A large percentage of conventional operational losses and severe damage incidents have occurred in lighter than air vehicles as a result of high winds, turbulence, and heavy precipitation, while the lighter than air vehicle was moored on a fixed or mobile mooring mast. The nose cone structure on a lighter than air vehicle serves two purposes: 1) it is used to fasten the lighter than air vehicle to the mooring mast and 2) it serves as a nose stiffening device to prevent the nose from dimpling inward due to the dynamic pressure (Q force) of the wind at high air speed.
The development of tethered aerostats, which are made of strong, lightweight fabrics, which can withstand significantly greater internal pressure than conventional lighter than air vehicles, have brought a new dimension to lighter-than-air operation. Since the internal pressure of the tethered aerostat may be increased as the wind forces increase, the need for nose stiffening to prevent cave-in of the aerostat no longer exists. Tethered aerostats also must be moored in such a way to react to the large excess lift with which aerostats operate compared to other lighter than air vehicles. Still further, aerostats are inherently designed to be operated and maintained totally outdoors in all weather, without access to hangars, contrary to other lighter than air vehicles. As a result, the nose structures on aerostats have been designed to be more robust so that aerostats can survive a much more hostile weather environment.
When lighter than air vehicles are moored, it is necessary to transfer the mooring loads from the hull fabric to the mooring tower. These loads are caused primarily by variations in wind direction and velocity. Lighter than air vehicle nose structures are designed to withstand steady state winds of at least 90 knots at ground level and enable the aerostat to survive in severe thunderstorms and frontal weather passages, while the aerostat is moored.
Previous lighter than air vehicle nose structure designs have used two basis approaches:
1. A large cone shaped truss structure with long curved battens have traditionally been used for over 20 years on large lighter than air vehicles, as illustrated in FIG. 1. These cone-shaped truss structures are very heavy and expensive to manufacture; and
2. A soft nose system which includes cable guy lines and a nose mooring probe on the vehicle which mates with the large cone structure on the mooring tower, as illustrated in FIG. 2. This requires a very large and expensive cone shaped structure on the mooring system. Further, this design is not as efficient as the FIG. 1 system in reacting mooring forces. However, it is extremely successful on lighter than air vehicles which operate in benign weather environments.
The present invention is directed to an improved lightweight nose cone assembly for lighter than air vehicles, and specifically for airships and aerostats, with equal or better strength performance than the cone and batten design illustrated in FIG. 1, but of a construction weight approaching that of the system illustrated in FIG. 2. The improved lightweight nose cone assembly for lighter than air vehicles of the present application comprises a welded metal truss and guy lines for attaching the lighter than air vehicle to its mooring tower or mast. The use of this new assembly results in substantial savings in weight and cost and is more efficient than the existing hard nose structures with battens. Further, the improved lightweight nose cone assembly for lighter than air vehicles of the present application greatly simplifies vehicle installation and inflation.