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.
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| Photo: National Weather Service |
| Arcas (PWN-6) |
The Arcas was powered by a relatively low-thrust slow-burning SR45-AR-1 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 an LAU-41/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.
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| Photo: National Weather Service |
| Arcas (PWN-6) |
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.
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| Photo: via Morrow/Pines |
| Arcas (PWN-6) |
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.
Boosted Arcas
The Arcas was also used as second stage in two-stage sounding rockets. For use as an upper stage, the Arcas was modified to the HV Arcas (High-Velocity Arcas) configuration, with larger fins, no boat-tail, and structural modifications to withstand the high initial acceleration of the booster.
Sparrow-HV Arcas
The Sparrow-HV Arcas rocket was originally developed in 1964 for the Pacific Missile Range's DENPRO (Density Probe) program. A second goal was to build a smaller and simpler replacement for the then widely-used Nike-Cajun sounding rocket without sacrifcing performance.
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| Photo: Lt.Col. Roy F. Houchin II, via Morrow/Pines |
| Sparrow-HV Arcas |
The booster stage of the Sparrow-HV Arcas was a MK 6 MOD 3 storable liquid-propellant motor of the AIM-7D Sparrow missile. The rocket could carry payloads of 4.5-13.6 kg (10-30 lb) and could reach altitudes of about 170 km (105 miles). Apart from at least 10 DENPRO flights in 1964, the Sparrow-HV Arcas was also used for other measurements in the mesosphere and lower ionosphere by the U.S. Air Force and Navy. Including non-military users, a total of about 50 of these rockets were launched.
Sidewinder-HV Arcas
The Sidewinder-HV Arcas was developed in 1965 by the Naval Missile Center, Pt. Mugu, and was designed to support the Gemini space program with high-altitude meteorological data. The first stage was a MK 17 MOD 1A solid-propellant rocket motor of AIM-9B Sidewinder missiles. The vehicle was fired from standard rail launchers which were available at most launch sites at that time.
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| Photo: Betty Flowers, via Morrow/Pines |
| Sidewinder-HV Arcas |
Sidewinder-HV Arcas rockets were launched by both the U.S. Air Force and Navy, but data on the number and scope of the military launches is not available. All users combined, a total of about 80 of these sounding rockets were launched in the late 1960s.
Specifications
Note: Data given by several sources show slight variations. Figures given below may therefore be inaccurate!
Data for PWN-6A/B, Sparrow-HV Arcas, Sidewinder-HV Arcas:
| PWN-6A/B | Sparrow-HV Arcas | |
|---|---|---|
| Length | 2.32 m (7 ft 7.2 in) | 3.84 m (12 ft 7.1 in) |
| Diameter | 11.4 cm (4.5 in) | 1st stage: 20.3 cm (8 in) 2nd stage: 11.4 cm (4.5 in) |
| Finspan | 33 cm (13 in) | 1st stage: 81 cm (32 in) 2nd stage: 33 cm (13 in) |
| Weight | 66 kg (146 lb) | 99 kg (218 lb) |
| Speed | 3950 km/h (2455 mph) | 6035 km/h (3750 mph) |
| Ceiling | 60 km (37 miles; 200000 ft) | 170 km (105 miles) |
| Propulsion | ARC SR45-AR-1; 1.5 kN (336 lb) for 29 s | 1st stage: Thiokol MK 6 MOD 3; 34.7 kN (7800 lb) for 2 s 2nd stage: ARC SR45-AR-1; 1.4 kN (324 lb) for 29 s |
| Sidewinder-HV Arcas | |
|---|---|
| Length | 4.31 m (14 ft 1.6 in) |
| Diameter | 1st stage: 12.7 cm (5 in) 2nd stage: 11.4 cm (4.5 in) |
| Finspan | 1st stage: 53 cm (20.8 in) 2nd stage: 33 cm (13 in) |
| Weight | 88 kg (195 lb) |
| Speed | 4940 km/h (3070 mph) |
| Ceiling | 115 km (72 miles) |
| Propulsion | 1st stage: Thiokol MK 17 MOD 1A; 17.7 kN (3970 lb) for 2.1 s 2nd stage: ARC SR45-AR-1; 1.4 kN (324 lb) for 29 s |
Main Sources
[1] Richard B. Morrow, Mitchell S. Pines: "Small Sounding Rockets", Small Rocket Press, 2000
[2] Peter Alway: "Rockets of the World", Saturn Press, 1999
[3] "Model Designation of Military Aircraft, Rockets and Guided Missiles", Department of Defense, 1970
[4] ORDATA Online Website
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Last Updated: 22 December 2005