Design and Implementation of a Shape Memory Alloy Actuated Separation Mechanism for Microsatellites

Paper number

IAC-05-C2.4.09

Author

Mr. Masafumi Iai, Tokyo Institute of Technology, Japan

Coauthor

Mr. Ken Fujiwara, Tokyo Institute of Technology, Japan

Coauthor

Mr. Katsutoshi Imai, Tokyo Institute of Technology, Japan

Coauthor

Mr. Shinji Masumoto, Tokyo Institute of Technology, Japan

Coauthor

Prof. Saburo Matunaga, Tokyo Institute of Technology, Japan

Coauthor

Mr. Kei Miyamoto, Tokyo Institute of Technology, Japan

Year

2005

Abstract

This paper describes the design and the implementation of a shape memory alloy (SMA) actuated separation mechanism for microsatellites. The purpose of the work is to develop a separation mechanism which enables microsatellites to hold a detachable object and separate it. This mechanism will be a part of the tether experiment system installed in Tokyo Tech's second satellite, Cute-1.7, and will separate an end mass of its tether. Additionally, other possible applications include holding and releasing of a deployable boom. 

With focus on installation in microsatellites, mechanical simplicity, small size, and light weight are primary requirements. First the use of SMA meets those requirements because SMA can function both as a structure and as an actuator, resulting in less number of parts. Also the technique of shrink-fit contributed its simplicity. Finally, in order to avoid duplicated effort, it is decided that the mechanism does not support force caused by acceleration during launch. The proposed mechanism is aimed at holding a detachable object while other larger separation mechanism holds a satellite during launch. Thus, the proposed mechanism is aligned so that the latter satellite separation mechanism can support the force applied on the detachable object.

The mechanism consists of a SMA ring with and a stainless ring. The former is attached to a satellite body, and the latter to an end mass. The two rings are fixed to each other by employing the technique of shrink-fit, which is widely used to fix machinery tools. The stainless ring is inserted in the SMA ring. When a detachable object is to be separated, the heater is activated to expand the diameter of the SMA ring, and then the object becomes free. The design resulted in holding pressure of greater than 20MPa at the interface of two rings in the ambient temperature range as wide as about -80 to 80 degree Celsius. The entire mechanism is 75mm in diameter and 5mm in height. The inner diameter of the SMA ring and the outer diameter of the stainless ring are 75mm and their thickness is 5mm. 

In conclusion, a new SMA separation mechanism is proposed. The use of SMA and shrink-fit technique made the mechanism suitable for installation in microsatellites. Every design considerations, fabrication process, operation sequence is detailed in the paper. In addition, separation experiment in microgravity is to be conducted at Micro-Gravity Laboratory of Japan, and its results will be reported.

Abstract document

IAC-05-C2.4.09.pdf

Manuscript document

IAC-05-C2.4.09.pdf (🔒 authorized access only).

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