Sperry flying bomb

Even before the outbreak of World War I, the idea of ​​air weapons controlled without the participation of a pilot attracted the attention of designers. In 1849, the Austrians tried to use Venetian- style balloons to bombard Venice , firing in the direction of the wind toward the besieged city and dropping incendiary and explosive ordnance onto it. The attempt as a whole was unsuccessful, but the idea of ​​creating an unmanned aerial vehicle for hitting enemy targets continued to develop.

In 1910, an American engineer Elmer A. Sperry , who worked on gyroscopic systems for warships, suggested using a rotating gyroscope to automatically control a flying airplane. He hoped that by adapting marine gyroscopic compasses to an airplane, it would be possible to achieve a stable flight without human intervention. The fleet became interested in Sperry's proposal and in 1913 conducted a series of experiments with the gyroscopic stabilization of a conventional seaplane .

In 1914, when war broke out in Europe, Elmer Sperry and his son Lawrence watched the first attempts to use military aircraft. Returning to America, Sperry, together with the inventor proposed in 1916 to the attention of the fleet a detailed project of an “air torpedo”. Sperry suggested launching an “air torpedo” from the side of the ship or from the water in the direction of the enemy’s warships - the device was supposed to fly at low altitude, automatically holding the course and at the estimated time, go into planning, hitting the enemy ship aboard or into the superstructure. The proposal aroused considerable interest of the Navy and the Bureau of Ordance , under the direction of Lieutenant T. S. Wilkinson, studied in detail the project and the autopilot prototype presented by the designers. The Commission considered that the system does not provide the accuracy necessary to hit even a stationary ship (not to mention maneuvering), but it is of some interest in terms of the possibility of bombing coastal targets. Relations between the United States and the Central Powers were constantly deteriorating, the likelihood of the United States joining the war was quite high, and the Navy was extremely interested in creating new weapons that could provide advantages in this already overturned all the old doctrines and assumptions of the war.

When the United States declared war on Germany in 1917, Sperry, supported by the Navy Advisory Council, sent his proposal to the Secretary for Naval Affairs, asking for $ 50,000 for design work. The idea was so interesting to the senators that the government without hesitation approved the development of even two types of flying bombs - radio-controlled and another, completely unmanned. May 17, 1917, the Navy Secretariat agreed to allocate 200 thousand dollars for the experiments, and the Navy provided five flying boats for experiments with autopilot.

Autopilot experiments began in September 1917. Hydroplanes equipped with autopilot showed themselves as a whole, quite well. The accuracy of reaching a given point with a deviation of 3.2 km at a range of 50 km was demonstrated. The fleet considered these experiments successful enough to order a batch of six samples of "flying bombs" at Curtiss immediately after the tests.

The Sperry Flying Bomb was a fairly large solid - wood biplane , with a trellised tail and a pulling two-bladed propeller . It was driven by a piston engine , with a horsepower of 100 horsepower. With a wingspan of about 7.6 meters and a mass of 680 kilograms, the "bomb" could fly at a speed of up to 145 km / h over a distance of 80 kilometers.

An explosive charge of about 450 kg (1,000 pounds) was to be placed in the body of the “flying bomb”. The bomb was controlled using two mechanical gyroscopes: one stabilized the bomb in flight (roll), the other kept it on a given course. To adjust the flight altitude, the bomb was equipped with a barometric altimeter , previously set (before launch) to a certain fixed value.

It should be noted that no preliminary blowing of the models in the wind tunnel or other activities characteristic of the aircraft development stage was performed.

The first attempt to launch a "bomb" was made in November 1917. To start it, Sperry originally used the bomb suspension on a long cable stretched between the posts. The bomb slid along a cable that sloped down the hill and, having gained sufficient speed, disconnected from it. In November-December 1917, three launch attempts were made, but all of them were unsuccessful, mainly due to problems with the launch mechanism.

Rejecting the cable, Sperry decided to return to the previously proposed (but rejected in favor of a "simple" solution) gravitational catapult. Now the "bombs" were to be launched from a railroad carriage moving along rails 46 meters long with a cable pulled through a mechanical transmission with a three-ton load falling from a nine-meter tower. Several practical tests showed the operability of such a system, but the attempt to launch, in fact, the “bomb” again failed: at launch, the device jumped off the cart, caught on the rail and damaged the propeller.

Finally, after lengthy experiments, in January 1918, Sperry managed to lift the “bomb” into the air. But the flight lasted only a few seconds: the bomb lost control and fell. It became clear that without a manned test it was impossible to work out the mechanism, two samples of the bomb were equipped with a pilot's seat and primitive control devices, which Sperry decided to control. One of these samples crashed immediately after the start (the inventor was not injured), but the second managed to make a manned flight over a short distance.

Deciding to work out the aerodynamics and the bomb control system, Sperry mounted it on the body of car. On a flat track, the car accelerated to 130 kilometers per hour and the incoming air flow interacted with the aerodynamic planes of the “bomb” in much the same way as in the case of a real flight. Using this test platform, Sperry managed to solve a number of problems with adjusting the autopilot, and ultimately, on March 6, 1918, it was from the accelerated Marmon that the bomb was launched on its first successful flight. During this test, the projectile stably flew 910 meters, becoming the first unmanned vehicle to make a controlled flight.

Sperry continued to test flying bombs until September 1918, when all manufactured shells were finally used up as a result of accidents. The fleet did not allocate money for the production of a new batch, not satisfied with the results. Sperry had to return to the experiments with the modernized N-9 flying boats, and in October one of them (with mounted autopilot) was lifted into the air without a pilot on board. The autopilot worked perfectly, stabilizing the car in the air, but the timer device, which was supposed to direct the flying boat down after reaching the estimated distance of 12800 meters, did not work. N-9 continued to fly at a given course, until it disappeared from view over the ocean.

After the war ended, the fleet, however, retained interest in the program. Financing of the project continued until 1922, but the inability of the then automation to provide a fully stable flight led to the fact that the project was eventually closed.

Source: Werrell, Kenneth P. The Evolution of the Cruise Missile . - Maxwell Air Force Base, Alabama: Air University Press, 1985 .-- P. 235 - 289 p.

• Wingspan - 7620 mm (25 ft)
• Length - 4572 mm (15 ft)
• The weight of the warhead - 453.6 kg (1000 pounds)
• Engine make - OX-5
• Engine power - 100 Amer. h.p.
• Marching speed - 145 km / h (90 mph)

• Werrell, Kenneth P. The Evolution of the Cruise Missile . - Maxwell Air Force Base, Alabama: Air University Press, 1985 .-- 289 p.
• Laurence R. Newcome. Unmanned Aviation: A Brief History of Unmanned Aerial Vehicles. - American Institute of Aeronautics and Astronautics, 2004. - 172 p. - ISBN 1563476444 .