Aerospace Problems Research Articles

Vibration Isolation of Pressure Transducers for Determination of Acoustic Environment

Measurement of pressure fluctuations due to acoustic environment is important in the investigation of turbulent flow phenomena associated with several classes of aerospace problems. These measurements, utilizing piezoelectric transducers, are accompanied by noise from vibrations of the structure on which the transducers are mounted. Two schemes for the vibration isolation of the transducers are experimentally investigated. These are: individual isolation of transducers, and isolation of an insert on which the transducers are mounted. Experiments were conducted in a 14 in.×14-in. supersonic wind tunnel at a nominal Much number of 1.96 and stagnation pressures of 30 and 45 psia. Comparison of the spectra of the pressure fluctuations measured by transducers mounted on a flat wall of the tunnel shows that structural noise above 3 kc/sec may be eliminated by any one of the two schemes, and that below 3 kc/sec may be eliminated by any one of the two schemes, and that below 3 kc/sec the structural noise is considerably reduced by these isolation techniques. In order to attain further insight into the manner in which a pressure transducer is affected by structural vibrations, coherence functions have been calculated for structural noise and observed pressure fluctuations.

Control: past, present and future

Automatic control developed historically as a necessary consequence of replacing human or animal power by wind and water power and later by steam power. Its beginnings were empirical, but an important contribution to the theory was made by Clerk Maxwell, and later the development of feedback amplifiers led to intensive theoretical work in the U.S.A. By 1945 a well-developed and highly successful theory was available, and wide applications have been made.In more recent times, theoretical effort has been concentrated on problems of guidance, using the calculus of variations. The incentive here was to solve aerospace problems, but there have been some applications to industrial problems. This theory seems to have a narrower range of applications than the earlier work.The development of the digital computer has placed in the hands of engineers a tool of unrivalled flexibility and power for the control of processes. By contrast, our theory is at present unable to exploit this power with full effect. The most promising field for control theory and application in the next five to ten years seems to be the application of computer control to all types of industry, and the development of the corresponding theory.

On the inter-influence of classical heterogeneous combustion research and related aerospace problems

Interest in heterogeneous combustion is a relatively recent development in aerospace operations though it has been the concern of industrial and fire research for half a century or more. The two areas operate at altogether different levels of combustion intensity, temperature, pressure, velocity, etc., but they have common ground at the fundamental level. In either area, a complete description of any combustion process requires information on the reaction mechanisms, their kinetics, the solid's response to thermal stress (pyrolysis), and the heat and masstransfer operations involved. The form of the differential equations describing the system's behavior are then the same but with different practical situations distinguighed by the appropriate coefficients and boundary conditions in the equations. Incorporation of all factors simultaneously has been called the multiple-factor approach which has been the more commonly used in aerospace research, in contrast to the single-factor approach more generally used in the classical research. Nevertheless, a multiple-factor analysis is no better than the accuracy of the basic postulates and, in this outline-review of mechanisms and behavior of solids in combustion, seven areas are identified that require clarification.

An integrated software system for hybrid flight simulation: The boeing hybrid simulator

The Boeing Hybrid Simulator is a general-purpose hybrid computer designed to provide a laboratory for the development of hybrid methods of solving a variety of aero-space problems as well as to support large-scale simulations. The first such simulation is a Flight Simulation Program which provides both a three-degrees-of-freedom missile performance analysis tool and a six-degrees-of-freedom missile subsystem design analysis tool. The 3D simulation was implemented by placing the integrations of the translational equations on the analog, utilizing the digital for function generation, some algebraic manipulations, and basic bookkeeping. The 6D was implemented by placing the integrations of the rotational equations on the analog and the integrations of the translational equations on the digital. Phase control was supplied on the analog in both cases. A hybrid oriented execute-time monitor system supported the simulations by 1) providing a flexibile man-machine relationship, 2) providing an automatic and manual control capability, and 3) reducing digital and analog setup time. It enabled the man at the console to bring system packages into computer memory either to temporarily displace the simulations or to tie in with them in such a way that activities closely related to the execution of the simulations occur at the end of frame calculations.

Hybrid techniques in statistical analysis I

Hybrid computation has been with us for a few years, and now techniques, procedures and applica tions are beginning to develop rapidly. We believe great strides can be expected in hybrid simulation now that many equipments are in the field and people are beginning to appreciate the value of bringing the respective qualities of analog and digital computers to bear on individual problems. This column is intended to disseminate information on hybrid simulation and tricks of the hybrid trade. We also hope to stimulate equipment users to provide us with contributions and comments we can publish. At present the subject of special interest to us in the field of hybrid computation is that of sampling effects at the analog-digital interface. We would en courage anyone who has anything to say on this subject—be it with regard to equipment, technique, program control, or the analysis of sampling-to write to us. The use of logic elements, gates, flip flops and counters, is foreign to most simulation people, and we are sure tricky circuits have evolved. Although the drive for hybrid came originally from the people with aerospace problems, many developments are occurring in other fields. These should be noted and made available to all who are interested. As a start this month, we present a short descrip tion by Baker Mitchell of his automatic correlator, which provides nice displays to watch and saves lots of time.

Aero-space problems are featured at 1960 AIEE Pacific general meeting

Aero-space problems are featured at 1960 AIEE Pacific general meeting