Towards a Viable Europa Penetrator

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Towards a Viable Europa Penetrator
A. Smith, R. Gowen, A. Coates, etc MSSL/UCL
I. Crawford Birkbeck College London P.
Church, R. Scott Qinetiq Y. Gao, M.Sweeting
Surrey Space Centre/SSTL T. Pike Imperial
College A. Ball Open University J. Flanagan
Southampton University
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Contents

• Introduction
• Background
• A New Start
• Science
• Feasibility
• Cost
• Technology developments
• Summary

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Introduction

• Problem How to work towards a surface element
  proposal that has both scientific and technical
  viability.
• Offer potential for unique science and ground
  truth to complement a Europa orbiter.
• Here we consider Penetrator (vs passive impactor,
  soft lander, etc).
• We present some thoughts on technology, payload
  and cost issues that could be input to an
  assessment study.

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What Characterizes micro-penetrators ?

• Very low mass projectiles 2-5Kg (c.f. Lunar A
  13.5Kg DS-2 3.6Kg)
• High impact speed 200-300 m/s
• Very tough 10,000gee
• Penetrate surface few metres
• Perform initial important science on planetary
  surface

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Mullard Space Science Laboratory
Hinode Launch 22-9-06

• Part of University College London
• 140 Staff
• In-house mechanical and electrical engineering
  design, manufacture and test
• Provided hardware or calibration facilities for
  17 instruments on 12 spacecraft currently
  operating
• Provided stereo cameras for Beagle-2
• Leading PanCam development for EXOMARS

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Penetrator Consortium

• MSSL
• Consortium lead, payload technologies, payload
  system design
• Birkbeck College London
• Science
• Imperial College London
• Seismometers
• Open University
• Science and instrumentation
• QinetiQ
• Impact technologies, delivery systems
  technologies
• Southampton University
• Optical Fibres
• Surrey Space Science Centre and SSTL
• Platform technologies, delivery system
  technologies

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A New Start

• An initial ESA technical study for a first Europa
  probe led to conclusion that there would be
  insufficient mass (1Kg) to support a survivable
  probe, to perform significant science, and that
  any development costs would be excessive.
• A following ESA TRP Empie study, aimed at a
  second Europa mission, removed the mass limit
  resulting in a feasible (at a pre- Phase A
  level), 4 probe (1.7Kg each) system which are
  axially oriented and decelerated with modest mass
  (20Kg).
• It is not clear that 20Kg is required for a first
  mission. For example a 2 probe system around 15
  Kg might be feasible if such mass were
  available.
• There is a considerable body of evidence that
  real probes (well beyond pre-phase A level)
  impacting around 300 m/s with gee forces well in
  excess of 10kgee are survivable.
• A pre-cursor Lunar mission (2010) (which could
  perform excellent science) would provide timely
  and cost effective technical developments,
  thereby reducing necessary Europa developments to
  a delta level.

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Europa Penetrator Payload Science

• Beeping Transmitter
• - For Earth based VLBI determination of
  surface ice movement
• (deformation, seismic vibration)
• Micro-Seismometers/tilt-meter
• - Detection of natural (or impact) seismic
  activity.
• - Presence and size of an under ice ocean.
• - cryo-tectonic activity
• Accelerometer
• - Determination of ice characteristics and
  penetration depth.
• Chemical Sensors - Presence, extent,
  concentration of organics (possible life
  indicators).
• - Presence, extent and concentration of other
  chemical species
• (minerals, chirality, isotopic abundances
  ?)
• Other sensors Heat flow (melting depth, internal
  structure), micro-camera (descent, surface),
  magnetometer, radiation monitor, etc.
• gt Assess science value, sensitivity, resource
  requirements, likelihood of success c.f. other
  surface/orbit alternatives

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Planetary Penetrators - History
No survivable high velocity impacting probe has
been successfully landed on any extraterrestrial
body
DS2 (Mars) NASA 1999 ?
Mars96 (Russia) failed to leave Earth orbit
?
TRL 6
Japanese Lunar-A much delayed
?
Many paper studies and ground trials
?
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Feasibility

• There is no history of failures of high speed
  (300m/s) planetary probes. Has only ever been
  one planetary deployment - Mars Polar Orbiter
  DS2 which failed alongside the soft lander.
• Military have been successfully firing
  instrumented projectiles for many years to at
  least comparable levels of gee forces expected
  for Europa.Target materials mostly concrete and
  steel.
• NASA and Japan have both developed penetrators
  and scientific instruments to withstand such high
  gee forces to TRL 8. Lunar-A passed its final
  all-up impact test this summer and is now simply
  awaiting a launch.
• Lunar-A or another Lunar technical demonstrator
  mission could provide first space demonstration
  in timescale useful to Europa mission.
• UK Penetrator consortium has plans to provide
  ground impact demonstration tests in next 2 years.

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Examples of electronic systems

• Have designed and tested electronics for high-G
  applications
• Communication systems
• 36 GHz antenna, receiver and electronic fuze
  tested to 45 kgee
• Dataloggers
• 8 channel, 1 MHz sampling rate tested to 60 kgee
• MEMS devices (accelerometers, gyros)
• Tested to 50 kgee
• MMIC devices
• Tested to 20 kgee
• TRL 6

MMIC chip tested to 20 kgee
Communication system and electronic fuze tested
to 45 kgee
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Targetting and Impact Site Issues

• Ability to impact at site of optimum scientific
  interest ?
• To land anywhere will give a high degree of
  scientific return surface composition and
  structural strength (also useful to follow on
  mission), seismometer determination of ice depth
  and event rates. Detection of organic chemicals
  will still be performed but not optimum.
• Could optimise impact ellipse zone using existing
  imagery, or during Europa approach and early
  orbit camera imagery with autonomous analysis to
  provide landing coordinates within descent system
  capabilities.
• Ability to successfully penetrate rough surface ?
• Glancing impact angle could prevent penetration.
  Study and tests required for expected ice.
• Could optimise impact ellipse as above, but with
  criteria for surface flatness/smoothness.
• Implement small pre-impact explosive to
  pre-smooth local entry surface. Defense sector
  has experience of this technology which is
  reported to be reliable. Disadvantage is
  possibility of chemical contamination of upper
  impact site which would complicate chemical
  sensing analysis.
• Ability to survive non-perpendicular surface
  impact ?
• Lunar penetrator mission limits entry to within
  around 8? of vertical, to limit possibility of
  probe failure through excess probe sideways
  stresses.
• Study required to determine if similar effects
  likely to exist for Europan ice, and to what
  degree.

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Cost

• NASA DS2 developments were characterised by
  ambitious challenges and extensive iterations.
  Japanese developments were characterised by a
  lack of pre-existing military support base
  necessitating a great deal of impact survival
  development and testing.
• UK defence sector exists with considerable
  experience including both test facilities and
  highly predictive (hydrocode) modelling
  capability which greatly reduces the need for
  extensive trials.
• Proposed UK Lunar penetrator development (which
  will address excellent science) will provide a
  significant reduction in cost for Europa.
• Possibilities for further cost saving by
  collaboration and purchase of existing
  technology.

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Technical Developments Required

• Stepwise developments Terrestrial ? Lunar ?
  Europa (very cold,
• high radiation, ice material)
• Penetrator Platform -
• (a) To Moon
• Define payload environment
• Micro attitude control (orient to survive impact
  and ensure penetration)
• Micro de-orbiting (reduce speed to survivable
  level)
• Spacecraft ejection mechanism
• Batteries (for long lifetime on surface)
• Penetrator Impact survival (design, modelling,
  test, including electronics)
• (b) Delta Developments for Europa
• Revise payload environment
• Penetration survival (Already survive
  penetration into concrete and steel !) (See
  earlier slides regarding surface conditions)
• RHU (prevent batteries becoming too cold)
• Communications (penetrator lt-gt spacecraft
  through Europan ice?)
• Radiation hard (much higher radiation level the
  Moon)

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Technical Developments Required.

• Penetrator Payload -
• (a) To Moon
• Seismometer (options, impact survival,
  sensitivity, operation)
• Chemical sensing (organic/astrobiology) (or
  access to existing technology). (various
  options - impact survival, operation
• sensitivity)
• Autonomy/data handling (affected by operations,
  comms)
• Heat flow (may also be useful on Europa)
• Descent Camera
• (b) Delta developments for Europa
• VLBI Beacons (new to Europa)
• Radiation hard (much more radiation than Moon)
• Further options/developments

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Summary

• We have proposed a new start to include
  penetrators as a useful Europa surface element in
  an assessment study for the ESA Cosmic Visions
  Jupiter-Europa Mission.
• We have demonstrated the feasibility for many of
  the key elements, and identified technical
  developments that could be necessary to achieve
  others which either may not be accessible or yet
  sufficiently mature.
• The UK penetrator consortium and PPARC proposed
  Lunar penetrator mission could provide a useful
  and timely path to assist in the assessment
  process, and help reduce costs significantly.
• Naturally we would welcome international
  participation

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