Search Results

An evolving aircraft synthesis simulation environment which offers improvements to existing methods at multiple levels of a design process is described in this paper. As design databases become obsolete due to the introduction of new technologies and classes of vehicles and as sophisticated analysis codes are often too computationally expensive for iterative applications, the design engineer may find a lack of usable information needed for decision making. Within the environment developed in this paper, rapid sensitivity analysis is possible through a unique representation of the relationship between fundamental design variables and system objectives. The combined use of the Design of Experiments and Response Surface techniques provides the ability to form this design relationship among system variables and target values, which is termed design-oriented in nature.

The growth of international markets as well as business partnerships between U.S. and Asian-based firms has lead to an increased interest in an economically viable business jet capable of supersonic cruise and trans-Pacific range with one stop over (or non-stop trans-Atlantic range)1. Such an aircraft would reduce the travel time to these regions by as much as 50% by increasing cruise Mach number from roughly 0.85 to 2.0. In response to this interest, the 1996 AIAA / United Technologies / Pratt & Whitney Individual Undergraduate Design Competition has issued a Request for Proposal for the conceptual design of a supersonic cruise business jet. The design of this aircraft considered both performance and economic issues in the conceptual design phase. Through the use of Response Surface Methodology (RSM) and Design of Experiments (DoE) techniques, the aerodynamics of this vehicle were modeled and incorporated into an aircraft sizing code, FLOPS.

The desire of achieving faster cruise speed for rotorcraft vehicles has been around since the inception of the helicopter. Many unconventional concepts have been considered and researched such as the advanced tilt rotor with canards, the tilt-wing, the folding tiltrotor, the coaxial propfan/folding tiltrotor, the variable diameter tiltrotor, and the stopped rotor/wing concept, in order to fulfill this goal. The most notable program which addressed the technology challenges of accomplishing a high speed civil transport mission is the High Speed Rotorcraft Concept (HSRC) program. Among the long list of potential configurations to fulfill the HSRC intended mission, the stopped rotor/wing is the least investigated due to the fact that the existing rotorcraft synthesis codes cannot handle this type of vehicle. In order to develop such a tool, a designer must understand the physics behind this unique concept.

This paper outlines work performed by the Aeronautical Systems Division of the Aerospace and Transportation Laboratory at the Georgia Tech Research Institute (GTRI). The paper provides limited, but pertinent information relative to the technical viability of a tiltwing configurations as civil powered-lift aircraft. Emphasis has been placed on identifying the complexity differences with tiltrotor and helicopter configurations. Complexity differences normally impact both acquisition and/or operating and support costs, although specific cost estimates are not presented.

In recent years, the residential and transportation sectors have made significant strides in reducing energy consumption, mainly by focusing efforts on low-hanging fruit in each sector independently. This independent viewpoint has been successful in the past because the user needs met and resources consumed in each sector have been clearly distinct. However, the trend towards vehicle electrification has blurred the boundary between the sectors. With both the home and vehicle now relying upon the same energy source, interactions between the systems can no longer be neglected. For example, when tiered utility pricing schemes are considered, the energy consumption of each system affects the cost of the other. In this paper, the authors present an integrated Home-Vehicle Simulation Model (HVSM), allowing the designer to take a holistic view.

Hybrid-electric powertrains for passenger vehicles and light trucks are generally being designed with two different configurations described as follows: The Toyota Hybrid System, THS-II, implemented in the 2004 Prius, the Lexus 400-H, and the Ford Hybrid Escape, is a power-split approach involving two electric machines and an internal combustion engine (ICE) mechanically coupled by a three-shaft planetary gear train. The second leading approach is a parallel hybrid-electric powertrain that generally includes a single electric machine and an ICE with a mating multi-ratio transmission. These parallel configurations are further divided as weak parallel and strong parallel. Honda uses a weak parallel powertrain in their Insight and Hybrid Civic. At Georgia Tech a strong (full), split-parallel hybrid powertrain has been implemented in a Ford Explorer. The vehicle is referred to as the Model GT.

This paper describes a machine to quarry construction material, sinter walls, and assemble future space station modules. In prior work, we explored the solar energy requirements to build a 50m diameter, 50m high, cylindrical module out of pulverized rock from a Near-Earth Object, using tailored radio wave fields. In this paper, we describe the issues in the conceptual design of the robotic construction machines. The 4-legged Rock breaker is designed to fit the payload bay of a modern heavy-lift booster to reach Low Earth Orbit, and primary solar-sail propulsion for most of its journey. It uses beamed microwave energy for its cutting operations. Rotating, telescoping arms use integrated laser/plasma jet cutter arrays to dig trenches in spiral patterns which will form blocks of material. Cut blocks are sent into a toroidal cloud of material for use in the force field tailoring for automatic module formation.

This paper presents a quantitative process to track the progress of technology developments within NASA’s Vehicle Systems Program (VSP) as implemented on a Supersonic Business Jet (SBJ). The process, called the Technology Metric Assessment and Tracking (TMAT) process, accounts for the temporal aspects of technology development programs such that technology portfolio assessments, in the form of technological progress towards VSP sector goals, may be tracked and assessed. Progress tracking of internal research and development programs is an essential element to successful strategic endeavors and justification of the pursuit of capital projects [1].

A design process is formulated and implemented for the taxonomy selection and system-level optimization of an Efficient Multi-Mach Aircraft Current Technology Concept and an Advanced Concept. Concept space exploration of taxonomy alternatives is performed with multi-objective genetic algorithms and a Powell’s method scheme for vehicle optimization in a multidisciplinary modeling and simulation environment. A dynamic sensitivity visualization analysis tool is generated for the Advanced Concept with response surface equations.

A procedure is developed for evaluating various candidates for thermal control in the orbiting space station. Candidates for acquisition, transport and rejection are considered. For example, thermal rejection candidates include heat pipe radiators, high capacity heat pipe radiators and liquid droplet raditors. A computer program has been developed which computes subsystem and total system weights, volumes, powers and costs for a system consisting of selected acquisition, transport and rejection candidates. The program user is also able to select mission parameters such as duration, resupply interval, thermal loads, transport distance, acquisition temperature and rejection temperature. Simulation models are included in the program which allow the user to change candidate designs. For example, for a high capacity heat pipe radiator the user may change working fluid, materials, radiator temperature, radiator geometry, surface emissivity and surface absorptivity.

The quantification of aircraft survivability in modern battlefield environments is a complex mathematical problem. In general, consideration must be given to the quantification of aircraft vulnerability to individual weapon systems, single encounter aircraft survivability, and the mathematical mapping of single encounter aircraft survivability into mission attrition. A methodology for quantifying the impacts of electronic warfare (EW) upon aircraft survivability is realized by the General Effectiveness Methodology (GEM) which is based upon a hierarchy of computer models. This paper describes this hierarchy of computer simulation tools which extensively employs probability theory to estimate the various engagement events such as aircraft detection, acquisition, missile launch, missile intercept, and probability of aircraft kill.

A technique is proposed for examining complex behaviors in the “pilot - vehicle - operational conditions” system using an autonomous situational model of flight. The goal is to identify potentially critical flight situations in the system behavior early in the design process. An exhaustive set of flight scenarios can be constructed and modeled on a computer by the designer in accordance with test certification requirements or other inputs. Distinguishing features of the technique include the autonomy of experimentation (the pilot and a flight simulator are not involved) and easy planning and quick modeling of complex multi-factor flight cases. An example of mapping airworthiness requirements into formal scenarios is presented. Simulation results for various flight situations and aircraft types are also demonstrated.

An affordable technique is proposed for fast quantitative analysis of aerobatics and other complex flight domains of highly maneuverable aircraft. A generalized autonomous situational model of the “pilot (automaton) – vehicle – operational environment” system is employed as a “virtual test article”. Using this technique, a systematic knowledge of the system behavior in aerobatic flight can be generated on a computer, much faster than real time. This information can be analyzed via a set of knowledge mapping formats using a 3-D graphics visualization tool. Piloting and programming skills are not required in this process. Possible applications include: aircraft design and education, applied aerodynamics, flight control systems design, planning and rehearsal of flight test and display programs, investigation of aerobatics-related flight accidents and incidents, physics-based pilot training, research into new maneuvers, autonomous flight, and onboard AI.

A hybrid electric vehicle (HEV) simulation has been developed for an electric-assist parallel configuration vehicle, at the University of Tennessee, Knoxville. The model was developed in MATLAB/SIMULINK using ADVISOR, a HEV simulation model developed by the National Renewable Energy Laboratory. The Neon simulation model implements a power control strategy using throttle position as the primary input. It incorporates other features of HEV power control such as battery regeneration and regenerative braking. A practical way of battery modeling is incorporated into this model. The model also simulates the vehicle operation as a pure electric vehicle (EV) or as a conventional vehicle (heat engine only). By using the Neon model, the performance of the vehicle has been analyzed using parametric analysis of the vehicle components and power control parameters. Recommendations are given for improving the design based on the simulation results.

The objective of this paper is to develop a generalized loss management model to account for the usage of thermodynamic work potential in vehicles of any type. The key to accomplishing this is creation of a differential representation for vehicle loss as a function of operating condition. This differential model is then integrated through time to obtain an analytical estimate for total usage (and loss) of work potential consumed by each loss mechanism present during vehicle operation. The end result of this analysis is a better understanding of how the work potential initially present in the fuel, batteries, etc. is partitioned amongst all losses relevant to the vehicle's operation. The loss partitioning estimated from this loss management model can be used in conjunction with cost accounting systems to gain a better understanding of underlying drivers on vehicle manufacturing and operating costs.

System effectiveness has become the prime metric for the evaluation of military aircraft. As such, it is the designer's goal to maximize system effectiveness. Industry documents indicate that all future military aircraft will incorporate signature reduction as an attempt to improve system effectiveness. Today's operating environments demand low observable aircraft which are able to reliably eliminate valuable, time critical targets. Thus, it is desirable to be able to evaluate the signatures of a vehicle, as well as the influence of signatures on the systems effectiveness of a vehicle. Previous studies have shown that shaping of the vehicle is one of the most important contributors to radar cross section and must be considered from the very beginning of the design process. This research strives to meet these needs by developing a parametric geometry radar cross section prediction tool.

The design of hypersonic vehicles is influenced by tightly coupled interactions between aerodynamics, propulsion, and structures. Therefore, in the conceptual design phases, the identification and mitigation of potential problem areas and disciplinary interrelations are critical. Although the multidisciplinary character of hypersonic designs is well known, research in hypersonics is primarily focused on the isolated disciplines with side notes on the interactions. The designer has to integrate all the disciplinary information and create a successful system. This integration is a tedious and elaborate process involving time-consuming iterations. This paper proposes a new approach and entails the creation of Response Surface Equations from the various constituent disciplines considered. This method allows to quickly assess the implication of design decisions at the top level using the multiple disciplinary meta-models.

A multidisciplinary design study considering the impact of Active Aeroelastic Wing (AAW) technology on the structural wing weight of a lightweight fighter concept is presented. The study incorporates multidisciplinary design optimization (MDO) and response surface methods to characterize wing weight as a function of wing geometry. The study involves the sizing of the wing box skins of several fighter configurations to minimum weight subject to static aeroelastic requirements. In addition, the MDO problem makes use of a new capability, trim optimization for redundant control surfaces, to accurately model AAW technology. The response surface methodology incorporates design of experiments, least squares regression, and makes use of the parametric definition of a structural finite element model and aerodynamic model to build response surface equations of wing weight as a function of wing geometric parameters for both AAW technology and conventional control technology.

In today’s atmosphere of lower U.S. defense spending and reduced research budgets, determining how to allocate resources for research and design has become a critical and challenging task. In the area of aircraft design there are many promising technologies to be explored, yet limited funds with which to explore them. In addition, issues concerning uncertainty in technology readiness as well as the quantification of the impact of a technology (or combinations of technologies), are of key importance during the design process. The methodology presented in this paper details a comprehensive and structured process in which to explore the effects of technology for a given baseline aircraft. This process, called Technology Impact Forecasting (TIF), involves the creation of a forecasting environment for use in conjunction with defined technology scenarios. The advantages and limitations of the method will be discussed, as well its place in an overall methodology used for technology infusion.

A key issue in complex systems design is measuring the ‘goodness’ of a design, i.e. finding a criterion through which a particular design is determined to be the ‘best’. Traditional choices in aerospace systems design, such as performance, cost, revenue, reliability, and safety, individually fail to fully capture the life cycle characteristics of the system. Furthermore, current multi-criteria optimization approaches, addressing this problem, rely on deterministic, thus, complete and known information about the system and the environment it is exposed to. In many cases, this information is not be available at the conceptual or preliminary design phases. Hence, critical decisions made in these phases have to draw from only incomplete or uncertain knowledge. One modeling option is to treat this incomplete information probabilistically, accounting for the fact that certain values may be prominent, while the actual value during operation is unknown.