Aiming at the Whipple protective structure with a front plate of 3 mm 6061-T6 aluminum alloy and a rear plate of 3 mm 6061-T6 aluminum alloy, two different projectiles were used to conduct experimental research on the low-velocity impact Whipple protective structure. The relationship between the corresponding damage mode and the kinetic energy property of the projectile was analyzed. At the same time, the penetration velocity limit of the Whipple protective structure was explored to obtain the damage characteristics of this protective structure under cm-level low-velocity impact. The damage characteristics of the small projectile to the protection mechanism within the relative impact velocity of 650 m/s provide theoretical and technical support for the later spacecraft reinforcement optimization design.