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At least 235 records · Page 13

Dynamic and structural control utilizing smart materials and structures

An account is given of several novel 'smart material' structural control concepts that are currently under development. The thrust of these investigations is the evolution of intelligent materials and structures superceding the recently defined variable-geometry trusses and shape memory alloy-reinforced composites; the substances envisioned will be able to autonomously evaluate emergent environmental conditions and adapt to them, and even change their operational objectives. While until now the primary objective of the developmental efforts presently discussed has been materials that mimic biological functions, entirely novel concepts may be formulated in due course.

Rogers, C. A.↗

Runway Exit Designs for Capacity Improvement Demonstrations. Phase 1: Algorithm Development

A description and results are presented of a study to locate and design rapid runway exits under realistic airport conditions. The study developed a PC-based computer simulation-optimization program called REDIM (runway exit design interactive model) to help future airport designers and planners to locate optimal exits under various airport conditions. The model addresses three sets of problems typically arising during runway exit design evaluations. These are the evaluations of existing runway configurations, addition of new rapid runway turnoffs, and the design of new runway facilities. The model is highly interactive and allows a quick estimation of the expected value of runway occupancy time. Aircraft populations and airport environmental conditions are among the multiple inputs to the model to execute a viable runway location and geometric design solution. The results presented suggest that possible reductions on runway occupancy time (ROT) can be achieved with the use of optimally tailored rapid runway designs for a given aircraft population. Reductions of up to 9 to 6 seconds are possible with the implementation of 30 m/sec variable geometry exits.

Trani, A. A.↗

V/STOL gets a lift

The concept of a supersonic STOVL that could offer enhanced mission capability, survivability, operational flexibility, and utility over conventional aircraft is presented. Emphasis is currently on design studies, CFD work, small- and large-scale wind tunnel tests, simulation activities, flight experiments, and ground environment experiments. Propulsion system technology centers about the adaptation of existing or off-the-shelf engines. Concepts under study include separate flow in hover, gas-driven lift fan, and shaft-driven lift fan. NASA is examining generic valve and ducting configurations with airflow at ambient temperature and at temperatures up to 1000 F to gather pressure loss and heat transfer data. Advanced civil rotorcraft technologies examined include high-efficiency/dual-mode components such as torque converters; lightweight, quiet transmissions; and variable geometry power turbines; along with dual-function or convertible engines.

Biesiadny, Tom↗

Dynamic, High-Temperature, Flexible Seals

Dynamic, flexible ceramic seals developed for use at high temperatures in high-performance, variable-geometry, hypersonic airplane engines. Stacked ceramic wafers pressed against stationary sidewall by pressure in one or more metal bellows. Seals also used in hypersonic engines, two-dimensional convergent/divergent and vectored-thrust exhaust nozzles, airframes of reentry vehicles, casings of rocket motors furnaces, and other applications.

Steinetz, Bruce M.↗

Three-dimensional simulation of a translating strut inlet

A three-dimensional Navier-Stokes code is used to numerically simulate the flow through a translating strut scramjet inlet. The inlet has variable geometry for efficient operation over a wide speed range. Overall flow-field features such as the corner flow, topwall separation, shockwave coalescence, cowl pressure increase, and flow distortion at the throat are investigated. Comparisons are made with experimental results to provide for the assessment of the present analysis. Effects of boundary-layer ingestion on the overall flow features are also investigated.

Singh, D. J.↗

Kinematic analysis of generalized adaptive trusses

Adaptive trusses offer the greatest stiffness and strength for a given weight of any articulated structure or mechanism. Because of this, there are many potential extraterrestrial applications of these variable-geometry trusses, including serpentine manipulators, payload isolation, tracking, pointing and docking mechanisms, and gimbals. All of these applications will require the ability to precisely control the kinematic parameters of the mechanism, including position, velocity, and acceleration. This paper explores the fundamental nature of adaptive trusses by examining the basic truss elements or unit cells. A general method for analyzing forward and inverse motion of all the basic truss units is presented, followed by a more efficient formulation for the octahedral unit cell. Finally, general closed-form techniques are presented for finding velocity, acceleration, and all higher derivatives of truss motion.

Tidwell, Paul H.↗

High-Temperature, Flexible, Pressure-Assisted Brush Seal

Ceramic-fibers brush and integral spring clip block hot, engine flows. High-temperature, pressure-assisted brush seal installed in movable panel in advanced hypersonic engine. Seal prevents flow of hot engine gas from penetrating gap between movable panel and adjacent stationary panel. Potential applications include sealing gaps in variable-geometry two-dimensional turbojet exhaust nozzles or sealing control surface gaps of hypersonic vehicles. Ceramic brush seals also used as structural seals in high-temperature furnaces or advanced ceramic heat exchangers.

Steinetz, Bruce M.↗

TBD(exp 3)

When asked by the Aeronautical Engineering staff to design a viable supersonic commercial transport, most of the students were well aware that Boeing, McDonnell Douglas, and other aircraft companies had been studying a cadre of transports for more than 30 years and had yet to present a viable aircraft. In the spirit of aviation progress and with much creative license, the TBD design team spearheaded the problem with the full intention of presenting a marketable high speed civil transport in spring of 1992. The project commenced with various studies of future market demands. With the market expansion of American business overseas, the airline industry projects a boom of over 200 million passengers by the year 2000. This will create a much higher demand for time efficient and cost effective inter-continental travel; this is the challenge of the high speed civil transport. The TBD(exp 3), a 269 passenger, long-range civil transport was designed to cruise at Mach 3.0 utilizing technology predicted to be available in 2005. Unlike other contemporary commercial airplane designs, the TBD(exp 3) incorporates a variable geometry wing for optimum performance. This design characteristic enabled the TBD(exp 3) to be efficient in both subsonic and supersonic flight. The TBD(exp 3) was designed to be economically viable for commercial airline purchase, be comfortable for passengers, meet FAR Part 25, and the current FAR 36 Stage 3 noise requirements. The TBD(exp 3) was designed to exhibit a long service life, maximize safety, ease of maintenance, as well as be fully compatible with all current high-traffic density airport facilities.

Baughan, Jim↗

The Edge supersonic transport

As intercontinental business and tourism volumes continue their rapid expansion, the need to reduce travel times becomes increasingly acute. The Edge Supersonic Transport Aircraft is designed to meet this demand by the year 2015. With a maximum range of 5750 nm, a payload of 294 passengers and a cruising speed of M = 2.4, The Edge will cut current international flight durations in half, while maintaining competitive first class, business class, and economy class comfort levels. Moreover, this transport will render a minimal impact upon the environment, and will meet all Federal Aviation Administration Part 36, Stage III noise requirements. The cornerstone of The Edge's superior flight performance is its aerodynamically efficient, dual-configuration design incorporating variable-geometry wingtips. This arrangement combines the benefits of a high aspect ratio wing at takeoff and low cruising speeds with the high performance of an arrow-wing in supersonic cruise. And while the structural weight concerns relating to swinging wingtips are substantial, The Edge looks to ever-advancing material technologies to further increase its viability. Heeding well the lessons of the past, The Edge design holds economic feasibility as its primary focus. Therefore, in addition to its inherently superior aerodynamic performance, The Edge uses a lightweight, largely windowless configuration, relying on a synthetic vision system for outside viewing by both pilot and passengers. Additionally, a fly-by-light flight control system is incorporated to address aircraft supersonic cruise instability. The Edge will be produced at an estimated volume of 400 aircraft and will be offered to airlines in 2015 at $167 million per transport (1992 dollars).

Agosta, Roxana↗

High-speed transpacific passenger flight

The design task of high-speed passenger flight across the Pacific Ocean was addressed by four design teams of eight students each. Two teams examined hypersonic flight (Mach greater than 5) and two teams studied supersonic flight (Mach = 3). The specific task of the aircraft was to transport at least 250 passengers 6500 nautical miles while operating from airport runways of 15,000 feet. Four design concepts evolved; the supersonic designs--one a variable-sweep oblique wing and the other a cranked-arrow wing--use conventional turbine engines and liquid hydrocarbon fuels. The two hypersonic configurations, one with a variable-sweep wing and the other with a fixed, swept-wing planform, employ methane fueled, variable-cycle turbojet/ramjet propulsion systems. Both supersonic aircraft weigh less than 700,000 lbs at takeoff, while the variable-geometry hypersonic airplane is the heaviest at 1,100,000 lbs and weighs 170,000 lbs more than the fixed-wing hypersonic design. All the conceptual designs are shown to perform the transport mission, although development and operating cost estimates favor the supersonic designs over the hypersonic configurations.

Source record↗

Analysis of ram-jet engine performance including effects of component changes

Calculated design-point performance of ram-jet engines using JP-4 fuel is presented for a wide range of engine total-temperature ratios and combustion-chamber-inlet Mach numbers for flight numbers from 1.5 to 4.0. The results include engine thrust, drag, fuel consumption, and area ratios. Data are also presented to illustrate the sensitivity of the results to variations in the assumed component parameters. A brief comparison is included between fixed-and variable-geometry engines.

Weber, Richard J↗

Preliminary design of nine high speed civil transports

Sixty senior design students at Cal Poly, SLO have completed a year-long project to design the next generation of High Speed Civil Transports (HSCT). The design process was divided up into three distinct phases. The first third of the project was devoted entirely to research into the special problems associated with an HSCT. These included economic viability, airport compatibility, high speed aerodynamics, sonic boom minimization, environmental impact, and structures and materials. The result of this research was the development of nine separate Requests for Proposal (RFP) that outlined reasonable yet challenging design criteria for the aircraft. All were designed to be technically feasible in the year 2015. The next phase of the project divided the sixty students into nine design groups. Each group, with its own RFP, completed a Class 1 preliminary design of an HSCT. The nine configurations varied from conventional double deltas to variable geometry wings to a pivoting oblique wing design. The final phase of the project included a more detailed Class 2 sizing as well as performance and stability and control analysis. Cal Poly, San Luis Obispo presents nine unique solutions to the same problem: that of designing an economically viable, environmentally acceptable, safe and comfortable supersonic transport.

Sandlin, Doral↗

Experimental studies of transonic flow field near a longitudinally slotted wind tunnel wall

The results of detailed parametric experiments are presented for the near-wall flow field of a longitudinally slotted transonic wind tunnel. Existing data are reevaluated and new data obtained in the Langley 6- by 19-inch Transonic Wind Tunnel are presented and analyzed. In the experiments, researchers systematically investigate many pertinent wall-geometry variables such as the wall openness and the number of slots along with the free stream Mach number and model angle of attack. Flow field surveys on the plane passing through the centerline of the slot were conducted and are presented. The effects of viscosity on the slot flow are considered in the analysis. The present experiments, combined with those of previous investigations, give a more complete physical characterization of the flow near and through the slotted wall of a transonic wind tunnel.

Everhart, Joel L.↗

Rich burn combustor technology at Pratt and Whitney

The topics covered include the following: near term objectives; rich burn quick quench combustor (RBQC); RBQC critical technology areas; cylindrical RBQQ combustor rig; modular RBQQ combustor; cylindrical rig objectives; quench zone mixing; noneffusive cooled liner; variable geometry requirements; and sector combustor rig.

Lohmann, Robert P.↗

Troika partnership model for licensing NASA-LaRC technologies

The Technology Applications (TAG) Group at NASA Langley Research Center has currently more than 100 technologies that are ripe for commercialization. These technologies are categorized by various sectors including: Energy and the Environment; Materials and Structures; Manufacturing; Information and Communications; Transportation, and Medical/Sensor/ Instrumentation. A requirement that TAG has placed on all technologies ready for licensing is that there will be some university involvement in the technology transfer or knowledge transfer process. This model involves the troika of government (LaRC), industry and university. A number of variations on the Troika Partnership Model (TPM) were developed as a part of this ASEE Fellowship. Furthermore, five technologies were identified - three of which industrial interests have been matched: LaRC-SI, a thermoplastic that can be used as a coating; Variable Geometry Truss Manipulator Arm that can be used for nuclear waste clean -up and as scaffolding; and ADAPT (Approach to Data Management, Archive Protection, and Transmission) is a technology that could be used for a variety of multi-tasking operations over the Internet. The aim of this work was to initiate a Space Act Agreement (SAA) for at least one of these technologies using one of the options of the TPM. A preliminary partnership agreement using the SAA is currently being negotiated with NASA-LaRC, VPI and Virginia Power for the LaRC-SI thermoplastic that will be used as a coating.

Maclin, Arlene P.↗

Haptic interfaces: Hardware, software and human performance

Virtual environments are computer-generated synthetic environments with which a human user can interact to perform a wide variety of perceptual and motor tasks. At present, most of the virtual environment systems engage only the visual and auditory senses, and not the haptic sensorimotor system that conveys the sense of touch and feel of objects in the environment. Computer keyboards, mice, and trackballs constitute relatively simple haptic interfaces. Gloves and exoskeletons that track hand postures have more interaction capabilities and are available in the market. Although desktop and wearable force-reflecting devices have been built and implemented in research laboratories, the current capabilities of such devices are quite limited. To realize the full promise of virtual environments and teleoperation of remote systems, further developments of haptic interfaces are critical. In this paper, the status and research needs in human haptics, technology development and interactions between the two are described. In particular, the excellent performance characteristics of Phantom, a haptic interface recently developed at MIT, are highlighted. Realistic sensations of single point of contact interactions with objects of variable geometry (e.g., smooth, textured, polyhedral) and material properties (e.g., friction, impedance) in the context of a variety of tasks (e.g., needle biopsy, switch panels) achieved through this device are described and the associated issues in haptic rendering are discussed.

Srinivasan, Mandayam A.↗

A CFD Study of Turbojet and Single-Throat Ramjet Ejector Interaction

Supersonic ejector-diffuse systems have application in driving an advanced airbreathing propulsion system, consisting of turbojet engines acting as the primary and a single throat ramjet acting as the secondary. The turbojet engines are integrated into the single throat ramjet to minimize variable geometry and eliminate redundant propulsion components. The result is a simple, lightweight system that is operable from takeoff to high Mach numbers. At this high Mach number (approximately Mach 3.0), the turbojets are turned off and the high speed ramjet/scramjet take over and drive the vehicle to Mach 6.0. The turbojet-ejector-ramjet system consists of nonafterburning turbojet engines with ducting canted at 20 degrees to supply supersonic flow (downstream of CD nozzle) to the horizontal ramjet duct at a supply total pressure and temperature. Two conditions were modelled by a 2-D full Navier Stokes code at Mach 2.0. The code modelled the Fabri choke as well as the non-Fabri non critical case, using a computational throat to supply the back pressure. The results, which primarily predict the secondary mass flow rate and the mixed conditions at the ejector exit were in reasonable agreement with the 1-D cycle code (TBCC).

Chang, Ing↗

A Scalable Distributed Approach to Mobile Robot Vision

This paper documents our progress during the first year of work on our original proposal entitled 'A Scalable Distributed Approach to Mobile Robot Vision'. We are pursuing a strategy for real-time visual identification and tracking of complex objects which does not rely on specialized image-processing hardware. In this system perceptual schemas represent objects as a graph of primitive features. Distributed software agents identify and track these features, using variable-geometry image subwindows of limited size. Active control of imaging parameters and selective processing makes simultaneous real-time tracking of many primitive features tractable. Perceptual schemas operate independently from the tracking of primitive features, so that real-time tracking of a set of image features is not hurt by latency in recognition of the object that those features make up. The architecture allows semantically significant features to be tracked with limited expenditure of computational resources, and allows the visual computation to be distributed across a network of processors. Early experiments are described which demonstrate the usefulness of this formulation, followed by a brief overview of our more recent progress (after the first year).

Kuipers, Benjamin↗