The First Heat-seeking Missile: Polaroid's Project Dove

Mark Dionne

During World War II, my father, Leonard Dionne and mother, Ruth Sweet Sawyer, both worked at Polaroid Corporation in Cambridge, Massachusetts. They both worked on Project Dove, a U. S. Navy sponsored project to build a bomb that could be dropped from airplanes and "home in" on ships using an electronic guidance system that detected the heat from the ships' engines. It was the first heat-seeking missile. My father worked in the engineering department, making the prototype mechanical parts, and my mother worked in the drafting department. They were married in 1947.

My father kept a box of parts from the project, and as a kid I played around with them. He explained how the guidance system worked. An infrared detector with a gold plated parabolic reflector was mounted on a gyroscopically stabilized gimbal arrangement. Small pre-amplifier circuit modules were mounted on or near the gimbals. These used miniature vacuum tubes and would fit in about a one inch cube. More circuits were in odd shaped metal "cans," roughly 3 by 3 by 8 inches, with the components "potted" in wax, including slightly larger vacuum tubes. The bomb's fins were moved by DC motors driving a long screw. The master control was a clockwork mechanism that turned a shaft with cams operating micro-switches. Since the guidance system was under development, there was also instrumentation to record what happened as the bomb was falling. Information was recorded on a strip of 35mm film. The film was not used photographically: several styluses were arranged to move representing the data, and periodically a solenoid pressed their sharp points into the moving film strip, which then wound into a very thick steel cylinder that was expected to survive the impact. Some of the styluses were connected to simple accelerometers, spring mounted weights with linkages to magnify their movement. They eventually tested the thousand pound bombs by dropping them onto a ship anchored in Boston Harbor, with smudge pots used to simulate the engine heat. The project never went into production because the war ended.

If you have sailed a boat very much, you will understand how the Dove bomb homed in on a moving target. If you are approaching another boat, and the bearing of the other boat (the angle you would need to turn your head to look at the boat) is changing, then you will miss them. If the bearing does not change, then you are on a collision course. In the Dove bomb, the infrared sensor was moved until the signal from the target was maximized. Since it was mounted on a gyroscope, the sensor would stay pointed at the target if the bomb was on a collision course. If the bomb was not on the proper trajectory, the target's image on the sensor would drift, and the sensor would need to be moved to re-center the image. The same movements would be amplified and applied to the steering fins of the bomb, correcting it's path in a feedback loop. When the bomb was "on target" the ship's image would not move on the infrared sensor, and there would be no more adjustment of the bomb's fins. All this was done with vacuum tube circuitry. Going back to the sailing model: if you want to intercept another boat, keep staring directly at the boat. If you need to turn your head to the left, then correct your steering to the left. If you need to turn your head to the right, then correct your steering to the right. (If you are not getting any closer, then speed up.)

The book Insisting on the Impossible: the Life of Edwin Land, by Victor K McElheny, adds more details. Physicist David Grey was the designer and the Navy spent $7 million on the project over several years. The bomb could be dropped from high altitude, avoiding dangerous and inaccurate "dive bombing". The sub-miniature vacuum tubes were originally developed for secret artillery proximity fuses. The heat-sensing thermistor was developed by Bell Labs. The control vanes were on the front of the bomb. Eastman Kodak company may have picked up the project after Polaroid dropped it.

Indeed, there is more history about the bomb here:
The project was renamed ASM-4, ASM-N-4 or XASM-N-4 (ASM stands for Air-Surface Missile). Kodak worked on the project, still named Dove, until 1952. 20 prototypes were built and tested but the missile was never put into service. The Army Air Force had a related project, the ATSC VB-6 Felix bomb, but it too was not ready before the war ended.

My father kept a souvenir from one of the bomb drops. Here is a photo:
[smashed camera parts]

McElheny writes:

To study the relationship between the extension of the vanes... the team installed an eight-millimeter camera in the nose of a dummy bomb. To obtain a very compact, pre-war Keystone home-movie camera, [Dr. Edwin] Land sent a letter to a list of customers provided by Keystone, offering a war-bond to anyone who would contribute a camera to the war effort. Hundreds were sent in.

From an article here.

It was in the beginning of 1945 when Boston came calling. The Navy, in conjunction with Boston's Polaroid Corporation, was conducting trials on a new missile and needed a ship for Project Dove that would be in close proximity to Monomoy Island in Chatham, and the Army base in Wellfleet. On February 22, 1945, the SS James Longstreet was ordered to Cape Cod Bay. She returned to Boston to be outfitted, stripped of all non-essential equipment, and on the morning of April 25, 1945, at 9:46, she was set to rest on New Found Shoal in Cape Cod Bay, just north of the town of Orleans and west of Eastham. According to Sawyer she was the target for the Dove bomb, which was a heat-seeking homing missile that later lead to the modern day Sidewinder missile, but by the following year Project Dove no longer needed the Longstreet. For the next twenty-five years the James Longstreet acted as the target for various bombs, bullets, and rockets from the Army, Navy, and Air Force, damaging her hull and breaking her down. In 1950 its official number had been surrendered by the US Maritime Commission, signaling not only the retirement of the ship, but the ship being official withdrawn from being a vessel of the United States. In 1971, or thereabouts, after she had been used in missile development in the Korean War and Vietnam, all actions were halted. Beyle states that, according to a statement issued by the Navy in 1978, the bombings were stopped due to the close proximity of civilians to the Target Ship, and the shutting down of the one of the major air bases on Cape Cod. After that, the Target Ship was left on her own for the waters of the bay to do with her what they wished.
(more on the SS James Longstreet)

I visited John Lothrop Sept 17, 2010. He is 91

John ran the shops that made all the mechanical prototypes at Polaroid, and he was one of my father's best friends. He lived in Westwood, Massachusetts, and his wife found the house there that my parents bought in 1948

The mechanical work on Dove was done in John's shop, though the shop also was doing other work. This was in part of the Kaplan building, which was also a furniture store [Osborn St]. It was near the famed Alexander Bell laboratory where the first long distance call was made. There were 4-5 men working on the project in his shop, and they were hired by the Navy. (Eventually there were up to 40 people in John's group, mostly working on cameras.) The Navy also supplied all the machinery. There were never more than about a dozen people in the entire project. Everything was very secret.

The first time they dropped a bomb on a ship, it hit the railing and went through the hull. The ship had "about 75 orchard heaters on it, they got them from all over the state." The bomb was meant to detect the heat from the entire deck as it sat in the sunshine, not the heat of the stack or engines. The plane was supposed to fly directly over the ship and release the bomb 250 feet past the ship.

The bombs had 4 fins. Dr. Land was directly involved, at least early in the project. Otto Wolff was chief engineer at Polaroid and led the project.

John gave me several gyroscopes, two were electrically driven and two were air driven. He claimed that the electrically driven ones were the ones used in the bomb, which makes sense. Also gave me an accelerometer exactly like the one I remembered. He also gave me a sensor that might be the one used for the bomb.

Photos of some parts from the protype bomb:
More photos

Copyright 2007 Mark Dionne. All Rights Reserved. This work is based on original research by Mark Dionne. Permission to copy or reprint this work is granted, provided: (1) the copy or reprint is used for non-commercial, educational purposes; (2) the work is copied in its entirety or a single paragraph is used as a quotation, and; (3) the author's name (Mark Dionne), email address, the URL mentioned in the following paragraph, and this notice are all included.

Latest revision: Sept 27, 2010. The master copy of this document resides at Revisions may have been made since this copy was taken. Please refer there for the latest revision.

[mark at mark dionne dot com]