Directed Energy System Concepts for Asteroid Threat Mitigation

Michael McVicker

ASTE-527

Directed Energy Systems

• Scalable systems that focus energy on target’s surface for the purpose of vaporization, trajectory deflection, and general threat mitigation.
• Earth or Sun orbiting
• Ground based
• DE-STAR classic example

12/17/2013

Directed Energy System Concepts for Asteroid Threat Mitigation

2

Directed Energy Systems

• Solid state or chemical lasers
• Phased array of densely packed laser collimators
• Planar array of phase-locked lasers that focus at long distance targets
• Many more benefits

Boeing YAL-1

HELLADS

​

Navy Laser Weapon System

​

Voronstov Adaptive Phase Array

12/17/2013

Directed Energy System Concepts for Asteroid Threat Mitigation

3

Asteroid Classification

253 Mathilde (66 x 48 x 46 km)

433 Eros ( 24.4 x 11.2 x 11.2 km)

21 Lutetia (121 x 101 x 75 km)

12/17/2013

Directed Energy System Concepts for Asteroid Threat Mitigation

4

Asteroid Types

Monolithics

• Sizes range from pebbles to small planetoids
• Often porous
• Unbounded spin rates

Rubble Piles

• Larger than 150 m diameter
• Slower spin rates (< 1 rev/2.2 hr)
• Held together by weak g forces

​

25143 Itokawa (535 x 294 x 209 m)

253 Mathilde (66 x 48 x 46 km)

12/17/2013

Directed Energy System Concepts for Asteroid Threat Mitigation

5

Observed Bodies

12/17/2013

Directed Energy System Concepts for Asteroid Threat Mitigation

6

“Classical” Mitigation

• Common asteroid mitigation techniques
• Vaporize it
• Blow it up
• Alter trajectory
• Worst case feasible scenario
• Detection at 1 AU from impact
• ~1 year lead time

12/17/2013

Directed Energy System Concepts for Asteroid Threat Mitigation

7

Two Alternative Methods

Resonance Destabilization

Spin-Destabilization

12/17/2013

Directed Energy System Concepts for Asteroid Threat Mitigation

8

Resonance Destabilization

• Monoliths are typically very solid, and fast spinning
• If vaporization or deflection is not an option, directed energy systems could potentially pulse to resonantly destabilize the asteroid.

12/17/2013

Directed Energy System Concepts for Asteroid Threat Mitigation

9

Resonance Destabilization Rationale

• Mechanical resonance amplifies vibrations if the pulsing matches the natural frequency of the
• Theoretically, the vibrating energy could quickly amplify until the structure fractures

​

12/17/2013

Directed Energy System Concepts for Asteroid Threat Mitigation

10

Resonance Destabilization Conclusion

• The asteroid does not have the means to dampen the internal vibrations, except through heat radiation and changing its internal structure (i.e. fracturing)
• If the directed energy can hone in on the resonant frequency, it could easily crack a rotating monolithic M-Type asteroid faster than any other method
• Sweeping or vaporization with directed energy can continue on remaining threats
• More work and analysis to be done

​

12/17/2013

Directed Energy System Concepts for Asteroid Threat Mitigation

11

Spin-up Destabilization Rationale

• Rubble piles are far more numerous and threatening in terms of size to Earth than monoliths
• Because of low gravity, rubble pile asteroids must spin slower than one rotation every 2.2 hours (or ~0.0008 rad/s)
• Most asteroids already initially spinning

12/17/2013

Directed Energy System Concepts for Asteroid Threat Mitigation

12

Spin-up Destabilization Rationale

• Ablative thrust and photonic momentum exchange applies torque to target body
• Once ~0.0008 rad/s spin is achieved, centripetal forces overcome gravitational forces
• Result is a buckshot-field of debris that could take years to gravitationally re-assemble
• Sweep the directed energy across the field to apply delta-v to individual smaller masses
• Typically, bodies smaller than 20 m will not make it through Earth’s atmosphere

​

​

12/17/2013

Directed Energy System Concepts for Asteroid Threat Mitigation

13

Spin Destabilization Analysis

• Assumptions
• Average density = 2000 kg/m³
• Initial rotation rate is 0 rpm (worst case scenario)
• Thrust applied at furthest point from CM, parallel to surface
• During spin-up, no mass is lost from the body
• Target will actually fling off mass to lower angular momentum as it spins up, which in effect means a lower moment of inertia
• Ellipsoid spinning about semi-major axis (not minor)
• Ellipsoid: a = r, b = 0.75r, c =0.75r

12/17/2013

Directed Energy System Concepts for Asteroid Threat Mitigation

14

Spin Destabilization Conclusion

• Ellipsoid Case
• Vaporization more effective for targets smaller than 150 m
• Results for spin-destabilization:
• Average ablative thrust (Newton)
• Diameter of asteroid for one year to spin-destabilize

10¹N

10² N

10³ N

10⁵ N

10⁷ N

82 m

260 m

820 m

2600 m

8200 m

12/17/2013

Directed Energy System Concepts for Asteroid Threat Mitigation

15

Conclusion

• Directed Energy Systems offer many options
• Vaporization
• Trajectory Alteration
• Resonance Destabilization
• Spin-Destabilization
• Further modeling and research necessary

​

12/17/2013

Directed Energy System Concepts for Asteroid Threat Mitigation

16

Resources

• Philip Lubin ; Gary B. Hughes ; Johanna Bible ; Jesse Bublitz ; Josh Arriola ; Caio Motta ; Jon Suen ; Isabella Johansson ; Jordan Riley ; Nilou Sarvian ; Deborah Clayton-Warwick ; Jane Wu ; Andrew Milich ; Mitch Oleson ; Mark Pryor ; Peter Krogen ; Miikka Kangas; Directed energy planetary defense. Proc. SPIE 8876, Nanophotonics and Macrophotonics for Space Environments VII, 887602 (September 24, 2013); doi:10.1117/12.2030228.
• Vorontsov, M.A.; Weyrauch, T.; Beresnev, L.A.; Carhart, G.W.; Ling Liu; Aschenbach, K., "Adaptive Array of Phase-Locked Fiber Collimators: Analysis and Experimental Demonstration,"Selected Topics in Quantum Electronics, IEEE Journal of , vol.15, no.2, pp.269,280, March-april 2009
• "Asteroid Fast Facts." Asteroid and Comet Watch (blog), November 3, 2011. http://www.nasa.gov/mission_pages/asteroids/overview/fastfacts.html (accessed December 8, 2013). http://neo.jpl.nasa.gov/ca/
• "Impact Risk." Near Earth Object Program(blog), December 8, 2013. http://neo.jpl.nasa.gov/risk/ (accessed December 8, 2013).
• Britt, D.T., Yeomans, D., Housen, K., and Consolmagno, G., Asteroid Densities. EAR-A-5-DDR-ASTEROID-DENSITIES-V1.1. NASA Planetary Data System, 2002.
• Statler, Tom. "Rotation of Near-Earth Asteroids." http://www.phy.ohiou.edu/~tss/NEA_Rotation.html (accessed December 8, 2013).http://www.killerasteroids.org/images/asteroids_comets_to_scale.jpg
• Itokawa [ [Web Photo]. ]. Retrieved from http://www.psi.edu/sites/default/files/imported/pgwg/images/Itokawa.jpg
• Laser Ablation [ [Web Graphic]. ]. Retrieved from http://www.astrobio.net/images/galleryimages_images/Gallery_Image_8898.jpg
• Bekey, I.,(1997) articles.adsabs.harvard.edu/cgi-bin/nph-iarticle_query?1997ESASP.393..699B&amp;data_type=PDF_HIGH&amp;whole_paper=YES&amp;type=PRINTER&amp;filetype=.pdf
• Asteroids. ((n.d.)). Retrieved from http://nssdc.gsfc.nasa.gov/planetary/text/asteroids.txt
• Choi, C. ((2013, April 10)2013, April 10).Asteroids: Formation, discovery and exploration. Retrieved from http://www.space.com/51-asteroids-formation-discovery-and-exploration.html
• (2005, October 31). Asteroid Eros Reconstructed [ [Web Photo]. ]. Retrieved from http://en.wikipedia.org/wiki/File:WholeEros.jpg
• Mathilde [ [Web Photo]. ]. Retrieved from http://en.wikipedia.org/wiki/File:(253)_mathilde.jpg
• Petit, D. (Array). (2008, April 29). Saturday Morning Science [ [Web Video]. ]. Retrieved from http://www.youtube.com/watch?v=jXYlrw2JQwo
• (2006, October 18). Breaking a Wine Glass Using Resonance [ [Web Video]. ]. Retrieved from http://www.youtube.com/watch?v=17tqXgvCN0E
• Gustafso. Resonance. Retrieved from http://www.math.utah.edu/~gustafso/2250resonance.pdf
• (2007, June 23). [ [Web Photo]. ]. Retrieved from http://en.wikipedia.org/wiki/File:Airbornelaserturret.jpg
• (2013, April ). [ [Web Photo]. ]. Retrieved from http://www.scitechmag.com/wp-content/uploads/2013/04/HIGH-ENERGY-LIQUID-LASER-AREA-DEFENSE-SYSTEM-HELLADS.jpg
• (2013, October 04). [ [Web Photo]. ]. Retrieved from http://a.abcnews.com/images/US/ht_navy_laws_weapon_tk_130804_wg.jpg
• [ [Web Graphic]. ]. Retrieved from http://www.teachengineering.org/collection/cub_/lessons/cub_images/cub_space8_lesson03_figure2.jpg
• About optical table performance specifications. ((n.d.)). Retrieved from http://www.newport.com/About-Optical-Table-Performance-Specifications/168086/1033/content.aspx

​

12/17/2013

Directed Energy System Concepts for Asteroid Threat Mitigation

17

Backup

Ground DE-STAR over Space

Advantages

• No extreme launch or maintenance costs
• Easier to power and maintain
• Space qualification is unneeded
• Easier to evolve & upgrade
• DoD application
• Debris removal application

​

​

Disadvantages

• Tracking
• Multiple systems across the surface of Earth for continuous target engagement
• Aviation/Public concerns
• Political use
• Atmospheric effects

​

​

​

12/17/2013

Directed Energy System Concepts for Asteroid Threat Mitigation

19

Scale

• A DE-STAR 4 is 10x10 km large.
• Solar CME effects on large systems unknown
• Or 1112 Arecibo Observatories

12/17/2013

Directed Energy System Concepts for Asteroid Threat Mitigation

20

To scale

12/17/2013

Directed Energy System Concepts for Asteroid Threat Mitigation

21

Comets

• Composed of rock, dusty, ice, and frozen gases
• 100m – 30 km in size
• Very low density
• Very high energy trajectories
• Off ecliptic intercepts needed for long period comets

​

103P/Hartley

12/17/2013

Directed Energy System Concepts for Asteroid Threat Mitigation

22

DE-STAR System Summary

• Originally created by Dr. Philip Lubin from UCSB and Dr. Gary Hughes from Cal Poly
• Different classes (0-4)
• 0: 1 m, 700 W, 0.7 N
• 1: 10 m, 70 kW, 70 N
• 2: 100 m, 7 MW, 7 kN
• 3: 1 km, 0.7 GW, 700 kN
• 4: 10 km, 70 GW, 70 MN

12/17/2013

Directed Energy System Concepts for Asteroid Threat Mitigation

23