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Space & Planetary Robotics GroupSpace & Planetary Robotics Group
Aerobots forPlanetary Exploration
Dave Barnes
Head of Space Robotics
Department of Computer Science
Aberystwyth University
Space & Planetary Robotics GroupSpace & Planetary Robotics Group
Planetary Exploration Methods:
• Orbiters – MGS, Mars Express
• Landers – Viking Lander I, II, Beagle 2
• Rovers – Spirit, Opportunity, ExoMars
• Aerobots – Flying robots (The Future)
Space & Planetary Robotics GroupSpace & Planetary Robotics Group
Aerobot Advantages:• High resolution surface imaging• Can touch (land) as well as see (image)• Landing site selection• Rover guidance• Data relay• Sample site selection• Payload delivery and surface science• Atmospheric science• Can go where rovers cannot!
Space & Planetary Robotics GroupSpace & Planetary Robotics Group
Aerobot Challenges:
• Mass/volume/power– (always a challenge!)
• Aerobot deployment (HTA versus LTA)• Constantly changing environment• Localisation
– Correlate science with Lat./Long./Alt.
Space & Planetary Robotics GroupSpace & Planetary Robotics Group
Localisation Challenge:
• No GPS!• Cannot always see the stars• Anomalous localised magnetic regions• Cannot commit orbital resources full time• Cannot commit terrestrial “ “ “• Line-of-sight not always possible
Space & Planetary Robotics GroupSpace & Planetary Robotics Group
FEATURE AND GRADIENTMATCHING METHODS USED
Local AerobotGenerated DEM
Space & Planetary Robotics GroupSpace & Planetary Robotics Group
LocalDEM(Aerobot)
GlobalDEM(Orbiter)
Space & Planetary Robotics GroupSpace & Planetary Robotics Group
AcceptanceTrials at theESA ESTECMars YardFacility
Space & Planetary Robotics GroupSpace & Planetary Robotics Group
Tethered AerobotPayload Calculations:
Displaced_Mars_atmosphere_mass × Mars_gravity = Total_balloon_mass × Mars_gravity
Neutral Buoyancy (N.B.) Example
Point of N.B.
millimetres
Kg
onacceleratimassForce
Balloon lift inthis region
Space & Planetary Robotics GroupSpace & Planetary Robotics Group
Neutral Buoyancy Equation:
ρA = Density of Martian atmosphereρHe = Density of Helium on MarsρE = Density of envelopeEt = Thickness of envelopeMscience = Mass of scienceMtether = Mass of tetherMnotional = Contingency massradius = Envelope radius
Mass ofDisplaced
atmosphere
Mass ofHelium inEnvelope
Mass ofBalloon
Envelope
volume
massDensity
3
3
4_ rSphereVolume
24__ rSphereAreaSurface
Space & Planetary Robotics GroupSpace & Planetary Robotics Group
Engineering Data:
Density of Helium at landing site (ρHe) 1.198 × 10-3 kg/m3
Density of Martian atmosphere at landing site (ρA) 0.013 kg/m3
Density of HDPE envelope (ρE) 0.95 × 103 kg/m3
Thickness of HDPE envelope (Et) 0.008 × 10-3 m
Mass of Kevlar-49, 0.25 mm diameter per km (Tether) 0.288 kg/km
Assume a) High Density Polyethylene (HDPE) envelopeb) Tether is made from Kevlar-49 material
c) 20% mass contingency
For a given envelope radius and tether length (i.e. balloon altitude in Km),then the mass of the science payload can be calculated:
MsciencealtitudeTetherEtErrHerA
233 4
3
48.0
3
4
20% contingency
(Use Ideal Gas Lawto calculate atmosphereand Helium densitieson Mars)
Space & Planetary Robotics GroupSpace & Planetary Robotics Group
The Next 50 years (or less!):
• Aerobots will be used routinely for planetary exploration• Aerobots will work with surface resources (e.g. rovers)• Aerobots will be used on Mars, Titan, Venus• Aerobot swarms (‘flocks’) will be used