Until now, three main types of lighter-than-air aircraft structures have been used in the world of airship construction: soft, semi-rigid, and rigid.
The choice of these structures was determined by the purpose of the airship and, consequently, its size. Therefore, the volume of soft airships did not exceed 5-10 thousand cubic meters, semi-rigid ones reached up to 20 thousand cubic meters, and all larger ones were built exclusively using the rigid scheme. It is believed that future airships with volumes ranging from 100 to 800 thousand cubic meters, frequently mentioned in foreign publications, will also fall into the last category.
Unfortunately, we lack sufficient experience in building "super" airships like the "Hindenburgs" and "Macons." Even in the 1930s, the volume of the largest airship built in our country, the B-6, was 18.5 thousand cubic meters.
For example, the highest achievement in the long process of perfecting mooring systems is still considered to be the invention of the French engineer Gutta in 1896 (!!) of the mooring mast, to which Zeppelins were moored by the nose. Later, similar devices were modernized, and, for instance, the mast erected in the English town of Cardington enabled the airship to be refueled with gas, fuel, oil, and water while it turned with the wind like a weather vane. Mini-masts, often installed on mobile transport vehicles like cars and ships, also proved to be quite effective.
The relative simplicity, low cost, and reliability of such moorings allow us to hope that they will be used in the 1980s as well. Naturally, taking into account the new requirements for both Zeppelins and ground servicing systems. Even the use of the set of ropes and blocks invented by the English engineer Scott to facilitate mooring did not eliminate the need for a bivouac team consisting of a dozen skilled specialists. Therefore, designers need to consider mechanizing, if not fully automating, all operations for securing the airship at the mooring.
Many difficulties also arose during the operation of Zeppelins in low-temperature conditions (a common occurrence for our North!), when the danger of icing arose, and the crews' fight against the additional weight of ice was complicated due to the colossal size of the airship's body. Moreover, it should not be forgotten that with sharp temperature fluctuations, the physical and mechanical properties of the structural elements generally worsen. These problems can be solved by using materials that are not afraid of the cold, do not ice up, or by using small ultrasonic impact devices for cleaning.
Of course, it is difficult to cover all the technical issues that need to be resolved even at the early stages of work on a modern airship in one article. But two of them, considered the main ones, should be highlighted.
Let's start with the control of the aerostatic lift force (ALF) of the airship, which depends on the volume, purity, temperature, and pressure of the gas inside it, and the temperature and pressure of the surrounding air. ALF regulation should be carried out using systems integrated into the central control post, along with engine control units and other devices. It is assumed that the pressure in the gas cylinders will be increased, or the gas will be heated (cooled) or transferred for storage in special cylinders. The problem of ALF control becomes especially significant when creating cargo airships, whose crews must vary the lift force depending on the mass of the cargo taken on board.
However, these methods limit maneuverability and worsen the flight characteristics of Zeppelins, and the water ballast used in the 1920s is unacceptable in low-temperature conditions. The conclusion is clear: the search for a more perfect method of ALF regulation remains as relevant as before.
Another equally important issue is related to ensuring the stability and controllability of airships in flight. In this regard, things are somewhat better, as airship designers can benefit from the experience of creators of VTOL (Vertical Take-Off and Landing) aircraft. Zeppelins, like VTOL aircraft, have to operate in two modes: flying like a conventional airplane and hovering when their ground speed is zero, and the wind effect is countered by the engines. The latter mode is used during assembly operations, mooring, and entry and exit from hangars. But in these cases, particularly powerful, and therefore heavy and fuel-consuming, engines are needed to keep the airship in place. This will inevitably force designers to increase the size of the airship, which will, in turn, increase its cost and worsen its characteristics.
In conclusion, a few words about the theory of aeronautics. In the last four decades, aerodynamics specialists have mainly studied the processes that occur when air flows around objects moving at sonic and supersonic speeds. However, an airship moves relatively slowly, but due to its size, the flow around it is characterized by high Reynolds numbers. It turns out that the results of shipbuilders' research can be useful here. The Zeppelin, "floating" — for lack of a better term — in the air ocean, is in many ways similar to a ship, especially a submarine. It is no coincidence that K. Fedyaevsky, one of our leading aerodynamicists, dedicated the last years of his scientific career to the theory of hydrodynamics and ship controllability. The fact is that when studying the forces acting on the long massive body of an airship, the issues of unsteady flow around the body in conditions of strong turbulence play a significant role.
Drawing a parallel between air and ocean ships, it should be noted that shipbuilders reassessed the strength calculations of ship hulls after a series of severe catastrophes involving the first supertankers. It turned out that during their construction, situations were not considered where a super-long ship could hang with its bow and stern ends on the crests of two waves and break in half. The history of aeronautics includes many similar cases — two-hundred-meter Zeppelins, caught in the zone of powerful air currents, crashed. However, these tragedies occurred with airships in the 1920s-30s, and with supertankers two decades later...
Of course, the development and improvement of strength theory and the use of computers in calculations will allow much more accurate determination of the stresses arising in the elements of the steel structure of lighter-than-air airships. However, here too, there is the inevitable "but": specialists will have to find a favorable ratio of the minimal weight of the Zeppelin (otherwise it won't lift anything but itself) with the necessary strength of its structure. It is important to remember that the enormous "Akron" and "Macon" perished due to the destruction of their structures.
Nevertheless, the above examples and problems mainly relate to airships of the classic shape, whose cigar-shaped bodies represented elongated rotational bodies. Speaking of recent projects, judging by the available information, there is now, and presumably not by chance, the development of airships in the form of discs (see the illustration on the cover of page 1), which Ferdinand Zeppelin would probably classify as "non-airships." However, such apparatuses are capable of creating aerodynamic lift at small angles of attack and are believed by specialists to be less susceptible to the impact of destructive air currents.
VLADIMIR UCHVATOV,
Candidate of Technical Sciences, Dolgoprudny, Moscow Region
In the top photo: a novelty from half a century ago — a mobile mast installed on a car.