Given how high-tech spacecraft tend to be, I was surprised to learn that existing space vehicles tend to use good old-fashioned glass (albeit a rather expensive kind). But for the next-gen Orion spacecraft, NASA has been working overtime to find something stronger, lighter, and just a little less fragile.
The historical preference for glass is down to its optical properties, which allow for all the kinds of high-res photographs of space that we know and love. But according to NASA, glass weakens under sustained pressure — not ideal on a years-long expedition to Mars (or anywhere else for that matter).
So for the Orion spacecraft, NASA is trialling acrylic materials — ironically, the same thing used in aquariums across the country. It retails glass's high-quality optical properties, whilst dramatically decreasing the weight and thickness. The first Orion test mission flew with some acrylic panes, and as you can see from the awesome photo of a very damp re-entry vehicle above, they all survived the flight intact.
The next step is stress-testing the acrylic for long periods, which involves subjecting panes to high pressure for months on end. No-one said interplanetary travel was easy. [NASA]