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Assembly and Outfitting of Tall Truss-Based Power Towers

Description:

ScopeTitle:

Extraterrestrial Surface Assembly ofTall Truss-Based Towers

ScopeDescription:

Autonomous assembly of truss-based structures is oneof the leading candidates for establishing some of the early lunarinfrastructure, for example, tall towers (50- to 80-m total height) forsolar power generation and communications, blast containment shields forlaunch and landing pads, shelters, etc. While structural assembly onEarth is a well-established construction approach, many technology gapsexist for the automated assembly of truss-based structures on the Moon.Specifically, joining technologies and robotic tools are required toenable efficient and reliable autonomous/automated assembly of thesestructures, which are often composed of hundreds of individualelements.

 

Proposals areinvited for the development of robotic assembly and joining concepts andthe corresponding robotic tools required to assemble a tall truss-basedtower (specific tower design information is provided below). However,extensibility of the robotic tools and joining concepts to otherstructural assemblies is highly desirable. Joining methods can include,but are not limited to, mechanical fastening (e.g., rivets), welding,and bonding (both reversible and nonreversible approaches to joining).Proposals to the current solicitation can assume that the truss elementsbeing assembled are between 0.5 and 2.0 m in length, with either anangle or square prismatic cross sections (cross-section dimensionslisted below). It is expected that early assembly missions will useEarth-sourced truss elements and that these elements may be eitheraluminum or composite. Over time, however, it is expected thatISRU-based truss elements will replace Earth-sourced elements forlarge-scale infrastructure development. Thus, concepts that supportassembly of Earth-sourced and ISRU-based truss elements are ofparticular interest. Finally, it is also assumed that a commercialgeneral-purpose, space-capable robotic manipulating arm will beavailable and that proposals shall concentrate on the development andintegration of specialized robotic end-effectors and tooling requiredfor assembly; however, it is desirable for proposers to specify thecommercial robot capabilities and other support equipment assumed intheir concept (reach, payload capacity, power consumption, etc.).

 

Note: Thetower, joining approach, and robotic assembly system is not expected tobe flight qualified, but it should have a clear path to flight.

 

Focusedapplication for development - Assembly of a tall lunar tower:

  • Lunar tower height: 50-m classlunar tower (10-m-tall lunar tower segment assumed for grounddemonstration).
  • Lunar tower payload: 1,500 kgat top of tower (250 kg Earth equivalent for 1/6 gravity loads forground demonstration).
  • Tower assembly tolerance:Straight to within ±1-degree tilt when assembled on ahorizontal surface.
  • Factor of safety of 5 onbuckling and 10,000 psi maximum stress.
  • Assume assembly site is levelto within ±2.5 degrees.
  • Assume a suitablefoundation/interface is available for assembly; however, proposals arefree and encouraged to provide/derive their own foundation/interfacerequirements.
  • NASA reference concept ofoperations (ConOps) = Module build and lift assembly approach (i.e.,assemble a truss module or bay, lift up and assemble the next modulebelow, repeat until tower is fully erected).

Trusselement geometries:

  • Truss element lengths: 0.5to 2.0 m (it can be assumed that intermediate lengths can be obtained ifnecessary).
  • Truss element cross section:
    • Angle: flange length 10 mm,20 mm, 40 mm; flange thickness 2.0 mm, 4.0 mm, 6.0 mm;
    • Square rod: 10mm2, 15 mm2, 20 mm2

(It can be assumed that trussescan be modified to aid in the assembly process if necessary, e.g.,additive or subtractive manufacturing.)

 

Trusselement materials:

  • Earth-sourced = aluminum 6061,graphite-epoxy
  • ISRU-based = 98% pure aluminum(properties similar to 1-series untempered aluminum; E = 10 Msi, yield~5 ksi)

Phase Iefforts are expected to focus primarily on system design and feasibilitystudies and proof-of-concept tests to identify and demonstrate keytechnology functions such as robotic truss manipulation, joint design,joining, etc.; Phase II efforts will be used to mature thesetechnologies and concepts and to conduct a ground demonstration torobotically assemble a 10-m-tall tower. The resulting assembly systemand demonstrated assembly process must be scalable to a 50- to 80-m-talllunar power and communications tower.

 

Proposalelements of interest include, but are not limited to, thefollowing:

  • Robotic tools for assemblythat are compatible with commercially available robotic manipulatorarms.
  • Concepts that maximizestructural efficiency, minimize power requirements and complexity, andmaintain suitable tolerances during assembly (not to exceed a 1-degreetilt when assembled on a horizontal surface) are desired.
  • Joining concepts for assemblyof composite and/or aluminum truss structures (including the joiningmethod and any necessary fittings/tooling/jigging).
  • Joint/node designs. In situmanufacturability, robotic assembly considerations, inspection.
  • Concept of operationsdescribing process to assemble a tall tower using the robotic tools andjoining methods developed.
  • In situ certification andproof testing.
  • Description of the assumedrobotic system(s) and infrastructure necessary for the proposedapproach, including reach, payload, etc. of the individual roboticagents.
  • Preliminary proof-of-conceptdemonstrations, methods, and equipment.
  • Discuss application oftechnology to the assembly of other truss-based structures, e.g., walls,arches, and domes.

Note: Proposal does not have toproduce space-rated equipment; however, the concept and processes shallbe extensible to the lunar environment. The lunar daytime environmentshould be considered for assembly operations (1/6 gravity,temperature, radiation, vacuum, lighting, powerrequirements). Justification of design choices shall beincluded.

Expected TRL or TRL Range at completion of theProject: 3 to 5

Primary TechnologyTaxonomy:

  • Level 1 07Exploration DestinationSystems
  • Level 2 07.X OtherExploration Destination Systems

Desired Deliverablesof Phase I and PhaseII:

  • Research
  • Analysis
  • Prototype
  • Hardware
  • Software

DesiredDeliverables Description:

Phase I must include the design and test of criticalelements associated with the proposed robotic technologies and joiningmethods needed to assemble truss-based structures, leading to a10-m-tall tower ground assembly demonstration in Phase II. For example,proposed truss configuration and joint designs, structural analysis anddesign justification, and a summary of assembly trials and test resultsfrom Phase I must be included. Phase I must also include a ConOps forthe assembly of the tower and the design and test plan of the roboticassembly system functions needed for Phase II. Phase I proposals shouldresult in at least TRL-4 structures and robotic assembly system.

 

Note: It is expected that notall element lengths or cross sections will be applicable to the designof a tall tower; however, preference will be given to proposals withversatile approaches that accommodate larger combinations of the trusselements described above.

 

Phase II deliverables mustinclude final robotic assembly system design, tower and joint design,and a ground demonstration of a 10-m-tall tower assembly. The tower isexpected to be constructed using robotic systems and implements andjoint designs developed in Phase I. Clear evidence of the extensibilityand scale-up of the ground demonstration system concept to 50- to80-m-tall lunar towers shall be provided. Structures and systems must bedeveloped to a minimum of TRL-5. Phase II assembly shall also considerthe integration and deployment of a surrogate 100-kWe solar array orother relevant elements.

State of the Art and CriticalGaps:

Whilecivil engineering and construction are well-established practices onEarth, automated lunar applications remain at low TRLs. Large-scalelunar infrastructure will require the construction of towers, landingpads, shelters, and habitats, many of which can be accomplished by theassembly of common structural elements such as trusses and panels. Todate, very few activities have been conducted to develop roboticassembly of large-scale truss-based structures such as 50- to 100-m-talltowers or arches for shelters and habitats. Most assembly technologieshave been proof-of-concept and developed at a small scale. Thus, toaccomplish large-scale structural assembly on the lunar surface, joiningtechnologies and robotic assembly systems are needed.

 

NASA Moon toMars Objectives: LI-1 Development of a Global Power Grid, and LI-4Industrial Scale Construction Capabilities—Roads withAutonomous Navigation Aids and Assembly of Towers.

 

The NASASpace Technology Mission Directorate (STMD) STARPort database currentlyincludes four technology gaps related to assembly of structures, forexample, power towers:

  • Assemble truss-basedtower.
  • Structural elements forassembly.
  • Structural joints/joiningtechnology.
  • Autonomy and robotics toassemble the tower.

Relevance / ScienceTraceability:

Roboticassembly and outfitting of infrastructure directly addresses thefollowing:

  • NASA Moon to Mars Objectives:LI-1 Development of a Global Power Grid, and LI-4 Industrial ScaleConstruction Capabilities—Roads With Autonomous NavigationAids and Assembly of Towers.
  • STMD Strategic Thrust: “Live:Sustainable Living and Working Farther from Earth.”

References:

  • Lunar Surface Innovation Initiative:https://www.nasa.gov/directorates/spacetech/Lunar_Surface_Innovation_Initiative
  • Persistent Assets in Zero-G and onPlanetary Surfaces: Enabled by Modular Technology and RoboticOperations, Doggett et al.: https://arc.aiaa.org/doi/pdf/10.2514/6.2018-5305

Scope Title:

Outfittingof Lunar Surface Structures: Truss-Based PowerTowers

ScopeDescription:

Assembly and outfitting of truss-based structures isone of the leading candidates for establishing some of the early lunarinfrastructure, for example, tall towers (50- to 80-m total height,which includes the attached payload height) for solar power generation,blast containment shields for launch and landing pads, shelters, etc.While manual structural outfitting on Earth is a well-establishedconstruction approach, many technology gaps exist for the automatedoutfitting of truss infrastructure on the Moon—specifically,technologies for routing and securing cables and tubing to a trussstructure, as well as the robotic tools to enable autonomous/automatedoutfitting of these structures.

Proposals are invited for the development ofconcepts to outfit a vertical truss tower, including routing ofelectrical cables; securing cables along the truss structure; andconnection of equipment such as communication packages, cameras, lights,and antenna. Proposals should include concept of operations andassociated robotic tools required to outfit truss power towers. Theprimary focus of this activity is the assembly of a tall truss-basedtower. A power tower is defined as a 50-m-tall, four-longeron trussstructure with solar arrays suspended from a cross member at the top ofthe tower. The cross member rotates to follow the Sun when emplaced atthe lunar south pole. The truss elements are expected to includecomposite members when assembled from Earth-sourced materials,transitioning to aluminum members as lunar-derived structural membersbecome available. Thus, concepts that support assembly of Earth-sourcedand ISRU-based truss elements are favored. Extensibility of theoutfitting concepts and robotic tools to other structural assemblies isdesirable. Proposals to the current solicitation can assume that thetruss elements being assembled are as described below. Finally, it isalso assumed that a commercial space-capable robotic manipulating armwill be available and that proposals shall concentrate on thedevelopment of specialized robotic tooling required for assembly;however, it is desirable for proposers to specify the estimatedinfrastructure and robot capabilities assumed (reach, payload capacity,etc.).

Proposal elements of interest include, butare not limited to, the following: cable routing; securingcables to truss tower; and securing equipment such as communicationpackages (20-kg boxes, 50 x 50 x 100 cm), cameras, lights, and antenna(in the 10-kg class), including securing electrical connection ofequipment as well as strain relief.

Truss tower geometries:

  • Truss element lengths: 0.5 to2.0 m (it can be assumed that intermediate lengths can be obtained ifnecessary).
  • Truss element cross section:
    • Square rod: 10mm2, 15 mm2, 20 mm2
    • Angle: flange length 10 mm, 20mm, 40 mm; flange thickness 2.0 mm, 4.0 mm, 6.0 mm

(It can beassumed that trusses can be modified to aid in the outfitting process ifnecessary, e.g., additive or subtractive manufacturing.)

Expected TRL or TRL Range at completion of theProject: 3 to 5

Primary TechnologyTaxonomy:

  • Level 1 12Materials, Structures, Mechanical Systems, andManufacturing
  • Level 2 12.4Manufacturing

DesiredDeliverables of Phase I and PhaseII:

  • Analysis
  • Prototype
  • Hardware

DesiredDeliverables Description:
Phase I must include the design and test ofcritical elements associated with the proposed outfitting of a 50-m-tallpower tower, including robotic technologies to route and secure cablingand support equipment such as communication packages, cameras, lights,and antenna. Phase I must also include a concept of operations foroutfitting of the tower and the proposal for design and testing of theoutfitting concept.

Phase II proposals should result in at leastTRL-5 tools for outfitting of a power tower. Phase II should concentrateon demonstrating key technologies in realistically sized tests of theproposed concept of operations along with required robotic toolsutilizing available terrestrial robots. Phase II deliverables mustinclude demonstration of outfitting a 10-m section of a 50-m tower,including installation and connection of representative equipment.

Note: It is expected that not all elementlengths or cross sections will be applicable to the design of a50-m-tall tower; however, preference will be given to proposals withversatile approaches that accommodate larger combinations of the trusselements described above.

State of the Art and CriticalGaps:

While civil engineering andconstruction are well-established practices on Earth, automated lunarapplications remain at low TRLs. Large-scale lunar infrastructure willrequire the construction of towers, landing pads, shelters, andhabitats. To transition these structures into useable facilities,utility outfitting must be accomplished to establish electrical power,fluid lines (installed for hydraulics, potable and nonpotable water,etc.), and environmental control utilities. This outfitting is the focusof this topic. To accomplish outfitting (i.e., utility installation),robotic routing, connection, and penetration sealing of cables andtubing must occur, followed by joining technologies to connect thesesystems to operational components. 

NASA Moon to Mars Objectives: LI-1Development of a Global Power Grid, and LI-4 Industrial ScaleConstruction Capabilities—Roads With Autonomous NavigationAids and Assembly of Towers.

The NASA Space Technology MissionDirectorate (STMD) STARPort database currently includes four technologygaps related to assembly of structures:

  • Assemble truss-basedtower.
  • Structural elements forassembly.
  • Structural joints/joiningtechnology.
  • Autonomy and robotics to assemble thetower.

Relevance / ScienceTraceability:

This technology is very muchapplicable in STMD support of its NASA, Government, and industrycustomers.

  • STMD for SMD: Radio telescope structural support (back side ofthe Moon).
  • ESDMD and SOMD (formerly HEOMD): Human Habitats, spaceinfrastructure as in buildings, landing pads, roads, berms, radiationprotection, and custom building sizes and shapes.
  • ARMD and Earth-based Government agencies: In situ constructioncapabilities both locally and remote.
  • Industry or Earth-based Government agencies: Rapid construction -small building within 24 hours.

References:

Don’tTake It – Make It: NASA’s Efforts to AddressExploration Logistics Challenges through In Space Manufacturing andExtraterrestrial Construction for Lunar Infrastructure.R.G. Clinton, Jr., PhD; Tracie Prater, PhD; Jennifer Edmunson,PhD; Mike Fiske; Mike Effinger. Novel Orbital and Moon Manufacturing,Materials, and Mass-efficient Design (NOM4D) Kick-Off, December14-15, 2021. https://ntrs.nasa.gov/api/citations/20210025774/downloads/NOM4D%20KO%2012.15.2021.pdf

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