361. Actual Mass Property Determinations for the Able Series Space Probes

Paper

Abstract

This paper was presented at the Twenty-first Annual National Conference of the Society of Aeronautical Weight Engineers at Seattle, Washington, May 14-17, 1962. Between August 1958 and December 1960, several multi-stage vehicles were launched from Cape Canaveral. They had various satellite and space probe missions. These vehicles, assembled by Space Technology Laboratories and sponsored by ARPA, the Air Force and NASA, were designated Able 1 through Able 5. They used Thor of Atlas first stages, Aerojet liquid second stages and Allegany Ballistics Laboratory solid third stages. Some of the spacecraft or payloads had propulsion units, others did not.
The flight control techniques and staging methods used in these vehicles required very tight mass property and assembly tolerances. Some of the mass property tolerances were considerably smaller than had been experienced heretofore. (Mass properties in this context include weight, centers of gravity, moments of inertia and principal axes locations.)
This paper examines the program requirements that necessitated actual mass properties tests and discusses how those tests performed by STL were devised and conducted to meet these requirements. No attempt is made here to discuss the overall weight control programs for these vehicles as the subject is too vast.
Particular emphasis is given to methods used for mass property determinations on the upper stages and spacecraft. For some of these tests existing techniques were refined. In other cases, new methods were devised to yield the desired accuracy. The devices used in the determinations are discussed in some detail. Error analyses of the tests are also shown.
The techniques and devices shown here are being refined and used on current space programs such as OGO and Program 698AM. Some are basic and highly accurate and as such should be useful in many future space generations.