Packaging and Deployment of Large-Area Structures
Many current and future space missions need structures with large planar surface areas such as antenna arrays, photovoltaic arrays, drag sails, sunshields, and solar sails. To minimize mass, these structures tend to be thin. Often, these structures require tight packaging for launch into orbit and are deployed into their operational state after launch.
This need for packaging and deployment poses several fundamental challenges: making efficient use of the stowage volume, i.e. leaving minimal voids; biaxial compaction, i.e. reducing the two large in-plane dimensions; packaging membranes of arbitrary non-zero thickness; avoiding permanent deformation of the structural material; the ability to deploy with small and predictable edge forces, to lower the requirements on the edge structure that will carry out the deployment.
We have introduced a novel packaging concept that addresses each one of these challenges. This packaging concept, called slip wrapping, exploits a mechanism known as a slipping fold, which allows for both rotation about and translation along a fold line. The packaging concept has two compaction steps, each compacting the membrane along a single dimension. First, the membrane is z-folded using n - 1 parallel slipping folds. Then, the resulting stack of n strips is wrapped in a rotationally symmetric fashion. The slipping folds accommodate the incompatibility created by wrapping the thick membrane strips around different radii. The symmetric wrapping scheme ensures that the ends of the strips need not slip, and can therefore remain connected.
The video below demonstrates a controlled, two-stage deployment of a membrane packaged according this scheme.
This packaging scheme can be generalized to many other fold-and-wrap patterns, such as the 4-fold-symmetric packaged model shown at the top of this page. It can also be used to package structures that are not just membranes, but have some out-of-plane bending stiffness. We are using such structures, where the edges of the strips are reinforced with collapsible booms, in the development of large space solar power spacecraft.
One example of such collapsible boom is the Triangular Rollable And Collapsible (TRAC) mast. This type of structure consists of two tape measure-like sections that are bonded together on one edge. The resulting bending stiffness to mass ratio, once deployed, can be really high while allowing a tight packaging method. We are currently working on the manufacturing and simulation of ultra-thin TRAC boom.
- Arya, M., Lee, N. and Pellegrino, S. (2016). Ultralight Structures for Space Solar Power Satellites. SciTech 2016, San Diego, AIAA-2016-1950 (pdf).
- Arya, M., Lee, N., and Pellegrino, S. (2015). Wrapping thick membranes with slipping folds. 2nd AIAA Spacecraft Structures Conference, 5-8 January 2015, Kissimmee, FL. AIAA 2015-0682 (pdf).