## 1 Introduction
SoftRide UniFlex consisted of a titanium flexure and a viscoelastic material to reduce the dynamic loads acting on the satellite along the launcher axial direction. To isolate both axial and lateral excitations from the launcher, SoftRide MultiFlex consisted of a pair of UniFlex isolators integrated with each other through a central post. The vibration in the launcher axial direction was isolated in the same manner as the UniFlex. Isolation in the lateral directions was achieved by vibrational-energy dissipation from the shear deformation of the constrained layers, as the dynamic bending of the flexure occurred. To enhance the performance of SoftRide MultiFlex, SoftRide OmniFlex was developed by [PERSON] et al. [7]. The major difference from the previous version was that the constrained layer was installed at the sides of the titanium flexure. This enabled the isolator to be more compact in volume, as well as enhancing the damping capability. [PERSON] et al. [8] proposed an isolation system using two serially connected flexure elements and a shear damping unit laminated with a metal plate and viscoelastic material. Isolation in the axial and lateral directions was achieved by the bending behavior of the titanium flexure and the shearing behavior of the damping unit, respectively. [PERSON] et al. [9] proposed a multi-frequency dynamic absorber using a two-spring mechanism arranged in each axial and lateral direction. These mechanisms are connected with the oscillating mass for tuning the specific target frequency for the spacecraft during the launch phase. [PERSON] et al. [10] proposed an active payload adaptor compliant with the Ariane 5 space-launch vehicle, which was able to reduce the interface loads to the payload in the 5-100 Hz low frequency domain by more than a factor of four. In actualizing a novel high damping three-axis passive launch vibration isolation for small satellite, we focused on the following two technical aspects. One is using the superelasticity of the shape memory alloy (SMA) material, and the other is applying multilayered thin plates with viscous lamina tapes to the SMA blades. The superelasticity is a unique characteristic of SMA material occurred by stress-induced phase transformation from the austenite to the martensite phase when the material is at above austenite finish temperature. It can be deformed considerably without being plastically deformed and recovers its original shape upon unloading. This makes it possible to ensure the structural safety of a satellite under the launch environment, even if the satellite is supported by a low-stiffness SMA application. In addition, this characteristic is associated with large hysteretic damping, owing to the phase transformation [11]. The effectiveness of using superelastic SMA for vibration isolation in space applications has been demonstrated in several previous studies [12; 13]. For example, [PERSON] et al. [12] proposed a superelastic SMA gear wheel that applied a two-axis gimbal-type X-band antenna to enhance the micro-jitter isolation capability without undergoing plastic deformation under excessive loading conditions. [PERSON] et al. [13] also proposed a blade-type cooler vibration isolator using a superelastic SMA material as a technical solution over ordinary titanium material. Then, the effectiveness of the superelastic SMA blade design was experimentally assessed and compared with that of an isolator made of titanium. If the superelastic SMA is applied to the WSVI, it is possible to ensure the structural safety of the satellite in a launch environment, while implementing a low-stiffness isolator. However, the SMA exhibits effective hysteretic damping only when the stress exceeds the critical point at which a phase transformation occurs. This means that an isolator with SMA material may exhibit insufficient damping performance, if the deformation is not sufficiently large.