Introduction to Roving VehiclesENAE 483/788D - Principles 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

© 2009 David L. Akin - All rights reservedhttp://spacecraft.ssl.umd.edu

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Introduction to Roving VehiclesENAE 483/788D - Principles of Space Systems Design

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Lunar Highlands (as imagined in 1950’s)

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Introduction to Roving VehiclesENAE 483/788D - Principles of Space Systems Design

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Lunar Highlands (reality)

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Introduction to Roving VehiclesENAE 483/788D - Principles of Space Systems Design

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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

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Introduction to Roving VehiclesENAE 483/788D - Principles of Space Systems Design

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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)

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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

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Introduction to Roving VehiclesENAE 483/788D - Principles of Space Systems Design

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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

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Introduction to Roving VehiclesENAE 483/788D - Principles of Space Systems Design

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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

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Introduction to Roving VehiclesENAE 483/788D - Principles of Space Systems Design

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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

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Introduction to Roving VehiclesENAE 483/788D - Principles of Space Systems Design

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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

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Introduction to Roving VehiclesENAE 483/788D - Principles of Space Systems Design

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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

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Introduction to Roving VehiclesENAE 483/788D - Principles of Space Systems Design

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Skid-Steer Rover (ET)

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Introduction to Roving VehiclesENAE 483/788D - Principles of Space Systems Design

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Electric Tractor (JSC)

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Introduction to Roving VehiclesENAE 483/788D - Principles of Space Systems Design

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ET “Suspension”

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Introduction to Roving VehiclesENAE 483/788D - Principles of Space Systems Design

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ET in Hilly Terrain

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Introduction to Roving VehiclesENAE 483/788D - Principles of Space Systems Design

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Static and Dynamic Stability Envelope

Stability Region

h

xt

x!

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B

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Introduction to Roving VehiclesENAE 483/788D - Principles of Space Systems Design

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Weight on the Wheels

h xt

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Ff

Fr

r

!mg

B

!forces about rear axle

Ff = mg!"

B!xtB

#! h

B tan !$

!forces about front axle

Fr = mg!

xtB + h

B tan !"

Introduction to Roving VehiclesENAE 483/788D - Principles of Space Systems Design

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ET Science Trailer Suspension System

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Introduction to Roving VehiclesENAE 483/788D - Principles of Space Systems Design

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SCOUT Suspension and Steering System

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Introduction to Roving VehiclesENAE 483/788D - Principles of Space Systems Design

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Nomad (CMU)

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Introduction to Roving VehiclesENAE 483/788D - Principles of Space Systems Design

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Nomad in Rough Terrain

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Introduction to Roving VehiclesENAE 483/788D - Principles of Space Systems Design

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Nomad Transforming Chassis

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Introduction to Roving VehiclesENAE 483/788D - Principles of Space Systems Design

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Nomad Chassis/Steering System

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Introduction to Roving VehiclesENAE 483/788D - Principles of Space Systems Design

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Steering Schemes

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Introduction to Roving VehiclesENAE 483/788D - Principles of Space Systems Design

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Nomad Steering Schemes

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Introduction to Roving VehiclesENAE 483/788D - Principles of Space Systems Design

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Marsokhod (in NASA Ames

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Introduction to Roving VehiclesENAE 483/788D - Principles of Space Systems Design

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Marsokhod Chassis

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Introduction to Roving VehiclesENAE 483/788D - Principles of Space Systems Design

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Robby (JPL)

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Introduction to Roving VehiclesENAE 483/788D - Principles of Space Systems Design

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Ratler (Sandia Labs)

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Introduction to Roving VehiclesENAE 483/788D - Principles of Space Systems Design

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Split-Body Rovers (Sanida Labs)

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Introduction to Roving VehiclesENAE 483/788D - Principles of Space Systems Design

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Rocky

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Introduction to Roving VehiclesENAE 483/788D - Principles of Space Systems Design

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Rocky 4

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Introduction to Roving VehiclesENAE 483/788D - Principles of Space Systems Design

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Rocky 7

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Introduction to Roving VehiclesENAE 483/788D - Principles of Space Systems Design

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Sojourner

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Introduction to Roving VehiclesENAE 483/788D - Principles of Space Systems Design

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FIDO (JPL)

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Introduction to Roving VehiclesENAE 483/788D - Principles of Space Systems Design

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K10 (Small Support Rover)

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Introduction to Roving VehiclesENAE 483/788D - Principles of Space Systems Design

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SCARAB (Drilling Robot)

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Introduction to Roving VehiclesENAE 483/788D - Principles of Space Systems Design

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Apollo Lunar Roving Vehicle

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Introduction to Roving VehiclesENAE 483/788D - Principles of Space Systems Design

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Electric Tractor and Chariot (JSC)

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Introduction to Roving VehiclesENAE 483/788D - Principles of Space Systems Design

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SCOUT (JSC)

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Introduction to Roving VehiclesENAE 483/788D - Principles of Space Systems Design

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Chariot (Mobility Chassis)

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Introduction to Roving VehiclesENAE 483/788D - Principles of Space Systems Design

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Chariot B Climbs a Boulder Field

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Introduction to Roving VehiclesENAE 483/788D - Principles of Space Systems Design

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ATHLETE (JPL)

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Introduction to Roving VehiclesENAE 483/788D - Principles of Space Systems Design

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Walking Robots

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Introduction to Roving VehiclesENAE 483/788D - Principles of Space Systems Design

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Scorpion King (JSC)

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Introduction to Roving VehiclesENAE 483/788D - Principles of Space Systems Design

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Dynamic Stability Conditions

h

mg

mdV

dt

mg

mV 2

R

!crit,! !crit,t

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

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Introduction to Roving VehiclesENAE 483/788D - Principles of Space Systems Design

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Effects of 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

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Introduction to Roving VehiclesENAE 483/788D - Principles of Space Systems Design

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Linear Deceleration from 15 km/hr

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

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Introduction to Roving VehiclesENAE 483/788D - Principles of Space Systems Design

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Effects of Slopes on Stability

mg

mdV

dt

!crit,t

mg

mV 2

R

!crit,!

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