Penetrators for Europa

1. Penetrators for Europa Rob Gowen on behalf of UK Penetrator Consortium MSSL/UCL UK

2. Detachable Propulsion Stage Point of Separation PayloadInstruments PDS (Penetrator Delivery System) Penetrator Europa Penetrators • Low mass projectiles ~4Kg+PDS • High impact speed ~ 200-500 m/s • Very tough ~10-50kgee • Penetrate surface ~0.5-few metres • Perform science from below surface

3. Penetrator Payload/Science A nominal 2kg payload … • Seismometers - interior structure (existence/size of subterrannean ocean) and seismic activity • Chemical sensors – subsurface refactory/volatile (organic/ astrobiologic (e.g. sulphur mass spec) material arising from interior • Mineralogy/astrobiology camera – subsurface mineralogy and possible astrobiological material • Accelerometers – hardness/layering/ compositionof subsurface material. (future landing site assessment) • Thermal sensors - subsurface temperatures • + other instruments – beeping transmitter, magnetometer, radiation sensors, etc… • descent camera (surface morphology, landing site location) Micro-seismometer Imperial College Ion trap spectrometer Open University

4. Science/Technology Requirements • Target • Region of upwelled interior material (e.g. sulphur). • 2 penetrators would allow improved seismic results and natural redundancy. • Lifetime • Only minutes/hours required for camera, accelerometer, chemistry, thermal & mineralogy/astrobiologic measurements. • An orbital period (~few days) for seismic measurements. (requires RHU) • Spacecraft support • ~7-9 years cruise phase, health reporting

5. Preliminary Estimated Mass

6. Lunar-A and DS2 space qualified. Military have been successfully firing instrumented projectiles for many years to comparable levels of gee forces into concrete and steel. 40,000gee qualified electronics exist (and re-used). Currently developing similar penetrators for MoonLITE. Payload heritage: Accelerometers, thermometers, sample drill, geophone – fully space qualified. Seismometers (ExoMars) & chemical sensors (Rosetta) heritage but require impact ruggedizing. Mineralogy camera – new but simple. Heritage When asked to describe the condition of a probe that had impacted 2m of concrete at 300 m/s a UK expert described the device as ‘a bit scratched’!

7. Impact Trial19-21 May 2008 • Full-scale trial • 3 Penetrators, ~0.6m long, ~13kg, Aluminum • 300m/s impact velocity • Normal Incidence • Dry sand target 0.56m

8. Impact trial - Contributors

9. Impact trial – Payload Mass spectrometer Radiation sensor Batteries Magnetometers Accelerometers Power Interconnection Processing Micro-seismometers Accelerometers, Thermometer Batteries,Data logger Drill assembly

10. Impact Trial Objectives Demonstrate survivability of penetrator shell, accelerometers and power system. Determine internal acceleration environmentat different positions within penetrator. Extend predictive modelling to new impact and penetrator materials. Assess impact on penetrator subsystems and instruments. Assess alternative packing methods. Assess interconnect philosophy.

11. Trial Hardware - Status Inners Stack

12. Impact Trial - Configuration • Rocket sled • Penetrator

13. Target • Dry sand • 2m x2m x6m • Small front entrance aperture (polythene)

14. Firing

15. 1’st Firing - Results • Firing parameters: • Impact velocity: 310 m/s • (c.f. 300m/s nominal) • Nose-up ~10degs (c.f. 0 degs nominal) • => worst case • Penetrator found in top of target in one piece ✓ • Glanced off steel girder which • radically changed its orientation • Much ablation to nose and belly • Rear flare quite distorted. • Penetration: ~3.9m

16. First Firing – Opening up • s

17. 1st Firing – internal Results Micro seismometer bay Connecting to MSSL accelerometer and data processing bay

18. 1’srt Firing – QinetiQ accelerometer data Initial impact hi-res: Tail slap peak Overview: 5 kgee smoothed, ~16 kgee peak high frequency components ~5khz

19. 1’st Firing – MSSL accelerometer data Along axis: • Main: 10kgee • Cutter: 3kgee • Girder: 1kgee Along axis Vertical axis Horizontal axis

20. Hi-res MSSL accelerometer data Lots of high frequency structure

21. 2nd & 3rd Firings • All 3 firings remarkably consistent ~308-310m/s velocity, and ~8-10 degs nose up. • 2/nd firing penetrator hit steel beam square on. • Penetrators survived all 3 firings. Payload still operational. Steel nose for 3rd firing

22. Survival Table Triple worst case: exceed 300m/s, >8deg attack angle No critical failures – currently all minor to unprotected bays or preliminary mountings

23. Impact Trial Objectives Demonstrate survivability of penetrator shell, accelerometers and power system. Determine internal acceleration environmentat different positions within penetrator. Extend predictive modelling to new impact and penetrator materials. Assess impact on penetrator subsystems and instruments. Assess alternative packing methods. Assess interconnect philosophy.

24. Next Steps… • next trial – aim for Jan’09. • impact into harder material (ice,icysand,concrete) • full up system (all operating) • transmit from target • imminent funding for analysis and further hardware development.

25. Penetrators Conclusions • Acheived major step in demonstrating confidence in technology • No great history of failure - only 1 planetary delivery to date • Significant TRL with previous space qualified technology • A useful tool in the toolbox of planetary exploration • Capable of addressing fundamental astrobiology signatures and habitability • Provide ground truth & new information not possible from orbit • Provide useful landing information for future missions. Penetrator website: http://www.mssl.ucl.ac.uk/planetary/missions/Micro_Penetrators.php email:rag@mssl.ucl.ac.uk

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