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: 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: 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 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.

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 vertical take-off and landing aircraft which uses fixed rotors for both VTOL and forward flight operations. The rotors form a synthetic wing and 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 narrow front and rear airfoils which may provide structural support as well as providing lift during forward flight. The wing rotors are tilted forward and provide some forward propulsion during horizontal flight.

Abstract: A method for the flying of a vertical take-off and landing aircraft which uses fixed rotors for both VTOL and forward flight operations. The rotors form a synthetic wing and 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 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: 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 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 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. 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. The system may also be used to support design analysis in non-realtime to run numerous simulations on different designs and to provide comparative output.

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: 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 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 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.