The mechanical properties of eggshells are inspiring designs to protect next-generation spacecraft from collisions with space debris. A study co-authored by MIT’s Pedro Reis in 2012 had revealed the relationship between the egg’s oval geometry and its stiffness. Reis also drew on an experiment involving walking on egg cartons without breaking them: The narrow, most crack-resistant ends of the eggs should face upward, the weight should be distributed across the entire surface, and no single egg should be subjected to excessive load. It takes approximately 5.5 pounds of force to break an egg; however, the outcome depends on the direction of the force and how it is distributed across the shell.
An eggshell’s resistance to cracking comes from calcium carbonate crystals embedded in a protein matrix and reinforced by a thin collagen inner membrane. The aerospace industry used this structure as a model in failure analyses of aircraft metal shells during the 1950s and 1960s. Reis’s 2012 study supported the widespread view that leaving an egg upright was safer. However, the team of MIT’s Tal Cohen found that when energy absorption is critical, horizontal eggs can absorb more energy and undergo greater compression under the same force. In experiments, horizontal eggs dropped from the same height cracked less frequently than upright ones.
These findings were also applied to efforts to protect against space debris. According to NASA’s 2021 report, near-Earth orbit contains approximately 34,000 objects larger than 10 centimeters, approximately 900,000 objects between 1 cm and 10 cm, and approximately 128 million objects smaller than 1 cm. Even small particles can damage spacecraft because of their high speeds. Whipple shields used on spacecraft are designed to fragment the particles and spread the impact energy over a wider area.
The researchers compared 3D-printed designs consisting of aluminum plates, water-filled aluminum spheres placed between the plates, and water-filled eggshell-shaped structures through simulations and light-gas gun experiments. The most successful design reduced the velocity of projectiles by nearly 65 percent, while aluminum plates alone reduced it by 51 percent. In the most effective configuration, the eggs were vertical, with their narrow ends touching the upper plate. Although the results are promising, more experiments are needed to further develop the design. The study was published in the Journal of Applied Physics in 2026; DOI: 10.1063/5.0324502.
Why it matters
The findings show that in spacecraft shields, not only material strength but also how impact energy is distributed within the structure is a determining factor. This approach adds a different option to the principle behind existing Whipple shields of fragmenting the particle, using layers that contain water and employ egg-shaped geometries. The subject is particularly relevant to spacecraft designers and orbital safety studies affected by the risk posed by the high velocities of small particles. However, it remains unclear how the reduction in velocity observed in the experiments will hold up under actual space conditions and with different collision directions; the researchers’ statement that more experiments are needed shows that the design has not yet been validated as a viable shield. The difference between horizontal and vertical placement could also alter design decisions depending on whether the protection objective is energy absorption or reducing impact transfer.