The notion of floating slowly above the ground, in absolute luxury, watching the beautiful scenery pass by beneath you is about to once again become a reality.
Details have just been released the a of a full production version of the Airlander 10 aimed specifically at civilian use. As compared to the current functioning prototype, the new model will have a sleeker, more aerodynamic hull. This design update is based on both wind tunnel testing and computer modelling, along with data gathered during test flights of the prototype. Its changed shape is particularly visible in the form of a rounder nose, and a new tail section.
The cabin will also be more aerodynamic, plus it will be longer. The latter is made possible due to the fact that components such as the fuel module, which are currently slung below the prototype's hull, are being moved up into the hull. As a result, the cabin can now be up to 46 meters long by 6 m wide. In that configuration, it offers 195 m² of floor space, not including the flight deck.
Hybrid Air Vehicles, the UK company that is adapting the original technology for civilian use, previously released images of what a deluxe tourist-carrying version of that cabin might look like.
Other changes include the addition of a bow thruster for better manoeuvrability during ground handling, along with a move from non-retractable to retractable landing gear. Additionally, whereas the prototype's two front rotatable propulsors are currently ducted, they will be unducted on the production model. This should not only reduce weight, but also improve their ability to generate directional thrust.
Overall, the production version of the Airlander 10 will be five percent longer than the prototype, which itself is 92 m in length. That said, Hybrid Air claims that it should be more fuel-efficient than the original, allowing it to "deliver up to a 75-percent reduction in emissions over comparable aircraft."
The Prototype
The Hybrid Air Vehicle HAV 304/Airlander 10 is a hybrid airship designed and built by British manufacturer Hybrid Air Vehicles (HAV). Comprising a helium airship with auxiliary wing and tail surfaces, it flies using both aerostatic and aerodynamic lift and is powered by four diesel engine-driven ducted propellers.
The HAV 304 was originally built for the United States Army's Long Endurance Multi-intelligence Vehicle (LEMV) programme. Its maiden flight took place in 2012 at Lakehurst, New Jersey, in the US. In 2013, the LEMV project was cancelled by the US Army.
HAV reacquired the airship and brought it back to Cardington Airfield in England. It was reassembled and modified for civilian use, and in this form was re-designated the Airlander 10. The modified aircraft completed design certification testing before being written off when it came loose from its moorings in a high wind.
During the 1990s, the UK based company Hybrid Air Vehicles (HAV) formed a partnership with US aerospace and defence company Northrop Grumman to promote the type in defence markets, particularly in the US.
Following the successful demonstration of the HAV-3 small-scale demonstrator, and with Northrop Grumman as the prime bidder, the hybrid airship concept was accepted for the US Long Endurance Multi-intelligence Vehicle (LEMV) project, in preference to the Lockheed Martin P-791 that had also been submitted.
Lockheed Martin P-791
The LEMV programme was intended to demonstrate a medium-altitude long-endurance unmanned aerial vehicle capable of providing Intelligence, surveillance, target acquisition, and reconnaissance (ISTAR) support for ground troops. Besides HAV, UK and US subcontractors included Warwick Mills (fabric engineering and development), ILC Dover (specialised engineering development and manufacturing services), Textron subsidiary AAI Corporation (US Army OneSystem UAV/surveillance aircraft control & information distribution station), Stafford Aero Technologies (flight control systems) and SAIC (full-motion video processing). Northrop Grumman were responsible for the integration of the various electro-optical/infrared, signals intelligence, radar and communications relay payloads onto the airship.
Requirements included the capability to operate at six kilometres (20,000 ft) above mean sea level, a 3,000-kilometre radius of action, and a 21-day on-station availability, provide up to 16 kilowatts of electrical power for payload, be runway independent and carry several different sensors at the same time. According to the U.S. Army, the LEMV was to have been a recoverable and reusable multi-mission platform. It could be forward located to support extended geostationary operations from austere locations and capable of beyond-line-of-sight command and control. The developmental prototype emerged as the HAV 304, a helium-filled airship with twin conjoined hulls having a total internal capacity of 38,000 m³ .With an overall length of 91 metres, the airship was longer than any contemporary rivals. However, several mid-20th century airships were longer: for example, the German Hindenburg-class airships were 245 metres long. The "largest-ever" non-rigid airship, the U.S. Navy's ZPG-3W 1950s-era military airborne early warning airship, was longer at 123 m and larger with a 42,450-cubic-metre envelope capacity.
Operationally, the LEMV was intended to be typically flown autonomously or as a remotely operated aircraft; for being transported to theatres of operation or within normal civil airspace, the airship can also be flown by onboard operators. According to Northrop's projections, one LEMV could provide the equivalent work of 15 fixed-wing medium-altitude aircraft.
The LEMV was intended to be capable of a wide variety of roles, including enhanced ISR (Intelligence, surveillance and reconnaissance) capabilities, beyond-line-of-sight communications and signals intelligence collection. It would integrate with existing ground station command centres and equipment used by ground troops in forward operating bases, making its data available to multiple users and analysts and reducing the information shortfall during operations.
The LEMV would be able to operate, like a helicopter, from small forward bases. Its operating cost and endurance were expected to be better than other surveillance options. It was intended to be the longest endurance UAV in the world.
The airship could serve as a steady communications relay, ensuring that groups of soldiers in mountainous areas would never lose contact with one another, even if they do not have direct line of sight to each other. The LEMV could have tracked important convoys, key roadways, or other key infrastructure as semi-permanent overwatch escorts, monitor an urban area of interest to prepare for major battles or enforce security, or focus on shutting down border chokepoints. The LEMV would have enabled the American DoD to fly the most technologically advanced payloads in the near term as they became available.
Following cancellation of the LEMV project, the deflated HAV 304 was repurchased by HAV, returned to the UK and hangared at Cardington Airfield. There it was reassembled, refurbished and modified for a more general role; accordingly, the aircraft was no longer an example of the HAV 304 design, having been rebuilt into the Airlander 10 prototype instead.
The Airlander 10 is designed primarily for civilian use. However, it can, like the HAV 304, be fitted for a wide variety of defence roles.
The HAV 304 / Airlander 10 is a hybrid airship, achieving lift, and thereby flight, via both aerostatic and aerodynamic forces. Unlike most airship designs, it does not have a circular cross-section, having adopted an elliptical shape with a contoured and flattened hull. This shaping is deliberate so that it acts as a lifting body, contributing aerodynamic lift while the airship is in forward motion; generating up to half of the airship's lift in a similar manner to that of a conventional fixed-wing aeroplane. Buoyancy is also provided by helium contained within the envelope, the pressure from which maintains the airship's unique shape, between 60 and 80% of the aircraft's weight is supported by the lighter-than-air helium. The Airlander 10 is equipped with a set of pneumatic skids that are designed to let the airship land and take off from a wide variety of terrain, as well as from water.
The Airlander 10 is capable of staying aloft for five days while crewed, and over two weeks while unmanned. The type had the potential for various civil and military applications; these include transportation purposes, conducting aerial surveillance, acting as a communications relay, supporting disaster relief operations, and various passenger services such as leisure flights and luxury VIP duties. Many of these duties could involve different configurations of the airship's mission module to suit. Northrop also said the LEMV could be used as a cargo aircraft, claiming that it had enough buoyancy to haul 7,000 kg of cargo 3,900 km at 50 km/h. According to HAV, the design would allow operators to choose among trade-offs between endurance and cargo capacity, carrying up to a maximum of 14,000 kg of cargo.
The Airlander 10 possesses a sizeable flight deck with four large floor-to-ceiling windows, providing a high level of external visibility. While the airship had originally been envisioned to be unmanned, HAV adopted an optionally piloted approach as a result of customer interest in such operations. In 2015, positions for a single pilot and an observer had been installed in the Airlander HAV intend to adopt a twin-pilot configuration along with a greater prevalence of glass cockpit-style controls and instrumentation in the future. The airship is controlled by a side-stick mounted on the right-hand side, somewhat resembling that of a rotorcraft; there are no rudder pedals, the side-stick being automatically slaved to the vanes instead. Garmin-built avionics furnish the cockpit; the suite includes a closed-circuit television system that enables the pilot to view the otherwise-distant engines.
The propulsion units and flying surfaces are both connected to the flight control system via fly-by-optics, using optical fibre cables to efficiently cope with the vast scale of the vehicle. The pilot's controls are various switches and potentiometers, which are connected to the Flight Control System to produce digital signals encoded into light pulses by one of three FCS-Masters and transmitted to the appropriate FCS-Satellite located around the vehicle. These 11 FCS-Satellites then connect electrically to the appropriate equipment including flying surface actuators, engine controls, Secondary Power Distributors etc. Outputs from these various units also take the return path back to the flight deck via the Flight Control System to provide feedback to the pilot on engine conditions, flying surface positions, Secondary Power conditions etc. Transitioning between the vehicle's multiple modes of flight is regulated directly by the flight control system, enabling the vehicle to be operated locally, remotely or in an unmanned configuration. According to HAV, the designing of the flight control regime was eased by the natural pendulum stability of the airship.
The hull of the airship comprises a skin made of triple-layered combination of composite materials. The skin provides considerable strength and rigidity when inflated, serving to keep in the gas, retain its unique shape, and support the four engines, fins and the flight deck that are attached directly upon it. Materials used include Vectran, Kevlar, Tedlar, Polyurethane, and Mylar; the Mylar layer, enveloped within polyurethane film layers, forms the airship's gas barrier. The Airlander 10 lacks any internal framework; weight from the payload module is distributed across every frame via cables running across and into the hull as well as internal diaphragms. According to HAV's Technical Director Mike Durham, the entirety of the airship's structural strength is derived from being inflated to just above atmospheric pressure with a 4-in. water gauge pressure differential this strength is due to the huge diameter of the vessel despite the relatively-low pressure differential.
The hull is internally divided by diaphragms into a total of six main compartments with additional sub-divisions; these divisions can be sealed in the event of emergencies, such as battle damage being sustained, allowing for the majority of the airship's helium, and thereby lift capacity, to be retained. Ballonets are housed within these compartments in order to regulate gas pressure; these are inflated on the ground to increase density and reduce lift. Air and helium are not allowed to mix in the ballonets, thus enabling each to be furnished with valves and fans in order to increase and decrease air volume independently; this approach is claimed by HAV to be unique to the airship.
According to estimates performed by Northrop, the biggest foreseen threat to the HAV 304 is adverse weather conditions, such as high winds or thunderstorms, that could buffet the craft. The threat posed by windy conditions is in part due to its vast surface area in comparison to most aircraft; in particular, ground operations are more difficult in such conditions, but not thought to reach the extent of becoming impossible. According to HAV chief test pilot David Burns, the danger from missiles was relatively low as they can pass through the airship without forcing it down. The skin is reportedly capable of handling small arms fire and other causes of tears due to a level of built-in redundancy and the relatively-low pressure difference between the inside and outside of the hull.
The Airlander 10 is powered by a total of four Thielert Centurion 325 hp V8 diesel engine which drive sets of three-bladed ducted propellers to provide the thrust for both flight and manoeuvring. These engines are positioned in pairs, one set being located towards the rear of the airship, while the other are positioned alongside the sides of the forward fuselage, mounted on stub wings. Each engine is furnished with a 50 kW generator, which provides electrical power for the airship and its mission systems.
The assembly for each of the side-mounted engines can be pivoted 20 degrees in either direction, vectoring the thrust to provide flight control, particularly during landing and taking off; the rear-mounted engines are fixed. By employing thrust vectoring, the engines can direct their thrust downwards to provide additional lift during take-off. A series of four triangular-shaped variable vanes are positioned behind the engines to provide further control authority by re-directing thrust from the rear engines over the tail fins.
While cruising at altitude, propulsion can be switched to a more efficient electric drive fed from the airship's central generator. Due to the hybrid aerostatic/aerodynamic lift approach, fuel can be expended without entering a state of positive buoyancy that would necessitate routine helium venting in order to land, a costly weakness present upon conventional airships. Fuel is primarily contained within the 12-metre-long main fuel module housing up to nine tons of fuel; the main tank is supplemented by separate rear and forward tanks, containing up to four. To optimise cruising efficiency, the angle of incidence can be adjusted by pumping fuel between the fore and aft tanks.
