Assembly, deployment, and maintenance of mechanical systems will become an even more significant challenge for space program managers and designers as future space projects increase in size and complexity with higher costs and larger mechanical loads. Robotic assistance reduces human E.V.A. time but also reduces mechanical design flexibility. As a result, designers need to develop structural systems that can be assembled and maintained easily in space and carry the required loads.
For hundreds of years, fasteners have been the most powerful, most flexible method of fastening and connection; they are inhibited in their robotic use generally due to their inherent weaknesses of slowness, high torque requirements, and cross-threading. These problems compounded for astronaut use in the zero gravity and harsh working conditions of space. Instant or fast-acting fasteners and "quick-connect" coupling designs are available in many forms, such as collets, rivets, self-tapping screws, and "snap-on" couplings. However, they often cannot be used repetitively, are usually not suitable for vibration and pressure, and are often subject to accidental disconnection. A system using flexible thread segments permitting the male thread to "zip" into the female, instantly form a rigid threaded joint (commercially known as "Zip Nut®" technology) enables aerospace designers to have speed and ease in fastening and to retain the load and flexibility benefits of screw threads.
N.A.S.A. first utilized this technology in 1989. Fullerton Fastening System developed for shuttle flight STS29. The technology has spread slowly throughout the space program, essentially by word of mouth, for numerous difficult robotic and E.V.A. assembly projects to date:
Robotic Assembly - Main Truss Structural Joints
Robotic Assembly - Alpha & Beta Solar Panel Gimbals
E.V.A. Handling - Deployment of UHF Antenna Booms
E.V.A. Handling - Solar Array Mast Canister
E.V.A. Handling - Universal Trunnion Attachment System
E.V.A. Handling - Kit for External Repair of Module Impacts (K.E.R.M.I.T.)
E.V.A. Handling - Wide Field and Planetary Camera
E.V.A. Handling - Fine Guidance Sensor
E.V.A. Handling - Solar Array Drive
E.V.A. Handling - Data Interface Unit
E.V.A. Handling - Fine Guidance Sensor
E.V.A. Handling - S-Band Single Access Transmitter
The success of these applications has led N.A.S.A. to incorporate FFS Technology as a "Recommended Technique for Effective Maintainability in Selection of Robotically Compatible Fasteners and Handling Mechanisms" (Technique DFE-l) in its official Policy for Safety and Mission Success (NPD 8700. 1). Those official Design Factors for all future N.A.S.A. projects specifically recommend FFS technology to "avoid jamming and binding" and as an "excellent soft dock attachment."
NASA formally recognized the history and widespread application of Robert Fullerton’s flexible thread concept (Zip Nut) in space in its 1989 Spinoff publication.
The concept is even listed in NASA’s official Policy for Safety and Mission Success (NPD8700.1) as a “Recommended Technique for Effective Maintainability “ in “Selection of Robotically Compatible Fasteners and Handling Mechanisms” (NTM4628) See excerpts in the EVA Tools and Equipment Reference Book.
Zip Lok® is the "push on" solution the airframe industry has been waiting for. It performs well under vibration, helps workers with installation in tight locations where threads may not be visible, and eliminates the need for other locking devices, such as washers and safety wire. Previous iterations of the design have been proven to save lives and prevent catastrophic failures in flight. Learn more about Zip Lok® aircraft panel fasteners here.
The global market for hydrogen fuel cells is expected to grow from $7.5 billion in 2022 to $19.5 billion in 2027 at a growth rate of 21%. As hydrogen becomes more widely used as a vehicle fuel, there will be a need for a fuel transfer coupler that can be used by the public, similar to a gas pump. The Zip Lok® Hydrogen Coupler, which was originally conceived for use on the proposed Moon Base, meets the high application and safety requirements needed for everyday use. The coupler is a simple and efficient device that will enable the safe transfer of hydrogen fuel to vehicles, without the fear of escaping gases. Learn more about Zip Lok®'s fuel coupler applications here.
Astronaut Steven L. Smith, Hubble Space Telescope (HST) servicing mission 3A payload commander, retrieves a Pistol Grip Tool (PGT) power tool while standing on the mobile foot restraint at the end of the Remote Manipulator System (RMS). Here Smith is using a flexible thread system to quickly make repairs in one of the most complex environment - An application where Zip Lok® thrives. Read more about Zip Lok®'s potential space applications here.