SR-72 Confirmed: Mach 6 Project Blackswift

It is extremely difficult to establish precise motion model for hypersonic flight vehicles (HFVs). However, the majority of the existing control techniques focus on model-based methodologies. This paper investigates a novel model-free controller for a continuous non-affine model of HFV. Firstly, the nonaffine vehicle dynamics is transformed into a pure feedback formulation consisting of velocity subsystem and altitude subsystem. Then, a model-free tracking control law is exploited for velocity subsystem. Furthermore, the developed model-independent control technique is expanded into the altitude subsystem that is a high-order dynamic system. The proposed model-free controller contains a Hurwitz stable term and a filtering term. In addition, compensated filters are devised to further strength robustness. The special novelty is that the addressed controller doesn't require accurate affine model, exhibiting fine universal property and strong robustness. Finally, theoretical conclusions are validated and the effectiveness of the design is verified by simulation results.

Flame oscillation characteristics in a strut-equipped dual mode combustor fueled with liquid kerosene were observed and discussed in this paper. A series of experiments and numerical simulations were carried out in the combustor both in lower inflow enthalpy condition (Ma = 2.0) and in higher inflow enthalpy condition (Ma = 2.8). The methods of high-speed photography and pressure measurement were used to record the basic data, and based on the basic data, the variation of flame area and the distribution law of wall pressure in different experimental conditions were analyzed to get the flame oscillation characteristics. Results indicated that the phenomenon of flame oscillation was caused by the variation of pilot flame strength and the adverse pressure gradient near the combustion region. Flame oscillation was distinguished into different status according to oscillation frequency and oscillation amplitude, and both the mass flow of oxygen and equivalence ratio could make a deep influence on the flame oscillation status. Flame oscillation characteristics were also closely related to the flowing state, and the difference of flame propagation process in supersonic and subsonic flowing conditions resulted in the distinction of flame oscillation characteristics. With the investigations in this paper, a depth understanding on flame oscillation in the dual mode combustor is achieved.

Evaluating the climbing performance of rocket-based combined cycle (RBCC) powered aircraft has a guiding role for single-stage to orbit. This study establishes a new modularized thrust model of the RBCC engine for low speeds (Ma∞ = 0.8–3) based on independent ramjet stream and pressure matching. The model can quickly estimate the quasi one-dimensional flow characteristics of secondary flow and primary flow at given runner geometry and operating conditions. Comparison with experimental results shows that the thrust model is correct. In this model, the influence of altitude, Mach number, and rocket flow on thrust and specific impulse is considered. The model was used to optimize the climbing trajectory of RBCC powered aircraft with a typical lifting-body. The comparison of RBCC propulsion and pure rocket propulsion shows that the former offers propellant saving advantages. During the climb, the RBCC powered aircraft needs to strictly control the air flow rate and ensure the pressure matching in the flow path to improve propulsion efficiency.