May 6th, 2009 18:59 EST
An interview with Reuben Garcia, Composites Team Leader
Q: Is it important to do our composites in-house?
Yes. Translating designs into actual airframe components often involves on-the-spot adjustments that would be time-consuming and expensive if XCOR had farmed out its composites work. We can make changes in real time and that saves time and money.
In-house capability is even more important during flight tests. When we tested the second generation rocket plane I found that my experience of making the modifications to the airframe helped a lot as we evaluated the test results.
Q: Is it difficult to use composites?
Composites construction is far more complicated and subtle than it looks. Composites include fiberglass, carbon fiber, Kevlar, and a whole variety of epoxy resins and fillers. Each combination provides different levels of strength, weight, and temperature resistance. They can also vary widely in cost and difficulty to use. For example, some cure at room temperature, while other resins have to be cured with heat in ovens. The foam cores used in a composite structure also have to be checked for their ability to retain shape and strength in a vacuum or when subjected to heating.
Q: Why is XCOR using different types of composites for the high fidelity test articles?
We use lower cost and easier to use traditional composites on the first version, or high fidelity test articles, of most of the Lynx components. When you are building a part the first time, you are working from drawings. The first attempts lets you see for the first time, how everything really does fit together. Going through the process also lets us see how we will actually build the flight article. We usually have to make modifications. More conventional composites allow us to make the changes a lot more easily, and since these first versions of the components won`t be used on a flying vehicle, the heavier weight of the traditional composite materials is not a drawback.
Q: Does it matter how you use the composite material?
Composites come in woven sheets. The direction of the threads, and how they are laid in plies determines the strength and characteristics of the composite part you are building. So it is very important to build a test article to ensure your design will work.