Polymer mirrors ready for space test

16 Aug 2006

Thin, reflective piezoelectric polymer films could replace traditional polished mirrors in space telescopes. But first they need to survive the rigours of space.

Researchers in the US have developed piezoelectric polymer films that could one day serve as ultralight mirrors for space telescopes. The team, based at Sandia National Laboratories, is now planning to send the polymers into orbit for testing onboard the International Space Station.

"Traditional mirrors have reached their limits in terms of weight and size. Polymer films would be a lot lighter, allowing for larger objects and fundamentally different adaptive optics approaches," Mat Celina, head of the research team at Sandia, told optics.org. "This is the first time that these polymers will be tested in an actual space environment. The films need to be optically perfect, controllable and without vibrations."

The team has developed films from a variety of polymers based on polyvinylidene fluoride (PVDF), which exhibit a strong piezoelectric response. This would allow the focal length of the mirrors to be adjusted as the polymers expand and change shape when an electric field is applied.

However, these polymer materials degrade quickly in the inhospitable low-earth-orbit environment, where they are exposed to atomic oxygen, solar UV, and repeated extreme temperature variations. Over the past three years, the researchers have tried to understand how the polymers degrade and to identify trends in their performance loss, which has enabled them to rate the materials based on their chemical and micro-structural makeup.

The most promising polymers have now been placed in an experimental holder that astronauts will attach to the outside of the International Space Station in 2007. "Only a validation experiment in the real space environment will provide the needed performance feedback," said Selina.

The samples should be returned in late 2007 or early 2008, depending on the Space Shuttle schedule. "Samples will then be evaluated based on retention of piezo features, surface degradation, morphology changes and general damage to the polymers," commented Selina.

According to Selina, the polymers could have other applications in large antennae, transmitters, or solar light reflectors -- which, placed on the Earth's surface, could even reduce global warming by reflecting the Sun's rays back into space.