The Effect of Microgravity on the Oxidation of Iron Exposed to a Saltwater Solution Griffin Eslinger and Alexander Puckhaber Co-Principal Investigators Palmetto Scholars Academy North Charleston, SC

Description of Experiment Our experiment compared the structural integrity of an iron bar oxidized in the presence of saltwater in microgravity to an iron bar oxidized in the presence of saltwater on Earth.

Hypothesis  We predicted that the iron bar oxidized in microgravity would be weaker than the iron bar oxidized on Earth. Without gravity, the surface tension of the salt water will be relatively stronger. Stronger surface tension in microgravity might make the oxidation process happen at a faster pace.

Why this is Important  If we find that the iron bar oxidized in microgravity is significantly weaker than the iron bar oxidized on Earth, our findings could impact how engineers design space missions. Many pressurized spacecraft are built with iron alloys. There would most likely be oxygen and water on the inside. If rust in microgravity causes iron to become weaker than expected, there might be a high potential for catastrophic failures.

Materials Experiment Materials Type Two FME (Fluid Mixture Enclosure) 3.5% salt water solution Iron tensile testing bar (9.5mm by 75mm by 2mm) Testing Materials Tensile testing machine Scanning electron microscope

Methods 5 identical FMEs prepared and numbered (+2 old FMEs) One (Sample #2) randomly selected to go to ISS Sent up for 9 weeks in space as part of SSEP Mission 4 Upon return, tested at University of South Carolina Mechanical Engineering Department on a Tensile Testing Machine. After tensile testing, surface examined under scanning electron microscope at NOAA lab.

Tensile Testing Five properties measured Modulus of Elasticity (Young’s Modulus) Yielding Strength Maximum Strength Elongation Ductility

Tensile Results

Scanning Electron Microscope Space sample had small circular rust spots. Controls had larger plate-like rust patches. Space Earth Control

Scanning Electron Microscope The controls had a rougher surface (more rusting) and a thicker breaking cross section Space Earth Control

Summary The Iron bar that went to space: Yielding Strength: Average Elongation: Average Maximum Strength: 2nd highest Modulus of Elasticity: Average Ductility: Highest But none statistically significant SEM showed less rust and in a different pattern. Hypothesis: false, bar not weaker

Acknowledgments Thank you to the Partners and Sponsors who made this experiment possible: Partners Space and Naval Warfare Systems Command (SPAWAR) Center for the Advancement of Science in Space (CASIS) National Center for Earth and Space Science Education College of Charleston Medical University of South Carolina (MUSC) National Oceanic and Atmospheric Administration (NOAA) Sponsors ISHPI Google CASIS Palmetto Scholars Academy Board Members Palmetto Scholars Academy Families

Questions?

Closeup of Stress vs Strain Curves