Fin Movements Research Articles

Experimental investigation of the relationship between caudal fin movement and propulsion by a tuna-type swimming robot

Experimental investigation of the relationship between caudal fin movement and propulsion by a tuna-type swimming robot

Constructing a control system using a time–state control form for a fish-type balloon robot

A fish-type balloon robot (FBR) is a biomimetic robot that introduces twisting and pectoral fin motions into an airship robot. The FBR can move back and forth, right and left, and up and down using the twisting and pectoral fin motions. The FBR can propel itself without using a propeller; therefore, it does not injure people during accidental collisions. From this perspective, the FBR can be considered very safe. Therefore, the FBR can be used as a monitoring satellite and an advertising platform. In this paper, we construct an automatic control system for such practical FBR applications. The FBR cannot skid sideways; therefore, it can be considered a robot with nonholonomic constrains, based on the Brockett’s study. In this research, we apply control using a time–state control form. The outline of this control method is as follows. First, we converted the FBR motion model into a time–state control form using a time state and a state control unit. Second, we constructed a feedback control system that stabilized the state control unit. Third, we measured the propulsion characteristics of the FBR using the pectoral fin motion, which is necessary for controlling the FBR’s motion using the time–state control form and for analyzing the measurement results. In addition, we varied the pectoral fin motion to simulate how the FBR’s propulsion and turning angular velocities become similar. Finally, based on the measurement results, we constructed and executed a simulated control system.

Breathing with fins: do the pectoral fins of larval fishes play a respiratory role?

Convective water flow across respiratory epithelia in water-breathing organisms maintains transcutaneous oxygen (O2) partial pressure (Po2) gradients that drive O2 uptake. Following hatch, larval fishes lack a developed gill and the skin is the dominant site of gas transfer, yet few studies have addressed the contribution of convective water flow to cutaneous O2 uptake in larvae. We hypothesized that the pectoral fins, which can generate water flow across the skin in larvae, promote transcutaneous O2 transfer and thus aid in O2 uptake. In zebrafish (Danio rerio), the frequency of pectoral fin movements increased in response to hypoxia at 4 days postfertilization (dpf), but the response was blunted by 15 dpf, when the gills become the dominant site of O2 uptake, and was absent by 21 dpf. In rainbow trout (Oncorhynchus mykiss), Po2 measured at the skin surface of ventilating larvae was lower when the pectoral fins had been surgically removed, directly demonstrating that fins contribute to convective flow that dissipates cutaneous Po2 boundary layers. Lack of pectoral fins compromised whole animal O2 consumption in trout during hypoxia, but this effect was absent in zebrafish. Overall, our findings support a respiratory role of the pectoral fins in rainbow trout, but their involvement in zebrafish remains equivocal.

A primal role for the vestibular sense in the development of coordinated locomotion.

Mature locomotion requires that animal nervous systems coordinate distinct groups of muscles. The pressures that guide the development of coordination are not well understood. To understand how and why coordination might emerge, we measured the kinematics of spontaneous vertical locomotion across early development in zebrafish (Danio rerio) . We found that zebrafish used their pectoral fins and bodies synergistically during upwards swims. As larvae developed, they changed the way they coordinated fin and body movements, allowing them to climb with increasingly stable postures. This fin-body synergy was absent in vestibular mutants, suggesting sensed imbalance promotes coordinated movements. Similarly, synergies were systematically altered following cerebellar lesions, identifying a neural substrate regulating fin-body coordination. Together these findings link the vestibular sense to the maturation of coordinated locomotion. Developing zebrafish improve postural stability by changing fin-body coordination. We therefore propose that the development of coordinated locomotion is regulated by vestibular sensation.

Simulation Analysis of Bionic Robot Fish Based on MFC Materials

With the development of marine resources, research on underwater robots has received unprecedented attention. The discovery and application of new smart materials provide new ideas for the research of underwater robots, which can overcome the issues of traditional underwater robots and optimize their design. A macro fiber composite (MFC) is a new type of piezoelectric fiber composite that combines actuators and sensors. The material has excellent deflection, good flexibility, and a high electromechanical coupling coefficient. Bionic mechatronics design is an effective way to innovate mechatronics in the future and can significantly improve mechatronics system performance. As an important issue for the design of bionic mechatronics, it is necessary to make robots as soft as natural organisms to achieve similar biological movement with both higher efficiency and performance. Compared with traditional rigid robots, the design and control of a soft robotic fish are difficult because the coupling between the flexible structure and the surrounding environment should be considered, which is difficult to solve due to the large deformation and coupling dynamics. In this paper, an MFC smart material is applied as an actuator in the design of bionic robotic fish. Combined with the piezoelectric constitutive and elastic constitutive equations of the MFC material, the voltage-drive signal is converted to a mechanical load applied to the MFC actuator, which makes the MFC material deform and drives the movement of the robotic fish. The characteristics of caudal fin motion during the swimming process of the bionic robotic fish were analyzed by an acoustic-solid coupling analysis method. The motion control analysis of the bionic robotic fish was carried out by changing the applied driving signal. Through numerical analysis, a new type of soft robotic fish was designed, and the feasibility of using an MFC smart material for underwater bionic robotic fish actuators was verified. The new soft robotic fish was successfully developed to achieve high performance.

Efficient thrust generation in robotic fish caudal fins using policy search

Thrust generation is a crucial aspect of fish locomotion that depends on a variety of morphological and kinematic parameters. In this work, the kinematics of caudal fin motion of a robotic fish are optimised experimentally. The robotic fish actuates its caudal fin with flapping and rotation motion, and also measures the fin hydrodynamic force and torque. Total nine designs of the caudal fins are investigated, with three different shapes (or inclination angles) and three stiffness. The optimisation is based on a policy search (PS) algorithm, which is used to maximise the thrust-generation efficiency of the caudal fins. The authors first parametrise fin spanwise-rotation as a sinusoidal function using rotation amplitude and phase delay and test whether it is beneficial to thrust-generation efficiency. The result shows that the rotation does not contribute to the efficiency, as the efficiency is maximised at zero amplitude. Next, the authors optimise flapping amplitude and trajectory profile without fin rotation. Results show that smaller flapping amplitude results in higher efficiency and linear flapping trajectories are preferred over sinusoidal ones. Fins that have the highest flexibility are more efficient in thrust generation although they generate less thrust, while an inclination angle of 30° yields the most efficient fin shape.

Flow interactions between uncoordinated flapping swimmers give rise to group cohesion

Many species of fish and birds travel in groups, yet the role of fluid-mediated interactions in schools and flocks is not fully understood. Previous fluid-dynamical models of these collective behaviors assume that all individuals flap identically, whereas animal groups involve variations across members as well as active modifications of wing or fin motions. To study the roles of flapping kinematics and flow interactions, we design a minimal robotic "school" of two hydrofoils swimming in tandem. The flapping kinematics of each foil are independently prescribed and systematically varied, while the forward swimming motions are free and result from the fluid forces. Surprisingly, a pair of uncoordinated foils with dissimilar kinematics can swim together cohesively-without separating or colliding-due to the interaction of the follower with the wake left by the leader. For equal flapping frequencies, the follower experiences stable positions in the leader's wake, with locations that can be controlled by flapping amplitude and phase. Further, a follower with lower flapping speed can defy expectation and keep up with the leader, whereas a faster-flapping follower can be buffered from collision and oscillate in the leader's wake. We formulate a reduced-order model which produces remarkable agreement with all experimentally observed modes by relating the follower's thrust to its flapping speed relative to the wake flow. These results show how flapping kinematics can be used to control locomotion within wakes, and that flow interactions provide a mechanism which promotes group cohesion.

Body and Pectoral Fin Kinematics During Routine Yaw Turning in Bonnethead Sharks (Sphyrna tiburo).

SynopsisManeuvering is a crucial locomotor strategy among aquatic vertebrates, common in routine swimming, feeding, and escape responses. Combinations of whole body and fin movements generate an imbalance of forces resulting in deviation from an initial path. Sharks have elongate bodies that bend substantially and, in combination with pectoral fin rotation, play a role in yaw (horizontal) turning, but previous studies focus primarily on maximal turning performance rather than routine maneuvers. Routine maneuvering is largely understudied in fish swimming, despite observations that moderate maneuvering is much more common than the extreme behaviors commonly described in the literature. In this study, we target routine maneuvering in the bonnethead shark, Sphyrna tiburo. We use video reconstruction of moving morphology to describe three-dimensional pectoral fin rotation about three axes to compare to those previously described on yaw turning by the Pacific spiny dogfish. We quantify kinematic variables to understand the impacts of body and fin movements on routine turning performance. We also describe the anatomy of bonnethead pectoral fins and use muscle stimulation to confirm functional hypotheses about their role in actuating the fin. The turning performance metrics we describe for bonnethead sharks are comparable to other routine maneuvers described for the Pacific spiny dogfish and manta rays. These turns were substantially less agile and maneuverable than previously documented for other sharks, which we hypothesize results from the comparison of routine turning to maneuvering under stimulated conditions. We suggest that these results highlight the importance of considering routine maneuvering in future studies. Cinemática del Cuerpo y de las Aletas Pectorales Durante el giro en el eje Vertical en la Cabeza del Tiburón Pala (Sphyrna tiburo) (Body and Pectoral Fin Kinematics During Routine Yaw Turning in Bonnethead Sharks [Sphyrna tiburo])

Pectoral fin kinematics and motor patterns are shaped by fin ray mechanosensation during steady swimming in Scarus quoyi.

For many fish species, rhythmic movement of the pectoral fins, or forelimbs, drives locomotion. In terrestrial vertebrates, normal limb-based rhythmic gaits require ongoing modulation with limb mechanosensors. Given the complexity of the fluid environment and dexterity of fish swimming through it, we hypothesize that mechanosensory modulation is also critical to normal fin-based swimming. Here, we examined the role of sensory feedback from the pectoral fin rays and membrane on the neuromuscular control and kinematics of pectoral fin-based locomotion. Pectoral fin kinematics and electromyograms of the six major fin muscles of the parrotfish, Scarus quoyi, a high-performance pectoral fin swimmer, were recorded during steady swimming before and after bilateral transection of the sensory nerves extending into the rays and surrounding membrane. Alternating activity of antagonistic muscles was observed and drove the fin in a figure-of-eight fin stroke trajectory before and after nerve transection. After bilateral transections, pectoral fin rhythmicity remained the same or increased. Differences in fin kinematics with the loss of sensory feedback also included fin kinematics with a significantly more inclined stroke plane angle, an increased angular velocity and fin beat frequency, and a transition to the body-caudal fin gait at lower speeds. After transection, muscles were active over a larger proportion of the fin stroke, with overlapping activation of antagonistic muscles rarely observed in the trials of intact fish. The increased overlap of antagonistic muscle activity might stiffen the fin system in order to enhance control and stability in the absence of sensory feedback from the fin rays. These results indicate that fin ray sensation is not necessary to generate the underlying rhythm of fin movement, but contributes to the specification of pectoral fin motor pattern and movement during rhythmic swimming.

Swimming Turned on Its Head: Stability and Maneuverability of the Shrimpfish (Aeoliscus punctulatus).

SynopsisThe typical orientation of a neutrally buoyant fish is with the venter down and the head pointed anteriorly with a horizontally oriented body. However, various advanced teleosts will reorient the body vertically for feeding, concealment, or prehension. The shrimpfish (Aeoliscus punctulatus) maintains a vertical orientation with the head pointed downward. This posture is maintained by use of the beating fins as the position of the center of buoyancy nearly corresponds to the center of mass. The shrimpfish swims with dorsum of the body moving anteriorly. The cross-sections of the body have a fusiform design with a rounded leading edge at the dorsum and tapering trailing edge at the venter. The median fins (dorsal, caudal, anal) are positioned along the venter of the body and are beat or used as a passive rudder to effect movement of the body in concert with active movements of pectoral fins. Burst swimming and turning maneuvers by yawing were recorded at 500 frames/s. The maximum burst speed was 2.3 body lengths/s, but when measured with respect to the body orientation, the maximum speed was 14.1 body depths/s. The maximum turning rate by yawing about the longitudinal axis was 957.5 degrees/s. Such swimming performance is in line with fishes with a typical orientation. Modification of the design of the body and position of the fins allows the shrimpfish to effectively swim in the head-down orientation.

Emersion and Terrestrial Locomotion of the Northern Snakehead (Channa argus) on Multiple Substrates

SynopsisMost fishes known for terrestrial locomotion are small and/or elongate. Northern snakeheads (Channa argus) are large, air-breathing piscivores anecdotally known for terrestrial behaviors. Our goals were to determine their environmental motivations for emersion, describe their terrestrial kinematics for fish 3.0–70.0 cm and compare kinematics among four substrates. For emersion experiments, C. argus was individually placed into aquatic containers with ramps extending through the surface of the water, and exposed to 15 ecologically-relevant environmental conditions. For kinematic experiments, fish were filmed moving on moist bench liner, grass, artificial turf, and a flat or tilted rubber boat deck. Videos were digitized for analysis in MATLAB and electromyography was used to measure muscular activity. Only the low pH (4.8), high salinity (30 ppt), and high dCO2 (10% seltzer solution) treatments elicited emersion responses. While extreme, these conditions do occur in some of their native Asian swamps. Northern snakeheads >4.5 cm used a unique form of axial-appendage-based terrestrial locomotion involving cyclic oscillations of the axial body, paired with near-simultaneous movements of both pectoral fins. Individuals ≤3.5 cm used tail-flip jumps to travel on land. Northern snakeheads also moved more quickly on complex, three-dimensional substrates (e.g., grass) than on smooth substrates (e.g., bench liner), and when moving downslope. Release of snakeheads onto land by humans or accidentally by predators may be more common than voluntary emersion, but because northern snakeheads can respire air, it may be necessary to factor in the ability to spread overland into the management of this invasive species.

Implementation of a robust motion control scheme for an Ostraciiform inspired underwater robot with caudal and pectoral fins

The underwater robotic vehicle presented here is inspired by an Ostraciiform form of swimming with three oscillatory fins to propel itself and control its orientation. A mathematical model is made to simulate the motion of the vehicle based on the fin oscillations to aid in the real-time vehicle control. The model predicts the forces produced by the oscillating rigid fins in the water. A new motion control approach for an underwater robot is proposed and investigated. In this paper, the oscillating fin arrangement is under-actuated and carries out four degrees of freedom (DOF) motion with three fins. The threes fins include: once caudal fin and two pectoral fins. The dynamic model developed for the robot has a highly nonlinear thrust vector map because of the thrust generation from these oscillation angles. Nonlinear control methods such as Backstepping control is applied to this robot model due to the continuous oscillatory motion of fins for achieving different DOF. Contrary to the feedback linearization technique which cancels potentially useful nonlinearities, this control scheme avoids the cancellation; resulting in a less complicated controller. Lyapunov stability theory was used to prove the system stability. RMS values of the error were used for tuning the controller gains constants.

Indirect pathway to pectoral fin motor neurons from nucleus ruber in the Nile tilapia Oreochromis niloticus.

Supraspinal motor control systems of pectoral fins remain unclear in teleosts. Nucleus ruber of Goldstein (1905; NRg), which has been identified as the probable homologue of nucleus ruber of tetrapods, is a candidate structure serving for such functions. In the present study, we investigated possible involvement of the NRg in the control of pectoral fin movement by tract-tracing experiments in the Nile tilapia Oreochromis niloticus. Tracer injections into the NRg revealed the fiber course of rubrospinal tract. Rubrospinal fibers crossed the midline at the level of midbrain, descended through the tegmentum, and terminated in a region ventrally adjacent to the dorsal horn at the spinomedullary junction, without reaching the ventral horn where pectoral fin motor neurons are present. Tracer injection experiments into the dorsal horn region resulted in labeled terminals in proximities of presumed pectoral fin motor neurons in the ventral horn. Tracer injection experiments into the ventral horn resulted in retrogradely labeled neurons ventrally adjacent to the dorsal horn, where labeled terminals were detected following rubral injections. These anatomical analyses suggest that the NRg of actinopterygians is involved in the control of pectoral fin motor neurons through an indirect pathway via interneurons in the dorsal horn.

Determination of lethal dose of Aeromonas hydrophila Ah17 strain in snake head fish Channa striata

Aeromonas hydrophila is a major bacterial fish pathogen which causes economic losses in the aquaculture. The study determined the Letha Dose (LD50-96h) of A. hydrophila Ah17 strain (isolated from EUS infected Channa striata) in C. striata. C. striata were challenged with three different concentration of A. hydrophila Ah17 strain 1.0 × 107, 1.0 × 108, 1.0 × 109 CFU/mL. The LD50-96h values were found to be 4.1 × 108 CFU/mL. Percentage of mortality was observed as 10%, 40% and 70% in 1.0 × 107, 1.0 × 108 and 1.0 × 109 CFU/mL respectively in challenged fish. Microbial load was calculated on muscle, kidney, liver and spleen with highest load was observed in muscle and lowest in kidney. Level of liver enzymes such as Aspartate aminotransferase (AST), Alanine Aminotransferase (ALT), and Alkaline Phosphatase (ALP) were increased compared to control fish. Level of mRNA expression of antioxidant genes such as Catalase (cat), Manganese Superoxide Dismutase (MnSOD), Glutathione Peroxidase (GPx) were high in liver tissue of all treated groups than control. Clinical signs were observed after intraperitoneal treatment of Ah17 in C. striata. Clinical signs such as lesions on the site of injection, imbalanced state, changes in the movement of pectoral fins, depigmentation on the tail of caudal fin and irregular lesions on the muscle region were observed. Thus the study concluded that, the LD50-96h value of A. hydrophila Ah17 strain was 4.1 × 108 CFU/mL and exhibited potential pathogenic effect upon experimental infection in snakehead murrel C. striata.

Simulation of the entanglement of a North Atlantic right whale (Eubalaena glacialis) with fixed fishing gear

AbstractPopulation estimates of the critically endangered North Atlantic right whale (Eubalaena glacialis) put the number of individuals at 458 with the actual number likely being lower due to a recent unusual mortality event. Entanglement with fixed fishing gear is the most significant cause of mortality of North Atlantic right whales. There remains little documentation of how North Atlantic right whales become enwrapped during an encounter with fixed fishing gear. In order to gain a better understanding of how entanglements might occur, an interactive simulator was developed that allows the user to swim a virtual whale model using a standard game controller through a gear field in an attempt to re‐create an entanglement. The morphologically accurate right whale model produces realistic swimming motions and is capable of pectoral fin motions in response to user input. Using the simulator, gear entanglements involving the pectoral flippers including ropes wrapping around the body and entanglements involving the tailstock were re‐created. Entanglements involving the pectoral flippers with body wraps were more easily generated than entanglements involving the tailstock only. The simulator should aid scientists, fisheries experts, fishing gear designers, and bycatch reduction scientists in understanding entanglement dynamics and testing potential new gear configurations.

A walking behavior generates functional overland movements in the tidepool sculpin, Oligocottus maculosus

Tidepool sculpins (Oligocottus maculosus) have been observed moving overland in the rocky intertidal, and we documented the terrestrial walking behavior that they use to accomplish this. We quantified the terrestrial movements of O. maculosus and compared them to (1) their aquatic locomotion, (2) terrestrial locomotion of closely-related subtidal species (Leptocottus armatus and Icelinus borealis), and (3) terrestrial movements of walking catfishes (Clarias spp.). We recorded sculpin movements (210 fps) on a terrestrial platform and in a water tank and tracked body landmarks for kinematic analysis. The axial-appendage-based terrestrial locomotion of O. maculosus is driven by cyclic lateral oscillations of the tail, synchronized with alternating rotations about the base of the pectoral fins, a behavior that appears similar to a military “army crawl.” The pectoral fins do not provide propulsion, but act as stable points for the body to rotate around. In contrast, individuals of O. maculosus use primarily axial undulation during slow-speed swimming. The army crawl is a more effective terrestrial behavior (greater distance ratio) than the movements produced by L. armatus and I. borealis, which use rapid, cyclic oscillations of the tail, without coordinated pectoral fin movements. Relative to Clarias spp., O. maculosus rotated the body about the base of the pectoral fin, rather than the tip of the fin, which may cause O. maculosus to have a lower distance ratio. Since O. maculosus lack major morphological adaptations for terrestrial locomotion, instead relying on behavioral adaptations, we propose behavioral adaptations may evolutionarily predate morphological adaptations for terrestrial locomotion in vertebrates.

Living on the edge: thermoregulatory behaviour of South American sea lions, Otaria flavescens, at the northern limit of their Atlantic distribution

Terrestrial reproduction presents a thermoregulatory challenge for marine mammals, especially in a context of global warming. Pinnipeds, especially otariids, differ from other marine mammals in that most reproductive processes occur on land. Rocky rookeries rarely provide thermoregulatory resources (shade, pools and wet sand), so pinnipeds reduce thermal stress through thermoregulatory behaviour such as flipper exposure, flipper movement and maintenance of individual distance. Our objective was to analyse climate correlates of thermoregulatory behaviour of Southern sea lions Otaria flavescens in a colony located at the warmest end of its northern distribution on the Atlantic coast of South America. We conducted summer behavioural observations of juveniles/sub-adult (less than 150 kg) and adult (300 kg) males in the Cabo Polonio rookery, Uruguay. Solar radiation and humidity were positively correlated with thermoregulatory behaviour of sea lions, while ambient temperature had a marginal effect and wind speed had no significant effect. There were no statistically significant differences between age classes in thermoregulation activity. These and previous results on thermoregulatory behaviour of pinnipeds open the possibility that pinnipeds can be limited in abundance or distribution if climate change alters solar radiation in terrestrial rookeries during the breeding season.

Development of Efficiency Enhanced Scotch Yoke Mechanism for Robotic Fish

A Scotch yoke mechanism can provide high thrust by generating high frequency flapping motion in a propulsion system of robotic fish. However, higher frequency makes higher drag force, and if the motor torque is insufficient compared to the drag force, this causes a lagging phenomenon due to the lack of torque, which causes a problem of lowering the thrust. In this paper, we propose an efficiency enhanced scotch yoke mechanism through output torque re-distribution. We focus on the fact that the required motor torque of the Scotch yoke mechanism is not constant in the fin propulsion system; thus, it is not necessary to raise the torque in the entire domain. By transferring the extra torque in a certain section to the torque-insufficient section, the frequency and thrust can be increased without increasing the motor size and energy consumption. We present a dynamic model and a design method of the proposed concept, and also validate the performance enhancement by comparing the thrust, frequency, and the period of the tail fin movement of conventional and enhanced system while the equal input current is supplied.

Development and experimental verification of a 5 kW small wind turbine aeroelastic model

Aeroelastic modelling is regularly used in the design and analysis of commercial scale wind turbines, but has seen comparatively little use in the development of small wind turbines. Fewer studies still have considered experimental validation of model performance with field measurements. This study details the development of an aeroelastic model of a 5 kW horizontal-axis Aerogenesis turbine within FAST. The model includes rotor aerodynamics, blade and tower structural freedom, free-yaw tail fin dynamics, and a self-excited induction generator incorporating maximum power point tracking variable speed control. This model was compared to measured operating data to assess aerodynamic and structural performance. Blade loadings and deflections were simulated within 8% and 10% respectively at design conditions in the azimuthal domain. Simulated rotor speed control and tail fin motions were bounded by measured field data. The simulated control system model was found to act aggressively, with a mean over-prediction in tip speed ratio of 11%. Areas for future model improvement are discussed in this paper. The resulting aeroelastic model and methodologies presented here are expected to further the use of aeroelastic modelling in the small wind turbine field. Particular applications may include the verification of performance and design loads specified in IEC 61400.2.

Kinematic study on a self-propelled bionic underwater robot with undulation and jet propulsion modes

SUMMARYThis paper proposed a novel type of bionic underwater robot (BUR). The undulation and jet propulsion modes on the self-propelled BUR were combined, and the kinematic characteristics of the two propulsion modes were thoroughly compared. First, the prototype and swimming strategy of the BUR were presented, and a dynamic model of the BUR was established based on several assumptions. Then, a central pattern generator (CPG) model allowing free adjustment of frequency and amplitude was employed to achieve the undulation propulsion of carangiform fish and the jet propulsion of jellyfish. Also, the kinematic characteristics of the two propulsion modes were investigated through experiments under different caudal fin actuation parameters. The experimental results indicate that the developed prototype can realize the undulation and jet propulsion by the means of the coordinated movement of the multi-caudal fins. By adjusting the CPG parameters, the BUR can switch the propulsion mode smoothly. Furthermore, the propulsion velocity of the BUR initially increased rapidly with the frequency and then slowed down when the frequency was greater than 0.8 Hz in both propulsion modes. The undulation propulsion velocity increased with the amplitude in the measurement ranges, however, the jet propulsion velocity initially increased quickly with the amplitude and then kept constant and even decreased when the amplitude was greater than 11 cm. Under the same caudal fin actuation parameters, the average velocity in undulation propulsion mode was higher than that in jet propulsion mode.