cutter prototype for "chaff" or "window"
Date: 1941-1942
Inventory Number: 1997-1-0786
Classification: Radar Counter-Measure
Subject:
Inventor: Fred L. Whipple (1906 - 2004)
Associate Name: Kenneth T. Bainbridge (1904 - 1996)
Maker: Radio Research Laboratory (1942 - 1946)
Cultural Region:
Place of Origin:
Dimensions:
17.9 × 45 × 17 cm (7 1/16 × 17 11/16 × 6 11/16 in.)
Description:
A cutting machine encased in a metal frame with a perforated metal sheet cover. The machine has a lawnmower-like interlocking cylinders with sharp angles, and is driven by a large belt wheen on one side.
Wooden block attached to base.
Wooden block attached to base.
Signedunsigned
FunctionThis is a machine that is fed a sheet of metal foil and cuts it into very narrow strips, and bends them at an angle along their length.
The resulting product, called "chaff" in the United States, was a radar countermeasure. See for example 1997-1-0796, RS0810, RS0811 and RS0812).
The resulting product, called "chaff" in the United States, was a radar countermeasure. See for example 1997-1-0796, RS0810, RS0811 and RS0812).
Historical AttributesThis is an early prototype machine to make "chaff", a form of radar countermeasure. It was developed at Harvard's Radio Research Laboratory by the astronomer Fred L. Whipple, work for which he earned the nickname "Chief of Chaff". Kenneth T. Bainbridge had brought the idea of chaff back from Britain as part of an information-sharing trip in early 1941.
During World War II, it was determined independently in Germany and Britain that a piece of metal of half the wavelength of a radar signal reflected a disproportionately large signal. Based on this finding, the radar countermeasure called "window" in Britain and "chaff" in the United States was developed. It consists of strips of metal foil of approximately half the wavelength of enemy radar, which were thrown in large numbers from airplanes. In order to maximize the amount of material, thin strips of aluminum foil were used. These strips were also corrugated bent in a right angle alongside its length so that they maintained their shape in the air. A full load of chaff from a bomber gave off the radar signature of about 700 airplanes. Conversely, clouds of chaff could be used to shield large numbers of airplanes behind it.
In total, 3/4 of the total production of aluminum foil during the war, about 20.000 tons, was used to manufacture chaff.
During World War II, it was determined independently in Germany and Britain that a piece of metal of half the wavelength of a radar signal reflected a disproportionately large signal. Based on this finding, the radar countermeasure called "window" in Britain and "chaff" in the United States was developed. It consists of strips of metal foil of approximately half the wavelength of enemy radar, which were thrown in large numbers from airplanes. In order to maximize the amount of material, thin strips of aluminum foil were used. These strips were also corrugated bent in a right angle alongside its length so that they maintained their shape in the air. A full load of chaff from a bomber gave off the radar signature of about 700 airplanes. Conversely, clouds of chaff could be used to shield large numbers of airplanes behind it.
In total, 3/4 of the total production of aluminum foil during the war, about 20.000 tons, was used to manufacture chaff.
Primary SourcesThe information-sharing trip by Kenneth T. Bainbridge to Britain in early 1941, where he obtained the idea of "chaff", is described in an oral history interview available at the IEEE here.
A good source about countermeasures in general from the period is "Radar Countermeasures", Electronics (January 1946), pg. 92-97. Available online at CECOM Historical Office here.
The Harvard Archives contain the papers of the Radio Research Laboratory. For a Finding Aid, click here.
A good source about countermeasures in general from the period is "Radar Countermeasures", Electronics (January 1946), pg. 92-97. Available online at CECOM Historical Office here.
The Harvard Archives contain the papers of the Radio Research Laboratory. For a Finding Aid, click here.