Initial Concept Review Team Alpha ALUM Rover (Astronaut Lunar Utility Mobile Rover) Friday, October 30, 2009 1830-2030 GMT
Rover Requirements/Capabilities Performance Requirements Keep up with an astronaut (estimated top speed 1.5m/s) Drive over a 30cm obstacle Drive on a 20 deg slope in any direction with nominal payload Payload accessible for 5%ile female through 95%ile male Accommodate all lunar thermal environments Self-contained power supplies for 8 hour EVA Size Requirements Max stowed mass: 100 kg Max stowed dimension: 2 m Max stowed volume: 3 m^3 Capabilities Capable of independent missions Capable of self-tended recharging
ASU Mission Requirements Mission: o Land in Oceanus Procellarum (20 o N, 40 o W) Exploration with astronauts o Continue in autonomous/tele-operated mode after astronauts depart Rover should survive a minimum of 3 months on lunar surface Scientific Objectives o Remotely identify rock composition o Ability to catalog samples of interest (location, spectrum) o Observe surface morphology o Test obstacle avoidance methods to be used by future autonomous rovers
ASU Instrumentation Heritage Science Instruments o Thermal Emission Spectrometer Based on MER Mini-TES Remote detection of rock composition o Two visible light cameras with a CMOS image sensor Based on MER PanCam Stereo images/panoramas of surroundings Assess the topography, mineralogy, and geological context around the landing site Microscopic Imager o Color CCD sensor o Document rocks and regolith
ALUM Rover High Gain Antenna Navigation Mast (Stereo and Omnidirectional Cameras) Payload Module Robotic Arm Battery Module Tweel Hub-mounted Brushless DC Motor Dust Guard Avionics
Rover Dimensions 1.4 m 1.2 m 1.6 m
Modular Approach Payload Modules Astronaut Tool Modules Sample Collection Modules Life support module for extended duration EVAs Science instruments Hinged bar restrains modules
Power System Power Requirements Torque = 40 N*m, max speed = 1.5 m/s 91W / wheel Assume 75% efficiency => 500W total for the wheels Plus power to run equipment Total (estimated) energy required = 5kW-hr Considerations Lithium-sulfur batteries (rechargeable): high specific energy density 500-600 Wh/kg Lithium-ion batteries (rechargeable): 100-160 Wh/kg Solar panels Total Capacity 10 kw-hr (theoretical)
Wheel Rationale Pros Cons Pneumatic Mechanically Simple Pressure vessel, Thermal Response Aluminum Mesh Offers shock absorption Used on LRV Limited life due to fatigue Tweel Offers shock absorption on par with pneumatic New technology, needs to be adapted to lunar environment Design choice: Tweel Considerations 1.Durable and superior performance 2.Currently being developed for lunar applications
Steering Selection Pros Cons Skid Steer Mechanically Simple Kicks up Too Much Dust Inefficient Steering Single Ackerman 4W Steer More efficient turning Won't kick up as much dust as Skid Steering Can perform any type of steering Can turn in place Increased Complexity and Mass Each wheel would require a steering motor Design choice: Single Ackerman Rationale: Astronauts won't be restricted to moving in straight lines, especially when navigating rough terrain Astronauts will be working in close proximity to the rovers, making dust an increased concern
Suspension Rationale Pros Cons Active Suspension Navigate rugged terrain Increased complexity, Requires computation Double Wishbone Passive, proven technology (LRV) Significant Mass MacPherson Strut Passive, low-mass Limited ability to tune kinematics Design choice: MacPherson strut Rationale: Passive system frees computational power Traverse speed is high Photo courtesy of Honda
Stability Stability on Flat Terrain o Accelerations up 1m/s^2 o At v = 1m/s, radius of curvature 1m o At v = 0.5m/s, radius of curvature 0.2m Stability on 20 deg slope: o Accelerations up to 0.4 m/s 2 20 deg upslope o At v=1m/s, radius of curvature of 2m o At v=0.5m/s, radius of curvature up to 0.5m
Mass Budget Item Quantity Mass (kg) Total Mass (kg) Wheel 4 4 16 Batteries - 20 20 Visible light camera2 0.3 0.6 Wheel motors 4 2 8 Gearboxes 4 2 8 GNC Computer - - TBD High gain antenna 1 6 6 Low gain antenna 1 6 6 Suspension and Structure - - TBD Solar Panels - 5 5 TOTAL - - 69.6
Rover Operation on EVA The astronaut will be able to... Operate rover using controls on suit Assign scientific tasks o Picking up rock samples o Use of instruments Set waypoints for the rover View images and data from the rover on a viewscreen Approach and access rover without the rover moving
Astronaut Control on EVA Arm-mounted control panel with viewscreen o See what rover sees o Touchscreen to set targets for travel or manipulation o Display navigation information Laser pointer to designate targets o Waypoints o Instruct rover to manipulate samples with robotic arm Image by SAIC
Astronaut Access to Rover Rover height was chosen based on work envelopes of 5th percentile females and 95th percentile males Astronauts can access rear modules from behind the rover Modules carrying tools may have racks extended over the wheels for easier access
Modes of Operation between EVA and after Astronaut Departure Autonomous Reconnaissance o Scout for areas of interest between EVA's o Take images and other data and transmit to Astronauts or operators on Earth o Used to decide where to explore Teleoperation Mode o Operate the rover from habitat o Set way points for the rover o Similar control as if on EVA
Navigation and Obstacle Avoidance Astronaut Following o Rely on Astronaut's natural ability to avoid obstacles o Track and follow Astronaut's path o Keep a safe distance from the Astronaut Stereoscopic image processing o Process stereo images to identify obstacles o For use in autonomous modes, where rover speed isn't critical Positioning o IMU for relative position and orientation o Star tracker for absolute position
Recharging During crew mission Rover will also use stereo vision to dock with charge port After crew departure Before crew departs, a solar panel will be placed on the rover to provide power
Bibliography Bell, J F., et al. (2003), Mars exploration rover athena panoramic camera (pancam) investigation. Journal of Geophysical Research, 108(E12), 8063. Christensen, P R., et al. (2003), Miniature thermal emission spectrometer for the Mars exploration rovers, Journal of geophysical research 108.10.102. Edgett, K S., et al. (2009), The Mars Hand Lens Imager (MAHLI) aboard the Mars rover, Curiosity, Lunar and Planetary Institute Contribution 1505, p. 5. Taylor, L. (1991), Helium abundances on the moon: Assumptions and estimates, Arizona Univ., Resources of Near-Earth Space: Abstracts p 40 (SEE N91-26019 17-91).
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