Investigation of a Towed-Capsule Installation of the AN/ASH-2 Condensation Nuclei Detector
Abstract
The AN/ASH-2 condensation nuclei detector was developed for use in naval aircraft for detecting invisible, persistent trails of exhaust products from submarines operating under diesel power. Air to be examined is drawn from the outside atmosphere by a pump and passed over a water-saturated wick to increase its humidity to nearly 100%. It then passes into a black, baffled expansion chamber in which the pressure is suddenly reduced; this produces a sudden decrease in temperature, supersaturation of the air and, if condensation nuclei (such as fragments of hydrocarbon molecules) are present, a water droplet surrounding each nucleus. The number of water droplets in the resulting cloud is "counted" by measuring the amount of light from an external incandescent source that is forward-scattered through the chamber and detected by a multiplier phototube. Five air samples are examined per second. The amplified output of the phototube is displayed as a continuous line on a strip chart recorder. The device is amazingly sensitive, being capable of detecting as few as 50 condensation nuclei relative to 2.7E19 molecules of air per cubic centimeter. A representative exhaust trail may exist as a "ribbon" about 2000 ft wide and 300-600 ft thick at an altitude up to 600 ft at a range of about 5 nmi downwind of a snorkelling submarine, depending upon the wind and the temperature lapse rate. The purpose of these tests was to investigate possible advantages that might accrue from towing the AN/ASH-2 behind and below the aircraft. One set was installed in an NADC HTM-9 towed capsule (which was developed for use with magnetic anomaly detectors) and a reference set was installed in the towing P2V-7 aircraft. Flight tests were conducted on 21 Mar 1957 and on 5 and 18 June 1958. Exhaust trails were recorded from a cargo ship consistently on both equipments at ranges of 3.5 to 40 nmi. On 31 crossings of the trail of a snorkelling submarine at ranges out to 15 nmi, the inboard equipment...
Document Details
- Document Type
- Technical Report
- Publication Date
- Mar 24, 1959
- Accession Number
- ADB966296
Entities
People
- Paul M. Moser
Organizations
- Naval Air Warfare Center Warminster