Optimal periodic control is an effective technique to reduce aerodynamic heating and fuel consumption of hypersonic cruise vehicle. Herein this optimal control problem has been solved by nonlinear programming and passed the posteriori check of optimality. The results indicate that lift coefficient and velocity in dynamical model could be recognized as constants. Accordingly, the original 3D system consists of velocity, flight path angle, and altitude could be decoupled into a 2D subsystem and an 1D one. The 2D subsystem could describe the correlation between flight path angle and altitude. And the period length is mainly dependent on the maximum altitude difference. The 1D subsystem has been proved to be feasible to describe the variation of kinetic energy or velocity. On basis of the subsystems, the heating and fuel performances of periodic cruise have been studied. The heating performance is mainly dependent on maximum altitude difference, and the fuel consumption is mainly dependent on the drag coefficient. The features concluded in this work can support rapid trajectory planning or suboptimal feedback design of hypersonic cruise vehicle.

Periodic cruise has been proven an effective trajectory to conserve fuel and alleviate aerodynamic heating for hypersonic cruise vehicles. This work studies how to adapt a hypersonic cruise vehicle with active cooling to periodic cruise. In this adaption, payload capacity is to maximize, whereas the cooling requirement is to reduce. The differences in requirements for subsystems between periodic and steady cruises have been made clear. The results indicate that periodic cruise principally transfers burden of thermal protection to structure, and that periodic cruise is more effective to trade payload capacity for larger reduction of cooling requirement. Afterwards, impacts of design parameters of vehicle on payload capacity and cooling requirement have been discussed. The results indicate that an insulation thinner than 3 mm, a planform loading lower than 220 kg/m2, or a large engine is not suggested for the vehicle studied herein. This work figures out the correlation between design parameters of vehicle and features of periodic cruise trajectory. It could help to improve the feasibility of periodic cruise for a hypersonic vehicle, which is significant for realization of long-range hypersonic cruise.

In this paper, the attitude determination problem from two vector observations is revisited, incorporating the redundant equality constraint obtained by the dot product of vector observations. Analytical solutions to this constrained attitude determination problem are derived. It is found out that the studied two-vector attitude determination problem by Davenport q-method under the dot product constraint has deterministic maximum eigenvalue, which leads to its advantage in error/perturbation analysis and covariance determination. The proposed dot product constrained two-vector attitude solution is applied then to solve several engineering problems. Detailed simulations on spacecrafts attitude determination indicate the efficiency of the proposed theory.

The endurance of an aircraft can be considerably extended by its exploitation of the hidden energy of a wind gradient, as an albatross does. The process is referred to as dynamic soaring and there are two methods for its implementation, namely, sustainable climbing and the Rayleigh cycle. In this study, the criterion for sustainable climbing was determined, and a bio-inspired method for implementing the Rayleigh cycle in a shear wind was developed. The determined sustainable climbing criterion promises to facilitate the development of an unpowered aircraft and the choice of a more appropriate soaring environment, as was demonstrated in this study. The criterion consists of three factors, namely, the environment, aerodynamics, and wing loading. We develop an intuitive explanation of the Raleigh cycle and analyze the energy mechanics of utilizing a wind gradient in unpowered flight. The energy harvest boundary and extreme power point were determined and used to design a simple bio-inspired guidance strategy for implementing the Rayleigh cycle. The proposed strategy, which involves the tuning of a single parameter, can be easily implemented in real-time applications. In the results and discussions, the effects of each factor on climbing performance are examined and the sensitivity of the aircraft factor is discussed using five examples. Experimental MATLAB simulations of the proposed strategy and the comparison of the results with those of Gauss Pseudospectral Optimization Software confirm the feasibility of the proposed strategy.

Aircraft longitudinal dynamics is approximated by short-time mode and phugoid mode from experience. In this article, a rigorous mathematical method is provided based on the singular perturbation theory to deal with this decoupling problem. The longitudinal decoupling and singular perturbation are first introduced. The longitudinal equations are normalized and transformed into a canonical form to extract the perturbation coefficient. Thus, the entire dynamics model is partitioned into boundary-layer equations and slow equations according to singular perturbation theory, which presents a proof to the experience method. The simulation results show that the proposed decoupling approach is sufficiently excellent to approximate the underlying model both in time domain and frequency domain.