The engineering design of a 115 m microgravity drop tower facility within atmospheric condition
摘要
This study presents the engineering design, analysis, and experimental validation of a microgravity drop tower facility capable of providing approximately 3.26 s of microgravity under atmospheric conditions. Unlike conventional vacuum-based systems, the proposed approach employs a free-fall method within a 115 m vertical shaft, combined with a dual-capsule configuration to mitigate aerodynamic drag and enhance microgravity quality. A theoretical model describing the relative motion between the outer and inner capsules was developed based on drag-induced acceleration differences. The analysis demonstrated that minimizing the drag coefficient of the outer capsule is essential for maximizing the effective microgravity duration by delaying contact between the two capsules. Aerodynamic stability was achieved through appropriate center-of-gravity and center-of-pressure design, supported by a streamlined capsule geometry and rear-mounted fins. To enable safe and reusable operation, a multi-layered airbag recovery system was designed and validated through numerical simulations and repeated drop tests. Experimental results demonstrated a total drop time of 4.74 s and a microgravity duration of 3.26 s within the inner capsule. Acceleration measurements showed good agreement with simulation predictions, with peak residual accelerations below 10− 3g and an effective microgravity quality approaching the 10− 4g level during the stable free-fall period. High-speed video analysis was further performed to quantify the relative motion between the inner and outer capsules, revealing that the inner capsule advanced relative to the outer capsule more rapidly than predicted by the simplified analytical model. This observation provides a plausible explanation for the reduction in the experimentally obtained microgravity duration and identifies the release mechanism and capsule interaction as important subjects for future investigation. Additional qualitative experiments, including flame shape observation and object behavior tests, further confirmed the successful realization of microgravity conditions. The proposed facility provides a practical, low-cost platform capable of performing approximately six to seven experiments per working day, offering a viable alternative to conventional vacuum-based drop towers for repeated microgravity research.