Christopher P. Frank

A Design Space Exploration Methodology to Support Decisions under Evolving Requirements’ Uncertainty and its Application to Suborbital Vehicles

This research aims at supporting the development of emerging markets such as suborbital vehicles by establishing a methodology that enables a broad design space exploration at a conceptual level to select the best concepts against unclear objectives and under evolving requirements’ uncertainty. To bridge the gap in current design space exploration techniques, a new architecture-based morphological matrix is developed to generate all feasible concepts. Then, a new evolutionary algorithm based on architecture fitness is implemented that drives multi-objective optimization algorithms to simultaneously compare and optimize all configurations. To support decisions under evolving uncertainty, requirements are modeled by membership functions and are propagated using fuzzy set theory. The new methodology is expected to reduce the risk of missing promising concepts and help designers with challenging go/no-go decisions. It will also provide more flexibility by allowing decision makers to develop scenarios and support more analytic decisions.

A Conceptual Design Framework for Performance, Life-Cycle Cost, and Safety Evaluation of Suborbital Vehicles

Recent technological advancements along with a growing demand for space tourism is supporting the development of new manned suborbital vehicles. This market is characterized yet by a lack of both an optimized baseline and clearly-defined requirements so that a methodology that explores the entire design space is needed. In particular, this research focuses on the development of a multi-objective design framework that provides the capabilities to rapidly evaluate the flying, economic, and safety performance of all suborbital vehicles at a conceptual level. For development purposes, the modeling and simulation environment is broken down into six modules: weight/size, aerodynamics, trajectory, propulsion, economics, and safety. By leveraging empirical models, physics-based approaches, and surrogate modeling techniques, it enables the rapid and parametric assessment and optimization of a multitude of design concepts. Finally, it is the first environment of this sort to provide economic and safety assessment capabilities for all architectures of suborbital vehicles.

An Evolutionary Multi-Architecture Multi-Objective Optimization Algorithm for Design Space Exploration

The increasing complexity of future aerospace vehicles gives rise to large combinatorial spaces of possible configurations for which no baseline has been established. To ensure that the best concept is selected, the entire design space has to be explored. In addition, the presence of evolving requirements’ uncertainty due to the lack of experience and established regulations requires flexible decision-making techniques to be implemented to alleviate the risks inherent to the launch of new programs. To address these challenges, a new evolutionary multi-architecture multi-objective optimization algorithm is presented. The proposed approach allows designers to efficiently and exhaustively generate variable-oriented architectures that can be further optimized and compared. It provides a dynamic decision-making environment able to identify trends and trade-offs, while also prioritizing designs. The application of the proposed methodology on suborbital vehicles highlights key promising technological enablers, which can be leveraged to design high-performance and robust concepts.

An Aircraft Development Methodology Aligning Design and Strategy to Support Key Decision Making

Commercial aviation is currently a very financially attractive sector for aircraft manufacturers, with strong growth and very positive outlooks. While the sector is very profitable, aerospace programs are considered to be some of the most costly and risky projects among businesses. A lot of money has to be committed to the development of a single vehicle, exposed to a broad range of significant risks, and to harsh competition. Past examples illustrate the economic failure of great engineering programs due to an uncontrolled exposure to such risks. The difficulty of making good decisions does not only stem from the aleatory aspect of the performance of an airplane and the health of the market. The multiplicity of business divisions involved in the full life-cycle of an aircraft program complicates the task of top managers. In order to plan the aircraft development program, a manufacturer does not only need its R&D division, but also its marketing and sales division and its financial division. These divisions determine the program budgeting, and perform some financial analyses and optimizations. Strategic executives then make the final decisions on the project. This paper addresses shortcomings of current aircraft design, by providing decision makers with a methodology that will enable them to collect the information they need, to integrate the different business divisions in order to align them towards a single company objective, and to make risk-aware decisions in an uncertain multi-objective environment.

Preliminary Design of a New Hybrid and Technology Innovative Suborbital Vehicle for Space Tourism

The general enthusiasm aroused by space tourism combined with the great technological achievement of Scaled Composites with the SpaceShipOne in 2004 initiated a new era: suborbital space tourism. As of today, most of the vehicles have been designed for performance, combining the most advanced technologies from both aeronautics and astronautics. Nevertheless, in order to become viable, vehicles must be safe enough to carry paying passengers and they must match the increasing demand. Thus, the implementation of a new design process based on adapted requirements led to a new vehicle. The latter is mainly powered by newly designed hybrid rocket engines but it also makes use of turbofans for the first segment of the climb and a safe powered landing. It takes-off and lands horizontally and is able to carry up to eight passengers and two pilots to an altitude of 109 km. The micro-gravity experienced by the passengers lasts approximately 4 minutes while the maximum load factor is reduced to 3.3 g in order to improve the passenger experience.

Design of an Improved Green Taxiing System Focused around the Landing Gear

New priorities in aircraft design are mapped out into an integrated holistic solution: an improved Green Taxiing system focused around the landing gear. The latter is streamlined through the use of fairings which also serve as landing gear doors. During the final approach phase, electric motors are used to rotate the wheels to the appropriate speed so as to reduce stress during touchdown. Energy, normally dissipated in heat, is collected in supercapacitors and used to power the aircraft subsystems for Green Taxiing. Titanium Matrix Composite is used to compensate additional weight. Super-capacitors power the aircraft during start and accelerations with engines turned off. For steady speed phase, the APU is used. An average 10 dB noise reduction is expected as well as a 4% decrease in operating costs and a 6% decrease in fuel consumption for a typical A320 mission.

Design Methodology for the Performance, Weight, and Economic Assessment of Chemical Rocket Engines

AbstractA design methodology is presented that supports the design of future aerospace rocket-powered vehicles. In particular, it provides the capabilities to rapidly evaluate the performance, weight, size, and lifecycle costs of all chemical rocket engines at a conceptual level. By leveraging cycle-based approaches and surrogate modeling techniques, the performance of all chemical rocket engines can be evaluated with an accuracy of 3%, whereas it divides the execution time by a factor of 105 compared to current physics-based models. New mass-estimating relationships are developed for estimating the weight and the size of solid engines with an improved accuracy compared to existing models. Physics-based models built around the key design drivers are used for the weight and size estimation of liquid and hybrid engines. Although existing cost-estimating relationships are used to evaluate the lifecycle costs of solid and liquid engines, a more physics-based model is developed for hybrid engines. Although it ...

An Integrated and Parametric Environment for Generation, Selection and Evaluation of New Architectures at a Conceptual Level: Application to the Environmental Control System

As aviation’s environmental impact becomes more and more worrying, designers are looking for innovative and more efficient subsystem architectures. To decrease design cost, the objective is to improve the requirements flow-down as well as their traceability throughout the design process. This work reviews previous work on the matter, and presents a systematic and rigorous methodology that helps the designers to generate, evaluate, compare and test architectures at a conceptual design level. The necessary tools and methods which have been implemented in a single environment are presented and applied to the Environmental Control System (ECS). A new bleed-less and more electric architecture has been developed and its performance has been assessed by a modeling and simulation environment. The latter includes inlet design, engine modification, cabin airflow characterization as well as a weight balance and an economic impact assessment.