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1 Pre-decisional NASA Internal Use Only Curved Extendable/Retractable Boom-Deployed Bag Asteroid Capture System Concept Scott Belbin, Mechanical Systems.

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Presentation on theme: "1 Pre-decisional NASA Internal Use Only Curved Extendable/Retractable Boom-Deployed Bag Asteroid Capture System Concept Scott Belbin, Mechanical Systems."— Presentation transcript:

1 1 Pre-decisional NASA Internal Use Only Curved Extendable/Retractable Boom-Deployed Bag Asteroid Capture System Concept Scott Belbin, Mechanical Systems Branch NASA Langley Research Center (757) Scott Belbin, Mechanical Systems Branch NASA Langley Research Center (757)

2 2 Pre-decisional NASA Internal Use Only RFI Concept Criteria  Capture an asteroid of unknown composition (possible dust/rubble pile) – Encapsulation bag required  Atlas V Medium Payload Fairing  Asteroid Mass ≤1000 metric tons  Accommodate different asteroid shapes  17.8m x 8.8m x 8.8m prolate spheroid  14m x 14m x7m oblate spheroid

3 3 Pre-decisional NASA Internal Use Only Design Drivers  Short development time: Launch in 2018  Need High TRL approach with minimal complexity  Deploy, close and retract bag without robot arms  Electrically driven system only to reduce mass (abundant S/C bus capacity)  Need to be able to reliably model  Rigid structures are readily modeled and simulated  Rigid structures to enhance dynamic stability while spinning up to match asteroid  Extendables are predictable and functionally reliable  Need to be able to test  Test in 1G  Vacuum chamber not required for testing (no inflatables), only still air needed  Need to provide crew access  Non-inflatable capture bag – single ply easy for crew to cut through  Non-inflatables allow access panels to be easily incorporated

4 4 Pre-decisional NASA Internal Use Only Concept Overview  Proposed system uses extendable booms to deploy a non- inflatable bag to capture and control an asteroid Stowed Deploy bag then match spin for capture Cinched up and retracted, Booms kink and conform to shape of the asteroid, ready to de-spin asteroid

5 5 Pre-decisional NASA Internal Use Only Deployment Storyboard 1) Booms in initial position 2) Bag ready to deploy3) Booms deploy, pulling bag 4) 1 st section taut, pulls next 5) 2 nd section taut, pulls next 6) Curved booms minimizes material 7) 3 rd section taut, pulls last 8) Booms stop at their limits 9) System ready for spin-up

6 6 Pre-decisional NASA Internal Use Only ConOps  Booms deploy single-ply Vectran bag  Circumferential cinch cables close bag, pulling in the booms which kink and conform to the asteroid’s shape  Booms retract to draw asteroid against spacecraft  Independent boom drives allow for CG adjustment of asteroid Add cinch motors Add multiple pics of sequences Bag mounted winches drive cinching cables in batten pockets Single drive in stowed position 500 mm 15 meters 20 meter booms

7 7 Pre-decisional NASA Internal Use Only  Lenticular cross section chosen due to favorable buckling characteristics wrt conforming to the asteroid’s shape  Conducted trades for materials and minimum cross sections  Results:  Titanium: 325mm width, 390mm flattened  MS =  1756 g/m  kg per boom  Composite: 250 mm width, 280mm flattened  MS =  464 g/m  9.51 kg per boom  Composite booms selected for mass estimate Preliminary Sizing Results

8 8 Pre-decisional NASA Internal Use Only Current Best Estimate of Mass Total Boom System Mass124.87kg Enclosure System Mass69.42kg Structure Mass27.00kg Attachments and Cabling10.00kg Capture System Avionics20.00kg Micro Meteorite and Thermal Shielding30.00kg CBE281.29kg Contingency Percentage30% Contingency Mass84.39kg CBE + Contingency365.68kg  Used Vectran areal density as reference for bag mass calcs  Incorporated catalog selections for space-rated drive motors and gearing  Based on preliminary Pro-E models; included large margins of uncertainty typical of concept level design

9 9 Pre-decisional NASA Internal Use Only Cursory Schedule in RFI Submittal  Timeline: 10/ /2018  Concurrent design and development testing  Includes boom tooling design and procurement  Incorporates Ground Test Article build and test

10 10 Pre-decisional NASA Internal Use Only Potential Next Steps  Boom cross section design and analysis  Boom section property demonstration (bending, torsion, buckling)  Boom to drive buckling limit demonstration  Bag material demonstration for abrasion and puncture resistance  Cinch cable drive design and testing  Boom tooling design and semi-section bonding demonstration  Boom extension and retraction demonstration

11 11 Pre-decisional NASA Internal Use Only Conclusion Dynamically stable in spin-up Medium to High TRLs Reliable mechanical drives Leverages abundant electrical power to reduce mass; no gas system Can demonstrate in 1G environment CBE Mass meets LV criteria Improved Crew Access Scott Belbin, Mechanical Systems Branch NASA Langley Research Center, Hampton VA (757)

12 12 Pre-decisional NASA Internal Use Only Design Details Backup

13 13 Pre-decisional NASA Internal Use Only Boom Type Trade 1: STEM Boom  Storable Tubular Extendable Member  Extensive flight heritage; TRL 9  Formable as a curved boom  Exerts force during extension for capture bag unfurl  Exerts retraction force to bring asteroid to bear against spacecraft  Drives mount on torsion spring bases to accommodate flexure during capture  Good Bending and torsional capability  Poor Buckling/Crippling characteristics wrt conforming to asteroid; possible reduction in tensile capability; no recovery from buckling/crippling for retraction into spool Tubular shape collapses and spools without permanent deformation. Section shape is restored when spooled out Variations of the STEMboom concept [Source: NASA] STEM TIP Drum antenna boom, self deploying [Source: Northrop Grumman]

14 14 Pre-decisional NASA Internal Use Only Boom Type Trade 2: Lenticular Section  TRL 5 – tested in zero-G  Formable as a curved boom (two halves construction, continuous length members)  Exerts force during extension for capture bag unfurl  Exerts retraction force to bring asteroid to bear against spacecraft  Drives mount on torsion spring bases to accommodate flexure during capture  Good Bending and torsional capability  Good Buckling/Crippling characteristics wrt conforming to asteroid; no appreciable tensile capability reduction; recoverable from buckling/crippling for re-spool Lenticular shape readily collapses and spools without permanent deformation. Section shape restores when spooled out

15 15 Pre-decisional NASA Internal Use Only  Examined load case from de-spin of asteroid  Used loads for JPL2 case (worst case)  7500N tangential de-spin load (6 booms, 1250N per boom)  Assumed contact at half-diameter (10 meters) but more likely ~6 meters (at second cinch cable); conservative  Analyzed for simple cantilever load case in strong axis  Safety Factors used: 1.4 on ultimate and 1.25 on yield  Three materials analyzed: AL 6061 T6, Ti-Al6-4V, Carbon Composite (T500 12k/976)  Geometry optimized until MS=>0.0 to determine minimum section size  Results: Aluminum min. section too large to fit volumetric constraints; Titanium and Composite are viable candidates Preliminary Lenticular Boom Sizing FTFT

16 16 Pre-decisional NASA Internal Use Only Preliminary Lenticular Boom Sizing, Min. Cross Section  Examined for lateral loads in strong axis direction  Safety Factors applied  Beam section properties from Pro-E  Composite properties from Mil-Hbk-17  Case shown here for T1-6Al-4V, 325mm section width Design Data SF, ultimate1.40 SF, yield1.25 Force at half Ø contact pts, total7500N No. of Booms6 Beam Geometry Beam Length20.50m Beam Length to half Ø contact pts.10m End Force, Tangential1250N Neutral axis dist., strong axis, c0.1625m MOI, strong axis3.18E+06mm^4 Beam Calcs Max Moment, M12500Nm Max Stress, δ639.55MPa Ti-6Al-4V,.020" thk Young's Mod, E113.8GPa Ftu951.48Mpa Fty882.53Mpa MS, Ftu0.059 MS, Fty0.094 Beam mass/length1.756kg/m Beam mass (1)36.00kg Max Displacement, w1153mm T500 12k/976 unidirectional tape, Mil 17, V2, Pg "thk layup Tensile Mod, E141.34GPa Ftu Mpa MS, Ftu0.495 Beam mass/length0.464kg/m Beam mass (1)9.51kg Max Displacement, w928mm Flattened Width =390mm I= mm^4 Flattened Width =280mm I= mm^4  Solving for minimum composite cross section = 250mm width

17 17 Pre-decisional NASA Internal Use Only Conical Instrumentation Volume provides unobstructed forward view Boom Mechanism Volume Capture Bag Stow Volume Volume trades allowed as design matures Atlas V Medium Fairing Payload Volume Packaging

18 18 Pre-decisional NASA Internal Use Only Design Details  Bag made of six 4-panel gores with Velcro deployment staging (can deploy well in advance of asteroid encounter)  Bag-mounted winches driving cinch cables in batten pockets close the bag in sequence around the asteroid, pulling the booms inward  Booms buckle/cripple by design as they contact the asteroid and conform to asteroid’s shape without losing tensile capability  Booms make a rigid connection for de- spin  Booms retract to draw asteroid against spacecraft  Independent boom drives allow for CG adjustment of asteroid Cinch Cables

19 19 Pre-decisional NASA Internal Use Only Internal View  Bag Dimensions  15 meters across flats at mouth, 18 meters across apices  20 meter booms  Thin Vectran construction w/reinforcement doubling in critical areas  Instrumentation Volume  Unobstructed view for asteroid characterization and bag deployment  Provides rigid coupling to captured asteroid while protecting boom drives  Bag Volume  Facilitates bag packaging and unfurling by mimicking bag shape  Boom Drive Volume  Allows for boom drive flexure motion  Provides volume for electrical harnesses and system to bus attachments

20 20 Pre-decisional NASA Internal Use Only Boom Drive and Bag Attachments Bag Extraction Attach Point attaches to mouth of bag  Cable Rings attach to bag via straps  Boom unfurls first segment  Subsequent segments Velcro retained  Booms slide through rings; bag segments become taut then pulls subsequent segments  Drive with Torsion Spring Base  Decreases risk of local boom buckling at boom exit point  Internal guides and compliant members further decrease local crippling risk


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