Commentary on Space Propulsion Activities
Space propulsion systems required to launch large payloads - General commentary
PROPULSION SYSTEM↗
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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.
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A commentary on satellite communication devices.
Commentary on active and passive satellite communication devices including attitude control, solar cells, batteries, etc
COMMUNICATIONS DEVICE↗
Commentary on the 1985 NASA/Vanderbilt Symposium on Future Hypervelocity Flight Requirements
The discussion, started in Semiannual Status Report Number 1, on aerothermal problems of hypervelocity flight and experiments that may lead to significant improvements in analytical/computational predictive methods, continues. The commentary is based on presentations made by speakers at a symposium on this subject held in December 1985. Symposium participants focused on the serious deficiencies that exist in knowledge of real-gas, nonequilibrium thermochemical-kinetic processes, catalytic processes, surface and shock slip, gas/surface interaction, boundary layer transition, and vortical leeside flows under hypervelocity conditions. Programs of laboratory research and computations leading toward in-flight experiments were recommended. Feasibility of appropriate measurement techniques for the flight environment was assessed and problems for study in that area identified. A synopsis of the oral presentations is given.
Potter, J. L.↗
A commentary on low-cost transportation.
Low cost rate transportation as mandatory goal for future space program, discussing recovery and reuse, launch system costs, hardware development, etc
Tischler, A. O.↗
Commentary on present practice
Specimen size and mechanical factors in plane strain fracture toughness testing of metallic materials
Brown, W. F., Jr.↗
The effects of chronic acceleration of animals - A commentary
Chronic acceleration effects on animals, considering growth rate, food intake, oxygen metabolism and life expectancy
Wunder, C. C.↗
Salyut-6--Soyuz-29: Our commentary, the crew and the station
A newspaper article written by an assistant flight director which stresses the importance of cosmonaut training is presented. The preliminary stage of training is discussed, and the training of a crewmaker on a real spacecraft is briefly covered. The success in training foreign cosmonauts by Soviets is also discussed. The author feels that training is even more important today than it was seven or eight years ago because of the increased complexity of the experiments and the length of time a cosmonaut spends in space now.
Kravets, V.↗
Salyut-6-Soyuz: Our commentary
The physical exercise and medical monitoring programs conducted during the Salyut-6-Soyuz space flight are discussed. A special suit for physical exercise which provides a load in the longitudinal direction of the body is described. A vacuum device to create reduced pressure and thus prevent disruption of blood circulation is reported. Medical examination of the cosmonauts upon landing and their reported health is discussed.
Burnazyan, A.↗
A commentary on solid lubricants and wear resistant solids for use in extreme environments
The need for high temperature tribological coatings and self-lubricating materials in advanced technology is discussed. A qualitative model for the mechanism of solid lubrication is proposed. The model is based upon microscopic observations of the dynamics of third-body solids in lubricated contacts. In this model, the rheology of plastic flow is suggested as a more general criterion for predicting the lubricating potential of a solid material than, for example, a specific crystal structure. Some examples of layer-lattice and nonlayer-lattice solids that lubricate by virtue of their extreme plasticity, film coherence, and adhesion to the lubricated metal are described. Circumstantial evidence for the model is presented for low shear-strength solids at room temperature and for solids such as calcium fluoride that become lubricative only when their brittle-to-ductile transition temperature is exceeded. Some materials considerations in the selection of hard-coat materials for wear control are also presented.
Sliney, H. E.↗
The basal ganglia-circa 1982 - A review and commentary
A review is presented of recent studies which utilize new anterograde and retrograde axon transport methods in order to improve knowledge of the projection of the basal ganglia and to clarify their sites of origin. These studies have thrown new light on certain topographic connectional relationships and have revealed several new reciprocal connections between constituent nuclei of the basal ganglia. Also examined are the many new histochemical techniques that are now providing regional biochemical overlays for connectional maps of the central nervous system, especially regions in or interconnecting with the basal ganglia.
Mehler, W. R.↗
Commentary on interstellar matter associated with 18 open clusters
Information supplementary to that contained in Section 4 of an article entitled, A CO Survey of Regions Around 34 Open Clusters, (Leisawitz, Bash, and Thaddeus) published in the Astrophysical Journal Supplement Series, Volume 70, Number 4, August 1989 is summarized. The information presented here, which describes the interstellar environments of young clusters and some cluster physical characteristics, comes from observations published in the astronomical literature and the author's carbon monoxide (CO) emission line survey, and may help clarify our understanding of the interaction of massive stars with the interstellar medium.
Leisawitz, David↗
A commentary on perception-action relationships in spatial display instruments
Transfer of information across disciplines is promoted, while basic and applied researchers are cautioned about the danger of assuming simple relationships between stimulus information, perceptual impressions, and performance including pattern recognition and sensorimotor skills. A theoretical and empirical foundation was developed predicting those relationships.
Shebilske, Wayne L.↗
A personal history of the human exploration initiative with commentary on the pivotal role for life support research
The author relates the history of the human exploration initiative from a personal perspective from the 1961 J. F. Kennedy initiative to land a man on the moon up to 1986 when a memo was circulated from NASA Headquarters to its employees which stated as a major goal the expansion of the human presence beyond Earth into the solar system. The pivotal role of life support research is woven into this personalized history.
Mendell, Wendell↗
The role of failure/problems in engineering: A commentary of failures experienced - lessons learned
The written version of a series of seminars given to several aerospace companies and three NASA centers are presented. The results are lessons learned through a study of the problems experienced in 35 years of engineering. The basic conclusion is that the primary cause of problems has not been mission technologies, as important as technology is, but the neglect of basic principles. Undergirding this is the lack of a systems focus from determining requirements through design, verification, and operations phases. Many of the concepts discussed are fundamental to total quality management (TQM) and can be used to augment this product enhanced philosophy. Fourteen principles are addressed with problems experienced and are used as examples. Included is a discussion of the implication of constraints, poorly defined requirements, and schedules. Design guidelines, lessons learned, and future tasks are listed. Two additional sections are included that deal with personal lessons learned and thoughts on future thrusts (TQM).
Ryan, R. S.↗
Computer aided reliability, availability, and safety modeling for fault-tolerant computer systems with commentary on the HARP program
Many of the most challenging reliability problems of our present decade involve complex distributed systems such as interconnected telephone switching computers, air traffic control centers, aircraft and space vehicles, and local area and wide area computer networks. In addition to the challenge of complexity, modern fault-tolerant computer systems require very high levels of reliability, e.g., avionic computers with MTTF goals of one billion hours. Most analysts find that it is too difficult to model such complex systems without computer aided design programs. In response to this need, NASA has developed a suite of computer aided reliability modeling programs beginning with CARE 3 and including a group of new programs such as: HARP, HARP-PC, Reliability Analysts Workbench (Combination of model solvers SURE, STEM, PAWS, and common front-end model ASSIST), and the Fault Tree Compiler. The HARP program is studied and how well the user can model systems using this program is investigated. One of the important objectives will be to study how user friendly this program is, e.g., how easy it is to model the system, provide the input information, and interpret the results. The experiences of the author and his graduate students who used HARP in two graduate courses are described. Some brief comparisons were made with the ARIES program which the students also used. Theoretical studies of the modeling techniques used in HARP are also included. Of course no answer can be any more accurate than the fidelity of the model, thus an Appendix is included which discusses modeling accuracy. A broad viewpoint is taken and all problems which occurred in the use of HARP are discussed. Such problems include: computer system problems, installation manual problems, user manual problems, program inconsistencies, program limitations, confusing notation, long run times, accuracy problems, etc.
Shooman, Martin L.↗
Configuration Studies of Personal Air Vehicles. Personal Air Vehicle and Flying Jeep Concepts: A Commentary on Promising Approaches or What Goes Around Comes Around (About Every Twenty Years)
The NASA/Langley Personal Air Vehicle (PAV) Exploration (PAVE) and the DARPA (Defense Advanced Research Projects Agency) Dual Air/Road Transportation System (DARTS) projects were established to investigate the feasibility of creating vehicles which could replace, or at the very least augment, personal ground and air transportation schemes. This overall goal implies integrating several technology areas with practical everyday transportation requirements to design a class of vehicles which will achieve the following goals: (1) Vertical, Extremely Short, or Short Takeoff and Landing (VTOL, ESTOL, STOL) capability; (2) Operation at block speeds markedly faster than current combinations of land and air transportation, particularly in critical market areas; (3) Unit cost comparable to current luxury cars and small general aviation aircraft; (4) Excellent reliability; (5) Excellent safety; (6) Ability to integrate with existing land and air transportation systems. The conclusions of these configuration studies are summarized as follows: (1) Creation of the five assigned configurations prompted added explorations, some of which were dead-ends; (2) Some components could be common to all configurations such as avionics and dual-mode suspension schemes; (3) Single-Mode PAVs can be created by removing dual-mode-specific items; (4) Aviation history provided some intriguing starting points, as in what goes around comes around; (5) CTOL (Conventional Take-off and Landing) and STOL dual-mode PAVs look feasible with single-mode PAVs being simplifications of the dual-mode approach; (6) VTOL PAVs will require development; (7) More exotic collapsing mechanisms mechanisms need development; (8) As a teaching tool, PAVs are not yet a well-enough bounded design problem.
Hall, David W.↗
The Case for Durative Actions: A Commentary on PDDL2.1
The addition of durative actions to PDDL2.1 sparked some controversy. Fox and Long argued that actions should be considered as instantaneous, but can start and stop processes. Ultimately, a limited notion of durative actions was incorporated into the language. I argue that this notion is impoverished, and that the underlying philosophical position of regarding durative actions as being a shorthand for a start action, process, and stop action ignores the realities of modelling and execution for complex systems.
Smith, David E.↗
A Reply to Diem et al.'s Commentary on a Recent Literature Contribution Focused on Urban-Induced Rainfall in Atlanta
A response is provided to Diem and colleagues discussion on the whether urbanization-enhanced precipitation should be maximized in the South-Southeast of Atlanta, Georgia as documented in Shepherd et al. (2003). Diem and colleagues have offered a critical response to Shepherd et al. (2002). The response herein offers both general and specific responses to issues raised by Diem and colleagues.
Shepherd, J. Marshall↗