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We analyse 635 set-years of service experience of 147 merchant-marine steam-turbine-gear propulsion sets, finding an MTBF of 23.5 set-years. The sets of one good-sized fleet have 3 times as large an MTBF as the rest of the sample, a fine return on the more conservative attention paid them. The sample size increased linearly with date. The most satisfactory analysis was as a plot of age-wise cumulatives of failures and service-life. This detected a significant short relatively trouble-free wear-in period with an MTBF of 9.3 set-years; later service had a 27.6 set-year MTBF. We discuss many failure modes and the design and operating practices that minimize them. Much of the favorable MTBF comes from avoiding all but a very little innovation in the design of individual sets.

As an introduction, the paper shows that for spacecraft systems to be designed for the next generation of scientific missions, the system complexity and long life requirements produce reliability criteria which can not be met by either current satellite logic circuitry nor application of redundant sets of such circuitry. The paper then describes a circuit composed of available integrated circuits along with a passive voter circuit and providing majority voting at the logic element level. This circuit is analyzed both from reliability and performance standpoints to show that approximately two to three orders of magnitude improvement in reliability without any significant degradation in performance is realizable.

Three separate and distinct electrolytic and one galvanic process were identified by visual inspection, metallographic, electron microprobe, and x-ray diffraction analysis in a clocked, flip-flop integrated circuit flat pack and/or the associated printed circuit test jig (two on flat pack and two on circuit board). These four processes were all found to be detectable by the use of noise measurements in microvolts per root cycle at 1000 Hz (cycles per second). The direct current applied for noise measurement to the integrated circuit devices was 100 micro-amperes, as compared to the 6-8 milliamperes required for normal operation. After initial experimentation, the devices were caused to fail in a laboratory ambient environment, followed by an acceleration of the rate of electrolytic reaction through the use of essentially 100 percent relative humidity, versus the upper specification limit of 80 to 98% relative humidity.

The techniques of device manufacturing control and screen testing employed today allows an escape rate of latent defects which makes probability of mission success of a manned interplanetary mission questionable. The increased system complexity and mission duration underscore the need to establish maximum integrated circuit reliability and a test sequence to prove that it exists. This paper describes a technique of utilizing life distributions of Integrated circuits obtained under high-stress testing to establish reliability screening criteria. Discussed are the basic factors controlling observable lot behavior, what can be learned from them, and how they dictate a test approach. Analyzed are the typical life expectancy distributions obtainable from today's devices; what the probable escape rates of defective devices are; how they may be made observable; and finally, how the expected life of accepted devices may be altered by stress screening.

A preliminary investigation to determine the feasibility of mathematically simulating a driver as a control element in the vehicle-driver system is discussed. An artificially produced cross-wind disturbance maneuver was chosen. This paper describes the investigation and concludes that, despite limitations, it is feasible to achieve some degree of simulation of the driving task for a specific maneuver.

Ingredients necessary for studying the effects of environmental interactions are presented. A technique for quantitatively predicting the effects of combined environments upon components was developed and applied to test data obtained under controlled conditions. The synergistic effects were equalized as to exposure time and the number of environmental encounters. The data was then statistically analyzed with the following conclusions: 1. Combined environments produce a synergistic effect which acts to reduce the over-all stress severity imposed upon components by the individual environments. 2. The length of time parts are exposed to a combined environment is more critical to component life than the number of encounters with that environment. 3. Combined environments appear to produce the same effect upon a given component irrespective of the environments concerned in the combination. 4. Different components are affected in different ways by a given combined environment.

Thermal problems peculiar to cryogens stored in a reduced gravity environment are discussed along with some techniques considered for their solution. Included are gravitational effects upon transient and steady-state nucleate boiling, heat transfer and temperature fluctuation, and meniscus displacement and distortion. To place these problems in proper perspective, a brief survey of the various heat transfer modes is presented. One device, which appears to warrant serious consideration, is the thermodynamic separator and its operation is briefly described. To illustrate the importance of certain problems peculiar to reduced gravity, a number of numerical examples are presented.

A liquid fluorine closed flow loop and engine test position has been designed, constructed, and operated for extended periods with very few difficulties. This paper describes the design philosophy of the system and discusses the operation experience gained in rocket engine firings and cold flow operations. Based upon experience with this system, a new attitude toward the handling of fluorine has evolved. Fluorine may now be handled with confidence so long as its peculiar characteristics are considered and respected. In this light, more realistic safety, cleaning, passivation, and testing procedures have been developed and are described herein.

Assessment of the design requirements for an LH2 heat exchanger to service the Saturn II Stage dictated the need for a more efficient and reliable type of heat exchanger than was presently known to exist. To accomplish this and also advance the state-of-the-art of existing concepts, a liquid-to-gas and a counterflow gas-to-gas type heat exchanger utilizing both latent and sensible heat of vaporization of liquid hydrogen were combined into one envelope. A discussion of the design, operation, and problems of the unit will be included within the scope of this paper. Important conclusions established from the design and performance data on this type of heat exchanger are as follows: 1. Efficiency is improved. 2. Cost of operation is reduced. 3. Physical size is reduced. 4. Flexibility is increased

With the aid of plastic structural analysis, the reliability (against plastic collapse) of a portal frame subjected to simple loading conditions is analyzed under a number of simplifying assumptions. It is shown that a minimum weight design under specified reliabilities is possible and that such a design might be compared with the standard deterministic design for better interpretation of safety factors that are presently in practice.

Improved structural design criteria for gust loads on aircraft are presented based on the continuous turbulence concept and probabilistic considerations. It is proposed that these improved criteria may replace the heretofore used discrete gust concept. The improved criteria consist of a rational-probability analysis backed up by a design envelope analysis. Both of these analyses are related to the strength level of a previously successful commercial transport and employ power spectral density techniques to establish design values. In conjunction with the rational-probability analysis, an acceptable failure probability is specified, and, for the design envelope analysis, a design limit gust velocity is established. Finally, the turbulence field parameters that may be used for design calculations on new aircraft are specified.

The application of cryogenic fluid storage systems to manned spacecraft is considered attractive primarily because of the substantial weight and volume saving afforded compared with high-pressure gaseous storage at ambient temperature. The major use of the stored fluids has been as a metabolic support (oxygen) and as reactant supply (hydrogen and oxygen) to the fuel cell for power generation. In addition cryogenic helium is used for descent propellant tankage pressurization aboard the lunar module. The subsystems developed for the NASA Gemini program, the firts full-scale operational application of this type of equipment, are discussed as a baseline for comparison with more advanced designs for subsequent programs. State-of-the-art design improvements are presented in some detail. Current programs (i.e., Apollo, Lunar Module, Biosatellite (primate), Manned Orbiting Laboratory, and the Air-lock Module) utilize cryogenic storage and supply subsystems for the usages mentioned earlier.

The changing, growing, and, hopefully, improving application of the behavioral sciences and related disciplines to the conceptualization, development and use of complex work systems demands adequate conceptualization about human performance. A useful framework for understanding the varieties of human performances in the complex system or formal work organization is presented. The approach here is interactionist, structuring human performance along the lines of the principal interactions of the human with the system environment and positing a fundamental “Performance Grid.” Multi-dimensional models are also discussed as basic to the systematic development of measurable aspects of human performance.

A major problem for Human Factors is implementing effective human performance consideration into system design; presenting the data in engineering, not psychological, terms. The most usual basic engineering requirement is for information which can be handled in mathematical terms. Mathematical description of human performance is difficult because of the non-linear and time-varying characteristics of man. The human factors mathematical data needed for system Conceptual Phase engineering solutions are generalized models, rules of thumb, or sovereign factors. During the Design Phase human task performance, and especially task complexity, should be quantified. During System Acquisition Phase, operation failure and error analyses must include valid human error probability determination. Methods of meeting these requirements are suggested.

This paper will concern itself with the reliability aspects of the ABRES feasibility programs. A specific example of the Athena program will address booster and data acquisition system reliability improvement. In addition to typical reliability practices, strong management control and examination of the hardware, procedures and design compromises resulted in a continuous reliability growth during the course of the program. The criticality of payloads obtaining good payload test data from very few and expensive flights requires an entirely different approach for the reliability aspects of these systems. Finally, some specific thoughts and techniques employed to achieve the enviable record for this program will be described.

The objectives of Category II and III Test Programs, particularly with relation to reliability demonstration, are described. Data is presented and analyzed from the Category II and III tests of two different systems, one a missile, the other an airborne radar fire control system. Examples are given of reliability improvements that were introduced during the Programs, with emphasis on coordination between factory and field. The importance of proper organization and control of the Test Program is discussed, and attendant problems are illustrated. It is concluded that even though limitations exist, Category II and III tests come the closest to allowing the total system to be exercised under operational conditions; and that from the test results, assessments can be made of demonstrated reliability, and significant reliability improvements can be achieved.

A study is made of the current research programs in reliability performed in the Navy. Primary emphasis is placed on identifying these programs and requirements for achieving a balanced basic research effort in reliability. Areas of interest include mathematical, engineering, behavioral and management sciences. The two principal functions that a sound program in basic reliability research can fulfill are (1) to increase the emphasis placed upon reliability aspects in relevant scientific research and (2) to provide the fundamental work leading to reliability techniques, methods and knowledge for use across all Naval organizations.

The reliability analysis is formulated for a certain type of statically indeterminate structure with random resistance and subjected to a random load. Specifically, this paper studies the effect of stress redistribution on the reliability of the structural system due to the failure of certain redundant members in an m-member plane truss. In addition, the probabilities of complete survival for structures with different degrees of redundancy were compared on the basis of equal volume of materials used.

The LW-3B Escape System was designed for low and medium performance V/STOL aircraft. The recovery capability of the system at speeds less than 200 KEAS, where most ejections from these aircraft occur, exceeds all contemporary escape systems, with the exception of other LW systems, which utilize the same parachute deployment system. This advance in the state of the art was achieved by a arranging a standard, 28 ft personnel parachute so that it is deployed immediately after seat-aircraft separation, thus reducing as much as 3 sec the time from initiation of the escape sequence to full inflation of the recovery parachute. This paper describes the operation of the two-mode LW-3B Escape System and its development and qualification pro -gram.

Escape systems for USAF aircraft must be designed to successfully recover crew members from disabled aircraft under a myriad of conditions. These conditions encompass a wide speed range, vary with altitude, and involve adverse aircraft attitudes including high sink rates. Designing a system which will satisfactorily perform over the entire spectrum poses many problems which necessitate various trade-offs to achieve a practical escape system. Emphasis is now being placed on low speed, low altitude, high sink rate, and adverse attitude escape capability. This is a significant problem area today and will be even more important with the advent of vertical take-off and landing (VTOL) aircraft. Escape and recovery under these conditions can be achieved only when the time from initiation of the escape sequence to full inflation of the parachute is kept to a minimum. However, the high speed performance of aircraft is increasing, with further complicates the escape system design.