Comparative analysis of new configurations of aircraft aimed at competitiveness, environmental compatibility and safety

This Ph.D. Thesis aims at suggesting a proper integrated and multidisciplinary design methodology to improve the current conceptual and preliminary design phases of breakthrough innovative aerospace products. The methodology, based on a Systems Engineering approach, is presented together with an envisaged toolchain, consisting of both commercial and ad-hoc developed software, integrated in a Model-Based Systems Engineering perspective. In addition, for the sake of clarity and for validation purposes, a specific case study has been selected and developed all along the document. The reference case-study is inspired to a real pre-feasibility study in which the research group of Politecnico di Torino, which the author of this Thesis belongs to, has been involved. The project aims at developing a suborbital vehicle able to perform parabolic flights for both scientific and touristic purposes. This kind of initiatives paves the way for the future hypersonic vehicles, because it allows to crucial enabling technologies to be tested and validated in relevant environment but with lower performances’ requirements. The Thesis is articulated in seven Chapters with an introduction and conclusion sections and in each Chapter a balanced mix between theoretical investigation, mathematical model development, tool selection or development and application to the selected case study is guaranteed. This document starts reporting the major reasons why an innovative design methodology should be envisaged to deal with the increasing level of complexity in the aerospace domain. In particular, in the first Chapter, a brief overview of existing or underdevelopment initiatives related to hypersonic is reported, together with the description of the different types of mission in which the new hypersonic vehicles will be exploited. Moreover, the major issues related to the infrastructures required to operate these transportation systems are summarized. As far as operations are concerned, a short section makes the readers aware of the current under-development regulatory framework. Then, the integrated multidisciplinary design methodology is presented starting from the very high level analyses up to the sizing of the different components of the transportation system. All along the document, crucial role is played by requirements, whose management can allow a complete traceability of the different design characteristics during the overall product life-cycle. Furthermore, proper algorithms allowing to move from purely qualitative to quantitative trade-offs, are presented, with a noticeable advantage in terms of traceability and reproducibility. Eventually, further improvements of both the tool-chain and the reference case studies are envisaged for future developments

Preliminary reliability and safety assessment methodology for trans-atmospheric transportation systems

Purpose This paper aims to propose a methodology for a safety and reliability assessment for the conceptual and preliminary design of very complex and disrupting innovative systems like trans-atmospheric vehicles. The proposed methodology differs from existing ones because it does not rely on statistical data at aircraft-level but exploits the statistical population at components-level only. For the sake of clarity, the paper provides some preliminary results of the application of the methodology at system level. The example deals with the safety and reliability assessment of a very complex propulsion system aimed at guaranteeing vertical take-off and landing capabilities of a suborbital vehicle. Design/methodology/approach The proposed methodology is strongly based on a systems engineering approach. It exploits safety and reliability assessment analyses which have already been developed in both aeronautical and space engineering domains, but it combines them in an innovative way to overcome the lack of statistics at aircraft level. The methodology consists of two different steps: a qualitative top-down process, allowing a functional and physical decomposition of the transportation system and a following quantitative bottom-up approach, which provides the estimation of system-level reliability and safety characteristics starting from the statistical estimation of the components’ characteristics. Findings The paper presents a new methodology for the preliminary reliability and safety assessment of innovative transportation systems, such as hypersonic transportation systems. The envisaged methodology will overcome the poorness of statistical data that is usually affecting the conceptual design of breakthrough systems. Research limitations/implications The paper shows the application of the articulated methodology to a limited case study. A complete example of application of the methodology to estimate safety and reliability characteristics at vehicle level will be provided in feature works. Practical implications The methodology has been proposed to be exploited in international research activities in the field of hypersonic transportation systems. Furthermore, a massive application of this approach would allow to create a database for the generation and the update of semi-empirical models focused on high-level estimations of reliability, availability, maintainability and safety (RAMS) characteristics. Moreover, the proposed safety assessment has been conceived to be fully integrated within a typical conceptual design process. Originality/value The existing literature about safety and reliability assessment at the early design stages proposes pure statistical approaches which are usually not applicable to highly innovative products, where the statistical population is not existing, for example, in the case of trans-atmospheric vehicles. This paper describes how to overcome this problem, through the exploitation of statistical data at components-level only through the combination of these data to estimate RAMS characteristics at aircraft-level thanks to functional analysis, concept of operations and typical safety assessment tools, like functional hazard analysis, failure mode and effect analysis, reliability block diagram and fault tree analysis. </jats:sec

Design of a blow off valve for turbocharged engine applications

On a turbo engine, the Blow of Valve (BOV) is used to relieve the pressure from the turbo output when the throttle is closed. Without the BO y, when the throttle is closed the turbo is suddenly trying to pump air against a closed throttle plate. This creates pressure spike in the turbo output hose and will send back the pressure to the turbine and can damage the turbo engine. When the throttle is opened again, the turbo has to spin up again, creating turbo lag. So, the present of the BOY will opened when the throttle is closed and pressurized the pressure spike to the air to avoid those phenomena. So, good flow of the air inside the BOV is important, the air will smoothly pressurized to the atmosphere if there is no back pressure inside the system. Computer aided design (CAD) and computational fluid dynamic (CFD) software were used as a tool for the design. This design is the improvement of the aftermarket design. The piston surface, size of vent, inlet ports, outlet ports, and also spring plays the role in the BOy. The design analyzed using CFD so can see the flow trajectories of the air inside the BOy

Technology roadmapping methodology for future hypersonic transportation systems

This paper discloses an innovative methodology for the generation and update of technology roadmaps to support strategic decisions for future hypersonic transportation systems, specifically targeting non-profit oriented R&D. The methodology is fully integrated into up-to-date conceptual design activity flows. It consists of five main steps that through mathematical and logical models moves from stakeholders’ analysis up to planning definition and results evaluation. Complementary to the traditional experts-based methodologies, the rational process here presented allows for a well-structured logical definition of activities and/or missions required to enhance the readiness level of technologies, including a more accurate and reliable budget and time resources estimation to support the technology development plan. This methodology is exploited in the framework of the H2020 STRATOFLY Project to assess the potential of hypersonic civil vehicles to reach Technology Readiness Level 6 by 2035 with respect to key technological, societal and economical aspects. The paper discloses a unique assessment of the readiness level of the European air-breathing propulsive technologies. The final results confirm the crucial role of air-breathing propulsive technologies in the development of future hypersonic transportation system and highlight the urgent need to invest in in-flight demonstration missions with increasing functionalities, to target 2050 as entry in to service of the first Mach 8 civil transport

MBSE approach to support and formalize mission alternatives generation and selection processes for hypersonic and suborbital transportation systems

This paper deals with the application of a Model Based Systems Engineering (MBSE) approach to support and formalize mission alternatives generation and selection processes aimed at developing operative hypersonic and suborbital transportation systems. Due to the high-level of complexity of these ultimate aerospace initiatives, a MBSE approach demonstrates to be very effective to allow reduction of risk of inconsistencies, of unappropriated or incompatible design choices, reducing the overall time and effort spent in design and development phases. After a brief introductory section aimed at providing some details about these kinds of vehicles, both in terms of enabling technologies and missions, a step-by-step innovative methodology based on a MBSE approach to carry out mission analysis is proposed. All along the methodology description, the application to a specific reference case study of a suborbital single-stage vehicle aimed at performing commercial parabolic flight services is proposed. Eventually, the selected mission baseline is detailed and the major benefits and further application of this innovative integrated methodology are reported and discussed

Research, development and production costs prediction parametric model for future civil hypersonic aircraft

Assessing the economic viability of new high-speed systems concepts since the early design phases is crucial for the success of future hypersonic vehicles including cruisers, reusable access-to-space and re-entry systems. Besides literature reports few parametric cost models for high-speed vehicles, all of them makes exclusively use of mass as parameter and none of the models moves beyond the vehicle level. This paper describes a new parametric cost estima-tion model which moves beyond the state-of-the-art methodologies (1) by integrating vehicle design and operational parameters (in addition to the mass) as cost drivers for the prediction of the vehicle life-cycle cost, (2) by introducing prediction margins accounting for the uncertainties on the data-driven correlations, (3) by providing a first estimate of the costs of every on-board subsystem, including combined cycle engines and multi-functional subsystems, (4) by increasing the granularity of the analysis up to technology level, thus providing a valuable support to Technology Roadmaping activities. The parametric cost estimation model has been refined and exploited in the context of the Horizon 2020 STRATOFLY project, where the technological, operational, environmental, and economic viability of a Mach 8 waverider concept have been investigated

Performance Assessment of an Integrated Environmental Control System of Civil Hypersonic Vehicles

This paper discloses the architecture and related performance of an environment control system designed to be integrated within a complex multi-functional thermal and energy management system that manages the heat loads and generation of electric power in a hypersonic vehicle by benefitting from the presence of cryogenic liquid hydrogen onboard. A bleed-less architecture implementing an open-loop cycle with a boot-strap sub-freezing air cycle machine is suggested. Hydrogen boil-off reveals to be a viable cold source for the heat exchangers of the system as well as for the convective insulation layer designed around the cabin walls. Including a 2 mm boil-off convective layer into the cabin cross-section proves to be far more effective than a more traditional air convective layer of approximately 60 mm. The application to STRATOFLY MR3, a Mach 8 waverider cruiser using liquid hydrogen as propellant, confirmed that presence of cryogenic tanks provides up to a 70% reduction in heat fluxes entering the cabin generated outside of it but inside the vehicle, by the propulsive system and other onboard systems. The effectiveness of the architecture was confirmed for all Mach numbers (from 0.3 to 8) and all flight altitudes (from sea level to 35 km)

Hypothesis for Hypersonic Flight development

The aim of this work is to promote the hypersonic flight in order to improve both the affordability of the access to space and the terrestrial flight transportation increasing flight range and reducing flight time. A strategic air vehicle is envisaged partially employing state-of-the-art technologies focusing on configuration and feasibility studies. The purpose is obviously to indicate the technologies on which concentrating the design efforts. To enable the development of future spacecraft, it is believed that the effort have to focused on the development, at low cost, of new technology demonstrator aircraft based on suborbital “tourism spacecraft” and fighter aircraft. An important goal would be the development of small and affordable aircraft able to perform the hypersonic cruise

Mixed-Flow Turbofan Engine Model for the Conceptual Design of Sustainable Supersonic Airplanes

Current research efforts on commercial supersonic flight aim to overcome past challenges by designing a new generation of sustainable supersonic airplanes. Achieving this goal requires careful consideration of the propulsion system during the design process. This study proposes a mixed-flow turbofan engine model coupled with emission estimation routines to increase the reliability of the conceptual design of future supersonic aircraft. The model enables parametric analyses by analyzing variations in main engine design parameters (pressure ratios, BPR) as function of the system and mission requirements, such as the Mach number, and suggesting applicability boundaries. The overall methodology was applied to a low-boom Mach 1.5 case study, allowing for both ondesign and off-design analyses and generating a propulsive database to support preliminary mission simulations and chemical emission estimation. Finally, the accuracy and reliability of the engine model was validated against GSP 11 data for a generic mixed-flow turbofan engine. A modified version of the Fuel Flow Method, originally developed by Boeing, allows for emissions estimation throughout the mission for a supersonic engine using biofuels. The application of the methodology led to the definition of an engine with a compressor pressure ratio of 30 and BPR of 0.7 for the selected case study, which was successful in meeting the initial mission requirements

Rapid prototyping for Martian space systems

With the clear path towards Mars for future human exploration missions, rapid prototyping tools may enhance different missions' architectural solutions. Such tools rapidly estimate mass, power and data budgets, providing quantitative figures of metrics to evaluate the most effective technical solutions in line with the stakeholders' needs. Politecnico di Torino is actively working on IDREAM an integrated framework with capabilities of sizing space systems, estimating their cost and building roadmaps for the maturation of the involved technologies. The iDREAM methodology consists of four main modules that can be used in a stand-alone mode and in an integrated activity flow, exploiting the implemented automatic connections. The first module consists of a well-structured MySQL database developed to support all the other modules, thanks to a unified connection guaranteed by an ad-hoc developed Database Management Library managing the operations of data input and output from/to the database throughout the tool modules. The second module consists of a vehicle design routine and a mission design routine, supporting the design of a new vehicle and mission concept and assessing the main performance of an already existing configuration. The third module is estimating the cost of the system. Once the design is defined, it is possible to run a subsystem-level cost estimation. Using the subsystems’ masses estimated in the design routine, the parametric cost model provides useful insights into the potential development, manufacturing, and operating costs, as well as the cost and price per flight. Eventually, the developed methodology gives the possibility to generate a technology roadmap (fourth module). Supported by a database connection, the tool estimates each technology readiness and risk assessment and indicates the necessary activities, missions, and future works. This presentation highlights the use of IDREAM to rapidly prototype Martian space systems