Introduction to Roving Vehicles -...
Transcript of Introduction to Roving Vehicles -...
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
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Lunar Highlands (as imagined in 1950’s)
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Lunar Highlands (reality)
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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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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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von Karman - Gabrielli Diagram
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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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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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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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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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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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Huygens Probe
• Titan entry January 2005
• Descent imaging used to survey surface at different scales
• Wind motion provided horizontal traverse of surface
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Electric Tractor (JSC)
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ET “Suspension”
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ET in Hilly Terrain
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Nomad (CMU)
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Nomad in Rough Terrain
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Nomad Transforming Chassis
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Nomad Chassis/Steering System
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Steering Schemes
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Nomad Steering Schemes
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Marsokhod (in NASA Ames
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Marsokhod Chassis
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Robby (JPL)
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Ratler (Sandia Labs)
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Split-Body Rovers (Sanida Labs)
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Rocky
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Rocky 4
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Rocky 7
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Sojourner
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FIDO (JPL)
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Field Trials for New Mobility Technologies
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SCOUT (JSC)
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Robonaut/Centaur (JSC)
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ATHLETE (JPL)
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Static and Dynamic Stability Envelope
Stability Region
h
xt
x!
x! = 1.0 m
xt = 1.5 mh = 1.75 m
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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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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
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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