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Hewitt-Sperry Automatic Airplane – First Ever Cruise Missile

A month before the last flight of the Hewitt-Sperry automatic aeroplane its creator, the brilliant Elmer Sperry, would boldly and prophetically claim it to be the “gun of the future”.

Sperry was not entirely wrong when he proclaimed this just a couple of months before the project was cancelled, for his invention is widely regarded as the precursor to the cruise missile that has defined the modern battlefield since the second half of the 20th century.


Elmer Sperry

In 1907 American inventor Elmer Ambrose Sperry began investigating how gyroscopes could improve the accuracy of long-range guns on US Navy ships.

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A device that was able to overcome the pull of the earth’s rotation and maintain true direction via the principles of angular stability, Sperry’s maritime application of this invention, which had been known about since the mid-18th century, was an unqualified success and led to the foundation of the Sperry Gyroscope Company in 1910.

Elmer Sperry.
Elmer Sperry.

Following this, Sperry began to wonder if the same system could be used in powered flight, recently discovered by the Wright Brothers in 1903, since aeroplanes like ships were also inherently unstable. Sperry himself described the problem:

“When aviation was in its infancy the pioneer airplanes were acting not unlike a bucking bronco which refuses to acknowledge the right of man to master it. Those early planes would nose dive and generally refuse to obey the desires of pilots. There was a heavy toll of human life.”

Eager to prove his theory had merit in spring 1914 Sperry, accompanied by his son and test pilot Lawrence, travelled to France with a gyroscopically enhanced aeroplane to enter into a competition organized by the French government, which was offering a prize of 50,000 francs if a stable aircraft could be demonstrated.

Blowing away all the other contestants Sperry’s contraption emerged victorious. The judges were particularly impressed by the way Lawrence had flown by them stood up and with both hands raised, a stunt that had convinced them that this was indeed a new form of automatic stabilization.

Early Experiments

Sperry’s success in France and the outbreak of World War One only a month later would set the stage for his next major project: an automatic pilotless flying bomb.

In 1915 American inventor Dr Peter Cooper Hewitt suggested to Sperry that a flying machine installed with gyroscopic stabilizers could be the basis for a radio-controlled unmanned missile, that could potentially assist the Allies in their struggle against a belligerent Imperial Germany.

Agreeing wholeheartedly, and procuring 3,000 dollars from Hewitt as well as a Curtiss flying boat and a new azimuth gyroscope, Sperry began experimenting in secret, later moving his laboratory to a small village on Long Island called Amityville so it was away from prying eyes.

On the hunt for a benefactor, Sperry’s letters to the US Army remained unanswered, but it would be the Navy who were to prove more forthcoming.

On September 12th 1916 from the passengers’ vantage point of a Navy N-9 hydroplane, lieutenant Commander T.S. Wilkinson Junior would witness a dress rehearsal of the procedure by which an aeroplane could be transformed into an airborne torpedo.

Sperry used the N-9 Seaplane for testing.
The Curtiss N-9 Seaplane that was initially used for testing.

After lifting off from the water with the assistance of a pilot (who would be eventually removed later down the developmental line), the plane would next reach a predetermined altitude via automatic gyroscopic control before either releasing a bomb or descending onto the target itself in the style of a World War Two kamikaze fighter.

Wilkinson remarked that a major weakness was that the plane was not accurate and that it was impossible to alter its direction mid-course, making it useless against enemy battleships which could simply move away to dodge it.

Alternatively, he recommended it could be more effectively used by the US Army against stationary targets.

The Army however continued to be uninterested, and following a major crash with the flying boat in November 1916, the project was all but abandoned.

Project Revival

On the other hand, Sperry’s project would receive a wave of renewed interest following the American entry into World War One on April 6th 1917. Following a meeting of the Naval Consulting Board in New York City on April 14th, the aerial torpedo was allocated an additional 50,000 dollars in funding, a sum that was later increased to 200,000 dollars.

Given five N-9 seaplanes to conduct tests, in June 1917 the project was officially restarted at Amityville with the US Navy hoping to eventually use flying bombs, which could carry one and half times more ordnance than water missiles, to disable stationary German submarines docked at German bases at Wilhelmshaven, Cuxhaven, and Helgoland.

By September 1917 flight trials were once again underway. A typical evaluation started with a pilot getting the craft airborne before switching on the gyroscope to enable automatic control.

Operating by itself on a predetermined flight path, the pilot would observe the aircraft as it dropped a sandbag acting as a bomb, after which automatic controls were disengaged and switched over to manual for touchdown.

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During this first stage, Sperry focused on making the ‘distance gear’ used to jettison the bomb as accurate as possible. Following several refinements to the equipment, by November targets up to 30 miles away could be consistently hit.

The next goal was to make his invention truly automatic by ensuring it could work without any pilot assistance. For this Sperry required a test bed that was smaller, faster, and most importantly cheaper, and which would resemble the finished product.

With the N-9 navy planes having reached the limit of their usefulness, Sperry next ordered 5 ‘Speed Scout type’ aircraft from Glenn Curtiss and authorized by rear Admiral  Ralph Earle on September 29th, but with an average cost of 14,000 dollars for each one (10,000 for an engine-equipped unit and 4000 for the Sperry controllers) the cost-effectiveness was well below Navy expectations.

Nevertheless with the war intensifying in Europe plans were given the go-ahead, and on November 10th 1917 the first ‘aerial torpedo’ was delivered to the US Navy a mere 3 weeks after approval, after which it would undergo its first unmanned evaluation.

Developments and Setbacks

In an omen of what was to come for several months, the first unmanned flight test on November 24th 1917 went disastrously wrong after the aerial missile tipped to one side, cutting the 400-foot cable of the catapult that was to launch it into the air and falling 30 feet off the raised platform.

What followed was a series of failures in which the aerial torpedo was wrecked and repaired a further three times without even getting airborne.

Gliding smoothly down the support cables, January 14th 1918 witnessed the first successful launch attempt, but when the craft was flung into the air it went into an overly steep climb, assuming an upright position before swinging sharply to left, stalling, and plummeting spectacularly to the ground where it was obliterated on impact.

With doubts about the very airworthiness of the missile creeping in, and efforts to get it to take off from the smooth, runway-like surface of a nearby frozen lake also coming to nought, the practicality of Sperry’s invention began to be questioned.

However, with the installation of a pilot’s seat and a brief return to manned test flights, Sperry was able to figure out what was going wrong.

A technical mismatch between the Curtiss airframe design and the Sperry controller was part of the problem, while a fundamental structural flaw, a lack of longitudinal balance, was identified after a particularly terrifying flight in which the aerial missile with Lawrence Sperry strapped inside was overturned two times, with the pilot afterwards noting how he had had to exert excessive force on the elevators to stop it from crashing. 

A handful of technical tweaks resulted in the first successful US cruise missile flight on March 6th 1918. After being catapulted smoothly from the launch pad, the flying bomb had travelled in a straight line up to the 1000-yard point when, as programmed, the distance mechanism had cut the engines, allowing the craft to lose altitude steadily before hitting the surface of the lake.

The RAE Larynx ready to be fired.
A much later attempt in the mid 20s, the RAE Larynx cruise missile was created and to be used as an anti ship weapon.

But the air missile was unable to repeat the results in succeeding examinations, compelling Sperry to rethink his entire evaluation method since it was very difficult to discover the issues with no pilot onboard to observe them.

Cancellation of the Sperry Missile

Sperry’s solution was to build an entirely new testing apparatus by attaching the torpedo to an automobile in order to recreate the conditions of flight on land and to allow assessors to make real-time evaluations. 

Fitting a Marmon automobile with an eight-cylinder OX-5 aircraft engine so it could reach the desired speed and exceed its usual 45 to 50 mile-per-hour limit, the torpedo was fastened onto an overhead frame while a courageous driver sped down a highway at 80 miles per hour with an engineer assessing performance once terminal velocity was reached.

With the Marmon now installed with railway wheels, Sperry next changed the testing site to an unused five-mile stretch of railway, where on one particularly perilous occasion both the aerial torpedo and the modified automobile momentarily lifted off the tracks because of lift generated under the wings.

With Sperry resorting to increasingly wild and harebrained schemes, Navy observer Benjamin B. McCormick, who had demonstrated incredible patience and optimism throughout the process, now wrote to his superior that he was: “strongly in favour of closing up these experiments at the earliest possible date.”

After briefly experimenting with an alternative launch apparatus through August and September 1918 known as the Norden Catapult launcher, which involved pulling a platform fastened with the missile down railway tracks with the assistance of a large flywheel, and failing at every turn, the signing of the November Armistice between the Allied and Central Powers would finally put an end to Sperry’s project.

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Having destroyed all of the available airframes, and with the coming of world peace decreasing the immediate need for new weapon technologies, the aerial torpedo project was officially cancelled on January 31st 1919. Although ultimately a failure, Sperry and the US Navy’s partnership would amount to humanity’s earliest exploration of cruise missiles, which would revolutionize modern warfare in the decades after World War Two.