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Compensation efforts directed at the stabilization and control of the Saturn S-II engine actuation system have given rise to nonlinear compensation philosophies that are also applicable to other types of hydraulic positioning servos. The analysis presented in this paper shows by theoretically and analog simulation techniques that a lag-lead form of compensation is superior to the presently popular dynamic pressure feedback (DPF) for reducing system step position errors in the presence of a large stiction/cou-lomb gimbal friction component. This result is important because nonlinear friction positioning errors are directly related to the magnitude of the resultant vehicle attitude limit cycle. An analog computer nonlinear system simulation was used to verify the analytical results discussed herein. Using the ITAE criterion, step and ramp responses of the system were compared to evaluate the DPF and laglead networks.

Because of the capability of extended accuracy, digital systems are indicated for guidance and control of spacecraft. Furthermore, by implementing these systems with integrated microelectronic components, substantial improvement in reliability can be expected. A study and experimental evaluation program was performed to apply such digital techniques to the spacecraft stabilization and control problem. Of major consideration were the selection of appropriate mathematical techniques for system analysis and the development of suitable fabrication methods for hardware implementation. A discrete state model of a spacecraft reaction wheel and jet attitude control system was developed and computer simulations were performed. An electronic control unit for this system was designed, constructed with semiconductor integrated microelectronics, and tested on an air bearing simulator.

The Aerojet Carbothermal Process for manufacture of oxygen from lunar resources has three essential steps: (1) reduction of silicate with methane to form carbon monoxide and hydrogen; (2) reduction of carbon monoxide with hydrogen to form methane and water; and (3) electrolysis of water to form oxygen and hydrogen. This cyclic process does not depend upon the presence of water or water precursors in the lunar materials; it will produce oxygen from silicates regardless of their precise composition and fine structure. Estimates are made of weight, power, and labor requirements for the operation of three different size lunar chemical plants for the manufacture of propellant oxygen from lunar raw materials.

This paper discusses the analytical simulations employed by Columbus Div. of North American Aviation to analyze the landing gear and associated vehicle response for A-5 aircraft, Apollo, and OV-10A. A brief development of the mathematical simulations with the basic equations of motion is included, along with methods used to predict the loads due to running over arresting cables or deck lights. The method of obtaining internal load distributions of the vehicle structure is also given. Where available, results of the analyses are compared with experimentally measured data. Finally, a discussion of the validity and applicability of the methods together with the conclusions based on the results are presented.

A description is given of the wind tunnel installation at M. I. R. A. comprising a full-scale wind tunnel which incorporates a 250 hp roller dynamometer, and a wind tunnel for quarter-scale models. Tests show good correlation between aerodynamic drag in the full-scale tunnel and the road, and between the roller dynamometer and the road, but correlation has not yet been established for other coefficients, or between model and full scale tunnels. Results from the full-scale tunnel show that drag coefficients are tending to rise and the need for careful design is underlined. Results from model tests indicate that drag coefficients can be markedly reduced without sacrificing styling.

The equation for lateral motion of a car, according to the “two degrees of freedom” mathematical model, are developed, taking into account the contribution of the aerodynamic forces applied to the car moving in stationary air. Modifications introduced by aerodynamic effects on stability and steering control are derived and discussed, also in a first-order approximation. In addition, successively numerical examples are utilized to illustrate the conclusions of the study described.

The complicated energy conversion processes in a Stirling cycle machine are simulated on an electronic analog computer. This gives the cyclic variation of all the time variables (pressure, temperature, torque, and so on), and the integrated energy quantities (heat exchange, work, losses, and so on) and, hence, yields a complete heat balance. Operating conditions are defined by specified parameters, and changes can be made very easily for a wide range of solutions. One sample solution is included, as well as graphs and heat-flow diagrams, showing the effect of changes in the regenerator efficiency when all other factors are kept constant. This has led to a new understanding of the regenerative process.

A simulation program is established to determine the probability of success of a lunar surface vehicle in completing its primary mission, as well as various partial missions. This determination is obtained as a function of lunar surface conditions with realistic effects arising from equipment reliability and instrumentation accuracy. A Monte Carlo simulation technique accounts for the statistical nature of such variables as terrain and reliability without requiring real-time problem solution. The application of this computer program in the vehicle design phase facilitates trade-offs between subsystem performance and weight or power. The selection of operating strategy for normal and adverse lunar conditions (terrain or equipment difficulties) can be made.

The current joint NASA-FAA simulator program, designed to study the problems anticipated in the integration of the supersonic transport (SST) into the air traffic control (ATC) system, is explained. The initial tests have consisted of simulated departure and arrival operations of a variable-sweep SST configuration in the New York terminal area under high-density traffic flow conditions with as many as six SST operations per hour. Several types of separation standards and handling concepts were investigated while using an ATC system based on present-day concepts and procedures. Results describing the operating problems for the SST and the workload, delay, and capacity problems for the ATC system are discussed.

A first attempt to study civil aircraft operations comprehensively, prior to having the airplane, occurred before the initial operation of U.S. subsonic jets. One airline carried out a manual-simulated “paper jet” operation lasting fifteen months. Today, computerized simulation of machines, methods, and operations has become commonplace, and replaces the slide rule and tedious day-by-day inputs of aircraft operational criteria. Computerized simulations are also applied to every aspect of the SST design and operations. These are important, but the results being should be used with caution and judgement.

A nondimensional representation for a four stroke spark ignition engine was obtained that included the transient charging and exhaust effects. Two basic advantages accrued from this approach; the design and operating parameters that evolved from the nondimensional approach are truly basic in nature, which makes the computer solution more universally applicable to all engines. The inclusion of the transient effects made the representation more realistic and of particular value in the study of engine breathing problems. The effect of valve timing, cam design, valve dimensions, and inlet temperature on engine performance were studied with the computer model.

The first part of the paper deals with the mathematical model and computer program for simulating a compression-ignition engine. The various assumptions used and the effects of these assumptions on the results are discussed. The second part of the paper evaluates results of the engine simulation program by comparisons with experimental data and with other simplified cycle calculations. The comparisons with experimental data include motoring, part load, and full load data for a speed range of 1400–3200 rpm. The simulation results show good agreement with experimental pressure-volume diagrams. The computed trends of volumetric efficiency, heat rejection, and metal part temperatures show reasonable agreement with experimental data.

A mathematical model of the scavenging process of uniflow two-cycle diesel engines is proposed. It assumes that certain general characteristics of a particular engine type are known. With a number of simplifying assumptions, the scavenging process and engine performance can then be analyzed by means of a digital computer. Experimental results are used to demonstrate the validity of the analysis. A number of scavenging system variables are investigated and a combination is proposed which should give optimum performance.

This paper sets up a mathematical model for measuring end-gas temperatures in spark ignition engines and the compression temperatures in compression ignition engines. The model is based on a modified thermodynamic equation, for which the nonlinear least square method is used to fit the parameters.

This paper describes the status of efforts to improve the safety of motor vehicle operation through training. The following types of programs are described: (1) the safety components of driver education and improvement courses, (2) the remedial training of traffic violators, (3) programs utilizing simulation techniques, and (4) the use of mass media such as books and films. A general lack of conclusive evidence concerning various training approaches is noted. A greater research effort should be directed toward (1) better identification of means by which accidents can be anticipated and avoided, (2)methods of coping directly with driver habits and skills, and (3) techniques of maintaining safe driving behavior through periodic evaluation and retraining.

The internal combustion engine cylinder head gasket is the most complex of all gasket applications. This is due to the variety of seals and sealing conditions which must be achieved in a single gasket. Some of the physical characteristics studied for such gaskets include spring rate, stress relaxation, torque loss, and permeability of current materials and elements used in these constructions. The effects of temperature, sealing stress, thickness, geometry, and engine operation on the properties of gaskets are discussed. In one of the theoretical derivations given, a mathematical model of a viscoelastic material is used to explain the results of certain experimental testing. Major emphasis is placed on spring rate and stress relaxation, which are directly related to fluctuations of sealing pressure and loss of torque which must be controlled in order to achieve satisfactory sealing.

Offtracking characteristics of single unit vehicles and combination vehicles are described. Offtracking values were obtained with scale models of vehicles making turns on turning radii varying from 25 feet to 225 feet. Individual vehicle offtrackings are influenced by three variables: degree of turn, length of vehicle wheelbase, and turning radius. Research found that the offtracking is greatest when the projection of the rear axle axis passes through the turning radius center; even though the projections of the other axles on the vehicle or trailer combination do not, at the same time, pass through the turning radius center.

Experiments have been conducted on seven cadavers to determine the nature of the response of the facial bones to impact with another body. The behavior of the individual facial bones, in particular the zygoma and the zygomatic arch, as a function of each of the several parameters such as velocity, mass energy, acceleration, padding, physical characteristics of bone, etc., are shown. Values are given for these parameters at fracture. Fist blows and falls are compared to equivalent controlled energy blows in the laboratory. It is shown that good correlation can be obtained between a mathematical model of the facial bones at impact and experimental results.