Propulsion

About: Propulsion is a research topic. Over the lifetime, 24977 publications have been published within this topic receiving 200311 citations.

High performance VTOL convertiplanes

Abstract: A single-tilt-rotor VTOL airplanes have a tiltable rotor attached to an elongated power pod containing the collective and cyclical pitch mechanism, and transmission. The power pod is pivotably attached to a base that is slidably mounted on a pair of slotted guide beams attached on top of the roof of the fuselage. The guide beams run longitudinally from the front of the aircraft to past the center of gravity (CG) of the aircraft in order to transport the power pod from the front section to the center section when converting from the horizontal cruising mode to the VTOL mode. In the horizontal cruising mode, the power pod perched horizontally on top of the fuselage front section with sufficient clearance for the rotor to rotate in front of the aircraft. Upon transitioning to the VTOL mode, a telescopic actuator is used to pivot the power pod vertically while a cable-winch system is used to move the entire power pod and base assembly rearwardly to stop at the center of gravity of the aircraft, and vice versa, thus allowing the power pod to travel significantly rearward and forward as required for proper balancing of vertical lift as the power pod pivots 90 degrees during transition from VTOL mode to the cruising mode. A single piston engine, or a single or pair of turbofan engines, mounted slightly to the rear of the CG, have drive shafts that can be clutched and mated onto respective receiving shaft from the transmission within the power pod in order to power the tiltable rotor. The engine is also attached to a propeller for horizontal propulsion, or if turbofan engines are used, jet thrust is generated for horizontal cruise. A small anti-torque rotor or ducted fan toward the tail of the aircraft is mechanically coupled to the engine via a drive shaft to provide the necessary side-way thrust to overcome the main rotor's torque. In the horizontal cruising mode, the tiltable rotor is allowed to windmill slowly at a minimum rotational speed necessary to maintain the integrity of the rotor blades. The same propulsion principle can be applied to VTOL airplanes having more than one tiltable rotor, thereby can potentially increase the speed, range and reliability of current twin-wing-mounted-tilt-rotor aircraft. A pair of high-aspect-ratio wings on both sides of the fuselage provide highly efficient lift during cruising flight with very little induced drag. Conventional horizontal and vertical tail planes are used for directional stability in the cruising mode.

Integrated and/or modular high-speed aircraft

Abstract: An integrated and modular high-speed aircraft (200) and method of design and manufacture. The aircraft (200) can have a supersonic or near-sonic cruise Mach number. In one embodiment, the aircraft (200) can include an aft body integrated with a delta wing (204) and a rearwardly-tapering fuselage (202) to define a smooth forward-to-rear area distribution. A propulsion system (206), including an engine (216), inlet (220), and exhaust nozzle (222) can be integrated into the aft body to be at least partially hidden behind the wing (204). In one embodiment, the entrance of the inlet can be positioned beneath the wing (204), and the exit of the nozzle (222) can be positioned at or above the wing (204). An S-shaped inlet duct (221) can deliver air to the aft-mounted integrated engine.

Dynamics and control of hypersonic aeropropulsive/aeroelastic vehicles

Abstract: The guidance and control of hypersonic vehicles is examined by studying the airframe/engine/structural-dynamic interactions of a generic vehicle with scramjet propulsion. The pitch-attitude dynamics are described for the vehicle configuration that can sustain hypersonic flight at near-orbital altitudes. These aerospacecraft have strong airframe/engine/elastic coupling in attitude dynamics and engine responses with static instability with respect to pitch. An integrated airframe-engine control system is presented for the control of the system's strong aeropropulsive/aeroelastic coupling. The control methodology utilizes feedback of measured/synthesized values of angle of attack, blended pitch rate, thrust, and combustor-inlet pressure. The multiinput/multioutput engine controller requires high-bandwidth actuation of the fuel-flow control and the effective diffuser ratio. The proposed control laws do not provide optimized performance in terms of pitch response suggesting that additional control crossfeeds and filtering is needed.

Methodology and Historical Perspective of a Hall Thruster Efficiency Analysis

Abstract: to ionization processes and losses that manifest as Joule heating, and contains no information about the vector properties of the jet. Propellant efficiency incorporates losses from dispersion in the jet composition and is unity for 100% ionization to a single ion species. The effect of neutrals on dispersion of the jet velocity distribution function in propellant efficiency is introduced in the neutral-gain utilization. The beam efficiency accounts for divergence of the jet and is ideal when the ion velocity vectors are parallel to the thrust axis. Plume divergence is defined as a momentum-weighted term, and the approximation as a charge-weighted term is characterized. The efficiency architecture is derived from first principles and is applicable to all propulsion employing electrostatic acceleration, including Hall thrusters and ion thrusters. Distinctions and similarities to several past methodologies are discussed, including past ion thruster analyses, early Russian performance studies, and contemporary architectures. To illustratethepotentialforenhancedunderstandingoflossmechanismsandionizationprocesseswithanarrayoffarfield plume diagnostics, a case study is presented of low-discharge voltage operation from a 6 kW laboratory Hall thruster.