Experimental Demonstration of Cryogenic Cooler Disturbance Attenuation Using the Non-Linear Passive Isolation System

Abstract

This study demonstrates the isolation performance of a non-linear passive isolator to enhance the pointing performance through isolating disturbances induced by a spaceborne cryogenic cooler. In this paper, a non-linear passive isolation system with varying stiffness under launching and under on-orbit conditions to attenuate the micro-vibration of the cooler is proposed. The isolation system provides low stiffness for small excitation of the cooler during on-orbit operation and high stiffness when the excitation range is relatively larger under the launch environment. The performance of the passive isolation system is investigated through both a launch environment test and a micro-vibration measurement test of the cooler combined with non-linear passive isolators.

Performance evaluation of spaceborne cryocooler micro-vibration isolation system employing pseudoelastic SMA mesh washer

“…The proposed isolation system shows a non-linear behavior similar to that of the rubber-type passive isolation system proposed by Oh et al [14]. However, the low-stiffness range and the stiffness value of the proposed SMA mesh washer isolator are much wider and lower, respectively, than those of the conventional isolation system [14]. This means that one can expect to obtain a better isolation performance and insensible integration sensitivity of the isolator by using the proposed SMA mesh washer isolator.…”

“…The estimated eigen frequency of the cooler assembly in this displacement range is 23.2 Hz, which might be an eigen frequency of the cooler assembly in a launch environment. The proposed isolation system shows a non-linear behavior similar to that of the rubber-type passive isolation system proposed by Oh et al [14]. However, the low-stiffness range and the stiffness value of the proposed SMA mesh washer isolator are much wider and lower, respectively, than those of the conventional isolation system [14].…”

“…9 shows an internal view of the dummy cooler used in the test to simulate the micro-vibration disturbances of the flight model of the cooler [10] during its on-orbit operation. The target force level of the cooler in the y-axis is 1.5 N at the main operating frequency of 36 Hz, which is almost the same value as that for the cooler used by Oh et al [10,14]. The operation principle of the dummy cooler is based on the reciprocating motion of the moving magnet induced by electromotive force when a sinusoidal wave of 36 Hz generated by a function generator is applied to the coils wound around the moving magnet, which is fixed by flexible plate springs.…”

Microvibration in spacecraft

“…The disturbance sources are also supported softly to reduce the excitation force transmissibility (Oh, et al, 2013). This measure involves the problem of how to ensure such a flexible structure withstands the launch vibration environment.…”