in a closed tank of designed pressure 11 bar, it takes 5.4 to 15days for the entire volume of the tank to be filled with liquid and 11 to 22 days for the tank to be exploded. If a closed tank is full of liquid, it is extremely dangerous because of abrupt pressure increase so that the safety devices are necessary to vent out pressurized gas. These phenomena can be explained with the liquid heat capacity, latent heat and compressibility.

• International Journal of Aeronautical and Space Sciences
• /
• v.17 no.4
• /
• pp.535-550
• /
• 2016

Securing the safety and the reliability of liquid-propellant rocket engines (LREs) for space vehicles is indispensable as engines consist of many complex components and operate under extremely high energy-dense conditions. Thus, health monitoring has become a mandatory requirement, especially for the reusable LREs that are currently being developed. In this context, a dynamic simulation program based on MATLAB/Simulink was developed in the current research on the Space Shuttle Main Engine (SSME), a partly reusable engine. Then, a series of fault simulations using this program was conducted: at a steady state operating condition (104% Rated Propulsion Level), various simulated fault conditions were artificially injected into the simulation models for the five major valves, the pumps, and the turbines of the SSME. The consequent effects due to each fault were analyzed based on the time responses of the major parameters of the engine. It is believed that this research topic is an essential pre-step for the development of fault detection and diagnosis algorithms for reusable engines in the future.

• Proceedings of the Korea Institute of Applied Superconductivity and Cryogenics Conference
• /
• 2002.02a
• /
• pp.310-311
• /
• 2002

We designed a large bore superconducting solenoid as a source of magnetic field inside liquid-nitrogen-jacketed liquid helium dewar. The diameter of the sample space in the dewar is about 10.0 cm. Considering the space for thermal insulation between liquid helium and the sample tube, the solenoid bobbin has been designed to be 12.0 cm and the most inner layer of the solenoid 13.0 cm. The desired uniformity of the field, which is ~ $\pm$0.1％ of the central field amplitude deviation within ~5.0$^2$$\times$3.6 ㎤ with the shortest dimension along the solenoidal axis, restricted the length of the solenoid to be at least 41.14 cm.

• Journal of the Korean Society for Aeronautical & Space Sciences
• /
• v.37 no.7
• /
• pp.661-668
• /
• 2009

The slosh natural frequencies, damping ratio, slosh mass and slosh force applying point of the liquid in cylindrical tank are estimated using the nonlinear least squares method in time domain. The estimated slosh model parameters are in good agreement with the results of the theoretical calculations for various liquid depths. Furthermore, this methodology will be applied to predict the sloshing parameters for a liquid propellant tank using ground experimental test-bed.

• Bulletin of the Korean Space Science Society
• /
• 2004.10b
• /
• pp.325-327
• /
• 2004

The longitudinal instability (POGO) of the rocket should not be occurred during the whole flight time for the large class liquid propulsion system to complete a mission successfully. The longitudinal instability is caused by the resonance between the propulsion system and rocket structure in the low frequency range below 50Hz, ordinarily. Analysis on the low frequency dynamic characteristics on the liquid propulsion system with staged combustion cycle engine system was performed as a preliminary study on the longitudinal instability analysis.

• Journal of Aerospace System Engineering
• /
• v.9 no.1
• /
• pp.1-6
• /
• 2015

A critical speed analysis of oxidizer pump was peformed for a 7 ton class liquid rocket engine as the third stage engine of the Korea Space Launch Vehicle II. Based on the previously developed experimental 30 ton class turbopump and presently developing 75 ton class turbopump for the first and second stage rocket engine of Korea Space Launch Vehicle II, a layout and configuration of the 7 ton class turbopump rotor assembly are determined. A ball bearing stiffness analysis and rotordynamic analysis are performed for both of the bearing unloaded condition and loaded condition. Structural flexibility of the oxidizer pump casing is also included to predict critical speeds. From the numerical analysis, it is confirmed that the rotor system acquires sufficient separate margin of critical speed as a sub-critical rotor even though decrease of critical speed due to the casing structural flexibility.

• Earthquakes and Structures
• /
• v.9 no.3
• /
• pp.577-601
• /
• 2015

The thermomagnetic effect on plane wave propagation at the liquid-solid interface with nonclassical thermoelasticity is investigated. It is assumed that liquid-solid half-space is under initial stress. Numerical computations are performed for the developed amplitude ratios of P, SV and thermal waves under Cattaneo-Lord-Shulman theory, Green-Lindsay theory and classical thermoelasticity. The system of developed equations is solved by the application of the MATLAB software at different angles of incidence for Green and Lindsay model. The effect of initial stress and magnetic field in the lower half-space are discussed and comparison is made in LS, GL and CT models of thermoelasticity. In the absence of magnetic field, the obtained results are in agreement with the same results obtained by the relevant authors. This study would be useful for magneto-thermoelastic acoustic device field.