• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.31 no.3
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• pp.58-64
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• 2003

Pogo is the instability resulting from the interaction between rocket structure and propulsion system of liquid propellant rocket. The coupling of structure and propulsion system can lead to severe problem in rocket. For the analysis of pogo, a time-invariant linearized mathematical model is developed for a selected flight time. Propulsion system is modeled using element representations for each components. Rocket structure is modeled using FEM. Form the results of modal analysis of structure, the behavior of structure can be represented. System equations for coupling structure and propulsion system are composed. The stability in obtained by the eigen solution of system matrix. The optimization of the design variables such as size, place of accumulator for suppressing pogo instability in carried out. This article of study can be used to determine the degree of stability, and guide the design of pogo suppression system.

• Journal of the Korean Society of Propulsion Engineers
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• v.7 no.4
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• pp.1-9
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• 2003

To reduce the possibility of longitudinal dynamic instability, called "POGO", in the liquid rocket system due to the feedback effect of a main structure and a fuel-feeding system, several different types of PSD(POGO Suppression Device) systems have been studied. In the present study, several different types of PSD were reviewed. Basically, all PSD systems can be categorized into two groups; a passive PSD or an active PSD. We can classify the passive PSD's into more detailed groups according to their compliance methods; localized compliance methods or distributed compliance methods. As a result of our intensive review on various PSD's, the gas-filled accumulator with a level control system is considered to be the most suitable one to suppress the POGO instability without mal-effects to the performance of a fuel-feeding system.ng system.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2002.04a
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• pp.10-13
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• 2002

Pogo is the instability resulting from the interaction between rocket structure and propulsion system of liquid propellant rocket. The coupling of structure and propulsion system can lead to severe problem in rocket. For the analysis of pogo, a time-invariant linearized mathematical model is developed for a selected flight time. Propulsion system is modeled using element representations for each components. The constitutive equation of propulsion system is a homogeneous second-order equation form in the Laplace domain. Rocket structure is modeled using FEM. From the results of modal analysis of structure, the behavior of structure can be represented. System equations for coupling structure and propulsion system are composed of all propulsion system equations and vehicle motion equations reacting on the vehicle by each component of propulsion system. The stability is obtained by the eigen solution of system matrix. The optimization of the design variables such as size, place of accumulator for suppressing pogo instability is carried out. This article of study can be used to determine the degree of stability, and guide the design of pogo suppression system.

• Proceedings of the KSME Conference
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• 2002.08a
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• pp.495-498
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• 2002

This article deals with the introduction of longitudinal instability of liquid rocket (pogo) and the analytical results on the frequency responses of KSR-III propulsion feeding system. Both the stiffness of bellows and the cavitation volume of venturi affect the frequency response of the feeding system. Especially, bellows has a great roll to reduce the natural frequency of the feeding system. Also, oxidizer and fuel feeding systems of the KSR-III have natural frequencies of ${\~}280Hz\;and\;{\~}90Hz$, respectively.

• Aerospace Engineering and Technology
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• v.7 no.1
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• pp.177-182
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• 2008

In this article, a mathematical modeling which is composed of linearized transfer functions on POGO suppression device was executed. The main parameters of PSD model can not be easily determined from the analysis due to the nonlinearity of the parameters. This article deals a method to get the values of the main parameters from the experimental results.

• Journal of the Korean Society of Propulsion Engineers
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• v.5 no.4
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• pp.75-82
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• 2001

KSR-III propulsion feeding system is designed to feed a certain amount of propellant to engine by the end of combustion. The oscillation of propellant to engine would cause combustion instability and thrust oscillation and POGO phenomenon. This article deal with analysis performed such as the effect of rocket acceleration on the propulsion system and POGO analysis to ensure the performance of KSR-III

• Journal of the Korean Society of Propulsion Engineers
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• v.6 no.3
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• pp.45-52
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• 2002

This article deals with the introduction of longitudinal instability of liquid rocket (pogo) and the analytical results on the frequency responses of Korean Sounding Rocket (KSR-III) propulsion feeding system. Both the stiffness of bellows and the cavitation volume of venturi affect the frequency response of the feeding system. Especially, bellows has a great roll to reduce the natural frequency of the feeding system. Also, oxidizer and fuel feeding systems of the KSR-III have natural frequencies of about 280Hz and 90Hz, respectively.

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

• International Journal of Aeronautical and Space Sciences
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• v.18 no.3
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• pp.485-497
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• 2017

The pogo phenomenon refers to a type of multidiscipline-related instability found in space launch vehicles. It is caused by coupling between the fuselage structure and other structural propulsion components. To predict the pogo phenomenon, it is essential to undertake adequate structural modeling and to understand the characteristics of the feedlines and the propulsion system. To do this, a modal analysis is conducted using axisymmetric two-dimensional shell elements. The analysis is validated using examples of existing launch vehicles. Other applications and further plans for pogo analyses are suggested. In addition, research on the pogo phenomenon of Saturn V and the space shuttle is conducted in order to constitute a pogo stability analysis using the results of the present modal analysis.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2017.05a
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• pp.714-717
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• 2017

Among the factors considered in the design stage of a space launch vehicle using liquid propellant, research has been focused out on the pogo phenomenon, longitudinal dynamic instability. The pogo phenomenon refers to the instability that the longitudinal vibration of the launch vehicle structure causes a change in the pressure and flow rate of the fluids in propulsion system, and this change re-excites the fuselage structure. This mechanism constitutes a closed system to gradually increase the vibration of the launch vehicle. This paper specifically focuses on the dynamic analysis of pressure and flow changes in the propulsion system. Based on the example study of the space shuttle, the acoustic modal analysis of the propulsion system is performed to predict the modes of the supply line causing instability of the fuselage.