Beautiful certificate from the Acoustica Associates, Inc.
issued in 1963. This historic document was printed by the De La Rue Banknote Company and has an ornate border around it with a vignette of an eagle. This item has the signatures of the Company’s President, Robert L. Rod and Secretary, Stuart Marks and is over 49 years old.
Control by Sound - Time magazine
Monday, Aug. 03, 1959
When U.S. rocket engineers talk about the bright possibilities of solid-fuel rockets, they always have to pause over one big requirement: how to control the fuel's burning rate. A current system is to shape the charge, measure the ingredients—and hope. This week Acoustica Associates, Inc.
of Plainview, N.Y. announced an initial $85,188 contract with the National Aeronautics and Space Administration to explore a radical new control that is as exciting as it is simple. The company thinks that it can handle solid fuels by filling the rocket with sound—plain, ordinary noise.
Acoustica engineers explain that when a solid fuel burns in a high-pressure combustion chamber, the components, e.g., ammonium perchlorate and polystyrene, turn to gases that mix in a thin layer on its surface. Part of the heat generated strikes back to the fuel, gasifies more of it, and so keeps the flame burning. When this characteristic was discovered by Dr. Martin Summerfield of Princeton, the next step was to look for something that would control the gas mixture. A faster mixing would increase the burning rate, while slower mixing would decrease it. If the control were precise enough, scientists would then have what amounts to a throttle for solid fuels.
Hole in the Middle. Sound waves can perform the trick. When they pass through the reaction layer, they jostle the gases, make them mix and react either faster or slower, depending on the level of sound.
When they reach the hardware stage, Acoustica's engineers will build an experimental rocket engine with a cylindrical cavity running through the mass of fuel (see diagram). A "grain"' of this shape is simple and strong, but if left alone it burns at an uneven rate: as the fuel is consumed, the cavity gets bigger and exposes more surface to the heat. Since the amount of hot gas generated is proportional to the area of burning fuel, the gas pressure keeps rising until just before burnout. The effect is that solid-fuel rockets of this type must have superstrong casings to hold the peak pressure, and must thus pay a penalty in weight.
Acoustica's idea is to control the fuel by blowing high-pressure gas through a heat-resistant whistle at the forward end of the cylinder's cavity. While the cavity is still small, the whistle will screech at full power, increasing the burning rate of the fuel. As the cavity grows bigger, a valve will reduce the amount of gas passing through the whistle. The volume of sound will decrease, and so will the fuel's burning rate. If the valve is manipulated efficiently by some pressure-sensing instrument, it will keep the hot gas inside the rocket at constant pressure from take-off to burnout. Rocket walls can be made lighter, and the bird itself will fly higher.
And a Fiddle on Top. Building a lightweight, sound-controlled rocket will not be easy. But Acoustica's engineers think that it is certainly possible. For a sound-making device, they intend to use a Levavasseur whistle that has no moving parts and can be made of heat-resistant material. The rocketeers figure that the best frequency to use is 10,000 cycles, about the pitch of a very high violin note. Yet the volume of sound must be well above the loudest fiddle; an ear-shattering 170 decibels, which is 100 times the sound pressure of a supersonic boom from a jet aircraft.
Ultrasonics: Unheard Progress - Time Magazine
Monday, Mar. 16, 1959
For years ultrasonics meant something only to dogs and other subhuman creatures. One of the few uses of ultra-high sound waves was in whistles, too high-pitched for human ears, to call pets. Today ultrasonics is an exciting new technological frontier. Last year the ultrasonics industry's commercial and military sales reached $25 million, and in 1959 they are expected to double. Last week industry experts estimated that within five years there will be a $150 million annual market for ultrasonic* equipment.
Ultrasonic machines are used for hospital and industrial cleaning and degreasing. They can join metals previously impossible to weld or solder, drill square and other odd-shaped holes in brittle materials, such as germanium and glass. They will measure any liquid, including exotic jet fuels, and liquid oxygen in rockets. The aircraft, electronic and missile makers have been a major spur to the growth of ultrasonics. Before the development of ultrasonic cleaners, jet-engine nozzles and oil filters had to be thrown away when dirty. Now imbedded residue can be removed in minutes through the use of sound energy. The sound waves whip the water into millions of microscopic bubbles which burst against the material, ripping dirt away. No transistor core goes to its final assembly package without an ultrasonic bath to remove impurities.
Whistle at Work. Sheffield Corp., subsidiary of Bendix Aviation Corp., has just unveiled a tool for machining brittle material that combines eight ultrasonic machines into one unit. Gulton Industries of Metuchen, N.J. will bring out a new line of cleaners, standardize the manufacture of its drills and welders to meet demands of the expanding market. Acoustica Associates, Mineola, L.I., last week demonstrated a new "ultrasonic dipstick" that continuously gauges the levels of virtually any liquid.
Aggressive Acoustica is an example of how fast an ultrasonics firm can grow. In 1955 Acoustica's young (now 38) President Robert L. Rod set up shop in a boathouse, landed six contracts for some $8,000 worth of ultrasonic cleaners. Since then, Acoustica's sales have increased, on the average, six times every year. For the fiscal year ended last Feb. 28, sales hit $4,750,000, with earnings of 50˘ per share, v. 8˘ in 1957. Stock issued at $1 per share in 1956 was selling around $25 per share last week. To boost earnings this year, Bob Rod is counting on new ideas. Among them: an ultrasonic whistle that will increase or decrease the rate at which solid fuel in missiles burns, control its thrust. (Sound waves shot through a material accelerate many chemical reactions, including combustion.)
Cleaning Up. Most profitable area of ultrasonics thus far is cleaning, where the field is divided between small companies such as Acoustica and Gulton and diversified big ones such as Bendix, Curtiss-Wright Corp. and Detrex Chemical Industries of Detroit. Detrex, the largest U.S. maker of dry-cleaning equipment, last year sold $1,250,000 worth of ultrasonic cleaners for electric shavers, auto-engine parts, outboard motors, jewelry and the tips of ballpoint pens. One cleaner washes a cash register with 5,000 parts in 7˝ minutes. Says Detrex's Chief Engineer T. J. Kearny: "Some day we'll be cleaning clothes with ultrasonic equipment."