Modular Assembly: An Efficient Approach for Creation and Maintenance of Persistent Space Assets William (Bill) R. Doggett Structural Mechanics and Concepts Branch NASA Langley Research Center, Hampton, Va. 23681 USA 2019 IEEE International Conference on Robotics and Automation
Outline • Definition of Persistent Asset and Motivation • Persistent Asset: Benefits • Past Assembly History and Why is Assembly Viable Now • Design for Persistence Applied to Applications • Large Precision Reflector • Persistent Platform: Solar Electric Transfer Vehicle • Langley Research Center (LaRC) Technology Development Efforts • Concluding Remarks 2
Definition and Motivation Persistent Asset: Any space system that benefits from multiple visits. Problem: Single launch paradigm is unsustainable. • Inability to repair and upgrade results in: • conservatism: on-orbit technology is decades behind state of the art, and • increased cost and complexity: redundant systems with elaborate deployment. • Single launch limits performance due to mass and volume constraints 19.1 m 17 m Why Now? New Paradigm for “Persistent 12 m Assets” enabled by: • Multiple, frequent, and inexpensive commercial launch options. • In-space robotic capabilities integrated with commercial spacecraft providing Multiple Low Cost Launch Options: Dia. ~ 5 m frequent, inexpensive visits. Need: New cross-cutting modular • Advances in electronics, approach supporting a new Persistent computational architectures, and Asset operational paradigm. software systems. 3
Significant Benefits of Persistent Asset Paradigm • Pay as you go: Put initial capability in place and expand/evolve capability over time. Provides a rapid return on investment. • Increased capability or reduced life cycle costs through ability to: • Upgrade: replace key competitive subsystems leaving “utilities” in place • Expand and Reconfigure: to rapidly adjust to customer needs • Service: reducing the need for high reliability of the entire system • Increased Competition: well defined interfaces allow variety of commercial companies to provide solutions • Significantly increased design freedom because: • Minimum mass will no longer be the primary driver and increases to system mass can be traded to reduce: • mission cost (design, development, and fabrication), • mission risk (increased structural margins, carry spares) • test and validation time • Launch volume and payload shroud dimensions are no longer primary drivers because the system can be economically distributed among a variety of vehicles • More efficient launch packaging schemes can be used that minimize the impact of launch loads. • The total spacecraft can thus be designed and optimized for in-service (zero-g) loads as opposed to launch loads which are the current primary driver. 4
What is Different from Past Assembly Approaches? 1988 • Early work focused on structure, not system 1985 1985 Space Station Freedom Maintenance and Repair 1992 • Space Station relied heavily on astronaut support 2015 LEO EVA International Space Station Assembly (1998-2011) and Servicing(1998-) 5
Robotic Approaches are Viable for Assembly and Servicing 1995 Automated Structures Assembly Laboratory Northrop Grumman MEV DARPA/Space NASA Custom Tools Systems Loral Restore L RSGS Feedback from Environment • Supervised Robotics are viable for space operations 2008 • Multiple robotic vehicles and providers entering market • Increasing need for cost effective rapid refresh of systems • Telecommunications • Space and Earth Science • Space Exploration Persistent Asset New Operational Paradigm Needed Paradigm 6 Japanese Kibo module positioned
Persistent Asset Application: Large Precision Reflector • Astrophysics and space science community desires > 20-meter diameter aperture for next space telescope. • Persistent asset paradigm currently being applied to overcome single-launch limitations. • Telescope structural modules and connectors currently being developed at LaRC. Vaughan 1981 Thronson 2014 Hedgepeth 1984 7
LaRC Technology Development: Tri-Truss Modular Architecture Top Close Out Mirror Members Structural Member (1 of 3) Core Central Triangle Bottom Members Tri-Truss significant features Tri Truss Module • No repeated members at interfaces • Statically Determinate Structure • Packages efficiently • Statically Stable Structure through Ortho-View deployment • High performance Assembled Structure Side View • Variety of locations to attach operational Packaged Deployed sub-systems 8
LaRC Technology Development: Modular Telescope Metallic Connection for Assembly Tests Multi-Nut Captive Bolt 2-meter Prototype Hardware 9
Persistent Asset Application: Persistent Platform Group Solar Electric Propulsion Tug Geo Platform Fuel/Servicing Depot DARPA GEO Platform Key Interfaces: Module: Backbone Truss Component: Instrument Earth Science Station 10
Test Platform Packaged for Launch Connection Deployed for clarity + Prepared for Assembled and Deployed assembly Pla lay V Vid ideo https://youtu.be/FK8gD5PY-Ng 11
Large-Scale Zero-G Application (1): Persistent Platform Solar Electric Transport Vehicle (SETV) • SETV conceived as having a modular system architecture. • Modular architecture allows for SETV to expand capability over time enabling increased payload capability, reduced trip time and negates solar array efficiency limitations. • Modules developed have broad applicability to other systems such as: • Science platforms, • Power beaming platforms, • Communications platforms. • Structural modules and modular connectors being developed at LaRC 12
LaRC Technology Development: Persistent Platform Long Reach Solar Tug Manipulator Module Precision Positioner Keel Truss Structure Assembly Direction Existing New Joint Response Spacecraft Module 2-meter Non-Structural Prototype Calibration Block Supports Hardware (Removable) Capture Alignment Guide Spring Pins 13 (Removable)
Concluding Remarks • Space operations are on the cusp of a revolutionary new operational paradigm that is enabled by new space robotic capabilities and frequent, low-cost launch opportunities. • Key attributes and benefits of a new “Persistent Asset” operational paradigm that leverages these new capabilities has been introduced. • Application of the Persistent Asset Paradigm to two relevant space systems were described. • The active development of modular technology at LaRC supporting implementation of Persistent Assets was summarized. Adoption and application of the Persistent Asset Paradigm can begin immediately 14
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Historical In-Space Assembly: Unique Packaging Opportunities Erectable Structures: Space trusses are comprised of strut members connected at nodes • Efficient packaging • Structurally simple and predictable 36 struts 12 node clusters 1976 36 Strut Members Node and Space Shuttle Connecting Joints 16 (54 m, [184 ft])
Predictability Key to Acceptance • Truss structure surface accuracy of 50-100 microns (~0.002-0.004”) • Center-fed parabolic reflector design with 3 fold symmetry • Primary support truss 45 nodes 150 graphite epoxy struts 1995 • Aprior Predictions • No tuning 4m-Diameter MAC (modal assurance criteria, 1 = perfect match
Historical In-Space Assembly: Robotic Assembly Background: Past Assembly Projects (Agent: Robot) Objective: Reliable predictable precision assembly of multiple structural forms from common components. 1995 Strut Installation Tool 8m [26 feet] diameter Panel Installation Tool 20m [66 feet] linear beam
Panel Utilities – Mixed Modules with Power Strip 4 4 4 Utilities at the corners and sides 4 4 Moveable power strip 4 4 4 4
Videos of Referenced Work RAMSES video https://youtu.be/FK8gD5PY-Ng Automated Structures Assembly Lab (ASAL) https://www.youtube.com/watch?v=h6-U_XINL8k&feature=youtu.be Precision Trusses https://www.youtube.com/watch?v=SBvOv5zJvJ4&feature=youtu.be Telerobotic Advances https://www.youtube.com/watch?v=4oS2BANNAlM&feature=youtu.be
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