This invention relates to the aerially transporting of loads between sites and more particularly, to the transporting of such loads using a lift balloon.
The concept of aerially transporting loads such as logs with lift balloons is well known. Balloons provide a great amount of lift at relatively low cost and can be maneuvered to hover over a loading or discharging site.
A recent example of a method for aerially transporting loads between loading and discharging sites by balloons is disclosed in U.S. Pat. No. 4,055,316 to Chipper et al. There, the lift balloon is guided between the sites by an aerial cable. The balloon contains a liquid ballast container that can be filled with ballast to maintain the proper buoyancy of the balloon. At the loading site, liquid ballast is ejected in an amount corresponding to the weight of the load to be suspended from the balloon. Upon return to the load discharging site, liquid ballast is replaced in the ballast container and the load is removed from the balloon.
One drawback of Chipper et al. and other conventional balloons is the aerodynamic drag their pear shape creates. Specially shaped balloons may be formed to reduce this drag, such as shown in U.S. Pat. No. 3,369,673 to Mosher, but these balloons cost considerably more than conventional balloons.
Another drawback is the difficulty of maintaining the proper buoyancy of the balloon with the added weight of the load. Chipper et al. compensates by ejecting a corresponding amount of ballast. But this ballast is then lost and must be replaced by additional ballast. However, replacement may be impractical under conditions where water is not readily available, such as in remote logging areas.