Rational selection of parameters of dynamic damper of longitudinal vibrations of liquid launch vehicle
Journal Title: Технічна механіка, Техническая механика, Technical Mechanics - Year 2014, Vol 3, Issue 3
Abstract
A significant increase in amplitudes of elastic longitudinal vibrations of a launch vehicle (LV) occurring in losses in longitudinal stability of liquid LVs may be responsible for an emergency. Measures for providing longi-tudinal stability are generally directed to the elimination of danger converging the proper frequencies of vibrations of the LV body and liquid propulsion system (LPS). Mounting a dynamical vibration damper (DVD) on LV, which is tunable to a danger frequency and damp-ens one, is an alternative way. The DVD does not dampen vibrations and only decreases their amplitudes (“sof-tens” the instability). However, mounting the DVD on the completed rocket is more simply than mounting damp-ers on its LPS. The problem resides in the fact that in determining the mass and location for mounting DVD on LV the ex-isting recommendations for selecting the DVD optimal parameters are not necessarily successful and the frequen-cy of longitudinal vibrations of the LV body, to which the DVD must be tuned, is changed in the LV flight. The determination of the DVD turning frequency becomes all the more complicated if longitudinal parame-ters with different frequencies occur in several sections of the LV flight. On the other hand, analysis of the DVD effects on longitudinal stability of LV is the challenge using a traditional mathematical model of a dynamic inter-action between the LPS and LV body. The paper presents an approach to determination of DVD parameters, based on a numerical study of the stability of a linear dynamical system of LSP and LV body with the DVD, using an improved mathematical model of a dynamic interaction between the LPS and the LV body with the DVD. The approach proposed is employed to determine parameters of the dynamic damper of longitudinal vi-brations of the three-stage liquid rocket, which loses its longitudinal stability in two sections of the flight. The selected values of DVD parameters provided a significant decrease in regions of divergent vibrations of the system of LSP and the LV body and coefficients of their divergence resulting in limitation of the possibility of evolution of these vibrations and in “softening” the system instability.
Authors and Affiliations
N. Khoryak
Keywords
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