Part 2 of 2 Parts (Please read Part 1 first)
Parabolic reflectors are an obvious choice for use in space applications because they either pick up or send information in a specific direction. However, their bowl-shape makes it inconvenient to store in a launch vehicle with limited room. This is an even bigger problem when many antennas need to be launched on the same vehicle.
It turns out that origami engineering is a solution to the problem of launching parabolic antennas. With this technique, a flat, two dimensional structure can be folded into complex three dimensional shapes. If parabolic antennas can be made into flat shapes by using origami, then they can be stacked or rolled up inside of a launch vehicle package. When they are ready to be deployed in orbit, they can be unrolled and folded into their functional parabolic shape. Hartl explained that folding a piece of flat material into a smooth bowl shape is difficult and non-intuitive. (I have to admit that I have absolutely no intuitive idea of how it could be done.)
Hartl said, “Conventional origami design entails folding thin sheets of material at sharp creases. Engineering structures, on the other hand, have a thickness, and the choice of material can make it hard to get these sharp creases. Consequently, we need to create folds that exhibit smooth bending.”
In order to facilitate paper-like folding at the creases, Hartl’s team employed shape-memory composites that change their shape when they are heated. In addition, these composites are inexpensive, light, flexible and they are capable of being stretched multiple times without being damaged.
First, the team built a flat two-dimensional surface using strips of shape-memory composites and card stock. Pieces of stiff cardstock are used to form flat facets which are held together by pieces of the shape-memory composite. This is similar to how the radial ribs in an umbrella hold the fabric in an inverted bowl-shape. At the vertices where the composite sections meet, the team cut tiny holes to serve as corner creases when the assembly folds into a three-dimensional parabola in orbit.
When the composites are heated, they change their shape by bending systematically and lift the cardstock pieces into the parabola bowl-shape. As mentioned above, tests show that their origami antenna functions as well as a regular parabolic antenna.
Hartle said that his research in an important step using the principles of origami to construct highly functional engineering structures that can be stored compactly and easily deployed after launch. He also said, “In addition to other applications, future advances based on this research will likely result in morphing reflector antennas for military and space telecommunication applications.”
Other members of Hartl’s team include Sameer Jape, Milton Garza and Dr. Dimitris Lagoudas from the aerospace engineering department; Joshua Ruff and Francisco Espinal from the Department of Electrical and Computer Engineering; Deanna Sessions and Dr. Gregory Huff from Pennsylvania State University; and Edwin A Peraza Hernandez from the University of California, Irvine.
There is a bright future for technical origami in the space industry.