Correlating the Impact Severity of Spherical and Non-Spherical Projectiles at Hypervelocity

The design of spacecraft protection against orbital debris (OD) is generally based on experiments and models involving spherical projectiles. However, observations of collision fragments from ground-based satellite impact experiments have shown that orbital debris is non-spherical in shape. To accommodate non-spherical projectiles in spacecraft protection measures, a relationship between spherical projectiles and their threat-equivalent non-spherical counterparts was established. Cylindrical projectiles featuring adjustable Length-to-Diameter (L/D) ratios were employed to simulate the projectile shape effect on the bumper performance under hypervelocity impact. The L/D ratio spanned a range from L/D = 1/3, representing a “flake” shape, through L/D = 1 for a “nugget” configuration and extended up to L/D = 5/3, representing a “straight rod” configuration. The numerical analysis utilized the smoothed-particle hydrodynamics technique, demonstrating that projectile geometry significantly influenced the threat posed by projectile fragments to the objects behind the bumper. The established projectile threat relationship can be applied to assess the ability of the existing OD bumpers to withstand non-spherical projectiles by representing them with an equivalent sphere. Utilizing this approach can contribute to decreasing uncertainty and enhancing the protection of spacecraft when encountering irregularly shaped OD particles.