Space may seem empty, but it contains temperature extremes, high levels of background radiation, micrometeoroids, and unfiltered glare from the sun. Additionally, materials and equipment outside the International Space Station are exposed to atomic oxygen (AO) and other charged particles as it orbits Earth at the edge of our atmosphere. Only the toughest materials, equipment, and organisms can withstand this harsh environment, and scientists conducting research in the orbiting laboratory have identified some of them for a variety of potential uses.
“There are ways to test the different components of space exposure individually on the ground, but the only way to get the combined effect of all of them at the same time is in orbit,” says Mark Shumbera of Aegis Aerospace, who owns and operates the MISSE Flight Facility (MISSE-FF), a space exposure study platform on the station. “This is important because the combined effects can be very different from the individual effects.”
Missions are launched approximately every six months to MISSE-FF, which is sponsored by the ISS National Lab. The experiments began when the platform was installed in 2018 and will continue for the life of the space station, Shumbera said. A former MISSE facility in operation from 2001 to 2016 hosted the first in-station exposure experiments.
Some of these missions help researchers understand how new technologies react to the space environment. “Before you use any technology on a satellite or an operational vehicle, you want to be sure that it will work the way you expect it to in the space environment,” he says.
MISSE-FF has high-definition cameras that take periodic photos of all elements of its exposure decks and sensors to record environmental conditions such as temperature, radiation, and UV and AO exposure . All test items are also returned to the ground for post-flight analysis.
NASA scientists have flown several missions on the MISSE-FF to analyze the effects of atomic oxygen and radiation on hundreds of samples and devices.
MISSE-9, for example, assessed how polymers, composites and coatings manage exposure to space. For this and other MISSE missions, Kim de Groh, a senior materials research engineer at NASA’s Glenn Research Center in Cleveland, is testing for two main environmental degradation effects. The first is how quickly a material erodes due to AO interaction. It measures mass loss in materials exposed to space and uses this information to calculate AO erosion yield values. These values help spacecraft designers determine whether specific materials are suitable for use and what thickness those materials should be.
Materials used for spacecraft insulation can become brittle in space due to radiation and temperature cycles in orbit. This embrittlement can create cracks and cause problems such as overheating of a spacecraft component. De Groh also tests the durability of different materials to find those that resist brittleness.
“The ideal situation is to actually expose samples to space, to experience all of the harsh environmental conditions at the same time,” de Groh explains.
The ESA (European Space Agency) EXPOSE-R-2 facility is another platform that offers scientists the opportunity to test samples in space. ESA investigations that have used the facility include BOSS and BIOMEX, which have exposed biofilms, biomolecules and extremophiles to space and Martian conditions. Extremophiles are organisms that can live in conditions that are intolerable or even deadly for most life forms.
The increased range is essential for future missions that travel farther from Earth and cannot rely on resupply missions. According to Daniela Billi, a professor in the Department of Biology at the University of Rome Tor Vergata and a researcher for BOSS and BIOMEX, microorganisms that tolerate extreme conditions have potential uses in life support systems for such missions. For example, cyanobacteria can use available resources to fix carbon (convert atmospheric carbon dioxide into carbohydrates) and produce oxygen.
During exposure on the space station, the dried cells of Chroococcidiopsis received a dose of ionizing radiation equivalent to a trip to Mars. Their response suggests that the bacteria could be transported around the planet and rehydrated on demand. The dried cells were also mixed with a regolith or Martian dust simulant and given a UV dose corresponding to approximately 4 hours of exposure on the Martian surface.
“The purpose of this study was to test whether this cyanobacterium could repair DNA damage accumulated during travel to Mars and exposure to unmitigated Martian conditions,” says Billi.
Recently published results suggest that they can: DNA sequencing of cells rehydrated after exposure showed no increase in mutation rate compared to controls grown under terrestrial conditions. This result increases the potential for using this organization to utilize locally available resources to support human settlements.
Another investigation using the EXPOSE-R-2 facility revealed signs of life in fungi containing melanin after 16 months of exposure to space. Fungal melanin pigment appears to play a role in cellular resistance to extreme conditions, including radiation, and may have potential for use as radiation protection in future deep space missions. In the experiment, a thin layer of a strain of melanized fungus reduced radiation levels by nearly 2% and potentially as much as 5%.
In addition to fungi, researchers used ESA’s platform to expose the resting stages of some 40 species of multicellular animals and plants in space for the EXPOSE-R IBMP survey. The results showed that many of these organisms remained viable and even completed life cycles and reproduction over several generations, suggesting that future journeys to other planets could bring terrestrial lifeforms for use in ecological systems of life support and to create artificial ecosystems.
As humans explore further into space and stay there longer, testing on the space station’s exposure platforms helps ensure that the materials and systems they take are ready for use. the trip.
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Exposed! The International Space Station tests organisms and materials in space