Space & Planetary Robotics Group Aerobots for Planetary Exploration Dave Barnes Head of Space Robotics Department of Computer Science Aberystwyth University

Space & Planetary Robotics GroupSpace & Planetary Robotics Group

Aerobots forPlanetary Exploration

Dave Barnes

Head of Space Robotics

Department of Computer Science

Aberystwyth University


Planetary Exploration Methods:

• Orbiters – MGS, Mars Express

• Landers – Viking Lander I, II, Beagle 2

• Rovers – Spirit, Opportunity, ExoMars

• Aerobots – Flying robots (The Future)


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!


Aerobot Challenges:

• Mass/volume/power– (always a challenge!)

• Aerobot deployment (HTA versus LTA)• Constantly changing environment• Localisation

– Correlate science with Lat./Long./Alt.


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


ESA Martian Balloon Project:


Aberystwyth Robotic Gondola:


FEATURE AND GRADIENTMATCHING METHODS USED

Local AerobotGenerated DEM


LocalDEM(Aerobot)

GlobalDEM(Orbiter)


Global DEMDemoShell


AcceptanceTrials at theESA ESTECMars YardFacility


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


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


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)


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


Autonomous Co-operant Aerobots:

Documents

Space & Planetary Robotics Group Aerobots for Planetary Exploration Dave Barnes Head of Space Robotics Department of Computer Science Aberystwyth University