John Schiermeier

Multidisciplinary analysis for large-scale optical design

Accurately predicting optical performance for any of the near-term concepts proposed under NASAs Origins missions is a uniquely challenging task, and one that has served to highlight a number of areas of necessary advancement in the field of computer-aided engineering analysis. The strongly coupled nature of these classes of problems combined with unprecedented levels of required optical precision demand a solution approach that is itself fundamentally integrated if accurate, efficient analyses, capable of pointing the way towards improved designs are to be achieved. Recent development efforts have served to lay the foundation for an entirely new finite element-based analytical capability; one that is open, highly extensible, is Matlab-hosted, and which utilizes NASTRAN syntax to describe common-model multidisciplinary analyis tasks. Capabilities currently under development, a few of which will be highlighted here, will soon capture behavioural aspects of coupled nonlinear radiative heat transfer, structures, and optics problems to a level of accuracy and performance not yet achieved for these classes of problems, in an environment that will greatly facilitate future research, development, and technical oversight efforts.

Multiphysics modeling and uncertainty quantification for an active composite reflector

A multiphysics, high resolution simulation of an actively controlled, composite reflector panel is developed to extrapolate from ground test results to flight performance. The subject test article has previously demonstrated sub-micron corrected shape in a controlled laboratory thermal load. This paper develops a model of the on-orbit performance of the panel under realistic thermal loads, with an active heater control system, and performs an uncertainty quantification of the predicted response. The primary contribution of this paper is the first reported application of the Sandia developed Sierra mechanics simulation tools to a spacecraft multiphysics simulation of a closed-loop system, including uncertainty quantification. The simulation was developed so as to have sufficient resolution to capture the residual panel shape error that remains after the thermal and mechanical control loops are closed. An uncertainty quantification analysis was performed to assess the predicted tolerance in the closed-loop wavefront error. Key tools used for the uncertainty quantification are also described.

A thermo/opto/mechanical testbed validation using Cielo

Due to their scale, operating environment, and required levels of operating precision, the design of the next generation of space-based observatories will necessarily place an ever-greater reliance on numerical simulation. Since it will be impossible to fully ground-test such systems prior to flight, system-level confidence must come, in large part, from correlated subsystem tests, system-level simulation, and an overall design understanding based on quantification of margins of uncertainty, sensitivity analyses, parameter variation studies, and design optimization. Further challenges will necessarily arise due to the actively-controlled nature of such systems, requiring fundamentally-integrated thermal, structural, optical, and controls models. In this paper we will discuss Cielo, JPLs multidisciplinary, high-capability compute platform for systems analysis, and describe some of the challenges in demonstrating these capabilities for the first time on a complex model, the Space Interferometry Missions Thermal-Structural-Optical (SIM-TOM3) testbed. The successes and lessons learned from these activities have the potential to greatly influence subsequent test programs, leading to greater design understanding, improved mission confidence, and significant cost and schedule reductions.