Basic theory and pilot experiments to the problem of triggering lightning discharges by rockets

The objective of this contract was to determine the feasibility of discharging electrified clouds with triggered lightning. As a first step towards this goal, the conditions have been calculated under which lightning may be triggered by different types of rockets. For instance the breakdown field value is reached at the tip of the Apollo-Saturn V rocket in a cloud field of about 10 kV/m, whereas a cloud field of about 125 kV/m is necessary to produce breakdown field at the folding fin aircraft rocket Mighty Mouse tipped with a trigger sphere of about 3.5 cm radius. The field concentration factor n at the tip of the rocket which augments the external cloud field to the field at the rocket tip is a function of the ratio of the length of the' rocket a to the radius of curvature at the tip p. In the case of the Apollo rocket, a/p = 1000 and in the case of the Mighty Mouse rocket, a/p = 34, with a = 120 cm and p = 3.5 cm. To simulate the Apollo by the Mighty Mouse rocket, it is necessary either to increase the length a or decrease the radius of curvature p of the Mighty Mouse rocket in such a way that a/p = 1000. This leads to a = 35 m or p = 1.2 mm. It is shown in section 1.4 that the length a may be further reduced to about 26 m. The radius of curvature p determines the type of discharge. For p>2 cm the discharge will be in the form of a spark and for p<2 cm in the form of corona discharge. The corona current is a function of the electric field strength. Using the corona current on a sharp needle as a field indicator, an instrument has been designed (measuring payboard) which can be attached to the Mighty Mouse rocket [L. H. Ruhnke, 1971]. This instrument measures and transmits to ground the electric field values along the rocket path.