Brief overview of lunar surface environment Examples of rover types and designs Steering systems Static and dynamic stability

Brief overview of lunar surface environment Examples of rover types and designs Steering systems Static and dynamic stability 2007 David L. Akin - All rights reserved http://spacecraft.ssl.umd.edu

Lunar Highlands (as imagined in 1950 s)

Lunar Highlands (reality)

Lunar Regolith Broken down from larger pieces over time Major constituents Rock fragments Mineral fragments Glassy particles Local environment 10-12 torr Meteorites at >10 5 m/sec Galactic cosmic rays, solar particles Temperature range +250 F -250 F

Regolith Creation Process Only weathering phenomenon on the moon is micrometeoritic impact! Weathering processes Comminution: breaking rocks and minerals into smaller particles Agglutination: welding fragments together with molten glass formed by impact energy Solar wind spallation and implantation (miniscule) Fire fountaining (dormant)

JSC-1 Simulant Ash vented from Merriam Crater in San Francisco volcano field near Flagstaff, AZ K-Ar dated at 150,000 years old ± 30,000 Major constituents SiO 2, TiO 2, Al 2 O 3, Fe 2 O 3, FeO, MgO, CaO, Na 2 O, other <1% Represents low-ti regolith from lunar mare MLS-1 simulant (U.Minn.) preferred for simulation of highland material

von Karman - Gabrielli Diagram

Surveyor Seven mission May 1966 - January 1968 (5 successful) Mass about 625 lbs Surveyor 6 performed a hop November 1967 4 m peak altitude, 2.5 m lateral motion

Lunar Roving Vehicle Flown on Apollo 15, 16, 17 Empty weight 460 lbs Payload 1080 lbs Maximum range 65 km Total 1 HP Max speed 13 kph

Lunakhod 1 and 2 Soviet lunar rovers 2000 lbs 3 month design lifetime Lunakhod 1 November, 1970 11 km in 11 months Lunakhod 2 January, 1973 37 km in 2 months

Mars Pathfinder Sojourner rover flown as engineering experiment 23 lbs, $25M Design life 1 week Survived for 83 sols (outlived lander vehicle) Total traverse ~100 m

Mars Exploration Rovers Two rovers landed on Mars in January 2004 Design lifetime 90 days, 1 km Both at 1-year mark Spirit 4030 m Opportunity 2075 m

Huygens Probe Titan entry January 2005 Descent imaging used to survey surface at different scales Wind motion provided horizontal traverse of surface

Skid-Steer Rover (ET) 14 Terramechanics Planetary Surface Robotics

Electric Tractor (JSC)

ET Suspension

ET in Hilly Terrain

Nomad (CMU)

Nomad in Rough Terrain

Nomad Transforming Chassis

Nomad Chassis/Steering System

Steering Schemes

Nomad Steering Schemes

Marsokhod (in NASA Ames

Marsokhod Chassis

Robby (JPL)

Ratler (Sandia Labs)

Split-Body Rovers (Sanida Labs)

Rocky

Rocky 4

Rocky 7

Sojourner

FIDO (JPL)

Field Trials for New Mobility Technologies

SCOUT (JSC)

Robonaut/Centaur (JSC)

ATHLETE (JPL)

Static and Dynamic Stability Envelope h = 1.75 m x t = 1.5 m x l = 1.0 m x t x l Stability Region h

Linear Acceleration 0-60 (sec) Accel (m/sec) Apparent G angle (Earth) Apparent G angle (Moon) 30 0.89 5.2 29.2 20 1.34 7.8 40.0 15 1.79 10.3 48.2 10 2.68 15.3 59.2 8 3.35 18.9 64.5 6 4.47 24.5 70.3 5 5.36 28.7 73.4

Linear Deceleration Stopping distance (m) Deceleration (m/sec^2) Apparent G angle (Earth) Apparent G angle (Moon) 20 0.43 2.5 15.2 15 0.58 3.4 19.9 12 0.72 4.2 24.3 10 0.87 5.1 28.5 8 1.09 6.3 34.1 6 1.45 8.4 42.1 4 2.17 12.5 53.6 2 4.34 23.9 69.8

Dynamic Stability Conditions θ crit,l = 29.7 deg θ crit,t = 40.6 deg m V 2 R m dv dt mg θ crit,l h mg θ crit,t

Effects of Slopes on Stability m V 2 R m dv dt mg mg θ crit,l θ crit,t