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: 8/11/1953 at 17:09 utc
Launch site: USS Staten Island (AGB-5)  
Balloon launched by: General Mills Inc.
Balloon manufacturer/size/composition: Zero Pressure Balloon General Mills -- 68 foot
Flight identification number: GMI-1024
Landing site: Payload no recoverable

The purpose of the flight was to obtain data on the physical properties of the Arctic upper atmosphere. Measuring stagnation and ambient pressure, along with the trajectory were sufficient to determine the pressure density, and temperature profiles. Stagnation pressures at the nose probe-tip were measured by a 0-250 mm Hg differential pressure bellow gauge. For ambient pressure measurements, holes located 7 calibres from the probe-tip maintained an ambient pressure chamber in the nose of the rocket while the pressure below 100 microns was measured by a Pirani gauge, located 7 calibres back from the rocket nose. Additionally a thermometer measured the Pirani gauge-case temperature, an accelerometer measured rocket-propellant burning-time and a 25-mm Hg pressure switch started the ambient pressure compressor and a data commutator. The data were telemetered by a two-channel FM-FM, 300-milliwat transmitter.

The balloon was launched on August 11th, 1953 at 15:09 utc, from the deck of the U.S Coast Guard vessel Staten Island sailing at coordinates 74º34'N - 94º29'W. After reaching float altitude of 70.300 feet, the rocket was fired by the activation of the onboard pressure switch at 18:28 utc. The rocket reached an apogee of 50.2 miles.

External references

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