Quartz Glass Versus Acrylic Plastic in Spacecraft Windows
Cheaper and lighter acrylics may replace quartz glass in spacecraft, but only if they are tough enough.
Windows in spacecraft are not just for looking through and photographing planet Earth and the stars in the universe. They are an important part of the spacecraft’s pressure shell, whose role is to protect astronauts as well as withstand temperatures close to 1,000 degrees C during the craft’s re-entry into the Earth’s atmosphere.
In the past, crewed spacecraft ranging from the Apollo capsules to the Shuttle and the International Space Station have used quartz glass in windows. The craft’s structural integrity was ensured by a multiple panes of glass that could not only withstand high temperatures and pressures but also do so without cracking.
All is set to change with NASA’s Orion spacecraft, the first of which had its maiden test flight in December last year. The Orion craft will form part of NASA’s latest programme for renewed manned space travel. It aims to take astronauts into deep space and beyond the Earth’s orbit.
The challenge here, however, will not just be space, or even a future manned landing on Mars, but economics. The days of a blank government cheque for funding NASA’s space programmes are long over. Today, cost savings are the key when purchasing construction materials and in fuel efficiency.
A lighter spacecraft is a more fuel-efficient spacecraft. This has persuaded NASA scientists to examine the use of alternative glass materials for spacecraft windows. But the technical stipulation has been that the new material should not have a significantly lower transparency than glass so that astronauts can take high-resolution images in space.
Polycarbonates are neither tough enough nor transparent enough. But acrylic plastics may meet the need. Often used in tanks in public aquaria, acrylics are tough. They are also light enough to significantly reduce the spacecrafts weight, But acrylics’ ability to withstand a sustained high load over many months of space travel is still questionable.
NASA is conducting tests on acrylics to determine this. The aim is to replace two out of three panes in a window with acrylics, leaving one made of quartz glass. NASA is also saving money by recycling old glass from Shuttle windows.
Quartz glass will continue to be used in future spacecraft. But now this tough material faces competition from a plastic upstart.
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