AMS-02 Structural Analysis Overview: Design Loads & Fracture Control

1. AMS-02 Structural Analysis Overview Carl Lauritzen Jacobs Engineering May 22, 2007 AMS-02 Phase 2 Flight Safety Review

2. Introduction • Structural Analysis Requirements • Structural Analysis Approach • Design Loads • Math Models • Shuttle Cargo Compatibility Assessment • Loads Analysis • Stress Analysis • Fracture Analysis AMS-02 Phase 2 Flight Safety Review

3. Structural Analysis Requirements • Space Shuttle Program strength and frequency • NSTS-14046 Rev. E, “Payload verification Requirements” • NSTS-37329B, “Structural Integration Analyses Responsibility Definition for Space Shuttle Vehicle and Cargo Element Developers” • NSTS-1700.7B, “Safety Policy and Requirements for Payloads Using the Space Transportation System” • International Space Station strength and frequency • SSP-57003, “Attached Payload Interface Requirements Document” • NSTS-21000-IDD-ISS, “International Space Station Interface Definition Document” • NSTS-1700.7B, “Safety Policy and Requirements for Payloads Using the International Space Station” • SSP-52005, Rev. C, “ISS Payload Flight Equipment Requirements and Guidelines for Safety Critical Structures” • Fracture Control • JSC-25863, Rev. A, “Fracture Control Plan for JSC Flight Hardware” • NASA-STD-5003, “Fracture Control Requirements for Payloads Using the Space Shuttle” • SSP-30558C, “Fracture Control Requirements for Space Station” • Fastener Analysis • NSTS-08307A, “Criteria for Preloaded Bolts” • Alpha Magnetic Spectrometer (AMS-02) Project • JSC-28792, Rev. E, “AMS-02 Structural Verification Plan for the Space Transportation System and the International Space Station” • Reviewed by AMS-02 Configuration Control Board • Approved by the NASA Structures Working Group and NASA OB ISS Structures Team AMS-02 Phase 2 Flight Safety Review

4. Structural Analysis Approach for AMS-02 • A finite element model (FEM) of the full payload has been used to characterize the overall structural behavior of the system. • The large AMS-02 component are modeled explicitly in the full payload model with detailed structural representations • Structural analyses of these components are performed using stand-alone models of the component using load conditions derived from the full payload model. • Smaller components that are not affected by the global response of the structure are represented as a rigid body with the appropriate mass and center of gravity. • Structural analyses of these smaller components are performed using stand-alone models of the component with load factors AMS-02 Phase 2 Flight Safety Review

5. Design Loads for AMS-02 Primary Structure • Primary structure is defined as the structure that provides the primary load path for the entire payload • Design load factors were generated using Space Shuttle math models and launch/landing load cases • Derived from a design coupled loads analysis (DCLA) • Dynamic analysis that represents excitations and responses as a function of time • Performed in 1999 using preliminary math models of the payload • Performed for a generic manifest configuration • An uncertainty factor of 1.5 was included in the resulting load factor • These load factors have been approved by the NASA Structures Working Group • These load factors were used in nonlinear, static analyses with a math model of the full payload to derive internal loads for detailed design and stress analyses of the USS, vacuum case, and the magnet support system. AMS-02 Phase 2 Flight Safety Review

6. Design Loads for AMS-02 Mated Configuration on ISS • Primary structure design loads for ISS attached payloads(defined in SSP 57003 Rev A, Table 3.1.1.2.3-2 ) • Represent worst case loads due to berthing and ISS re-boost events • These interface loads were used to design the AMS-02 payload attach system (PAS) AMS-02 Phase 2 Flight Safety Review

7. Design Loads for Large AMS-02 Components • As part of an effort to reduce the weight of the payload, less conservative load factors were developed for some of the large components of the payload • Performed a second Design Coupled Loads Analysis (2003) • Used updated math models of the AMS-02 payload • Incorporated the nonlinear effects of the magnet support straps • Used updated Shuttle math models and forcing functions from Boeing • Used math models for the cargo elements associated with UF-4 flight • These load factors include an uncertainty factor of 1.25 • These load factors have been approved by the NASA Structures Working Group • These load factors were used in combination with component interface displacements to design and assess the large payload components not considered primary structure (radiators, RICH, upper and lower TOF, and the TRD) AMS-02 Phase 2 Flight Safety Review

8. Design Loads for AMS-02 Secondary Structure • Design load factors for AMS-02 secondary structure • Secondary structure is defined as components that are not part of the primary load path and can be treated as independent entities for analysis purposes • Components weighing less than 500 pounds use “simplified design” load factors (“Simplified Design Options for STS Payloads”, JSC-20545A, April 1988). • The factors are applied simultaneous in three axes directions • 100% of load factor is applied in primary axis direction • 25% of load factor is applied in remaining two orthogonal axes AMS-02 Phase 2 Flight Safety Review

9. Acoustic Design Loads for AMS-02 • Experiment components with large panels were assessed for acoustic loads • Responses computed using the Statistical Energy Analysis method(VAPEPS and AutoSEA software) • The total component load is determined by combining the static design load factor with the specified acoustic load factor AMS-02 Phase 2 Flight Safety Review

10. Additional Design Loads for AMS-02 • Magnet forces and eddy current induced loads • Assessment has shown that these only critical for the magnet structure. • EVA related loads for all external items that have potential EVA access • Crew kick loads, hand hold loads, crew-actuated tool loads • Shuttle RMS and Space Station RMS grapple fixture loads • Orbiter emergency landing loads • Defined in NSTS-21000-IDD-ISS • Bounded by primary structure design load factors • Quasi-static load conditions for Shuttle ascent and Orbiter entry • Defined in NSTS-37329 • Consists of 2064 deflection cases from mechanical, thermal, and pressure loading conditions • Helium slosh loads are combined with the helium tank design load factors for contingency landing cases • Ground and air transportation loads • Ground handling loads AMS-02 Phase 2 Flight Safety Review

11. Math Model for AMS-02 Loads Analysis • Math models are based on CAD models and drawings from designers • High level of fidelity for all major components • USS and vacuum case • Magnet, helium tank • Selected experiments (upper/lower TOF, TRD, TRD gas supply, ECAL, radiators, RICH) • Nonstructural items that are relatively rigid are modeled as lumped masses (e.g., electronic boxes) • Nonstructural items that have a low stiffness are modeled as distributed mass (cables, pipes, etc) • Model mass properties reflect current assessment from all component developers • Current loads model for the full payload is in excess of 500,000 DOF • Nonlinear model of magnet support straps • Modeled using tension-only elements with a defined stress-strain relationship • Stress-strain relationship in math model is based on physical force-displacements for each strap configuration • Stress-strain relationship accounts for temperature conditions (cryogenic environment vs. room temperature) AMS-02 Phase 2 Flight Safety Review

12. AMS-02 Finite Element Loads Model AMS-02 Phase 2 Flight Safety Review

13. Y X AMS-02 Finite Element Loads Model AMS-02 Phase 2 Flight Safety Review

14. Magnet Support Strap Representation for Loads Model • Warm strap model used for assessment of configurations that assume helium tank is empty • 1-D strap test, STA sine sweep test, modal test, and static test • Cold strap model used for assessment of configurations that assume helium tank is full • Liftoff and abort landing AMS-02 Phase 2 Flight Safety Review

15. Compatibility Assessment for Shuttle Cargo Integration • Primary trunnion: xo 1163.40, Stabilizer trunnion: xo 1242.07, Keel trunnion: xo 1175.20 • Satisfies ROEU compatibility requirements — extension to be made 6.07 inches longer • AMS-02 interface loads are within the Orbiter attach point capability • Clearances with ISS payload envelope and Orbiter hardware have undergone preliminary assessment AMS-02 Phase 2 Flight Safety Review

16. AMS-02 Orbiter Clearance Assessment • Clearance assessment performed by Boeing engineers in 2003(“AMS-02 and Orbiter Payload Bay Static and Dynamic Clearance Assessment” by Karen Bellard, Gilmar Gonzalez, and Charles Hethcoat of Boeing, April 29, 2003) • AMS-02 cargo bay location based on ROEU compatibility assessment by Gilmar Gonzalez, Boeing • Assumptions for dynamic clearance assessment • Manufacturing tolerance of 0.1 inch • Thermal growth of 0.5 inch • Relative dynamic motion of 3.0 inch at all locations except scuff plates • All items show “acceptable clearance” except for PAS guide pins which show “close clearance” • Dynamic clearance will be reassessed when displacement data is available from dynamic analyses AMS-02 Phase 2 Flight Safety Review

17. AMS-02 Structural Analyses • Primary analyses • Nonlinear static for loads generation and strength assessment (FEA, hand calculations) • Nonlinear transient for loads generation (FEA) • Quasi-static loads analysis for deflection and clearance assessment (FEA) • Buckling analysis for vacuum case and helium tank design verification (FEA) • AMS-02 load factors are obtained using results from nonlinear Design Coupled Loads Analysis (DCLA) • Design cycle load factors include an uncertainty factor of 1.25 and have been coordinated with the Structures Working Group (SWG) and ISS Structures Team • Modal analysis of nonlinear, preloaded model (FEA) • Assess frequency requirements for components and full payload • Dynamic correlation of payload model • Acoustic analysis of components with large honeycomb panels (statistical energy analysis) • Fracture mechanics and fatigue crack-growth analyses (NASGRO) • Fastener analysis(per NSTS-08307) AMS-02 Phase 2 Flight Safety Review

18. Stress Analysis Overview • Stress analysis of all components are performed per JSC-28792 (AMS-02 Structural Verification Plan) • Appropriate Factors of Safety have been used as presented in Appendix A of JSC-28792 (AMS-02 Structural Verification Plan) • For combined loading conditions, interaction formulas are used based on stress ratios for each loading condition • Material properties for metallic materials are taken from MIL-HDBK-5H and temperature reduction factors are applied, if required • Fitting factors, joint separation factors, and uncertainty factors are used for fastener analysis • Margins of safety for all structural components are greater than zero for all combined load conditions • An exception is a non-failure condition for joint separation • A detailed margin of safety summary is provided in the Hazard Report AMS-02-F01 AMS-02 Phase 2 Flight Safety Review

19. Fracture Control Assessment • Fracture control requirements of the AMS-02 payload components have been established in accordance with Space Shuttle and International Space Station requirements • The objective is to ensure safety of the crew, Orbiter, and ISS such that failure of any structure will not result in a catastrophichazard • Combined fatigue loading spectrum have been used for fracture analysis • Spectrum includes air transport, truck transport, launch/landing, and on-orbit loading events • STA vacuum case (flight backup) also includes sine sweep testand acoustic test spectrums • Scatter factor of 4 is used for design safe life analysis • The flight hardware has been reviewed and the fracture critical components have been identified. • Appropriate inspections, analyses, and controls have been implemented • A detailed summary of the fracture classification for the payload components is provided in Hazard Report AMS-02-F01. AMS-02 Phase 2 Flight Safety Review

20. Fracture Critical Components • Safe-life analysis is performed using the NASGRO program • Size of flaw used in the analysis is based on the appropriate NDE techniques or on proof testing • All fracture critical components will be NDE inspected per standard aerospace quality procedures (as referenced in JSC-25863, Rev. A) • Composite materials will be classified “low risk” per the specifications of section 5.2 d of the Fracture Control Plan (JSC 25863, Rev. A) AMS-02 Phase 2 Flight Safety Review

21. Pressurized Components • Composite over-wrapped pressure vessels (COPV) follow the guidelines of ANSI/AIAA S-081 • Stainless steel pressure vessels  follow the guidelines of ANSI/AIAA S-080 • Designed to have a non-hazardous leak-before-burst (LBB) mode of failure • Cracks through the thickness with a length 10 times the wall thickness will not result in unstable fracture • Components, lines, and fittings comply with burst and proof factors of safety as defined in NSTS 1700.7B and the ISS Addendum • Minor exceptions to this will be discussed in more detail in a separate presentation on the pressurized components. AMS-02 Phase 2 Flight Safety Review

22. Conclusion • An approved plan is in place to satisfy all structural analysis requirements for the AMS-02 payload • There are no significant open issues related to structural analysis. AMS-02 Phase 2 Flight Safety Review