Design a novel non-explosive release device using shape memory effect of SMA for spacecraft application

In this paper, a novel non-explosive release device for spacecraft with the aid of the shape memory effect of SMA(Shape Memory Alloys) is introduced. Since AFRL(Air Force Research Laboratory)'s first attempt in 1993, non-explosive release devices are widely used in space industry in deploying instrument like solar array, balloon or in separation of small satellites from launch vehicle. Most important function of them is to release the instrument safely with low-shock so that the instrument and spacecraft are not damaged during separation process. In addition to this, several features: short separation time, structural integrity with a high preload and reusability are often required. To develop such actuator, SMA(Shape Memory Alloys) having shape-memory effect(one-way memory effect and two-way memory effect) is widely used as the trigger or the load-bearing mechanism. However, in the case of SMA wire, usually, it works as the trigger with well-known one-way memory effect in commercial SMA actuator. Before re-using it, additional pre-straining process should be performed to make deformation up to a certain level using universal testing machine. Additionally, some of the used small parts including spools, plungers should be replaced. In the low shock release device with two-way memory effect, the trigger mechanism is extremely simple because SMA remembers two different shapes: one at the low temperature and the other at the high temperature shape. It does not need any pre-straining process as well as preserve major key requirement: low-shock, short separation time, and reusability. To verify the proposed device, EM(Engineering Model) is designed and constructed by combining with separation nut mechanism. Separation time and preload are also investigated by performance tests.