A 1957 Stanford Research Institute study proposed a small single-stage sounding rocket to measure winds at 45 km (150,000 ft) to determine the spread of radioactive fallout. The Office of Naval Research and the Air Force Cambridge Research Center awarded Atlantic Research Corporation a contract to develop this sounding rocket in January 1958. ARC designed the Arcas rocket, the first of which was ready for flight tests in late 1958. By the end of 1960, more than 400 Arcas rockets had been launched.
Historical Essay © Andreas Parsch
Atlantic Research PWN-6 Kitty
In early 1957, the Stanford Research Institute presented a study that a small single-stage sounding rocket would be very useful to measure winds at an altitude of up to 45 km (150000 ft) after nuclear tests to determine the spreading of radioactive fallout. The Office of Naval Research (ONR) and the Air Force Cambridge Research Center (AFCRC) concluded that such a system had a general utility as a high-altitude weather probing tool, and awarded Atlantic Research Corporation (ARC) a contract to develop this sounding rocket in January 1958. ARC designed the Arcas rocket, the first of which was ready for flight tests in late 1958. By the end of 1960, more than 400 Arcas rockets had been launched.
The Arcas was powered by a relatively low-thrust slow-burning solid-propellant rocket motor. This caused much less stress on the payload than, say, the very short high-acceleration burn of the contemporary Loki-Dart type sounding rockets (like the PWN-8). It was launched from a tubular closed-breech launcher, which could be adjusted in azimuth and elevation. The rocket was kept centered in the tube by four plastic spacers, which flew free at launch.
Throughout the 1960s, the U.S. Air Force used several different versions of the Arcas. The first one was the PWN-6A Kitty, which carried an AN-DMQ-6 meteorological radiosonde as payload. This radiosonde was ejected at the apogee of the trajectory at about 60 km (200000 ft) and descended slowly on a parachute. It contained a temperature measuring instrument and a telemetry package, which transmitted temperature and air desity data to an AN-GMD-1 or -2 RAWIN (Radar Wind Sounding) ground station. The radar of the RAWIN station was used to get a radar plot of the falling radiosonde's track, which was then used to calculate wind speed and direction. The PWN-6B was identical to the PWN-6A except for an additional transponder. This could be used together with the AN-GMD-2 RAWIN station to get wind speed-direction data directly.
Another Arcas variant used by the USAF was the PWN-7 Rooster with a ROBIN (Rocket Balloon Instrument) falling sphere payload. For many every-day purposes, the PWN-6 was already replaced in the late 1960s by the cheaper instrumented Loki-Dart (PWN-8). In the early 1970s, the Super Loki-Dart sounding rockets (PWN-10, PWN-11, PWN-12) became available, and these finally replaced the Arcas as the USAF's meteorological sounding rocket.Specifications
Note: Data given by several sources show slight variations. Figures given below may therefore be inaccurate!
Data for PWN-6A-B:
|Length||2.30 m (7 ft 6.6 in)|
|Diameter||11.4 cm (4.5 in)|
|Finspan||33 cm (13 in)|
|Weight||34 kg (76 lb)|
|Speed||3950 km-h (2455 mph)|
|Ceiling||60 km (37 miles; 200000 ft)|
|Propulsion||Atlantic Research SR45-AR-1 solid-fuel rocket; 1490 kN (336 lb) for 29 s|
 Richard B. Morrow, Mitchell S. Pines: "Small Sounding Rockets", Small Rocket Press, 2000
 Peter Alway: "Rockets of the World", Saturn Press, 1999
 "Model Designation of Military Aircraft, Rockets and Guided Missiles", Department of Defense, 1970