• Journal of the Korean Society of Propulsion Engineers
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• v.11 no.3
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• pp.13-19
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• 2007

This paper described design method to minimize the crosstalk effect of multiaxis thrust measurement stand which can measure the thrust vector control performance of Solid Rocket Motor. This paper presents a theoretical solution for predicting the magnitude of crosstalk and calculates design sensitivity. The results indicate that the most important parameter of crosstalk is the displacement of flexure-loadcell-flexure assembly. And shape, dimension and mechanical properties of flexure and loadcell can also influence the magnitude of crosstalk.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2008.03a
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• pp.427-430
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• 2008

Electroforming is one of the key technologies for the regenerative thrust chamber of the rocket engine. To use nickel electroforming method for the thrust chamber, direct electroforming of nickel on cupper and the welding method between different materials are needed. Minimizing the internal stress is one of the important factor for making thick electroforming,. Also minimizing contamination(ex. Sulfur containing compound) is another important factor for the stability of quality. This paper includes advanced methods for thick nickel electroforming, those of strength test results and EDS/EPMA inspection results. Advanced for electroforming process makes the achievement of Electro-beam welding between Inconel718(Manifold) and Nickel Electroforming. This paper also includes the influence of the electroforming precipitation angle on strength. Thus advanced electroforming improvement processes and the test results make achievement for manufacturing of the regenerative thrust chamber with direct nickel thick electroforming on cupper materials.

• Journal of ILASS-Korea
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• v.23 no.4
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• pp.159-168
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• 2018

Thrust throttling in a liquid rocket engine can be implemented via several ways such as high pressure drop injector, dual manifold, multiple chamber, pintle injector, and gas injection. Thrust throttling using gas injection controls thrust by usually injecting inert gas into propellant through an aerator to reduce the propellant's bulk density. In this study, the outside-in aerator was used in the propellant line to create two phase flow. Closed-type, open-type, and screw-type bi-swirl coaxial injectors were utilized for investigating throttling characteristics such as pressure drop, mixture density, and discharge coefficient according to gas-liquid mass ratio.

• International Journal of Naval Architecture and Ocean Engineering
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• v.12 no.1
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• pp.325-342
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• 2020

The current study is focused on the evaluation of the ultimate strength of stiffened panels found in ship hull structures that are subjected to combined uniaxial thrust, in-plane and out-of-plane bending moments. This loading condition, which is in general ignored when performing buckling checks, applies to representative control geometries (stiffener with attached plating) as a consequence of the linearly varying normal stresses along the ship's depth induced by the hull-girder vertical bending moment. The problem is generalized by introducing a non-uniform thrust described by a displacement ratio and rotation angle and by introducing the slenderness ratios, within the practical range of interest. The formed design space is explored through methods sourcing from Design of Experiments and by applying non-linear finite element procedures. Surrogate empirical models have been constructed through regression analysis and Response Surface Methods. An additional empirical model is provided to the literature for predicting the ultimate strength under uniaxial thrust. The numerical experimentation has shown that is a significant influence on the ultimate strength of stiffened panels as the thrust non-uniformity increases.

• International Journal of Naval Architecture and Ocean Engineering
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• v.13 no.1
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• pp.126-135
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• 2021

Wave energy is one of the most available sources of renewable energy in the world. It has been previously proven that the flapping foil can generate thrust forces using energy from the surface waves and an empirical formula was proposed to predict the thrust forces generated by a flapping foil consist of NACA0015 section (Kumar and Shin, 2019a). However, the proposed empirical formula was restricted to the head waves i.e. 0° azimuth angle which was not useful for the flapping foils encountering with oblique and following waves. Therefore, in this study, the thrust empirical formula was modified to include the effects of azimuth angles based on the experimentally obtained data. And the modified empirical equations were validated by the combination of foils experimentally.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.37 no.4
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• pp.392-398
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• 2009

Theoretical thrust equations for the diverse nozzle expansion condition were derived. By using the obtained thrust equations, parametric studies were carried out to estimate the effect of pressure exponent, minimum operation pressure, ambient pressure and extinguishment pressure on thrust modulation performance in pintle-nozzle solid rocket motors. Analysis results showed that thrust turndown ratio can be easily attained by small nozzle-throat area variation at high pressure exponent, low minimum operation pressure, high ambient pressure and high extinguishment pressure condition. At those conditions, the highest chamber pressure to obtain the intended thrust turndown ratio can be minimized.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.37 no.5
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• pp.476-482
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• 2009

The effect of pintle shape on the thrust level of pintle-nozzle Solid Rocket Motor(PNSRM) was studied numerically using the Spalart-Allmaras turbulent model of Fluent. Mass flow rate of PNSRM was always less than theoretical value and the extent of decrease in mass flow rate grew in the large pintle because of increase in the relative boundary layer thickness between pintle body and nozzle wall. The bigger pintle size was, the more thrust of pintle tip pressure was obtained. Meanwhile the more thrust of nozzle and chamber pressure decreased. Hence, total thrust of big pintle was less than a small pintle under same throat area condition. Specific impulse was relatively flat for all pintle shape.

• Aerospace Engineering and Technology
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• v.9 no.2
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• pp.8-13
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• 2010

An effective control of the axial thrust of a turbopump is one of the critical issues for obtaining its operational stability. Axial thrusts of the fuel pump for the 75-ton class rocket engine under development were measured with water as a test propellant at a room temperature. According to the test results, the axial thrust of the fuel pump seemed to satisfy the axial force condition of its bearing. Also, the thrust was increased as a whole when the flowrate of the pump was decreased. Furthermore it was found that the thrust and the leakage flowate were modified when the gaps between the floating ring seals and the impeller were changed.

• International Journal of Aeronautical and Space Sciences
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• v.13 no.3
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• pp.317-322
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• 2012

The low speed aerodynamic characteristics for a modified sonic arc airfoil which is designed by using the nose shape function of sonic arc, the shape function of NACA four-digit wing sections, and Maple are experimentally investigated. The small rotor blades of a modified sonic arc and NACA0012 airfoil are precisely fabricated with a commercially available light aluminum(Al 6061-T6) and are spin tested over a low speed range (3000rpm-5000rpm). In a consuming power comparison, the consuming powers of NACA0012 are higher than that of modified sonic arcs at each pitch angle. The measured rotor thrust for each pitch angle is used to estimate the rotor thrust coefficient according to momentum theory in the hover state. The value of thrust coefficients for both two airfoils at each pitch angle show almost constant values over the low Mach number range. However, the rotor thrust coefficient of NACA0012 is higher than that of the modified sonic arc at each pitch angle. In conclusion, the aerodynamic performance of NACA0012 is better than that of modified sonic arcs in the low speed regime. This test model will provide a convenient platform for improving the aerodynamic performance of small scale airfoils and for performing design optimization studies.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.15 no.1 s.94
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• pp.87-95
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• 2005

This paper proposes a method to calculate the characteristics of a coupled hydrodynamic journal and thrust bearing of a HDD spindle motor. The governing equations for the journal and thrust bearings are the two dimensional Reynolds equations in $\theta z$ and $ r\theta$ planes, respectively. Finite element method is appropriately applied to analyze the coupled journal and thrust bearing by satisfying the continuity of mass and pressure at the interface between the journal and thrust bearings. The pressure in a coupled bearing is calculated by applying the Reynolds boundary condition and compared with that by using the Half-Sommerfeld boundary condition. The static characteristics are obtained by integrating the pressure along the fluid film. The flying height of spindle motor is measured to verify the proposed analytical result. This research shows that the proposed method can describe HDB in a HDD system more accurately and realistically than the separate analysis of a journal or thrust bearing.