Sierra Space continues to place its large integrated flexible environment (Life) habitat design through a slant. After multiple stress tests in which inflatable space station modules were filled with water until they burst like balloons, the private startup has moved to filming their latest prototypes with a hyper belt light gas gun. And, like previous exams, intense testing served an important purpose. In this case, we ensure that the shield-coated lifetime habitat module withstands the effects of dangerous microintestinal muscle style and orbital debris (MMOD).
The possibility of a massive metstone strike is a horrifying scenario with dramatic and fatal consequences, but the space station is much more likely to encounter a run-in with a much smaller space lock. For this reason, current and future orbital structures must be designed to withstand occasional panmaring from small metstones and space junks moving at very fast speeds.
Sierra Space’s Life Habitat module is constructed from a unique soft goods material called Vectran, made from chemically woven synthetic liquid crystal polymers. Although light and flexible when not in use, Vectran modules can expand to form a rigid structure that is stronger than traditional steel. However, these structures must be resilient for MMOD strikes as well, and additional composite shield layers must be designed.
For contractors like NASA and Sierra Space, this means that trip Remote Ultra-Fast Testing Institute (rhtl) White sand test facility In Las Luces, New Mexico. The RHTL operator has overseen roughly 600 test fires each year since the lab opened in 1993, and now relies on four stages of light gas guns placed in vacuum sealed chambers to simulate the MMOD conditions in space. To achieve such cosmic speed, NASA’s guns combine early stages that rely on gunpowder, which is increased by a second stage of highly compressed hydrogen gas.
Recent tests on the Sierra Space included a pair of .50 caliber guns built to replicate the impact of orbital fragments by firing projectiles at a speed of about 23,000 feet (FPS). For reference, the fastest bullet on Earth (.222 Remington round) is traversed at 3,167 fps.
“Historically, whipple shields or stuffed whipple shields have been used.” Sierra Space Mechanical Engineer Zack Masciopinto saidrefers to metal structures used at the International Space Station.
Masciopinto and colleagues are instead exploring flexible multi-shock shields. These use layers of ballistic fabric to act as “sacrifice walls” that absorb projectile impact while breaking it down into fragments.
“By the time it reaches our rear wall, no damage will occur,” he explained.
The Sierra Space experiment included two phases to determine the optimal ballistic fabric option. In the first phase, the operator fired various soft goods materials with a 0.50 caliber gun held in a fixed set of parameters to simulate MMOD events. After determining the most promising options, the researchers adjusted the gun to calculate an equation focused on the effectiveness and performance of the shield stack. A total of 40 shots were fired with the material to confirm the optimal configuration. Finally, the team made the final selection a further 19 shots to collect as much data as possible for future improvements.
“After a lot of testing… we were able to leave something very well and very efficient,” Masio Pinto said.
Sierra Space will spend the next year and a half to finalize the entire SoftGoods module system and submit NASA certification. As everything goes according to the plan, future low-earth orbit space stations can be characterized by inflatable life habitats protected from troublesome space debris.
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