Abstract: An aerial vehicle configured with air intake in an otherwise higher drag location. In some aspects, the aerial vehicle is a vertical take-off and landing aircraft. The aircraft may intake the air to provide air to a hydrogen fuel cell system within the aircraft. The aircraft may have electric motor driven rotor assemblies which provide thrust for both vertical take-off and landing and forward flight operations. The electric motor driven rotor assemblies may be powered by electric power from the fuel cell system. The air intake may be on the forward portion of a nacelle placed in what would be a high drag location, such as at the junction of the wings and the fuselage, or the junction of the vertical stabilizers and the fuselage, for example.

Abstract: An oblique flying wing aircraft with internal ducting and airflow. The aircraft may have propulsion units within the wing body. The propulsion units may be off-axis internal to the wing to utilize locations with larger internal space available. In some aspects, the multi-segment oblique flying wing aircraft may have three distinct segments including two outer wing segments and a central wing segment. The central segment may be thicker in the vertical direction and adapted to hold pilots and passengers. The outer wing segments may be substantially thinner and may taper as they progress outboard from the wing center. The multi-segment oblique flying wing aircraft be adapted for rotating into a high-speed flight configuration, or may be adapted for take-off and cruise at a constant angle.

Abstract: A high efficiency hydrogen fuel system for an aircraft at high altitude which utilizes compressors to compress air to a sufficiently high pressure for the fuel cell. Liquid hydrogen is compressed and then utilized in heat exchangers to cool the compressed air, maintaining the air at a temperature low enough for the fuel cell. The hydrogen is also used to cool the fuel cell as it is also depressurized prior to its entry in the fuel cell cycle. A water condensation system allows for water removal from the airstream to reduce impacts to the atmosphere. The hydrogen fuel system may be used with VTOL aircraft, which may allow them to fly at higher elevations. The hydrogen fuel system may be used with other subsonic and supersonic aircraft, such as with asymmetric wing aircraft.

Abstract: An aircraft propulsion system with an internally cooled electric motor adapted for use in an aerial vehicle. The motor may have its stator towards the center and have an external rotor. The rotor structure may be air cooled and may be a complex structure with an internal lattice adapted for airflow. The stator structure may be liquid cooled and may be a complex structure with an internal lattice adapted for liquid to flow through. A fluid pump may pump a liquid coolant through non-rotating portions of the motor stator and then through heat exchangers cooled in part by air which has flowed through the rotating portions of the motor rotor. The drag reduction portion and the cooled electric motor portion may share the same inlet.

Abstract: A slanted heat exchange system and method for use in aerodynamic vehicle and for transferring heat between a coolant and a fluid. In some examples, the aerodynamic vehicle is an aircraft, and the fluid is air. The slanted heat exchange system and method include a slanted heat exchanger that is slanted relative to a channel direction just before the slanted heat exchanger. The slanted heat exchanger has an increased frontal surface area while still preserving a relatively compact cross-sectional area when viewed from the front. An array of inlet turning vanes both diffuse and slow down the fluid while also turning the fluid to enter the slanted heat exchanger approximately perpendicular to the slanted heat exchanger. This mitigates turning losses and reduces any pressure drop across the heat exchanger. In some examples, an array of outlet turning vanes turns and accelerates the fluid exiting the slanted heat exchanger.

Abstract: A multi-segment oblique flying wing aircraft which has three distinct segments including two outer wing segments and a central wing segment. The central segment may be thicker in the vertical direction and adapted to hold pilots and passengers. The outer wing segments may be substantially thinner and may taper as they progress outboard from the wing center. The multi-segment oblique flying wing aircraft be adapted for rotating into a high speed flight configuration, or may be adapted for take-off and cruise at a constant angle. In an extreme flight case, the central wing segment may rotate to a local sweep of ninety degrees.

Abstract: A variable-geometry cooling airflow management system and method for managing the cooling of a fuel cell on an aerodynamic vehicle (such as an aircraft). The cooling management is achieved by providing a conduit having a fan, radiator, and variable-geometry openings (such as variable-geometry inlet and variable-geometry outlet) at the conduit ends. Heat from the fuel cell is transferred to a coolant, which then flows through the radiator in the conduit. Cooling airflow passes over the radiator to provide fuel cell cooling. The amount of cooling airflow over the radiator is adjusted by varying the size of the variable-geometry inlet, the variable-geometry outlet, or both. Adjustments are made based on the operational parameters of the aircraft such as airspeed and flight configuration. A fan also may be located in the conduit, a speed of which is varied by the control system based on the operational parameters of the aircraft.

Abstract: An aircraft includes a fuel cell system including a fuel cell powered by hydrogen received from a supply of hydrogen, and a propulsion unit including a conduit through which a flow of air is propelled. A first heat exchanger transfers heat from the fuel cell to a coolant fluid located in a coolant loop, and a second heat exchanger is located in the conduit for heating the air passing through the conduit by transferring heat to the air from the coolant fluid via the second heat exchanger. This configuration serves to cool the fuel cell while increasing the efficiency of the propulsion unit.

Abstract: A vertical take-off and landing aircraft which uses fixed rotors for both VTOL and forward flight operations. The wing rotors are tilted forward and provide some forward propulsion during horizontal flight. The rotors are positioned to achieve a high span efficiency. The rotors are positioned to even out the lift across the span of the synthetic wing. The synthetic wing may also have airfoils which may provide structural support for the rotors as well as providing lift during forward flight.

Abstract: The aircraft can include: an airframe, a tilt mechanism, a payload housing, and can optionally include an impact attenuator, a set of ground support members (e.g., struts), a set of power sources, and a set of control elements. The airframe can include: a set of rotors and a set of support members. By utilizing a larger rotor blade area (and/or larger rotor disc area) and adjusting the blade pitch and RPM, the rotors can augment the lift generated by the aerodynamic profile of the aircraft in the forward flight mode in addition to providing forward thrust. Variants generating lift with the rotors can reduce or eliminate additional control surfaces (e.g., wing flaps, ailerons, ruddervators, elevators, rudder, etc.) on the aircraft since the thrust and motor torque is controllable (thereby indirectly controlling lift) at each rotor, thereby enabling pitch, yaw, and/or roll control during forward flight.

Abstract: An aircraft including an airframe and a plurality of propulsion assemblies coupled to the airframe, wherein each propulsion assembly includes an electric motor, a propeller coupled to the electric motor, and a tilt mechanism that connects the propulsion assembly to the airframe and transforms the propulsion assembly between a forward configuration and a hover configuration; wherein the plurality of propulsion assemblies is transformable between a forward arrangement and a hover arrangement, wherein each of the plurality of propulsion assemblies is in the forward configuration in the forward arrangement, wherein each of the plurality of propulsion assemblies is in the hover configuration in the hover arrangement, wherein the spacing between at least two of the propellers of the plurality of propulsion assemblies changes between the forward arrangement and the hover arrangement.

Abstract: A vertical take-off and landing aircraft and method which uses fixed rotors for both VTOL and forward flight operations. The rotors are positioned to achieve a high span efficiency. The rotors are positioned to even out the lift across the span of the wing. The wing may also have narrow front and rear airfoils which may provide structural support as well as providing lift during forward flight, or may have a single center wing. The wing rotors are tilted forward and provide some forward propulsion during horizontal flight.

Abstract: An aircraft propulsion system with a drag reduction portion adapted to reduce skin friction on at least a portion of the external surface of an aircraft. The drag reduction portion may include an inlet to ingest airflow. The aircraft may also have an internally cooled electric motor adapted for use in an aerial vehicle. The motor may have its stator towards the center and have an external rotor. The rotor structure may be air cooled and may be a complex structure with an internal lattice adapted for airflow. The stator structure may be liquid cooled and may be a complex structure with an internal lattice adapted for liquid to flow through. A fluid pump may pump a liquid coolant through non-rotating portions of the motor stator and then through heat exchangers cooled in part by air which has flowed through the rotating portions of the motor rotor. The drag reduction portion and the cooled electric motor portion may share the same inlet.

Abstract: The rotary airfoil 100 defines a cross section and a span, wherein the cross section is a function of the point along the span (e.g., spanwise point) and defines an upper surface and a lower surface at each spanwise point. The rotary airfoil 100 also defines, at a cross section, a lift coefficient (CL) that is a function of the angle of attack at which the airfoil is rotated through the air. The system can optionally include: a rotor hub to mount the rotary airfoil, a tilt mechanism to pivot the rotary airfoil between a forward configuration and a hover configuration, and a pitching mechanism to change the angle of attack of the rotary airfoil 100.

Abstract: A high efficiency hydrogen fuel system for an aircraft at high altitude which utilizes compressors to compress air to a sufficiently high pressure for the fuel cell. Liquid hydrogen is compressed and then utilized in heat exchangers to cool the compressed air, maintaining the air at a temperature low enough for the fuel cell. The hydrogen is also used to cool the fuel cell as it is also depressurized prior to its entry in the fuel cell cycle. A water condensation system allows for water removal from the airstream to reduce impacts to the atmosphere. The hydrogen fuel system may be used with VTOL aircraft, which may allow them to fly at higher elevations. The hydrogen fuel system may be used with other subsonic and supersonic aircraft, such as with asymmetric wing aircraft.

Abstract: A method for controlling an aircraft includes accessing input data indicative of at least airspeed of the aircraft and determining trim values based at least in part on the input data. The trim values includes an angle of attack trim value for the aircraft. The method also includes accessing data indicative of the trim values by a flight controller and controlling, using the flight controller, operation of the aircraft based at least in part on the trim values.

Abstract: The aircraft can include: an airframe, a tilt mechanism, a payload housing, and can optionally include an impact attenuator, a set of ground support members (e.g., struts), a set of power sources, and a set of control elements. The airframe can include: a set of rotors and a set of support members. By utilizing a larger rotor blade area (and/or larger rotor disc area) and adjusting the blade pitch and RPM, the rotors can augment the lift generated by the aerodynamic profile of the aircraft in the forward flight mode in addition to providing forward thrust. Variants generating lift with the rotors can reduce or eliminate additional control surfaces (e.g., wing flaps, ailerons, ruddervators, elevators, rudder, etc.) on the aircraft since the thrust and motor torque is controllable (thereby indirectly controlling lift) at each rotor, thereby enabling pitch, yaw, and/or roll control during forward flight.

Abstract: A method for the control of a vertical take-off and landing (VTOL) aircraft which reduces the acoustic profile of the rotary airfoil in hover for VTOL applications. The rotary airfoil incurs an efficiency penalty in order to improve the acoustic performance during hover. The aircraft operates the rotary airfoils of the propeller during hover in the hover angle of attack range, and the aircraft operates the rotary airfoils during forward flight in the forward angle of attack range.

Abstract: A method for determining airspeed of an aircraft that includes determining a rotor model relating a power coefficient of a propeller of the aircraft to an axial inflow velocity through the propeller as a function of a set of rotor operating parameters; determining the set of rotor operating parameters by sampling an electronic control signal associated with an electric motor actuating the propeller; computing the axial inflow velocity through the propeller based on the set of rotor operating parameters using the rotor model; and determining the airspeed based on the axial inflow velocity.

Abstract: A method and system for modeling aerodynamic interactions in complex eVTOL configurations for realtime flight simulations and hardware testing which includes decomposing the aircraft into aerodynamic subcomponents, wherein the interactions between these components are handled by flow simulations of the surrounding fluid, which may be Euler flow CFD simulations. A computer generated simulation can be used to analyze the fluid flow and pressures, the forces delivered by an aircraft into the fluid and the forces onto the aircraft from the fluid, to determine the position and attitude of the aircraft, and other aspects. The system may be used as a flight simulator for pilot training in a realtime environment. The system may be used to support component testing using an interface to those components, such as flight electronics and actuators, to test the components in high fidelity simulations of actual flight demands on those components.