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The technical objectives are to develop high-performance, space-qualifiable, onboard computing, storage, and networking technologies. The topics are presented in viewgraph form and include the following: justification; technology challenges; program description; and state-of-the-art assessment.
The development of a test bed tank and system for evaluating cryogenic fluid management technologies in a simulated upper stage liquid hydrogen tank is covered. The tank is 10 ft long and is 10 ft in diameter, and is an ASME certified tank constructed of 5083 aluminum. The tank is insulated with a combination of sprayed on foam insulation, covered by 45 layers of double aluminized mylar separated by dacron net. The mylar is applied by a continuous wrap system adapted from commercial applications, and incorporates variable spacing between the mylar to provide more space between those layers having a high delta temperature, which minimizes heat leak. It also incorporates a unique venting system which uses fewer large holes in the mylar rather than the multitude of small holes used conventionally. This significantly reduces radiation heat transfer. The test bed consists of an existing vacuum chamber at MSFC, the test bed tank and its thermal control system, and a thermal shroud (which may be heated) surrounding the tank. Provisions are made in the tank and chamber for inclusion of a variety of cryogenic fluid management experiments.
Objectives of this research are as follows: to understand the three classes of superresolution and their behavior in optical data storage systems; to investigate new and improved components and techniques in the optical system for data detection and servo control; to apply micro-optic components to the optical system to reduce size and weight; to investigate techniques, such as near-field optical probes, for recording data densities beyond that possible with superresolution; and to understand and find solutions for problems associated with dynamic testing, especially those that arise when evaluating blue-sensitive media.
A synergistic hierarchy of analytical and computational fluid dynamic techniques is used to analyze three-dimensional combustion instabilities in liquid rocket engines. A mixed finite difference/spectral procedure is employed to study the effects of a distributed vaporization zone on standing and spinning instability modes within the chamber. Droplet atomization and vaporization are treated by a variety of classical models found in the literature. A multi-zone, linearized analytical solution is used to validate the accuracy of the numerical simulations at small amplitudes for a distributed vaporization region. This comparison indicates excellent amplitude and phase agreement under both stable and unstable operating conditions when amplitudes are small and proper grid resolution is used. As amplitudes get larger, expected nonlinearities are observed. The effect of liquid droplet temperature fluctuations was found to be of critical importance in driving the instabilities of the combustion chamber.
In recent years, avionics systems development costs have become the driving factor in the development of space systems, military aircraft, and commercial aircraft. A method of reducing avionics development costs is to utilize state-of-the-art software application generator (autocode) tools and methods. The recent maturity of application generator technology has the potential to dramatically reduce development costs by eliminating software development steps that have historically introduced errors and the need for re-work. Application generator tools have been demonstrated to be an effective method for autocoding non-redundant, relatively low-rate input/output (I/O) applications on the Space Station Freedom (SSF) program; however, they have not been demonstrated for fault tolerant, high-rate I/O, flight critical environments. This contract will evaluate the use of application generators in these harsh environments. Using Boeing's quad-redundant avionics system controller as the target system, Space Shuttle Guidance, Navigation, and Control (GN&C) software will be autocoded, tested, and evaluated in the Johnson (Space Center) Avionics Engineering Laboratory (JAEL). The response of the autocoded system will be shown to match the response of the existing Shuttle General Purpose Computers (GPC's), thereby demonstrating the viability of using autocode techniques in the development of future avionics systems.
The development of an experimental test-bed to investigate the integration and control of perception in a continuously operating vision system is described. The test-bed integrates a 12 axis robotic stereo camera head mounted on a mobile robot, dedicated computer boards for real-time image acquisition and processing, and a distributed system for image description. The architecture was designed to: (1) be continuously operating, (2) integrate software contributions from geographically dispersed laboratories, (3) integrate description of the environment with 2D measurements, 3D models, and recognition of objects, (4) capable of supporting diverse experiments in gaze control, visual servoing, navigation, and object surveillance, and (5) dynamically reconfiguarable.
A method for providing uniform transparent access to disparate distributed information systems was demonstrated. A prototype testing interface was developed to access documentation and information using publicly available hypermedia tools. The prototype gives testers a uniform, platform-independent user interface to on-line documentation, user manuals, and mission-specific test and operations data. Mosaic was the common user interface, and HTML (Hypertext Markup Language) provided hypertext capability.
A wheeled exploratory vehicle is under construction at the Mars Mission Research Center at North Carolina State University. In order to serve as more than an inspection tool, this vehicle requires the ability to interact with its surroundings. A crane-type manipulator, as well as the necessary control hardware and software, has been developed for use as a sample gathering tool on this vehicle. The system is controlled by a network of four Motorola M68HC11 microcontrollers. Control hardware and software were developed in a modular fashion so that the system can be used to test future control algorithms and hardware. Actuators include three stepper motors and one solenoid. Sensors include three optical encoders and one cable tensiometer. The vehicle supervisor computer provides the manipulator system with the approximate coordinates of the target object. This system maps the workspace surrounding the given location by lowering the claw, along a set of evenly spaced vertical lines, until contact occurs. Based on this measured height information and prior knowledge of the target object size, the system determines if the object exists in the searched area. The system can find and retrieve a 1.25 in. diameter by 1.25 in. tall cylinder placed within the 47.5 sq in search area in less than 12 minutes. This manipulator hardware may be used for future control algorithm verification and serves as a prototype for other manipulator hardware.
We propose to develop an on-line data distribution and interactive display system for the collection, archival, distribution and analysis of operational weather satellite data for applications in land surface studies. A 1,000 square km scene of the western U.S. (centered on the Colorado Rockies) will be extracted from Advanced Very High Resolution Radiometer (AVHRR) imagery collected from morning and afternoon passes of the NOAA polar-orbiters at the direct readout stations operated by CU/CCAR. All five channels of these AVHRR data will be navigated and map registered at CU/CCAR and then be transferred to NCAR for storage in an on-line data system. Software will also be available at NCAR to process and navigate the raw AVHRR data as needed. A display workstation software, based on a Macintosh II computer, will be developed that will display and further process the AVHRR data for studies of vegetation monitoring and snowpack assessment. Various options of presently used techniques for both vegetation and snowpack monitoring will be implemented in the workstation software to provide the individual investigator with the freedom to interact with the satellite image data. The display software will be freely distrributed online to interested investigators, and the AVHRR data will be made available on-line to anyone interested. In addition, potential users will be sought out and connected to the on-line data archive. This experiment with an active on-line archive and interactive analysis systems will provide experience with a small scale EOSDIS.
We were motivated to define and build a sophisticated satellite simulation capability for the evaluation at a satellite operations automated environment called IntelliSTAR. This architecture, and associated prototype, addresses the entire spacecraft operations cycle including planning, scheduling, task execution, and analysis. It is aimed at increasing the autonomous capability of current and future spacecraft. It utilizes advanced software techniques to address incomplete and conflicting data for making decisions. It also encompasses critical response time requirements, complex relationships among multiple systems, and dynamically changing objectives. Given the extreme scope of activities that are targeted, a sophisticated, flexible, and dynamic simulation environment was required to drive this prototype. In particular the derived requirements for evaluating the IntelliSTAR prototype include realistic and dynamic environment, easily reconfigurable, and multiple levels of fidelity.
Simulation of spacecraft battery operation is implemented. Robust design experiment to obtain optimum battery operational parameters is performed. It is found that short term tests using robust design of experiments can provide guidelines for optimum battery operation. It is decided to use robust design approach to provide guidelines for battery operation on current spacecraft in orbit as batteries age (GRO, UARS, EUVE, TOPEX).
An Integrated Agent Architecture (IAA) is a framework or paradigm for constructing intelligent agents. Intelligent agents are collections of sensors, computers, and effectors that interact with their environments in real time in goal-directed ways. Because of the complexity involved in designing intelligent agents, it has been found useful to approach the construction of agents with some organizing principle, theory, or paradigm that gives shape to the agent's components and structures their relationships. Given the wide variety of approaches being taken in the field, the question naturally arises: Is there a way to compare and evaluate these approaches? The purpose of the present work is to develop common benchmark tasks and evaluation metrics to which intelligent agents, including complex robotic agents, constructed using various architectural approaches can be subjected.
This document is Volume 3 of the final technical report on the work performed by SRI International (SRI) on SRI Project 8600. The document includes source listings for all software developed by SRI under this effort. Since some of our work involved the use of ST-II and the Sun Microsystems, Inc. (Sun) High-Speed Serial Interface (HSI/S) driver, we have included some of the source developed by LBL and BBN as well. In most cases, our decision to include source developed by other contractors depended on whether it was necessary to modify the original code. If we have modified the software in any way, it is included in this document. In the case of the Traffic Generator (TG), however, we have included all the ST-II software, even though BBN performed the integration, because the ST-II software is part of the standard TG release. It is important to note that all the code developed by other contractors is in the public domain, so that all software developed under this effort can be re-created from the source included here.
DARTnet provides an excellent environment for executing networking experiments. Since the network is private and spans the continental United States, it gives researchers a great opportunity to test network behavior under controlled conditions. However, this opportunity is not available very often, and therefore a support environment for such testing is lacking. To help remedy this situation, part of SRI's effort in this project was devoted to advancing the state of the art in the techniques used for benchmarking network performance. The second objective of SRI's effort in this project was to advance networking technology in the area of traffic control, and to test our ideas on DARTnet, using the tools we developed to improve benchmarking networks. Networks are becoming more common and are being used by more and more people. The applications, such as multimedia conferencing and distributed simulations, are also placing greater demand on the resources the networks provide. Hence, new mechanisms for traffic control must be created to enable their networks to serve the needs of their users. SRI's objective, therefore, was to investigate a new queueing and scheduling approach that will help to meet the needs of a large, diverse user population in a "fair" way.
The Space Science and Engineering Center (SSEC) of the University of Wisconsin - Madison had two primary goals for NASA grant NAG5-2906. (1) Collaborate with scientists at NASA Goddard Space Flight Center (GSFC) to integrate SSEC's Vis5D software into NASA's Interactive Image Spread Sheet (IISS). Vis5D provides environmental modelers with interactive three-dimensional visualization of their model output. Integration of Vis5D with the IISS would give 3-D graphics capability to the iiss. (2) Make improvements in Vis5D as required by scientists at the NASA Data Assimilation Office (DAO). We were successful in both of these goals. Furthermore, the generic approach taken to achieving the first goal has enabled Vis5D to be integrated into many other software systems.
One of the challenges in the area of cryogenics for space exploration in the next millennium is providing the capability for inexpensive, frequent, access to space. Faced with this challenge during the International Space Station (ISS) build era, when other Space Shuttle manifesting opportunities are unavailable, a "proof of concept" cryostat has been developed to demonstrate the ability to accommodate low temperature science investigations within the constraints of the Hitchhiker siderail carrier. The Hitchhiker siderail carrier is available on a "mass available" basis during the ISS build era. In fact, several hitchhiker payloads flew with the deployment of the Unity module. Hitchhiker siderail carrier payloads have historically flown an average of about four times a year. A hybrid Solid Neon - Superfluid Helium cryostat has been developed with Janis Research Company to accommodate instruments of 16.5 cm diameter and 30 cm. length. This hybrid approach was taken in part to provide adequate on-orbit lifetime for instruments with high (conducted) heat loads from the instrumentation wiring. Mass, volume, lifetime and the launch hold scenario were all design drivers. In addition, with Ball Aerospace and Technologies Corporation, a multichannel VME architecture Germanium Resistance Thermometer (GRT) readout and heater control servo system has been developed. In a flight system, the cryostat and electronics payloads would be umbilically attached in a paired Hitchhiker siderail mount, and permit on-orbit command and telemetry capability. The results of performance tests of both the cryostat, and a helium sample instrument will be presented. The instrument features a self contained, miniaturized, nano-Kelvin resolution High Resolution Thermometer (HRT). This high level of thermal resolution is achieved through the utilization of a dc Superconducting Quantum Interference Device (SQUID). Although developed for the Low Temperature Microgravity Fundamental Physics investigator community, many design features are applicable in fields such as infrared and x-ray astronomy.
The Formation Flying Test Bed (FFTB) at NASA Goddard Space Flight Center (GSFC) is being developed as a modular, hybrid dynamic simulation facility employed for end-to-end guidance, navigation, and control (GN&C) analysis and design for formation flying clusters and constellations of satellites. The FFTB will support critical hardware and software technology development to enable current and future missions for NASA, other government agencies, and external customers for a wide range of missions, particularly those involving distributed spacecraft operations. The initial capabilities of the FFTB are based upon an integration of high fidelity hardware and software simulation, emulation, and test platforms developed at GSFC in recent years; including a high-fidelity GPS simulator which has been a fundamental component of the Guidance, Navigation, and Control Center's GPS Test Facility. The FFTB will be continuously evolving over the next several years from a too[ with initial capabilities in GPS navigation hardware/software- in-the- loop analysis and closed loop GPS-based orbit control algorithm assessment to one with cross-link communications and relative navigation analysis and simulation capability. Eventually the FFT13 will provide full capability to support all aspects of multi-sensor, absolute and relative position determination and control, in all (attitude and orbit) degrees of freedom, as well as information management for satellite clusters and constellations. In this paper we focus on the architecture for the FFT13 as a general GN&C analysis environment for the spacecraft formation flying community inside and outside of NASA GSFC and we briefly reference some current and future activities which will drive the requirements and development.
Our mission is to bring together the mutual elements of research, industry, and training in the field of cryogenics to advance technology development for the spaceports of the future. Successful technology and productive collaboration comes from these three ingredients working together in a triangle of interaction.