An explicit Guidance.law is developed for a Reentry vehicle. Motion is constrained to a three-dimensional Bezier curve. Acceleration commands are derived by solving an inverse problem that combined with differential flatness approach. Trajectory is related to Bezier parameters. A comparison with pure proportional navigation shows the same accuracy, but a higher capability for optimal trajectory to some degree. Other advantages such as trajectory representation with minimum parameters, applicability to any Reentry vehicle configuration and any control scheme, and Time-to-Go independency make this Guidance.approach more favorable.

An advanced Guidance.law is developed for Reentry phase of a Reentry vehicle. It can achieve small miss distance and desired impact attitude angle, simultaneously. To meet this requirement, a Guidance.law based on the fuzzy logic control approach is developed. It is partitioned into three stages. This Guidance.law does not require linearization of missile engagement model. Line-of-sight angle and flight path angle are used to constitute the rule antecedent of the Guidance.law to shape an appropriate flight trajectory for engagement. Numerical simulation results and comparison with an existing algorithm demonstrated that the proposed Guidance.law offers satisfactory performance and robustness, fulfilling its design goals.

Trajectory optimization is a familiar method for most of re-entry and Re-usable vehicles. This is because of the ability to include almost all of the problem constraints without facing restrictions such as time & Calculation issues. Adding or removing constraints in trajectory optimization problem has significant effects on overall optimization performance which even can upgrade the method to an on-line process. Most of optimization Algorithms such as nonlinear-programming need an initial guess and are also sensitive to it. Hence in this research management of initial guess is done to remove some constraints from optimization problem and transfer them to initial phase. Accordingly an effort is conducted through using a Classic Guidance.method to satisfy constraints of distance error and angle of impact command. The output of Guidance.initial guess is then fed to the optimization problem. 6Dof Simulation results show the increase of optimization performance via reduced number of iterations and Optimization time and increased solution accuracy.

An optimal explicit Guidance.law that maximizes terminal velocity is developed for the Reentry of a vehicle to a fixed target. The equations of motion are reduced with differential flatness approach and acceleration commands are related to the parameters of trajectory. An optimal trajectory is determined by solving a real-coded genetic algorithm. For online trajectory generation, optimal trajectory is approximated. The approximated trajectory is compared with the pure proportional navigation and genetic algorithm solutions. The near optimal terminal velocity solution compares very well with these solutions. The approach robustness is examined by Monte Carlo simulation. Other advantages such as trajectory representation with minimum parameters, applicability to any Reentry vehicle configuration and any control scheme, and Time-to-Go independency make this Guidance.approach more favorable.

In this paper, a multi-objective Guidance.scenario has been developed which could be used to improve the accuracy of sub-orbital modules at the entry to the earth’s atmosphere. Developed algorithm could be used for the trajectory shaping and adjusting of the trajectory relative to the desired position. To achieve defined objectives, it has been organized in three phases relative to different layers of trajectory. In the first phase, using of sensitivity functions which are of less computational burden, improving the accuracy according to the reference trajectory is done. In the second phase, trajectory shaping which is required to achieve desired flight performance is applied which could be designed and performed online in the mission. Finally in the last phase which is relative to low altitudes, improving of the accuracy according to homing rules is performed. Validation of developed algorithm using of a sample Guidance.problem is presented finally.

A numerical trajectory optimization study of two types of lifting-entry Reentry vehicle has been presented at low suborbital speed of 4.113 km/s and -15 degree entry angle. These orbital speeds are typical of medium range ballistic missile with ballistic range of approximately 2000 km at optimum burnout angle of approximately 41 degree for maximum ballistic range. A lifting Reentry greatly enhances the Reentry range which leads to a higher overall range of approximately 3000 km for the same DV. The optimum Reentry angle of lifting Reentry vehicle for medium range missiles under constrained g-load lies between -15 to -20 degree for limited g-load trajectories. These entry angles result in high decent rates and the vehicle quickly approaches the heat rate boundary. The heat rate problem is more severe for small size vehicle because of small nose-radius. Limiting the heat rate restricts the trajectory and lowers the downrange/cross-range performance of the Reentry vehicle. A wing-body Reentry vehicle has a larger nose radius as compared to a waverider which results in comparatively low heat rates during flight. This type of a vehicle has lower lift-to-drag ratio and therefore lesser range in comparison to a waverider type design. The performance of the two vehicle types is studied at various heat rate limits with the objective to calculate the optimum control deflections that would maximize the cross range. The results provide performance of the two designs vis-a-vis maximum heat rate constraint at the stagnation point along with the required control history. General pseudo-spectral optimal control software, GPOPS has been used for the optimal trajectory studies.

In this research a perturbation based Guidance.method is developed for non Keplerian problem, Problem is linearized in the presence non-gravitational forces like aerodynamic. so it can improve the performance of C* Guidance.for Reentry problems. In this study developed method is used for a Reentry zuidance accuracy and performance. Results showed significant increases in accuracy compared to Keplerian approaches.

The robust multi-disciplinary, multi-objective shape optimization of re-entry capsule with aero-thermodynamic, trajectory, stability and the geometry considerations are presented in this paper. In this research, the results of maximizing the volumetric efficiency of the capsules while minimizing the ballistic coefficient and the longitudinal stability derivative with considering uncertainties are discussed in presence of some constraints on geometry, heating load, and load factor. To reduce the time and cost of robust optimization, the Adaptive Monte Carlo Simulation technique is used which decreases the number of required evaluations within the robust optimization process. Utilizing the constrained multi-objective genetic algorithm will result in a collection of robust optimal solutions. The results show that the performance of obtained robust optimal configurations is in a way that the considered constraints aren’ t violated with 99. 8% of confidence level even in the presence of uncertainties.

We present a 33 years-old smoker male with dyspnea on exertion, the cause of which was finally identified as atrial tachyarrhythmia after performing echocardiography, coronary angiography, right, and left sided cardiac catheterization During electrophysiology study; upper loop Reentry (ULR) a rare form of atypical Atrial flutter was diagnosed and ablated by conventional technique. New mapping technology improved our understanding of the mechanism and pathways of arrhythmia, and allowed complex ablations made easier and more cost-effective.