Intensive experiments began in late January 1957 at the Nevada Test Site. All the tests were conducted by the Sandia Laboratory of Albuquerque. The tests determined the adequacy of safety controls, handling procedures and stability. The field tests assured that. rigging had been devised which would hold the balloons and prevent their escape, They assured also that a deflation system, devised to lower the balloon quickly whenever necessary, such as during high winds, was satisfactory. The safety device burns a large hole in the top of the balloon so the helium inside the balloon can escape rapidly. This causes the balloon to come down immediately, Balloon tests have been made under many conditions, such as in high winds and thunderstorms, and because of such experiments, the Test Organization has expressed confidence that there will be no difficulty in controlling the balloons during actual detonations of nuclear devices conducted with balloons, Two balloon sizes are being used during Plumbbob. One type is 67 feet in diameter and the other 75 feet in diameter. The smaller balloon will lift a one-ton device to 1,500 feet and still have enough lift to provide control. The larger balloon will lift about two or two-and-a-half tons to the same altitude and still provide — sufficient lift for control. The shot balloons are anchored with four cables, including a main vertical cable and three guy cables, all operated by remotely controlled winches located in heavily shielded underground bunkers, Operation of the cables is from the Control Point where an operator sits at a console with buttons for pulling in or letting out the cables, The operator has before him two television screens which picture the balloon's precise location through the use of two television cameras located on the ground near the balloon. The control cables have dynamometers to relay to the operator the amount of tension on each cable, Maneuvering the cables helps prevent the balloon from moving. If any one of the cables should break because of high winds or other strain, the operator first would attempt to operate and lower the balloon by manual control. Should this system fail, the operator can activate an automatic deflation device at the console in the Control Point. Should neither of these systems work for any reason, a barometric device would activate the deflation system at a certain altitude should the balloon escape, Should the barometric system fail, the balloon automatically will split its seams and descend when it redéhes 5,000 feet over ground level. Because a balloon moves somewhat even in slight winds, recording devices such as cameras and collimators have been re-designed to obtain adequate scientific data during balloon-borne nuclear tests. Some instrument recordings will be carried by cable to underground bunkers. Balloons are used for tests not requiring the precise positioning for which towers are necessary. Detonation from a balloon, because it can be flown higher than the top of any tower used so far, will significantly reduce the amount of surface materials drawn into fe. the radioactive cloud and later deposited as nearby fallout. The r] - 45 - van \ (\