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The Space Shuttle Orbiter vehicle employs two earth storable bipropellant propulsion subsystems to provide orbit maneuvering and vehicle attitude control. Respectively, these are the Orbit Maneuvering Subsystem (OMS) and the Reaction Control Subsystem (RCS). The OMS provides the velocity increments necessary to achieve final insertion of the vehicle into earth orbit, to perform orbital changes, and to de-orbit the vehicle. The OMS is made up of two normally independent propulsion subsystems in removable pods. Each contains a 6000 lb. thrust rocket engine, propellant tankage, and necessary feed and control componentry. The propellant capacity of 24,721 lbs. for both pods provide a nominal 1000 ft/sec velocity increment. In addition, a supplementary propellant supply, the cargo bay kit, boosts the all-up delta V capability to 2500 ft/sec.

This paper presents the metric program approach taken by the Boeing Aerospace Co. in the design and fabrication of the PHM hydrofoil ship. The program approach was to maintain a strict metric base line allowing exceptions only where extensive qualifications, schedule impact, costs, and reductions of performance were imposed by a metric design. The program metric implementation plan is described. A discussion is provided of the metric problems encountered and the solutions evolved. The PHM ship evolves as a hybrid design where the structural design is metric and some of its operating systems are inch designs. An analogy is made relating the approach to more sophisticated aerospace-type programs as spacecraft, aircraft, etc. The analysis is made on the basis of a need for additional aerospace quality engineering metric standards in order to produce a complete metric design.

The Heavy Lift Helicopter (HLH) is the airborne component of a container ship and helicopter logistics system. The U.S. Army initiated a program for development of advanced-technology components (ATC) for the HLH in June 1971 to reduce the risk associated with future procurement of an air vehicle. The components now under development by Boeing Vertol include the rotor and drive systems, flight-control system, and cargo-handling system. In addition, Boeing Vertol selected and procured representative HLH engines for use on an integrated rotor- and drive-system test rig. The HLH program has now been extended to include construction and flight-test demonstration of an austere prototype aircraft to evaluate the ATC components in a dynamic environment.

Computer graphics has become the bridge between the computer and the designer. McDonnell Douglas' CADD system was originally developed for parts layout and solutions to geometry problems, and this restriction was maintained until recently so development could be controlled. Now, with the maturing of the system, several disciplines are converting the computer graphics design package to their special applications. Recent advances in computer graphics software have been adapted to advanced design. The integration of these disciplines has required a number of changes in design techniques in order to evolve and evaluate a conceptual configuration. However, the time savings alone will allow advanced design teams to define and analyze more configurations earlier in the design cycle, resulting in much greater design visibility and with greater accuracy.

The general characteristics of flutter problems affecting the structural design of both subsonic and supersonic transport aircraft are discussed in relation to configuration constraints resulting from mission performance and environmental impact requirements. Combined analytical and experimental approaches employed in the assessment and solution of these problems are outlined. Included are discussions of the extensive application of automated procedures in the use of high-speed digital computers for flutter analysis and the dependence on highly sophisticated wind tunnel flutter model construction techniques to provide reliable experimental data. Illustrations of the application of design techniques to supersonic and subsonic aircraft are presented.

Machinery maintenance programs based on vibration trend monitoring have been successfully used in several applications. In essence, these programs rely on the interpretation of changing machinery vibration patterns to diagnose developing defects and subsequently define a relative condition index. This information, along with other operating parameters and constraints, is then used to draw up meaningful maintenance schedules. This paper, after a brief review of the vibration monitoring programs in use by the Sea Element of the Canadian Armed Forces, discusses the operational problems that arise in the definition of a vibration health monitoring program for a 750 kW gas turbine generator. It describes in detail the rationale for selecting the location of points where measurements should be made and lists the mechanical components which influence the vibration pattern at each station.

Recent advances in the design and development of motion simulators, visual display systems, artifical force producers, and computer capability have enhanced the effectiveness of ground-based simulators in the design process. At Northrop, a systematic improvement in simulator subsystems has resulted in the existence of the Northrop Large Amplitude Three-Axis Flight Simulator which has 6 degrees of freedom. The simulator is a significant tool in the design of flight control systems, particularly in today's environment where the aerospace industry is attempting to extend the performance envelopes of its products through the use of nonconventional configurations and radical flight control system concepts. Some examples are presented in this paper to demonstrate the contribution that the Northrop Large Amplitude Three-Axis Flight Simulator is making in the YF-17 program to the solution of current flight control system problems that are not soluble by analytical techniques.

Predominant features of sound signatures can be related back to operational events occurring within components both for normal and failure mode operations. Engineering analysis permits establishment of quantized go, no-go, or caution parameters necessary to make readiness assessment decisions. The “Structure Borne Acoustics” test technique presented in this paper has outstanding potential for this work. Reliability includes accurate detection and diagnosis of the maximum number of faults, with an absolute minimum false alarm rate. Jet engine-bearing monitoring is one example of successful application.

A technique is discussed for generating diagnostic information from the vibration signature of machinery in the high-frequency range (up to 100 kHz). The signal generation mechanism is discussed, as well as the diagnostically significant characteristics of the data and a method of extracting this information. Two specific cases are presented utilizing the techniques to illustrate its suitability for many of the common problems encountered in machinery.

This paper presents the composite exceedance method as an alternative to the more costly broadband power spectral density (PSD) analysis which is the standard method of acoustic signature analysis for rotating machinery. The composite exceedance is superior to the PSD analysis in that the computational procedure is straightforward and effective without the use of Fourier Transforms and, therefore, lends itself to simple programming, and the information extracted from the vibration data is represented in one master plot, permitting direct evaluation of all g peak levels encountered in terms of the number of occurrences above which they exceed a given level of acceleration. The sensitivity of anomaly detection by the proposed method has been demonstrated in a number of actual cases, one of which is discussed. The data collection methodology and philosophy of the method as they relate to narrow-band Gaussian random processes are also considered.

A unique propulsion system is being developed for the Space Shuttle Orbiter utilizing airbreathing engines to provide a means for horizontal flight testing and ferrying the Orbiter within the contiguous United States. Primarily, the NASA was concerned with ferrying the Orbiter from manufacturing site to launch site, but it was also recognized that on some occasions weather conditions or other emergency situations might dictate landing at alternate sites when returning from space missions. These situations would also require subsequent takeoff and ferry to a launch site. To fulfill these objectives, certain ground rules and criteria were selected, consisting primarily of takeoff capability on a hot day from a runway 10,000 feet in length, a 423 nautical mile minimum cruise range, engine out cruise ceiling of 10,000 feet, the use of existing engines, and an installation that was easily attached and removed from the Orbiter vehicle.

The Techroll joint is a constant-volume, fluid-filled bearing configured with a pair of rolling convolutes that permits omniaxis deflection of a solid rocket motor nozzle. The fluid-filled bearing is pressurized by nozzle ejection loads and serves as both the movable nozzle bearing and nozzle seal. The Techroll seal is made of a fabric-reinforced elastomeric composite material and does not require complex manufacturing processes or tight tolerances. The Techroll joint has undergone development under U.S. Air Force, Navy, and Army funding and has been demonstrated on six separate contracts involving 12 different designs. This paper introduces the concept, presents four of the designs, and summarizes the performance characteristics of seven designs.

A special subscale, pintle-mounted gas generator was developed by the Army Advanced Ballistic Missile Defense Agency. It was used to comparatively evaluate the thrust vector control systems which might be used in conjunction with pintle-controlled interceptor motors. The two thrust vector control systems which have been evaluated to date are: the Gimballed, Supersonic Splitline Thrust Vector Control System and the Techroll Movable Nozzle Thrust Vector Control System. These evaluations were carried out under simulated altitude conditions with the gas generator operating in a boost and a sustain mode as part of the duty cycle. This paper will discuss the design of this Thrust Vector Control Gas Generator, motor fabrication, its multiple ignition system, the thrust vector control systems, test objectives, test procedures, and test results.

Apollo 17 ended the most successful application of rocket propulsion systems in man's history. A total of 23 developmental and manned operational flights were made. Seven hundred and sixty-three spacecraft rocket engines were flown in the program. Over 6 h of manned rocket flights were logged by the spacecraft propulsion systems and approximately one million rocket engine firings were made. One engine failure was encountered on an early unmanned flight as a result of a failure in the guidance programmer which caused the engine to operate in a manner known to cause failures. Numerous operational problems and malfunctions were observed; however, system and component redundancy prevented loss of mission objectives and never jeopardized crew safety. Performance of all systems was usually nominal and most problems were merely nuisances. This paper will present some highlights of Apollo propulsion performance and will provide a bibliography of all flight results.

A reverberant acoustic field is frequently used in ground testing when it is desired to generate a spacecraft vibration environment similar to that encountered in flight. The sound-pressure level specified to accomplish this is usually the same as the maximum expected flight fluctuating pressure level. Experience has shown this to be an inadequate way to specify reverberant ground test levels because of basic differences in the characteristics of the reverberant and flight fluctuating pressure fields. This paper reviews pertinent information on this subject that has recently been obtained from large upperstage space vehicles.

The need for evaluating and optimizing airframes of advanced aircraft configurations with exceptional speed and accuracy has resulted in the development of highly sophisticated computerized techniques. Sensitivity of these programs to advanced materials, construction types, aeroelasticity, structural dynamics, configuration geometry, airloads, missions, and performance has all but obsoleted the statistical approach to the problem solution. The competitive nature of the field has also placed unusually severe demands on calendar time available for such evaluations. This has resulted in the development of integrated analytical computer programs that have the required sensitivity and rapid turnaround time to face the competitive nature of today's environment.