End-to-End Mission Design – Trajectory Optimization / Target Selection Criteria

2013 NASA Feasibility Study JPL: Nathan Strange, Tim McElrath, Gregory Lantoine, Damon Landau, Aline Zimmer, Try Lam, Nick Mastrodemos, Paul Chodas, Steve Chesley, Greg WhiffenGRC: Melissa McGuire, Laura Burke, Michael MartiniJSC: Jerry Condon, Juan Senent, Jacob Williams, Ricky JedryMSFC: John DankanichLaRC: Gabe Merrill, Dan Mazanek, Carlos Roithmayr, Haijun Shen, Mark Jesik

2011/2012 KISS Study JPL: Damon Landau, Nathan StrangeGRC: John DankanichARC: Julie BelleroseLaRC: Dan MazanekUSC: Pedro LlanosPlanetary Society: Marco Tantardini

2010 Innovation Fund Study JPL: John Brophy, Bob Gershman, Damon Landau, James Polk, Chris Porter, Don YeomansJSC: Carlton Allen, Willie WilliamsUCSC: Erik Asphaug

Mission Design Teams

Self-Imposed Ground Rules1. Launch by the end of this decade

2. Require only a single Evolved Expendable Launch Vehicle (Atlas family)

– Falcon Heavy and SLS under consideration

3. Use only existing or near-term (by end of decade) technology

40 kW SEP, 10 kW thrusters

4. Total round-trip flight time of ~5 years

5. Select asteroids from the NEA database (no hypothetical objects)

6. Return asteroid a Earth vicinity indefinitely (no crashes, no escapes)

Pre-Decisional -- For Planning and Discussion Purposes Only 2

Mission Timeline

1. Launch (2 Options)

1a. Atlas V – Low Thrust Spiral to Moon

1b. Delta IV Heavy, SLS, Falcon Heavy –Direct Launch to Moon or to Asteroid

2. Lunar Flyby to Escape

5. Lunar Flyby to Capture

3. Low Thrust Trajectory to Asteroid

6. Low Thrust Trajectory to Storage Orbit

7. MPCV Rendezvous

4. Low Thrust Trajectory with Asteroid to Earth-Moon System

(If Needed)Pre-Decisional -- For Planning and Discussion Purposes Only 3

Design for Maximum Return

Pre-Decisional -- For Planning and Discussion Purposes Only 4

2008 HU4 example, return leg onlyNatural approach of 0.15 AU, 1.3 km2/s2

40 kW array, 3000 s Isp, 60 % efficiency

Capture C3, km2/s2

Lunar gravity assist captures NEA during Earth flyby

Storage Options

DV / Propellant

Transfer /Stay Time

Loose orbit,Earth-Moon L1, L2

Station-keeping

few monthsfew weeks

High -LunarOrbit

~30 m/s~ 1.2 t

~ a year ~ a year

DistantRetrograde

~50 m/s~ 2.5 t

couple years many decades

Single flyby captures objects from up to ~3 km2/s2 C3

Double flyby up to ~5 km2/s2, depends on declination

Return an Entire Small Asteroid

Returned Mass, t

Xe, t (no Spiral) Earth Escape

Flight Timeyr (no spiral)

Arrival C3km2/s2

250 5.0a 4/27/2022 4.0 1.8

400 5.2a 4/27/2021 5.0 1.7

600 5.6a 4/27/2020 6.0 1.6

950 8.9b 4/28/2019 7.0 1.6

1300 9.1b 4/28/2018 8.0 1.6

Pre-Decisional -- For Planning and Discussion Purposes Only 5

2008 HU4, ~ 7 m diameter, radar opp. In 2016

Launch 2017, return 1,300 t

Escape: Earth4/28/2018TOF: 0 daysC3: 2.0 km2/s2

Mass: 15 t

Return: Earth4/26/2026TOF: 2920 daysC3: 1.6 km2/s2

Mass: 1306 t

Depart: 2008 HU44/26/2020TOF: 729 daysMass: 1314 t

Arrive: 2008 HU41/24/2020TOF: 635 daysMass: 14 t

Propellant load depends on launch tradesaAtlas 531 launch to LEOAtlas 551 launch to 200 x 11k km alt. orbit Falcon Heavy or SLS launch to escape

bAtlas 551 launch to LEOFalcon Heavy launch to MoonSLS launch to escape

…or Return a Chunk from a Bigger NEA

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DesignationReturned Mass, t

Xe, t (no

Spiral) Earth Escape

Flight Timeyr (no spiral)

Arrival C3

km2/s2

1998 KY26 30 4.9 11/11/2019 4.7 2.0

1998 KY26 70 4.8 7/19/2020 5.3 2.0

1998 KY26 110 5.2 6/25/2020 5.4 4.0

2000 SG344 1800 1.8 3/8/2027 2.6 2.0

2000 SG344 3600 1.7 2/14/2027 2.6 2.1

1998 KY26• ~30 m diameter, C type• Natural intercept ~12 Lunar distances,

C3 = 27 km2/s2

2000 SG344• ~30 m diameter, “Easy” astronaut target• Natural intercept 8–20 Lunar distances,

C3 = 1.3–2.1 km2/s2

Earth0.25 AU

Escape: Earth2/14/2027TOF: 0 daysC3: 2.0 km2/s2

Mass: 7 t

Arrive: 2000 SG3441/5/2028TOF: 325 daysMass: 7 t

Return: Earth9/25/2029TOF: 953 daysC3: 2.1 km2/s2

Mass: 3606 t

Depart: 2000 SG3445/9/2028TOF: 450 daysMass: 3607 t

Example mission returning 3,600 t of a NEA with an Earth-like orbit

Potential Return Opportunities, 2020s• Atlas 551 Launch to

200 x 11k km alt., Launch ~1.5 yr before escape

• 40 kW array• 3000 s Isp, 60 % eff.• 60 days at NEA– 4 d Rendezvous (200 km)– 13 d Characterization– 4 d Bag deployment– 0.5 d Capture– 1.5 d De-spin/de-tumble– 1.5 d Checkout– Double & round up for

margin

Pre-Decisional -- For Planning and Discussion Purposes Only 7

AsteroidAsteroidDiameter

Return C3

Max Return Capability

Earth Escape

Return Date

2007 UN12 4–11 m 2.2 km2/s2 500 t Jun ’17 Sep ’20

2009 BD 5–13 1.7 900 Jun ‘17 Jun ’23

2009 BD 5–13 1.7 500 Jan ‘19 Jun ’23

2010 UE51 5–13 0.9 500 Jun ’18 Nov ’23

2011 MD 6–14 2.1 800 Jun ’18 Jun ’25

2011 MD 6–14 2.1 450 Jan ‘20 Jun ’25

2008 HU4 6–14 1.6 500 Apr ’20 Apr ’26

2013 GH66 6–14 5.3 800 Jan ’23 Apr ’27

2000 SG344 27–65 1.6 1000 Feb ’24 Sep ’28

2006 RH120 3–7 0.3 400 Jul ‘24 Nov ’28

2000 SG344 27–65 2.1 3000 Mar ’27 Sep ‘29

Diameter assumes 5–30 % albedo range

Abbreviated List

Example 2009 BD Trajectory

Spiral 4662 m/s 1.4 yr

To Asteroid 3868 m/s 1.8 yr

Earth Return 152 m/s 3.0 yr

To Storage 60 m/s 1.4 yr

Total DV 8742 m/s

Coast arcs

Thrust arcs

Eclipses

Spiral Trajectory

2 LGAEscape

• Atlas V (551) launch requires spiral trajectory and two Lunar flybys

• This cases launches in early 2017

• 2009 BD return in June 2023– Asteroid in final storage orbit

in Oct. 2024– May be crew accessible as

soon as Feb. 2024

• Direct launch to 2009 BD in June 2018 possible with Falcon Heavy or SLS

• Delta IV Heavy would require escape LGA

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Interplanetary Trajectory

9

Trajectory to Asteroid Asteroid Retrieval

DV = 3868 m/s TOF = 671 days (1.84 yr) DV = 152 m/s TOF = 1092 days (2.99 yr)

Pre-Decisional -- For Planning and Discussion Purposes Only 9

Earth-Moon System Trajectory

Earth-Sun Rotating Frame

Sun

Earth

Moon

15-FEB-2025Lunar flyby (altitude 9300 km)

9-JUN-2023Lunar flyby (altitude 177 km)

Trajectory to Storage Orbit

DV = 35 m/sTOF = 251 days (0.7 yr)thrust arc

EarthFinal DROOct. 2024

15-FEB-2025Lunar flyby Orbit Trim Maneuvers

(for long term stability)

DV = 25 m/sTOF = 257 days (0.7 yr)

Earth-Moon Rotating Frame

(thrust arcs not shown)

127 km)

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Conclusions• It appears feasible to capture and return an entire near-

Earth asteroid using technology that is or can be available in this decade.– Alternative concept is to pick up a ~7-m rock from a much larger

(and well-characterized) asteroid

• A key challenge is the discovery and characterization of a large number of sufficiently small asteroids of the right type and with the right orbital characteristics.

• 6 years, 8 t of propellant, & 40 kW SEP system can return a 500 t asteroid to Earth/Moon capture orbit– Object is captured in Earth orbit following lunar flyby, then

transported to lunar orbit for astronaut mission(s).

• Best time to return asteroid is when it naturally has a close approach to Earth.

• If a NEA retrieval mission is conducted promptly, it could feed experience and hardware forward for a series of human missions beyond low-Earth orbit in the late 2020s.

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