• Journal of the Korean Society of Propulsion Engineers
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• v.23 no.6
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• pp.1-10
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• 2019

The wave motion inside the nozzle is known as one of the major damping elements of the rocket's combustion instability by it's aeroacoustic effects that result from the flow passage through the nozzle throat. These effects can be quantitatively evaluated by the nozzle admittance. In this study, one-dimensional linearized Euler equation was adopted to calculate the nozzle admittance, and trend analysis was performed depending on the nozzle's main design variables. As a result, when nozzle converging part shortens, it is verified that the frequency dependency of the nozzle admittance is decreased due to the widened frequency range with lowered longitudinal nozzle admittance. Also, admittance estimation using the short nozzle theory is not appropriate when the first tangential mode of the pressure perturbation arises.

• Journal of the Korean Society of Propulsion Engineers
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• v.9 no.4
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• pp.96-103
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• 2005

The main purpose of launch vehicle is to insert satellite into a target orbit safely and correctly. To accomplish the main purpose of launch vehicle, the inserting velocity, inserting angle, and final mass of launch vehicle should be within the allowable range. In general, such requirements are satisfied with applying TCS(Thrust Control System) and TDS(Tank Depletion System), which manage thrust and mixture ratio by controlling propellant flow rate with thrust and mixture ratio control valves. In this study, the control characteristics of thrust and mixture ratio control valve were examined by PID control logic for stable operation of liquid-Propellant rocket engine at on-dosing point. The analysis on the control characteristics of control valves was done with AMESim code and the results from control valve test facility at KARI.

• Journal of the Korean Society of Propulsion Engineers
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• v.9 no.3
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• pp.133-144
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• 2005

Enhancements to propellants provide an opportunity to either increase performance of an existing launch vehicle. One of the promising technologies is the use of densified cryogenic propellants such as liquid hydrogen and liquid oxygen. The main advantage of densified cryogenic propellants is the increase in propellant mass fraction. Increased propellant mass fraction means increased payload mass to orbit. This paper reviews the basic principles and current technology trends for cryogenic propellant densification technologies. Several promising densification methods are presented focused on liquid oxygen densification. Engine and vehicle performance analyses are also presented to quantify the potential performance benefits of densified propellants in an overall system. And suggestions of application scheme for satellite launch vehicle is made.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2010.11a
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• pp.590-593
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• 2010

The processes of supplying propellants into propellant tanks play important roles during launch preparation of satellite launch vehicle. The total weight of launch vehicle greatly depends on the accuracy of filling quantity of propellant during launch preparation. Among propellants used for launch vehicles a cryogenic propellant such as liquid oxygen is widely adapted as an oxidizer for launch vehicles. Such cryogenic propellant usually resides in a propellant tank as two-phase fluid with liquid and gas, which needs an accurate level measurement system to detect the position of propellant surface precisely. In this paper the fabricating process of a level measurement system using capacitance type with three electrodes is analyzed. In addition, the change of electric signal according to the height of liquid is verified by testing the level measurement system under consideration. The results of tests shows as expected the linear trend of voltage according to the change of water height in a tank.

• Journal of the Korean Society of Propulsion Engineers
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• v.21 no.6
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• pp.1-7
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• 2017

The performance of a MEMS solid propellant thruster was predicted and analyzed through internal ballistics model and CFD analysis. The nozzle throat was $416{\mu}m$, and the area ratio of the nozzle was 1.85. As a result of the internal ballistics model, chamber pressure increased up to 197 bar and the maximum thrust was 3,836 mN. In CFD analysis, the chamber pressure of the internal ballistics model was applied as the operating pressure, and the CFD model was divided into an adiabatic and a heat loss model. As a result, the maximum thrust of the adiabatic model was 14.92% lower than that of the internal ballistics model, and the effect of heat loss was insignificant.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2004.03a
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• pp.605-610
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• 2004

Solid propellants allow thrusters to be light-weight, com-pact and robust because they require neither tank nor valve, Moreover, the solid propellant will not leak, spill or slosh. Consequently, the solid propellant thruster is one of the potential candidates for the microthruster. On the other hand, the control of the solid propellant combustion is difficult, since the conventional solid propellant continues to bum until all the stored propellant is consumed. Although particular devices like thrust reverser were designed to control the combustion, these devices were rarely used in the practical rocket motors. These devices rise thruster weight as well as complicate the thruster operation. In this study, a solid propellant microthruster using laser sustained combustion was designed in order to develop a high-efficiency microthruster overcoming the previously-mentioned difficulty. This designed thruster has semiconductor lasers and non-self-combustible solid propellants in addition to the conventional solid propellant thruster. In this designed thruster, the semiconductor laser controls the combustion of the non-self-combustible solid propellant. In order to demonstrate that the solid propellant combustion is controllable with laser, some non-self-combustible solid propellants were irradiated with the laser at a back-pressure of about 1㎪. A 40-W class Neodymium Yttrium Aluminum Garnet (ND:YAG) laser was used as a tentative alternate to the semiconductor laser. This experiment has shown that the solid propellant combustion was controllable with 10- W class laser irradiation.

• Journal of the Korean Society of Propulsion Engineers
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• v.17 no.6
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• pp.59-66
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• 2013

Spray characteristics of single round jet with liquid nitrogen and coaxial spray with liquid nitrogen and gaseous argon were observed. Shadowgraph method was used for spray visualization, and density gradient magnitude image was used to analyse the result. In subcritical condition, irregularity of the jet surface was harder in the coaxial spray. In supercritical condition, diffusion of nitrogen injected from shear coaxial injector was faster than single jet. Jet diameter was induced by averaging images, in supercritical condition, difference of diameter of coaxial jet was rapidly decreased than that of single jet.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2017.05a
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• pp.26-29
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• 2017

KARI has been conducting R&D for independent development of KSLV-II since 2010. Vehicle holding device is a device for vertically standing SLV on the launch pad of launch complex and fixing the lower part of vehicle in order to firmly fix vehicle so that SLV does not fall from an external load such as a wind load. When thrust generated after the 1st stage engine ignition of SLV must exceed the takeoff weight of vehicle, and holding device should be quickly released so that it does not interfere with takeoff of vehicle like other ground equipment at the beginning of the launch. Pyro-valve is one of the key components constituting VHD, and it should have high reliability and quick response characteristics with similar functional parts applied to launch vehicle separation device and satellite separation device. Through this paper, I intend to broaden the overall understanding of the development process of pyro-valve for VHD and KSLV-II.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2017.05a
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• pp.79-87
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• 2017

Korea Aerospace Research Institute has being developed a staged combustion cycle rocket (SCCR) engine with high specific impulse to send a 3-ton class satellite into geostationary orbit while conducted Korean Space Launch Vehicle (KSLV) II project. The SCCR engine is different from the KSLV-II engine, which is open cycle engine using a gas-generator. The SCCR engine with closed cycle is composed of a pre-burner, a turbo pump, and a main combustor. The technology demonstration model (TDM0) was assembled and tested in the 7ton-class engine combustion test facility of Naro Space Center, and the combustion test was successfully conducted. Afterward engine-shaped SCCR engine model (TDM1) is being designed and developed for the next combustion test.

• Journal of the Korean Society of Propulsion Engineers
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• v.23 no.3
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• pp.119-126
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• 2019

For rockets using cryogenic liquid hydrogen or liquid oxygen, chilling is required to avoid cavitation and surge problems. Chilling is categorized by the initial chilling/filling stage and the low-temperature maintenance stage. In addition, to improve satellite insertion capability, a multi-ignition capability is required and accordingly chilling to prepare for the next ignition during low-gravity coasting is also required. This paper describes the overall aspects of filling and low temperature maintain marinating for the booster and the upper stage engine including chilling for multi-ignition.