This report outlines the rationale, procedures, technical feasibility, risk assessment, and cost-benefit analysis of utilizing a Near-Earth Object, 101955 Bennu (provisional designation 1999 RQ36 - the target of the OSIRIS-REx mission), as a source of energy to minimize the propulsion requirements of an interplanetary spacecraft. The planet Mars is the target body in this study and the outbound Trans-Mars injection in the years between 2175 and 2199 will be analyzed (within this timeframe Bennu’s orbit is predicted to approach Earth within two Earth radii on at least 80 occasions). The Mars orbit insertion burn, Trans-Earth injection burn, and Earth orbit insertion burn are assumed to be achieved with propulsive maneuvers outlined in standard manned interplanetary mission architectures. To accomplish this mission, two methods of transferring kinetic energy are examined: direct capture and release of the asteroid by a spacecraft using a Kevlar net and an inertial reel, and indirect capture by establishing a station on the asteroid to manufacture compressed material from the carbonaceous regolith in order to fire a mass stream to be captured by the spacecraft. This mission architecture analysis takes into account the associated safety risks of perturbations within Bennu’s orbit (which could result in inaccurate rendezvous location predictions), the implications of altering the orbit of 101955 Bennu after transferring a portion of its energy (since there is a possibility of collision with Earth in the late 22nd century if the asteroid is slowed too significantly), g-limit restrictions of the spacecraft and its occupants during an acceleration by the asteroid, and the possibility of a collision between Bennu and the spacecraft. In addition, the cost-benefit considerations of this mission architecture are weighed. This examination concludes that a direct capture Net and Reel system aboard the spacecraft is not a viable capture method due to an insufficient maximum ΔV available through a best-case perfectly elastic collision (capture) with the asteroid, as well as a prohibitive weight penalty aboard the spacecraft due to the Net and Reel system. However, this report finds that the method of establishing a station on Bennu with the capability to separate mass from the asteroid and fire it at a spacecraft is a plausible (if costly) means of transferring a significant ΔV. A KETNEO-FIMM Asteroid Station mission architecture could also be used in subsequent interplanetary missions providing cost-sharing over many decades for future interplanetary missions.

1. U S A F A
Space
Systems
Research
Center
Kinetic Energy Transfer of Near-Earth Objects for
Interplanetary Manned Missions
C1C Winston Sanks
United States Air Force Academy
Department of Astronautics
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2. U S A F A
Space
Systems
Research
Center
Overview
 Introduction
• Interplanetary Travel
• Energy Requirements
• Transfer Opportunities
 Kinetic Energy Transfer
• Near Earth Object - Bennu
• Procedures
 Future Applications
• Mission Candidates
 Conclusion
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Near-Earth Asteroid 2012 DA14 (Courtesy NASA)

3. U S A F A
Space
Systems
Research
Center
Interplanetary Travel
 Reasons for traveling
• Scientific development
• Resource utilization
• Sustainment of the Human Race on
other celestial bodies
 Terminal Destinations
• Mars
• Moon
• Titan
• Europa
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Jupiter’s sixth closest moon, Europa (Courtesy NASA)

4. U S A F A
Space
Systems
Research
Center
Interplanetary Travel
 Travel Constraints
• Time
• Environmental Control and Life
Support System (ECLSS)
limitations of interplanetary
spacecraft
• Radiation exposure
• Effects of prolonged low-
gravity environment
• Psycho-social impact of
prolonged isolation of crew
• Energy-propulsion
restrictions
• Monetary Support
• Political Consideration
4Unclassified -- Distribution A. Approved for Public Release. Distribution Unlimited.
Wernher Von Braun’s 1948-1952 Mars Expedition plan,
involving 10 spacecraft and seventy astronauts
(Courtesy NASA)

5. U S A F A
Space
Systems
Research
Center
Trans Mars Injection
Energy Requirements
 Energy required for Trans Mars
Injection
• 7.45x1013 - 1.97x1014 Joules
• Roughly equivalent to 8-10
Saturn V Rockets
• Energy required dependent on
trajectory chosen and mass of
the space vehicle(s)
• Values based on NASA Mars
Design Reference Architecture
Mission 5.0
• 250 - 500 metric tons spacecraft
mass
• Bennu’s approximate mean
kinetic energy is 2.3x1019 Joules
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NASA Mars Design Reference Architecture 5.0
Theoretical Manned Spacecraft (Courtesy NASA)

6. U S A F A
Space
Systems
Research
Center
Mars Transfer
Opportunities
 Opposition Class Trajectory
• Short surface stays
• About 40 days
• Best Departure Dates
• 4 September 2017
– ∆V=7588 meters/second
– Bennu approach 0.317 AU
• 12 September 2023
– Outbound Venus Flyby
– ∆V=4400 meters/second
– Bennu approach 0.471 AU
6Unclassified -- Distribution A. Approved for Public Release. Distribution Unlimited.
Opposition - Class Trajectory
Correct phasing occurs every 26 months
(Courtesy NASA)

7. U S A F A
Space
Systems
Research
Center
Mars Transfer
Opportunities
 Conjunction Class Trajectory
• Long surface stays
• Greater than 500 days
• Best Departure Date
• 11 May 2018
– ∆V=3530 meters/second
– Bennu approach 0.35 AU
7Unclassified -- Distribution A. Approved for Public Release. Distribution Unlimited.
Conjunction - Class Trajectory
Correct phasing occurs every 26 months
(Courtesy NASA)

8. U S A F A
Space
Systems
Research
Center
Bennu
 101955 Bennu (1999 RQ36)
• Every six years, Bennu’s orbit
takes it near the Earth
• 2017, 2018, and 2023 are next
close approaches at 0.317 AU,
0.35 AU, and 0.471 AU
• During 2175 to 2199 timeframe,
approaches to within two Earth
radii
• The mean orbital speed of
Bennu is 27.8 km/s
• 480 to 511 m diameter
• Made of carbonaceous material
• Target of upcoming OSIRIS-
REx mission
8Unclassified -- Distribution A. Approved for Public Release. Distribution Unlimited.
(Courtesy NASA)
Orbit of 101955 Bennu (Courtesy NASA)

9. U S A F A
Space
Systems
Research
Center
Kinetic Energy Transfer
9Unclassified -- Distribution A. Approved for Public Release. Distribution Unlimited.
Date Class Relative KE
available from
Bennu (Joules)
∆KE needed
for Transfer
(Joules)
∆V needed
Outbound
(km/s)
Maximum fuel
saved due to
transfer (kg)
4-Sept-2017
Opposition
2.93x1019 1.25x1014
7.49 2.69x106
11-May-2018 Conjunction 1.60x1019 5.53x1013
3.51 1.10x106
12-Sept-2023
Opposition-
Outbound
Venus Flyby 3.19x1019 7.03x1013
4.40 1.34x106

10. U S A F A
Space
Systems
Research
Center
NEO Capture Procedures
Net and Inertial Reel
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Conceptual design of Net and Inertial Reel capture system
(Courtesy Space Junk 3D, LLC)

11. U S A F A
Space
Systems
Research
Center
NEO Capture Procedures
Net and Inertial Reel
11Unclassified -- Distribution A. Approved for Public Release. Distribution Unlimited.
Reel Mass (kg)
Anticipated
Spacecraft Mass (kg)
4.16 x107 5 x105
6.29 x107 5 x105
 The spacecraft mass budget
prohibits a Net-and-Reel
system as a viable capture
method
Date ∆V needed
Outbound
(km/s)
∆V Max Net
and Reel
Capture
(km/s)
∆t Capture
at 10g (s)
Cross
Sectional
Area of
Reel (cm2)
Length of
Reel (km)
Total Net and
Reel System
Mass (kg)
4-Sept-2017 7.49 2.97 30.29 203.25 947 4.16x107
12-Sept-2023 4.40 5.62 44.82 203.25 1433 6.29x107

12. U S A F A
Space
Systems
Research
Center
NEO Capture Procedures
Asteroid Station and Mass Driver
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Conceptual design of Asteroid Station and Mass Driver
(Courtesy Bryan Versteeg / Spacehabs.com)

13. U S A F A
Space
Systems
Research
Center
NEO Capture Procedures
Asteroid Station and Mass Driver
13Unclassified -- Distribution A. Approved for Public Release. Distribution Unlimited.
Conceptual design of Spacecraft Mass Collector (Courtesy NASA)

14. U S A F A
Space
Systems
Research
Center
NEO Capture Procedures
Asteroid Station and Mass Driver
14Unclassified -- Distribution A. Approved for Public Release. Distribution Unlimited.
Date Firing
Velocity
(km/s)
Slug Mass
(kg)
Muzzle
Energy
(Joules)
Total Mass
Transfer
(kg)
Acceleration of
SC per Slug
Capture (m/s2)
Mass of SC
Mass
Collector
(kg)
Number
of
Firings
4-Sept-2017 1.0 64 3.2x107 2.41x105
1.18 1480 3767
11-May-2018 1.0 64 3.2x107 1.91x105 1.99 1261 2976
12-Sept-2023 1.0 64 3.2x107
1.25x105 2.26 952 1947

15. U S A F A
Space
Systems
Research
Center
NEO Capture Procedures
Asteroid Station and Mass Driver
15Unclassified -- Distribution A. Approved for Public Release. Distribution Unlimited.
 Reasonable method of
momentum exchange
• Mass Transfer differences are
dependent on required
transfer ∆V and relative
velocities of Earth and Bennu
at the time of transfer
Departure
Date
Asteroid Station
Mass (kg)
Total Mass
Transfer (kg)
4-Sep-17 2.02 x106 2.41 x105
11-May-18 2.02 x106 1.91 x105
12-Sep-23 2.02 x106 1.25x105

16. U S A F A
Space
Systems
Research
Center
Safety
16Unclassified -- Distribution A. Approved for Public Release. Distribution Unlimited.
 Safety is a priority
• Perturbation risk within Bennu’s
orbit
• Could result in inaccurate
rendezvous location predictions
• Possibility of collision with the
spacecraft
• In late 22nd century Bennu’s orbit
becomes a potential hazard to Earth
• Possibility of collision with Earth
• G-limit restrictions of the spacecraft
and its occupants during an
acceleration by the asteroid
NASA Mars Theoretical Positron Reactor Powered
Spacecraft (Courtesy NASA)

17. U S A F A
Space
Systems
Research
Center
Safety
17Unclassified -- Distribution A. Approved for Public Release. Distribution Unlimited.
 Perturbation risk within Bennu’s
orbit
• Bennu has a well-determined orbit
due primarily to 12 years of radar
ranging
• Accuracy of the orbit determined for
Bennu will increase dramatically by
the planned departure dates in the
late 22nd century
 In late 22nd century Bennu’s orbit
becomes a potential hazard to
Earth
• Study found that transfer with one
500,000kg spacecraft would not
cause a collision that wasn’t going
to happen otherwise.
 G-limit restrictions of the
spacecraft and its occupants
during an acceleration by the
asteroid
• The maximum spacecraft
acceleration is limited to 10g
• Ensured in the Net and Inertial
Reel architecture through the
inertial reel itself
• In the Mass Driver
architecture, each 64kg slug
capture by the spacecraft
contributes a maximum
acceleration of roughly 2 m/s

18. U S A F A
Space
Systems
Research
Center
Future Candidates
 (285263) 1998 QE2
• Binary asteroid system (primary
body has a moonlet)
• Orbital period of 3.77 years
• Diameter calculated at 2.75
kilometers
• The next notable close approach
predicted May 27, 2221, the
asteroid will pass Earth at
0.038 AU
18Unclassified -- Distribution A. Approved for Public Release. Distribution Unlimited.
(Courtesy NASA)

19. U S A F A
Space
Systems
Research
Center
Conclusion
19Unclassified -- Distribution A. Approved for Public Release. Distribution Unlimited.
 Introduction
• Interplanetary Travel
• Energy Requirements
• Transfer Opportunities
 Kinetic Energy Transfer
• Near Earth Object - Bennu
• Procedures
 Future Applications
• Mission Candidates
 Conclusion

20. U S A F A
Space
Systems
Research
Center
Acknowledgements
20Unclassified -- Distribution A. Approved for Public Release. Distribution Unlimited.

21. U S A F A
Space
Systems
Research
Center
Questions?
21
Unclassified -- Distribution A.
Approved for Public Release.
Distribution Unlimited