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This paper was motivated by an interest in finding a way to determine the reliability of a system of interacting components in which the interaction effects can be specified by a set of parameters. Models are developed in which the basic assumption is that component interaction generate a linear statistical correlations among the conditions of groups of components. Formulas are then developed for the joint reliability of series and parallel systems in which the effects on system reliability are represented by these correlations.

The toxic properties of beryllium have been known for many years. New developments in the fields of industrial hygiene and manufacturing have greatly reduced the hazard in fabrication of beryllium components. These new methods of control have also reduced the cost of process control. This paper describes the techniques used by North American Rockwell to control the toxic effects of fabricating beryllium. Also discussed are the medical controls.

Many spacecraft experiments and systems employ drive systems which contain gear trains, slides, rachets, and similar components subject to sliding wear. In order to inhibit or mitigate the wear, some manufacturers employ surface hardening processes, including nitriding. Cases of three such applications are reviewed. One involved rachets made of Nitralloy 135M on a spectrometer grating drive. These rachets suffered excessive embrittlement of the very small (10 mil height) rachet teeth. Another case involved Type 416 stainless steel gears in a small motor gear train. These were nitrided by a proprietary process and suffered flaking of the nitriding and chipping of the gear teeth during testing. A third case involved a pinion gear on an infrared scanner which also was made of Nitralloy 135M and nitrided to increase its surface hardness. This gear was subject to flaking of the nitrided case and also breakage of the teeth.

Microbiologists are concerned that uncontrolled planetary exploration may contaminate the planets with terrestrial microorganisms. Should this happen, we would never know if our Earth is really unique in the Solar System. Such contamination could happen through carelessness or by accident. To avoid such an occurrence, world scientists agreed to keep the environment of the planet Mars inviolate through 1984 -- to achieve a contamination probability of 10−3 or less. The challenge facing the materials engineer in the manufacture of space vehicles where both particulate cleanliness and biological contamination must be rigidly controlled will be discussed. A brief review of the techniques of sterilization will also be presented. Some of the problems which must be considered because of the sterilization requirements are discussed. Thermal and chemical environments which will be required place a new burden, and an entirely new reliability history must be obtained.

The principle of maximum entropy is used to obtain the prior probability distribution functions for critical creep-strain and creep-rupture characteristics of engineering materials, operating at known high temperatures and uniaxial stresses. From the prior distribution function obtained, reliability function which is simply the probability of successful operation of the material, can be derived for specified critical creep-strain and creep-rupture modes of failure. An attempt is made to derive the reliability functions from prior considerations of the mechanics of failure, and the mechanical and physical characteristics of engineering materials. This work assumes that mechanical creep design reliability functions for creep-rupture and critical creep-strain modes of structural elements can have values such that the failure of the elements can occur either by any of the modes of failure or by the assumed combined modes of failure.

THIS PAPER introduces a new field called Physics of Maintainability. This is a concept for an organized scientific approach to the solution of special design oriented problems in maintenance. The conventional maintenance approaches can be strengthened and provided with adequate tools and techniques for the new challenges being raised by the recent advances in the electronic state-of-the art. This paper describes the new field and discusses some familiar aspects of maintenance which will be affected by it. Materials in Design, Aid to Trouble Isolation, Applications to Microelectronics and Implications of Maintenance in Space are some of the topics discussed.

A new type of rotary wing aircraft, the compound aircraft, is currently in development for the armed services. This new method of VTOL flight appears to offer great promise to the commercial VTOL field, particularly as it applies to the interurban mass transportation problem. It has been apparent for some years that fixed wing aircraft, due to airport congestion both in the air and on the ground, cannot fill this requirement. The possibilities of this new type of aircraft in this environment are discussed.

The management of engineering and engineers provides a challenge to engineering managers to maximize cost effectiveness. Industry and the educational community have successfully developed the precision of various disciplines to achieve technical excellence of engineered items. In doing this, certain aspects of education, training, and experience may have been overlooked. Engineers have made significant contributions in many areas in developing the theories, the technologies, materials, and equipment, with their application to subsequent conversion into various levels of sophisticated and useful hardware.

This paper presents the procedures used by Douglas Aircraft Co. in maintaining the cleanliness of parts that have been cleaned and packaged in a clean room. Specific procedures are discussed for propellent and hydraulic systems and spacecraft.

Research on metal-matrix composites for turbine compressors has demonstrated that four areas of compatibility are very important in composite design, and all must be considered in detail when specifying metal-matrix composites for structural applications. These areas comprise: chemical compatibility between matrix and filament, elastic strain compatibility, physical property compatibility, and manufacturing process compatibility. The designer must have detailed knowledge of every step in the composite manufacturing process to predict structural performance. Control of the manufacturing process to achieve maximum reinforcement from the filaments is considered the most important single factor. Asymmetrical elastic properties introduced by residual stresses or area ratio variation appear to be the most difficult aspect to appraise. A result of such asymmetry is dimensional and structural instability in a changing temperature environment.

Several aspects of V/STOLs for short-haul transportation are considered: production time needed to produce a craft with suitable operational characteristics, profitable operation, noise, safety and reliability, air traffic system control, landing facilities, passenger comfort, marketability, size. The author urges that a joint effort by military and civilian departments of the government and industry be undertaken to develop a V/STOL transport system. Factors to be considered are discussed.

An analytical investigation of the design and transient performance of a representative space vehicle thermal control system is used to transfer waste heat from the vehicle's environmental control/life support system to a space radiator. The system was designed by suboptimizing system components on the basis of weight and power at various flow rates, and subsequently finding the minimum total system penalty and corresponding system flow rate. With Freon 21 as the heat transport fluid, the transient analyses indicated that heat loads as low as 20% of the design heat load were permissible without causing incipient freezing of the Freon in the radiator tubes.

A typical military short haul airlift situation is postulated for the 1970–80 period. Based on this generalized picture of operational requirements, criteria are developed qualitatively with respect to the principal characteristics of a mixed fleet of advanced V/STOL short haul aircraft to support the postulated airlift operation.

An analytical thermal model of the project Apollo Command Module has been developed by the General Electric Co., Apollo Support Dept. for the National Aeronautics and Space Administration, Manned Spacecraft Center. This model simulates the entire spacecraft structure and the four closed fluid loops of the Environmental Control System. The configuration of the model is discussed as well as the correlation of this type model with test data. Also covered are the environmental data used in conjunction with the model for mission analysis. Typical results of the mission analyses are discussed in more detail.

The interfaces of engineering and management offer an insight into why the engineer, when viewed as in his castle, avoiding constraints, seems out of contact with the facts of business life. His sharing in the benefits and yields, while shunning a full measure of responsibility, appears less than glamourous in final, depersonalized analysis. A view of the engineer as manager, judicious scheduler, and user of resources after regressive analysis of professional antecedents and future expectations; the engineer as participant, delineator, and communicator; as active in the art and science of management as well as in design, innovation, and research, can be projected as faces of an attainable value, with enhanced professional esteem.

This paper presents the environmental control and life-support system design for the 21 and 30 day mission NASA Biosatellite program. A two-loop system is described which provides temperature control for the fuel cell power source, cryogenic gases, water and urine storage, and the gas management system. The latter provides control of the gaseous environment in the recovery capsule. It controls temperature, relative humidity, recirculation and filtration of the atmosphere, buildup of toxic and/or nontoxic gases and odors, and partial and total pressure of the nitrogen/oxygen atmosphere. Comparison of experimental results with analytical predictions are presented. Extensive thermal vacuum system testing was performed to verify design predictions; good agreement with analysis was achieved.

This paper defines and discusses technical obsolescence of engineers and scientists. It is concerned with the knowledge explosion in general terms, and in specific areas. The impacting force of the knowledge explosion is considered in terms of organizations and individuals. An approach to assessing the impact of the knowledge explosion is proposed. The responsibility for positive action to avoid technical obsolescence is discussed. The scope of this paper is restricted to the technical obsolescence of engineers and scientists, and does not concern itself with equipment and facilities.

Familiarity with beryllium metal machining and handling characteristics places the material in favorable perspective with conventional materials. The stability, coefficient of expansion, and thermal conductivity of beryllium are very favorable to achieving and maintaining size control. Extensive use in the aerospace industry has assisted in development of allied processes that further enhance the achievements in fabrication techniques. This paper shows the evolution of fabrication considerations from procurement through completion of parts. Interim processes and surface treatments will be discussed, featuring some applications.

New developments in braze-joining are presented. This technology will extend practical utilization of beryllium in fabrication of lightweight, exceptionally stiff components. Consideration of structural beryllium brazements is discussed. Some examples are monocoque cylindrical and conical shapes, radiator assemblies, sheet metal brackets, and sandwich structures. Beryllium exhibits attractive properties up to 1200 F. Special fabrication techniques are necessary, however, due to its metallurgical and mechanical peculiarities. Data presented show the effect of filler metal interactions on stress levels attainable in properly brazed joints. Beryllium is extremely versatile and is an unparalleled material of construction where strength/weight at elevated temperature is the criterion.

Electrical discharge machining, through imagination in the design of unique tooling, machining motions, and machine design flexibility, has made many major breakthroughs to establish it as a production process in the metal working industry. It has proved a most economical method of producing unusual production operations, with specialized machines to perform single production operations either impossible by conventional machinery or, at best, very expensive. It has also found application in the production of large piece parts.