Zeppelin NT
The Zeppelin NT is a class of helium-filled airships being manufactured since the 1990s by the German company Zeppelin Luftschifftechnik GmbH in Friedrichshafen. The initial model is the N07. The company considers itself the successor of the companies founded by Ferdinand von Zeppelin which constructed and operated the very successful Zeppelin airships in the first third of the 20th century. There are, however, a number of notable differences between the Zeppelin NT and original Zeppelins as well as between the Zeppelin NT and usual non-rigid airships known as blimps. The Zeppelin NT is classified as a semi-rigid airship.
There are various roles for the Zeppelin NT; traditional roles have been aerial tourism purposes and for conducting passenger services. The Zeppelin NT have also been used for observation platforms, such as for aerial photographers and by television commentators covering major events. Due to their capability for low-vibration flight for up to 24 hours at a time, ZLT considers the airships suitable for research missions for environmental observation, troposphere research and natural resource prospecting. The envelope of the airship has also been used for advertising purposes.
Development
The modern development and construction embodied by the Zeppelin NT had been financed by a long-standing endowment, which had been initially funded with money left over from the earlier Zeppelin company, that had been under the trusteeship of the Mayor of Friedrichshafen. A stipulation had been placed upon the endowment that limited the use of its funds to the field of airships. Over the many years, the investment value of the endowment grew to a point where it had become viable for the funds to be put to use for the purpose of designing, developing, and constructing of a new generation of Zeppelins.In 1988, the first considerations into the technological and economic feasibility of reviving the Zeppelin industry began; this included examinations of historic Zeppelin documentation as well as current designs for airships. In December 1990, a feasibility study and accompanying market research program found an initial sales potential for around eighty Zeppelin airships for purposes such as tourism, advertising, and scientific research. In mid 1991, the newly formed development team filed several patents on various technologies that would be later used on the subsequent airship, these included propeller arrangements, structure and girder design, and ballonet implementation. In March 1991, a flyable remote control proof of concept model was demonstrated, which is claimed to have revealed excellent flight characteristics from the onset.
In September 1993, the Zeppelin Luftschifftechnik GmbH was founded in Friedrichshafen as a corporate spin-off of the original Zeppelin company to pursue development and production of the new generation of Zeppelins, later known as the Zeppelin NT. By spring 1994, preparatory studies for a full-sized prototype were underway. In 1995, the Luftfahrt-Bundesamt, Germany's civil aviation authority, officially recognized ZLT as a design organisation, and approved new construction regulations for airships. In November 1995, final assembly of the first airship prototype commenced, it was promoted as being the first rigid airship to be produced by the firm since the Second World War. In July 1996, the under-construction prototype of the Zeppelin N07 was presented to the public and the media. In September 1997, the prototype performed its maiden flight at Friedrichshafen; piloted by US test pilot Scott Danneker, it flew for a total of 40 minutes.
On 8 August 1998, the Zeppelin N07 prototype performed a cross-country flight via Altenrhein, Switzerland to Echterdingen near Stuttgart, Germany; at the end of this journey, the prototype also accomplished its first masting away from Friedrichshafen upon landing at Stuttgart Airport. The test program included noise level measurements, avionics tests, and take-offs and landings. In October 1999, the prototype completed a journey, its longest distance flight at that point. According to the manufacturer, the Zeppelin N07 prototype had proven the technical design by mid 1998, and thus could be applied to production models without major modifications.
On 2 July 2000, the centennial of the first Zeppelin flight, the prototype was christened D-LZFN Friedrichshafen by Count Zeppelin's granddaughter, Elisabeth Veil. In July 2000, the prototype performed a high-profile tour of Germany, travelled more than in about 75 flight hours and appearing at the Expo 2000 at Hannover. By December 2000, the flight test programme was completed; during which, the prototype had accumulated in excess of 800 flight hours over roughly 220 flights. In June 2001, the prototype appeared at the Paris Air Show, the occasion being the first time that a Zeppelin had cruised above Paris since the 1920s.
In May 1999, the production of the components for the first production airship was started. In February 2000, the support structure assembly of the first series airship was completed, while the envelope was attached to the support structure in May that year. In 2001, the company formally commenced series manufacturing of the Zeppelin NT, and began the commercial exploitation of the airships. In April 2001, the Luftfahrt-Bundesamt issued type certification for the Zeppelin N07, a key step towards commercial operations; that same month, ZLT became a certified airship-manufacturing company. On 19 May 2001, the first production airship conducted its maiden flight, flying for two and a half hours. On 10 August 2001, the first production airship SN 02 was christened D-LZZR Bodensee by Carl, Duke of Württemberg; five days later, it began providing commercial passenger services, initially involving one-hour sightseeing flights over Lake Constance to members of the public up to ten times per day.
Design
Overview
The Zeppelin NT series are a family of semi-rigid airships, combining the design principles of rigid airships and blimps together. The Zeppelin N07, the base model and most commonly constructed to date, are long, with a volume of. They are thus considerably smaller than the old Zeppelins, which reached a maximum volume of, such as the LZ 129 Hindenburg. Furthermore, they are inflated exclusively with the non-flammable noble gas helium, rather than with hydrogen.The Zeppelin NT, designed more than 60 years after the last generation of Zeppelins were built and making use of advances in material science and computer-aided design, is claimed to overcome some of the typical maneuverability, safety, and economic disadvantages of airships. In particular, the propulsion system offers significantly increased safety. In standard operations with a maximum payload, the lifting gas cells do not create enough buoyancy to make the whole ship lighter than air. The negative buoyancy is overcome with the application of engine power. The buoyancy can change when traveling with a reduced payload and partially emptied fuel tanks, but typically the Zeppelin NT starts a journey with a net downward force of about ; on long trips, the airship can become lighter–than–air if much of its fuel is consumed.
The design typically has a range of some and reaches top speeds of. The standard cruising speed of for tourist flights can be attained using the rear propeller only. Standard operational altitude is, but up to is possible. Their maximum permitted takeoff weight is, with a payload of. A long endurance system can also be installed for extended range and longer flight times.
Hull and structure
The Zeppelin NT is a semi-rigid airship. It is unlike both the original Zeppelins that had a rigid skeleton and non-rigid blimps. It has an internal triangular truss made of graphite-reinforced plastic and three longitudinal girders made of welded aluminium which connect the triangular elements along the length of the frame. Additionally, the structure is tightened with aramid cords to provide for extra rigidity. All major components, such as the engines, control cabin and the steering fins, are mounted upon the structure; this allows maneuverability to be maintained even in the event of envelope pressure being lost. The whole structure weighs only about.The envelope contains the lighter-than-air helium which gives the airship its buoyancy. Inside historical Zeppelins, the gas cells were separate entities from the hull; however, on the Zeppelin NT, the envelope serves both as the aircraft's hull and as the gas cell. It is made of a three-layered laminate: one gas-tight layer of Tedlar, one polyester fabric layer to provide stability and one polyurethane layer suitable for plastic welding that acts to connect the separate laminate panels. To preserve its outer form, a slight overpressure of about is maintained within the hull. As in blimps, the interior pressure is kept constant at all flight altitudes by using ballonets. The ballonets have a total volume of.
On the external surfaces of the Zeppelin NT are several equipment attachment points, including multiple hardpoints present for the purpose of installing cameras of up to 65 kg weight; an optional nose-mounted boom can be installed for attaching sensor equipment or scientific probes. Payloads can also be suspended underneath the airship via a cargo hook arrangement using the floor hatch present in the cabin. Due to the center of gravity and the location of the cabin being different, two sets of non-retractable landing gear are installed on the underside of the airship, the forward set being directly attached to the cabin's underside and the aft set upon the primary structure itself.
Propulsion and steering
Power for the Zeppelin NT's propulsion systems is provided by a trio of Textron Lycoming IO-360 boxer aviation engines, fueled by standard aviation gasoline. These engines are mounted on the sides and rear of the structure itself to provide optimum efficiency; this arrangement also increases in-flight comfort due to reduced levels of propeller noise and vibration. In addition to thrust, each engine also provides maneuverability via their swiveling propellers; the two forward engines are equipped with hydraulically-actuated tilting propellers which are usually aligned horizontally, but can be turned 90° upward or 30° downward, while the aft engine powers a fixed lateral propeller. Each engine is furnished with separate fuel tanks and supply systems that typically operate independently of one another.The swiveling propellers have been claimed to have provided the Zeppelin NT with unique flight characteristics, such as being able to hover precisely, fly backwards, take off vertically, and turn on its axis. The functionality of the swiveling propellers allows the Zeppelin NT to carry out both take-offs and landing operations entirely in the vertical plane. During such operations, only three ground personnel are required, lowering costs and minimizing turnaround times as a consequence. In 2010, development of an improved propeller capable of quieter operation was completed.
Instead of four rudder and elevator fins set on the airship's empennage, the Zeppelin NT uses only three identical fins; one fin being set at the top with the others offset at an angle of 120 degrees to either side of the top fin. This arrangement not only saves weight, but as a side effect, the loss of one fin can be compensated with the remaining two. The aerodynamically balanced rudders are equipped with independent electrical actuators.