Goddard Space Flight Center

Goddard Space Flight Center was established in 1959, absorbing the U. S. Navy Vanguard satellite project and, with it, the mission of devel­oping, launching, and tracking unpiloted satellites. Since that time, its roles and responsibilities have expanded to consider space science, Earth observation from space, and unpiloted satellite systems more broadly.

Structural analysis problems studied at Goddard included definition of operating environments and loads applicable to vehicles, subsystems, and payloads; modeling and analysis of complete launch vehicle/payload sys­tems (generic and for specific planned missions); thermally induced loads and deformation; and problems associated with lightweight, deployable structures such as antennas. Control-structural interactions and multi­body dynamics are other related areas of interest.

Goddard’s greatest contribution to computer structural analysis was, of course, the NASTRAN program. With public release of NASTRAN, management responsibility shifted to Langley. However, Goddard remained extremely active in the early application of NASTRAN to practical problems, in the evaluation of NASTRAN, and in the ongoing improvement and addition of new capabilities to NASTRAN: thermal analysis (part of a larger Structural-Thermal-Optical [STOP] program, which is discussed below), hydroelastic analysis, automated cyclic sym­metry, and substructuring techniques, to name a few.[885]

Structural-Thermal-Optical analysis predicts the impact on the per­formance of a (typically satellite-based) sensor system due to the defor­mation of the sensors and their supporting structure(s) under thermal and mechanical loads. After NASTRAN was developed, a major effort began at GSFC to achieve better integration of the thermal and optical analysis components with NASTRAN as the structural analysis compo­nent. The first major product of this effort was the NASTRAN Thermal Analyzer. The program was based on NASTRAN and thereby inherited a great deal of modeling capability and flexibility. But, most impor­tantly, the resulting inputs and outputs were fully compatible with NASTRAN: "Prior to the existence of the NASTRAN Thermal Analyzer, available general purpose thermal analysis computer programs were designed on the basis of the lumped-node thermal balance method.

. . . They were not only limited in capacity but seriously handicapped by incompatibilities arising from the model representations [lumped – node versus finite-element]. The intermodal transfer of temperature data was found to necessitate extensive interpolation and extrapolation. This extra work proved not only a tedious and time-consuming process but also resulted in compromised solution accuracy. To minimize such an interface obstacle, the STOP project undertook the development of a general purpose finite-element heat transfer computer program.”[886] The capability was developed by the MacNeal Schwendler Corporation under subcontract from Bell Aerospace. "It must be stressed, however, that a cooperative financial and technical effort between [Goddard and Langley] made possible the emergence of this capability.”[887]

Another element of the STOP effort was the computation of "view factors” for radiation between elements: "In an in-house STOP proj­ect effort, GSFC has developed an IBM-360 program named ‘VIEW’ which computes the view factors and the required exchange coefficients between radiating boundary elements.”[888] VIEW was based on an ear­lier view factor program, RAVFAC, but was modified principally for compatibility with NASTRAN and eventual incorporation as a subrou­tine in NASTRAN.[889] STOP is still an important part of the analysis of many of the satellite packages that Goddard manages, and work contin­ues toward better performance with complex models, multidisciplinary design, and optimization capability, as well as analysis.