OPTIMIZATION OF ROVER WHEEL GEOMETRIES FOR PLANETARY MISSIONS

Rovers have been launched into space for exploration of the Moon and Mars to collect samples of rock and soil. To continue the explorations, the rovers need to have reliable wheels to drive around. However, due to the soil being soft, the wheels on the rover start to lose traction and the wheels sink while driving to various locations. Previous work in this field has been done experimentally or with the use of simulations. Only a few references report the effect of uncertainties in grouser simulation on the traction efficiency. The objective of this work was to (a) Understand the effect of uncertainties on wheel traction efficiency, and (b) Design a rover wheel, consider those uncertainties, and then compare results with deterministic optimization. The results are categorized into three different sections. The first section shows the result of a closed-form equation for rover traction efficiency. A closed-form equation was obtained using three different formulas from previous work. The second section provides results on a reliability analysis to understand the effects of uncertainty on traction efficiency. The uncertainty variables chosen were the empiric soil parameter, , the weight of the wheel, w, and the width of the wheel, b. The third section has a result of using the reliability-based design for the wheel considering those uncertainties, in which the design parameters are the normalized height of the grousers, , the width of the wheel, b, the radius of the wheel, r, and finally the weight of the wheel, w. In the reliability-based optimization there are two variables that are considered uncertain which are not the design parameters, the soil parameter and torque. In the design parameters, the radius of the wheel is considered uncertain. Once the optimized values are obtained, they are compared to the deterministic optimization. As a result, optimized design variables were obtained

Optimization of Rover Wheel Geometries for Planetary Missions

Rovers have been used extensively on exploration and sample collection missions to the Moon and Mars. Challenging prospective missions require rovers that have reliable wheels to navigate the harsh conditions of the planetary regolith. However, due to the regolith being soft the wheels on the rover start to lose traction and the wheels sink while driving. The goal of this work is to optimize the grouser geometry to improve wheel traction and sinkage simultaneously facilitating better rover maneuvering. This research will be conducted by changing different parameters of the grouser\u27s height, number of grousers, and shape of the grousers. Novel geometries will be analyzed using LIGGGHTS and Paraview software. Recommendations will be made towards optimizing the wheel performance on planetary surface missions. MATLAB will be the first to use to optimize the grouser geometry and then input into LIGGGHTS and processed in Paraview. For validating the work, high-fidelity simulations will be performed along with sensitivity study

Magneto Active Slosh Control System - MAPMD

Sloshing poses a serious challenge in the design of satellites, spacecraft and launch vehicles. Sloshing can be affected by either passive or active measures. Passive slosh damping through either fixed internal baffles or other propellant management devices (PMD) is effective for low-amplitude slosh at low fill fractions but is less effective for higher fill fractions and higher amplitude slosh. Further it reduces the available propellant volume inside the tank and requires significant mass budget to implement effectively. The Magneto-active Propellant Management Device (MAPMD) system includes the membrane floating on the propellant surface and a control system that utilizes low-power electromagnetic coils to detect the position of the membrane within the tank, assess the slosh state of the liquid within the tank, and apply appropriate magnetic forces to the floating membrane to suppress incipient slosh. The slosh test bed at Embry-Riddle Aeronautical University (ERAU) is an experimental setup consisting of a dynamic force balance with three movable arms attached to a single axis actuator from Aerotech called Linear Motion Actuator (LMA). A pair of FUTEK LCM 300 (Tension and Compression) dynamic load cell is attached at the end of each movable arms. The sensitivity of the load cell is rated at 250 lbs or 1112 N. These load cells measure the forces acting on tank walls and resolve them into forces and moments. Motion of the actuator is accomplished by a custom built LabVIEW code coupled with Aerotech’s soloist CP software at Embry-Riddle Aeronautical University. The test tank is a clear polycarbonate cylindrical vessel of diameter 6 inches and length 8 inches. The external control system consists of two external wire coils each consisting of 100 turns of 12-AWG magnet winding wire, and (2) programmable DC power supplies capable of providing 1A of current at 12V. The coils are spaced at intervals equal to the coil radius, effectively creating a series of Helmholtz Coils. The Helmholtz configuration is advantageous because it creates a region of uniform magnetic field between two coils when the current supplied to each coil is the same. As a result, over 90% of the tank volume can be subjected to a constant, static magnetic field enough to stiffen the membrane and suppress slosh. The proposed MAPMD addresses all the challenges stated above through a simple, innovative solution that could prove to be cost effective and lead to better control performance of satellites, space craft and launch vehicles

Fabrication of Rocket and Payload Bay Area

The objective of the Suborbital Technology Experimental Vehicle for Exploration research project is to design and build a Level 3 Rocket that can serve as a research platform for launching and testing payloads. The development of this research project will help students to test various size payloads and science experiments to gauge future efforts to design and develop larger payloads for larger suborbital or orbital national and international platforms. Final rocket design, specifications, and payloads are being constructed at the Payload Applied Technology Operations (PATO) lab using state-of-the-art materials, manufacturing and 3D printing techniques. The design and fabrication of the payload bay area was optimized to have four TubeSats and two Nanolabs. By using ANSYS static structural analysis, the preliminary results simulate the maximum acceleration loads that the payload will experience during the main parachute deployment. Through this analysis, the resulting maximum acceleration load the payload would experience was determined to be 310 m/s^2 (12,174 in/s^2). Another observation made through this analysis was the location of the maximum stress, located on the connecting rods. The deformations observed are protected by the structure of the payload. The design for the coupler tubes and nose cone have been finalized and are ready to be fabricated. Fabrication of rocket components, such as coupler tubes, nosecone, and motor tube, are being carried out within the Aviation Maintenance Science (AMS) building using fabrication techniques such as CNC machining. After the carbon fiber hand layup of the motor tube, it was necessary to sand the motor tube to its desired diameter of 0.273 m (10.75 inches) and machine the fin alignment jig to make it sturdier. Working with this department, the fabrication of the motor tube and the alignment jig, used for fin alignment, have been completed

Suborbital Payload Testing Aboard Level 3 Rocket Research Platform

Embry-Riddle Aeronautical University (ERAU) has launched several suborbital scientific payloads aboard Blue Origin’s New Shepard in 2017 and 2019. Students continue gaining hands-on experience in rocket design and construction, and payload integration and testing of future and more mature payloads to be launched into space. A Level 3 Rocket is being designed and developed at ERAU to serve as a scaled-down model research platform for launching and testing of payloads that will be later flown in commercial suborbital platforms such as Blue Origin’s New Shepard and PLD space Miura 1 rockets. Computer simulations were conducted to calculate the key parameters such as flight trajectory profiles, stability and flight velocities for different rocket motors configurations. A preliminary design of the rocket was developed using Computer-Aided Design (CAD) software. The rocket will accommodate multiple payloads (Cubesats, NanoLabs, TubeSats) designed and developed in the Payload Applied, Technology and Operations (PATO) laboratory. The rocket will be primarily constructed of carbon fiber composite as it has a high strength to weight ratio. These simulations are used to select a suitable motor for the rocket according to the flight requirements and landing restrictions. This prospective Level 3 Rocket is referred to as Suborbital Technology Experimental Vehicle for Exploration (STEVE). Rocket procedures and results from the design, simulation, construction and assembly will be presented