Future Aerospace Vehicles Research Articles

A novel co-continuous Si–Zr hybrid phenolic aerogel composite with excellent antioxidant ablation enabled by sea-island-like ceramic structure at high temperature

Lightweight phenolic matrix composites are highly potential in ablative thermal protective materials for future aerospace vehicles, and hybrid modification is considered as one of effective ways to improve the oxidation and ablation resistance of phenolic matrix. Herein, the co-continuous silica zirconium hybrid phenolic resin (SZRx) was synthesized, which can be used to prepare lightweight ablation resistant aerogel composites by the sol-gel method. The SZRx aerogel showed stable porous structure and excellent hydrophobicity, and the silicon zirconium hybrid greatly improved the high temperature carbon residue and oxidation resistance of phenolic resin. The SZRx aerogel composites also possessed excellent integrated characteristics of heat protection and insulation, with a linear ablation rate as low as 0.032 mm/s and a back temperature below 200 °C. The synergistic effect of silicon and zirconium formed the multiphase ceramic layer (C, SiO2, SiC and ZrO2) with the sea-island-like structure on the surface of the composite material, which can effectively resist high-temperature ablation and aerodynamic exfoliation. This can indicate that silicon zirconium dual element hybrid phenolic resin is the highly competitive matrix for lightweight and ablation resistant composite materials.

Experimental investigation on cryogenic chilldown performance under high-Reynolds number condition and using interior micro-fin structure

Future aerospace vehicle requires a fast propellant fueling and a rapid launching. In the present study, a high-pressure chilldown test platform is established, and two different tube structures, including a straight tube and an interior micro-fin tube, are tested under different inlet Reynolds number (Re) conditions. The test results show that for a typical chilldown case through the straight tube, different boiling mechanisms successively dominate the fluid-wall heat transfer, and inverse annular flow film boiling occupies the maximum proportion of wall temperature decrease. Increasing inlet flow rate could accelerate the chilldown rate, and the time cost in Re=45,000 case is only about 15% of that in Re=5,000 case. For the proposed interior micro-fin tube, the test results verify its excellent performance in improving chilldown rate. Under Re=5,000 condition, the time cost for micro-fin tube case is only about 70 s, which is far less than the time cost by a straight tube case. This astonishing performance is mainly because the micro-fin structure induces a radial velocity component in the inverse annular vapor film. The radial velocity strike acts on the liquid-vapor interface, yielding an interface fluctuation or even a liquid column breakup. Therefore, the liquid phase could contact the tube warm wall earlier, and then a sustained high heat flux gives rise to significant temperature decrease effect throughout the whole chilldown process.

Cycle optimization of the staged combustion rocket engines

PurposeThe purpose of this paper is to introduce new and modified “staged combustion” cycles in the form of engineering algorithm as a possible propulsion contender for future aerospace vehicle to achieve the highest possible “total impulse” to “mass” of propulsion system.Design/methodology/approachIn this regard, the mathematical cycle model is formed to calculate the engine’s parameters. In addition, flow conditions (pressure, temperature, flow rate, etc). in the chamber, nozzle and turbopump are assessed based on the results of turbo machinery power balance and initial data such as thrust, propellant mixture ratio and specifications. The developed code has been written in the modern, object-oriented C++ programming language.FindingsThe results of the developed code are compared with the Russian RD180 engine which demonstrates the superiority and capability of new “thermodynamic diagrams”.Research limitations/implicationsThis algorithm is under constraint to control the critical variation of combustion pressure, turbine rpm, pump cavitation and turbine temperature. It is imperative to emphasize that this paper is limited to “oxidizer-rich staged combustion” engines with “single pre-burner”.Originality/valueThis study sheds light on using fuel booster turbopump and the second-stage fuel pump to moderate the effect of cavitation on pumps which reduces tank pressure and, as a consequence, decreases the propulsion system weight.

Development of Web Directory of Aerospace Testing Facilities in India (ATFI)

The paper is an outcome of a major research project funded by the Aeronautics Research and Development Board (AR&DB), DRDO. The primary intent of this project is to create a web-based database of testing facilities in aerospace and to facilitate sophisticated searchable database on WWW platform. The output of the project report can be treated as a working catalogue to provide narrative information describing each facility, its testing capabilities, unique characteristics, location, organisation, key persons, etc. Usage of the database is divided into passive and active. It enables to identify specific data requirements needed to quantify the status of the country's technological maturation from which an assessment can be made for research, development and testing of future aerospace vehicles. It also helps in designing standard operating procedure for providing Aerospace Test facilities existing in DRDO labs to the private sector (including under ‘Make in India’ initiative) on payment basis.

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, weig...

Taking nanotechnology to new heights: The potential impact on future aerospace vehicles

Abstract

Curvilinearly T-Stiffened Panel-Optimization Framework Under Multiple Load Cases Using Parallel Processing

Future aerospace vehicles like hybrid wing/body, truss-braced wing, and “double bubble” would have pressurized noncircular fuselage structures and complex wing geometry. Traditional aircraft designs have led to the confidence and experience of designing such structures using the knowledge base built over the years and the resulting rules of thumb. However, there is a lack of experience of load calculations and design of complex, multifunctional, aircraft structural concepts for future aerospace vehicles. Designing such structures will require a physics-based optimization framework. Therefore, a new optimization framework, EBF3PanelOpt, is being developed. Commercial software MD-PATRAN (geometry modeling and mesh generation) and MD-NASTRAN (finite-element analysis) are integrated in EBF3PanelOpt framework using the Python programming environment to design stiffened panels with curvilinear stiffeners. Currently, EBF3PanelOpt optimizes the stiffened panel with curvilinear blade stiffeners, where the loads are applied only through the plate. During the optimization, the mass is minimized with the constraints on buckling, von Mises stress, and crippling or local failure of the stiffeners. EBF3PanelOpt is enhanced to have curvilinear T stiffeners with or without axial loads in addition to loads through plate. The panel/stiffener geometry is defined in a parametric fashion based on design variables that include variables for orientation and shape of the stiffeners, the thicknesses and heights of the webs and flanges of the stiffeners, and the plate-pocket thicknesses. This framework is supported with coarse-grained parallelism using Python to analyze multiple designs on the cluster. Using this framework, a vertical stabilizer skin panel of transport aircraft panel having two extreme load cases is optimized using with or without stiffener loads. When the equivalent uniform loads are applied only through the plate, the plate buckling becomes critical, but combined buckling of plate and stiffeners becomes critical when the loads are applied through both the plate and the stiffeners. When the uniform in-plane compressive loads are applied through both the plate and the stiffeners, the panel with straight T stiffeners is more optimal than the panel with curvilinear T stiffeners.

Real-Time Simulation as a New Tool in Future Advanced Aerospace Project Design and Manufacturing Processes

Conceptualisation and subsequent validation are essential for future aerospace vehicle design. In this process, theoretical analysis is often constrained imposed by numerical and physical experimentation limitations. This is where the incorporation of flight and other simulation packages as new tools of real-time investigation, for determining design drivers, estimating flight performance, likely operational scenarios and manufacturing strategies can become so useful. For the past few years, we have been exploring the effectiveness of this new tool at the University of New South Wales. The results appear to be highly promising. In this paper, we outline the various stages of the methodology and demonstrate through a test case how the simulation activity can be implemented in the overall design process. It appears that the incorporation of simulation into the design process has the prospect of ushering in a new era for future advanced project aerospace design that will find application far beyond aerospace industries.

On the response of two commercially-important CFRP structures to multiple ice impacts

Carbon-fibre reinforced composites (CFRPs) are likely to feature heavily as structural elements of future aerospace vehicles due to their high stiffness and low densities. However, such components are likely to be subjected to a variety of impact-related events during their in-service lives. One area which has only received limited attention in the literature is that of ice impact on CFRP structures; e.g. hail stone impacts on aerospace components. In this study the response of two aerospace-grade CFRP structures (one woven and one uni-directional lay-up) to multiple ice impacts with cumulative impact energies in the range 72–1215 J was investigated. Six empirical damage categories were identified, ranging from no apparent surface damage (Type 1) to penetration accompanied by complete lay-up disruption (Type 6). Surface damage was found to correlate with changes in recovered panel properties; determined by ultrasonic C-Scan and compression-after-impact strength tests. With both CFRP structures sub-surface disruption and residual compressive strength varied linearly with total impact energy; suggesting that damage in such structures is cumulative in nature. Further, in line with previous studies, the woven structure consistently exhibited lower levels of damage at a given impact energy, even when damage extent was normalised by areal density.

Autonomous Control Reconfiguration of Aerospace Vehicle Based on Control Effectiveness Estimation

Future aerospace vehicles (ASV) are designed to fly in both inner and extra atmospheric fields, which requires autonomous adaptability to the uncertainties emanated from abrupt faults and continuously time-varying environments. An autonomous control reconfiguration scheme is presented for ASV to deal with the uncertainties on the base of control effectiveness estimation. The on-line estimation methods for the time-varying control effectiveness of linear control system are investigated. Some sufficient conditions for the estimable system are given for different cases. There are proposed corresponding on-line estimation algorithms which are proved to be convergent and robust to noise using the least-square-based methods. On the ground of fuzzy logic and linear programming, the control allocation algorithms, which are able to implement the autonomous control reconfiguration through the redundant actuators, are put forward. Finally, an integrated system is developed to verify the scheme and algorithms by way of numerical simulation and analysis.

Ultra-High Temperature Ceramics (UHTCs) via Reactive Sintering

Current high temperature ceramics, such as ZrO2, Si3N4 and SiC, cannot be used at temperatures over 1600°C due to their low melting temperature or dissociation temperature. For ultrahigh temperature applications over 1800°C, materials with high melting points, high phase composition stability, high thermal conductivity, good thermal shock and oxidation resistance are needed. The transition metal diborides, mainly include ZrB2 and HfB2, have melting temperatures of above 3000°C, and can basically meet the above demands. However, the oxidation resistance of diboride monolithic ceramics at ultra-high temperatures need to be improved for the applications in thermal protection systems for future aerospace vehicles and jet engines. On the other hand, processing science for making high performance UHTCs is another hot topic in the UHTC field. Densification of UHTCs at mild temperatures through reactive sintering is an attracting way due to the chemically stable phase composition and microstructure as well as clean grain boundaries in the obtained materials. Moreover, the stability studies of the materials in phase composition and microstructures at ultra high application temperatures is also critical for materials manufactured at relatively low temperature. Furthermore, the oxidation resistance in simulated reentry environments instead of in static or flowing air of ambient pressure should be evaluated. Here we will report the concept, advantages and some recent progress on the reactive sintering of diboride–based composites at mild temperatures.

Linear temporal characteristics of heart interbeat interval as an index of the pilot's perceived risk

The concept of adaptive automation is the first commendable step towards machine monitoring and support of the human operator behaviour and performance. Despite a large number of studies, the concept is still not sufficiently mature and more experimental studies are required to enable its application in the real world. As a small contribution in this direction, this experimental study made an effort to develop some techniques for online assessment of the pilot's perceived risk of the consequences resulting from their inability to execute a task adequately. Linear dynamical characteristics of 60 pilot's heart interbeat intervals were used for the assessment. Past research has shown that such ‘perceived risk’ influences the pilot's need for an automation aid. The preliminary results of this study suggested that the frequency and power of the heart interbeat interval dominant cycle, together with the characteristics of the energy contained in the power spectrum, can be sensitive indices of the level of perceived risk. The study techniques and preliminary results appear promising for incorporation into the algorithm of an intelligent online monitoring and alerting system on future aerospace vehicles to define the moments when the human supervisory controllers require an automation aid.

Identification of nonlinear parameters for reduced order models

Constructing nonlinear structural dynamic models is a goal for numerous research and development organizations. Such a predictive capability is required in the development of advanced, high-performance aircraft structures. Specifically, the ability to predict the response of complex structures to engine induced and aero acoustic loading has long been a United States Air Force (USAF) goal. Sonic fatigue has plagued the USAF since the advent and adoption of the turbine engine. While the problem has historically been a maintenance one, predicting the dynamic response is crucial for future aerospace vehicles. Decades have been spent investigating the dynamic response and untimely failure of aircraft structures, yet little work has been accomplished towards developing practical nonlinear prediction methods. Further, the last decade has witnessed an appreciable amount of work in the area of nonlinear parameter identification. This paper outlines a unique and important extension of a recently introduced nonlinear identification method: Nonlinear Identification through Feedback of the Outputs (NIFO). The novel extension allows for a ready means of identifying nonlinear parameters in reduced order space using experimental data. The nonlinear parameters are then used in the assembly of reduced order models, thus providing researchers with a means of conducting predictive studies prior to expensive and questionable experimental efforts. This paper details both an analytical and experimental study conducted on a well-characterized clamped–clamped beam subjected to broadband random loading. Amplitude dependent, constant stiffness parameters were successfully identified for a multiple-degree-of-freedom (MDOF) nonlinear reduced order model. The nonlinear coefficients identified from the analytical scenario compare well with previously published studies of the beam. Nonlinear parameters were also successfully identified from the raw experimental data. Finally, a MDOF nonlinear reduced order model, constructed from experimental data, was used to predict the experimental response of the beam to other loading conditions. Beam response spectra and average displacement values from the prediction model also compare well with the experimental results.

放電プラズマ焼結法で作製したＳＣＳ‐６／Ｔｉ‐１５Ｖ‐３Ｃｒ‐３Ｓｎ‐３Ａｌ複合材料の強度特性

The low structural mass fraction required for future aerospace vehicles necessitates the development of new materials having improved specific properties at elevated temperatures. Fiber-reinforced titanium matrix composites (TMC) offer significant improvements in strength and stiffness over their monolithic counterparts and are prime candidates for these applications. This study was undertaken to investigate the effects of TMC processing on the axial tensile properties of unidirectional SCS-6/Ti-15V-3Cr-3Sn-3Al (Ti-15-3) titanium matrix composites. The composite was manufactured by using spark plasma sintering (SPS). The Ti-15-3 powder and SCS-6 fiber mats were consolidated by SPS at the temperature of 800, 900 and 1,000ºC, and at pressure of 30 and 60 MPa in vacuum. The tensile specimens of TMC were tested in air at room temperature, 400, 600, and 800ºC, and the resulting properties were compared to those of TMC by hot pressing. The reactions and microstructures were studied in interfaces between SCS-6 and Ti-15-3. TMC consolidated by SPS had tensile strengths of 756 to 1,570MPa from room temperature to 800ºC. The SPS provided superior tensile strengths of TMC, as compared to hot pressing.

Future challenges and opportunities in aerodynamics

AbstractInvestments in aeronautics research and technology have declined substantially over the last decade, in part due to the perception that technologies required in aircraft design are fairly mature and readily available. This perception is being driven by the fact that aircraft configurations, particularly the transport aircraft, have evolved only incrementally over the last several decades. If, however, one considers that the growth in air travel is expected to triple in the next 20 years, it becomes quickly obvious that the evolutionary development of technologies is not going to meet the increased demands for safety, environmental compatibility, capacity, and economic viability. Instead, breakthrough technologies will be required both in traditional disciplines of aerodynamics, propulsion, structures, materials, controls and avionics as well as in the multidisciplinary integration of these technologies into the design of future aerospace vehicles concepts. The paper discusses challenges and opportunities in the field of aerodynamics over the next decade. Future technology advancements in aerodynamics will hinge on our ability to understand, model and control complex, three-dimensional, unsteady viscous flow across the speed range. This understanding is critical for developing innovative flow and noise control technologies and advanced design tools that will revolutionise future aerospace vehicle systems and concepts. Specifically, the paper focuses on advanced vehicle concepts, flow and noise control technologies, and advanced design and analysis tools.

Structures technology for future aerospace systems

An overview of structures technology for future aerospace systems is given. Discussion focuses on developments in component technologies that will improve the vehicle performance, advance the technology exploitation process, and reduce system life-cycle costs. The component technologies described are smart materials and structures, multifunctional materials and structures, affordable composite structures, extreme environment structures, flexible load bearing structures, and computational methods and simulation-based design. The trends in each of the component technologies are discussed and the applicability of these technologies to future aerospace vehicles is described.

Ram accelerator utilizing active projectile

A chemical-propulsion accelerator (either ram- or external-propulsion) system, utilizing a novel, activeprojectile concept is proposed. The projectile comprises the mechanism for compression, storage, and release of high-pressure fluid, that may be either the fuel or the oxidizer used in the ambient combustible gas mixture or inert gas. The shock pattern established by ejection of high-pressure gas from the supersonic projectile into the ambient, combustible-gas mixture serves to ignite the mixture through shock heating and compression, and therefore, to induce the desired propulsive mode (combustion or detonation). The ejected gas then serves to alter locally the ambient mixture, and therefore, can enhance its reactive properties. The present method alse-effers potential application in future aerospace vehicles that will utilize external propulsion modes. A simple model is used to show the practicality of the method and to estimate the lateral size of the combustion zone. The results show that the jet bow shock can ignite the combustible mixture within a radial distance from the body comparable with the barrel radius used in the present ram accelerators. The size of the combustion zone is shown to scale favorably with increasing Mach numbers encountered during the acceleration. The amount of the injectant gas needed is shown to be small. ^

Crack growth and residual strength characteristics of two grades of glass-reinforced aluminium ‘Glare’

Crack growth and residual strength tests have been conducted on both Glare 3 and Glare 4 material. Results have been compared with those for 2024-T3 monolithic aluminium alloy showing improvements in fatigue life of up to 100 times and improvements in residual strengths of up to 40%. The potential weight savings and general structural performance improvements of the Glare material make it most attractive for future aerospace vehicle design, despite its current higher manufacturing costs.

Aerospace Applications of Advanced Aluminum Alloys

Advanced metallic materials within the Al-base family are being developed for applications on current and future aerospace vehicles. These advanced materials offer significant improvements in density, strength, stiffness, fracture resistance, and/or higher use temperature which translates into improved vehicle performance. Aerospace applications of advanced metallic materials include space structures, fighters, military and commercial transport aircraft, and missiles. Structural design requirements, including not only static and durability/damage tolerance criteria but also environmental considerations, drive material selections. Often trade-offs must be made regarding strength, fracture resistance, cost, reliability, and maintainability in order to select the optimum material for a specific application. These trade studies not only include various metallic materials but also many times include advanced composite materials. Details of material comparisons, aerospace applications, and material trades will be presented.

Outer atmospheric research using tethered systems

The region about 90-150 km above the Earth is a major part of the upper or outer atmosphere. It is relatively unexplored, being too high for balloons or aircraft and too low for persistent orbiting spacecraft. However, the concept of a tethered subsatellite, deployed downward from an orbiting, more massive craft such as the Space Shuttle, opens the possibility of a research capability that could provide global mapping of this region. The need for research in this thick spherical shell above the Earth falls into two major categories: 1) scientific data for understanding and modeling the global atmosphere and thereby determining its role in the Earth system and 2) engineering data for the design of future aerospace vehicles that will operate there. This paper presents an overview and synthesis of the currently perceived research needs and the state-of-the-art of the proposed tethered research capability.