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LUTH, Meudon, 21.02.2013 Siegfried Eggl

LUTH, Meudon, 21.02.2013 Siegfried Eggl. Asteroid Deflection - Why Bother?. D=7-17m M~7000 t Shallow entry. Chelyabinsk 15.02.2013. Asteroid Deflection - Why Bother?. D~45m M~??? Missed. MPC 2013. Asteroid Deflection - Why Bother?. Currently Known NEOs > 1km: (1268).

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LUTH, Meudon, 21.02.2013 Siegfried Eggl

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  1. LUTH, Meudon, 21.02.2013 Siegfried Eggl

  2. Asteroid Deflection - Why Bother? D=7-17m M~7000 t Shallow entry Chelyabinsk15.02.2013

  3. Asteroid Deflection - Why Bother? D~45m M~??? Missed...

  4. MPC 2013

  5. Asteroid Deflection - Why Bother? Currently Known NEOs > 1km: (1268) Aerospaceweb.org

  6. Currently Asked Questions Where do NEOs come from? How many are there? How many are dangerous? What can we do about them?

  7. Near Earth Object Family Tree IAU MPC 16.02.2013

  8. Where do NEOs come from? NEO lifetime ~ 106 yrs, constant replenishment necessary

  9. ~600 000 MBOs NEO lifetime ~ 106 yrs

  10. Yarkovsky Thermal Effect diurnal seasonal Bottke et al. 2006

  11. ~600 000 MBOs

  12. How many NEOs are there? What percentage do we know?

  13. NEO numbers NEOs: 9614 NEOs > 1km: 1268 PHOs: 1377 Is that „all“? IAU MPC 16.02.2013

  14. Wide-field Infrared Survey Explorer NASA mission 2010, 40 cm optics ,IR : 3-25 μm NEOWise (PI: Mainzer, A.)

  15. Wide-field Infrared Survey Explorer

  16. How many are potentially dangerous?

  17. Potentially Hazardous Objects • PHOs (1377) : • MOID <0.05 AU, • H<=22mag (D<150m)

  18. Minimum Oribt Intersection Distance • PHO (1377) : • MOID <0.05 AU, H<=22mag • (D<150m) http://orsa.sourceforge.net/atwork.html

  19. JPL 2013

  20. JPL 2013

  21. How dangerous are PHOs? Palermo Scale: compare risk of individual impact probability to background (LOG) Torino Scale: 0-10: according to impact risk and impact consequences

  22. The Palermo Scale PS= log10 R R...Relative Risk R=PI / (f x DT) PI ...Imp. Prob. DT...Time to Imp. f .....BG Imp. Prob. f= 0.03 x E -4/5 E...Imp. Energy (Mt)

  23. Impact probability? 2 body scattering b b... Impact parameter

  24. Impact probability Clones orbit uncertainty Impact probability: 1/3

  25. Impact probability 3D b-plane Uncertainty Ellipse

  26. Keyholes, 99942 Apophis b-plane 2029 x 100 [km] [km] Bancelin (2012)

  27. Line Of Variation 2011 AG5 σζ b-plane LOV σξ a: 1.43 au e: 0.39 i: 3.7° H: 21.86 Yeomans et al. (2012)

  28. 2011 AG5 close encounter 2023 Yeomans et al. (2012)

  29. What can we do?

  30. TOO EXPENSIVE

  31. NEOShield • study mitigation concepts (science+industry) • mitigation prerequisites • (asteroid physical properties, orbital uncertainty) • prepare for demo-mission • propose international emergency strategy

  32. study mitigation concepts (science+industry) • mitigation prerequisites • (asteroid physical properties, orbital uncertainty) • prepare for demo-mission • propose international emergency strategy

  33. What can we do? Teaches us a lesson not to focus all attention on one object... Tim Warchocki, National Research Council Report (2010)

  34. NeoShield Blast Deflection Gravity Tractor +Solar Sail +Ion Beam Shepherd Impactor

  35. Kinetic Impactor

  36. Kinetic Impactor Naïve calculation Momentum delivered by impactor = mimpact.ΔV Momentum change of NEO = MNEOδvNEO mimpact.ΔV = MNEOδvNEO So mass of impactor required, mimpact. = MNEOδvNEO / ΔV NEO: D = 150 m, density = 2.0 g cm-3, DT = 10 years, miss distance required = 3 x R_Earth, ΔV achievable = 10 km s-1, mimpact. = 21 tonnes! (cf. Ariane 5 payload capacity: 10 metric tons to GTO).

  37. Kinetic Impactor Somewhat less naïve calculation mimpact. = MNEOδvNEO / (ΔV x β), β …. “momentum multiplication factor” due to momentum carried off by the collision ejecta. NEO: D = 150 m, density = 2.0 g cm-3, DT = 10 years, miss distance required = 3 x R_Earth, ΔV achievable = 10 km s-1, β = 5??: mimpact. = 4.3 tonnes (cf. previous 21 tonnes with β = 1) (cf. Ariane 5 payload capacity: 10 metric tons to GTO). ??? β??? AVOID DESTRUCTION OF NEO!!!

  38. Kinetic Impactor Numerical Simulations Jutzi, Benz, Michel (2008) Laboratory Experiments

  39. Deep Impact (NASA, 2005) Target: Comet 9P/Tempel a: 3.124 au, e: 0.517, i: 10.5° m: 7-8 1013 kg Impactor mass: 384kg Change in pericenter: 10m Change in Period: 1s

  40. Kinetic Impactor • Two test mitigation mission proposals in Europe: • Don Quichote (Deimos, Belló et al. (2003), NEOShield) Single Asteroid • AIDA/DART (Cheng, A. F., Rivkin, A., Galvez, A., et al. 2012. ) Binary Asteroid • DON‘T TARGET/PRODUCE PHOs!

  41. Kinetic Impactor Difficulties • Achieve high ΔV (retrograde orbit, hit NEO at pericenter, impactor mass…) • Yet low enough ΔV for accurate targeting: auto GNC! • Avoid destruction • Need prior information on NEO (spin, structure, mass) • Full phase for targeting Saks et al. (2012)

  42. Blast Deflection

  43. Blast Deflection vs Kinetic Impactor mass of kinetic impactor = 4.3 tonnes , ΔV = 10 km s-1, K.E. = 2.1 x 1011 J ~ 5.0 x 10-5 Mt (1 Mt = 4.184×1015 J). Yield of largest H-bomb tested ~ 50 Mt! (1961). R-36 Russian ICBM ~ 20 Mt to LEO Even if not all of the energy will be imparted on NEO, still “afterglow” propulsion Limiting NEO diameter ~ 3 km

  44. Why Not Nuke Everything? • Non weaponization of space (Outer Space Treaty) • Avoid destruction (radioactive debris!) • Prior information on NEO composition needed • Not tested at all (buried, surface, stand-off blast?)

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