Purpose of the flight and payload description

The so called ROCKOON (Rocket-Balloon) technique allowed small rockets to reach higher altitudes by sending it onboard a stratospheric balloon to an altitude of about 70.000 ft where it was fired either by an onboard timer, a pressure switch or by telecommand. The technique was first used in 1952 by Dr. James Van Allen then working at the State University of Iowa.

The main advantage of the rockoon combination was to let the rocket to pass throught the lower and thicker layers of the atmosphere without using its own propulsion power, which then allowed a higher apogee to be reched. The only setback was that once released, the balloons cannot be steered and consequently the rocket's launch direction nor imapct area can be predicted. Thus, for safety reasons, all the Rockoon missions were conducted from small vessels sailing in open waters. This possed an additional advantage as the ships could move with the wind to create a "zero wind condition" ideal to launch the balloons.

The first rockoon firings used a high-performance small vector known as DEACON. It was a vertically launched sounding rocket developed in 1947 by Allegany Balistics Laboratory for the Navy Bureau of Ordnance, and originally designed to carry a 50-pound instrument load to an altitude of about 20 miles. It had no internal controls or movable surfaces and was arrow stabillized by fins at the after end of the rocket. Propulsion was furnished by a JATO X220 solid propellant rocket motor. Its total length was 12.3 ft, diameter 6.5 inches and fin span was 38.9 inches. The Deacon was capable of attaining speeds about 3.000 mph, and altitudes in excess of 60 miles when fired from a balloon floating around 70.000 ft.

Details of the balloon flight

Balloon launched on: 8/31/1952
Launch site: USCGC Eastwind (WAGB 279) anclado en la Bahia de Baffin entre Groenlandia y el NE de Canada (Lat. 77.33º N - Lon. 72.83º O)
Balloon launched by: General Mills Inc.
Balloon manufacturer/size/composition: Zero Pressure Balloon General Mills - 55 ft
Flight identification number: GMI-961
End of flight (L for landing time, W for last contact, otherwise termination time): 8/31/1952
Landing site: Payload no recoverable

The purpose of this flight was to make an absolute measurement of the total intensity of charged primary cosmic rays down to the lowest feasible value of magnetic rigidity. The scientific payload developed by Robert A. Ellis was located in the nose section of the rocket which was pressurized, approximately conical in shape, detachable and with a volume of about 2.5 cubic feet. It consisted of a spherical ion chamber at the top, followed by a box containing the immediately associated electronics circuits behind the pressure gauge. The next three decks contained batteries, while the lower deck housed the telemetry transmitter. At left can be seen an image of it. A small rocket-firing gondola, containing a timer, barometric pressure switch, and firing batteries, was suspended from the rocket's tail fins by a light cord so that the rocket would break away once it was fired.

The balloon was launched on August 31th, 1952 from the deck of the U.S Coast Guard vessel Eastwind, sailing at coordinates 77º20'N - 72º50'W. After reaching float altitude of 7.8 miles, the rocket was fired succesfully and achieved an apogee of 39.8 miles.

External references

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