Blossoming of Coiled Deployable Booms

Coiled deployable booms have been used extensively in space and are a large part of the deployable space structures family. They have a wide variety of uses such as the deployment of instruments, gravity-gradient stabilisation masses and more recently solar sails. Most deployable booms are similar to a carpenter's tape measure in the way they are coiled in a retracted condition and then deploy to form the boom structure. There have been many developments in the optimisation of boom properties in the deployed state, by using different shape cross sections and by using different materials. The first metal tape spring booms have developed into the more modern booms with a variety of cross sections. One aspect that is common to all booms is the coiling and uncoiling process and the difficulties associated with this. Blossoming, where the boom starts to uncoil within the boom deployer, can lead to the jamming of the mechanism. The reasons behind blossoming have not been thoroughly investigated, leaving designers of booms, and boom housing mechanisms to try and mitigate this problem themselves, often by trial and error. This work investigates boom blossoming with the aim of better understanding the underlying mechanics so that more effective deployment systems can be designed in the future. A method is developed that uses the strain energy stored in coiled booms to find the maximum tip force that can be achieved before blossoming occurs. This method is also used to investigate the central spindle torque during blossoming. The effects that the coil geometry and the friction between the layers of the coiled booms have on blossoming are also investigated. The theory developed should enable the designers of tape spring deployers to estimate the tip force and central spindle torque of a tape spring boom in the design phase of projects and reduce the reliance on trial and improvement type testing once deployers have already been built.