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Shock drag and aeroheating are major problems faced by hypersonic vehicles. This study proposes a novel three-dimensional model combining spike-aerodisk with a bleed air channel featuring multiple lateral nozzles for drag and aeroheating reduction. The high-temperature and high-pressure air at the stagnation point of the aerodisk is introduced into the channel and ejected laterally through multiple nozzles to modify the flow field structure and reduce drag and aeroheating. In contrast to previous research employing a two-dimensional axisymmetric assumption, our innovation considers the structure of the exit nozzles and the spacing between nozzles. Due to multiple lateral nozzles, the connection thickness between nozzles can lead to asymmetric flow phenomena. Three-dimensional flow field simulation has been employed with the Reynolds-averaged Navier-Stokes (RANS) equations coupled with the shear stress transport (SST) k-ω turbulence model. The effects of the convergence half-angle of the channel inlet, the divergent angle of the nozzle, and the nozzle position on modifying the characteristics of the flow field are studied. Increasing the convergence half-angle of the channel inlet can further push away the reattachment shock, but when it exceeds 60°, the drag reduction performance degrades. Reducing the divergent angle of the nozzle and increasing the number of nozzles can reduce the drag coefficient and the peak value of the Stanton number. However, when the divergent angle is reduced to 10°, the performance of reducing drag and aeroheating is weakened. In the range of research parameters, when the convergence half-angle is 60°, the divergent angle is 15°, and the nozzles are located in the middle of the spike, compared with the plain spike-aerodisk model, the drag coefficient and peak Stanton number of the combined model are further reduced by 17.8 % and 34.8 %, respectively. Our findings confirm that a multi-nozzle can effectively reduce drag and aeroheating while the channel structure is viable in practice. • A new model of lateral jet without gas source is studied by 3-D numerical simulation. • The gas for the lateral jet is coupled with the outside flow. • A distribution form of multiple lateral nozzles is proposed. • A realistic 3-D simulation is conducted, enhancing its practical applicability. [ABSTRACT FROM AUTHOR]

A fast robust dive guidance scheme for a hypersonic vehicle is proposed based on the extended state observer and sliding mode observer. The three-degree-of-freedom centroid dynamical and kinematical equations containing model and aerodynamic uncertainties are established. A novel three-dimensional coupling relative dynamical model is described based on exact coordinate transformations. The fast robust dive guidance scheme considering navigation errors and uncertainties is derived with the help of extended state observer and sliding mode observer. An optimal control allocation is adopted and the actual commands of the angle of attack and bank angle are obtained via the second order actuator model. Finally, the performance and robustness of the novel dive guidance scheme is verified and validated via an air-breathing generic hypersonic vehicle. [ABSTRACT FROM AUTHOR]

For the BTT attitude tracking control problem of hypersonic vehicle, a state-error-space implementation expression of nonlinear H∞ attitude tracking control for above nonlinear coupling system is given firstly. Then basing on γ-energy-dissipation and L² gain performance criterion in nonlinear system theory, the smooth differentiable stored-energy function is designed, which subject to the Hamilton-Jacobi-Isaacs inequality. Following some assumptions, a local state-space solution of nonlinear H∞ attitude-tracking control problem for nonlinear coupling hypersonic vehicle system is obtained, by using Riccati differential equation of linear following system in local state-space. The local state-space is the neighborhood around the command state error space. Above approach avoids complicated solving process of Hamilton-Jacobi-Isaacs inequality, thus it's a good reference for engineering. [ABSTRACT FROM AUTHOR]