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B.L.A.S.T: The NASA BOARDS Launch Acceleration Simulation Tool

        Background

         Research is being conducted on the effects of space travel on the human brain by submitting stem cell samples, called brain organoids, to the International Space Station to determine the effect of micro-gravity. During this process the brain organoids will experience forces due to acceleration according to a Falcon 9 launch. In order to provide a control for this experiment, the Arthur C. Clarke Center, in collaboration with SpaceTango, has requested a centrifuge for their experiment boxes be designed that will mimic the acceleration profile experienced during launch.

   One of the experiment boxes sent aboard the ISS.

SpaceX Falcon 9 Launch Profile

        Objective

         In order to provide a controlled environment for the conditions in which the brain organoids will experience on the trip to and back from the ISS, a centrifuge-like device is required to emulate the acceleration profile of launch and recovery forces. An acceleration profile similar to those experienced during launch is shown below. The final product should be able to recreate this profile with less than 10% error, and will be configurable in order to use different box designs and acceleration profiles. To this end, there is a racking counterweight system, and the sling design can accommodate multiple box sizes. The final design will also include a fully functional user interface and braking system to be used in the event of an emergency stop.

           The typical acceleration profile during a Falcon 9 launch.

        Final Design

            Once manufactured, the final design will be driven by a Vex Robotics CIM motor geared 50:1. The arm is attached to the motor via the center stack assembly, which transmits power from the motor while the bearings minimize friction. The center stack assembly also contains a brake mounted on top, which is used to stop the arm's rotation suddenly when needed to more accurately replicate the acceleration profile shown below. The brake is used in conjunction with back-driving the motor, is powered by an external power source, and is also set to be used in the event of an emergency stop.The arm is balanced on one side with a removable counterweight assembly, whose weights can be changed out to accommodate different sized loads. One the other side, the CubeLab is bolted to a sheet metal sling, which allows the system to more precisely replicate the conditions of launch by controlling the direction of the resultant acceleration. This entire assembly is contained within a hexagonal frame made of aluminum extrusion, which is in turn covered by a removable polycarbonate safety covering. During the manufacturing process, it is expected that the users will be able to interact with the microcontroller through a Linux-run single board computer, as well as a physical e-stop switch. The majority of machined parts are to be made of aluminum 6061-T6 alloy, with the exception to this being the counterweight assembly, which will be machined from AISI 1020 steel alloy.

CAD model of the completed assembly.

        Summary of Performance Results

            Dynamic simulation of the model determined that a 2 degree of freedom design was the best choice for this particular use case. The arm will need to rotate at a maximum speed of 50 RPM, which precipitated the need for the 50:1 gearbox as 50 RPM is a relatively low speed to run this motor at. The arm also needs to have a torque of up to 30 Nm applied to it in order to correctly replicate the acceleration curve given to it. Modal analysis of the chassis indicated that the maximum speed of centrifuge in operation produces a frequency of 1.6Hz.

Animation showing operation at approximately 40 RPM.

        Link to Executive Summary

        See Reports folder for Executive Summary.

        Final Presentation