A Novel Loss Tolerant Data Transmission Schemes for Airborne Telemetry System of a Long Range Aerospace Vehicle

The on-board telemetry system of an aerospace vehicle sends the vehicle performance parameters to the ground receiving station at all instances of its trajectory. During the course of its trajectory, the communication channel of a long range vehicle, experiences various phenomena such as plume attenuation, stage separation, manoeuvring of a vehicle and RF blackout, causing loss of valuable telemetry data. The loss of communication link is inevitable due to these harsh conditions even when using the space diversity of ground receiving systems. Conventional telemetry systems do not provide redundant data for long range aerospace vehicles. This research work proposes an innovative delay data transmission, frame switchover and multiple frames data transmission schemes to improve the availability of telemetry data at ground receiving stations. The proposed innovative schemes are modelled using VHDL and extensive simulations have been performed to validate the results. The functionally simulated net list has been synthesised with 130 nm ACTEL flash based FPGA and verified on telemetry hardware.

A New Strategy for Improving the Surface Quality of Ti6Al4V Machined by Abrasive Water Jet: Reverse Cutting with Variable Standoff Distances

Titanium alloys are widely used in important structures of aerospace vehicles, but the low thermal conductivity and high chemical activity make them difficult to process. As an untraditional machining technology, abrasive water jet (AWJ) has been proven to be an effective method for this kind of material. Aimed at further improving the cutting performance, reverse cutting with variable standoff distance (SOD) strategy was put forward, and experiments of titanium alloy Ti6Al4V machined by AWJ were conducted. The influence of SOD with different reverse cutting types on the kerf quality was studied to obtain the optimal SOD combinations. Ra, Sa and kerf taper were used to evaluate the quality of the machined surface. Moreover, the results of reverse cutting at the same speed and efficiency and single cutting at the constant SOD were compared and analyzed. It was found that the proposed strategy results in higher kerf quality in the aspect of surface roughness, compared to the single cutting. To be more specific, for the reverse trimming cutting, the improvements of Ra and Sa can reach up to 62.8% and 73.1% respectively under the condition of the SOD of the second cutting is 8mm. Furthermore, the kerf taper can be reduced 26.1% when the SOD of the second cutting is 2mm. With respect to the reverse deepening cutting, even the traverse speed of reverse cutting is set as twice as that of a single cutting, the kerf quality is still better. Additionally, when the SOD of the second cutting is 4mm, the improvements of Ra and Sa can reach up to 51.7% and 14.9%, respectively, and the kerf taper is reduced by 20.2%. This study provides a new method for improving the machined surface quality of hard materials, especially for Ti6Al4V.

Numerical Tool for MOS Calculation with Different Mechanical/ Thermal Loads and Safety Factors Combinations

For aerospace vehicles, such as rockets and satellites that are subjected to high mechanical and thermal loading, it is necessary to better understand how the structure is influenced by these loads. Because reducing the mass of the structure while maintaining strength is a very important requirement, field-tested components will be subject to different SFs (safety factors) than those that are only subjected to FEA (Finite Element Analysis). Also to further reduce the magnitude of the load factors in the MOS (Margin of Safety) calculation, mechanical loads are considered to have a different safety factor than the thermal loads. This paper proposes a solution, a tool developed to calculate MOS for structural parts for different safety factors on mechanical and thermal loads, based on data obtained from FEA. The tool takes as input the results from the NASTRAN result files and creates one excel file with MOS for each component requested by the user and different types of summary.

Crack Growth Simulation of Functionally Graded Materials Based on Improved Bond-Based Peridynamic Model

Functionally graded materials (FGMs) are widely used in the aerospace industry, especially for the thermal protection shields of aerospace vehicles. Studies show that the initiation and expansion of micro-cracks are important factors that adversely affect the service life of these shields. Based on the peridynamic theory of bonds, an improved peridynamic model is proposed in the present study for FGMs. In the proposed model, integral equivalence is applied to calculate the required material parameters. Obtained results reveal that this method can better reflect the gradient change of material properties.

Flight Stability Analysis of a Flexible Rocket Using Finite Elements and Reduced-Order Modeling

The coupling of advanced structural and aerodynamic methods is a complex and computationally demanding task. In many cases, simplifications must be made. For the flight simulation of flexible aerospace vehicles, it is common to reduce the overall structure down to a series of linked degenerate structures such as Euler-Bernoulli beams in order to expedite the structural portion of the solution process. The current study employs the sophistication and generality of finite-element based modeling with the concepts of reduced-order modeling to create a general flexible-body flight simulation program. The program was created for use with the MATLAB-Simulink programming package. A parametric analysis on the stability of flexible rockets is performed and results are presented for a variety of rocket configurations based on the SPHADS-1 vehicle under development at Ryerson University. The primary instability mode under study is that associated with the flapping and twisting motions of the tailfins under aerodynamic loading. By varying the average fin thickness, both stable and unstable behaviour is recorded for a variety of flight conditions.

Flight Stability Analysis of a Flexible Rocket Using Finite Elements and Reduced-Order Modeling

The coupling of advanced structural and aerodynamic methods is a complex and computationally demanding task. In many cases, simplifications must be made. For the flight simulation of flexible aerospace vehicles, it is common to reduce the overall structure down to a series of linked degenerate structures such as Euler-Bernoulli beams in order to expedite the structural portion of the solution process. The current study employs the sophistication and generality of finite-element based modeling with the concepts of reduced-order modeling to create a general flexible-body flight simulation program. The program was created for use with the MATLAB-Simulink programming package. A parametric analysis on the stability of flexible rockets is performed and results are presented for a variety of rocket configurations based on the SPHADS-1 vehicle under development at Ryerson University. The primary instability mode under study is that associated with the flapping and twisting motions of the tailfins under aerodynamic loading. By varying the average fin thickness, both stable and unstable behaviour is recorded for a variety of flight conditions.

Evolved auxiliary controller with applications to aerospace

Purpose To guarantee the asymptotic stability of discrete-time nonlinear systems, this paper aims to propose an evolved bat algorithm fuzzy neural network (NN) controller algorithm. Design/methodology/approach In evolved fuzzy NN modeling, the NN model and linear differential inclusion representation are established for the arbitrary nonlinear dynamics. The control problems of the Fisher equation and a temperature cooling fin for high-speed aerospace vehicles will be described and demonstrated. The signal auxiliary controlled system is represented for the nonlinear parabolic partial differential equation (PDE) systems and the criterion of stability is derived via the Lyapunov function in terms of linear matrix inequalities. Findings This representation is constructed by sector nonlinearity, which converts the nonlinear model to a multiple rule base for the linear model and a new sufficient condition to guarantee the asymptotic stability. Originality/value This study also injects high frequency as an auxiliary and the control performance to stabilize the nonlinear high-speed aerospace vehicle system.