facility of the U.S. Naval Ordnance Test Station, Pasadena, California. Ten assemblies were dropped into the water at various angles and with various modifications. Ths first eight tests were carried out by dropping the assemblies from a height of approximately 32 feet at angles of 75° and 90° with the breathe hole left open. Other tests included drops of nose sections attached to parachutes from 100 feet, free-fall drops with the breathe hole closed, and parachute drops with a naoprene boot on the forward seal of the nose sections. The last six tests used sections in which a vacuum (23 inches of mercury), similar to the near-vacuum of the upper atmosphere, had been induced. Examination of these assemblies after recovery showed that the vacuum remained when the breathe hole was sealed. Twenty-seven tests using ten nose section assemblies were conducted over a 5-day period. This work, plus further testing at the Cooper Development Corporation plant, indicated that certain points around the forward ball-seal joint and the operating mechanism were susceptible to small leaks when the presaure difference between the interior and exterior of the diffuser~filter section increased. The neoprene boot, which covered the operating mechanism, had proved to be particularly vulnerable during the EPG firings and later tests. The reliability of the seal was increased a great deal by redesign of the boot, and only infrequent minute leaks were observed after installation of the improved boots. These leaks were repaired as they occurred, until the seal was tight enough to hold a pressure difference of 23 inches of mercury for 10 minutes. Following the successful drop tests, two flight test rounds were fired at the Naval Missile Center (NMC), Point Mugu, California, 24 July. The nose sections for these rounds were modified to incorporate the improvements which had been made during tae tests at Morris Dam. All programer function times were as planned, and both rounds were judged to be successful. Their trajectories were followed throughout the flights by range radar, enabling the impact points to be quickly located by radars on the search aircraft. The nose sections were then recovered by a rescue craft. One of them was completely dry, and the second contained only a few milliliters of water. When the sections were disassembled, it was observed that the dry one had maintained a partial vacuum, while the other had apparently leaked air to equalize the pressure. In spite of the success of the flight tests, it was felt that still further improvements could be made in sealing the diffuser-filter assembly. A conference was held in August between Cooper and UCRL personnelto investigate new approaches to the problem. After study of the design, it was concluded that moving the forward ball-seal O-ring from the forward to aft side of the ball would eliminate several possible sources of leakage, al- though there would be some sacrifice of performance. Slight leakage had been observed during some of the tests at the rubber boot on the push-pull rod, around the nose cap cable entries, and at the forward nose cap blowoff joint. Relocation of the O-ring to a position aft of these areas was expected to prevent any water that might enter from reaching the filter. Allchanges in design that had been made at the EPG and later, including the relocation of the O-ring, were incorporated in a new set of drawings, and two new hose sections were manufactured to the revised drawings. A new antenna system, consisting of two bent dipoles located on opposite sides of the nose section and positioned as far forward as possible so that they would be above the surface of the water, was devised for the recovery transmitter. This system was tested at Puddingstone Dam near Pomona, California, 20 November. The antenna was first submerged, then the nose section was allowed to float during the test. Readable signals were received as far as § miles away with both ground and aircraft receivers. The sig- nal was both stronger and steadier than that produced by the antennas used on the EPG rounds. 57