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A programming language for the flight software of the NASA space shuttle program was developed and identified as HAL/S. The language is intended to satisfy virtually all of the flight software requirements of the space shuttle. The language incorporates a wide range of features, including applications-oriented data types and organizations, real time control mechanisms, and constructs for systems programming tasks.
The ATS ground stations were described, including a system description, operational frequencies and bandwidth, and a discussion of individual subsystems. Each station configuration is described as well as its floor plan. The station performance, as tested by the GSI, is displayed in chart form providing a summary of the more important parameters tested. This chart provides a listing of test data, by site, for comparison purposes. Also included is a description of the ATS-6 experiments, the equipment, and interfaces required to perform these experiments. The ADP subsystem and its role in the experiments is also described. A description of each program task and a summary of the activities performed were then given. These efforts were accomplished at the Rosman II Ground Station, located near Rosman N.C., the Mojave Ground Station, located near Barstow Ca., and the GSI Contractors plant located near Baltimore, Md.
The experience of the National Aeronautics and Space Administration (NASA) with extravehicular activity life support emergency oxygen supply subsystems has shown a large number of problems associated with particulate contamination. These problems have resulted in failures of high pressure oxygen component sealing surfaces. A high pressure oxygen filter was designed which would (a) control the particulate contamination level in the oxygen system to a five-micron glass bead rating, ten-micron absolute condition (b) withstand the dynamic shock condition resulting from the sudden opening of 8000 psi oxygen system shutoff valve. Results of the following program tasks are reported: (1) contaminant source identification tests, (2) dynamic system tests, (3) high pressure oxygen filter concept evaluation, (4) design, (5) fabrication, (6) test, and (7) application demonstration.
MBASIC is high-level, interactive computer language that reduces time of computer task programming. Outstanding features of MBASIC include: multiple assignments or statements in single instruction; conditional, assignment, and repetitive statement modifiers; and excellent string-handling capabilities. Two machine versions are available: UNIVAC (written in reentrant Assembler code for execution under EXEC 8) AND DEC-10 (written in Assembler code for execution under TOPS-10).
The Near Term Hybrid Passenger Vehicle Development Program tasks included defining missions, developing distributions of daily travel and composite driving cycles for these missions, providing information necessary to estimate the potential replacement of the existing fleet by hybrids, and estimating acceleration/gradeability performance requirements for safe operation. The data was then utilized to develop mission specifications, define reference vehicles, develop hybrid vehicle performance specifications, and make fuel consumption estimates for the vehicles. The major assumptions which underlie the approach taken to the mission analysis and development of performance specifications are the following: the daily operating range of a hybrid vehicle should not be limited by the stored energy capacity and the performance of such a vehicle should not be strongly dependent on the battery state of charge.
Ease of handling and control in zero gravity and minimizing the quantity of water required were prime considerations. The program tasks include the selection of biocidal agent from among the variety used for surgical scrub, formulation of a dispensing system, test, and delivery of flight dispensers. The choice of an iodophore was based on effectiveness on single applications, general familiarity among surgeons, and previous qualification for space use. The delivery system was a choice between the squeeze foamer system and impregnated polyurethane foam pads. The impregnated foam pad was recommended because it is a simpler system since the squeeze foamer requires some applicator to effectively clean the skin surfaces, whereas the form pad is the applicator and agent combined. Testing demonstrated that both systems are effective for use as surgical scrubs.
The formal HAL/S language specification is documented with particular referral to the essentials of HAL/S syntax and semantics. The language is intended to satisfy virtually all of the flight software requirements of NASA programs. To achieve this, HAL/S incorporates a wide range of features, including applications oriented data types and organizations, real time control mechanisms, and constructs for systems programming tasks.
The key component of this concept is a coiled tube of silicon nitride which acts as a heat exchanger appears to be ideal from the standpoint of utilizing structural ceramics at around 2500 F under severe thermal shock conditions. However the size and configuration of this coil are beyond the state of the art for fabricating such materials as silicon nitride and carbide. A two-task program to develop and demonstrate the feasibility of extruding and forming a section of thin walled silicon nitride tubing was undertaken as an addition to the original program. A promising polyvinyl butyral-based binder lubricant was identified. Fourteen full size extrusion experiments were conducted. Two trial firings of 1-1/4 turn helices were made.
The Silicon Material Task of the Flat-Plate Solar Array Project was assigned the objective of developing the technology for low-cost processes for producing polysilicon suitable for terrestrial solar-cell applications. The Task program comprised sections for process developments for semiconductor-grade and solar-cell-grade products. To provide information for deciding upon process designs, extensive investigations of the effects of impurities on material properties and the performance of cells were conducted. The silane process of the Union Carbide Corporation was carried through several stages of technical and engineering development; a pilot plant was the culmination of this effort. The work to establish silane fluidized-bed technology for a low-cost process is continuing. The advantages of the use of dichlorosilane is a siemens-type were shown by Hemlock Semiconductor Corporation. The development of other processes is described.
The dynamic prediction model along with its macro-processor capability and data flow system from the Drexel Limited-Area and Mesoscale Prediction System (LAMPS) were converted and recorded for the Perkin-Elmer 3220. The previous version of this model was written for Control Data Corporation 7600 and CRAY-1a computer environment which existed until recently at the National Center for Atmospheric Research. The purpose of this conversion was to prepare LAMPS for porting to computer environments other than that encountered at NCAR. The emphasis was shifted from programming tasks to model simulation and evaluation tests.
There is a need for high temperature containerless processing facilities that can efficiently position and manipulate molten samples in the reduced gravity environment of space. The goal of the research is to develop sophisticated high temperature manipulation capabilities such as selection of arbitrary axes rotation and rapid sample cooling. This program will investigate new classes of acoustic levitation in rectangular, cylindrical and spherical geometries. The program tasks include calculating theoretical expressions of the acoustic forces in these geometries for the excitation of up to three acoustic modes (multimodes). These calculations are used to: (1) determine those acoustic modes that produce stable levitation, (2) isolate the levitation and rotation capabilities to produce more than one axis of rotation, and (3) develop methods to translate samples down long tube cylindrical chambers. Experimental levitators will then be constructed to verify the stable levitation and rotation predictions of the models.
Objectives are to evaluate the feasibility and limitations of fluid acquisition and transfer under an accleration induced in a tethered orbital refueling facility and to provide conceptual designs. Program tasks consist of recommendation of fluid transfer method and parameters; evaluation of disturbances, fluid motion, and damping; selection of passive devices to augment inherent fluid damping and determination of the resultant envelope of operation; assessment of the effect of tether lengths on hazards; and identification of ground and flight tests necessary to prove the tethered orbital refueling concepts.
NASA's Space Station Human Productivity and Man/System Integration Standards programs are described. The data collection methodologies and analyses utilized in the productivity study are examined. The study reveals that attention to habitability is required in order to maximize human productivity for on-orbit operations. The nine program tasks used to develop standards for man/system integration are discussed.
The current status of efforts to develop commercial space projects is surveyed, with a focus on US programs, in reviews and reports presented at the Second Symposium on Space Industrialization held in Huntsville in February 1984. Areas explored include policy, legal, and economic aspects; communications; materials processing; earth-resources observation; and the role of space carriers and a space station. Also included in the volume are 132 brief descriptions of the NASA Microgravity Science and Applications Program Tasks as of December 1984. These tasks cover the fields electronics materials; solidification of metals, alloys, and composites; fields and transport phenomena; biotechnology; glass and ceramics; combustion science; and experimental technology.
This work addresses the problem of reducing context switch overhead on a processor which supports a large register file - a register file much like that which is part of the Berkeley RISC processors and several other emerging architectures (which are not necessarily reduced instruction set machines in the purest sense). Such a reduction in overhead is particularly desirable in a real-time embedded application, in which task-to-task context switch overhead may result in failure to meet crucial deadlines. A storage management technique by which a context switch may be implemented as cheaply as a procedure call is presented. The essence of this technique is the avoidance of the save/restore of registers on the context switch. This is achieved through analysis of the static source text of an Ada tasking program. Information gained during that analysis directs the optimized storage management strategy for that program at run time. A formal verification of the technique in terms of an operational control model and an evaluation of the technique's performance via simulations driven by synthetic Ada program traces are presented.
The use of timing diagrams is recommended in the design and testing of multi-task Ada programs. By displaying the task states vs. time, timing diagrams can portray the simultaneous threads of data flow and control which characterize tasking programs. This description of the system's dynamic behavior from conception to testing is a necessary adjunct to other graphical techniques, such as structure charts, which essentially give a static view of the system. A series of steps is recommended which incorporates timing diagrams into the design process. Finally, a description is provided of a prototype Ada Execution Analyzer (AEA) which automates the production of timing diagrams from VAX/Ada debugger output.
The project was initiated to research Object Oriented Programming Systems (OOPS) and frame representation systems, their significance and applicability, and their implementation in or relationship to Ada. Object orientated is currently a very popular conceptual adjective. Object oriented programming, in particular, is promoted as a particularly productive approach to programming; an approach which maximizes opportunities for code reuse and lends itself to the definition of convenient and well-developed units. Such units are thus expected to be usable in a variety of situations, beyond the typical highly specific unit development of other approaches. Frame represenation systems share a common heritage and similar conceptual foundations. Together they represent a quickly emerging alternative approach to programming. The approach is to first define the terms, starting with relevant concepts and using these to put bounds on what is meant by OOPS and Frames. From this the possibilities were pursued to merge OOPS with Ada which will further elucidate the significant characteristics which make up this programming approach. Finally, some of the merits and demerits of OOPS were briefly considered as a way of addressing the applicability of OOPS to various programming tasks.
Controls structures interaction (CSI), a phenomenon which occurs when control forces interact with the flexible motion of a structure, can, if improperly treated in design and development, cause reduced performance or control instabilities. Properly applied, it can improve flexible spacecraft performance. In this paper, the NASA CSI technology program for future spacecraft applications is described. The program objectives and organization are outlined, and the nature of individual program tasks is described. The interdisciplinary aspects of CSI are also addressed.