• Advances in aircraft and spacecraft science
• /
• v.9 no.5
• /
• pp.401-414
• /
• 2022

In the present paper, the optimal selection of batteries for an electric pump-fed hybrid rocket engine is analyzed. A two-stage Mars Ascent Vehicle, suitable for the Mars Sample Return Mission, is considered as test case. A single engine is employed in the second stage, whereas the first stage uses a cluster of two engines. The initial mass of the launcher is equal to 500 kg and the same hybrid rocket engine is considered for both stages. Ragone plot-based correlations are embedded in the optimization process in order to chose the optimal values of specific energy and specific power, which minimize the battery mass ad hoc for the optimized engine design and ascent trajectory. Results show that a payload close to 100 kg is achievable considering the current commercial battery technology.

• Journal of the Institute of Electronics Engineers of Korea SD
• /
• v.47 no.2
• /
• pp.94-99
• /
• 2010

This paper presents a charge pump architecture for correcting the current mismatch due to the PVT variation. In general, the current mismatch of the charge pump should be minimized to improve the phase noise and spur performance of the PLL. In order to correct the current mismatch of the charge pump, the current difference is detected by the replica charge pump and fed back into the main charge pump. This scheme is very simple and guarantees the high accuracy compared with the prior works. Also, it shows a good dynamic performance because the mismatch is corrected continuously. It is implemented in 0.13um CMOS process and the die area is $100{\mu}m\;{\times}\;160{\mu}m$. The voltage swing is from 0.2V to 1V at supply voltage of 1.2V. The charging and discharging currents are $100{\mu}A$, respectively and the current mismatch due to the PVT variation is less than 1%.

• Proceedings of the KIPE Conference
• /
• 2000.07a
• /
• pp.489-492
• /
• 2000

A novel low-cost simple and unity-power-factor electronic ballast is presented. The proposed electronic ballast employs a bypassing capacitor and load networks composed of ballast capacitors and small charge pump capacitors as power factor correction circuit combined with the secondary winding of the transformer in the self-excited current-fed push-pull resonant inverter(CF-PPRI) resulting in cost-effectiveness and higher efficiency. By analyzing the principles of power factor correction mathematically optimum design guidelines are presented. Since the lamps are used in power factor correction stage the input power is automatically adjusted according to the number of the lamps.

• KSBB Journal
• /
• v.5 no.3
• /
• pp.307-313
• /
• 1990

A microcomputer-aided fermentation system was constructed for high density fed-batch culture using dissolved oxygen(DO) as a substrate feeding indicator. DO signal was processed prior to aquisition to computer. Agitation speed and oxygen flow rate was changed stepwisely to maintain DO value at a constant level. Agitation speed was controlled by the output signal of D/A converter. Oxygen flow rate was controlled by a flow rate control valve connected to a stepping motor. Substrate was fed with a feeding pump operated by the abrupt increase of DO signal. Methylobacillus sp. SK1 was cultivated to test the system and 16.53g/l of cell density was obtained after 10 hr.

• Aerospace Engineering and Technology
• /
• v.2 no.2
• /
• pp.151-156
• /
• 2003

Liquid rocket engine system is classified into an engine of pressurization and turbo pump type by the way of fuel fed-supporting system. In the KSR-III sounding rocket, an engine of pressurization type was used, but there was lots of technical problems to be solved for a use as the first stage engine of space launch vehicle. So, an engine of turbo pump type was required to be developed to overcome the technical limitation of liquid rocket engine. In this research, the analysis of propellant of Kerosine-LOX and methane-LOX which are noticed as a future propellant was carried out for the purpose of studying the basic characteristics. And to review the basic characteristics of an engine of turbo pump type, among the sizing variant of the space launch vehicle, the ways of injecting a satellite to a direct orbit and transient orbit were discussed in this paper.

• Journal of the Korean Society of Propulsion Engineers
• /
• v.9 no.3
• /
• pp.74-84
• /
• 2005

This paper include the investigation of finding the system characteristics of facility by simulating open-type turbo-pump fed system, which has commercial control valves, using AMESIM (Advanced Modeling Environment Simulation) commercial software. After developing a flight-type control valve on the basis of the results, the system characteristics of facility for control and valve tests is estimated. Especially, one of purposes of this paper is to find PID value of each commercial control valve in the facility for system test. To find suitable control logic, PI and PID modes are also compared. This paper also introduces design parameters of valve and equipment for thrust control and TDS simulation, which are using control valves.

• Journal of Nutrition and Health
• /
• v.29 no.10
• /
• pp.1087-1095
• /
• 1996

The study was carried out to investigate a new type of functional foods with hypotensive effect which is critical in the prevention and treatment of hypertension and related circulatory diseases. The experimental diets(A, B, C) were prepared from plant based ingredients such as buckwheat, potato, perilla seed with different ratios formulated as an edible form appropriate for human consumption according to AIN-77 standard. Control group(D) was fed commercial rat chow. Twety-four 15-week-old SDR(Sprague Dawley rats) and twenty-four 20-week-old SHR(spontaneously hypertensive rats), weighing 200g respectively, were assigned to 4 treatments of 6 rats each in a completely randomized design. Blood pressure was measured at 7 day interval by tail-cuff sphygmomanometer using an IITC cuff pump and amplifier. The growth rates of both SHR and SDR were not statistically different in comparions with the control except those of diet B and C in SDR and SHR, respectively(p<0.05). When exprimental diets were fed, systolic blood pressure of SDR and SHR at day 28 had been lowered by 17-20 mmHg(ave. of 19.6mmHg for both strains) compared with the reference pressure at day 0. The levels of HDL-cholesterol were increased, while the levels of LDL-cholesterol consistently decreased in both strains when experimental diets were fed(p<.05). Plasma total cholesterol levels were not different among treatments. Plasma triglyceride levels were higher in control diet(commercial rat chow) due to two times higher fat content of control diet itself(p<.05). Atherogenic indices were lower compared to those of control when the experimental diets were fed in both strains (p,.05). The results suggest that the antihypertensive diets mainly consisting of plant-based ingredients may possibly effective in relieving hypertension as well as circulatory diseases.

• Aerospace Engineering and Technology
• /
• v.4 no.1
• /
• pp.196-202
• /
• 2005

In cryogenic feeding system of turbo pump fed liquid-propulsion rocket, rise of cryogenic propellant temperature can bring into geysering in pipe or cavitation in turbo pump. In this paper, performance analysis of recirculation line which is one of the method to inhibit these phenomenon is carried out based on the configuration of KSLV-I 1st stage LOX feeding system, and parametric study to find design parameter. Diameter and re-entrance height, initial LOX temperature, ullage pressure, and natural convection heat transfer coefficient are varied to see the effects on performance. Additional He is injected into recirculation line to promote LOX recirculation. 1-dimensional analysis using network-solver, SINDA/FLUINT is carried out.

• Proceedings of the Korean Society of Propulsion Engineers Conference
• /
• 2009.11a
• /
• pp.313-317
• /
• 2009

The orifice in the propellent feeding pipe line of a Liquid Rocket Engine(LRE) is used to balance the pressure of the pipe line. When a LRE starts up, pressure at the upstream of the orifice rapidly increases. In this case, pressure waves occuring by resistance of the orifice may induce low frequency instability in the pipe line. For this reason the study of dynamic characteristics of orifices is needed to prevent the instability. A pump is used to build up the pressure, and the pressure is measured upstream and downstream of the orifice when the orifice diameter is changed. With the increase of orifice diameter, water hammer decreases, but the effect of resistance downstream is increases.

• Journal of the Korean Society of Propulsion Engineers
• /
• v.8 no.4
• /
• pp.26-35
• /
• 2004

As part of thrust control technology research on turbopump-fed type liquid-propellant rocket engine system, the low frequency dynamic characteristics of turbopump was investigated. It can be described that a turbopump system has a 1st-order lag element. When the value, which was resulted by subtraction of the variation of turbine moment with respect to the variation of revolution number from the variation of pump moment with respect to the variation of revolution number, was positive, the time constant of the 1st-order lag element was positive which stood for a stable system. Increasing the above-mentioned valve within positive range leaded to the increase of response and to the decrease of controllability.