Martian Coat Bracket
A lightweight structural bracket designed to support loads in low-gravity environments
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Problem
On Mars, the reduced gravity lessens the weight of objects, but structural components still experience significant forces during movement, impacts, and assembly. Our task was to design a lightweight bracket for a Martian coat-hanging system that could support loads without failing, while minimizing mass to reduce launch costs. The first design buckled under compression during early testing, showing that conventional assumptions about load direction and support conditions were insufficient for this unique environment .
Solution
We redesigned the bracket to place its main beam in tension rather than compression, shifting the pinned connection to the top of the structure and adding an L-shaped form for lateral support. This change eliminated buckling while keeping the part compact and lightweight. The final bracket withstood the target loads while weighing only 4.19 grams, making it efficient for transport while structurally sound under Martian conditions.
We began by analyzing the first design using free-body diagrams and hand calculations. While the part passed static stress predictions, physical testing revealed early failure through buckling, which our initial analysis underestimated.
This failure led us to rethink the load path and support points entirely. We repositioned the pinned connection to place the beam primarily in tension, which acrylic handles better than compression. Adding an L-shaped configuration created lateral stability and distributed forces more evenly.
After incorporating these changes, we validated the new design with both calculations and FEA simulations. It showed no signs of buckling and maintained a safe factor of safety while remaining extremely lightweight, meeting both performance and efficiency requirements for use in a Martian environment.
Initial Ideation and Design Process
Design 1 used a horizontal beam under compression with two pinned ends, but testing revealed instability and premature buckling. For Design 2, the beam was reoriented under tension, and the support points were moved to improve stability. The redesign also added an L-shaped profile for extra lateral stiffness .
Stress Analysis and FEA
Hand calculations showed maximum axial stress of 1710.81 psi and shear stress of 18.35 psi on the highest-loaded section. FEA confirmed a similar stress distribution, with a minimum factor of safety of 2.01, aligning with calculations given the acrylic’s yield strength of about 9400 psi .
CAD and Assembly
The final CAD model optimized material placement by pocketing low-stress regions to reduce weight. Mounting holes were precisely dimensioned, and overall geometry minimized bending moments by shortening unsupported spans. The final part weighed only 4.19 g.
Manufacturing
The bracket was laser-cut from acrylic sheet for precision and lightness. Edges were polished for safety, and holes were tolerance-tested to ensure proper fit on the support rig during loading experiments.
Continuous Improvement
Further development could involve replacing acrylic with a carbon-fiber composite for better strength-to-weight ratio, incorporating finite element topology optimization, and integrating shock-absorbing features to handle dynamic loads during Martian transport.
Impact
This project demonstrated how reframing load paths can dramatically improve performance in low-gravity contexts. By shifting from compression to tension, we created a stable, lightweight bracket that meets both structural and mass constraints for Martian use.
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Hand calculations were performed to evaluate the internal forces, shear, and bending moments on the Martian coat bracket. The structure was divided into two subsystems, and free-body diagrams were used to solve for axial, shear, and bending loads. The maximum bending stress was calculated using the flexural formula, yielding approximately 4.6 psi, which is well below the acrylic’s yield strength. These calculations helped predict stress concentrations and validate that the bracket would remain structurally safe under the expected loading conditions.
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The FEA simulation shows the factor of safety distribution for the final Martian coat bracket under the applied loading conditions. The results confirm that stress remains low across the structure, with the minimum factor of safety above 2.0, indicating sufficient strength while maintaining a lightweight form. High-stress zones are concentrated near mounting holes, while the main beam stays well within safe limits.
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The Martian coat bracket was mounted onto an aluminum frame and loaded at its end to replicate operational forces in testing. This setup allowed direct observation of its structural response, confirming that the redesigned bracket remained stable under load without buckling and performed as predicted by FEA analysis.
