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Mission Analysis and Conceptual Spacecraft Design for Human Exploration of Near-Earth Asteroids

Mission Analysis and Conceptual Spacecraft Design for Human Exploration of Near-Earth Asteroids. Aline K. Zimmer Institute of Space Systems University of Stuttgart 17 October 2012. Overview. Introduction Mission Analysis Accessibility Mission Abort Reusability System Analysis

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Mission Analysis and Conceptual Spacecraft Design for Human Exploration of Near-Earth Asteroids

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  1. Mission Analysis and Conceptual Spacecraft Design for Human Exploration of Near-Earth Asteroids Aline K. Zimmer Institute of Space Systems University of Stuttgart 17 October 2012

  2. Overview • Introduction • Mission Analysis • Accessibility • Mission Abort • Reusability • System Analysis • COSMICS & MPDB • Conceptual Spacecraft Design • Conclusion & Outlook

  3. Introduction to Near-Earth Asteroids • Near-Earth Asteroids (NEAs) • Maximum perihelion distance of 1.3 AU • Wide range of characteristics • 7,812 NEAs discovered (16 March 2011) • Potentially Hazardous Asteroids (PHAs) • Subgroup of NEAs • Threatening close approach with Earth (< 0.05 AU) • Size large enough for devastation in case of impact (absolute magnitude H < 22.0) • 1,224 NEAs classified as PHAs (16 March 2011)

  4. Why Missions to NEAs? • Science • Pristine material • Understanding of the origin and formation of the solar system • Characterization of NEA population • Sample return! • Technology • Test bed for long-duration, deep- space capabilities • Radiation shielding • Close-loop life support systems • Technology to cope with psychological and physiological effects on humans • In-situ resource utilization

  5. Why Missions to NEAs? • Exploration • Extension of human frontier beyond Earth-Moon system • Stepping stones on the way to Mars • Proximity to Earth & low mass  increased accessibility • Human contributions • Mission autonomy & real-time response (communication delays) • Cognitive & intuitive capabilities • Flexibility & adaptability • Informed decisions regarding sample selection & placement of scientific equipment

  6. Objectives Feasibility of small-body missions for human exploratory and scientific endeavors • Comprehensive understanding of the nature of human missions to NEAs • Number of accessible targets • Range of mission durations • Novel mission architectures to reduce cost and risk • System Design • Development of a computer tool in support of the systems engineering process • Example spacecraft concept • Configuration, subsystems, concept of operations

  7. Overview • Introduction • Mission Analysis • Accessibility • Mission Abort • Reusability • System Analysis • COSMICS & MPDB • Conceptual Spacecraft Design • Conclusion & Outlook

  8. Accessibility Model Objective • Pre-selection of asteroids Approach • Based on astrodynamics rather than scientific gain of mission target • Loose filters for upper and lower limits of orbital elements based on upper stage performance Trajectory Design • Departure from LEO, two-impulse transfer, round-trip mission • Targets: “theoretical” NEAs for combinations of orbital elements within limits • Termination condition: Δv < 10 km/s, mission duration < 365 days

  9. Accessibility Model • Termination condition: Δv < 10 km/s, mission duration < 365 days

  10. Semi-major axis: Eccentricity: Inclination: Verification of Model 7,812 currently known NEAs Size Criterion • absolute magnitude H≤ 25 • sufficient size for proximity interaction and relatively slow rotation rate 6,704 Orbital Elements Criterion 2,567 Termination Conditions • Δv < 10 km/s • mission duration < 365 days 240 NEAs accessible between 2020 and 2040

  11. Verification of Model • Confirmation of model by 240 accessible asteroids

  12. 2004 MN4 2001 FR85 2009 UY19 2007 UY1 2010 JK1 2000 SG344 2000 SG344 1999 AO10 (2000 SG344) Mission Opportunities • 170 launch periods between 2020 and 2040 • Strategy • Gradual increase in mission duration • Increase in time spent in proximity • ~1 mission / 2 years

  13. NEA Mission Campaign

  14. Example Trajectory • Earth, asteroid, & spacecraft orbit Sun together • Small angular distance, no conjunctions • “Small” distances between spacecraft and Earth

  15. Mission Abort Anytime Abort “Free” Return critical incidents threatening crew, e.g., injury, illness, life support system malfunction Cause critical incidents concerning propulsion system, e.g., engine failure, fuel tank leak duration of return to Earth (minimized) Δv (minimized) Driving Parameter Δv duration of return to Earth Secondary Parameter

  16. Mission Abort “Free” Return ~365 day return feasible for all missions; Additional ~180 day return for some missions Anytime Abort Feasible for some missions

  17. Mission Architecture without Reusability Crew & cargo departure from Earth Earth’s Sphere of Influence v∞ Rendezvous with NEA Cargo discarded Direct re-entry of crew Staging orbit v∞ Transfer to NEA

  18. Spacecraft Architecture Human Missions to NEAs • High cost per mission for multiple missions • Reusability of system elements throughout campaign desirable • Stationing system elements in space between missions • High mass • Complex system • Multiple launches per mission • High manufacturing cost • Multiple missions • All system elements expended after each mission

  19. Mission Architecture with Reusability Earth’s Sphere of Influence Cargo parking location v∞ Rendezvous with NEA Crew departure from Earth Direct re-entry of crew Staging orbit v∞ Crew & cargo rendezvous, transfer to NEA

  20. Libration Points in Earth’s Vicinity EML4 EML2 • Sun-Earth Libration (SEL) points time-invariant in rotating heliocentric frame  No additional phasing restrictions • High energy level  Beneficial gateways for interplanetary missions EML1 SEL1 SEL2 150 Mio. km EML5 EML3 1.5 Mio. km 1.5 Mio. km Sun EML1 EML2 NEA SEL2 EML3 SEL1 Sun

  21. Proposed Mission Architecture • Architecture: Cargo s • Outbound & inbound transfers to NEAs • Halo departure / arrival on unstable / stable manifold • Maneuver in direction of motion at perigee • Maneuver at SOI to match v∞ vector  heliocentric trajectory of crew vehicle • Architecture: Cargo stationed in SEL point halo orbits SOI Δv SEL2 v∞ Δv Δv v∞ Δv

  22. Results • Total Δv range from “free” transfers to hundreds of m/s • Heliocentric specific energy • Heliocentric inclination • Perigee altitude of the manifold trajectory

  23. Example Trajectories • First mission to asteroid 2000 SG344, outbound leg, first SOI exit

  24. Example Trajectories • First mission to asteroid 2000 SG344, outbound leg, second SOI exit

  25. Overview • Introduction • Mission Analysis • Accessibility • Mission Abort • Reusability • System Analysis • COSMICS & MPDB • Conceptual Spacecraft Design • Conclusion & Outlook

  26. The Conceptual Design Problem • Fuzzy problem formulation • Strong interdependencies among system elements • Adverse relationship between available information and consequences of conceptual design decisions • Multidisciplinary approach • Clear methodology (simple steps) • Iterations • Adapted computer tools to support simulation and analysis

  27. Space Station Design Workshop (SSDW) • Conceptual design and optimization studies of space stations and human exploration missions • Within a short time frame (usually one week) • Multidisciplinary design teams • Customized, interdisciplinary methodology • Sophisticated easy-to-use computer tools • Realistic education in systems engineering • Hands-on experience for students and young professionals • Competitive, international, interdisciplinary team challenge

  28. Functional Requirements • Concurrent System and Mission Conceptualization Software (COSMICS)

  29. Mission Parameter Database (MPDB) • Data structure & interdependencies

  30. Conceptual Database Modeling • Entity Relationship Model (ERM): definition of relationships between entities • For users: predetermined design space • For admin: easily adaptable • Translation into the Relational Database Model (RDBM) for the use with MySQL

  31. Web-Application Architecture

  32. Results • Several test runs • Real-time data exchange • Large amounts of data • Coherent data set • Multitude of users • Portability & license-free software • Tested on all established operating systems and web-browsers • Flexibility • Design space easily adaptable • Successful application during SSDW in 2009 & 2010 • Interest from ESA & EADS Astrium in purchasing the software for their concurrent design facilities, current negotiations

  33. Conceptual Spacecraft Design • Crew of 3 & mission duration of 365 days (“free” return) • Crew Transfer Vehicle (CTV) • MPCV-derived capsule: crew transport • Service module: cargo & supply • Mission duration of 65 days (anytime abort) • 17.4m3 habitable volume • 20 tons • Deep-Space Habitat (DSH) • Long-duration amenities • Suitports for dust mitigation • 28.3m3 habitable volume • 17 tons

  34. ConOps: Baseline

  35. ConOps: Reusability #1 full at AOI 2nd maneuver 1st maneuver

  36. ConOps: Reusability #2 half full at AOI 1st maneuver 2nd maneuver

  37. ConOps Trade Off • Pay off for low interplanetary inclinations and C3 • Reusability #1 • Mass penalties for most missions • Requirements given by combination of missions • Reusability #2 • Mass savings of more than 40 tons • DSH PM fuel mass already used • Requirements only given by single mission

  38. Overview • Introduction • Mission Analysis • Accessibility • Mission Abort • Reusability • System Analysis • COSMICS & MPDB • Conceptual Spacecraft Design • Conclusion & Outlook

  39. Conclusion & Outlook • Accessibility & target selection • Determination of filters for pre-selection of asteroids • Identification of 73 promising targets • Mission abort • Confirmation of two abort scenarios: “free” return & anytime abort • Transfer trajectories can be optimized for better abort options • Reusability architecture • Connection of halo orbits at SEL points and their manifolds to interplanetary trajectories of human trajectories • Total Δv from “free” transfers to several hundreds of m/s • Transfer trajectories can be optimized for better reusability options • Additional target asteroids, Mars and its moons

  40. Conclusion & Outlook • COSMICS & MPDB • Multi-user top-level systems engineering tool • Integration of all subsystems and their interdependencies • Mapping of design process and maturity • Facilitation of documentation and communication  Intuitive and efficient use, greatly accelerating iteration and design progress • Capabilities not limited to conceptual design of space missions and systems; adaptation of database • Implementation of several missions or entire campaigns • Design space modifiable for users (not only admin) • Use over internet

  41. Conclusion & Outlook • Space craft design & architecture trade-off • Crew Transfer Vehicle: 17 tons, MPCV heritage • Long-duration Deep-Space Habitat: 20 tons • Propulsion system: IMLEO between 90 and 400 tons • Future work: increased level of detail, subsystem optimization, synergies • IMLEO savings of more than 40 tons • Evaluation on case-by-case basis • Cost & risk analysis

  42. Thank you! Contact: Aline K. Zimmer Institute of Space Systems University of Stuttgart Pfaffenwaldring 29 70569 Stuttgart Germany zimmer@irs.uni-stuttgart.de

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