Abstract: A system may include a tether, a slip ring, a tether gimbal assembly, a drive mechanism, a control system. The tether may include a distal tether end coupled to an aerial vehicle, a proximate tether end, and at least one insulated electrical conductor coupled to the aerial vehicle. The slip ring may include a fixed portion and a rotatable portion, where the rotatable portion is coupled to the tether. The tether gimbal assembly may be rotatable about at least one axis and is coupled to the fixed portion of the slip ring. The drive mechanism may be coupled to the slip ring and configured to rotate the rotatable portion of the slip ring. And the control system may be configured to operate the drive mechanism to control twist in the tether.

Abstract: A system for adjusting a load on a tethered aircraft is disclosed. The aircraft is tethered to a payload. The system determines a new position for the tethered aircraft in the event that due to environmental effects, e.g., the aircraft is flying upwind or downwind, the load experienced by the tethered aircraft is not optimal.

Abstract: A flight configuration is disclosed. The flight configuration includes a lift configuration in which a lift aircraft lifts a powered payload via a tether. The flight configuration comprises a series of steps for transitioning from the lift configuration to a forward flight configuration. In the forward flight configuration, the lift aircraft and the powered payload are in horizontal alignment.

Abstract: A propeller includes a blade free to rotate. A first stop is positioned to mechanically engage one or both of a first portion of the blade and a first structure coupled to the blade when the blade is in a first position at a first end of the rotational range of motion. A second stop is positioned to mechanically engage one or both of a second portion of the blade and a second structure coupled to the blade when the blade is in a second position at a second end of the defined rotational range. The blade rotates to the first position against the first stop when the propeller is rotated in a first direction and to the second position against the second stop when the propeller is rotated in a second direction.

Abstract: A propeller includes a blade free to rotate about a longitudinal axis of the blade. The propeller also includes a mechanical stop positioned to engage mechanically a first portion of the blade and/or a first structure coupled mechanically to the blade when the blade is in a first position. The propeller also includes a magnetic stop positioned to engage magnetically a second portion of the blade and/or a second structure coupled mechanically to the blade when the blade is in a second position. The blade rotates to the first position against the mechanical stop when the propeller is rotated at a first rotational speed and the blade rotates to the second position against the magnetic stop when the propeller is rotated at a second rotational speed in a same direction as when the blade is in the first position.

Abstract: A system to maintain a phase difference is disclosed. Two or more aircraft fly in a continuous periodic trajectory. The system maintains a phase difference between the two or more aircraft. Telemetry information for a reference aircraft moving in a first periodic trajectory is received. A phase difference between a primary aircraft and the reference aircraft with respect to the first periodic trajectory is determined. A variance in the phase difference between the primary aircraft and the reference aircraft from the target phase difference is determined. A new trajectory for the primary aircraft that decreases the variance in the phase difference with respect to the new periodic trajectory is determined, and the primary aircraft is maneuvered to follow the new trajectory.

Abstract: An apparatus is provided that includes a top clamshell having a first contoured surface that is configured to capture at least a portion of a top surface of a wing of an airborne wind turbine (AWT). The apparatus further includes a bottom clamshell having a second contoured surface that is configured to capture at least a portion of a bottom surface of the wing. The first contoured surface and the second contoured surface are configured to restrain the wing between the top clamshell and the bottom clamshell. The top clamshell is configured to be coupled to the fuselage attachment via a fastener at an aft end of the attachment apparatus.

Abstract: Apparatus are disclosed that are configured to passively rotate a propeller blade from a first pitch angle to a second pitch angle. An example apparatus involves: (a) a rotor hub, (b) at least one dual-pitch support coupled to the rotor hub, wherein the dual-pitch support has a first surface, a second surface and a cavity defined there between, and (c) at least one propeller blade rotatably coupled to the rotor hub such that a blade root is disposed within the dual-pitch support's cavity, where the blade root's front face is positioned against the dual-pitch support's first surface in a first position and the blade root's back face is positioned against the dual-pitch support's second surface in a second position, and the propeller blade is oriented at a first pitch angle in the first position and is oriented at a second pitch angle in the second position.

Abstract: An automated aircraft recovery system is disclosed. In various embodiments, the system includes an interface configured to receive sensor data; and a control mechanism configured to: perform automatically a recovery action that is determined based at least in part on the sensor data. In various embodiments, the control mechanism may determine an expected state of an aircraft, determine whether a state of the aircraft matches the expected state, and in the event the state of the aircraft does not match the expected state, perform the recovery action.

Abstract: Methods and systems described herein relate to power generation control for an aerial vehicle. An example method may involve determining an asynchronous flight pattern for two or more aerial vehicles, where the asynchronous flight pattern includes a respective flight path for each of the two or more aerial vehicles; and operating each of the aerial vehicles in a crosswind flight substantially along its respective flight path, where each aerial vehicle generates electrical power over time in a periodic profile, and where the power profile of each aerial vehicle is out of phase with respect to the power profile generated by each of the other aerial vehicles.

Abstract: A multi-modal aircraft recovery system is disclosed. In various embodiments, the system includes a first aircraft recovery parachute having a first set of physical attributes optimized for a first set of conditions and a second aircraft recovery parachute having a second set of physical attributes optimized for a second set of conditions different from the first.

Abstract: Techniques to deploy a parachute are disclosed. In various embodiments, a first projectile is configured to be propelled in a first direction, causing the parachute to be deployed. A second projectile configured to be propelled in a second direction is coupled to a line tethered to the parachute in such a way that a force in a direction opposite the first direction is applied to the line of the parachute when the second projectile is propelled in the second direction.

Abstract: In an example embodiment, a system includes a plurality of drive units coupled to a plurality of propellers. Each drive unit includes a single motor/generator and a single motor controller, and the plurality of drive units includes a first drive-unit pair and a second drive-unit pair. The system also includes a high-voltage bus connecting the motor controllers in the first drive-unit pair to a tether, a low-voltage bus connecting the motor controllers in the second drive-unit pair to the tether, and an intermediate-voltage bus connecting the motor controllers of the first drive-unit pair in series with the motor controllers of the second drive-unit pair. The motor controllers in the first drive-unit pair are connected in parallel via the high-voltage bus and the intermediate-voltage bus, and the motor controllers in the second drive-unit pair are connected in parallel via the intermediate-voltage bus and the low-voltage bus.

Abstract: In order to maximize cooling while minimizing drag in aerial vehicles of airborne wind turbines, it may be preferable to dissipate the cooling energy of the motors via a radiator in a region with advantageous airflow parameters. Aerial vehicle rotors operating in thrust mode may produce relatively more airflow velocity in certain regions further away from the center of the rotor blades, both radially and longitudinally. Placing a radiator in a rotor-supporting pylon and offset from the center of the rotor blades and aft of the rotor blades may allow for greater cooling while the aerial vehicle while in thrust mode.

Abstract: While an aircraft is mid-flight, a braking start point associated with a stoppable rotor is calculated where the stoppable rotor includes a first and second blade and the stoppable rotor is configured to rotate about a substantially vertical axis. A process to stop the stoppable rotor is started, while the aircraft is mid-flight, when the stoppable rotor reaches the braking start point, where the stoppable rotor is stopped with the first blade pointing forward and the second blade pointing backward.

Abstract: A stoppable rotor, which includes a first and second blade and rotates about a substantially vertical axis, is stopped with the first blade pointing forward and the second blade pointing backward while the aircraft is mid-flight. Anti-torque is provided using a set of one or more combination rotors in a first mode of operation in order to counter torque produced by the stoppable rotor when the stoppable rotor is rotating where the set of combination rotors rotate about a substantially longitudinal axis. Forward thrust is provided using the set of combination rotors in a second mode of operation when the stoppable rotor is not rotating.

Abstract: Systems and methods are provided for a wiring harness for an aerial vehicle. A wing of the aerial vehicle comprises a pocket for insertion of the wiring harness. The wiring harness provides wiring and associated connections capable to attach to and power various components.

Abstract: Apparatus are disclosed that are configured to passively rotate a propeller blade from a first pitch angle to a second pitch angle. An example apparatus involves: (a) a rotor hub, (b) at least one dual-pitch support coupled to the rotor hub, wherein the dual-pitch support has a first surface, a second surface and a cavity defined there between, and (c) at least one propeller blade rotatably coupled to the rotor hub such that a blade root is disposed within the dual-pitch support's cavity, where the blade root's front face is positioned against the dual-pitch support's first surface in a first position and the blade root's back face is positioned against the dual-pitch support's second surface in a second position, and the propeller blade is oriented at a first pitch angle in the first position and is oriented at a second pitch angle in the second position.

Abstract: In response to a torque that is applied to a clutch module not exceeding a torque threshold, the clutch module is locked where a blade is configured to be at a first pitch angle in response to the clutch module being locked. In response to the torque that is applied to the clutch module exceeding the torque threshold, the clutch module is released where the blade has a range of motion which extends from the first pitch angle to a second pitch angle in response to the clutch module being released.

Abstract: A vehicle-based airborne wind turbine system having an aerial wing, a plurality of rotors each having a plurality of rotatable blades positioned on the aerial wing, an electrically conductive tether secured to the aerial wing and secured to a ground station positioned on a vehicle, wherein the aerial wing is adapted to receive electrical power from the vehicle that is delivered to the aerial wing through the electrically conductive tether; wherein the aerial wing is adapted to operate in a flying mode to harness wind energy to provide a first pulling force through the tether to pull the vehicle; and wherein the aerial wing is also adapted to operate in a powered flying mode wherein the rotors may be powered so that the turbine blades serve as thrust-generating propellers to provide a second pulling force through the tether to pull the vehicle.