Purpose – The purpose of this paper is to present a novel guidance law for hypervelocity descent to a stationary target such that the impact angle and impact velocity can be constrained. Design/methodology/approach – The proposed method is based on inverse dynamics and is designed using a third-order Bézier curve approximation to the reference trajectory. Findings – Simulations indicate that the proposed law is able to satisfy impact angle and impact velocity constraints as well as follow control and path limitations in the case of guidance under perturbations. Comparisons with other methods also indicate better performance. Research limitations/implications – The onboard implementation requires an offline selection of Bézier parameters. Practical implications – The presented scheme could be extremely important for further research on automated onboard control of impact angle and velocity for both re-entry and terminal guidance laws. Originality/value – This paper presents an innovative method for the solution of an inverse dynamics-based guidance law using Bézier curve approximation.

In this paper, a guidance scheme is developed for tracking constrained entry trajectory which is updated onboard. From an initial offline trajectory, the guidance system updates trajectories at every step of control command generation. This scheme models state error dynamics as a linear time varying system and updates the trajectory using a pseudospectral method. The solution provides an updated and optimal trajectory from the present position to the terminal state satisfying the path constraints. The guidance system continues updating the online trajectories and generates the control commands. This method is different from tracking methods purely based on linear quadratic regulator theory because it utilizes the pseudospectral method in generating control command; but it is also different from pseudospectral guidance because generation of new reference trajectories is done onboard. The method is validated through a number of test cases for initial state perturbations, aerodynamics and atmosphere modeling errors. In order to demonstrate improved accuracy relative to other methods, the method is also tested against linear quadratic regulator and pseudospectral guidance schemes.

The paper presents a gauss pseudospectral solution for the trajectory optimization problem of a hypersonic vehicle. Determination of optimal trajectory of a hypersonic vehicle is of great interest due to the different path and boundary conditions that need to be met for high accuracy. Recent researches show that pseudospectral methods are capable of providing high accuracy in computationally efficient manner. The hypersonic vehicle optimized here is accelerated through solid rocket propulsion to mach 3.5 and after ejection of the rocket motor it is accelerated to mach 6 where it starts cruise for reaching target. The flight profile which is divided into boost, ascent, cruise and dive phase is optimized using multi-phase implementation programme of gauss pseudospectral method GPOPS. The optimization is carried out in 2D assuming non-rotating flat earth assumption and considering propulsion, dynamic and atmospheric constraints. The results are then analyzed for max range and max final velocity and hit angle. The results are found to be feasible.

An explicit entry guidance law has been developed using inverse dynamics approach. The inverse dynamics problem is solved through Bézier curve approximation of the vehicle trajectory. Most important and novel feature of the developed guidance law is its ability to satisfy the terminal angular and velocity constraints besides position constraints. Through shape preserving 'Bézier parameters' the guidance law has the ability to control terminal velocity. For entry glide flight the guidance law incorporates limits on acceleration and attack angle which are converted from path constraints. The results demonstrate remarkably good efficiency in meeting terminal constraints.

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