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GO Aircraft Ltd. is developing a patented, very high speed VTOL aircraft concept that is twice as fast with more than double the range of any VTOLs flying today.
The High Speed Vertical Takeoff and Landing (HSVTOL) aircraft is a patented aircraft concept, that can be applied to a variety of aircraft sizes and missions, both military and civilian. Patents have been issued in both the U.S. and Great Britain. There is an additional U. S. Provisional Patent Application filed covering further improvements. GO Aircraft Limited (GOAL) has been funded by DARPA by means of SBIR Phase I and Phase II contracts to begin the development of the concept.
Prior to SBIR Phase I, GOAL had accomplished a first iteration of conceptual design that applied the concept to carry 24 combat equipped troops or 32 civil passengers. A scale model was fabricated to aid in the explanation of how the concept works. Note that design improvement has evolved a vehicle configuration somewhat different from that shown in the front view photo . However, the scale model shown can still serve the purpose of helping explain how the HSVTOL concept works.
The photo shows a 1/30th scale model of the 45-foot diameter HSVTOL design in a forward view. As can be seen, the HSVTOL concept takes a revolutionary departure from traditional approaches to air vehicle design. It is scalable through the usual CTOL aircraft sizes from the largest to the fairly smallest. The 45-foot diameter HSVTOL was designed to carry a payload of 6400 pounds, to cruise at 0.86 Mach at 37,000 feet altitude, and to fly without refueling to a range of over 2100 nautical miles.
The HSVTOL concept is shown with 3 engines. Note that in alternative configurations two or three engines can be used. For FOD/stealth and engine performance considerations, inlets can be located on the top of the fuselage. Further, instead of podding, two engines can be embedded in the fuselage.
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The side view shows how the engine exhaust can be diverted into a plenum chamber shown in blue. The fuel is colored red. A portion of the model is cut away to aid in the explanation of its operation. The fan blades of a quadrant of the fan assembly are shown in the open position for vertical flight. In horizontal flight, these fan blades are closed flush to form an aerodynamic surface for conventional lift. Also shown in the cut away is an indication of a cabin configuration.. Hot core flow and cooler fan flow from the three engines are directed through concentric ducts to a toroidal manifold which distributes the gases to the center body peripheral ports. The cooler fan air surrounds the hot core gas to keep the structure cool and to minimize insulation requirements.
The rotating fan is supported by vertical and radial air bearings at the rotation interface. Brush seals and conventional fiber seals contain the gas flow at the interface. The hot engine exhaust gasses and relatively cool fan air are then mixed in the ducting that leads to two-dimensional exhaust nozzles (28 each) at each of the 28 fan blades in the rotor. The nozzles are oriented tangentially to propel the fan assembly, and depressed slightly so as not to impinge on any portion of the aircraft. Brush seals are also used to prevent undesired dust from gaining entrance to the interface cavity.
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At the interface of the fan assembly and the fuselage, the hot engine exhaust gasses are sandwiched radially between two layers of the cooler fan air. The cooler fan air is planned for leakage into the interface cavity, with the amount of leakage minimized by brush seals. Thus, the interface cavity temperatures become equal to that of the fan air. Each of the two-dimensional exhaust nozzles at each fan blade is thus continuously connected with a supply of exhaust gases from the manifold when the fan is rotating. Note that there are no gears or direct mechanical connection between the fan blade assembly and the central body. Drive for the fan is purely pneumatic. Nearly frictionless air bearings carry loads from the fan to the central body.
At the interface of the fan assembly and the fuselage, the hot engine exhaust gasses are sandwiched radially between two layers of the cooler fan air. The cooler fan air is planned for leakage into the interface cavity, with the amount of leakage minimized by brush seals. Thus, the interface cavity temperatures become equal to that of the fan air. Each of the two-dimensional exhaust nozzles at each fan blade is thus continuously connected with a supply of exhaust gases from the manifold when the fan is rotating. Note that there are no gears or direct mechanical connection between the fan blade assembly and the central body. Drive for the fan is purely pneumatic. Nearly frictionless air bearings carry loads from the fan to the central body.
Since there is no mechanical interconnect between the fuselage and the rotating fan assembly, it is only necessary to counteract a very small and uniformly distributed amount of air bearing friction in order to maintain the orientation of the fuselage. GO plans to maintain the orientation of the fuselage by means of a closed loop anti-rotation servo or a vertical tail plus hot gas jets bled from part of the bypass flow of the upper engine exhausts of the HSVTOL.
The rotating fan blade assembly provides inertial stabilization in the same manner as that of the "Frisbee". Gyroscopic control of the HSVTOL is obtained by applying torque to the gyro-like fan blade assembly. In SBIR Phase II, Draper Lab conducted preliminary gyroscopic flight control architecture design, flight control algorithm formulation and analyses using input design data of the HSVTOL from GOAL. The results of Draper's work were very encouraging. The roll and pitch rates obtained were acceptable and subject to further optimization for specific applications.
In vertical takeoff, (electrical or mechanical) torque can be cyclically applied in a number of alternative ways. One way is the actuation of spoilers; another is closing off cyclically the exhaust gas flow to the fan thrusters; or by means of down-wash on aero surfaces. In horizontal flight, torque can be applied by means of aerodynamic surfaces and thrust vectoring.
During transition to horizontal flight, the HSVTOL can probably stay well within the usual advancing and retreating blade rotor limitations similar to helicopters. The fan rotation speed, plus horizontal flight transition speed, can be maintained safely below sonic. Further, the retreating blade speed, less maximum horizontal transition speed, can be maintained safely above stall limits. After transition to horizontal flight, all fan blades are closed and this rotor limitation disappears. When scaling to various sizes of HSVTOLs, fan blade speed is planned to be maintained at approximately 400 fps. In this way, for all sizes of HSVTOLs, transition speed from vertical to horizontal flight can be maintained within limitations.
During the transitional phase of flight, the jet engine exhausts are diverted from the fan assembly to rearward thrusting nozzles on the central fuselage, and the fan blades are closed to form a smooth aerodynamic surface for high-speed horizontal flight.
Aerodynamic coefficients were obtained in Phase I of the DARPA SBIR program by means of wind tunnel tests. Performance analysis using these data and engine data shows that after transitioning to horizontal flight, the GOAL HSVTOL is capable of attaining cruise speeds more than twice that of the most advanced VTOLs flying today.
Relevance and Importance
The HSVTOL aircraft concept can be applied for both military and civil applications. A wing body concept, it takes a revolutionary departure from traditional approaches to air vehicle design to enable vertical takeoff and landing in an aircraft that has subsonic performance similar to that of CTOL fighter aircraft with similar payloads. The HSVTOL's features can be summarized as follows:
- Incorporates only state-of-the-art technologies and does not require any enabling technological breakthroughs.
- Vertical takeoff and landing capability in an aircraft concept that is usually not concerned with controlled flight into terrain accidents (CFIT).
- High subsonic horizontal cruise speeds at altitudes between 37,000 and 50,000 feet.
- Long range or alternatively, long endurance capability similar to CTOL aircraft.
- Payloads similar to CTOL aircraft.
- Almost frictionless, pneumatic fan drive for vertical take-off (no gears nor interconnect shafting)
- Synchronized gyroscopic controls for stabilized and responsive flight characteristics.
- Lower rotor vibration- significantly less noise and vibration levels as compared to helicopters.
- Relatively low acquisition costs based on use of non-exotic materials and low cost fabrication methodology.
Results of preliminary conceptual design and cost analyses plus the fabrication of a 15 foot diameter fan assembly in SBIR Phase I and II work with DARPA, indicates that life cycle costs of a 45 foot diameter HSVTOL could be significantly lower (less than half) as compared to the V-22. These analyses are for comparable production runs and comparable application.
DARPA SBIR Phase II HSVTOL Summary
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The DARPA SBIR Phase II, ground test program of the GOAL proof-of-concept demonstrator 15 ft diameter fan assembly was partially completed on 25 April 2024 at Wyle Laboratories in Norco, CA. The test was a cold gas flow, mechanically driven static test of the capability of the fan rotor to achieve the necessary vertical thrust for VTOL operations. In the case of the 15 foot diameter 3900 pound HSVTOL demonstrator vehicle, the design target is 4300 pounds vertical thrust at a rotor speed of 760 RPM. Since this was a cold gas flow mechanically driven test (in the flight vehicle, the rotor is to be driven by a hot gas flow pneumatic drive without a gear train), a T-53 gas turbine provided torque for rotor acceleration through a non-flight-article gearing system. Pre-test checkout runs to 400 RPM were completed. In the first test run, as the rotor speed accelerated past 300 RPM, the test gearing drive system from the T-53 failed catastrophically limiting further data collection. |
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In the adjacent figure are plotted two curves. One curve shows test results (RPM vs. Thrust) and extrapolation of results to design thrust. The second curve shows fan design thrust versus RPM. The fan performed approximately 55% better than design, achieving design thrust at 610 RPM rather than 760 RPM.
Promising military and commercial applications.
Military Aircraft Market Niches.
- UAV Market. The Navy has recently funded studies to establish Mission Needs Statement (MNS) for a Multi Role Endurance (MRE) Unmanned Ariel Vehicle (UAV). This would establish Milestone 0 in DoD's acquisition procedure for weapon systems. The preliminary size requirements appear to be at approximately the size of GOAL's Proof-of-concept (PoC) SBIR Phase III demonstrator.
- Military C-130 Replacement (C-XXX). This is an established Air Force requirement. The Air Force Special Operations Command has expressed strong interest in such an aircraft.
- The Director DDR&E;, Dr. Hans Mark has indicated that the replacement of the C-130 with a vertical takeoff, long range, high speed aircraft concept as a foremost military need. The GOAL HSVTOL appears to satisfy all requirements. As compared to other VTOL aircraft concepts, the GOAL HSVTOL appears to have a significant speed, range and cost advantage. As compared to the stopped rotor concept, the GOAL HSVTOL appears to have a speed, and cost advantage.
Civil Aircraft Market Niches.
Commercial Aircraft and Aerospace Market. GOAL will address the commercial aircraft market needs for executive passengers, oil field support, commuter airliners, medical transport, early warning aircraft and all other markets currently met by the helicopter and airplane. The potential civilian markets will include any market where it could serve as a viable replacement for helicopters, the B-B 609 tiltrotor and commuter airliners. Low operating and low acquisition costs are very important marketing features. This civil market includes:
- Business. Flying passengers far distances and requiring speed and safety calls for an aircraft design such as GOAL's which is economical to operate and can get passengers there quickly. Vertical takeoff and landing capability is essential in the avoidance of congested airports to save significant amounts of time or to act as a feeder aircraft to congested airports that are unable to handle increased air traffic.
Significant amounts of the executive's time may be saved driving to and from very congested airports and waiting to board and disembark large aircraft. The HSVTOL's vertical takeoff capability would enable use of convenient heliports atop buildings or small fields and community airports to enable the executive to fly directly to another heliport or small field close his meeting appointment.
- Utility. GOAL's fast cruising speed would allow it to cover great distances quickly and hover in tight locations such as high mountainous areas to drop off supplies or return with passengers. It's ability to land in a variety of terrain would be very beneficial to search and rescue operations. Speed is critical in saving lives in medical emergencies.
NOTE: All the Information and Images belongs to Aerowebspace.com
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