Space Show Webinar: Engineering Structures in Space · Space Show Webinar: Engineering Structures...
-
Upload
dinhkhuong -
Category
Documents
-
view
229 -
download
0
Transcript of Space Show Webinar: Engineering Structures in Space · Space Show Webinar: Engineering Structures...
1
17 February 2013
Haym Benaroya
Department of Mechanical
& Aerospace Engineering
Space Show Webinar: Engineering Structures in Space
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.
3
Arthur C. Clarke, 1951
Drawing: R.A. Smith
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).
5
Lunar Environment
• gMoon = 1.62 m/s²
• internal air pressurization can range from 34.5
kPa (5 psi) to 101.3 kPa (14.7 psi)
• protection from radiation and micrometeoroids
• insulation (temperature differentials of 250°C)
•2.5 m - 3.0 m of regolith cover needed
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
7
Structural Concepts
• first generation:
pre-fabricated and pre-outfitted
modules like the ones for the
ISS
8
Cylinder
Modules
Brand Griffin
9 Courtesy Orbital Sciences
Drawing: Carter Emmart 1996
Emmart
Carter Emmart
11
Structural Analysis and
Design of the
RUTGERS
Lunar Base Structure 2002-Present
Structural Design of a Lunar Base
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?
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)
Redundancy
Duplication or repetition of elements for alternative functional channels in case of failure
Parallelism
Multiple options in the face of unanticipated difficulties
Logistics • Replace or Repair
• Acquisition, Distribution, Maintenance, Replacement
Serviceability limit may lead to Ultimate limit quickly: Design for escape and rescue
Design Process
Prototyping
Conceptualization
*Evaluation
Manufacturing
Construction
Total Life Cycle
Conception
**Concurrent Engineering
Recycling of System & Components
Retirement & Disposition
System Design
Acceptable risk ?
Economic costs
*Reliability concepts are analysed at this point. **Move major items early in the cycle to anticipate potential problems.
Reliability
• Human Safety • Minimum Risk
Design Philosophy Limit States
Redundancy
Logistics
Parallelism
Ultimate Serviceability
Limit State Function <= 0
Failure
Design for Escape & Rescue
GOALS
use know
if not
NEED
Constructability
LINK to USERS’ LOSS of USE
PerformancePerformance--Based EngineeringBased Engineering
• Covers range of hazard levels
• Accounts for uncertainty in parameters, relationships
dIMEDPdGEDPDMdGDMDVG IMDV
Intensity
measure
Engineering
demand
parameter
Damage
measureDecision
variable
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
Performance-based engineering methodology leads to decision variables.
Input/Intensity Spectrum
Fragility/ Damage
Cost/Decision Variable
Engineering Demand
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:
17 4 4 1 2 6 Underground
23 6 4 6 4 3 Three-hinged arch
19 6 2 4 2 5 Crater base
21 6 5 1 3 6 Tuft-Pillow
14 2 3 1 3 5 Spherical inflatable
Total Excav. Found. Exper Constr Transp Structure
Three-hinged arch: •Transportation 3 •Easy of construction 4 •Experience with the structural system 6 •Foundations 6 •Excavation 4
Proposed Design:
A Tied-Arch Shell Structure
Concept and picture by F. Ruess and H. Benaroya
global safety factor applied: 5
Design Volume Habitat dimensions: • Volume: 120 m3 per person for
a lunar habitat has been recommended
• Floor height: 4.0 m seems most
suitable. Use of slightly magnetic boots could reduce the floor height (need metal floors) = 34.4 m2 floor area per person.
It will depend not only on the
crew size but also on the amount of equipment and stowage space needed.
415 320 250 Total area ~
69 55 41 20% for Equipment & Stowage
343 275 206 Habitable area
10 8 6 Crew size
A three-hinged arch
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
Tension force governs arch design
Structural Analysis
Structural Design of a Lunar Base
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
Load Case 1: Internal Pressure
Structural Design of a Lunar Base
Contents – I. Introduction – II. Environment – III. Concepts – IV. Structural Analysis – V. Conclusion
Load Case 2: Regolith Cover
Structural Design of a Lunar Base
Contents – I. Introduction – II. Environment – III. Concepts – IV. Structural Analysis – V. Conclusion
Bending Moment: Parabolic Arch
Structural Design of a Lunar Base
Contents – I. Introduction – II. Environment – III. Concepts – IV. Structural Analysis – V. Conclusion
Bending Moment: Circular Arch
Structural Design of a Lunar Base
Contents – I. Introduction – II. Environment – III. Concepts – IV. Structural Analysis – V. Conclusion
Cross Section Types
Structural Design of a Lunar Base
Contents – I. Introduction – II. Environment – III. Concepts – IV. Structural Analysis – V. Conclusion
The Tie / Floor
Structural Design of a Lunar Base
Contents – I. Introduction – II. Environment – III. Concepts – IV. Structural Analysis – V. Conclusion
Bending moment
distribution (BMD)
Floor shape similar to
BMD
Cross Sections: Summary
Structural Design of a Lunar Base
• 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
Dynamics
Structural Design of a Lunar Base
Contents – I. Introduction – II. Environment – III. Concepts – IV. Structural Analysis – V. Conclusion
• simulated cam mechanism: f = 172 Hz; a = 4.6 cm
• no significant increase in forces and deflections was found
Modal shape 1
The End Walls: Bending Moments
Structural Design of a Lunar Base
Contents – I. Introduction – II. Environment – III. Concepts – IV. Structural Analysis – V. Conclusion
Bending moment In the x-direction. Blue represents Minimum bending moment of -90.4 kNm/m. Red represents Maximum bending Moment of 16.8 kNm/m.
Hinged Connections: Variant 1
Structural Design of a Lunar Base
Contents – I. Introduction – II. Environment – III. Concepts – IV. Structural Analysis – V. Conclusion
Hinged Connections: Variant 2 Concept: Jörg Schänzlin
Structural Design of a Lunar Base
Contents – I. Introduction – II. Environment – III. Concepts – IV. Structural Analysis – V. Conclusion
Wall Connections
Structural Design of a Lunar Base
Contents – I. Introduction – II. Environment – III. Concepts – IV. Structural Analysis – V. Conclusion
The Construction Sequence
Structural Design of a Lunar Base
Contents – I. Introduction – II. Environment – III. Concepts – IV. Structural Analysis – V. Conclusion
Base Layout
Structural Design of a Lunar Base
Contents – I. Introduction – II. Environment – III. Concepts – IV. Structural Analysis – V. Conclusion
40
Drawing: Andre Malok, Newark Star Ledger
Base – Star Ledger
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
PerformancePerformance--Based EngineeringBased Engineering
dIMEDPdGEDPDMdGDMDVG IMDV
Intensity
measure
Engineering
demand
parameter
Damage
measureDecision
variable
Cost of
repair Or
Loss of
Function
Structural
or non-
Structural
Damage
Forces, Displ,
Temp.Input
Spectra
The following slides are supplementary.