Under the direction of the NASA In-Space Propulsion Technology Office, the team of L'Garde, NASA Jet Propulsion Laboratory, Ball Aerospace, and NASA Langley Research Center has been developing a scalable solar sail configuration to address NASA's future space propulsion needs. Prior to a flight experiment of a full-scale solar sail, a comprehensive phased test plan is currently being implemented to advance the technology readiness level of the solar sail design. These tests consist of solar sail component, subsystem, and sub-scale system ground tests that simulate the vacuum and thermal conditions of the space environment. Recently, two solar sail test articles, a 7.4-m beam assembly subsystem test article and a 10-m four-quadrant solar sail system test article, were tested in vacuum conditions with a gravity-offload system to mitigate the effects of gravity. This paper presents the structural analyses simulating the ground tests and the correlation of the analyses with the test results. For programmatic risk reduction, a two-prong analysis approach was undertaken in which two separate teams independently developed computational models of the solar sail test articles using the finite element analysis software packages: NEiNastran and ABAQUS. This paper compares the pre-test and post-test analysis predictions from both software packages with the test data including load-deflection curves from static load tests, and vibration frequencies and mode shapes from vibration tests. The analysis predictions were in reasonable agreement with the test data. Factors that precluded better correlation of the analyses and the tests were uncertainties in the material properties, test conditions, and modeling assumptions used in the analyses.

Under the direction of the NASA In-Space Propulsion Technology Office, the team of L'Garde, NASA Jet Propulsion Laboratory, Ball Aerospace, and NASA Langley Research Center has been developing a scalable solar sail configuration to address NASA's future space propulsion needs. Prior to a flight experiment of a full-scale solar sail, a comprehensive phased test plan is currently being implemented to advance the technology readiness level of the solar sail design. These tests consist of solar sail component, subsystem, and sub-scale system ground tests that simulate the vacuum and thermal conditions of the space environment. Recently, two solar sail test articles, a 7.4-m beam assembly subsystem test article and a 10-m four-quadrant solar sail system test article, were tested in vacuum conditions with a gravity-offload system to mitigate the effects of gravity. This paper presents the structural analyses simulating the ground tests and the correlation of the analyses with the test results. For programmatic risk reduction, a two-prong analysis approach was undertaken in which two separate teams independently developed computational models of the solar sail test articles using the finite element analysis software packages: NEiNastran and ABAQUS. This paper compares the pre-test and post-test analysis predictions from both software packages with the test data including load-deflection curves from static load tests, and vibration frequencies and mode shapes from structural dynamics tests. The analysis predictions were in reasonable agreement with the test data. Factors that precluded better correlation of the analyses and the tests were uncertainties in the material properties, test conditions, and modeling assumptions used in the analyses.

Space structures are subject to thermal and mechanical loads. Matrix cracks can form in composite components, which results in a change in their thermal and elastic properties. The objective of this study is to develop a method to predict transverse microcracking in general composite laminates subject to thermal and mechanical loads. The approach combines probabilistic and analytical components in an incremental damage method. The probabilistic components include a distribution of flaws characterized by a Weibull probability function, seeding of flaws at random locations, inspection of flaws in random order for crack initiation, and inspection of cracks in random order for extension. The analytical components include fracture mechanics based energy criteria that uses a shear lag derivation of the stress and displacement fields. Degradation of material properties, temperature-dependent material properties, and a material variations model are incorporated into the method. This method is implemented through a computer program that predicts crack densities, crack distributions, and degraded laminate properties as functions of an arbitrary thermomechanical load profile. Parametric analyses are used to understand the behaviors predicted by the method and their sensitivities to model parameters. Predictions are compared to previously collected data and observations for different laminate configurations and material systems. For both thermal and mechanical loads, crack density predictions capture general trends and agree with much of the data. The method shows improvements on the current state of the art in several areas. The effective flaw model predicts the initiation and gradual accumulation of cracks. The material variations model allows the method to emulate the intrinsic variability of the crack data. The method predicts crack distributions and their evolution as cracking progresses. This evolution can include the formation of different crack types and patterns. The effect of ply thickness on this evolution is correctly predicted. The success of the method shows its superiority as a tool for predicting cracking. By replicating complex observed behavior using a relatively simple method, the work supports the physical soundness of the method and increases our understanding of the mechanisms of microcracking in composite laminates.

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