Blended-wing-body, tail-sitter aircraft

Abstract

An aircraft includes a blended-wing-body airframe that defines a center-body region exhibiting a center-body aerodynamic center forward of a center of mass of the aircraft within a horizontal flight envelope of the aircraft. This airframe also defines an outer-wing region exhibiting an outer-wing aerodynamic center aft of the center of mass of the aircraft within the horizontal flight envelope of the aircraft. Additionally, the aircraft includes a vertical landing subsystem configured to, in a vertical landing configuration, contact a ground surface and structurally support the aircraft, as well as a propulsion subsystem.

Description

BLENDED-WING-BODY, TAIL-SITTER AIRCRAFTCROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This Application claims the benefit of U.S. Provisional Application No. 63 / 657,462, filed on 07-JUN-2024, which is incorporated in its entirety by this reference.TECHNICAL FIELD

[0002] This invention relates generally to the field of aircraft design and, more specifically, to a new and useful blended-wing-body, tail-sitter aircraft in the field of aircraft design.BRIEF DESCRIPTION OF THE FIGURES

[0003] FIGURE 1A is a schematic representation of one variation of an aircraft in a horizontal flight configuration.

[0004] FIGURE IB is a schematic representation of one variation of the aircraft in a vertical flight configuration.

[0005] FIGURE 2A is a schematic representation of one variation of the aircraft.

[0006] FIGURE 2B is a schematic representation of one variation of the aircraft.

[0007] FIGURE 2C is a schematic representation of one variation of the aircraft.

[0008] FIGURE 2D is a schematic representation of one variation of the aircraft.

[0009] FIGURE 3 is a perspective-view, schematic representation of one variation of a blended-wing-body airframe.

[0010] FIGURE 4 is a schematic representation of one variation of the aircraft in the vertical landing configuration.

[0011] FIGURE 5 is a schematic representation depicting relative locations of a center-body region and an outer-wing region for one variation of a blended-wing-body airframe.

[0012] FIGURE 6A is a vertical cross-section depicting an arrangement of a cargo compartment in one variation of the aircraft.

[0013] FIGURE 6B is a horizontal cross-section depicting the arrangement of a cargo compartment in one variation of the aircraft.

[0014] FIGURE 7A is a schematic representation of one center-body airfoil profile section in a set of center-body airfoil profile sections for one variation of the center-body region of the blended-wing-body airframe.

[0015] FIGURE 7B is a schematic representation of one center-body airfoil profile section in the set of center-body airfoil profile sections for one variation of the center-body region of the blended-wing-body airframe.

[0016] FIGURE 7C is a schematic representation of one center-body airfoil profile section in the set of center-body airfoil profile sections for one variation of the center-body region of the blended-wing-body airframe.

[0017] FIGURE 7D is a schematic representation of one center-body airfoil profile section in the set of center-body airfoil profile sections for one variation of the center-body region of the blended-wing-body airframe.

[0018] FIGURE 8 is a graphical representation of a twist distribution of one variation of the aircraft.

[0019] FIGURE 9 is a graphical representation of a center of pressure distribution for one variation of the aircraft.

[0020] FIGURE 10A is a schematic representation of one outer- wing airfoil profile section in a set of outer-wing airfoil profile sections for one variation of the outer-wing region of the blended-wing-body airframe.

[0021] FIGURE 10B is a schematic representation of one outer- wing airfoil profile section in the set of outer-wing airfoil profile sections for one variation of the outer-wing region of the blended-wing-body airframe.

[0022] FIGURE 10C is a schematic representation of one outer- wing airfoil profile section in the set of outer-wing airfoil profile sections for one variation of the outer-wing region of the blended-wing-body airframe.

[0023] FIGURE 10D is a schematic representation of one outer-wing airfoil profile section in the set of outer-wing airfoil profile sections for one variation of the outer-wing region of the blended-wing-body airframe.

[0024] FIGURE 10E is a schematic representation of one outer-wing airfoil profile section in the set of outer-wing airfoil profile sections for one variation of the outer-wing region of the blended-wing-body airframe.

[0025] FIGURE 10F is a schematic representation of one outer- wing airfoil profile section in the set of outer-wing airfoil profile sections for one variation of the outer-wing region of the blended-wing-body airframe.

[0026] FIGURE 11 is a schematic representation of an outer-wing sweep angle progression for one variation of the aircraft.

[0027] FIGURE 12 is a schematic representation of a set of control surfaces of one variation of the aircraft.

[0028] FIGURE 13 is a schematic representation of a vertical landing subsystem of one variation of the aircraft.

[0029] FIGURE 14A is a schematic representation of a vertical landing subsystem of one variation of the aircraft in a horizontal flight configuration.

[0030] FIGURE 14B is a schematic representation of a vertical landing subsystem of one variation of the aircraft in a vertical landing configuration.

[0031] FIGURE 15 is a frontal schematic representation of a propulsion system for one variation of the aircraft.

[0032] FIGURE 16 is a frontal schematic representation of a propulsion system for one variation of the aircraft.

[0033] FIGURE 17 is a frontal schematic representation of a propulsion system for one variation of the aircraft.

[0034] FIGURE 18 is a frontal schematic representation of a propulsion system for one variation of the aircraft.

[0035] FIGURE 19 is a frontal schematic representation of a propulsion system for one variation of the aircraft.DESCRIPTION OF THE EMBODIMENTS

[0036] The following description of embodiments of the invention is not intended to limit the invention to these embodiments but rather to enable a person skilled in the art to make and use this invention. Variations, configurations, implementations, example implementations, and examples described herein are optional and are not exclusive to the variations, configurations, implementations, example implementations, and examples they describe. The invention described herein can include any and all permutations of these variations, configurations, implementations, example implementations, and examples.

[0037] Generally, the term “can,” as utilized herein, indicates an action or attribute of the system, which may or may not be executed by or be applicable to the system depending on the implementation or embodiment of the system.

[0038] Generally, the term “include,” as utilized herein, can mean “comprise,” “consist of,” or “consist essentially of’ and is not restricted to any one of the above interpretations throughout.

[0039] Generally, the term “set,” as utilized herein, can include a single instance or multiple instances of an associated object. Descriptors such as “first,” “second,” “third,” etc., as utilizedherein, do not imply a sequence or order unless otherwise specified but do imply separate instances of the associated object.

[0040] Generally, the terms “planar,” “symmetric,” “coaxial,” “parallel,” “perpendicular,” and other terms characterizing the relative position defining characteristics of physical objects, as utilized herein, describe substantial adherence to the aforementioned concepts within mechanical tolerances. For example, if one component is “parallel” to another, this indicates that the central axes of these components are parallel within a predefined tolerance.

[0041] Generally, various components and characteristics of the aircraft are described herein with respect to one or more axes of the aircraft. The terms “longitudinal axis” and “longitudinally,” as utilized herein, refer to the axis of the aircraft aligned with the intended direction of forward motion of the aircraft. Various descriptors are utilized herein to refer to positions and relative positions along the longitudinal axis of the aircraft. For example, terms such as “leading,” “fore,” “forward,” and the like refer to longitudinal positions or relative positions toward the front of the aircraft when the aircraft is traveling in the intended direction of forward motion. Terms such as “trailing,” “aft,” “behind,” and the like refer to longitudinal positions toward the rear of the aircraft when the aircraft is traveling in the intended direction of forward motion. Additionally, the symbol x with various subscripts is utilized herein to refer to positions along the longitudinal axis, where x represents the distance from the nose of the aircraft.

[0042] Generally, the terms “lateral axis,” “laterally,” “span-wise,” and the like refer to the axis of the aircraft perpendicular to the longitudinal axis of the aircraft and spanning the wingtips of the aircraft. Various descriptors are utilized herein to refer to positions and relative positions along the lateral axis. For example, terms such as “inner,” “inside,” “inward,” “center,” “central,” “centrally,” and the like refer to positions and relative positions along the lateral axis toward a point equidistant from the wingtips of the aircraft or a point laterally aligned with the longitudinal axis of the aircraft. Terms such as “outer,” “outside,” “outward,” and the like refer to positions and relative positions along the lateral axis toward the wingtips of the aircraft. Additionally, the symbol y with various subscripts is utilized herein to refer to positions along the lateral axis, where y represents the distance from the center of the longitudinal axis of the aircraft. Furthermore, the symbol b is utilized herein to refer to the length of the wingspan or “span” of the aircraft.

[0043] Generally, the term “vertical axis” and the like refer to the axis of the aircraft perpendicular to both the longitudinal axis and the lateral axis. Various descriptors are utilized herein to refer to positions and relative positions along the vertical axis. For example, terms suchas “above,” “upward,” “upper,” “top,” and the like refer to positions along the vertical axis toward the sky when the aircraft is in upright horizontal flight. Terms such as “below,” “downward,” “lower,” “bottom,” and the like refer to positions along the vertical axis toward the ground when the aircraft is in upright horizontal flight. Additionally, the symbol z with various subscripts is utilized herein to refer to positions along the vertical axis, where z represents the distance from the center of the longitudinal axis of the aircraft.

[0044] Generally, the term “horizontal flight envelope” refers to a range of aerodynamic and aircraft-related conditions, such as angles of attack, propulsion subsystem configurations, control surface configurations (in implementations in which control surfaces are present), airspeeds, air pressures, or any other metric relevant to the controllability of the aircraft in horizontal flight, in which the aircraft is capable of controllable horizontal flight. Depending on the intended operational characteristics of the aircraft, the horizontal flight envelope of the aircraft may be defined differently. Generally, the term “horizontal flight configuration” refers to the state of the aircraft achieving sustained flight within the horizontal flight envelope of the aircraft.

[0045] Generally, the term “VTOL flight envelope” refers to a range of aerodynamic and aircraft-related conditions, such as angles of attack, propulsion subsystem configurations, control surface configurations (in implementations in which control surfaces are present), airspeeds, air pressures, or any other metric relevant to the controllability of the aircraft in vertical flight, in which the aircraft is capable of controllable vertical flight. Depending on the intended operational characteristics of the aircraft, the VTOL flight envelope of the aircraft may be defined differently. Generally, the term “VTOL flight configuration” refers to the state of the aircraft when flying within the VTOL flight envelope of the aircraft.

[0046] Generally the term “transition flight configuration” refers to the aerodynamic and aircraft-related conditions, such as angles of attack, propulsion subsystem configurations, control surface configurations (in implementations in which control surfaces are present), airspeeds, air pressures, or any other metric relevant to the controllability of the aircraft as the aircraft transitions from the VTOL flight envelope to the horizontal flight envelope or from the horizontal flight envelope to the VTOL flight envelope.

[0047] Generally, the term “vertical landing configuration” refers to a state or conditions of the aircraft when the aircraft is stationary and contacting the ground via the vertical landing subsystem of the aircraft. Generally, in the vertical landing configuration, the aircraft is oriented such that the longitudinal axis of the aircraft is substantially perpendicular (i.e., defining an angle of greater than 75 degrees) to the ground surface, thereby enabling the aircraft to transition from the vertical landing configuration directly into the VTOL flight configuration of the aircraft.

[0048] Generally, various symbols are utilized herein to represent various characteristics and properties relating to the aircraft. More specifically: is utilized herein to represent a local lift coefficient of an airfoil profile section or region of the aircraft; F is utilized herein to represent a local lift force of an airfoil profile section or region of the aircraft; g is utilized herein to represent acceleration due to gravity; F is utilized herein to represent a force due to gravity on 9 the aircraft; M, with various subscripts, is utilized herein to represent moments about various points on the aircraft; c is utilized herein to represent the local chord length of an airfoil profile section of the aircraft; is utilized herein to represent a reference chord length of the aircraft;t / c is utilized herein to represent a thickness-to-chord ratio of an airfoil profile section of the aircraft; is utilized herein to represent an aerodynamic center of an airfoil profile section of the aircraft as a proportion of local chord length; x is utilized herein to represent the center ofgravity of the aircraft as a proportion of local chord length; x is utilized herein to represent a cp center of pressure of an airfoil profile section of the aircraft as a proportion of local chord length; and a is utilized herein to represent an angle of attack of the aircraft in degrees. Additionally, the “center-body” and “outer-wing” modifiers may be applied to any of the above symbols to designate contributions specifically from the center-body region or the outer-wing region respectively.

[0049] Generally, positions along chords of airfoil profile sections are provided as a percentage or proportion of the total chord length of the airfoil profile section, with 0%, or 0.0, referring to the leading edge of the airfoil profile section, and 100%, or 1.0, referring to the trailing edge of the airfoil profile section. Unless otherwise specified, x values provided for “center-body” or “outer-wing” contributions are distances normalized by the reference chord length, whichcan be the maximum chord length of the blended-wing-body airframe and / or a virtual chord spanning the full length of the blended-wing-body airframe extending beyond any single chord of the blended-wing-body airframe.

[0050] Generally, characteristics of the aircraft related to airfoil sections and / or regions of a blended-wing-body are intended to describe those airfoil sections and / or regions of the blended-wing-body within the horizontal flight envelope of the aircraft, unless otherwise specified. For example, the “aerodynamic center” of an airfoil is well-defined and relevant to the shape of an airfoil within the horizontal flight envelope of the aircraft. However, a different “aerodynamic center” may or may not exist for conditions of the aircraft outside of the horizontalflight envelope. Therefore, “aerodynamic center” when utilized herein refers to the well-defined aerodynamic center of the airfoil or region of the blended-wing-body within the horizontal flight envelope of the aircraft.1. Aircraft

[0051] As shown in FIGURE 1A and FIGURE IB, an aircraft 100 can include a blended-wing-body airframe 110: defining a center-body region 111 exhibiting a center-body aerodynamic center forward of a center of mass of the aircraft within a horizontal flight envelope of the aircraft; and defining an outer- wing region 121 exhibiting an outer- wing aerodynamic center aft of the center of mass of the aircraft within the horizontal flight envelope of the aircraft. The aircraft can also include a vertical landing subsystem 130 configured to, in a vertical landing configuration 106: contact a ground surface; and structurally support the aircraft. Additionally, the aircraft includes a propulsion subsystem 140.

[0052] One variation of the aircraft includes a propulsion subsystem 140 configured to control the aircraft via differential thrust configured to control the aircraft in a VTOL flight configuration 104 and a horizontal flight configuration 102.

[0053] Another variation of the aircraft, depicted in FIGURE 2A, includes a blended-wing-body airframe 110: defining a center-body region 111 exhibiting a positive partial derivative of a center-body center of pressure with respect to an angle of attack of the aircraft; and defining an outer- wing region 121 exhibiting a negative partial derivative of an outer- wing center of pressure with respect to the angle of attack of the aircraft. Alternatively, this variation of the aircraft can be described as including a blended-wing-body airframe 110: defining a center-body region 111 exhibiting aft movement of a center-body center of pressure as an angle of attack of the aircraft increases within a horizontal flight envelope of the aircraft; and defining an outer-wing region 121 exhibiting forward movement of an outer- wing center of pressure as the angle of attack of the aircraft increases within the horizontal flight envelope of the aircraft.

[0054] Yet another variation of the aircraft, depicted in FIGURE 2B, includes a blended-wing-body airframe 110: defining a center-body region 111 exhibiting, within a horizontal flight envelope of the aircraft, a center-body center of pressure forward of a center-body aerodynamic center, the center-body aerodynamic center forward of a center of mass of the aircraft; and defining an outer- wing region 121 exhibiting, within the horizontal flight envelope of the aircraft, an outer-wing center of pressure aft of an outer-wing aerodynamic center, the outer-wing aerodynamic center aft of the center of mass of the aircraft.

[0055] Yet another variation of the aircraft, depicted in FIGURE 2C, includes a blended-wing-body airframe 110: defining a center-body region 111 exhibiting, within ahorizontal flight envelope of the aircraft, a center-body partial derivative of a center-body lift coefficient with respect to a pitch of the aircraft; and defining an outer- wing region 121 exhibiting, within the horizontal flight envelope of the aircraft, an outer-wing partial derivative of an outer-wing lift coefficient with respect to the pitch of the aircraft greater than the center-body partial derivative of the center-body lift coefficient with respect to the pitch of the aircraft. Alternatively, this variation of the aircraft can be described as including a blended-wing-body airframe 110: defining a center-body region 111 exhibiting, within a horizontal flight envelope of the aircraft, a center-body rate of increase of a center-body lift coefficient as an angle of attack of the aircraft increases; and defining an outer- wing region 121 exhibiting, within the horizontal flight envelope of the aircraft, an outer-wing rate of increase of an outer-wing lift coefficient as the angle of attack of the aircraft increases, wherein the outer-wing rate of increase is greater than the center-body rate of increase.

[0056] Yet another variation of the aircraft, depicted in FIGURE 2D, includes a blended-wing-body airframe 110. In this variation, the blended-wing-body airframe 110: defines a center-body region 111 characterized by a set of center-body airfoil profile sections 112, each center-body airfoil profile section including a leading-edge-carved lower surface 113; and defines an outer- wing region 121 adjacent to and laterally outside of the center-body region 111 and characterized by a set of outer- wing airfoil profile sections 122, each outer- wing airfoil profile section including an outer- wing lower surface 123 defining one or fewer curvature inflection points. More specifically, the leading-edge-carved lower surface 113 of each center-body airfoil profile section includes: a leading convex segment 114; a concave segment 115 aft of the leading convex segment 114 and located within a forward 50% of a chord of the center-body airfoil profile section; and a trailing convex segment 116 aft of the concave segment.

[0057] However, the aforementioned variations are not mutually exclusive and can each represent a blended-wing-body airframe 110 exhibiting static stability in pitch within a horizontal flight envelope of the aircraft. Additionally, the aforementioned variations of the aircraft can each represent a blended-wing-body airframe 110 defining a unitary lifting surface (i.e., without additional lifting surfaces such as a horizontal stabilizer and / or vertical stabilizer).2. Applications

[0058] Generally, the blended-wing-body, tail-sitter aircraft (hereinafter, “the aircraft”) combines beneficial characteristics of blended-wing-body aircraft, such as high aerodynamic efficiency, increased lift, and increased internal volume, with beneficial characteristics of vertical take-off and landing (hereinafter “VTOL”) aircraft, such as takeoff and landing location flexibility. More specifically, due to these aforementioned characteristics, the aircraft is characterized byimproved range and operational horizontal airspeed relative to existing VTOL aircraft, thereby enabling applications in rapid point-to-point delivery of cargo. Additionally, some variations of the aircraft are characterized by static stability in pitch without the use of an elevator, a tail, or reflex-cambered airfoil profile sections, thereby further improving aerodynamic efficiency relative to other statically stable blended-wing-body aircraft.

[0059] In applications of the aircraft for which static stability in pitch is not a design goal, the aircraft can exhibit an alternative lift distribution that increases the lift generated by the outer wing relative to the center body, resulting in greater aerodynamic efficiency. The aircraft can achieve these improvements with a propulsion subsystem 140 capable of thrust-vectoring or propulsive control via differential thrust and a blended-wing-body airframe 110 with particular characteristics that accommodate VTOL functionality while achieving stability and aerodynamic efficiency goals. Thus, the aircraft offers multiple advantages compared to existing blended-wing body and VTOL aircraft.

[0060] One application of the aircraft includes rapid point-to-point delivery of cargo between non-airport locations. For example, the aircraft can leverage increased range relative to other VTOL aircraft to transport organs for transplant that require fast transit times between hospitals (e.g., kidneys and blood). In another example, the aircraft can transport high-value cargo between locations that would otherwise require multiple vehicle hand-offs, thereby reducing the risk that the cargo is lost, damaged, or otherwise compromised during transit.

[0061] In another application, the aircraft can leverage improved efficiency relative to other VTOL aircraft to fly non-airport routes while utilizing lower-energy-density power sources (e.g., non-hydrocarbon fuels), such as chemical batteries or hydrogen fuel cells. Thus, the aircraft can reduce the environmental impact of non-airport point-to-point cargo transport as well as cargo transport involving an airport connection.

[0062] In yet another application, the aircraft can operate as an autonomous aerial vehicle capable of carrying cargo over long distances safely by leveraging the static stability of the aircraft to obviate safety concerns over power failures in flight. More specifically, in power failure circumstances in which existing VTOL aircraft are uncontrollable, the aircraft can maintain controlled flight and glide to a controlled landing.3. Blended-Wing-Bodv Airframe

[0063] As shown in FIGURE 3, the aircraft includes a blended-wing-body airframe 110 (or fuselage) to which other components are mounted, integrated with, or housed by. Additionally, the blended-wing-body airframe 110 includes particular features to enable the aircraft to land in a vertical landing configuration 106 (i.e., a tail-sitting configuration), as shown in FIGURE 4,while maintaining stability and aerodynamic efficiency. More specifically, the blended-wing-body airframe 110 defines a center-body region 111 and an outer-wing region 121, each with distinct shaping to enable efficient flight while maintaining the ability of the aircraft to land and take off from the vertical landing configuration 106. In particular, the blended-wing-body airframe 110 defines aerodynamic shaping that balances lift forces generated by the center-body region 111 and the outer- wing region 121 fore and aft of the center of gravity of the aircraft respectively. Additionally, the blended-wing-body airframe 110 defines a planform that does not extend aft beyond the extent of the vertical landing subsystem 130 when deployed in the vertical landing configuration 106, thereby enabling the aircraft to tail-sit on the vertical landing subsystem 130 without the blended-wing-body airframe 110 contacting the ground. However, due to the shorter longitudinal dimensions of the blended-wing-body airframe 110 relative to other blended-wing-body aircraft, the blended-wing-body airframe 110 defines additional characteristics such as a lower outer-wing sweep angle and a leading-edge-carved center-body region 111 to enable stability and aerodynamic efficiency goals while maintaining the shorter planform. More specific characteristics of the blended-wing-body aircraft are further described below.

[0064] In one implementation, the blended-wing-body airframe 110 defines a unitary lifting surface. More specifically, in this implementation, the blended-wing-body defines a single contiguous surface (with the exception of integrated control surfaces) from which the aircraft generates substantially all non-propul si ve lift within the horizontal flight envelope. In particular, in this implementation, the aircraft exhibits stability in pitch without the inclusion of a secondary lifting surface, such as a horizontal stabilizer.

[0065] As shown in FIGURE 5, the blended-wing-body airframe 110 defines the center-body region 111 and the outer-wing region 121 based on a change in cross-sectional geometry between the center-body region 111 and the outer- wing region 121 that can occur at approximately 40% of half-span (2y / b = 0. 40 ±0. 05), in some implementations. More specifically, the airfoil profile sections of the center-body region 111 each include a leading-edge-carved lower surface 113 characterized by two curvature inflection points transitioning from a leading convex segment 114, to a concave segment, and back to a trailing convex segment 116, within the forward 50% of the chord, while the airfoil profile sections of the outer- wing region 121 section define classical airfoil shapes including one or fewer curvature inflection points. In particular, the transition in airfoil shaping between the center-body region 111 and the outer wing region in cooperation with the spanwise twist distribution enable a reversal of the relative longitudinal positions of the aerodynamic center and center of pressure of the center-body region 111compared with the predictions of thin airfoil theory. Thus, the center-body region 111 is able to effect a stabilizing moment forward of the center of mass of the aircraft that balances the rearward lift generated by the outer- wing region 121.

[0066] Generally, the blended-wing-body airframe 110 defines the center-body region 111 based on a lateral transition section, y at which the concavity of the leading-edge-carved center-body airfoil profile section becomes convex. In some implementations, the transition point, y approximately coincides with a section at which x = x or the sectional center of pressure, x cp ac cp, is collocated with the sectional aerodynamic center, x^. Therefore, in this implementation, the blended-wing-body airframe 110 defines the center-body region 111 as the lateral region where y < y and defines the outer- wing region 121 as the lateral regions on either side of the center-body region 111 where y > y

[0067] In one implementation, the blended-wing-body airframe 110 defines: a center-body region 111 characterized by a set of center-body airfoil profile sections 112 for which x <and an outer- wing region 121 characterized by a set of outer- wing airfoil profile sections 122 for which x > x^. Thus, the blended-wing-body defines the center-body region 111 and outer- wing region 121 with distinct sets of airfoil profile sections to achieve the above-described aerodynamic properties.

[0068] Equivalently, the blended-wing-body airframe 110 can: define the center-body region 111 within which a partial derivative of a sectional center of pressure with respect to an angle of attack of the aircraft is positive; and define the outer-wing region 121 within which the partial derivative of the sectional center of pressure with respect to the angle of attack of the aircraft is negative. More specifically, the blended-wing-body can exhibit characteristics such that, at the transition point, y for each section in the span of the blended-wing-body airframe 110 where y < yt, x moves aft with increasing angle of attack (dx^ / da > 0), and, for each section in the span of the blended-wing airframe where y > yt, x moves forward with increasing angle of attack (dx / da < 0). Thus, in this implementation, the center-body region 111 experiences cp nose up moments about the center-body aerodynamic center while the outer- wing region 121 experiences nose down moments about the outer-wing aerodynamic center.

[0069] In another implementation, the blended-wing-body airframe 110 exhibits an aerodynamic transition region, [y , y ] around the geometrically defined transition point, y in the span ofthe blended-wing-body airframe 110. Within the transition region, the relative position of x and may vary unpredictably for various angles of attack and other flow conditions.

[0070] In yet another implementation, the blended-wing-body airframe 110 defines airfoil profile sections characterized by thickness-to-chord ratios of up to 45% within the center-body region 111 to accommodate larger volumes of cargo or cargo with larger vertical dimensions despite the relatively short longitudinal dimensions of the blended-wing-body airframe.

[0071] As shown in FIGURES 6 A and 6B, the blended-wing-body airframe 110 can house power sources (e.g., batteries), fuel (e.g., petroleum-based fuel, hydrogen fuel, stored electric energy), the vertical landing subsystem 130, internal cargo compartments 126 and / or passenger compartments, a cockpit, electrical and hydraulic circuitry, a sensor suite, a control system (i.e., an autonomous or semi-autonomous computer system), a pressurization system, an HVAC system, and / or any other component contributing to operation of the aircraft in the aircraft’s intended capacity as cargo and / or passenger air transport. In one implementation, the blended-wing-body airframe 110 facilitates balance about the center of gravity of the aircraft via the inclusion of an electrochemical battery 128 forward of a cargo compartment 126 and forward of the propulsion subsystem 140.

[0072] Structural components of the blended-wing-body airframe 110 can be constructed from a variety of materials, including steel, aluminum, titanium, composites (e.g., carbon fiber), plastics, foam, rubbers, and / or any other material selected for a particular mechanical application within the blended-wing-body airframe 110.

[0073] The blended-wing-body airframe 110 can define the center-body region 111 and the outer-wing region 121 as a continuous blended airfoil. Alternatively, the blended-wing-body can define a center-body region 111 mechanically coupled to non-contiguous outer-wing region 121 to facilitate construction of the blended-wing-body airframe 110. However, the blended-wing-body airframe 110 can be constructed in any other manner that achieves target aerodynamic and structural attributes.3.1 Center-Body Region

[0074] Generally, the blended-wing-body defines a center-body region 111 configured to generate lift forward of the center of gravity of the aircraft to balance lift generated aft of the center of gravity of the aircraft by the outer- wing region 121 of the blended-wing-body airframe 110 and to increase the total lift generated by the blended-wing-body when operating within the horizontal flight envelope. More specifically, the blended-wing-body defines a center-body region 111 characterized by a set of center-body airfoil profile sections 112 characterized by leading-edge-carved lower surfaces 113. Additionally, the blended-wing-body can define acenter-body region 111 characterized by a positive centerline twist increasing laterally toward two twist maxima 120 located symmetrically about the lateral centerline, such that the two twist maxima exceed the positive twist at the lateral centerline by at least one-half of a degree (i.e., 0.5 degrees). In one implementation, the two twist maxima exceed the positive twist at the lateral centerline by at least three degrees. Also, the blended-wing-body airframe 110 defines a center-body region 111 characterized by the set of center-body airfoil profile sections 112 that exhibit centers of pressure forward of aerodynamic centers of the center-body airfoil profile sections. Thus, the blended-wing-body defines a center-body region 111 with multiple distinct characteristics that together achieve target stability and aerodynamic efficiency within the horizontal flight envelope of the aircraft.

[0075] As shown in FIGURES 7A, 7B, 7C, and 7D, the blended-wing-body airframe 110 can define the center-body region 111 characterized by the set of center-body airfoil profile sections 112 with leading edge carving, which, when combined with the three-dimensional flow around the center-body region 111, creates an aerodynamic center that is behind the 25% chord point as predicted by thin airfoil theory (e.g.„ between 27% and 33% of chord length). Thus, the blended-wing-body airframe 110 can exhibit an overall aerodynamic center (i.e., neutral point) behind the center of pressure of the aircraft within the horizontal flight envelope of the aircraft.

[0076] FIGURE 7A shows one example of a center-body airfoil profile section 112A located at the lateral centerline, 2y / b = 0. FIGURE 7B shows one example of a center-body airfoil profile section 112B located at the lateral positions, 2y / b = 0. 05. FIGURE 7C shows one example of a center-body airfoil profile section 112C located at the lateral positions, 2y / b = 0. 2. FIGURE 7D shows one example of a center-body airfoil profile section 112D located at the lateral positions, 2y / b = 0. 36. Thus, as represented in FIGURES 7A-7D, the center-body region 111 can define a set of center-body airfoil profile sections 112 characterized by leading-edge concavities of spanwise decreasing length and depth.

[0077] Generally, the center-body region 111 can include specific center-body airfoil profile section shaping that can be adjusted, with the aforementioned parameters, depending on the specific weight distribution, target handling characteristics, target flight regime, and other design parameters for the aircraft. More specifically, the center-body region 111 can be characterized by airfoil profile sections in which the leading convex segment 114 and the concave segment are positioned anywhere within the forward 50% of the chord length of each section to effect target aerodynamic characteristics. Additionally, while the curvature inflection point from the concave profile occurs within the forward 50% of the chord of each center-body airfoil profile section, thesecond convex section can extend from the second curvature inflection point to the trailing edge of each center-body airfoil profile section.

[0078] As shown in FIGURE 8, the blended-wing-body can define the center-body region 111 characterized by a positive centerline twist (at y = 0) increasing laterally to two twist maxima located symmetrically about the lateral centerline. In one implementation, the blended-wing-body airframe 110 defines a center-body region 111 characterized by two twist maxima located at y such that 0. 12 < < 0. 28. Thus, the blended-wing-bodyairframe 110 maintains lift generated by the center-body region 111 even with high degrees of local sweep.

[0079] As shown in FIGURE 9, the blended-wing-body airframe 110 defines a center-body region 111 exhibiting a center of pressure forward of an aerodynamic center of the center-body region 111 forward of the center of gravity of the aircraft as a result of the aforementioned aggressive leading edge shaping and twist distribution of the center-body region 111. This center of pressure distribution is further described below with respect to the stability characteristics of the aircraft.3.1.1. Modular Center-Body

[0080] In one implementation, the aircraft can include a modularly constructed blended-wing-body airframe 110 to enable modular replacement of the center-body region 111 to provide various cargo, instrumentation, and / or equipment configurations. In this implementation, the blended-wing-body airframe 110 can include a set of replaceable modular center-body regions 111. In one example of this implementation, the set of replaceable modular center-body regions 111 can define a set of center-body types such that each center-body type is characterized by a different cargo, instrumentation, and / or equipment configuration. In this implementation, the aircraft can include an electromechanical interface between the set of replaceable modular center-body regions 111 and the outer-wing region 121, enabling a secure mechanical connection between the set of replaceable modular center-body regions 111 and the outer-wing region 121 and electrical connections to supply power and transmit control signals to the propulsion subsystem 140, the vertical landing subsystem 130, and / or any control surfaces mounted to the outer-wing region 121 of the blended-wing-body airframe 110.3.2 Outer-Wing Region

[0081] Generally, the blended-wing-body defines an outer- wing region 121 configured to generate lift aft of the center of gravity of the aircraft to balance lift generated forward of the center of gravity of the aircraft by the center-body region 111 and to increase the total lift generated by the blended-wing-body when operating within the horizontal flight envelope of theaircraft. More specifically, the outer-wing region 121 is characterized by a set of outer-wing airfoil profile sections 122 defining a classical airfoil geometry, i.e., a set of outer-wing airfoil profile sections 122 defining outer- wing lower surfaces 123 with one or fewer curvature inflection points. Additionally, the blended-wing-body can define a set of outer-wing airfoil profile sections 122 configured for the target horizontal flight envelope and a sweep angle that tends toward zero with increasing span to aid in overall balance, given the shorter longitudinal dimensions of the aircraft. In one implementation, the set of outer-wing profile sections can define negative local sweep angles to further aid in balancing the blended-wing-body. Furthermore, as shown in FIGURE 8, the blended-wing-body airframe 110 defines an outer- wing region 121 characterized by a negative twist relative to the centerline twist of the blended-wing-body airframe 110. Thus, the blended-wing-body defines an outer- wing region 121 characterized by specific planform and airfoil shaping to improve stability and lift characteristics of the blended-wing-body airframe 110.

[0082] As shown in FIGURES 10 A, 10B, 10C, 10D, 10E, and 10F, the blended-wing-body airframe 110 can define an outer- wing region 121 characterized by a set of outer- wing airfoil profile sections 122 selected based on a target horizontal flight envelope for the aircraft. FIGURE 10A shows one example of a outer- wing airfoil profile section 122 A located at the lateral positions, 2y / b = 0. 47. FIGURE 10B shows one example of a outer- wing airfoil profile section 122B located at the lateral positions, 2y / b = 0. 55. FIGURE 10C shows one example of a outer-wing airfoil profile section 122C located at the lateral positions, 2y / b = 0. 66. FIGURE 10D shows one example of a outer- wing airfoil profile section 122D located at the lateral positions, 2y / b = 0. 76. FIGURE 10E shows one example of a outer-wing airfoil profile section 122E located at the lateral positions, 2y / b = 0. 87. FIGURE 10F shows one example of a outer-wing airfoil profile section 122F located at the wingtip positions, 2y / b = 1. 00. Thus, as represented in FIGURES 10A-10F, the outer- wing region 111 can define a set of outer- wing airfoil profile sections 122 characterized by classical airfoil profile sections with one or fewer curvature inflection points on the lower surface of each outer-wing airfoil profile section.

[0083] Given the intended VTOL operation of the aircraft, in one implementation, the aircraft operates within a target horizontal flight envelope characterized by relatively low airspeeds and Mach numbers, such as between Mach 0.05 and Mach 0.5. In this implementation, the blended-wing-body airframe 110 defines an outer-wing region 121 characterized by a set of low-speed outer- wing airfoil profile sections, such as NACA 4412, Clark Y, NASA / LANGLEY LS(l)-0417 (GA(W)-l), Eppler E193, SD7037 or similar airfoils. Alternatively, in implementations of the aircraft capable of higher thrust-to-weight ratios, the aircraft can achievehigher airspeeds and Mach numbers, such as between Mach 0.6 and Mach 0.88. In these implementations, the blended-wing-body airframe 110 defines an outer-wing region 121 characterized by a set of transonic outer- wing airfoil profile sections, such as NACA 64-210, supercritical airfoils, or other similar airfoils. Thus, the blended-wing-body airframe 110 defines an outer- wing region 121 with airfoil profile sections specific to the target horizontal flight envelope of the aircraft.

[0084] Each of the above-mentioned airfoil shapes define shapes with one or fewer curvature inflection points on the lower surfaces of each outer-wing airfoil profile section. As a result, the set of outer- wing profile sections exhibit an x « 0. 25 as predicted by thin airfoil theory and anose down pitching moment about x and about the center of mass of the aircraft, therebycounteracting the nose up pitching moment provided by the center-body region 111.

[0085] As shown in FIGURE 11, the blended-wing-body airframe 110 can define an outer-wing region 121 characterized by an initial leading-edge sweep angle of between 35 and 65 degrees at the transition from the center-body region 111 that reduces to less than 20 degrees with increasing span. Additionally or alternatively, the blended-wing-body airframe 110 can define an outer- wing region 121 characterized by an initial midpoint sweep between 35 and 65 degrees at the transition from the center-body region 111 that reduces to 0 degrees with increasing span. In one implementation, the blended-wing-body airframe 110 defines an outer-wing region 121 characterized by a wingtip leading edge sweep angle of less than 10 degrees in order to reduce the pitch moment of lift generated by the outer- wing region 121 relative to the center of mass of the aircraft without introducing any undesirable handling characteristics typical of forward swept wings. Alternatively, the aircraft includes an outer- wing region 121 with a negative sweep angle (i.e., forward swept wings) to further decrease the pitch moment about the center of gravity of the aircraft. Thus, the blended-wing-body airframe 110 defines an outer-wing region 121 with significantly lower sweep angles than existing blended-wing-body aircraft to accommodate the aircraft’s vertical landing configuration 106, VTOL flight configuration 104, and stability targets with respect to the center-body region 111.

[0086] As shown in FIGURE 8, the blended-wing-body airframe 110 can define an outer- wing region 121 characterized by a negative twist, such that the centerline twist exceeds the outer-wing twist by between zero and five degrees. In one implementation, the blended-wing-body defines an outer- wing region 121 characterized by a set of outer- wing airfoil profile sections 122 characterized by an outer-wing twist at least one degree less than the centerline twist. In another implementation, the blended-wing-body defines an outer-wing region 121 characterized by a set of outer- wing airfoil profile sections 122 characterized by anouter-wing twist at up to five degrees less than the centerline twist. Thus, by maintaining angular separation between airfoil profile sections in the center-body region 111 and the outer- wing region 121, the blended-wing-body airframe 110 can exhibit favorable stability characteristics because changes in pitch may affect the lift generated by the center-body region 111 and the outer- wing region 121 at different rates, which generates a righting moment for the aircraft.3.3 Static Stability in Pitch Variation

[0087] In a statically stable variation, shown in FIGURE 2C, the blended-wing-body airframe110 exhibits pitch stability without utilizing a tail with a horizontal stabilizer or reflex-cambered airfoil profile (i.e., without down-loading) by generating a center-body lift moment and an outer-wing lift moment balanced about the center of mass of the aircraft. More specifically, the aforementioned characteristics of the blended-wing-body airfoil result in the center-body region111 and the outer-wing region 121 exhibiting distinct partial derivatives of their respective lift moments about the center of mass of the aircraft with respect to pitch, dM da. In particular, the center-body region 111 exhibits a center-body dM / da less than an outer-wingL, C enter body dM / da throughout the horizontal flight envelope of the aircraft. In particular, theL, outer— wing blended-wing-body airframe 110 can define a center-body region 111 exhibiting a center-body partial derivative of a center-body lift moment with respect to a pitch of the aircraft; and an outer- wing region 121 further exhibiting an outer- wing partial derivative of an outer- wing lift moment with respect to the pitch of the aircraft greater than the center-body partial derivative of the center-body lift moment with respect to the pitch of the aircraft. Equivalently, the blended-wing-body airframe 110 can define: a center-body region 111 exhibiting, within the horizontal flight envelope of the aircraft, a center-body rate of increase of a center-body lift moment as the angle of attack of the aircraft increases; and define an outer- wing region 121 exhibiting, within the horizontal flight envelope of the aircraft, an outer-wing rate of increase of an outer-wing lift moment as the angle of attack of the aircraft increases, wherein the outer-wing rate of increase is greater than the center-body rate of increase. Because in neutral horizontal flight these lift moments are balanced about the center of mass, the aforementioned difference in regional lift derivatives causes a nose-down moment about the center of mass of the aircraft with increasing pitch and a nose-up moment about the center of mass of the aircraft with decreasing pitch, thereby effecting static stability for the aircraft. Thus, as a increases the lift generated by the outer- wing region 121 acting aft of the center of mass increases at a faster rate than the lift generated by the center-body region 111 acting forward of the center of mass, thereby providing a stabilizing, net nose-down moment about the center of mass of the aircraft. Additionally, the relationship between the center-body lift moment and the outer-wing lift moment remains truefor negative angles of attack within the horizontal flight envelope, thereby producing a stabilizing, net nose-up moment for negative angles of attack.

[0088] Generally, in this variation, the center-body region 111 can generate greater than 50% of the total lift generated by the blended-wing-body airframe 110 in order to maintain static stability in pitch in instances in which the center-body moment arm is shorter than the outer-wing moment arm. In particular, in this variation the blended-wing-body airframe 110 satisfies the stability criterion

[0089] Further, in this variation, shown in FIGURE 2B, the blended-wing-body airframe 110 can define: a center-body region 111 exhibiting, within the horizontal flight envelope of the aircraft a center-body center of pressure forward of a center-body aerodynamic center, the center-body aerodynamic center forward of a center of mass of the aircraft; and an outer- wing region 121 exhibiting, within the horizontal flight envelope of the aircraft, an outer-wing center of pressure aft of an outer-wing aerodynamic center, the outer-wing aerodynamic center aft of the center of mass of the aircraft. More specifically, in the center-body region 111 of the blended-wing-body airframe 110, x while in the outer-wing region 121 of the blended-wing-bodyairframe 110, x > x > x . Thus, the relative positional relationship of the center of pressure, cp ac eg aerodynamic center, and center of mass, changes between the center-body region 111 and the outer- wing region 121.

[0090] Also, in this variation, shown in FIGURE 2A, the blended-wing-body airframe 110 can define: a center-body region 111 exhibiting, within the horizontal flight envelope of the aircraft, a positive partial derivative of a center-body center of pressure with respect to an angle of attack of the aircraft; and an outer- wing region 121 exhibiting, within the horizontal flight envelope of the aircraft, a negative partial derivative of an outer-wing center of pressure with respect to the angle of attack of the aircraft. More specifically, the blended-wing-body airframe 110 can define: a center-body region 111 exhibiting aft movement of a center-body center of pressure as an angle of attack of the aircraft increases within the horizontal flight envelope of the aircraft; and an outer- wing region 121 exhibiting forward movement of an outer- wing center of pressure as the angle of attack of the aircraft increases within the horizontal flight envelope of the aircraft. In particular, in the center-body region 111 of the blended-wing-body airframe 110, 8x / da > 0, cp while in the outer-body region, dx^ / da < 0. Thus, the direction of the center of pressure movement with respect to angle of attack is opposite between the center-body region 111 and the outer- wing region 121 of the aircraft.3.4 Static Instability in Pitch Variation

[0091] In another variation, the blended-wing-body airframe 110 exhibits static instability in pitch, while offering improved aerodynamic efficiency when compared to the statically stable variation. In this variation, the blended-wing-body airframe 110 can be characterized by a set of airfoil profile sections in the center-body region 111 and / or the outer-wing region 121 and / or can be characterized by a twist distribution that improves the aerodynamic performance of the aircraft by increasing the lift generated by the outer- wing region 121 relative to the center-body region 111. More specifically, the blended-wing-body airframe 110 can be characterized by reducing lift generated by airfoil profile sections in the set of airfoil profile sections where x cp is ahead of the x^ (e.g., the center-body region 111) and increasing lift generated by the airfoil profile sections in the set of airfoil profile sections where the x^ is ahead of the x (e.g., the outer-wing region 121). Thus, by shifting the lift distribution of the blended-wing-body airframe 110 toward the outer-wing region 121, which is characterized by higher efficiency airfoil profile sections, this variation of the blended-wing-body airframe 110 can exhibit improved overall aerodynamic efficiency compared to the statically stable variation. In this variation, the aircraft remains controllable despite static instability in pitch via the use of autonomous control subsystems configured to correct deviations from a target a with sufficiently low latency and low overshoot to maintain horizontal flight.4. Control Surfaces

[0092] Generally, the aircraft is controllable in pitch, roll, and yaw via the propulsion subsystem 140 configured to control the aircraft via differential or vectored thrust. By relying on the propulsion subsystem 140 for control, the aircraft can be characterized by lower construction complexity and, therefore, a lower overall weight. Relying on the propulsion subsystem 140 for control also allows the aircraft to operate at the most efficient operating point of the aircraft rather than disturb the flow over the airfoils with control surfaces. However, in some implementations, the blended-wing-body airframe 110 can include a set of control surfaces (e.g., elevons 150 or ailerons) integrated into the trailing edge of the blended-wing-body airframe 110 to add control redundancy in cases of propulsive failure.

[0093] In one implementation, shown in FIGURE 12, the aircraft includes a set of elevons 150 positioned on the trailing edge of the outer- wing region 121 of the blended-wing-body airframe 110. More specifically, the set of elevons 150 can be positioned between 50% and 80% of a semispan of the aircraft within the outer- wing region 121 of the blended-wing-body airframe 110. Thus, in this implementation, the aircraft includes control redundancy and improved controllability at maximum thrust, when differential thrusts cannot be applied.5. Vertical Landing Subsystem

[0094] Generally, the aircraft includes a vertical landing subsystem 130 configured to support the aircraft in a vertical landing configuration 106 and absorb forces imparted to the vehicle while landing and taking off by extending longitudinally beyond the aft extent of the blended-wing-body airframe 110 when the aircraft is in the vertical landing configuration 106. More specifically, the vertical landing subsystem 130 is further configured to, in the vertical landing configuration 106, extend aft of a maximum longitudinal extent of a planform of the blended-wing-body airframe 110.

[0095] In one implementation, shown in FIGURE 13, the aircraft includes a vertical landing subsystem 130 including a set of wingtip-mounted vertically oriented struts capable of bearing the weight of the aircraft and cargo within the aircraft’s designed cargo-carrying capacity.

[0096] In another implementation, shown in FIGURES 12A and 12B the aircraft includes a set of extensible struts housed within the blended-wing-body airframe 110 in a horizontal flight configuration 102 and deployable during the VTOL flight configuration 104 of the aircraft. Upon deployment of the set of extensible struts, the set of extensible struts extends longitudinally aft, beyond the extent of the blended-wing-body airframe 110, in preparation for vertical landing of the aircraft. Additionally, upon transition from the VTOL flight configuration 104 to the horizontal flight configuration 102, the aircraft can retract the set of extensible struts into the blended-wing-body airframe 110.

[0097] In yet another implementation, shown in FIGURE 4, the aircraft includes a vertical landing subsystem 130 extending from the propulsion subsystem 140. In this implementation, the vertical landing subsystem 130 can extend longitudinally from the hub of propellers acting as propulsive units 142 in the propulsion subsystem 140.6. Fuel and Power Sources

[0098] Generally, the aircraft includes a source of fuel and / or a source of power housed by the blended-wing-body airframe 110. In one implementation, the aircraft includes a set of batteries (e.g., lithium-ion batteries) that supply electrical power for both control and propulsion. Alternatively, the aircraft can include a source of liquid fuel (e.g., a set of fuel tanks) in addition to a separate electrical system. In another implementation, the aircraft includes a tank of liquid or gaseous hydrogen and a hydrogen-combusting propulsion system or a hydrogen fuel cell to convert the hydrogen fuel to electrical energy.7. Propulsion Subsystem

[0099] Generally, the aircraft includes a propulsion subsystem 140, which can be configured to control the aircraft in pitch, roll, and yaw in both the horizontal flight configuration 102 and theVTOL flight configuration 104. The propulsion subsystem 140 can include a set of propulsive units 142 defining a propulsion longitudinal extent less than the longitudinal extent of the vertical landing subsystem 130 in the vertical landing configuration 106. Additionally, the propulsion subsystem 140 is configured to control the aircraft via differential thrust between the set of propulsive units 142 and / or via thrust vectoring of one or more of the set of propulsive units 142. Each of the aforementioned variations of the propulsion subsystem 140 is described in further detail below.

[0100] Generally, the propulsion subsystem 140 in coordination with the control system can: control the aircraft in a VTOL flight configuration 104; control the aircraft in a horizontal flight configuration 102; transition the aircraft from the VTOL flight configuration 104 to the horizontal flight configuration 102; and transition the aircraft from the horizontal flight configuration 102 to the VTOL flight configuration 104. More specifically, the propulsion subsystem 140 is configured to: cause the aircraft to take off vertically from the vertical landing configuration 106 into the vertical flight configuration; cause the aircraft to transition from a VTOL flight configuration 104 to a horizontal flight configuration 102 within the horizontal flight envelope of the aircraft; control the aircraft in pitch, roll, and yaw within the horizontal flight envelope of the aircraft; cause the aircraft to transition from the horizontal flight configuration 102 within the horizontal flight envelope of the aircraft to the VTOL flight configuration 104; and cause the aircraft to land vertically in the VTOL flight configuration 104. Thus, the propulsion subsystem 140 can control the aircraft in all phases of flight.

[0100] The aircraft can include a propulsion system including a set of propulsive units 142 of any known type or variation, including but not limited to electric-motor-driven propellers, engine-driven propellers, turbopropellers, or jet engines, arranged in any configuration about the aircraft.7.1 Differential Thrust Variation

[0101] In one variation, the aircraft includes a propulsion subsystem 140 configured to produce differential thrust sufficient to generate pitch moments, roll moments, and / or yaw moments about the center of gravity of the aircraft sufficient to control the aircraft in the horizontal flight configuration 102 and the VTOL flight configuration 104. More specifically, to generate moments about all three control axes of the aircraft, the propulsion subsystem 140 can include a set of propulsive units 142 including three or more propulsive units 142 defining non-coplanar thrust vectors. Thus, in this variation, the aircraft is fully controllable via differential thrust from the set of propulsive units 142.

[0102] As shown in FIGURE 15, the propulsion subsystem 140 includes a set of four propulsive units 142 mechanically coupled to the wingtips of the blended-wing-body airframe 110. More specifically, in this implementation, the propulsion subsystem 140 includes: a first subset of two propulsive units 143 arranged above each wingtip of the blended-wing-body airframe 110; and a second subset of two propulsive units 144 arranged below each wingtip of the blended-wing-body airframe 110. Thus, in this implementation, the propulsion subsystem 140 includes a pair of propulsive units 142 arranged above and below each wingtip and defining longitudinal thrust vectors parallel to the longitudinal axis of the aircraft. In this implementation, the aircraft is fully controllable in the VTOL flight configuration 104 via quadcopter-type control algorithms and can transition into the horizontal flight configuration 102 in which the blended-wing-body airframe 110 produces lift sufficient to maintain horizontal flight.

[0103] In another implementation, the aircraft includes a set of propulsive units 142 mounted to the blended-wing-body airframe 110 via struts and positioned forward of the outer- wing region 121 of the blended-wing-body airframe 110. In one example of this implementation, the aircraft includes four propulsive units 142 mounted above and below each wingtip of the blended-wing-body airframe 110. In this implementation, the aircraft includes a set of propulsive units 142 located closer to the center of gravity of the aircraft, facilitating control of the aircraft in the VTOL flight configuration 104 at the expense of increased drag relative to implementations of the aircraft including a set of aft-mounted propulsive units 142. In another example of this implementation, the aircraft includes additional propulsive units 142 (e.g., six total propulsive units 142) attached to the blended-wing-body airframe 110 via struts extending from the blended-wing-body airframe 110.

[0104] In yet another implementation, shown in FIGURE 16, the propulsion subsystem 140 includes a set of six propulsive units 142 further including: a first subset of two propulsive units 145 coupled to the the blended-wing-body airframe 110 at a trailing edge of the blended-wing-body airframe 110 and vertically overlapping with the blended-wing-body airframe 110; a second subset of two propulsive units 146 attached to the blended-wing-body airframe 110 via a first set of two support struts 147 and arranged above the blended-wing-body airframe 110; and a third subset of two propulsive units 148 attached to the blended-wing-body airframe 110 via a second set of two support struts 149 and arranged below the blended-wing-body airframe 110.

[0105] In yet another implementation, the propulsion subsystem 140 includes a set of three propulsive units 142 defining non-coplanar thrust vectors. In this implementation, the propulsionsubsystem 140 is fully controllable in VTOL flight via tricopter-type control algorithms and can transition into the horizontal flight configuration 102 as described above.

[0106] In yet another implementation, shown in FIGURE 17, the propulsion system can include a set of forward mounted propulsion units 141 forward of the outer-wing region 121 of the aircraft on either side of the center body. In one example of this implementation, the propulsion system can include a set of two forward pointed propellers, one on each side of the center-body region 111 of the aircraft.

[0107] In yet another implementation, shown in FIGURE 18, the propulsion system can includes a subset of forward mounted propulsion units 141 similar to those depicted in the implementation shown in FIGURE 17, in addition to the second subset of propulsion units of two propulsive units 146 attached to the blended-wing-body airframe 110 via a first set of two support struts 147 and arranged above the blended-wing-body airframe 110 and the third subset of two propulsive units 148 attached to the blended-wing-body airframe 110 via a second set of two support struts 149 and arranged below the blended-wing-body airframe 110, as depicted in FIGURE 16.7.2 Thrust- Vectoring Variation

[0108] In one variation, the aircraft includes a thrust-vectoring propulsion subsystem 140 capable of generating variable thrust in a range of configurations contributing to both lift and / or propulsion of the aircraft. More specifically, the aircraft can include a thrust-vectoring propulsion subsystem 140: coupled to the blended-wing-body airframe 110; characterized by at least one degree of freedom relative to the blended-wing-body airframe 110; and configured to generate variable thrust in response to a thrust control signal and transition in at least one degree of freedom, to alter a pitch, yaw, or roll moment about a center of mass of the aircraft induced by the variable thrust, in response to a vectoring control signal. Thus, the aircraft includes a thrust-vectoring propulsion subsystem 140 capable of adding a secondary lift component to the aircraft, thereby providing improved operational capabilities at lower airspeeds and enabling VTOL flight via precise vectoring of the thrust-vectoring propulsion subsystem 140.

[0109] The aircraft can include a thrust-vectoring propulsion subsystem 140, including a set of thrust-vectoring propulsive units 142. The aircraft can include propulsive units 142 such as propellers, turbofan engines, jet engines, or any other propulsive device. Additionally, the aircraft can include propulsive units 142 powered by electricity generated via a set of batteries, solar cells, and / or fuel cells, or propulsive units 142 powered by liquid fuels.

[0110] In one implementation, shown in FIGURE 19, aircraft can include propulsive units 142 mounted within the trailing edge region of the blended-wing-body airframe 110. Additionally oralternatively, the aircraft can include propulsive units 142 mounted forward of the trailing edge region or integrated into the blended-wing-body airframe 110 via cowlings or other structures (e.g., positioned on vertical stabilizers or other structures extending from the blended-wing-body airframe 110). Furthermore, the aircraft can include a propulsive unit positioned centrally (i.e., in line with the longitudinal axis of the blended-wing-body airframe 110) or multiple propulsive units 142 positioned approximately symmetrically relative to the longitudinal axis of the blended-wing-body airframe 110. Additionally, for each propulsive unit in the set of propulsive units 142, the aircraft can include a set of thrust-vectoring mechanisms that can vary in design across the set of propulsive units 142. The aircraft can include a thrust-vectoring propulsion subsystem 140 incorporating multiple thrust-vectoring mechanisms that can be independently controlled via a set of vectoring control signals. Thus, implementations of the aircraft can incorporate a large variety of thrust-vectoring propulsion subsystems 140 to meet the thrust and maneuverability targets for the aircraft.

[0111] In one implementation, the aircraft includes a set of propulsive units 142 coupled to the aircraft via an articulating or actuating interface, such as a gimbal and / or a linear actuator, enabling movement of the propulsive unit in at least one degree of freedom relative to the blended-wing-body airframe 110.7.2.1. Gimballed Electric Propeller

[0112] In one implementation, the aircraft includes a gimballed electrically powered propeller as a propulsive unit for the aircraft. More specifically, the aircraft can include a thrust-vectoring propulsion subsystem 140 including a gimballed electric propeller: characterized by freedom in pitch; and configured to transition in pitch to alter the pitch moment about the center of mass of the aircraft induced by the variable thrust in response to the vectoring control signal. In particular, the thrust-vectoring propulsion subsystem 140 can include a gimballed electric propeller: rotationally coupled to the blended-wing-body airframe 110; and configured to transition to alter the pitch moment of the aircraft induced by the variable thrust, in response to the vectoring control signal.

[0113] In this implementation, the aircraft can include an electric propeller powered by an electric motor driving the shaft of the propeller and powered via a battery, solar cell, fuel cell, and / or any other source of electricity available on the aircraft. Additionally, the aircraft can include a gimbal system to which the electric propeller is mounted that is configured to electrically or hydraulically actuate in response to the vectoring control signal, thereby changing the pitch of the electric propeller and varying the pitch moment imparted by the electric propelleron the blended-wing-body airframe 110. Thus, the aircraft can include a gimballed electric propeller as an effective thrust-vectoring propulsion subsystem 140 for the aircraft.7.2.2. Translating Electric Propeller

[0114] In one implementation, the aircraft includes a translating electrically powered propeller as a propulsive unit for the aircraft. More specifically, a thrust-vectoring propulsion subsystem 140 can include a translating electric propeller: translationally coupled to the blended-wing-body airframe 110; and configured to transition to alter the pitch moment of the aircraft induced by the variable thrust, in response to the vectoring control signal.

[0115] In particular, the aircraft can include a thrust-vectoring propulsion subsystem 140 including a translating electric propeller: characterized by freedom in longitudinal position; and configured to transition in longitudinal position to alter the pitch moment about the center of mass of the aircraft induced by the variable thrust in response to the vectoring control signal.

[0116] In this implementation, the aircraft can include an electric propeller powered by an electric motor driving the shaft of the propeller and powered via a battery, solar cell, fuel cell, and / or any other source of electricity available on the aircraft. In this implementation, the aircraft can include an electric or hydraulic linear actuator that is configured to translate the electric propeller fore and aft, and in a dimension offset from the center of gravity of the aircraft, thereby varying the pitch moment imparted by the thrust generated by the electric propeller on the blended-wing-body airframe 110 as a result of translation of the electric propeller. Thus, the aircraft can include a translating electric propeller as an effective thrust-vectoring propulsion subsystem 140 for the aircraft.7.2.3. Multiple-Degree-of-Freedom Electric Propeller.

[0117] In one implementation, the aircraft includes an electrically powered propeller to generate thrust for the aircraft characterized by more than one degree of freedom in rotation and / or translation. More specifically, the aircraft can include a thrust-vectoring propulsion subsystem 140, including an electric propeller: characterized by greater than one degree of freedom; and configured to alter the pitch moment about the center of mass of the aircraft induced by the variable thrust, in response to the vectoring control signal. In this implementation, the aircraft can include an electric propeller powered by an electric motor driving the shaft of the propeller and powered via a battery, solar cell, fuel cell, and / or any other source of electricity available on the aircraft. For example, in this implementation, the aircraft can vector the electric propeller in both pitch and yaw, enabling further stabilization of the aircraft in yaw. Thus, by enabling movement of the propeller in multiple degrees of freedom, this implementation of the aircraftcan achieve greater vectoring precision and / or responsiveness at the expense of mechanical complexity.8. Sensor Suite

[0118] Generally, the aircraft includes a sensor suite to inform a pilot of the aircraft or an autonomous or partially autonomous control system regarding the physical state of the aircraft during operation. More specifically, the sensor suite can include but is not limited to altitude sensors, airspeed sensors, accelerometers, gyroscopes, magnetometers, inertial measurement units (IMUs), GPS receivers, temperature sensors, pressure sensors, fuel flow sensors, and / or battery condition sensors. Each sensor included in the sensor suite is communicatively coupled to an instrument display panel within the cockpit, the autonomous or partially autonomous control subsystem, or a transmitter for subsequent transmission to a remote control system. Thus, the aircraft is fully outfitted with sensors that generate a set of flight data that inform the coordinated positioning of any control surfaces (if present) and the orientation, positioning, and / or thrust settings of the propulsion subsystem 140.9. Control System

[0119] Generally, the aircraft can include a control system including: a computational unit or set of computational units configured to autonomously, semi-autonomously, or in response to inputs received via a control interface, calculate control signals based on the set of flight data received from the sensor suite; and a communication system configured to transmit the control signals to the controllable components of the aircraft such as the thrust-vectoring propulsion subsystem 140, and any control surfaces integrated with the aircraft. More specifically, the aircraft includes a control system configured to control the aircraft in the VTOL flight configuration 104 and in the horizontal flight configuration 102. In particular, the aircraft includes a control system configured to balance the aircraft during takeoff and initial VTOL flight, transition the aircraft from the VTOL flight configuration 104 to the horizontal flight configuration 102, control the aircraft in pitch, roll, and yaw during horizontal flight, transition the aircraft from the horizontal flight configuration 102 to the VTOL flight configuration 104, and balancing the aircraft while landing in the VTOL flight configuration 104. Thus, the aircraft includes a control system that enables a pilot or autonomous system to maintain control of the aircraft during operation.

[0120] The aircraft can include a computational unit such as an onboard or remotely located computer or set of computers configured to autonomously control the aircraft based on the set of flight data, a specified destination, and other flight control parameters. Alternatively, the aircraft can include a computational unit configured to semi-autonomously coordinate configurations ofthe thrust-vectoring propulsion subsystem 140 and / or any control surfaces integrated with the aircraft to enable a pilot or remote pilot to more easily control the aircraft.

[0121] The aircraft can include an electrical communication system, wherein digital or analog electrical signals are transmitted by wire or wirelessly between components of the aircraft. Additionally or alternatively, the aircraft can include a hydraulic communication system, wherein hydraulic impulses are generated by hydraulic pumps or pistons and transmitted via hydraulic fluid to actuating components of the aircraft. Additionally or alternatively, the aircraft can include a mechanical communication system, wherein mechanical impulses are transmitted via cable actuation or other mechanical means.

[0001] The systems and methods described herein can be embodied and / or implemented at least in part as a machine configured to receive a computer-readable medium storing computer-readable instructions. The instructions can be executed by computer-executable components integrated within the aircraft. The instructions can be executed by computer-executable components integrated by computer-executable components integrated with apparatuses of the types described above. The computer-readable medium can be stored on any suitable computer-readable media such as RAMs, ROMs, flash memory, EEPROMs, optical devices (CD or DVD), hard drives, floppy drives, or any suitable device. The computer-executable component can be a processor, but any suitable dedicated hardware device can (alternatively or additionally) execute the instructions.

[0122] As a person skilled in the art will recognize from the previous detailed description and from the figures and claims, modifications and changes can be made to the embodiments of the invention without departing from the scope of this invention as defined in the following claims.

Claims

CLAIMSWe Claim:

1. An aircraft comprising:• a blended-wing-body airframe: o defining a center-body region characterized by a set of center-body airfoil profile sections, each center-body airfoil profile section comprising a leading-edge-carved lower surface; and o defining an outer- wing region adjacent to and laterally outside of the center-body region and characterized by a set of outer-wing airfoil profile sections, each outer-wing airfoil profile section comprising an outer-wing lower surface defining one or fewer curvature inflection points;• a vertical landing subsystem configured to, in a vertical landing configuration: o contact a ground surface; and o structurally support the aircraft; and• a propulsion subsystem.

2. The aircraft to Claim 1, wherein the leading-edge-carved lower surface of each center-body airfoil profile section in the set of center-body airfoil profile sections comprises:• a leading convex segment;• a concave segment aft of the leading convex segment and located within a forward 50% of a chord of the center-body airfoil profile section; and• a trailing convex segment aft of the concave segment.

3. The aircraft of Claim 1, wherein the propulsion subsystem is configured to:• control the aircraft in a VTOL flight configuration;• control the aircraft in a horizontal flight configuration;• transition the aircraft from the VTOL flight configuration to the horizontal flight configuration; and• transition the aircraft from the horizontal flight configuration to the VTOL flight configuration.

4. The aircraft of Claim 1, wherein the propulsion subsystem is configured to:• cause the aircraft to take off vertically from the vertical landing configuration into the vertical flight configuration;• cause the aircraft to transition from a VTOL flight configuration to a horizontal flight configuration within the horizontal flight envelope of the aircraft;• control the aircraft in pitch, roll, and yaw within the horizontal flight envelope of the aircraft;• cause the aircraft to transition from the horizontal flight configuration within the horizontal flight envelope of the aircraft to the VTOL flight configuration; and• cause the aircraft to land vertically in the VTOL flight configuration.

5. The aircraft of Claim 1, wherein the vertical landing subsystem is further configured to, in the vertical landing configuration, extend aft of a maximum longitudinal extent of a planform of the blended-wing-body airframe.

6. The aircraft of Claim 1, wherein the propulsion subsystem is configured to control the aircraft via differential thrust.

7. The aircraft of Claim 1, wherein the propulsion subsystem comprises a set of four propulsive units comprising:• a first subset of two propulsive units arranged above each wingtip of the blended-wing-body airframe; and• a second subset of two propulsive units arranged below each wingtip of the blended-wing-body airframe.

8. The aircraft of Claim 1, wherein the propulsion subsystem further comprises a set of six propulsive units comprising:• a first subset of two propulsive units: o coupled to the the blended-wing-body airframe at a trailing edge of the blended-wing-body airframe; and o vertically overlapping with the blended-wing-body airframe;• a second subset of two propulsive units: o attached to the blended-wing-body airframe via a first set of two support struts; and o arranged above the blended-wing-body airframe; and• a third subset of two propulsive units: o attached to the blended-wing-body airframe via a second set of two support struts; ando arranged below the blended-wing-body airframe.

9. The aircraft of Claim 1, wherein the blended-wing-body airframe is characterized by static stability in pitch.

10. The aircraft of Claim 1, wherein the thrust-vectoring propulsion subsystem comprises a gimballed electric propeller:• rotationally coupled to the blended-wing-body airframe; and• configured to transition to alter the pitch moment of the aircraft induced by the variable thrust, in response to the vectoring control signal.

11. The aircraft of Claim 1, wherein the thrust-vectoring propulsion subsystem comprises a translating electric propeller:• translationally coupled to the blended-wing-body airframe; and• configured to transition to alter the pitch moment of the aircraft induced by the variable thrust, in response to the vectoring control signal.

12. The aircraft of Claim 1, wherein the blended-wing-body airframe:• defines the center-body region within which a partial derivative of a sectional center of pressure with respect to an angle of attack of the aircraft is positive; and• defines the outer-wing region within which the partial derivative of the sectional center of pressure with respect to the angle of attack of the aircraft is negative.

13. The aircraft of Claim 1, wherein each center-body airfoil profile section in the set of center-body airfoil profile sections is characterized by a positive initial camber.

14. The aircraft of Claim 1 :• wherein the set of center-body airfoil profile sections is characterized by a positive centerline twist at a lateral centerline of the blended-wing-body airframe increasing toward two laterally symmetric twist maxima, wherein the two laterally symmetric twist maxima exceed the positive twist at the lateral centerline by at least one degree; and• wherein the set of outer-wing profile sections is characterized by a negative twist, wherein the centerline twist exceeds the outer-wing twist by between three and five degrees.

15. The aircraft of Claim 1 :• wherein, within the horizontal flight envelope of the aircraft, the center-body region exhibits a center-body center of pressure forward of a center-body aerodynamic center, the center-body aerodynamic center forward of a center of mass of the aircraft; and• wherein, within, the horizontal flight envelope of the aircraft, the outer-wing region exhibits an outer-wing center of pressure aft of an outer-wing aerodynamic center, the outer-wing aerodynamic center aft of the center of mass of the aircraft.

16. The aircraft of Claim 1, wherein, within a horizontal flight envelope of the aircraft, the center-body region generates greater than 50% of a total lift generated by the blended-wing-body aircraft.

17. The aircraft of Claim 1, wherein, within a horizontal flight envelope of the aircraft, the center-body region generates less than 50% of a total lift generated by the blended-wing-body aircraft.

18. The aircraft of Claim 1 :• wherein the center-body region further exhibits a center-body partial derivative of a center-body lift moment about a center of mass of the aircraft with respect to a pitch of the aircraft; and• wherein the outer-wing region further exhibits an outer-wing partial derivative of an outer-wing lift moment about the center of mass of the aircraft with respect to the pitch of the aircraft greater than the center-body partial derivative of the center-body lift moment with respect to the pitch of the aircraft.

19. The aircraft of Claim 1, wherein the outer-wing region is characterized by an initial leading edge sweep angle between 35 and 65 degrees and a wingtip leading edge sweep angle less than 20 degrees.

20. The aircraft of Claim 1, wherein the outer- wing region is characterized by an initial midpoint sweep angle between 35 and 65 degrees and a wingtip midpoint sweep angle of zero degrees.

21. An aircraft comprising:• a blended-wing-body airframe:o defining a center-body region exhibiting a center-body aerodynamic center forward of a center of mass of the aircraft within a horizontal flight envelope of the aircraft; o defining an outer-wing region exhibiting an outer-wing aerodynamic center aft of the center of mass of the aircraft within the horizontal flight envelope of the aircraft;• a vertical landing subsystem configured to, in a vertical landing configuration: o contact a ground surface; and o structurally support the aircraft; and• a propulsion subsystem.

22. The aircraft of Claim 21, wherein the propulsion subsystem is configured to:• control the aircraft in a VTOL flight configuration;• control the aircraft in a horizontal flight configuration;• transition the aircraft from the VTOL flight configuration to the horizontal flight configuration; and• transition the aircraft from the horizontal flight configuration to the VTOL flight configuration.

23. The aircraft of Claim 21, wherein the propulsion subsystem is configured to:• cause the aircraft to take off vertically from the vertical landing configuration into the vertical flight configuration;• cause the aircraft to transition from a VTOL flight configuration to a horizontal flight configuration within the horizontal flight envelope of the aircraft;• control the aircraft in pitch, roll, and yaw within the horizontal flight envelope of the aircraft;• cause the aircraft to transition from the horizontal flight configuration within the horizontal flight envelope of the aircraft to the VTOL flight configuration; and• cause the aircraft to land vertically in the VTOL flight configuration.

24. The aircraft of Claim 21, wherein the vertical landing subsystem is further configured to, in the vertical landing configuration, extend aft of a maximum longitudinal extent of a planform of the blended-wing-body airframe.

25. The aircraft of Claim 21, wherein the propulsion subsystem is configured to control the aircraft via differential thrust.

26. The aircraft of Claim 21, wherein the propulsion subsystem comprises a set of four propulsive units comprising:• a first subset of two propulsive units arranged above each wingtip of the blended-wing-body airframe; and• a second subset of two propulsive units arranged below each wingtip of the blended-wing-body airframe.

27. The aircraft of Claim 21, wherein the propulsion subsystem further comprises a set of six propulsive units comprising:• a first subset of two propulsive units: o coupled to the the blended-wing-body airframe at a trailing edge of the blended-wing-body airframe; and o vertically overlapping with the blended-wing-body airframe;• a second subset of two propulsive units: o attached to the blended-wing-body airframe via a first set of two support struts; and o arranged above the blended-wing-body airframe; and• a third subset of two propulsive units: o attached to the blended-wing-body airframe via a second set of two support struts; and o arranged below the blended-wing-body airframe.

28. The aircraft of Claim 21, wherein the blended-wing-body airframe is characterized by static stability in pitch.

29. The aircraft of Claim 21, wherein the thrust-vectoring propulsion subsystem comprises a gimballed electric propeller:• rotationally coupled to the blended-wing-body airframe; and• configured to transition to alter the pitch moment of the aircraft induced by the variable thrust, in response to the vectoring control signal.

30. The aircraft of Claim 21, wherein the thrust-vectoring propulsion subsystem comprises a translating electric propeller:• translationally coupled to the blended-wing-body airframe; and• configured to transition to alter the pitch moment of the aircraft induced by the variable thrust, in response to the vectoring control signal.

31. The aircraft of Claim 21, wherein the blended-wing-body airframe:• defines the center-body region within lateral transition positions along a span of the blended-wing-body airframe at which a sectional center of pressure equals a sectional aerodynamic center; and• defines the outer-wing region outside of the lateral transition positions.

32. The aircraft of Claim 21, wherein the blended-wing-body airframe:• defines the center-body region within which a partial derivative of a sectional center of pressure with respect to an angle of attack of the aircraft is positive; and• defines the outer-wing region within which the partial derivative of the sectional center of pressure with respect to the angle of attack of the aircraft is negative.

33. The aircraft of Claim 21, wherein each center-body airfoil profile section in the set of center-body airfoil profile sections is characterized by a positive initial camber.

34. The aircraft of Claim 21 :• wherein the set of center-body airfoil profile sections is characterized by a positive centerline twist at a lateral centerline of the blended-wing-body airframe increasing toward two laterally symmetric twist maxima, wherein the two laterally symmetric twist maxima exceed the positive twist at the lateral centerline by at least one degree; and• wherein the set of outer-wing profile sections is characterized by a negative twist, wherein the centerline twist exceeds the outer-wing twist by between three and five degrees.

35. The aircraft of Claim 21 :• wherein, within the horizontal flight envelope of the aircraft, the center-body region exhibits a center-body center of pressure forward of a center-body aerodynamic center, the center-body aerodynamic center forward of a center of mass of the aircraft; and• wherein, within the horizontal flight envelope of the aircraft, the outer-wing region exhibits an outer-wing center of pressure aft of an outer-wing aerodynamic center, the outer-wing aerodynamic center aft of the center of mass of the aircraft.

36. The aircraft of Claim 21, wherein, within a horizontal flight envelope of the aircraft, the center-body region generates greater than 50% of a total lift generated by the blended-wing-body aircraft.

37. The aircraft of Claim 21, wherein, within a horizontal flight envelope of the aircraft, the center-body region generates less than 50% of a total lift generated by the blended-wing-body aircraft.

38. The aircraft of Claim 21 :• wherein the center-body region further exhibits a center-body partial derivative of a center-body lift coefficient with respect to a pitch of the aircraft; and• wherein the outer-wing region further exhibits an outer-wing partial derivative of an outer-wing lift coefficient with respect to the pitch of the aircraft greater than the center-body partial derivative of the center-body lift coefficient with respect to the pitch of the aircraft.

39. The aircraft of Claim 21, wherein the outer-wing region is characterized by an initial leading edge sweep angle between 35 and 65 degrees and a wingtip leading edge sweep angle less than 20 degrees.

40. The aircraft of Claim 21, wherein the outer- wing region is characterized by an initial midpoint sweep angle between 35 and 65 degrees and a wingtip midpoint sweep angle of zero degrees.

41. An aircraft comprising:• a blended-wing-body airframe without reflexed airfoil profile sections: o exhibiting static stability in pitch within a horizontal flight envelope of the aircraft; and o defining a unitary lifting surface within the horizontal flight envelope of the aircraft;• a vertical landing subsystem configured to, in a vertical landing configuration:o contact a ground surface; and o structurally support the aircraft; and• a propulsion subsystem.

42. The aircraft of Claim 41, wherein the blended-wing-body airframe:• defines a center-body region exhibiting a positive partial derivative of a center-body center of pressure with respect to an angle of attack of the aircraft; and• defines an outer-wing region exhibiting a negative partial derivative of an outer-wing center of pressure with respect to the angle of attack of the aircraft.

43. The aircraft of Claim 41, wherein the blended-wing-body airframe:• defines a center-body region exhibiting aft movement of a center-body center of pressure as an angle of attack of the aircraft increases within the horizontal flight envelope of the aircraft; and• defining an outer-wing region exhibiting forward movement of an outer-wing center of pressure as the angle of attack of the aircraft increases within the horizontal flight envelope of the aircraft.

44. The aircraft of Claim 41, wherein the blended-wing-body airframe:• defines a center-body region exhibiting, within the horizontal flight envelope of the aircraft, a center-body center of pressure forward of a center-body aerodynamic center, the center-body aerodynamic center forward of a center of mass of the aircraft; and• defines an outer-wing region exhibiting, within the horizontal flight envelope of the aircraft, an outer-wing center of pressure aft of an outer-wing aerodynamic center, the outer-wing aerodynamic center aft of the center of mass of the aircraft.

45. The aircraft of Claim 41, wherein the blended-wing-body airframe:• defines a center-body region exhibiting, within the horizontal flight envelope of the aircraft, a center-body partial derivative of a center-body lift coefficient with respect to a pitch of the aircraft; and• defines an outer-wing region exhibiting, within the horizontal flight envelope of the aircraft, an outer-wing partial derivative of an outer-wing lift coefficient with respect to the pitch of the aircraft greater than the center-body partial derivative of the center-body lift coefficient with respect to the pitch of the aircraft.

46. The aircraft of Claim 41, wherein the blended-wing-body airframe:• defines a center-body region exhibiting, within the horizontal flight envelope of the aircraft, a center-body rate of increase of a center-body lift coefficient as an angle of attack of the aircraft increases; and• defines an outer-wing region exhibiting, within the horizontal flight envelope of the aircraft, an outer-wing rate of increase of an outer-wing lift coefficient as the angle of attack of the aircraft increases, wherein the outer-wing rate of increase is greater than the center-body rate of increase.

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