Design/Analysis of Isolation System for the Oceaneering Space Systems Cargo Transport Container Arya Majed, Ph.D. Applied Structural Dynamics, Inc. www.appliedstructuraldynamics.com ASD-TB-2-27 Updated:1/1/22
CTC System Architecture Cargo Transport Container (CTC) An isolated cargo box manifested on Space Shuttle cross-bay carriers intended to carry a wide range of cargo mass while mitigating the Shuttle dynamic environment 2
Task ASD tasked with the design, analysis, and test support of an isolation system for the OSS Cargo Transport Container (CTC) that will mitigate the Space Shuttle transient and random environments 3
Tasks Performed Design/specification/optimization of isolation system Isolation system modeling CTC finite element model (FEM) dynamic math model reduction Variational Coupled loads analyses Evaluated CTC capability to be launched at the specified locations on cross-bay carriers Evaluated with varying CTC cargo weight on the cross-bay carriers From 85 to 535 lbs Optimized isolation system parameters Developed predicted load environments for the CTC mounted at each carrier location Test Support 4
Definitions Cargo Element (CE) across-the-bay cargo carrier structure attached to shuttle via primary and stabilizer trunnions Cargo Item (CI) substructures manifested on a CE Cargo Transport Container (CTC) An isolated CI intended to carry a wide range of cargo mass while mitigating the CE dynamic environment Coupled Loads Analysis (CLA) Transient analysis of the coupled Shuttle / CE system for the events of liftoff and landing Variational Coupled Loads Analysis (VCLA) CLAs with parameter variation yielding the entire spectrum of response relative to that parameter Base-Shake Analysis An approximate analysis method where the coupling of the CE to CI is ignored 5
Background CI from dynamic environment involves: Tuning Suspension soft enough to mitigate significant dynamic amplification Low frequency transients (< 35 Hz) Structural-borne random vibrations Suspension stiff enough to contain excessive relative motion for both transient and quasi-static flight events Damping Mitigate any amplifications due to coupling of the isolated CI frequencies with integrated CE frequencies CI tuning easily accomplished for CI integrated on stiff carrier structure, i.e., insignificant isolated CI/integrated CE coupling 6
Background - continued With integrated CE frequencies a function of the manifested cargo weight and the isolated CI frequencies a function of CI weight, adverse coupling with CI amplified response is possible Isolator damping becomes critically important Proof of concept best demonstrated with multiple Coupled Loads Analyses, showing the entire spectrum of the isolated CTC response as a function of overall manifested CE weight and CI weight Coupled Loads Analyses varying a parameter in each analysis are referred to as a Variational Coupled Loads Analyses Beware - base-shake analyses cannot account for isolated CI/integrated CE coupling! 7
Aeroflex Wire rope Isolators Totally passive, robust design Weakly nonlinear stiffness characteristics Nonlinear Coulomb friction energy dissipation Significant energy dissipation through internal friction, equivalent ζ ~ 15% of critical damping Certified for flight aboard Orbiter, utilized in aft fuselage Aeroflex springs in the Main Propulsion System (MPS) Orbiter aft fuselage Attenuation and shock protection for MPS components 8
Aeroflex Wire-rope Isolators - continued Off the shelf hardware Wide range of application in vibration and shock isolation 9
Aeroflex Wire-rope Isolators - Tuning Longeron Xo Liftoff Dynamic Environment Tune Isolator 1
Aeroflex Wire-rope Isolators - Tuning Longeron Yo Liftoff Dynamic Environment Tune Isolator 11
Aeroflex Wire-rope Isolators - Tuning Longeron Zo Liftoff Dynamic Environment Tune Isolator 12
Aeroflex Wire-rope Isolators Selection Frequency Stiffness f = 1 2π K M K = 4π 2 f 2 M = 4π 2 f 2W / 386 Gives Isolator total stiffness a function of the designated isolation frequency and weight of the isolated object Isolator stiffness = total stiffness / number of isolators Select from Aeroflex Manual Dynamic Travel - x = K 1 Ma = a 4π 2 f 13 2
Aeroflex Wire-rope Isolators Selection - continued 14
Aeroflex Wire-rope Isolators Selection - continued 15
Aeroflex Wire-rope Isolators Selection - continued 16
Aeroflex Wire-rope Isolators Stiffness Model Derive a stiffness matrix for Aeroflex helical spring Stiffness (per Aeroflex brochure) Kct is the compression/tension stiffness Ksr is the shear/roll stiffness h is the height of the spring L is the length of the spring w is the bar width 17
Aeroflex Wire-rope Isolators Stiffness Model Coordinate System Stiffness derived in spring coordinate system A y z A View A-A y x 18
Aeroflex Wire Rope Stiffness Matrix [ K sr K ct K sr 1 h K sr 2 1 h K sr 2 1 2 L K ct 12 1 h K sr 2 K sr 1 h K sr 2 K sr K ct K sr 1 h K sr 2 1 h K sr 2 1 2 L K ct 12 1 2 L K sr 12 1 h K sr 2 1 2 w K ct 2 K sr K ct K ct K sr K sr 1 h K sr 2 1 h K sr 2 1 2 L K ct 12 1 h K sr 2 1 h K sr 2 1 2 L K ct 12 1 h K sr 2 1 w 2 K ct 2 1 h K sr 2 1 h K sr 2 1 2 L K sr 12 CB13-3 Aeroflex wire rope springs Ksr = 42 lbs./inch Kct = 169 lbs./inch L = 14 inches 19 1 h K sr 2 1 2 L K sr 12 1 h K sr 2 1 w 2 K ct 2 1 2 L K sr 12 1 2 w K ct 2 ]
Analysis Plan Variational Coupled Loads Analysis Cargo bay manifest (typical Utilization Logistic Flight) ODS RMS ICC ( 4 CTC units, 2 hard-mounted / 2 isolated) MPLM LMC (2 CTC units, 1 hard-mounted / 1 isolated) Conduct Variational Coupled Loads Analysis Develop the full spectrum of response variations of the isolated and hard-mounted CTCs as the cargo weight for each box is varied from 85 to 535 lbs by 45 lbs increments 2
Cargo Bay Manifest for Coupled Loads Analysis 21
OSS CTC Finite Element Model (FEM) with Aeroflex Springs Frequencies Note: Rigidly mounted CTC with 535 Lbs of cargo frequency > 3 Hz 22
ICC CE FEM Integrated with 4 PFAPs CTC_5k Rigid CTC_7k Isolated CTC_9k Rigid KYA CTC_3k Isolated XICC 23
Integrated ICC / CTC FEM 24
Integrated LMC/CTC Sketch Top View LMC Model delivered as a reduced Dynamic Math Model Isolated CTC Rigidly Mounted CTC 25
Integrated LMC/CTC Sketch Front View 26
CTC Xo Cargo Acceleration Spectrum Isolated vs. Rigidly Mounted ICC Liftoff VCLA 27
CTC Yo Cargo Acceleration Spectrum Isolated vs. Rigidly Mounted ICC Liftoff VCLA 28
CTC Zo Cargo Acceleration Spectrum Isolated vs. Rigidly Mounted ICC Liftoff VCLA 29
CTC Xo Net-Load Factor Spectrum Isolated vs. Rigidly Mounted ICC Liftoff VCLA 3
CTC Yo Net-Load Factor Spectrum Isolated vs. Rigidly Mounted ICC Liftoff VCLA 31
CTC Zo Net-Load Factor Spectrum Isolated vs. Rigidly Mounted ICC Liftoff VCLA 32
CTC AFRAM/PFRAM I/F Force Spectrum 34311 - Z ICC Liftoff VCLA 33
CTC/AFRAM I/F Rel. Displ. Spectrum -x/-y corner Xo ICC Liftoff VCLA 34
CTC/AFRAM I/F Rel. Displ. Spectrum -x/-y corner Yo ICC Liftoff VCLA 35
CTC/AFRAM I/F Rel. Displ. Spectrum -x/-y corner Zo ICC Liftoff VCLA 36
CTC/AFRAM I/F Force -x/+y corner Y (element coordinate system) ICC Liftoff VCLA 37
CTC Xo Cargo Acceleration Time-history Isolated vs. Rigidly Mounted (13 lbs of Cargo) ICC Landing CLA 38
CTC Yo Cargo Acceleration Time-history Isolated vs. Rigidly Mounted (13 lbs of Cargo) ICC Landing CLA 39
CTC Zo Cargo Acceleration Time-history Isolated vs. Rigidly Mounted (13 lbs of Cargo) ICC Landing CLA 4
CTC Xo Cargo Acceleration Time-history Isolated vs. Rigidly Mounted (49 lbs of Cargo) ICC Landing CLA 41
CTC Yo Cargo Acceleration Time-history Isolated vs. Rigidly Mounted (49 lbs of Cargo) ICC Landing CLA 42
CTC Zo Cargo Acceleration Time-history Isolated vs. Rigidly Mounted (49 lbs of Cargo) ICC Landing CLA 43
CTC Xo Cargo Acceleration Spectrum Isolated vs. Rigidly Mounted ICC Landing VCLA 44
CTC Yo Cargo Acceleration Spectrum Isolated vs. Rigidly Mounted ICC Landing VCLA 45
CTC Zo Cargo Acceleration Spectrum Isolated vs. Rigidly Mounted ICC Landing VCLA 46
CTC Xo Cargo Acceleration Spectrum Isolated vs. Rigidly Mounted LMC Liftoff VCLA 47
CTC Yo Cargo Acceleration Spectrum Isolated vs. Rigidly Mounted LMC Liftoff VCLA 48
CTC Zo Cargo Acceleration Spectrum Isolated vs. Rigidly Mounted LMC Liftoff VCLA 49
CTC Xo Cargo Acceleration Spectrum Isolated vs. Rigidly Mounted LMC Landing VCLA 5
CTC Yo Cargo Acceleration Spectrum Isolated vs. Rigidly Mounted LMC Landing VCLA 51
CTC Zo Cargo Acceleration Spectrum Isolated vs. Rigidly Mounted LMC Landing VCLA 52
Net-load Factor Summary Tables from Coupled Loads Analyses ICC Liftoff Flight Event Low Frequency Random Vibration 1 Combination (RSS one axis 2 at a time) 3 Landing LMC Liftoff Flight Event Low Frequency Random Vibration 1 Combination (RSS one axis 2 at a time) 3 Landing Nx 3.86 5.4 6.64 3.86 3.86 3. Unisolated Ny 4.39 8 4.39 9.13 4.39 3.73 Nx 5.51 5.4 7.71 5.51 5.51 3.3 Unisolated Ny 3. 8 3. 8.54 3. 1.93 53 Nz 2.55 5.4 2.55 2.55 5.97 3.47 Nz 2.77 5.4 2.77 2.77 6.7 3.8 Nx 2.84 Isolated Ny 2.8 Nz 2.88 2.84 2.8 2.88.92.86 4.14 Nx 2.65 Isolated Ny 1.41 Nz 1.19 2.65 1.41 1.19.84 1.23 2.7
Sidewall Mounted CTC Net-Load Factors Base-shake analysis conducted on a 31 lb isolated CTC using some sidewall accelerations from CLO11 and LE751 forcing functions Sidewall Mounted Liftoff Flight Event Low Frequency Random Vibration 1 Combination (RSS one axis 2 at a time) 3 Landing IDD Ny 7. 8. 7. 1.6 7. 7. Nx 7. 5.4 8.8 7. 7. 6. Nz 6. 5.4 6. 6. 8.1 8. Nx 2.2. Isolated Ny 2.7. Nz 2.2. 2.2 2.7 2.2.6 1.4 2.2 Variational Coupled Loads Analysis considering the entire CTC cargo weight range and potential coupling to GAS Beam to be conducted in Phase II 54
Conclusions Liftoff Coupled Loads Analyses for the isolated CTC result in maximum net-load factors (including random) in the Xo, Yo and Zo directions of less than 3g s throughout both the ICC and LMC cargo manifest weight range Landing Coupled Loads Analyses for the isolated CTC result in maximum net-load factors in the Xo and Yo directions of less than 1.2 g s and Zo direction of 4.14 g s throughout both the ICC and LMC cargo manifest weight range 55
Conclusions - continued There is some coupling of the ICC and LMC platform Zo bending mode frequency and the CTC Zo isolation frequency (8 12 Hz depending on the cargo weight) and is mitigated by isolation system damping See Backup charts on stiff platform study Base-shake analysis for the sidewall mounted isolated CTC indicate similar reductions in CTC netload factors Coupled Loads Analyses for entire CTC weight range to be conducted in Phase II 56
Conclusions - continued OSS CTC design utilizing off the shelf robust Aeroflex wire rope isolators tuned to the 8-12 Hz region of the longeron dynamic environment significantly mitigates both transient and random vibrations while providing a stiff enough suspension to limit excessive relative motion ASD s Variational Coupled Loads Analysis capability can be utilized to determine the entire spectrum of response of the isolated CTC on other carriers such as the Express Pallet, ICC-V, ICC-L, and ULC 57
Back-up charts Zo Coupling with Stiff ICC Platform ICC Platform Stiffness artificially increased to force the isolated CTC / Integrated ICC frequencies to be better separated Landing Variational Coupled Loads Analysis re-conducted and results compared with nominal platform stiffness 58
CTC Zo Cargo Acceleration Spectrum Nominal Platform Stiffness ICC Landing VCLA 59
CTC Zo Cargo Acceleration Spectrum Increased Platform Stiffness ICC Landing VCLA 6