R.C. Singleterry Jr., G.D. Qualls, J.W. Wilson, F.M. Cheatwood, J.O.
Riggins
NASA Langley Research Center
K.Y. Fan, B.D. Johns M.S. Clowdsley
M.Y. Kim
Swales Aerospace NRC
College of William and Mary
S.L. Koontz, F.A. Cucinotta W. Atwell
S.A. Kayali
NASA JSC The Boeing Company
NASA JPL
F.F. Badavi
Christopher Newport University
The hazards of ionizing radiation in space continue to be a limiting factor in the design of spacecraft and habitats. Shielding against such hazards is an enabling technology in human and robotic exploration and development of space and it even adds to the mission costs. We are developing a web accessible system for radiation hazard evaluation during the spacecraft design process and its subsequent operation. The Framework for Analysis and Collaborative Engineering (FACE) is used to integrate mission trajectory, environmental models, spacecraft materials and geometry, system radiation response functions, and mission requirements for evaluation and optimization of shielding distribution and materials. This new tool will be called the Space Ionizing Radiation Environment and Shielding Tool (SIREST). Emphasis of the first version of SIREST in the Integrated Design System (IDS) [1] will address low Earth orbit allowing design system validation using STS, Mir, and ISS measurements. The second version will include Mars, the Moon, and other deep space mission analysis. It will also include the capability to perform shielding optimization including shield materials, mission sequence, and propulsion trade studies. The third version will include deep space probe design capability.
Optimal spacecraft design is an interdisciplinary, collaborative activity demanding input from mission scientists, spacecraft designers, engineers, technicians, and software and hardware specialists. For example, minimizing weight and maximizing performance demands that structural materials also function as efficient radiation shielding wherever possible. In the past, adding radiation shielding to a spacecraft design as an afterthought has led to substantial increases in cost and launch weight.
Many different computational tools are needed to help the designer and engineer create the appropriate spacecraft for the mission requirements. These tools must work together for the designer to create a fully optimized spacecraft. Therefore, a user and computational framework that enables collaborative engineering design must be created. The specific computational tools to be used in the framework are mission dependant, but all missions share certain common characteristics. The design will be generated in a Computer Aided Design (CAD) package. Collaboration between individuals located at distant sites and having different backgrounds is assumed. Before the spacecraft leaves the Earth’s surface, its ability to function in the expected mission environment must be verified by both test and analysis. Collaborative engineering enables a large part of the analytical verification process to be completed concurrently with spacecraft design. Many other items can be listed, but only radiation issues will be dealt with in this summary.
All issues of design collaboration and computational analysis must be resolved to fully analyze and optimize a potential space spacecraft. We concentrate on a tool and framework to determine the potential radiation fields inside and outside the spacecraft and to map those fields to damage estimates for humans, electronics, and materials. Once all the parameters of a spacecraft are optimized to the mission requirements, including the assessment and mitigation of radiation hazards, then the lowest spacecraft weight and cost as well as the highest reliability can be assured.
The IDS is an initiative by NASA to tie large engineering codes together in an easy-to-use Graphical User Interface (GUI). The team at NASA Langley Research Center developed a Computer Gateway Interface (CGI) based system to interface engineering codes. The FACE team uses Perl to integrate the system codes written in C/C++ and FORTRAN. The system is completely platform independent. There are core machines that are PC’s running Linux and SGI’s running Irix. The remote machines are PC's with Linux or Windows NT and SGI’s with Irix.
The development of spacecraft requires the use of several different codes to perform analysis on a single design. The development of a pre-Phase A design could take several weeks to get the data to the sub-system experts and perform the analysis required. The use of FACE allows a given module to reside with the expert or sponsor, and the novice or expert user to access it. Data can be stored and displayed from geographically remote locations, where only an Internet browser is required. The use of default inputs for each module assists the novice user in performing good analysis. The user selects a spacecraft that is similar to the one they want to test. The default inputs from the selected mission are used for further analysis. This selection allows the novice user to perform analysis without requiring an expert eye. An expert can be called in to verify the results after the run, saving time and talent.
FACE eliminates the need to port analysis codes to another system. Rather, each module resides on the host machine supplied by its sponsor. Using any Internet browser that is Netscape 1.1 compatible, a user can access the FACE system (Note: there are special features of FACE that require a newer browser with plug-ins, but these features are not required to perform analyses). Only the login screen of the web interface is static. All other web pages are automatically generated at run-time for each application from a text-based configuration file. The framework consists of: a password protected login page, an application page where all applications for the IDS system are displayed, input and output pages for each individual application, a review page where all results saved by the user are displayed, and batch capability for running codes that would otherwise timeout. Within IDS, the user may generate and save results, share data with other users, restart from a saved dataset, and remove unwanted results from the system.
A user-friendly tool that utilizes FACE and the LaRC shielding and space environment effects tools will enable the inclusion of shielding analysis in spacecraft design and operation. The SIREST collaborative tool will allow spacecraft designers to include radiation protection in their spacecraft optimizations, allow mission designers to perform trade studies on various parameters to reduce the radiation received by the crew, allow accurate prediction of expected radiation exposure for electronic devices and materials, and allow operations personnel to assess upcoming events with respect to the current radiation conditions. Astronaut training in the CAVE immersive models can be performed to familiarize them with the hot spots inside the spacecraft. This effort will entail merging proven legacy code and state-of-the-art immersive technology.
Please contact Robert C. Singleterry Jr. at the NASA Langley Research Center for any more information at (757) 864 1437 or r.c.singleterry@larc.nasa.gov.
[1] The original IDS is a design environment for planetary entry spacecraft. This consists of aerodynamics, transitional regime, thermal protection shielding design, and trajectory modules. Our near-term plans do not include integrating with these modules, but our far-term plans are to include them with others to enable a full design capability under IDS.