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On April 5, 1990, after release from a B-52 aircraft at 43,198 ft, the three-stage Pegasus solid-propellant rocket successfully completed its maiden flight by injecting its 423-lb payload into a 273 x 370-nmi 94-deg-inclination orbit. The first flight successfully achieved all mission objectives, validating Pegasus's unique air-launched concept, the vehicle's design, and its straightforward ground processing, integration and test methods.
The Topex/Poseidon Project is a joint U.S. and French mission to develop and operate an earth-orbiting satellite with sensors capable of making accurate measurements of sea level. The NASA Radar Altimeter (NRA), a fifth-generation U.S. altimeter, will provide the primary measurement for the Topex/Poseidon altimetric mission. This paper presents the requirements, altimeter fundamentals, design description, integration and test program, primary elements of ground processing, and assessment for the dual-frequency NRA.
Microelectronic advanced laser scanner (MEALS) is opto/electro/mechanical apparatus for nondestructive testing of integrated memory circuits, logic circuits, and other microelectronic devices. Multipurpose diagnostic system used to determine ultrafast time response, leakage, latchup, and electrical overstress. Used to simulate some of effects of heavy ions accelerated to high energies to determine susceptibility of digital device to single-event upsets.
A set of procedural and functional requirements are presented for the interface between software development environments and software integration and test systems used for space station ground systems software. The requirements focus on the need for centralized configuration management of software as it is transitioned from development to formal, target based testing. This concludes the GSDE Interface Requirements study. A summary is presented of findings concerning the interface itself, possible interface and prototyping directions for further study, and results of the investigation of the Cronus distributed applications environment.
The Advanced Modulation and Coding Project at LeRC is sponsored by the Office of Space Science and Applications, Communications Division, Code EC, at NASA Headquarters and conducted by the Digital Systems Technology Branch of the Space Electronics Division. Advanced Modulation and Coding is one of three focused technology development projects within the branch's overall Processing and Switching Program. The program consists of industry contracts for developing proof-of-concept (POC) and demonstration model hardware, university grants for analyzing advanced techniques, and in-house integration and testing of performance verification and systems evaluation. The Advanced Modulation and Coding Project is broken into five elements: (1) bandwidth- and power-efficient modems; (2) high-speed codecs; (3) digital modems; (4) multichannel demodulators; and (5) very high-data-rate modems. At least one contract and one grant were awarded for each element.
This report presents a review of the software configuration management (CM) plans developed for the Space Station Training Facility (SSTF) and the Space Station Control Center. The scope of the CM assessed in this report is the Systems Integration and Testing Phase of the Ground Systems development life cycle. This is the period following coding and unit test and preceding delivery to operational use. This report is one of a series from a study of the interfaces among the Ground Systems Development Environment (GSDE), the development systems for the SSTF and the SSCC, and the target systems for SSCC and SSTF. This is the last report in the series. The focus of this report is on the CM plans developed by the contractors for the Mission Systems Contract (MSC) and the Training Systems Contract (TSC). CM requirements are summarized and described in terms of operational software development. The software workflows proposed in the TSC and MSC plans are reviewed in this context, and evaluated against the CM requirements defined in earlier study reports. Recommendations are made to improve the effectiveness of CM while minimizing its impact on the developers.
The goal of the completed project was to develop an experiment in remote manufacturing that would use the capabilities of the ACTS satellite. A set of possible experiments that could be performed using the Advanced Communications Technology Satellite (ACTS), and which would perform remote manufacturing using a laser cutter and an integrated circuit testing machine are described in detail. The proposed design is shown to be a feasible solution to the offered problem and it takes into consideration the constraints that were placed on the experiment. In addition, we have developed two more experiments that are included in this report: backup of rural telecommunication networks, and remote use of Synthetic Aperture Radar (SAR) data analysis for on-site collection of glacier scattering data in the Antarctic.
Three-dimensional, elastic-plastic, finite-element results are presented for single-edge crack-tension specimens with several shallow crack-length-to-width ratios (0.05 less than or equal to a/W less than or equal to 0.5). Results showed the need to model the initial yield plateau in the stress-strain behavior to accurately model deformation of the A36 steel specimens. The crack-tip-opening-displacement was found to be linearly proportional to the crack-mouth-opening displacement. A new deformation dependent plastic-eta factor equation is presented for calculating the J-integral from test load-displacement records. This equation was shown to be accurate for all crack lengths considered.
The development and operations costs of the Space IR Telescope Facility (SIRTF) are discussed in the light of minimizing total outlays and optimizing efficiency. The development phase cannot extend into the post-launch segment which is planned to only support system verification and calibration followed by operations with a 70-percent efficiency goal. The importance of reducing the ground-support staff is demonstrated, and the value of the highly sensitive observations to the general astronomical community is described. The Failure Protection Algorithm for the SIRTF is designed for the 5-yr lifetime and the continuous venting of cryogen, and a science driven ground/operations system is described. Attention is given to balancing cost and performance, prototyping during the development phase, incremental development, the utilization of standards, and the integration of ground system/operations with flight system integration and test.
The usual method of evaluating flight performance during a simulation is to collect as many primary performance measurements as possible. Then analyze all the measurements to find one sensitive to the manipulations imposed on the pilot during the scenario. Although this method can be useful, it is usually unreliable from one study to another. A simulation was conducted to test an integrated figure of merit (FOM) constructed using a standardized procedure. Pilots flew two full-mission scenarios in an instrument trainer with three degrees of motion freedom. The primary performance measurements selected assessed the pilot's performance in accuracy, smoothness, and activity. The results suggest that the integrated FOMs performed comparably to the primary performance measurements in determining which flight imposed the higher demands on the pilot. The standardized construction process allow adjustments to the FOM, so it can be used in different applications.
An innovative approach to fault management was recently demonstrated for the NASA LeRC Space Station Freedom (SSF) power system testbed. This project capitalized on research in model-based reasoning, which uses knowledge of a system's behavior to monitor its health. The fault management system (FMS) can isolate failures online, or in a post analysis mode, and requires no knowledge of failure symptoms to perform its diagnostics. An in-house tool called MARPLE was used to develop and run the FMS. MARPLE's capabilities are similar to those available from commercial expert system shells, although MARPLE is designed to build model-based as opposed to rule-based systems. These capabilities include functions for capturing behavioral knowledge, a reasoning engine that implements a model-based technique known as constraint suspension, and a tool for quickly generating new user interfaces. The prototype produced by applying MARPLE to SSF not only demonstrated that model-based reasoning is a valuable diagnostic approach, but it also suggested several new applications of MARPLE, including an integration and testing aid, and a complement to state estimation.
The validation and verification of large deployable space structures are continual challenges which face the integration and test engineer today. Spar Aerospace Limited has worked on various programs in which such structure validation was required and faces similar tasks in the future. This testing is reported and the different offloading and deployment methods which were used, as well as the proposed methods which will be used on future programs, are described. Past programs discussed include the Olympus solar array ambient and thermal vacuum deployments, and the Anik-E array and reflector deployments. The proposed MSAT reflector and boom ambient deployment tests, as well as the proposed RADARSAT Synthetic Aperture Radar (SAR) ambient and thermal vacuum deployment tests will also be presented. A series of tests relating to various component parts of the offloading equipment systems was required. These tests included the characterization and understanding of linear bearings and large (180 in-lbf) constant force spring motors in a thermal vacuum environment, and the results from these tests are presented.
The goal of this study was to evaluate and make recommendations for improving the level of integration of several work groups within the Materials and Processes Lab at the Marshall Space Flight Center. This evaluation has uncovered a variety of projects that could improve the efficiency and operation of the work groups as well as the overall integration of the system. In addition, this study provides the foundation for specification of a computer integrated manufacturing test bed environment in the Materials and Processes Lab.
The topics are presented in viewgraph form and include the following: an instrument and changes overview; mechanical requirements; thermal requirements; electrical command and data handling; contamination; software; integration and test; and environmental requirements assessments.
Viewgraphs on SPE electrolyzers for space propulsion are presented. Topics covered include: SPE electrochemical cell reactions; SPE fuel cell/electrolyzer features; SPE cell life capability; SPE cell voltage stability; state-of-the-art SPE cell structure; electrolysis cell stack; electrolysis system; integrated propulsion test article-electrolyzer module components; and oxygen generator module.
Satellites and long-life spacecraft require effective contamination control measures to ensure data accuracy and maintain overall system performance margins. Satellite and spacecraft contamination can occur from either molecular or particulate matter. Some of the sources of the molecular species are as follows: mass loss from nonmetallic materials; venting of confined spacecraft or experiment volumes; exhaust effluents from attitude control systems; integration and test activities; and improper cleaning of surfaces. Some of the sources of particulates are as follows: leaks or purges which condense upon vacuum exposure; abrasion of movable surfaces; and micrometeoroid impacts. The Environmental Verification Experiment for the Explorer Platform (EVEEP) was designed to investigate the following aspects of spacecraft contamination control: materials selection; contamination modeling of existing designs; and thermal vacuum testing of a spacecraft with contamination monitors.
Teleoperated robots require one or more humans to control actuators, mechanisms, and other robot equipment given feedback from onboard sensors. To accomplish this task, the human or humans require some form of control station. Desirable features of such a control station include operation by a single human, comfort, and natural human interfaces (visual, audio, motion, tactile, etc.). These interfaces should work to maximize performance of the human/robot system by streamlining the link between human brain and robot equipment. This paper describes development of a control station testbed with the characteristics described above. Initially, this testbed will be used to control two teleoperated robots. Features of the robots include anthropomorphic mechanisms, slaving to the testbed, and delivery of sensory feedback to the testbed. The testbed will make use of technologies such as helmet mounted displays, voice recognition, and exoskeleton masters. It will allow tor integration and testing of emerging telepresence technologies along with techniques for coping with control link time delays. Systems developed from this testbed could be applied to ground control of space based robots. During man-tended operations, the Space Station Freedom may benefit from ground control of IVA or EVA robots with science or maintenance tasks. Planetary exploration may also find advanced teleoperation systems to be very useful.
In response to the initiatives to streamline, not to mention comply with the Public Law for Non-Developmental Item Preference, the Department of Defense (DOD) has increased its use of commercial products. The Air Force has, over the past 15 years, been adapting Federal Aviation Administration (FAA) certified aircraft to perform many of its airlift and training missions. Counting the T-1A Jayhawk Trainer (Beechjet 400), in excess of 500 total aircraft, covering 15 different types, will have been procured since 1978. Needless to say, significant reform of the "classical" DOD and Air Force way of doing business has been necessary. Major strides have been made by the Transport Directorate of the Aircraft Program Office in the area of test and evaluation, with integrated qualification and operational testing (QT &E/QOT &E) and airworthiness certification testing by the FAA. As well, significant changes in contracting practices and the use of commercial (vice military) specifications for qualification criteria have been realized. This paper will relate some of these significant strides in "commercializing" and streamlining the DOD acquisition and test and evaluation processes. Additionally, it will review both regulatory changes made and recommended. It concludes with a compilation of lessons learned and recommendations for further streamlining of the DOD processes.