Thrust Termination Research Articles

Regional tectonic dynamics in Central Iran: Unveiling the interplay of fault systems through morphotectonic and seismological analyses in the Shotori mountains

Iran, located at the convergence of the Eurasian and Arabian tectonic plates, is a region of significant geologic and tectonic interest. This setting gives rise to complex tectonic dynamics that are crucial for understanding the seismicity and geological evolution of the area. This study provides novel insights into the tectonic dynamics of Central Iran, with a particular focus on the Shotori Mountains. Employing a combination of satellite imagery, earthquake catalog analysis, and field observations, we have studied the complex interactions among active fault systems in this part of Iran. Our investigation highlights the significant interactivity of these faults, especially at the convergence point of the Nayband strike-slip fault with the Esfandiar and Shotori thrust faults. This area is characterized by a high frequency of reverse mechanism earthquakes, primarily occurring in shallower crustal layers. A notable aspect of our findings is the identification of a distinct pattern of seismic activity linked to the interaction between different fault types. The Nayband shear zone, for instance, is critically responsible for right-lateral, oblique reverse faulting, and strike-slip events. This study also reveals a novel aspect of tectonic behavior in Central Iran: the correlation between strike-slip fault systems and their thrust terminations, influenced by the rotational dynamics of these faults. Our analysis suggests that the activation of strike-slip faults can precipitate the activation of their thrust terminations, a phenomenon particularly evident at their intersection points. This insight is crucial for understanding regional tectonic processes and could significantly impact seismic hazard assessments in Central Iran. Furthermore, the interaction between the Nayband strike-slip fault and its thrust terminations, such as the Shotori and Esfandiar faults, highlights areas of heightened tectonic activity. This study not only advances our understanding of the seismic and tectonic landscape of Central Iran but also has broader implications for regional tectonic studies and seismic risk management.

A novel in-flight thrust modulation technique for SPRM: proof of concept

Thrust modulation (termination or reduction) is one of the most sophisticated topics in rocket motors. Thrust termination is employed when combustion must be terminated to ensure proper stage separation, to avoid motor explosion, to attain certain range, or for research purposes. While liquid and hybrid propellant rocket motors have the ability to extinguish thrust, thrust termination in solid propellant rocket motors (SPRMs) need the use of specialized technology. In-flight thrust termination of (SPRMs) can be achieved by sudden and sufficient increase in throat area. Increasing throat area causes high depressurization rate which consequently leads to extinguishing the rocket motor. In contrast, in-flight thrust reduction can be theoretically attained either by reducing chamber pressure to a new equilibrium level or by reducing the divergent section length. The objective of the present paper is to prove the concept of using Linear Shaped Charge (LSC) for thrust modulation; a technique novel to SPRM applications. Thrust termination concept is proved via a set of static firing tests on a standard test motor. In addition, a mathematical model is developed to predict the drop in thrust due to cutting the nozzle at any arbitrary location. The model is validated by comparing with published experiments for thrust termination and reduction. A parametric study is conducted based on model results. It is confirmed that by cutting the nozzle along its divergent section, thrust reduction less than 20% can be attained. Further reduction can be achieved by cutting the nozzle along its convergent section.

Thrust termination of solid rocket motor

Rocket motors are engines that create the necessary thrust for the rocket motion. There are different types of rocket motors based on the propellant state, such as solid propellant rocket motors, liquid propellant rocket motors, and hybrid propellant rocket motors. One of the biggest disadvantages of solid propellant rocket motors, in comparison to liquid and hybrid propellant rocket motors, is that they are extremely difficult to extinguish, necessitating the use of specific devices. This paper reviews various ways for thrust termination such as fluid injection, rapid increase in throat area, and sudden opening of an additional port at the forward section of the motor, which increases the depressurization rate (dp/dt) required for extinguishing. The rate of depressurization varies depending on propellant components, combustion pressure, and exhaust pressure, and may be investigated using experimental approaches. The change in the critical area for a motor can be predicted by using MATLAB code to ensure the complete extinguishing by decreasing the pressure under the deflagrationlimit with high depressurization rate.

Instantaneous Impact Point Guidance with Coast Arcs for Solid Rockets

This paper proposed an analytical iterative guidance method with the desired instantaneous impact point constraint for solid rockets in “burn-coast-burn” trajectory mode. Solid rocket motors expect to remove the thrust termination mechanism to increase the structural strength and launch reliability, which induce new difficulties and challenges to the guidance problems. In terms of the “Hohmann transfer” principle, a pointing algorithm is deduced in depth to establish the theoretical relations among the ignition time, the required velocity vector, and the orbital element constraints and provides the analytical expression of the ignition time. Then, an analytic solution of the required velocity vector is derived based on orthogonal and nonorthogonal velocity vectors, and a complete guidance logic is used to solve the target orbit elements satisfying the desired instantaneous impact point. Finally, the application of the developed theoretical algorithm in this paper is conducted using a two-stage solid rocket. The proposed guidance method is verified by Monte Carlo simulations, and the testing results demonstrate the adaptability, strong robustness, and excellent performance for different desired impact point missions.

Autonomous ascent guidance with multiple terminal constraints for all-solid launch vehicles

Removing the thrust termination mechanism of solid rocket motors is an inevitable trend but reduces the ability of terminal multi-constraints. This paper presents an improved analytic algorithm for rapid and automated ascent guidance of responsive small solid launch vehicles shutting off by fuel exhaustion. The proposed new analytical solution is solved for the two-point boundary value problem with coast arc and constraints of the given burn arc. A velocity increment control method is derived from the minimum steering angle constraints to dissipate the extra energy and an improved pointing algorithm is constructed to restrain the coupling vectors caused by the process of velocity increment control. Then, the solution of the improved pointing algorithm provides the direction of the velocity increment control and the effect of the additional coupling vectors on terminal constraints is suppressed by this direction. Finally, the application of the developed theoretical algorithm in this paper is conducted by using the last stage of all-solid launch vehicles. The proposed guidance method is verified by Monte Carlo simulations and the testing results demonstrate the adaptability, strong robustness and excellent performance for different orbital-insertion missions.

Multi-constrained ascent guidance for solid propellant launch vehicles

Solid rocket motors expect to remove the thrust termination mechanism to increase the strength of structure and reduce the cost, which induce new difficulties and challenges to ascent guidance. This paper presents an ascent guidance algorithm for small solid launch vehicles (SSLVs) which shut off by fuel exhaustion. A pointing algorithm is tailored for the baseline guidance algorithm of SSLVs with constraints of the velocity vectors and the position vectors. Subsequently, an energy management technique is developed for dissipating the extra energy that the solid rockets have when shutting off by fuel exhaustion. The energy management technique primarily allocates the energy to different sub-stages, while an attitude control energy management method is applied to the dissipation of the excess energy at one stage. Finally, the proposed guidance algorithm is verified by Monte Carlo simulations in which the dispersions of vehicle mass, operation temperature of motors and aerodynamic coefficient as well as random wind shear are considered. The testing results demonstrate the capability, strong robustness and excellent performance of the proposed guidance algorithm.

Insights from heterogeneous structures of the 1999 Mw 7.6 Chi‐Chi earthquake thrust termination in and near Chushan excavation site, Central Taiwan

AbstractWe describe and analyze the surface and subsurface deformation of the 1999 Chi‐Chi earthquake thrust termination of the Chelungpu fault in and near the Chushan excavation site, central Taiwan. In order to minimize damage to engineering structures within a deformation zone and formulate regulations for earthquake fault zones and fault setbacks, one needs to know the characteristics of the deformation zone and the connection between surface and subsurface deformation. The surface deformation zone of high strain induced by the earthquake faulting ranges from 15 to 70 m in width, and characterized by a 0.5 to 2 m high escarpment is much wider in the hanging wall. Exposures in the trench, 40 m long and 10 m deep, excavated across the earthquake ground rupture, show on the one hand the heterogeneous structure of a steep, monocline‐like fold. On the other hand, strikingly different surface deformation profiles on either side of the 14 m wide trench, i.e., semiparabola‐like and monoclinal, do not reflect in any obvious way the subsurface structure. The analysis of our detailed mapping results along with well logs suggests that the significant width variation of the surface deformation zone is attributed to secondary faults branching from the dominant fault at several tens of meters depth. The surface profile of the escarpment is controlled by the depth of the relevant fault tip, and the subsurface heterogeneous structure formed during at least four earthquakes.

Mathematical modeling and analysis of cutoff impulse in a liquid-propellant rocket engine

Thrust termination transient behavior of liquid-propellant rocket engines is important for launch vehicle to achieve the desired final velocity and, hence, fulfill the desired mission in placing a satellite in the intended orbit. A mathematical model has been developed for an open-cycle engine to predict the transient behavior of engine components, obtain the pressure changes of the combustion chamber, and to determine the cutoff impulse. By employing this model, the engine shutdown process has been simulated in four time intervals: (1) the duration from when cutoff command is issued to the time when the cutoff valves start to close, (2) closing of the cutoff valves, (3) discharge of combustion products from the chamber, and (4) the duration of the phase change and pressure fluctuations. The propellant flow has been modeled one-dimensionally in the cutoff valve and thermodynamically in the cooling channels and the combustion chamber. The results indicate that the time duration of the first two stages and the working pressure of the engine during the transmission of the cutoff command have considerable impacts on the increase or reduction of the thrust force. Also, with the improvement in modeling accuracy and the complete development of the engine processes, the results indicate a maximum error of 9% compared with the 15–41% error in the calculation of cutoff impulse achieved by previous works, which demonstrates the enhanced accuracy of the present modeling.

Flight-Path Angle Control for Cutoff Insensitive Guidance

A cutoff insensitive guidance scheme is proposed for strategic missile systems not equipped with thrust termination systems. The main idea behind this scheme is to manipulate the current flight-path angle to follow the required flight-path angle. For this, a routine to obtain the required flight-path angle is set up by reorganizing the equations comprising the Lambert routine. Compared with existing schemes, the proposed scheme is more robust to motor performance uncertainty; it is also simpler and has a lighter calculation load. It is shown that the algorithm has good performance through the computer simulation.

Kick Solid Rocket Motor Multidisciplinary Design Optimization Using Genetic Algorithm

In this paper, a multidisciplinary design optimization (MDO) approach of a solid propellant kick rocket motor is considered. A genetic algorithm optimization method has been used. The optimized kick solid rocket motor (KSRM) is capable of delivering a small satellite of 200 kg to a circular low earth orbit (LEO) of 600 km altitude. The KSRM should accelerate from the initial apogee velocity of 5000 m/s up to the orbital insertion velocity of 7560 m/s. The KSRM design variables and the orbital insertion trajectory profile variables were optimized simultaneously, whereas the mass characteristics of the payload deployment module were assigned. A depleted shutdown condition was considered, to avoid the necessity of a thrust termination device, resulting in a reduced total mass of the KSRM. The results show that the proposed optimization approach was able to find the convergence of the optimal solution with highly acceptable value for conceptual design phase.

Multidisciplinary Design Optimization of Small Canister-Launched Space Launch Vehicle Using Genetic Algorithm

A multidisciplinary design optimization approach of a three stage solid propellant canister-launched launch vehicle is considered. A genetic algorithm (GA) optimization method has been used. The optimized launch vehicle (LV) is capable of delivering a microsatellite of 60 kg. to a low earth orbit (LEO) of 600 km. altitude. The LV design variables and the trajectory profile variables were optimized simultaneously, while a depleted shutdown condition was considered for every stage, avoiding the necessity of a thrust termination device, resulting in reduced gross launch mass of the LV. The results show that the proposed optimization approach was able to find the convergence of the optimal solution with highly acceptable value for conceptual design phase.

Geometry of an oblique thrust fault zone in a deepwater fold belt from 3D seismic data

Growth of a 12 km long, deepwater anticline during the late Pliocene–Recent is documented from 3D seismic reflection data across NW Borneo. The fold is part of a train of folds formed along the slope at the distal margin of the Baram Delta Province. Growth of the anticline involved fold lateral propagation and linkage of two thrusts formed in the anticline forelimb as either break thrusts or as imbricates ramping up from a master detachment (at ∼3 km depth). For the southwestern anticline, the northern tip of the NE–SW striking, SE-dipping thrust passes into an E–W striking oblique termination, which lies in the linkage zone between the two anticlines. The thrust termination is characterised by the following changes passing east towards the fault tip: 1) the fault zone dips steeply to the south, then 2) passes to a vertical segment (inferred to have oblique motion), and 3) furthest east the fault dips northwards with an extensional component of displacement. The fault zone terminates in a transtensional graben. This graben does not fit with a simple pull-apart geometry or simple oblique ramp geometry. In the future if the thrust faults propagate together and link this oblique fault zone may develop into an oblique ramp that acts as a transfer zone between the faults. However at present the oblique fault zone appears to be a region of 3D strain, where deformation at the fault tip, and the gravity effects of plunging folds have affected the shallow, weak sediments and given rise to a complex thrust termination at a early stage of thrust and fold development. The oblique structure may have developed in response to strains imposed by the encroachment of the fold and thrust belt on an uplifted basement or volcanic high that forms a pronounced topographic feature across a narrow part of the thrust front, 14 km NW of the most external (oceanward) fold.

Thrust Termination Dynamics of Solid Propellant Rocket Motors

A CTIVE thrust termination or reversing of a separatingmotor are ways to facilitate the staging process and improve the performance of a multistage rocket [1–4]. This is done by opening a secondary nozzle located on the motor head and causing rapid depressurization of the motor chamber. During a rapid change in the chamber pressure the burning rate becomes a nonlinear function of pressure and its time rate of change. The strong dependence of the solid propellant burning rate on the chamber pressure results in a transient nonlinear behavior that may cause premature dynamic extinguishment of the motor. Solid propellants’ transient burning and extinguishment during rapid pressure change have been the subject of a number of studies and several transient burning models have been developed [5–8]. Zeldovich has proposed a comprehensive model based on the unsteady rate of heat transfer to the propellant surface and the time rate of change of the temperature distribution in the solid propellant [6]. This model requires specification of many experimentally determined parameters. The transient burning rate model proposed by Von Elbe and McHale is easy to implement and requires instantaneous pressure and its time rate of change for the regression rate prediction [5]. References [1,2] studying motor transient behavior have used a control volume approach for the gas dynamic simulation of the motor’s internal ballistics. However during the active thrust termination (or reversing) process there is a considerable pressure variation along the motor port and there is a rapid propagation of expansionwaves, through the thrust termination nozzles. These expansion waves play an important role in the transient thrust behavior and a more comprehensive flow model should be used for the internal ballistics’ simulation.

Lateral ramps and thrust terminations: an example from the Moine Thrust Zone, NW Scotland

Detailed remapping within the Assynt Culmination in NW Scotland shows that the Ben More Thrust joins the Glencoul Thrust along a lateral branch line positioned in Loch Glencoul. This branch line marks the northern lateral termination of the Glencoul Thrust. The thrust on the northern shore of Loch Glencoul (‘the famous view’) is thus the Ben More Thrust. The Ben More Thrust Sheet is therefore much larger than previously thought. The lateral terminations of the Ben More Thrust to the north and the south are of two distinct types. This reinterpretation negates the existence of ‘surge’ zones in Assynt.

Evolution of Ordnance Subsystems and Components in Air Force Strategic Missile Systems

Ordnance subsystems and components are critical elements in intercontinental ballistic missile systems. Ord- nance is required for stage ignition, stage separation, thrust vector control system actuation, �uid isolation valve actuation, battery actuation, thrust termination, and release of reentry vehicles. In addition, an ordnance destruct subsystem is mandatory for eachight test. The similarity between missile systems enabled the development and evolution of ordnance designs; for example, the isolation valves, linear-shaped charges for destruct subsystems, linear explosives for stage separation rings, and conned detonating cords for explosive train interconnections were used on allve missile systems developed by the U.S. Air Force since the early 1960s. The approach did not prevent the adoption of new technologies to improve performance. High-temperature resistant hexanitrostilbene explosive was adopted and the through-bulkhead initiator and exploding bridgewire initiator replaced the hot bridgewire-based squibs and detonators. A laser/�ber-optics-based ordnancering system was developed for a mobile missile system. Hermetic seal technologies were adopted for achieving a longer service life for explosive devices. Better methods were adopted for ordnance testing, for example, the thermal transient pulse test and the builtin reectometry. These approaches dramatically improved reliability, safety, weight efciency, service life, and cost effectiveness.

Aspects of the three-dimensional structure of the Alberta Foothills and Front Ranges

Ever more detailed subsurface images of the Alberta Foothills and Front Ranges obtained from improving seismic techniques, coupled with an ever expanding base of information from deep wells and improved structural analysis techniques, have produced an understanding of fold-thrust deformation that is probably applicable to other fold-thrust belts. Comprehensive subsurface data obtained by the petroleum industry are used to outline and analyze the three-dimensional configuration of fold-thrust deformation of Paleozoic carbonate strata. These data indicate that displacement changes smoothly along individual thrusts, but displacement changes along strike may be large, marked by considerable horizontal rotation (20°–30° or more) of hanging-wall stratigraphic cutoffs relative to the footwalls. Stacking of thrusts with varying displacements has produced summed horizontal rotations of hanging-wall cutoffs of as much as 45°–50°. The three-dimensional trajectories of the thrusts through the stratigraphy are smooth for large distances, interrupted by abrupt offsets at lateral and oblique ramps. These are more common than previously realized. The intersections of these ramps with other thrusts produce complex three-dimensional links between thrusts with concomitant abrupt displacement changes. Some simple examples of these linkages are examined with a three-dimensional geometric analysis. The predictions of the analysis are consistent with structural geometries observed in two case studies of subsurface structures. The links at lateral ramps imply simultaneous displacement on parts of the thrusts connected by the ramps. Since the ramps extend downdip 20 km or more, displacement occurred simultaneously on structures occupying relatively interior and exterior positions in the thrust belt. The smooth and long radius-of-curvature folding of many upper detachments indicated by reflection seismic data also is consistent with simultaneous or overlapping periods of motion on groups of thrusts distributed along regional dip. Most major Alberta Foothills thrust sheets terminate southward at lateral ramps at the Paleozoic level. The abrupt southwest-northeast offsets at these features are most clearly apparent on a palinspastic reconstruction. These offsets cause the Paleozoic deformation front to step out east and northeast around the southern and eastern margins of the main arc of the Foothills. In contrast, northward thrust terminations at the Paleozoic level commonly occur at both tip lines and lateral ramps. Subsurface data reveal that there have been some misconceptions regarding large-scale structural relationships. For example, the McConnell and Livingstone sheets are actually portions of the same thrust sheet, as are the Bighorn and Nikanassin sheets. When corrected for these misconceptions, the data from the Alberta Foothills suggest that maximum displacement has a nonlinear relationship to thrust length, although a linear relationship cannot be ruled out.

3D Structural Analysis and Visualization of Oblique-Ramp Accommodation Structures in Thrust Sheets: ABSTRACT

We have observed numerous examples of complex 3D deformation associated with oblique ramps near abrupt thrust terminations. The structures are restricted to hanging-walls of thrust sheets and are associated with zones of rapid loss in stratigraphic separation and/or large displacement gradients along strike. These structures produce a complex but characteristic pattern of folds and/or backthrusts and tear faults that intersect the main thrust at angles up to 90[degrees]. We call these features oblique-ramp accommodation structures. Conventional 2D restoration techniques fail to accurately model oblique-ramp accommodation structures because their transport direction often differs significantly from that of the main thrust. We have analyzed a suite of these structures by constructing 3D computer models using GeoSec 3D. Palinspastic restoration was performed using an equal area, directional flattening algorithm that is based on the azimuth of local structural vergence. The three-dimensionally restored hanging-walls were used to determine the pre-thrust geometry of their corresponding footwalls. In each case the resulting footwall contains an abrupt bend in the strike of the main thrust adjacent to the oblique-ramp accommodation structures in the hanging-wall. Oblique-ramp accommodation structures are the manifestation of local out-of-plane motion in the hanging-wall as it passes over segments of the footwall ramp that more » are oblique to the overall transport direction. They indicate that the termination of the main thrust is probably nearby. They can significantly affect trap geometry by compartmentalizing thrust closures, and can produce local structural highs along main hanging-wall anticlines. « less

Displacement transfer at thrust terminations: the Saltville thrust and Sinking Creek anticline, Virginia, USA : Journal of Structural Geology, 16(6), 1994, pp 781–793

Displacement transfer at thrust terminations: the Saltville thrust and Sinking Creek anticline, Virginia, USA : Journal of Structural Geology, 16(6), 1994, pp 781–793

Displacement transfer at thrust terminations: the Saltville thrust and Sinking Creek anticline, Virginia, U.S.A.

The Saltville thrust terminates in the core of the Sinking Creek anticline. Changes in the amplitude of the anticline may preserve profile shortening as the thrust displacement decreases towards the fault termination. Consequently, thrust displacement would be transferred into the fold. We combine newly published maps and new strain and mesostructural data from the Tuscarora Sandstone to argue that the Sinking Creek anticline did perform this kinematic role. We propose that the anticline developed as a fault-propagation fold that experienced both décollement and anticlinal breakthrough by the Saltville thrust. Thrust displacement was accommodated by the development of the modified fault-propagation fold and by transfer to a roof flat from the décollement breakthrough. New strain and mesostructural data indicate no fixed pin lines in either the hinge or backlimb throughout folding. Consequently, layer slip occurred through the hinge during folding and the forelimb deformed internally during breakthrough. Towards the plungeout of the Sinking Creek anticline, the displacement on the Saltville thrust is transferred to a floor thrust. We apply this interpretation to the termination of the St. Clair thrust, which has a similar surface geometry where the thrust terminates into an anticline. A testable implication of this proposed interpretation for the St. Clair thrust is that the Appalachian Plateau must absorb over 20 km of thrust displacement as horizontal shortening.

Displacement and deformation associated with a lateral thrust termination, southern Golden Gate Range, southern Nevada, U.S.A.

The Golden Gate thrust offers an excellent opportunity to study displacement and deformation at a lateral thrust tip. Slip across this E-vergent thrust is uniformly about 2.4 km for the southern 2 km of exposed strike length and dies out to zero in the northern 5 km. Constant displacement and uniform hangingwall structure along the southern one-third of exposed strike length suggest that along-strike displacement variation and consequent deformation are localized near the lateral tip. Structures located at and north of the lateral tip are consistent with transpression and later uplift as slip accumulated on the thrust. Fold and fault orientations and calcite twinning strain record possible transpression north of the lateral tip. E-W-striking normal faults at the thrust tip record extension that is interpreted to be the result of the uplift and translation of a structurally continuous, rigid block located north of the normal faults. This block is connected to and was uplifted with the crest of the hangingwall anticline, and was separated by the normal faults from thrust-related folding to the south. The main hangingwall structure is an anticline that in southern exposures trends N-S parallel to the thrust but bends westward and opens into a box fold to the north. The hangingwall anticline superficially resembles a classic fault-propagation fold formed by a migrating ductile bead. However, we are forced to reject the ductile bead hypothesis for the fold because: (1) the geometry of the hangingwall anticline far from the thrust tip cannot have evolved from the geometry at the thrust tip; and (2) twinned calcite strain data from along the thrust suggest that strain was homogeneous and coaxial rather than inhomogeneous and progressively non-coaxial as predicted for a migrating ductile bead. The three-dimensional structural and kinematic relations at the lateral tip of the Golden Gate thrust appear to be the result of deformation around a pinned tip, although the reason that the tip was pinned at its present location is unclear. We interpret the thrust to have propagated relatively quickly to its ultimate extent with little initial displacement, indicating that it was easier to fault the rocks than to fold them.