Analysis and Design of a Microgravity Drop Tower

Abstract: A drop tower is a device that produces a microgravity environment by allowing an experiment to free fall for a short period of time, usually less than 10 seconds. Certain types of drop towers are also capable of reproducing the gravitational conditions of other celestial bodies, such as Lunar and Martian gravity. Microgravity environments are often required for many different scientific experiments, such as experiments in material science, fluid dynamics, biological studies and many other fields. Microgravity environments are also often used as a specialized manufacturing method for certain materials. Components and systems that will be used in space or onboard sounding rockets can also be tested and verified using drop towers before launch. There is an ever-present need to conduct experiments in a microgravity environment and thus highlights the importance and relevance of drop towers in research and design verification. Other microgravity facilities such as sounding rockets, parabolic flights and orbital spacecraft typically provide longer microgravity durations, however, come at a considerable cost. This highlights the need for drop towers that are cost-effective as a desirable research device. This thesis consists of a comprehensive, systematic literature review to determine industry standards and the current state of the art in the world of drop towers. The different potential mechanical designs of a drop tower are then analyzed and trade-offs are completed. The most suitable design, that could feasibly be built at Luleå University of Technology (LTU)’s space campus, is chosen and presented later in this thesis. The safety of the drop tower was of utmost concern when deciding on the most suitable design as well as when completing the mechanical design of the drop tower. The slider is a major component of a drop tower, it houses the experiment and is a critical component in determining the achievable microgravity quality. The slider design was also analyzed with a trade-off analysis of the potential existing designs, with the most feasible design being chosen. The drop tower is planned to be installed in the LTU Spacecampus light garden which can accommodate a drop tower of approximately 13m in height. The mechanical design is verified using various Finite Element Analysis (FEA) simulations. The 14m planned and designed drop tower is a non-vacuum, guided design which would provide approximately 3 seconds of microgravity, 5.2 seconds of Martian simulated gravity and 7.8 seconds of Lunar simulated gravity. The drop tower has been designed to accommodate projects that are part of the REXUS program. The towers' considerable size and ease of use would make it suitable for many research institutions and many potential scientific studies.