Loki (rocket)

Development

The Taifun was conceived by Klaus Scheufelen as a simple unguided rocket to be fired en masse into bomber streams, filling a gap while guided missiles were developed. It used a hypergolic mixture pressure-fed into the combustion chamber by small cordite charges that burst diaphragms to release fuel and oxidizer. The engine never worked reliably, and the rocket was not deployed. The US Army studied the Taifun in 1946, and German engineers working for the Army advocated further development.

When similar concerns about guided missile timelines arose, a development program began at Bendix in 1948. A key change replaced the warhead with a dart that separated from the rocket body at burnout to coast to higher altitudes. Bendix struggled with the engine and switched to a solid-fuel design using a new elastomeric fuel from the Jet Propulsion Laboratory, starting in March 1951. The first solid-fuel Loki flew on 22 June 1951, and the liquid engine was abandoned in February 1952.

A meeting on June 25, 1954, at Redstone Arsenal involving Wernher von Braun, Frederick C. Durant, Alexander Satin, David Young, Fred L. Whipple, S. Fred Singer, and Commander George W. Hoover concluded that a Redstone rocket with a Loki cluster as a second stage could place a satellite into a 200-mile orbit without major new developments.

Sounding rockets

In 1955, the United States Navy took many completed Lokis and replaced the explosive warhead with a chaff dispenser, calling them WASP rockets. These were fired from ships to release chaff at apogee for radar wind measurement. The USAF used the Loki in this role as the XRM-82.

The ONR employed the Loki in Rockoon launches, lifting it by balloon before firing. A larger motor with 50% more fuel was developed in 1957, creating the Loki II, with the original retroactively named Loki I. Other versions included the Cooper Development/Marquardt Rocksonde 100 (100,000 ft maximum altitude) and Rocksonde 200 (200,000 ft). The HASP variant was launched from a 5-inch gun barrel, using bore riders on the dart's fins for stabilization and spin, which fell free after exit.

SDC

Space Data Corporation (SDC) formed in 1963 to supply small sounding rockets to defense agencies. They adapted the meteorological rockets with an instrument payload for the Loki, replacing the chaff dispenser. At least three instrument payload variants existed: PWN-10, PWN-11, and PWN-12. These carried a thermistor for temperature, broadcast via a 1680 MHz radio, and altitude was tracked by radar reflecting off a square mylar parachute and radar reflector called a starute, or with the PWN-10 via a ranging transponder.

The SDC version was slightly heavier, reducing maximum altitude by about 10,000 ft. Production of the Loki Datasonde began in 1966, with over 20,000 built until 1985. The Air Force requested a version without radar tracking, leading SDC to add a transponder, enlarge the starute, and develop a larger booster, resulting in the Super Loki, which first flew in 1968 and saw 9,000 delivered. In 1972, SDC completed the Viper IIIA motor, nearly identical to the Super Loki, providing apogees of ~120 km for ROBINSphere payloads to measure wind and atmospheric profiles in the 110–95 km region.

A design change in 1993 replaced the elastomeric solid propellant with HTPB in both the Super Loki and Viper IIIA. Orbital Sciences Corporation bought SDC in 1990, and production of the Super Loki and Viper IIIA continued until 2001.