Color change in space materials may aid in remote monitoring of deterioration

More than a dozen different materials samples will be studied to evaluate the effects of space exposure, including this carbon fiber reinforced polymer (CFRP). Credit: Sean McNeil, GTRI
More than a dozen different materials samples will be studied to evaluate the effects of space exposure, including this carbon fiber reinforced polymer (CFRP). Credit: Sean McNeil, GTRI

For the next six months, a camera system mounted on the outside of the International Space Station (ISS) will take photos of more than a dozen different material samples, gathering detailed data that will aid researchers in determining how and why the harsh conditions of space affect these materials. Color variations that may indicate deterioration induced by exposure to the environment in space are among the topics to be investigated. A key goal of the research will be to correlate color changes caused by low-Earth orbital (LEO) exposure with variations in material properties such as structural strength, chemical composition, and electrical conductivity, in order to determine how these spectral changes may allow scientists and engineers to visually assess deterioration. The destructive impacts of atomic oxygen, UV light, and high-energy electrons are all present in the LEO space environment.

Elena Plis, a senior research engineer at the Georgia Tech Research Institute (GTRI) and the team's leader, stated, "We want to know not only how space affects materials, but also why." For example, we know that a regularly used DuPont material, Kapton polyimide film, changes in conductivity in space, but we want to know why, how we can prevent it, or how we can exploit it to our advantage.

Photographing the materials on a regular basis in both the visible and infrared spectral regions will offer a dynamic record of what occurs with optical characteristics in space, expanding on information that has hitherto been confined to measurements before and after space exposure. The study team will thoroughly examine the materials returned to Earth in order to better understand how space deterioration may impact other material qualities, and this information will be used to design long-term space missions.

Plis stated, "I'm interested in the dynamics of material damage in space." Until now, we've had just two data points for measuring the consequences of spaceflight: the pristine materials we launch and the accumulated effects we may detect when they are returned. This experiment is unusual in that it allows us to observe the damage as it occurs over time.

Researchers from the Air Force Study Laboratory (AFRL), NASA, the University of Texas at El Paso, and DuPont, a multi-industrial business located in Wilmington, Del., are also part of the research team. The project, which makes use of the Materials International Space Station Experiment (MISSE) Flight Facility, is also sponsored by Aegis Aerospace Inc., the firm that owns and manages the MISSE platform deployed on the ISS. The experiment's spectral data analysis might also help observers decide whether a piece of space trash is a lightweight insulating blanket or a heavier circuit board that could damage orbiting spacecraft. Aside from giving a new method for remotely monitoring the structural health of materials and assessing the threats posed by space debris, the experiment will also assist engineers in evaluating innovative materials that might present designers of future spacecraft with new possibilities.

Plis stated that DuPont Kapton HN polyimide film, for example, has been utilized since the Apollo missions, making it the gold standard. However, there are many more materials that may have enhanced qualities, so we'll look at how some of those are influenced by space.

Many of the materials under investigation are utilized to safeguard spacecraft equipment and people against the impacts of fast heat fluctuations in orbit, as well as harmful electrical charging effects. Polyimides, liquid crystal polymers (LCP), polyhedral oligomeric silsesquioxane (POSS), carbon and glass fiber reinforced polymers, and polyethylene terephthalate (PET) polyester films are among the materials used in the MISSE-16. The samples were mounted on the ISS's exterior with a robotic arm and will be removed in the same manner in around six months. A SpaceX Dragon cargo spaceship launched on July 16 and delivered the samples to the ISS.

The MISSE testbed has been improved with a camera and lighting system to cover a greater spectral range, including infrared, which is critical for studying some elements of deterioration over time. After the GTRI-led experiment concludes, the enhanced gear will remain a component of the MISSE equipment. The one-inch square samples are slated to be returned to Earth next spring. The materials launched into orbit will be thoroughly inspected to understand deterioration and compared to identical samples subjected to laboratory-simulated space conditions. The samples will be subjected to a total of ten distinct characterization techniques, including atomic force microscopy, optical characterization of reflection and absorptance, and electrical charge transfer studies.

Plis stated that the optical qualities will be linked to surface and chemical changes. We believe that our ground experiments will help us comprehend these shifts and the physics that underpins them.

Plis, who has been researching the effects of space exposure on materials since 2015, saw the research launch into orbit as the culmination of a multi-year application and development process.

She stated, "It was very emotional for me to launch the materials." Sending my study into space and receiving data from space is like a dream come true. This is my first space project, and I hope there will be more.

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