Piezoelectric polymers in space

Piezoelectric polymer films developed by a

research team, that might one day serve as ultra-light mirrors in space telescopes, will be launched into low Earth orbit (LEO) for the first time in 2007.

Sandia Labs' experimental package of promising polymers will be part of a NASA experiment on the upcoming Materials International Space Station Experiment (MISSE-6).

‘This will be the first time these polymers will be remotely operated in an actual space environment,’ Mat Celina, the project leader, said. ‘We hope to learn which polymer materials will work best in space. The materials will boldly go where they have not been before.’

Lightweight piezoelectric polymers based on polyvinylidene fluoride (PVDF) and its copolymers expand and change shape when an electric field is applied. They have not been used much in space because they degrade when exposed to the conditions of LEO, such as atomic oxygen, solar UV (ultraviolet), and repetitive temperature variations.

To be successful as space mirrors, the polymer films, which would be covered with a metallic coating, will have to be able to survive the rigors of space.

The new polymer film mirrors would be lightweight, and, because of their piezoelectric qualities, could adjust focal lengths when electrical fields are remotely applied. The research team spent the past three years developing and testing polymers in an effort to identify the ones that just might work best.

As part of the experiments the research team measured how the piezoelectric material would change in different circumstances and identified a range of materials. They also experimented with a variety of polymers, including some that were off-the-shelf and others that were specially created.

After coming up with the most promising polymers, the materials were placed in a 15cm square sample holder. This experimental unit will be launched as part of a larger suitcase-type container where experiments from a range of universities and other agencies will be assembled as well. Astronauts will attach the container to the International Space Station during a spacewalk and will open it inside out to expose the samples.

Depending on which side of the container the samples are located, they will either receive primarily vacuum UV (VUV) radiation or both VUV and atomic oxygen exposure. Both passive experiments, which are not hooked up to electric excitation, and active experiments, which will be connected to high voltage, will be flown, allowing for a range of experiments and materials to be tested over the course of the exposure.

The degradation trends and loss in performance caused by exposure to the space conditions will be monitored in real-time and logged into NASA-qualified data-loggers. When the loggers are returned to Earth, Sandia researchers will analyse the data to determine which materials were able to best survive the harsh space environment and how their performances will change with time. Celina anticipates it will take at least one year to evaluate the materials and data to decide which polymers might be best suited for space mirrors.