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FLYING at altitude intensifies most problems, simplifies some, the author shows. Increasing operating altitude from 25,000 ft to well into the stratosphere lowers temperature more than 50 F, and reduces pressure to one-fifth the sea-level value. This complicates structural problems. It affects the hydraulic and control systems, electrical systems, cooling, and air conditioning, and increases the danger from failure of any of these essentials. Gusts and turbulence, on the other hand, are lessened by flying high. The author charts the extent of each of the problems, and shows how altitude economy gains make solutions imperative.

THIS PAPER presents the development of the DC-8 suppressor and thrust brake unit from initial test work through the final design. The selection of the production unit was based on a wide background of test work using both model and full-scale facilities. On the basis of this work, the configuration selected for production consisted of a fixed, corrugated, suppressing nozzle with a retractable ejector. A target-type thrust brake, mounted in the ejector, was chosen for the thrust brake production unit. Approximately 12-db suppression and 44% reverse thrust are provided by the unit. The ejector is hydraulically operated and the thrust brake air actuated. Both actuation systems obtain power from the aircraft systems which provides for operation during engine-out conditions. Alternate methods of actuation are provided in case of a primary system failure.

Because of the rapid growth of air travel, both cargo and passenger, the payload capacity required for future transport aircraft is too great to be accommodated by fuselages of conventional configuration (that is, single-deck, single-aisle, up to 6 seats abreast). Fuselage design philosophy was therefore re-evaluated in a recent Douglas study, and this paper reviews some of the features of that study. Factors affecting fuselage design are outlined and trends are discussed. It is concluded that the forthcoming wide, single-deck fuselage, seating up to 10 abreast, will have a potential capacity of about 550 passengers. For larger capacities, the greater efficiency of multi-deck fuselages over that of the single-deck becomes increasingly apparent on a per-passenger basis. The use of multi-deck fuselages, however, will raise new problems-particularly those of airport terminal design and passenger evacuation-but these should not prove insurmountable.

The S-IV and S-IVB stages for the Saturn vehicles were designed to utilize the high specific impulse of the liquid hydrogen - liquid oxygen propulsion system. The use of liquid hydrogen presented special structural problems that led to the development of the reinforced foam internal insulation and the sandwiched honeycomb common bulkhead. The major design problem in each case was the high thermal stress resulting from the steep thermal gradient across the depth of the structure. For the extreme temperatures involved the thermal stresses were very high and were dominant factors in establishing the designs.