Aerospace & Aviation

An integrating ionization chamber and a single Geiger counter were flown on United States satellite Explorer VI in an elliptical orbit extending to 48,000 km. In addition to the Van Allen inner zone and the great outer zone, a stable and distinct intermediate zone was detected throughout August and September 1959. The outer-zone intensity showed a large decrease following the sudden commencement of a geomagnetic storm. Later in the storm the outer zone increased to much in excess of its prestorm level. During stable periods the outer zone was fairly constant and less intense than it had been observed to be with Pioneer III or Pioneer IV or the first Soviet cosmic rocket. Cosmic-ray background counting rates were reached on most passes in August and Septmeber near apogee of the satellite. The radiation ?dumped? from the outer zone during the geomagnetic storm fits very well with the intensity and latitude distribution required to account for balloon observations of auroral X rays made during the IGY period. This paper is based on preliminary analysis of Explorer VI data.

In a rocket motor having a de Laval nozzle with a fixed expansion ratio, there is only one pressure ratio (p(sub c)/p(sub o)) for which this expansion ratio is correct. At any other pressure ratio the gases will be either underexpanded or overexpanded, depending on whether the pressure ratio is higher or lower than the correct value. Rocket motor flame patterns illustrating the four possible regimes are shown in Figures 1 to 4, inclusive. In Figure 1, the pressure ratio is higher than the correct one for the fixed expansion ratio of the nozzle, resulting in underexpansion of the gases. in Figure 2, the pressure ratio is the correct one. In Figure 3, the pressure ratio is only slightly lower than the correct one, resulting in overexpansion without separation of the gases from the wall. In Figure 4, the pressure ratio is considerably below the correct one, resulting in overexpansion with separation of the gases from the nozzle wall. The present report is concerned primarily with this fourth type of flow, that is, overexpansion of the gases with separation of the flow from the wall. Such a situation exists in a rocket motor operating at a considerably lower altitude than that for which its exhaust nozzle was designed.