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As the market for CubeSats expands, designers are faced with more issues of how to get the operational capability offered by large satellites into smaller packages. Space on a space vehicle has always been a constraint as weight and size means added costs on scarce rockets with limited payload capacity. One of the areas of difficulty has been in designing and making small decoupling actuators as large satellite mechanisms do not scale down due to the number of components. Also, the impulse force caused by large satellite actuators – even if they were appropriately scaled – would throw a CubeSat off course.
Navy scientists have ingeniously developed a new coupling device made by press-fitting a hollow nickel-titanium shape memory alloy (SMA) shaft into a steel hub. Press-fitting the hollow SMA shaft in its detwinned martensitic phase into a steel hub creates a joint capable of holding parts such as emergency doors, satellite solar panels, or tamper locks securely together until commanded release. The release is accomplished by heating the SMA to its activation temperature. The resulting decrease in diameter of the hollow SMA shaft allows it to easily slip out of the hub, releasing the part. Load testing showed ultimate strengths about twice that of traditional press-fit coupling strength calculations. The coupling can be designed to be a simple mechanism of very small size, on the order of one cubic centimeter, capable of achieving coupling strengths in excess of 4000 N (900 lbs).
This US patent 8,579,535 is a divisional of US patent 9,003,627. The ‘627 patent embodies the method for releasably coupling the components. The ‘535 patent embodies the mechanism.
- The design allows for large coupling strength and requires little power to actuate release
- Designed with very few parts and a simple, single-motion actuation minimizes failure modes and increases coupling mechanism reliability
- US patent 8,579,535 available for license