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Sunday, February 03, 2008

Sunday Ship History: Putting Radar on Ships

It's 9pm on September 8, 1923 and a U.S. Navy destroyer squadron is at sea off Honda Point, California:
Just over twelve hours earlier Destroyer Squadron ELEVEN left San Francisco Bay and formed up for a morning of combat maneuvers. In an important test of engineering efficiency, this was followed by a twenty-knot run south, including a night passage through the Santa Barbara Channel. In late afternoon the fourteen destroyers fell into column formation, led by their flagship, USS Delphy. Poor visibility ensured that squadron commander Captain Edward H. Watson and two other experienced navigators on board Delphy had to work largely by the time-honored, if imprecise, technique of dead reckoning. Soundings could not be taken at twenty knots, but they checked their chartwork against bearings obtained from the radio direction
finding (RDF) station at Point Arguello, a few miles south of Honda. At the time they expected to turn into the Channel, the Point Arguello station reported they were still to the northward. However, RDF was still new and not completely trusted, so this information was discounted, and DesRon 11 was ordered to turn eastward, with each ship following Delphy.

However, the Squadron was actually several miles north, and further east, than Delphy's navigators believed. It was very dark, and almost immediately the ships entered a dense fog. About five minutes after making her turn, Delphy slammed into the Honda shore and stuck fast. A few hundred yards astern, USS S.P. Lee saw the flagship's sudden stop and turned sharply to port, but quickly struck the hidden coast to the north of Delphy. Following her, USS Young had no time to turn before she ripped her hull open on submerged rocks, came to a stop just south of Delphy and rapidly turned over on her starboard side. The next two destroyers in line, Woodbury and Nicholas, turned right and left respectively, but also hit the rocks. Steaming behind them, USS Farragut backed away with relatively minor damage, USS Fuller piled up near Woodbury, USS Percival and Somers both narrowly evaded the catastrophe, but USS Chauncey tried to rescue the men clinging to the capsized Young and herself went aground nearby. The last four destroyers, Kennedy, Paul Hamilton, Stoddert and Thompson successfully turned clear of the coast and were unharmed. In the
darkness and fog enveloping the seven stranded ships, several hundred crewmen were suddenly thrown into a battle for survival against crashing waves and a hostile shore.
Today, such an event is most unlikely, thanks to the development of radar for ships. A WWII training manual stated: "RADAR -- synthetic word meaning Radio Direction And Ranging -- is an electronic device which locates ships and planes in darkness, fog, or storm. It has many military applications and has been effective in many battles of this war." To which we might add, in that war, all wars since and in thousands of non-military applications.

Radar as we know it today was the evolutionary product of great minds, ranging from Heinrich Hertz, the "discoverer" of radio waves, to Christian Huelsmeyer:
On the 30th April 1904, Christian Huelsmeyer in Duesseldorf, Germany, applied for a patent for his 'telemobiloscope' which was a transmitter-receiver system for detecting distant metallic objects by means of electrical waves. The telemobiloscope was designed as an anti-collision device for ships and it worked well. His interest in collision prevention arose after observing the grief of a mother whose son was killed when two ships collided. After a period teaching in Bremen, where he had the opportunity of repeating Hertz's experiments, he joined Siemens. In 1902 he moved to Duesseldorf to concentrate on his invention. He became acquainted with a merchant from Cologne, was given 5,000 marks and founded the company 'Telemobiloscop-Gesellschaft Huelsmeyer und Mannheim'. The first public demonstration of his 'telemobiloscope' took place on the 18th May 1904 at the Hohenzollern Bridge, Cologne. As a ship on the river approached, one could hear a bell ringing. The ringing ceased only when the ship changed direction and left the beam of his 'telemobiloscope'. All tests carried out gave positive results. The press and public opinion were very favorable. However, neither the naval authorities nor industry showed interest. In June 1904 he was given the opportunity by the director of a Dutch shipping company to display his equipment at various shipping congresses at Rotterdam. His was detecting ships at ranges up to 3,000 m, and he was planning a new 'telemobiloscope' which would function up to 10,000 m. He received a fourth patent on the 11th November 1904 in England.
From this primitive beginning, inventors began to pursue better technology.

Modern radar owes much to the U.S. Navy's Naval Research Laboratory:
From 1934 to 1936, experiments by the Naval Research Laboratory, NRL, were being carried out by Robert M. Page. In 1935, he and a small group of scientists at NRL began testing a 60 MHz pulsed radar to detect aircraft. However, pulses from the high powered transmitter caused "ringing" in the receivers, which swamped the echo signals returning from objects nearby.By 1936, NRL engineers had built a 28 MHz pulsed radar which detected aircraft 10 miles away. By the end of 1936, a new radar operating at 80 MHz was detecting aircraft 38 miles away. And in Dec. 1938, a 200 MHz
XAF radar was tested on the USS New York and it detected aircraft up to 100 miles away. The Radio Corporation of America, RCA, worked closely with NRL. Hollmann's patent disclosures filed in the US for such systems as pulsed radar circuits, ring oscillator multiple push-pull tuned-grid tuned-anode, split-anode magnetron, Barkhausen-Kuerz oscillator and antenna duplexer were used.The new model CXAM radar, developed after the XAF unit, worked on 400 MHz (l=75 cm), was put into production. RCA built and delivered 20 CXAM sets in 1940. These sets were installed on the battleships California, Texas, Pennsylvania, West Virginia, North Carolina and Washington, on aircraft carriers Yorktown, Lexington, Saratoga, Ranger, Enterprise and Wasp, on 5 heavy cruisers, 2 light cruisers, and the seaplane tender Curtis. The CXAM performed well during WWII.

The battleship New York was not the first U.S. Navy ship to test radar:

Before radar came along the art of stationkeeping in maneuvers and convoys was a very intricate and hazardous problem. In 1937, a 200-mc radar set was tested at sea on USS Leary (DD-158). Two years later, USS New York (BB-34), while she was in a fleet problem in the Carribean at night, tested a greatly improved 200-mc radar set. A group of destroyers (without radar) were attempting a torpedo run on a line of battleships. All ships were in darkness. Aboard New York a group of men in air plot were intently peering at a small flourescent screen when a slightly higher hump appeared in the jagged green line wavering across the screen. They let the "hump" come to 5,000 yards, trained a searchlight in its direction, illuminated, and picked off the oncoming destroyer. Radar had come to life. Upon the Radioman's shoulders fell the brunt of keeping up sound and radar equipment. Operators of this equipment (Soundmen and radar operators, then) were usually Yeomen, Storekeepers, or Seamen, who, if they could distinguish between a "ping" and a "pong" were awarded five extra dollars a month. Communications responsibilities increased and Radiomen couldn't be spared to keep up extra equipment, so in 1943, there were two more ratings established, Radarman and Sonarman.
More here:
In April 1937, Leary became the first United States naval vessel to be equipped with search radar, which was installed by the Naval Research Laboratory.

In September 1939 destroyers Leary and Hamilton (DD-141) established a continuous antisubmarine patrol off the lower New England coast. The following year her patrol functions enlarged and 9 September 1941 she began a series of hazardous escort missions to Iceland. On 19 November Leary became the first American ship to make radar contact with a U-boat. After 26 February 1942 she spent a year escorting convoys from the midocean meeting point to various Icelandic ports.
How does radar work?
The principle upon which radar operates is simple. Briefly, it consists of sending out a short pulse of radio energy and receiving a portion of the same energy reflected back by objects in its path.

The energy sent out by a radar set is the same as that transmitted by ordinary radio. But unlike an ordinary radio set a radar set literally picks up its own signals. Thus the radar set transmits a short pulse of energy, receives its echoes, then transmits another pulse and receives its echoes. This out-and-back cycle is repeated from 60 to 5000 times a second.

The extremely short time interval between the sending of the pulse and the reception of its echoes can be measured very accurately--even to one ten-millionth of a second. Since the speed at which the radio energy travels is known (it is the same as that of light) the range of any reflecting object can be obtained.

Furthermore, the transmitted energy is focussed in a beam which can be pointed in any chosen direction. Hence the bearing of a reflecting object is also obtained.
Radar for navigation? Well, you can get a "picture" of land masses:
ACTUAL-SIZE PHOTOGRAPH of a radar "scope," taken in a plane flying over Nantucket Island. Circle on scope marks 10-mile radius. Note correspondence with geodetic chart (insert.)

ACTUAL-SIZE PHOTOGRAPH of a radar "scope," taken in a plane flying over Nantucket Island. Circle on scope marks 10-mile radius. Note correspondence with geodetic chart (insert.)

THIS PHOTOGRAPH ILLUSTRATES the clear definition between land and water provided by radar, as well as the sort of picture presented on one type of radar scope. Such definition, of course, is useful as an aid in navigation of planes and ships, in observing the movements of ships and convoys, in detecting targets at night, in shelling or bombing enemy vessels or coastal targets, or in mapping work.

This PPI scope has a flourescent screen so made that the signals from reflecting objects will persist for a few moments. Other types of scopes are shown on the following pages, illustrating some of the chief uses of radar. For most of these functions, several radar sets are now available. Details of design, operation and performance of specific sets are listed later in the book.
It's hard to imagine the Point Honda disaster occurring if the destroyer navigators had had sucha clear picture of the danger they were standing into.

Radar on ships - a perfect fit.

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