"chaff, "rope", and other radar contermeasures in box
Date: circa 1944
Inventory Number: 1997-1-0796c
Classification: Radar Counter-Measure
Subject:
Maker: Reynolds Metal Company (1919 - 2000)
Maker: Radio Research Laboratory (1942 - 1946)
Associate Name: Fred L. Whipple (1906 - 2004)
Cultural Region:
Place of Origin:
Dimensions:
box: 16 × 33 × 32 cm (6 5/16 × 13 × 12 5/8 in.)
Accessories: see Description for itemized list
DescriptionA large cardboard box packed with different samples of radar countermeasures in individual packets. The inscriptions on the packaging appear to be the results of experimentation during their development at Harvard.
Most of the packets contain "chaff", thin strips of foil folded at a right angle lengthwise. Most of the chaff packages contain a type that has bare aluminum on one side and a thin paper coating on the other side. The triangular packs (see below) contain chaff that is entirely made of foil).
There are also packets of "rope" longer strips of paper coated with metal along its thin edges.
There is also one large device, possibly a decoy, consisting of a retractile, kite-like structure of metal rods with pale gold metal foil attached between them. The structure can be folded to fit into a cardboard tube.
There are also packets with rolls of metal foil about 1cm width, which may have been also used as countermeasures or as raw material for making them.
There is also a roll of unprocessed metal foil.
The box also contains three inscribed sheets of paper, and an s-shaped aluminum rod and toothed wheel that were part (perhaps a crank) of a larger machine.
***
Listed below are the different types of packs, their contents, and inscriptions:
- 1 circular roll of chaff. inscribed: I-B-1 4000 CHA3
- 3 flat packs of chaff, of 2 different lengths.
(longer): CHA-2 / 107.2 gr. gross / Average of 2: 109.3gr = 0.241#
shorter #1 inscribed: Average gross wt of 10 units = 74.8 gr /3 / Wt of wrapper = 21.8 " / Average net wt per unit = 53 grams / Wt of 300 dipoles (?) 77 " / [illegible] Tin Foil + [illegible] / / CHA-3 Thin Sliced [?] Width .043 / Average No. of dipoles per inch [unit?] = 53/7/7 x 300 = 9x300 = 2100.
shorter #2 inscribed: Reynolds / CHA 3 / gross wt 80.8 gr / average of 2: / 79.6 gr / Wrapper = 24.2 gr / Nt Wt. 55.4 gr = 0.122 lbs / Present products / May 1st, 1944.
23 additional flat bundles of chaff (as ones above) of same length, unmarked.
1 long bundle with square/pentagonal cross-section. Inside, large retractile device, probably a decoy or antenna. Five metal rods attached to same metal block arranged with one central rod and four others unfold via spring mechanism. pale gold colored metal foil extends between each of the lateral rods and the central ones, sail-wise. FRAGILE foil!
1 bundle with rectangular cross section, unmarked. inside, containing very short chaff (ca 2 inches long).
8 triangular bundles of chaff of 2 different lengths, chaff made of metal only (no paper). bunched together with cardboard straps.
16 additional triangular bundles (shorter length), in sets of four linked with cardboard straps. chaff made of metal only.
5 additional triangular bundles (longer length) in one set of five. chaff made of metal only.
2 long paper cylinders containing stack of rolls of aluminum tape ca 1cm width.
1 long paper cylinder containing unprocessed roll of aluminum sheet
2 aluminum cylindrical shells containing densely packed chaff ca 2 inches long, kept together by brass rings.
bundle of two rolls of aluminum tape ca 1cm wide. one by itself, other packed in cardboard box and wrapped in paper.
9 rectangular bundles containing long thin strips of paper, ca 70cm in length. The paper has been coated with metal along its thin edge.
s-shaped aluminum rod and an aluminum toothed wheel that connect together, maybe used to be a crank for a machine
yellow mailing receipt handwritten with pencil on back: [torn off]2064 / [David Wheatland's Address] / Signature
letter sized paper, typewritten: "WINDOW" / CHAFF CUTTER / USED TO MANUFACTURE CHAFF / MACIMUM TOTAL PRODUCTION RATE / 7 MILES OF CHAFF PER SECOND / "ROPE" / USED TO KNOCK OUT JAP RADARS / GUN LAYING AND SEARCHLIGHTS / ONE BOMBER LOAD OF CHAFF / ON AVERAGE MISSION EQUALS / 700 DEHYDRATED BOMBERS
handwritten paper note: "Window" was the name given a countermeasure device for the German radar controlled anti-aircraft gun. This "window" consisted of small strips of aluminum foil with a right angle bend down its length which was made first at the "Radio Research Lab" at Harvard and formed and cut on the machine designed by the astronomer F.L. Whipple (of the Observatory).
back of paper note: (header left) GRADUATE SCHOOL OF ARTS AND SCIENCES / PHYSICS // (header right) GRADUATE SCHOOL OF ENGINEERING / COMMUNICATIONS ENGINEERING // (top center) CRUFT LABORATORY / HARVARD UNIVERSITY / CAMBRIDGE, MASSACHUSETTS
Most of the packets contain "chaff", thin strips of foil folded at a right angle lengthwise. Most of the chaff packages contain a type that has bare aluminum on one side and a thin paper coating on the other side. The triangular packs (see below) contain chaff that is entirely made of foil).
There are also packets of "rope" longer strips of paper coated with metal along its thin edges.
There is also one large device, possibly a decoy, consisting of a retractile, kite-like structure of metal rods with pale gold metal foil attached between them. The structure can be folded to fit into a cardboard tube.
There are also packets with rolls of metal foil about 1cm width, which may have been also used as countermeasures or as raw material for making them.
There is also a roll of unprocessed metal foil.
The box also contains three inscribed sheets of paper, and an s-shaped aluminum rod and toothed wheel that were part (perhaps a crank) of a larger machine.
***
Listed below are the different types of packs, their contents, and inscriptions:
- 1 circular roll of chaff. inscribed: I-B-1 4000 CHA3
- 3 flat packs of chaff, of 2 different lengths.
(longer): CHA-2 / 107.2 gr. gross / Average of 2: 109.3gr = 0.241#
shorter #1 inscribed: Average gross wt of 10 units = 74.8 gr /3 / Wt of wrapper = 21.8 " / Average net wt per unit = 53 grams / Wt of 300 dipoles (?) 77 " / [illegible] Tin Foil + [illegible] / / CHA-3 Thin Sliced [?] Width .043 / Average No. of dipoles per inch [unit?] = 53/7/7 x 300 = 9x300 = 2100.
shorter #2 inscribed: Reynolds / CHA 3 / gross wt 80.8 gr / average of 2: / 79.6 gr / Wrapper = 24.2 gr / Nt Wt. 55.4 gr = 0.122 lbs / Present products / May 1st, 1944.
23 additional flat bundles of chaff (as ones above) of same length, unmarked.
1 long bundle with square/pentagonal cross-section. Inside, large retractile device, probably a decoy or antenna. Five metal rods attached to same metal block arranged with one central rod and four others unfold via spring mechanism. pale gold colored metal foil extends between each of the lateral rods and the central ones, sail-wise. FRAGILE foil!
1 bundle with rectangular cross section, unmarked. inside, containing very short chaff (ca 2 inches long).
8 triangular bundles of chaff of 2 different lengths, chaff made of metal only (no paper). bunched together with cardboard straps.
16 additional triangular bundles (shorter length), in sets of four linked with cardboard straps. chaff made of metal only.
5 additional triangular bundles (longer length) in one set of five. chaff made of metal only.
2 long paper cylinders containing stack of rolls of aluminum tape ca 1cm width.
1 long paper cylinder containing unprocessed roll of aluminum sheet
2 aluminum cylindrical shells containing densely packed chaff ca 2 inches long, kept together by brass rings.
bundle of two rolls of aluminum tape ca 1cm wide. one by itself, other packed in cardboard box and wrapped in paper.
9 rectangular bundles containing long thin strips of paper, ca 70cm in length. The paper has been coated with metal along its thin edge.
s-shaped aluminum rod and an aluminum toothed wheel that connect together, maybe used to be a crank for a machine
yellow mailing receipt handwritten with pencil on back: [torn off]2064 / [David Wheatland's Address] / Signature
letter sized paper, typewritten: "WINDOW" / CHAFF CUTTER / USED TO MANUFACTURE CHAFF / MACIMUM TOTAL PRODUCTION RATE / 7 MILES OF CHAFF PER SECOND / "ROPE" / USED TO KNOCK OUT JAP RADARS / GUN LAYING AND SEARCHLIGHTS / ONE BOMBER LOAD OF CHAFF / ON AVERAGE MISSION EQUALS / 700 DEHYDRATED BOMBERS
handwritten paper note: "Window" was the name given a countermeasure device for the German radar controlled anti-aircraft gun. This "window" consisted of small strips of aluminum foil with a right angle bend down its length which was made first at the "Radio Research Lab" at Harvard and formed and cut on the machine designed by the astronomer F.L. Whipple (of the Observatory).
back of paper note: (header left) GRADUATE SCHOOL OF ARTS AND SCIENCES / PHYSICS // (header right) GRADUATE SCHOOL OF ENGINEERING / COMMUNICATIONS ENGINEERING // (top center) CRUFT LABORATORY / HARVARD UNIVERSITY / CAMBRIDGE, MASSACHUSETTS
Signedunsigned
Inscribedsee Description for details of inscriptions on each individual item
FunctionThis box contains several different types of passive radar countermeasures developed at Harvard's Radio Research Laboratory during World War II.
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.
The present box contains chaff of several lengths, from very short 2-inch pieces to about 22-inch pieces. There are also samples of chaff of different materials, some entirely made of metal, and some with paper on one side. The chaff is stored in different forms of packaging which probably reflect different ways of releasing the product from airplanes.
The box also contains samples of "rope", which was the radar countermeasure used when enemy radars emitted at very different wavelengths. "Rope" was more frequently used over Japan. It consists of much longer strips of metal, which would be dropped from airplanes, sometimes in groups attached to parachutes.
Some of the samples of "rope" in the box are rolls of metal foil, while others are long paper tapes coated with metal along their thin edges.
The box also contains a kite-like device, likely some sort of decoy. It can be stored inside a thin tube and unfolds automatically via spring mechanisms at the joints of its aluminum frame when released.
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.
The present box contains chaff of several lengths, from very short 2-inch pieces to about 22-inch pieces. There are also samples of chaff of different materials, some entirely made of metal, and some with paper on one side. The chaff is stored in different forms of packaging which probably reflect different ways of releasing the product from airplanes.
The box also contains samples of "rope", which was the radar countermeasure used when enemy radars emitted at very different wavelengths. "Rope" was more frequently used over Japan. It consists of much longer strips of metal, which would be dropped from airplanes, sometimes in groups attached to parachutes.
Some of the samples of "rope" in the box are rolls of metal foil, while others are long paper tapes coated with metal along their thin edges.
The box also contains a kite-like device, likely some sort of decoy. It can be stored inside a thin tube and unfolds automatically via spring mechanisms at the joints of its aluminum frame when released.
Curatorial RemarksThe Collection has several packages of such materials: 1997-1-0796 (box with radar countermeasures) plus RS0810, RS0811 and RS0812, three triangular bundles of chaff.
ProvenanceProbably from the Cruft Laboratory [Harvard], as one of the notes is written in stationary from that Laboratory, and three chaff bundles catalogued independently (but likely part of this box) are described in database as coming from Cruft.