balloon as a detonation platform is very much less expensive thana tower, The principal purpose in using balloon suspension is to decrease nearby fallout, to permit better scheduling by avoiding long weather delays, and to obtain better positioning at higher altitudes than would be possible through air drops which might otherwise be necessary on some shots in the Plumbbob series, but which now are scheduled on balloons, \ Another consideration in the use of balloons is the fact that there is a practical limit to the height of towers for supporting nuclear shot devices, This limit has two factors: (1) The limitation of weight in that it is not (2) A point is reached when it would not be practical to build a 1,500-foot tower, for example, that would support two tons or sa; and, appropriate to use towers because the increased amount of tower material would add materially to the nearby fallout. At a certain altitude, ground material no longer is picked up into the fireball and this is advantageous. However, at some higher point, the increased material vaporized into the fireball from the tower itself offsets the lack of ground material. Balloons solve this problem by providing very little fallout material. The helium in the balloon may be heated by the nuclear reaction during a detonation but there is no other physical effect. ll. SAFETY AND RADIATION PROTECTION As in past series, safeguarding the public health and safety is a primary consideration in the Plumbbob series of nuclear tests. Because of improved controls and procedures, radioactive fall~ out in the area around the Test Site is expected to be even lower than the levels which have resulted from previous tests in Nevada. For the United States as a whole, average exposure will be small in comparison with the radiation dosage normally received from natural "background" radiation. Fallout levels in other parts of the world as a result of the tests generally will be lower than those in the United States, Systems of detecting and measuring fallout radioactivity have been expanded and improved in order to provide more extensive data for scientific purposes and for informing the public. Radiological monitoring will be conducted by several networks of stations extending from the Test Site region to locations around the world, Each test scheduled for Operation Plumbbob has been carefully evaluated to determine that it is necessary for achievement of the overall objective of strengthening the military and civil defense of the United States and the Free World. - 46 -