Space Show Webinar: Engineering Structures in Space

Transcription

1 Space Show Webinar: Engineering Structures in Space Haym Benaroya Department of Mechanical & Aerospace Engineering 17 February

2 Elements of the Whole 1. human physiology 2. human psychology 3. plant physiology 4. the lunar surface radiation environment 5. the lunar surface temperature cycles 6. lunar regolith mechanics 7. human factors studies 8. structural mechanics 9. thermal science in low gravity and vacuum 10. low gravity fluid mechanics 11. power systems 12. astronomy requirements on the Moon 13. geology requirements on the Moon n-1. economic theory n. lunar tourism. 2

3 Arthur C. Clarke, 1951 Drawing: R.A. Smith 3

4 A 1962 lunar base study by DeNike and Zahn for a flat region on the Moon that included the Sea of Tranquility (the Apollo 11 landing site). 4

5 g Moon = 1.62 m/s² Lunar Environment internal air pressurization can range from 34.5 kpa (5 psi) to kpa (14.7 psi) protection from radiation and micrometeoroids insulation (temperature differentials of 250 C) 2.5 m m of regolith cover needed 5

6 Additional Critical Environment Factors Regolith dust: very small particles that are easily electrostatically charged, easily suspended and displaced, are abrasive, and attach to everything Moonquakes: Order of magnitude ~ 5 Richter, can last 10 minutes vs. 2 min max on Earth 6

7 Structural Concepts first generation: pre-fabricated and pre-outfitted modules like the ones for the ISS 7

8 Cylinder Modules Brand Griffin 8

9 Courtesy Orbital Sciences 9

10 Emmart Drawing: Carter Emmart 1996 Carter Emmart

11 Structural Design of a Lunar Base Structural Analysis and Design of the RUTGERS Lunar Base Structure 2002-Present 11

12 Lunar Design Reliability What reliability is considered acceptable? Should the Lunar outpost be designed to higher or lower risk tolerances? How does the designer consider reliability of a structure that has never been built before and cannot be tested? Can we afford to fail?

13 Considerations for a Detailed Structural Reliability Study Lunar temperature gradients and material fatigue (exposed structures) Structural sensitivity to high/low temperatures Outgassing for exposed steels/materials Factors of safety according to risk tolerance Dead loads, live loads under lunar gravity Buckling, stiffening, bracing requirements for lunar structures (internally pressurized) New failure modes (micrometeorite impacts)

14 Duplication or repetition of elements for alternative functional channels in case of failure Redundancy

15 Parallelism Multiple options in the face of unanticipated difficulties

16 Logistics Replace or Repair Acquisition, Distribution, Maintenance, Replacement

17 Serviceability limit may lead to Ultimate limit quickly: Design for escape and rescue

18 Design Process **Concurrent Engineering System Design Manufacturing Prototyping Conceptualization *Evaluation Total Life Cycle Acceptable risk? Economic costs Conception Retirement & Disposition Construction *Reliability concepts are analysed at this point. **Move major items early in the cycle to anticipate potential problems. Recycling of System & Components

19 Reliability use GOALS Human Safety Minimum Risk know Design Philosophy Limit States Constructability Ultimate Serviceability Redundancy Limit State Function <= 0 if not Parallelism Failure NEED Logistics Design for Escape & Rescue LINK to USERS LOSS of USE

20 Performance-Based Engineering Input/Intensity Spectrum Covers range of hazard levels Accounts for uncertainty in parameters, relationships Decision variable Damage measure Engineering demand parameter Intensity measure DV DM dg DM EDP dg EDP IM d DV G IM Engineering Demand Fragility/ Damage Cost of repair Or Loss of Function Structural or non- Structural Damage Forces, Displ, Temp. Input Spectra After: Kramer, Mayfield and Mitchell, Ground Motions and Liquefaction Cost/Decision Variable Performance-based engineering methodology leads to decision variables.

21 Comparisons of Concepts On a scale of 1-6, with 6 being the highest reflecting a very positive characteristic of the concept, the following ratings are given to various structural concepts: Three-hinged arch: Transportation 3 Easy of construction 4 Experience with the structural system 6 Foundations 6 Excavation 4 Structure Transp Constr Exper Found. Excav. Total Spherical inflatable Tuft-Pillow Crater base Three-hinged arch Underground

22 Proposed Design: A Tied-Arch Shell Structure global safety factor applied: 5 Concept and picture by F. Ruess and H. Benaroya

23 Design Volume Habitat dimensions: Volume: 120 m 3 per person for a lunar habitat has been recommended Crew size Habitable area Floor height: 4.0 m seems most suitable. Use of slightly magnetic boots could reduce the floor height (need metal floors) = 34.4 m 2 floor area per person. 20% for Equipment & Stowage Total area ~ It will depend not only on the crew size but also on the amount of equipment and stowage space needed.

24 A three-hinged arch Tension force governs arch design Loading and support conditions for the end walls The static load cases: 1-internal pressure 2regolith cover 3partial regolith cover 4-floor loads 5installation loads

25 Structural Design of a Lunar Base Structural Analysis Additional calculation parameters: rise: 5 m regolith modulus of subgrade reaction: 1000 kpa / m global safety factor applied: 5 Contents I. Introduction II. Environment III. Concepts IV. Structural Analysis V. Conclusion

26 Structural Design of a Lunar Base Load Case 1: Internal Pressure Contents I. Introduction II. Environment III. Concepts IV. Structural Analysis V. Conclusion

27 Structural Design of a Lunar Base Load Case 2: Regolith Cover Contents I. Introduction II. Environment III. Concepts IV. Structural Analysis V. Conclusion

28 Structural Design of a Lunar Base Bending Moment: Parabolic Arch Contents I. Introduction II. Environment III. Concepts IV. Structural Analysis V. Conclusion

29 Structural Design of a Lunar Base Bending Moment: Circular Arch Contents I. Introduction II. Environment III. Concepts IV. Structural Analysis V. Conclusion

30 Structural Design of a Lunar Base Cross Section Types Contents I. Introduction II. Environment III. Concepts IV. Structural Analysis V. Conclusion

31 Structural Design of a Lunar Base The Tie / Floor Bending moment distribution (BMD) Floor shape similar to BMD Contents I. Introduction II. Environment III. Concepts IV. Structural Analysis V. Conclusion

32 Structural Design of a Lunar Base Cross Sections: Summary cross section Type 4 is most efficient material: high-strength aluminum arch mass: 31 kg / m² average floor mass: 118 kg / m² max. deflections for operational loads are about 5 cm Contents I. Introduction II. Environment III. Concepts IV. Structural Analysis V. Conclusion

33 Structural Design of a Lunar Base Dynamics Modal shape 1 simulated cam mechanism: f = 172 Hz; a = 4.6 cm no significant increase in forces and deflections was found Contents I. Introduction II. Environment III. Concepts IV. Structural Analysis V. Conclusion

34 Structural Design of a Lunar Base The End Walls: Bending Moments Bending moment In the x-direction. Blue represents Minimum bending moment of knm/m. Red represents Maximum bending Moment of 16.8 knm/m. Contents I. Introduction II. Environment III. Concepts IV. Structural Analysis V. Conclusion

35 Structural Design of a Lunar Base Hinged Connections: Variant 1 Contents I. Introduction II. Environment III. Concepts IV. Structural Analysis V. Conclusion

36 Structural Design of a Lunar Base Hinged Connections: Variant 2 Concept: Jörg Schänzlin Contents I. Introduction II. Environment III. Concepts IV. Structural Analysis V. Conclusion

37 Structural Design of a Lunar Base Wall Connections Contents I. Introduction II. Environment III. Concepts IV. Structural Analysis V. Conclusion

38 Structural Design of a Lunar Base The Construction Sequence Contents I. Introduction II. Environment III. Concepts IV. Structural Analysis V. Conclusion

39 Structural Design of a Lunar Base Base Layout Contents I. Introduction II. Environment III. Concepts IV. Structural Analysis V. Conclusion

40 Base Star Ledger Drawing: Andre Malok, Newark Star Ledger 40

41 Conclusions Lunar structures must: minimize mass show robustness (reliability) be expandable be easy to construct eventually use local materials (ISRU) be transferable to Mars with minor redesign Performance-Based Engineering Decision variable Damage measure Engineering demand parameter Intensity measure DV DM dg DM EDP dg EDP IM d DV G IM Cost of repair Or Loss of Function Structural or non- Structural Damage Forces, Displ, Temp. Input Spectra The following slides are supplementary.