Asteroid Initiative Idea Synthesis Workshop Asteroid Deflection Session

1. Asteroid Initiative Idea Synthesis Workshop Asteroid Deflection Session 25 September 2013 Affordable Spacecraft with Capabilities to Enable Multiple Deflection Schemes Prepared by: Andrew E. Turner Turner.Andrew@ssd.loral.com 3825 Fabian WayPalo Alto, CA 94303.4604USA

2. Four Diverse Asteroid Deflection Techniques • Gentle sustained push applied directly by the Asteroid Redirect Vehicle (ARV) via its robotic arms against a selected site on the asteroid, or against a robotically deployed fixture that distributes the push pressure over a wider area on the asteroid to demonstrate direct asteroid deflection • Electrostatic tractor technique using the technology developed at the University of Colorado • Gravity Tractor technique defined by the B612 Foundation also defined by NASA Ames Research Center (ARC). which we have augmented to include a robotically extracted boulder as a gravity multiplier • Kinetic impactors developed by ARC • These 4 techniques are applied when appropriate to the asteroid target, whose nature may not be known until it is approached. It may not be possible to select which type of asteroid is to be manipulated, but we have a flexible spacecraft system design that can handle any type • More than one of these techniques may be applied during a single mission • So the “person in the street” understands the importance of this project, we would demonstrate the capability to • Move an asteroid large enough to constitute a threat to show we can “save the planet” • Retrieve a boulder to distant Earth orbit so a sample can be brought home by U.S. astronauts that people can touch

3. Spacecraft Configuration • The versatile flight-proven, economical SSL bus can accommodate the specialized equipment for this mission, which has been commercially procured on a Firm Fixed Price basis more than 80 times (~5 launches/year) • Proposed equipment has sufficiently diverse functionality that it can handle any of the 4 deflection techniques • It will be discussed how even a single deflection technique involves multiple equipment types • 40 kW of electric propulsion is sufficient to generate 2N of thrust using thrusters already available from SSL, can adapt new thrusters if needed

4. SSL Has Full Access to MDA’s Robotics Technology • The robotics proposed for this mission already exist and reuse hardware and control software from the ISS robotics, Orbital Express Autonomous Satellite Capture Demonstration and the DARPA Phoenix Satellite Repurposing Demonstration SSRMS captures HTV at ISS IDD engages the Martian surface 13-m Hubble Telescope Capture Arm with Visual Servo Algorithms to Capture Free Flyers (available for this mission) This equipment now located at NASA-GSFC MSL Robotic Arm, Multi-Tool Turret

5. Asteroid Deflection/Retrieval Gravity Tractor Example • Propellant Budget accounting borrowed from heritage spacecraft mission analysis for this application • Masses of acquired 6-m boulder also 200-m diameter asteroid counted as spacecraft mass • Propulsion: 8 SPT-140 with total 2N thrust, bi-propellant with total 80N thrust • About 7% of total impulse applied to the 1 mm/s delta-V Deflection, this operation requires about 2 months 160-ton boulder acquired

6. Background to Example • Gravitational attraction between the 10-ton spacecraft and the 200-m asteroid is below 2N without the 160-ton boulder • Gravitational attraction is 7N at the asteroid’s surface when the 160-ton boulder is acquired so employ chemical thrusters • At 90m altitude the gravitational attraction is 2N which can be balanced by the electric thrusters. The asteroid subtends a total angle of about 90 deg. as seen from the spacecraft. This assists with avoidance of the asteroid’s shadow for full solar array power and avoidance of impingement of the thruster plumes on the asteroid’s surface • What if the asteroid is not a “rubble pile” but a coherent asteroid and we cannot extract a boulder? We might push • What if the asteroid is a “rubble pile” but contains only rubble far smaller than 6m (160 ton) boulders? We might scoop • What if 90 m is too close to the asteroid for continuous operation? We might reduce thrust, operate from a greater distance and spend more time but not more propellant performing the deflection demonstration 1 2 3 Asteroid is spherical with a density of 1500 kg per cubic meter 3 2

7. Hip Pocket Slides

8. Background: Coherent, Fractured, or “Rubble Pile” Asteroids • Example of a “rubble pile”: Asteroid Itokawa, hundreds of meters across, from which Japanese spacecraft Hayabusa returned samples in 2010 from a 2005 visit • Small asteroids, only a few meters across, may tend to be coherent boulders • A coherent asteroid is more amenable to being pushed or acquired for captive-carry, a “rubble pile” is more amenable to being pulled using the gravity tractor, once a coherent boulder has been acquired from its surface Source: What We Have Learned from the Asteroid Itokawa Samples Returned by the Hayabusa-1 Mission’, The 10th IAA International Conference on Low-Cost Planetary Missions 18 June 2013

9. The Path to the Asteroid, and The Way Back, via The Moon Barycentric Orbits Spacecraft Launch Mass • New generation of commercial LVs: 10-15 tons into trans-lunar trajectories • A lunar gravity assist (LGA) is used to eject the spacecraft into interplanetary space with nearly enough impetus to reach Near-Earth Asteroids • An LGA can provide a delta-V on the order of 1 km/s • Later maneuvers using electric propulsion speed the spacecraft on its way • This avoids spending considerable time in the Van Allen belts near the Earth, thus minimizing radiation exposure Apogee at Lunar Altitude • A lunar gravity assist (LGA) is essential for bringing home the 160-ton boulder • Even with electric propulsion spacecraft has insufficient total impulse to achieve capture with this heavy mass • Lunar gravity acts on every atom within the spacecraft and the boulder, so there is no stress created as it operates • The spacecraft carrying the boulder is constrained not to be significantly nearer to Earth than the moon

10. A Second (Much Smaller) Moon … • YouTube video http://www.youtube.com/watch?v=3KG3kHWLSZo supplied by the Keck Institute for Space Studies displays injecting the captured asteroid into a distant retrograde lunar orbit following a low perigee pass by Earth • An alternative strategy would be to use an LGA only and inject into an orbit of roughly the same size and the same period as the orbit of the moon • This orbit would be inclined to the lunar orbit with a wedge angle of about 50°, but both orbits could be inclined about 23° to Earth’s equator, therefore captured asteroid is reachable from a Cape Canaveral launch • The asteroid would be maintained on the opposite side of its orbit from the moon to limit perturbations due to lunar gravity, corresponding to a halo orbit about the Earth-moon L3 point, precise location to be evaluated • The boulder is now ready for astronauts to visit, study it and return samples North Lunar orbit Retrieved Boulder orbit Wedge angle