astrodynamics technologies€¦ · astrodynamics technologies opag workshop feb 21,2018 ryan p....
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Astrodynamics Technologies
OPAG workshopFeb 21,2018
Ryan P. RussellThe University of Texas at Austin
OPAG workshopFeb 23,2018
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Agenda• Introductions• Astrodynamics for Outer Planets
- Overview- Specifics to OPAG- Enabling successful past/current missions- Enabling/improving future missions- Recommendations: (consider treating Astrodynamics as
a “push technology” rather than “pull”)
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Who is the Astrodynamics Community?
• I am attempting to represent a large community of researchers and practitioners
• NASA centers, FFRDCs, Universities, international space agencies
• Professional Societies- American Astronautically Society (AAS)
• Astrodynamics Specialist Meeting• Spaceflight Mechanics Meeting
- American Institute of Aeronautics and Astronautics (AIAA)• Astrodynamics Technical Committee (chair elect)• GNC Technical Communities
- International Symposium on Space Flight Dynamics (ISSFD)
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Astrodynamics Defined…
• The study and application of the dynamics of spacecraft and celestial bodies
• Synonyms: celestial mechanics, orbit mechanics, and spaceflight mechanics
• Astrodynamics is an applied, cross-cutting discipline that includes - mathematics - optimization theory - estimation theory - statistics and probability - environment modeling- numerical/data analysis- computational engineering
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Domains of Astrodynamics• Earth focused
- Military (assets, technologies to support DoD, GPS, space catalogue, space situational awareness)
- Commercial (design, launch, track commercial satellites, GEO/LEO)
- Science/Exploration (ISS, Earth remote sensing, weather etc.)
• Beyond Earth (~Science/Exploration)- Moon, cis-lunar- Inner planets- Small bodies (comets/asteroids)- Outer planets
(and planetary moon systems)
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Outer Planets Astrodynamics
• Mission Destinations…- Gas Giant systems
• Jupiter• Saturn• Uranus• Neptune
- Kuiper belt bodies- Icy moons
• Titan/Enceladus• Europa/Ganymede/Callisto
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Roles of Astrodynamics• Mission design
- Concept feasibility/early mission development- Proposal reference trajectory- Extended missions designs- Trajectory optimization/Path planning
• Flight operations/Technologies- Modeling/simulation- Tracking/Orbit determination- Automated maneuver planning - GNC (Guidance, Navigation, Control)
• Estimation theory• Autonomy/Robotics (e.g. OpNav, precision landing)
• Science recovery- Orbit determination (plus sought after parameters)- Remote sensing/Data analysis/Signal processing
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Outer Planet Astrodynamics
• “It’s a solved problem” - doesn’t apply here…
• Outer planet missions are among the hardest missions to design
• Extraordinarily large design space• Difficult constraints
- Radiation- Lighting- Timing/Long seasons
• Strong non-Keplerian dynamics- third body- non-spherical gravity- Tether applications
• Outer planet missions stand to benefit the most from improved Astrodynamics methods/software
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Success Stories• Voyager grand tour, Galileo tour, Cassini
- Mid-mission, development of new tour design tool (MTOUR), enabled extended missions, grand finale
• Celestial Mechanics & Dynamical Systems->Third body dynamics missions: Genesis, Spitzer, ICE, Lunar missions
• Dawn: low-thrust optimization software Mystic enabled its success (and lifeline preventing it from being canceled). Hayabusa another example
• Cassini• Europa Clipper/Europa Lander/Juice• Jupiter System Grand Tour (weak capture at all 4 Icy
moons for no ∆v)• MOSTLY EXECUTED AS “PULL TECHNOLOGY”
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Outer Planet Astrodynamics
OBJECTIVE:
Mission Science Return
Mission Co
st ($
)
Conventionalmethods
State of the artmethods To be
discovered methods?
Maximize Science →Minimize Cost ↓
Flagship Class…
New Frontiers…
Discovery…
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Exploring the Design Space
• Each dot is a point design• Single dots can be massive effort (say team of
engineers, working for weeks)• Need new automated methods to search full space
Metric 1
Metric
2
Notional Design Spacewith 3 Performance Indices
radiation
want to minimize both objectives
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Typical Mission Study/Proposal
• Rushed timeline, limited budget• Most elements of spacecraft system
require/hinge on a credible reference trajectory
• Basic mission design (necessarily) fixed at an early stage
• Common Result:- Best feasible point design is
chosen/fixed- design space not fully explored- Point of no return reached…
• With competition for discovery/new frontier proposals, the stakes are high
Reference trajectory
Science requirements
Spacecraft Systems Design
Iterative Design Cycle
Astrodynamics Tools
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Astrodynamics Focus Areas (next decade)
• Multibody dynamics research- Orbit stability - Highly non-spherical gravity fields - Ballistic Capture- Planetary moon tours / Resonance hopping
• Numerical methods- Analytical solutions/Fast proxy models- High performance computing- Monte Carlos, high fidelity sims, long-term orbit prediction, body ephemerides- Planetary protection simulations,
• Optimization Theory- Global optimization- Combinatorial optimization- Low thrust optimization - Optimization of tethered/sail/non-propellant propulsion
• Small Satellite missions (i.e. low budget, low res sensors etc)• GNC technologies
- Aero braking/ EDL technologies (e.g. Titan) - Precision terrain relative navigation (e.g. Europa, Enceladus)- Autonomy/ AutoNav/ Optical navigation- Advanced Estimation Techniques- Autonomous approach, orbit insertion, and tour execution
vetted to zeroth order by many in the community
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Suggestion forward• Maximize the impact of mission studies by investing in precursor
astrodynamics research programs (“Give it a Shot!”…)• Tap into the large community of Astrodynamicists
- NASA, FFRDCs, non-profits, universities, international • Open up competitive opportunities for solution methods (before mission
studies, lower TRL)• Solicit “push technologies” rather than “pull”• Help remove the stovepipes
- More opportunities for collaborations- Centers of Excellence, MURIs, etc.- Encourage cross-center collaborations
• Similar model to Science (competitions, annual mechanisms to propose new ideas etc)
• Advocate for astrodynamics language (specific to mission destinations) in steering documents, NASA HQ technology calls
• Low investment (mainly software/simulations) potential high payoff
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Example Technologies
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Low-Thrust Trajectory Design
• Why consider low-thrust systems ?- More efficient propulsion (high Isp, no fuel with solar sail)- Larger payload ratio (smaller launch vehicle)- Cheaper- Flexible mission design with extended launch windows
Deep Space 1Mission: Testing / FlybyBodies: Comet BorrellyIsp: 3100 s
1998‐2001
SMART‐1Mission: OrbiterBodies: MoonIsp: 1640 s
2003‐2006
HayabusaMission: Sample ReturnBodies: ItokawaIsp: 2900 s
2003‐2010
DawnMission: Flyby / OrbiterBodies: Mars‐Vesta‐CeresIsp: 3100 s
2007‐2015
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Challenges of Low-Thrust• HUGE design space• Highly non-linear
Multi-body problems
Long thrusting periods
Multiple local
minima
Multi-revolution problems
Constraints
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Low Energy Third-Body Dynamics
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~Ballistic Capture
Quasi‐ballistic captureLoosely orbit for “free”
Primary
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Multiple Flyby Trajectories
Titan Enceladus Cycler
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Long Life Periodic Science OrbitsEnceladus Vesta
Europa
Ganymede
Phobos
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• Applications- Planetary protection- Collision probability- Navigation Monte
Carlos- Uncertainty
Quantification
• Fast proxy model• Make a non-Gaussian
distribution using a sum of Gaussians
• Split the distribution in multiple dimensions
Full distributionApproximate distribution
Gaussian Mixture Models
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Fast Gravity Models
Mj
rjrcm
Point mascon model Interpolation model
Multi‐core models
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Analytic Models (e.g. low-thrust, oblate planets, three-body)
• Orbit averaging• Perturbation theory• Choice of independent variables, coordinates
matter• Speed allows massive, rapid searches • New/improved methods
- Vinti model: Oblate bodies (large J2 like Earth all the gas giants)
- Control models (analytic low thrust models)- Series solutions (modern taylor series,
others) - STARK MODEL (from physics –charged
particles in homogeneous e field)
tNtN-1t2t1t0
u0uN-1
u1xN
xN-1
x2
x1
x0
Numerical propagation: SLOW
Analytic Models: FAST
Analytic propagation of Saturn insertion
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Auto/Optical Navigation at Small bodies
• Autonomous• On‐board• Filtering
(EKF/UKF/DDF)• Approach/
Descent• Pinpoint landing
S.L.A.M.(simultaneous localization and mapping)• Body Spin State• S/C position• S/C attitude
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BACKUPS
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Introductions…My Research Interests
• Trajectory optimization• Multi-body dynamics• Perturbation methods• Numerical methods/ HPC• Planetary moon missions• Gravity modeling• Optimal control• Space Situational Awareness• Navigation/ Proximity Operations