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Introduction to Roving Vehicles Principles of Space Systems Design U N I V E R S I T Y O F MARYLAND Introduction to Roving Vehicles 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

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Introduction to Roving VehiclesPrinciples of Space Systems Design

U N I V E R S I T Y O FMARYLAND

Introduction to Roving Vehicles

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

© 2007 David L. Akin - All rights reservedhttp://spacecraft.ssl.umd.edu

Introduction to Roving VehiclesPrinciples of Space Systems Design

U N I V E R S I T Y O FMARYLAND

Lunar Highlands (as imagined in 1950’s)

Introduction to Roving VehiclesPrinciples of Space Systems Design

U N I V E R S I T Y O FMARYLAND

Lunar Highlands (reality)

Introduction to Roving VehiclesPrinciples of Space Systems Design

U N I V E R S I T Y O FMARYLAND

Lunar Regolith• Broken down from larger pieces over time• Major constituents

– Rock fragments– Mineral fragments– Glassy particles

• Local environment– 10-12 torr– Meteorites at >105 m/sec– Galactic cosmic rays, solar particles– Temperature range +250°F – -250°F

Introduction to Roving VehiclesPrinciples of Space Systems Design

U N I V E R S I T Y O FMARYLAND

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)

Introduction to Roving VehiclesPrinciples of Space Systems Design

U N I V E R S I T Y O FMARYLAND

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 SiO2, TiO2, Al2O3, Fe2O3,

FeO, MgO, CaO, Na2O, other <1%• Represents low-Ti regolith from lunar mare• MLS-1 simulant (U.Minn.) preferred for

simulation of highland material

Introduction to Roving VehiclesPrinciples of Space Systems Design

U N I V E R S I T Y O FMARYLAND

von Karman - Gabrielli Diagram

Introduction to Roving VehiclesPrinciples of Space Systems Design

U N I V E R S I T Y O FMARYLAND

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

Introduction to Roving VehiclesPrinciples of Space Systems Design

U N I V E R S I T Y O FMARYLAND

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

Introduction to Roving VehiclesPrinciples of Space Systems Design

U N I V E R S I T Y O FMARYLAND

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

Introduction to Roving VehiclesPrinciples of Space Systems Design

U N I V E R S I T Y O FMARYLAND

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

Introduction to Roving VehiclesPrinciples of Space Systems Design

U N I V E R S I T Y O FMARYLAND

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

Introduction to Roving VehiclesPrinciples of Space Systems Design

U N I V E R S I T Y O FMARYLAND

Huygens Probe

• Titan entry January 2005

• Descent imaging used to survey surface at different scales

• Wind motion provided horizontal traverse of surface

TerramechanicsPlanetary Surface Robotics

U N I V E R S I T Y O FMARYLAND

Skid-Steer Rover (ET)

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Introduction to Roving VehiclesPrinciples of Space Systems Design

U N I V E R S I T Y O FMARYLAND

Electric Tractor (JSC)

Introduction to Roving VehiclesPrinciples of Space Systems Design

U N I V E R S I T Y O FMARYLAND

ET “Suspension”

Introduction to Roving VehiclesPrinciples of Space Systems Design

U N I V E R S I T Y O FMARYLAND

ET in Hilly Terrain

Introduction to Roving VehiclesPrinciples of Space Systems Design

U N I V E R S I T Y O FMARYLAND

Nomad (CMU)

Introduction to Roving VehiclesPrinciples of Space Systems Design

U N I V E R S I T Y O FMARYLAND

Nomad in Rough Terrain

Introduction to Roving VehiclesPrinciples of Space Systems Design

U N I V E R S I T Y O FMARYLAND

Nomad Transforming Chassis

Introduction to Roving VehiclesPrinciples of Space Systems Design

U N I V E R S I T Y O FMARYLAND

Nomad Chassis/Steering System

Introduction to Roving VehiclesPrinciples of Space Systems Design

U N I V E R S I T Y O FMARYLAND

Steering Schemes

Introduction to Roving VehiclesPrinciples of Space Systems Design

U N I V E R S I T Y O FMARYLAND

Nomad Steering Schemes

Introduction to Roving VehiclesPrinciples of Space Systems Design

U N I V E R S I T Y O FMARYLAND

Marsokhod (in NASA Ames

Introduction to Roving VehiclesPrinciples of Space Systems Design

U N I V E R S I T Y O FMARYLAND

Marsokhod Chassis

Introduction to Roving VehiclesPrinciples of Space Systems Design

U N I V E R S I T Y O FMARYLAND

Robby (JPL)

Introduction to Roving VehiclesPrinciples of Space Systems Design

U N I V E R S I T Y O FMARYLAND

Ratler (Sandia Labs)

Introduction to Roving VehiclesPrinciples of Space Systems Design

U N I V E R S I T Y O FMARYLAND

Split-Body Rovers (Sanida Labs)

Introduction to Roving VehiclesPrinciples of Space Systems Design

U N I V E R S I T Y O FMARYLAND

Rocky

Introduction to Roving VehiclesPrinciples of Space Systems Design

U N I V E R S I T Y O FMARYLAND

Rocky 4

Introduction to Roving VehiclesPrinciples of Space Systems Design

U N I V E R S I T Y O FMARYLAND

Rocky 7

Introduction to Roving VehiclesPrinciples of Space Systems Design

U N I V E R S I T Y O FMARYLAND

Sojourner

Introduction to Roving VehiclesPrinciples of Space Systems Design

U N I V E R S I T Y O FMARYLAND

FIDO (JPL)

Introduction to Roving VehiclesPrinciples of Space Systems Design

U N I V E R S I T Y O FMARYLAND

Field Trials for New Mobility Technologies

Introduction to Roving VehiclesPrinciples of Space Systems Design

U N I V E R S I T Y O FMARYLAND

SCOUT (JSC)

Introduction to Roving VehiclesPrinciples of Space Systems Design

U N I V E R S I T Y O FMARYLAND

Robonaut/Centaur (JSC)

Introduction to Roving VehiclesPrinciples of Space Systems Design

U N I V E R S I T Y O FMARYLAND

ATHLETE (JPL)

Introduction to Roving VehiclesPrinciples of Space Systems Design

U N I V E R S I T Y O FMARYLAND

Static and Dynamic Stability Envelope

Stability Region

h

xt

x!

x! = 1.0 m

xt = 1.5 mh = 1.75 m

Introduction to Roving VehiclesPrinciples of Space Systems Design

U N I V E R S I T Y O FMARYLAND

Linear Acceleration

“0-60” (sec) Accel (m/sec) Apparent G angle (Earth)

Apparent G angle (Moon)

30 0.89 5.2 29.220 1.34 7.8 40.015 1.79 10.3 48.210 2.68 15.3 59.28 3.35 18.9 64.56 4.47 24.5 70.35 5.36 28.7 73.4

Introduction to Roving VehiclesPrinciples of Space Systems Design

U N I V E R S I T Y O FMARYLAND

Linear Deceleration

Stopping distance (m)

Deceleration (m/sec^2)

Apparent G angle (Earth)

Apparent G angle (Moon)

20 0.43 2.5 15.215 0.58 3.4 19.912 0.72 4.2 24.310 0.87 5.1 28.58 1.09 6.3 34.16 1.45 8.4 42.14 2.17 12.5 53.62 4.34 23.9 69.8

Introduction to Roving VehiclesPrinciples of Space Systems Design

U N I V E R S I T Y O FMARYLAND

Dynamic Stability Conditions

h

mg

mdV

dt

mg

mV 2

R

!crit,! !crit,t

!crit,! = 29.7 deg !crit,t = 40.6 deg

Introduction to Roving VehiclesPrinciples of Space Systems Design

U N I V E R S I T Y O FMARYLAND

Effects of Slopes on Stability

mg

mdV

dt

!crit,t

mg

mV 2

R

!crit,!