Biggest Tunnel

The taxpayers got a look last week at the gigantic new wind tunnel (cost: $33 million) at the propulsion laboratory of the National Advisory Committee for Aeronautics at Cleveland. It has been abuilding since 1952, and so far as the Western world knows, it is the most powerful in operation. Engines up to 5 ft. in diameter can be tested in its 10 ft.-by-10 ft. throat, fed with air rushing past at Mach 3.5 (1,800 m.p.h.). To move so much air at this speed requires monstrous fans that soak up 250,000 h.p.

When a passive model is being tested, the air in the tunnel is sent around a circuit and used repeatedly, but jet engines or ram-jets poison the air with their exhaust gases. New air must be taken from the atmosphere, and its excess moisture eliminated. So the tunnel is provided with a monstrous air dryer stocked with 1,890 tons of activated alumina, which soaks up 1.5 tons (ten bathtubs) of water per minute. On a muggy day the alumina has to be dried out after two hours, and this takes enough gas burners to keep the whole city of Berea, Ohio (pop. 13,200) warm in winter. The air in the tunnel must be cooled, and the job is done by cooling apparatus equivalent to 250,000 household air conditioners.

An important part of the new tunnel is an automatic system for making sense out of the flood of information that streams from it. Eighty thousand separate measurements may be made in a single day. The figures are first put on magnetic tape, then worked over by an electronic computer that reduces them quickly to curves and tables. In old-style wind-tunnel setups, most of this job was done by hand and often took several weeks.

Many a Clevelander was apprehensive while the new tunnel was under construction. Lesser tunnels at the same site jangled nerves with their dreadful racket. This tunnel has an enormous muffler in which even the loudest sounds get lost. A screaming siren can be carried into the muffler and become inaudible in a few yards. When the tunnel is in operation, its noise is reduced to levels acceptable at least to N.A.C.A.'s hardened neighbors. The tunnel works-late at night only, so its inordinate thirst for electricity will not slow the city of Cleveland (pop. 935,000).

This file is automatically generated by a robot program, so reader's discretion is required.