Directory of U.S. Military Rockets and Missiles
Copyright © 2002 Andreas Parsch

Space Data PWN-8 Loki Datasonde

In the early 1960s, the low-cost Loki-Dart sounding rockets (PWN-1, PWN-5) could only carry a passive chaff payload to high altitude. For more sophisticated payloads like temperature transmitters, the USAF had to use the significantly more expensive Arcas (PWN-6 Kitty) rocket. The Space Data Corporation (SDC) was founded in 1963 with the goal to develop a meteorological instrument package small enough to fit into the 3.5 cm (1.38 in) diameter darts of the Loki-Dart systems.

SDC designed an instrument package which would be released from the dart at high altitude and descend slowly below a square metalized mylar parachute structure called "starute". A circuit with a thermistor (temperature-sensitive resistor) would continually transmit temperature data to the ground station. Altitude information was obtained by tracking the descending starute by radar. The rocket motor of SDC's Loki-Dart was based on the Rocket Power Inc. "Judi-1" design, and assembled by Aero Dyne Corporation. Because the original Loki-Dart was only marginally stable in the motor burnout phase, SDC built slightly heavier darts, which decreased the apogee by about 3000 m (10000 ft) but significantly enhanced the stability, and therefore reliability, of the system. SDC's instrumented Loki-Dart was qualified for production in 1966, and more than 20000 units were built until production ceased in 1985.

Drawing: Morrow/Pines
Instrumented Loki-Dart (PWN-8)

The initial Air Force variant of the instrumented Loki-Dart was the PWN-8A, but the main USAF version was the PWN-8B. Because it was significantly cheaper than the PWN-6 Kitty (Arcas), the PWN-8B quickly replaced the latter for many every-day routine applications. The PWN-8B itself was eventually replaced in USAF service in the early 1970s by the larger Super Loki family (PWN-10, PWN-11, PWN-12) of sounding rockets. SDC marketed the rocket as the Loki Datasonde®, which is sometimes referred to as PWN-8D. This is an unofficial designation, with the D suffix possibly chosen to mean "Datasonde".


Note: Data given by several sources show slight variations. Figures given below may therefore be inaccurate!

Data for PWN-8B:

Length (incl. booster)2.95 m (9 ft 8.3 in); dart: 1.24 m (49 in)
DiameterBooster: 7.62 cm (3 in); dart: 3.49 cm (1.375 in)
Finspan13.7 cm (5.4 in)
Weight (incl. booster)15 kg (33 lb); dart: 4.3 kg (9.5 lb)
Ceiling60 km (37 miles; 200000 ft)
PropulsionAero Dyne SR71-AD-1 solid-fuel rocket; 9.55 kN (2150 lb) for 1.9 s

Main Sources

[1] Richard B. Morrow, Mitchell S. Pines: "Small Sounding Rockets", Small Rocket Press, 2000
[2] "DOD 4120.15-L: Model Designation of Military Aerospace Vehicles", Department of Defense, 1974

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Last Updated: 21 October 2002