The prime requirement of the space and missile industry is for reliability in components. Many of these components represent conventional articles used by engineers over a long period of time, and it is necessary to stop and review the developments which have affected changes in these articles. From water pipe to helium hydraulic lines in missiles is a long step. But, so also is the change from cast iron to vacuum-melted stainless steel. These changes in application and in basic material find a counterpart in the development of quality in tubular products, although this development has been given less recognition.
Tubing is a critical part in hydraulic systems and must measure up to the requirements for higher strength, lighter weight and great reliability. The beneficial weight-strength ratio of steel tubing was recognized in the aircraft industry forty years ago by the transition from wood to metal tubular frame construction - with doped-cotton skin. World War II saw tremendous strides in airplane construction, both by numbers and by size. The actuation of airplane components was extended from pedal and cable, to complex hydraulic systems requiring special quality tubing. The change from aircraft to astrocraft calls for still further upgrading in quality.
The aeronautical engineer must be informed of the latest materials available for his selection. These materials can best be defined by their capabilities and limitations, with respect to tolerances of dimensions, quality and mechanical properties. This paper will attempt to up-date some of the technical information which the engineer normally seeks in the handbooks.