1. Space Debris: History, Major Events and Possible Mitigation and Reduction Strategies Lee Jasper University of Colorado, Aerospace Engineering PhD Student April 4, 2011Space Grant 2011 Symposium1

2. What are space debris? Anything no-longer used – Dead satellites – Rocket bodies – Ejected components Shells Bolts Micro meteoroids April 4, 2011Space Grant 2011 Symposium2

3. Why do we care? KE = ½ m v 2 – M = 1 kg – V = 7500 m/s – KE = 2.8 x 10 7 J !!!!! Lots of damage Hard to predict Hard to track April 4, 2011Space Grant 2011 Symposium3 [11]

4. History 1957 – 1978 Big Sky theory prevailed – Space is…spacious. It will never get full 1978 Donald Kessler presented the Kessler Syndrome [1] – Space is NOT spacious – Eventually, too many objects = collision is likely – One collision adds to debris, increasing chance of more collisions – CASCADE EFFECT 1996 NASDA (JAXA): Space Debris Mitigation Standard – Mid 90’s, start to consider ways to reduce debris creation April 4, 2011Space Grant 2011 Symposium4

5. History April 4, 2011Space Grant 2011 Symposium5 Orbital debris quarterly Jan 2011 2007 Chinese ASAT Test [2] 2009 Iridium-Cosmos

6. History Iridium Cosmos Collision Collision Sim ISS has had to dodge ~10 debris in 10 years April 4, 2011Space Grant 2011 Symposium6 [7]

7. History Galaxy 15 in 2010 – ‘Zombie Sat’ [3] – Lost communications, near collisions w/ neighbors April 4, 2011Space Grant 2011 Symposium7 [8]

8. Tracking Space Situational Awareness – ~20,000 objects tracked – No smaller than a softball (CubeSat size, remember amount of energy in 1kg?) – Estimated 500,000 objects between 1cm-10cm – Estimated millions of objects below 1cm (less dangerous) [10] April 4, 2011Space Grant 2011 Symposium8

9. Mitigation Can significantly reduce future issues by limiting debris creation now – Much larger field than is presented here! General Method: Passivation – Use all fuel – vent tanks – Allow batteries to continually discharge Reduce discarded/short use objects Have de-orbit/re-orbit plan April 4, 2011Space Grant 2011 Symposium9

10. Mitigation – LEO/GEO LEO – Drag: Problems – Above 800 km, long decay times – Atmosphere becoming less dense? April 4, 2011Space Grant 2011 Symposium10

11. Mitigation – LEO/GEO GEO – re-orbiting – 300+ km above GEO This is above solar-radiation-pressure variance – Depends upon area-to-mass ratio Problems – No one is directly liable/responsible for enforcement – 1997-1998: 37 satellites retired, only 9 re-orbited [8] April 4, 2011Space Grant 2011 Symposium11

12. Reduction - LEO Obviously mitigation may help reduce future additions to debris, but what about current problems? April 4, 2011Space Grant 2011 Symposium12 [4] Removal of only 5+ objects/year Trends reduce significantly! Major contributors like rocket bodies [4]

13. Reduction - GEO Possible use of Electrostatic forces [6] April 4, 2011Space Grant 2011 Symposium13 V2, q2, m2 V1, q1, m1 L Thrust

14. Current Research Performance studies – Semi-major axis changes – Fuel usage – How to model non-spherical shapes April 4, 2011Space Grant 2011 Symposium14

15. Current Research Low-thrust trajectories April 4, 2011Space Grant 2011 Symposium15 [9]

16. Conclusions Cascade ‘Kessler Syndrome’ has begun to occur Environment is currently very cluttered! Mitigation techniques are very important Active debris removal can reduce the growth April 4, 2011Space Grant 2011 Symposium16

17. References [1] Kessler, Donald J., and Cour-Palais, Burton G., "Collision Frequency of Artificial Satellites' The Creation of a Debris Belt." Journal of Geophysical Research, Vol. 83, issue A6, 1978, pp. 2637-646. [2] Covault, Craig. "Chinese Test Anti-Satellite Weapon." Online posting. AviationWeek.com. The McGraw-Hill Companies, Inc., 17 Jan. 2007. Web. 11 Nov. 2010. [3] Ferster, Warren. "Intelsat Loses Contact with Galaxy 15 Satellite." Online posting. Space News. Imaginova Corp., 8 Apr. 2010. Web. 11 Nov. 2010.. [4] A sensitivity study of the effectiveness of active debris removal in LEO J.-C. Liou, Nicholas L. Johnson, 16 July 2008. Acta Astronautica 64 (2009) 236–243 [5] Orbital Debris Quarterly News, Volume 15, issue 1 January 2011. http://www.orbitaldebris.jsc.nasa.gov/index.html [6] Schaub, Hanspeter, and Daniel F. Moorer. "Geosynchronous Large Debris Reorbiter: Challenges and Prospects." AAS/AIAA Kyle T. Alfriend Astrodynamics Symposium AAS 10-311, California, (2010). [7] "Iridium 33 & Cosmos 2251 Collide." Physics Help and Math Help - Physics Forums. Web. 6 Apr. 2011.. [8] Johnson, Nicholas L. "Protecting the GEO Environment: Policies and Practices." Space Policy 15 (1999): 127-35. Print. [9] "WMAP Observatory: Lagrange Points." Wilkinson Microwave Anisotropy Probe (WMAP). Web. 6 Apr. 2011.. [10] "NASA Orbital Debris FAQs." NASA Orbital Debris Program Office. Web. 6 Apr. 2011.. [11] LEAR, D., J. HYDE, E. CHRISTIANSEN, J. HERRIN, and F. LYONS. STS-118 Radiator Impact Damage. Rep. Print. April 4, 2011Space Grant 2011 Symposium17

18. Questions? April 4, 2011Space Grant 2011 Symposium18