Thrust Failure Research Articles

Gliding Footprint Calculation Method for Aircraft with Thrust Failure Based on Six-Degree-of-Freedom Flight Envelope and Back-Propagation Artificial Neural Network

In hostile environments, engine damage is of particular concern since the engine is the only component to generate thrust that affects survivability. For an aircraft suffering thrust failure, the forced landing sites should be identified within the gliding footprint, which is the reachable region on the ground. This paper proposes two calculation methods to obtain the gliding footprint by finding a series of boundary points with maximum gliding distance around the aircraft. Method 1 models the thrust-failed aircraft with six-degree-of-freedom (6-DOF) flight dynamics and adopts a novel 6-DOF unpowered-flight envelope to characterize its maneuvering capabilities. Given the initial altitude when thrust failure occurs, Method 1 determines all feasible gliding distances around the aircraft based on the constructed 6-DOF flight envelope and selects the landing points of maximum gliding distances along different radial directions as the boundary points. Method 2 employs the Back-Propagation Artificial Neural Network (BP-ANN) to predict the boundary points. Using the well-trained BP-ANN, this method can estimate the maximum gliding distances with only the initial altitude and radial directions. Simulations are conducted to analyze these two methods. Compared with conventional methods using point-mass flight dynamics, Method 1 considers more flight constraints, and the gliding footprint area is reduced by 20.79%. These results are relatively conservative and can improve the safety threshold of forced landing sites. Method 2 can estimate the gliding footprints (encircled by the boundary points under the entire operational altitude and full radial direction) in real time, which reserves more response and action time for aircraft forced landing.

Abort-Safe Spacecraft Rendezvous on Elliptic Orbits

We develop a spacecraft rendezvous policy that ensures safe, collision-free trajectories under various thrust failure scenarios. We use backward reachable sets (RSs) to characterize the unsafe region where, if a failure occurs, a collision between a chaser and a target spacecraft cannot be avoided with the remaining available thrust. The chaser spacecraft is guided toward the target via model predictive control (MPC) that ensures abort safety by avoiding the unsafe region, which is locally convexified with half-spaces. Simulations of the rendezvous policy on various orbits demonstrate that the approach ensures safe aborts in the event of multiple thruster failures, passive abort safety under total thruster failure, and achieves some robustness to unmodeled orbital perturbations.

Feasibility analysis of solar thermal propulsion system with thermal energy storage

Possessing relatively high specific impulse and moderate thrust levels, solar thermal propulsion (STP) is a promising candidate in spacecraft propulsion system. However, the traditional solar thermal propulsion system suffers from thrust failure in the shadow area, which seriously affects its applicability. In this paper, we investigate feasibility of regenerative solar thermal propulsion system (RSTP) incorporating thermal energy storage, which can effectively overcome unmatched synchronous working time and illumination time. A numerical model for RSTP considering the whole energy transfer process from light concentrating, heat storage, to thrust generation is built, which is verified by experiment measurements with relative errors less than 15 %. The result shows that the maximum time to complete heat storage is about 4000 s, which is within the illumination time for low Earth orbit. In the solar eclipse region, the thrust (Ft) and the specific impulse (Isp) of the system increase with the propellant flow rate, which can reach about 2 N and 690 s, respectively. What’s more, the system can operate for around 100 s continuously at the maximum thrust in the shadow area. This work provides alternative approaches for microsatellite propulsion with high specific impulse, high thrust, and continuous operation despite presence of solar eclipse.

Single and diagonal double thrust failure assessment of quad-copter at starting

This papers deals with the thrust failure assessment of quad-copter at starting. This has been achieved by performing stability and fault analysis of quad-rotor helicopter wherein PD and PID controllers used for analysis of an advanced nonlinear cross-coupled dynamic system at normal and fault conditions. Normal, single thrust and diagonal double thrust failure conditions have been introduced in the system. Response of the system has been studied for different types of reference input at normal as well as at both types of thrust failure conditions. Specific changes have been observed in output pattern due to the presence of fault. Based on comparative study, an algorithm has been proposed to verify whether the system is normal or suffering from thrust failure at starting. Practical validation of algorithm has been pursued to authenticate the effectiveness of the approach. As the test is performed at starting, it is less affected by external extremities.

In situ stress magnitudes at the toe of the Nankai Trough Accretionary Prism, offshore Shikoku Island, Japan

AbstractQuantifying the orientation and magnitude of tectonic stresses is essential toward understanding deformation and faulting in subduction zones. However, constraints on in situ horizontal stress magnitudes (Shmin and SHmax) are rare. We estimate Shmin and SHmax at Ocean Drilling Program Site 808 at the toe of the Nankai accretionary prism offshore Japan, using coupled constraints from (1) the width of wellbore breakouts together with estimates of rock strength and a model describing stress redistribution at the borehole wall and (2) limits on regional differential stress defined by failure on preexisting faults. Our analysis extends from 175 to 915 m below seafloor (mbsf) and spans the active frontal thrust. For an upper bound on rock unconfined compressive strength (UCS) and assuming hydrostatic formation pore pressure, Shmin and SHmax (referenced to the seafloor) increase from 6.5 MPa at 175 mbsf to 17.4 MPa at 915 mbsf, with the stress state gradually transitioning from a thrust or strike‐slip faulting regime above 800 mbsf to a normal faulting regime below. For cases with higher formation pore pressure, horizontal stresses are slightly lower but follow a similar pattern. We show that estimated Shmin and SHmax are strongly dependent on UCS, breakout width, and friction coefficient, all of which are characterized by uncertainty. Our results suggest that the prism is near thrust failure in the upper ~300 mbsf, but far from failure below. This may be reconciled with active thrusting if thrust faults are locally weaker than the surrounding rock or if SHmax fluctuates during the seismic cycle.

Robust control for constant thrust rendezvous under thrust failure

A robust constant thrust rendezvous approach under thrust failure is proposed based on the relative motion dynamic model. Firstly, the design problem is cast into a convex optimization problem by introducing a Lyapunov function subject to linear matrix inequalities. Secondly, the robust controllers satisfying the requirements can be designed by solving this optimization problem. Then, a new algorithm of constant thrust fitting is proposed through the impulse compensation and the fuel consumption under the theoretical continuous thrust and the actual constant thrust is calculated and compared by using the method proposed in this paper. Finally, the proposed method having the advantage of saving fuel is proved and the actual constant thrust switch control laws are obtained through the isochronous interpolation method, meanwhile, an illustrative example is provided to show the effectiveness of the proposed control design method.

Adaptive Flight-Control Design Using Neural-Network-Aided Optimal Nonlinear Dynamic Inversion

A neural-network-aided nonlinear dynamic inversion-based hybrid technique of model reference adaptive control flight-control system design is presented in this paper. Here, the gains of the nonlinear dynamic inversion-based flight-control system are dynamically selected in such a manner that the resulting controller mimics a single network, adaptive control, optimal nonlinear controller for state regulation. Traditional model reference adaptive control methods use a linearized reference model, and the presented control design method employs a nonlinear reference model to compute the nonlinear dynamic inversion gains. This innovation of designing the gain elements after synthesizing the single network adaptive controller maintains the advantages that an optimal controller offers, yet it retains a simple closed-form control expression in state feedback form, which can easily be modified for tracking problems without demanding any a priori knowledge of the reference signals. The strength of the technique is demonstrated by considering the longitudinal motion of a nonlinear aircraft system. An extended single network adaptive control/nonlinear dynamic inversion adaptive control design architecture is also presented, which adapts online to three failure conditions, namely, a thrust failure, an elevator failure, and an inaccuracy in the estimation of . Simulation results demonstrate that the presented adaptive flight controller generates a near-optimal response when compared to a traditional nonlinear dynamic inversion controller.

Reasonable Reinforcement Ratio of CRC+AC Composite Asphalt Pavements

The longitudinal reinforcement design was analyzed under current specifications of cement concrete pavement design for highway, considering the structural characteristics and limitations of existing studies on continuously reinforced concrete and asphalt concrete (CRC+AC) composite pavements. By using heat transfer theory and the finite element method, the temperature effect of the asphalt concrete (AC) layer was examined, and the influence of the temperature effect on the longitudinal reinforcement ratio of CRC+AC composite pavements was calculated and analyzed. The results show that (1) the longitudinal reinforcement design of CRC+AC composite pavements can disregard spalling, seepage, and thrust failure and only consider the tensile failure of reinforcement; (2) the longitudinal reinforcement ratio of CRC+AC composite pavements can be reduced through the efficient heat insulation of the AC layer, for instance, when the thickness of the AC layer is 10 cm, the longitudinal reinforcement ratio of the CRC layer can be reduced by approximately 0.12%; and (3) the sliding stent is recommended to be used in reinforcement erection, with banding method employed for jointing longitudinal reinforcement with an overlapped length that is approximately 35 times of the reinforcement diameter.

Emergency Flight Planning Applied to Total Loss of Thrust

Autopilot systems are capable of reliably following flight plans under normal circumstances, but even the most advanced flight-management systems cannot provide robust response to most anomalous events including in-flight failures. This paper describes an emergency flight-management architecture that can be applied to piloted or autonomous aircraft, with focus on the design and implementation of an adaptive flight planner (AFP) that dynamically adjusts its model to compute feasible flight plans in response to events that degrade aircraft performance. A two-step landing-site selection/trajectory generation process defines safe emergency plans in real time for situations that require landing at an alternate airport. A constraint-based search algorithm selects and prioritizes feasible emergency landing sites, then the AFP synthesizes a segmented trajectory to the best site based on postfailure flight dynamics. The AFP architecture is general for any failure situation; however, operational success is guaranteed only with accurate postfailure performance characterization and a trajectory generation strategy that respects degraded flight envelope boundaries. A real-time segmented trajectory planning algorithm and case study results are presented for total loss of thrust failure scenarios. This emergency is surprisingly common and necessitates an immediate approach and landing without a go-around option.

Coulomb Stress Transfer and Tectonic Loading Preceding the 2002 Denali Fault Earthquake

Pre-2002 tectonic loading and Coulomb stress transfer are modeled along the rupture zone of the M 7.9 Denali fault earthquake (dfe) and on adjacent segments of the right-lateral Denali–Totschunda fault system in central Alaska, using a three-dimensional boundary-element program. The segments modeled closely follow, for about 95°, the arc of a circle of radius 375 km centered on an inferred asperity near the northeastern end of the intersection of the Patton Bay fault with the Alaskan megathrust under Prince William Sound. The loading model includes slip of 6 mm/yr below 12 km along the fault system, consistent with rotation of the Wrangell block about the asperity at a rate of about 1°/m.y. as well as slip of the Pacific plate at 5 cm/yr at depth along the Fairweather–Queen Charlotte transform fault system and on the Alaska megathrust. The model is consistent with most available pre-2002 Global Positioning System (gps) displacement rate data. Coulomb stresses induced on the Denali–Totschunda fault system (locked above 12 km) by slip at depth and by transfer from the M 9.2 Prince William Sound earthquake of 1964 dominated the changing Coulomb stress distribution along the fault. The combination of loading (∼70–85%) and coseismic stress transfer from the great 1964 earthquake (∼15–30%) were the principal post-1900 stress factors building toward strike-slip failure of the northern Denali and Totschunda segments in the M 7.9 earthquake of November 2002. Postseismic stresses transferred from the 1964 earthquake may also have been a significant factor. The M 7.2–7.4 Delta River earthquake of 1912 (Carver et al. , 2004) may have delayed or advanced the timing of the dfe, depending on the details and location of its rupture. The initial subevent of the 2002 dfe earthquake was on the 40-km Susitna Glacier thrust fault at the western end of the Denali fault rupture. The Coulomb stress transferred from the 1964 earthquake moved the Susitna Glacier thrust fault uniformly away from thrust failure by about 100 kPa. The initiation of the Denali fault earthquake was advanced by transfer of 30–50 kPa of positive Coulomb stress to the Susitna Glacier fault (Anderson and Ji, 2003) by the nearby M 6.7 Nenana Mountain foreshock of 23 October 2002. The regional tectonic loading model used here suggests that the Semidi (Alaska Peninsula) segment of the megathrust that ruptured in 1938 ( M 8.2) may be reloaded and approaching failure.

Modelling Quaternary thrusting in Himalayas and its geodynamic constraints in Southern Tibet

The occurrence of Quaternary thrusting in Himalayas and its geodynamics constraints in Southern Tibet is modelled using stress simulation analysis. 2D non-linear elastic and homogeneous wedge models, representing cross-sections of the Himalayas and Tibet are used. Simulated stresses for a set of boundary conditions, representing building up of Himalayas and Southern Tibet, reveals the region of thrust failure gradually recedes away from the wedge towards the base (lower boundary) with a decrease in the strength of the base. Thus, the result favours the preposition that a strong and a weak basal (Main Himalayan Thrust; MHT) respectively, below Himalayas and Southern Tibet is responsible for presence and restricting the extension of Quaternary thrusting in these regions. A decrease in strength of MHT from the Himalayas to Tibet is also supported by observational evidence and thermal modelling, imply partial melting along MHT.

Critical wedges in three dimensions: Analytical expressions from Mohr‐Coulomb constrained perturbation analysis

We present simple analytical expressions for evaluating three‐dimensional stress fields in critical wedges (Coulomb failure throughout) that are deforming within an oblique convergent zone. We assume that the load and geometry variations in the lateral direction, and the topographic slope, are relatively small. The stress state of a two dimensional critical wedge is perturbed by admitting a small lateral shear, which is accommodated (to maintain criticality) by a reduction in the dominant normal compressive stress. Cohesionless cases are further simplified with Taylor series expansions in the topographic slope. The analytical expressions distinguish the behavior of strong base wedges associated with steep slopes from weak base wedges with more modest slopes, and are reliable for lateral shear values as large as half the lithostatic load. In the weak base case where the vertical shear is small, the orientations of the principal stresses are very sensitive to the perturbation. As the lateral shear increases through relatively small values, the roles of the lateral and vertical coordinate axes are interchanged, with a resultant transition from predominantly thrust failure to strike slip failure. Transition to strike slip in the strong base case is more gradual. The particular value of horizontal shear for which transition occurs also depends on the difference of the minor normal stresses. We produce an analytical expression predicting displacement patterns compatible with those observed in natural and analog orogens. Displacement partitioning is predicted for weak base wedges due to minor changes in lateral boundary conditions associated with variable orogen geometry.

Instantaneous Impact Point Analysis

THE FLIGHT PROFILE of a mission in case of thrust failure prior to attainment of orbital speed is considered. Specifically the impact point corresponding to a given set of thrust cutoff conditions is analyzed. Analytical solutions are obtained for various impact parameters. Several graphical solutions are formulated for the purpose of generating such information, often referred to as the instantaneous impact point (IIP) trace, for mission planning purposes. A new form of graph paper with trigonometric scales is introduced.