Multi-objective trajectory optimization for guided surface-to-surface missiles

During the early phases of engineering design, the costs committed are high, costs incurred are low, and the design freedom is high. It is well documented that decisions made in these early design phases drive the entire design's life cycle cost. In a traditional paradigm, key design decisions are made when little is known about the design. As the design matures, design changes become more difficult in both cost and schedule to enact. The current capability-based paradigm, which has emerged because of the constrained economic environment, calls for the infusion of knowledge usually acquired during later design phases into earlier design phases, i.e. bringing knowledge acquired during preliminary and detailed design into pre-conceptual and conceptual design. An area of critical importance to launch vehicle design is the optimization of its ascent trajectory, as the optimal trajectory will be able to take full advantage of the launch vehicle's capability to deliver a maximum amount of payload into orbit. Hence, the optimal ascent trajectory plays an important role in the vehicle's affordability posture yet little of the information required to successfully optimize a trajectory is known early in the design phase. Thus, the current paradigm of optimizing ascent trajectories involves generating point solutions for every change in a vehicle's design parameters. This is often a very tedious, manual, and time-consuming task for the analysts. Moreover, the trajectory design space is highly non-linear and multi-modal due to the interaction of various constraints. When these obstacles are coupled with the Program to Optimize Simulated Trajectories (POST), an industry standard program to optimize ascent trajectories that is difficult to use, expert trajectory analysts are required to effectively optimize a vehicle's ascent trajectory. Over the course of this paper, the authors discuss a methodology developed at NASA Marshall's Advanced Concepts Office to address these issues. The methodology is two-fold: first, capture the heuristics developed by human analysts over their many years of experience; and secondly, leverage the power of modern computing to evaluate multiple trajectories simultaneously and therefore enable the exploration of the trajectory's design space early during the pre- conceptual and conceptual phases of design. This methodology is coupled with design of experiments in order to train surrogate models, which enables trajectory design space visualization and parametric optimal ascent trajectory information to be available when early design decisions are being made.

The initial phases of design, known as the conceptual design phases, are often associated with hand sketching, while parametric tools are reserved for the later, more developed stages of design. This paper examines the potentials of using parametric tools in the early design phases in comparison to widely utilized hand sketching. It is intended to find out the impacts of using parametric tools on the cognitive behaviors and the satisfaction of self-assessment levels of the designers. An experimental study was conducted with a group of graduate architecture students using Grasshopper, the findings of which are analyzed through a content-oriented coding scheme, together with protocol analyses. Significant differences are found between cognitive behaviors of the participants in using hand sketching and Grasshopper. The findings show that all of the participants consider Grasshopper as a useful conceptual design tool that may be utilized in early design phases, in contrast to its wide popularity in the late stages of design.

In a product development process, it is crucial to understand and evaluate multiple and synergic aspects of systems such as performance, cost, reliability, and safety. These aspects are mainly considered during later stages of the design process. However, in order to improve the foundations for decision-making, this article presents methods that are intended to increase the engineering knowledge in the early design phases. In complex products, different systems from a multitude of engineering disciplines have to work tightly together. Collaborative design is described as a process where a product is designed through the collective and joint efforts of domain experts. A collaborative multidisciplinary design optimization process is therefore proposed in the conceptual design phase in order to increase the likelihood of more accurate decisions being taken early on. The performance of the presented framework is demonstrated in an industrial application to design aircraft systems in the conceptual phase.

Risk assessments are necessary to anticipate and prevent accidents from occurring or repeating. Current probabilistic risk assessment methods require mature design proposals to analyse. Since product safety and reliability are affected the most by decisions made during the early design phases, a risk assessment that can be performed with less mature data during these design phases is needed. This study focuses specifically on the relationship between function and risk in early design by presenting a mathematical mapping from product function to risk assessments that can be used in the conceptual design phase. An investigation of a spacecraft orientation subsystem is used to demonstrate the mappings. The results from the study and its spacecraft application yield a preliminary risk assessment method that can be used to identify and assess risks as early as the conceptual phase of design. The preliminary risk assessment presented in this paper is a tool that will aid designers by identifying risks as well as reducing the subjectivity of the likelihood and consequence value from a risk element, will provide four key risk element properties (design parameter, failure mode, likelihood, and consequence) for numerous risk elements with simple calculations, and will provide a means for inexperienced designers to effectively address risk in the conceptual design phase.

The stability and control characteristics of any flight vehicle have to comply with designand certification requirements throughout the flight envelope. Starting with the early conceptual design phase, the control effectors are responsible to ensure a flyable and safe vehicle despite their adverse effect on flight performance. The design has to guarantee satisfactory flight characteristics, which will be confirmed or censured during the flight test phase at the end of the design chain. The obstacle at the heart of this undesirable situation is the significant information requirement (in both quantity and quality) of designrelated stability and control analysis during the conceptual phase. Clearly, there is a strong incentive to establish a competent link between the first (initial sizing) and the final (flight test) vehicle development stage during the conceptual design phase to reduce design risks. The objective of the present investigation is to identify a generic set of design-constraining flight conditions (DCFC) for conceptual sizing of the longitudinal, lateral, and directional control effectors of conventional and unconventional fixed-wing aircraft types. The study emphasizes on the identification of design-relevant flight conditions for symmetric and asymmetric type of aircraft in symmetric and asymmetric flight conditions. Since this approach avoids the need to evaluate the entire flight envelope for the flight vehicle under consideration, it becomes, however, more important to identify likely worst-case flight conditions beforehand for sizing of control effectors. As a result, a generic set of DCFC has been defined with the support of a dedicated aerospace knowledge-based system, utilizing A340 and Concorde flight test schedules, taking JAR/FAR 25, MIL Specs, and Concorde’s TSS requirements into account. The paper demonstrates that the design criticality of flight conditions depends, to a large degree, on the aircraft configuration choice.

The integration of a reusable scramjet vehicle as the second stage of a multistage space launch system has the potential to reduce the cost of small-payload orbital launches. This paper determines the maximum payload to orbit trajectory of a multistage rocket–scramjet–rocket system. This trajectory is calculated by formulating the problem as an optimal control problem, and then solving it using the pseudospectral method. Using this method, it is determined that the optimal trajectory for the scramjet stage involves an initial decrease in dynamic pressure, followed by constant-dynamic-pressure flight, and finally a pullup maneuver. This optimal trajectory results in an 8.35% improvement in payload mass to orbit when compared to a constant-dynamic-pressure trajectory with minimum pullup. Furthermore, the optimal pullup maneuver decreases the maximum dynamic pressure experienced by the final rocket stage by 20.3%. The sensitivity of the trajectory is tested by varying the maximum allowable dynamic pressure and the drag produced by the vehicle. A maximum dynamic pressure variation of is shown to produce only and variations in the payload mass. A drag increase of 10% is shown to produce a similar optimal trajectory shape, indicating robustness with variation of the vehicle aerodynamics.

The three most important phases of design are (1) conceptual phase; (2) configuration phase; and (3) parameterization phase. The second and the third phases are well researched. However, little work has been done in the conceptual design phase. In this paper the author deals with a different way of modeling the conceptual design phase. In this research the paradigm of function-to-structure transformation is used. One of the most difficult ideas of design is that of modeling the function-to-structure transformation process. The current research shows that the function-to-structure transformation is accomplished through a process of association. Whenever a designer is faced with finding a solution to a new functional requirement, the designer tries to associate this new function with known functions from his/her memory through a process of association. After having identified the closest function, an associated structure can be retrieved and mutated to form the design solution for the new problem. In essence, the designer associates the new functions with known functions and will try to retrieve the closest and most general design solution from his/her memory through a process of association. The author models the human associative memory through artificial neural networks (ANN) with back-propagation. A simple yet illustrative example of cups and containers is selected to model the function-to-structure transformation process at the conceptual design phase. In this paper the implementation aspects of the ANN are clearly explained. The robustness of the ANN through different schemes is also explored. A performance analysisvia simulation by varying the nodes of the hidden layer is also carried out.

We present an approach for computer-aided generation of different variations of floor plans during the early phases of conceptual design in architecture.The early design phases are mostly characterized by the processes of inspiration gaining and search for contextual help in order to improve the building design at hand.The generation method described in this work uses the novel as well as established artificial intelligence methods, namely, generative adversarial nets and case-based reasoning, for creation of possible evolutions of the current design based on the most similar previous designs.The main goal of this approach is to provide the designer with information on how the current floor plan can evolve over time in order to influence the direction of the design process.The work described in this paper is part of the methodology FLEA (Find, Learn, Explain, Adapt) whose task is to provide a holistic structure for support of the early conceptual phases in architecture.The approach is implemented as the adaptation component of the framework MetisCBR that is based on FLEA.

The growing complexity of green transport vessels results in a gap between current ship design methods and new green transport vessel design. Innovative technologies such as digital twins (DTs) show the potential in supporting future complex designs when combined with suitable current ship design methods. The current state-of-the-art in DT-enabled design processes is still in its early research phases, both in the maritime world, and general engineering community. The most recent literature is presented, as well the role of optimization in the early design phases. Two complimentary design approaches are proposed, aimed at the concept design phases of green ships, where most of the design requirements are set (via design requirements) and locked-in (via initial design decisions). First, a DT-based green transport vessel design method is proposed which is then evaluated through a case study on an LNG-powered handysize bulk carrier. Four design scenarios are presented to show the ability of the design approach to simulate vessel behaviour, providing a feasible design space, and supporting early design decision-making. Second, an optimization-based DT design approach is proposed also covering the early concept design phase. Combined, the two complimentary DT design approaches help address the gap in enabling DTs in the design of green transport vessels.

The avionics components of modern military aircraft significantly impact the cost and effectiveness of the total aeronautical system. In the early conceptual phase, aeronautical system designers give scant attention to designing the avionics components. The design team generally provides weight, volume and power considerations for the desired avionics functions and assumes that an avionics suite can be assembled. Less than comprehensive attention is given to the interacting effect avionics have with the other system components. In contrast, the designers expend a very large effort on finding the best balanced combination of airframe and propulsion components which satisfy the design objectives. This paper shows why avionics must be a co-equal member of the aeronautical system along with airframe, propulsion, and armament. To become a co-equal partner, avionics must be an element of the system design iterations and analysis commencing with the early conceptual design phase of a new aeronautical system.

Industrial Resources in the design of Reconfigurable Manufacturing Systems for aerospace: A systematic literature review

Simulated annealing for missile trajectory planning and multidisciplinary missile design optimization

Vehicle Concept Modeling: A New Technology for Structures Weight Reduction

The development and application of the vehicle advanced CAE (computer aided engineering) allowed the vehicle designers to considerably reduce the weight and improve the structural performance of the body. However, the current advanced CAE model can only be available in the late design phase of the vehicle when only minor changes of the structure is feasible. Despite the detailed CAE model, which requires all detailed design, the concept CAE model can be created with less need for the detailed CAD data and it can be created in the early (concept) design phase. The members and panels of the automotive body in white (BIW) are modeled and approximated using beam and shell elements. The joints properties are then obtained from the original detailed CAE model using Guyan reduction method. The automotive seat concept model is also created and added to the concept BIW model. The developed models show good correlation with corresponding advanced CAE models as well as corresponding modal tests results in low frequency range. The interaction of the seat and BIW modes, which can be the cause of a poor seat vibration, is considered as a problem for structural optimization. Optimization of the BIW and the seat structure to prevent this mode interaction is only feasible in the early design phase. Sensitivity analysis and optimization of the structure were successfully conducted on the BIW-Seat concept model. The developed NVH CAE concept model demonstrates a good method to enhance the NVH performance in early stage of design. The proposed method can be used to effectively predict and optimize the BIW structure.

Conceptual design of cogeneration plants under a resilient design perspective: Resilience metrics and case study