Engineering topics
Publications and source records attributed to Babel, H. W..
This viewgraph report presents an examination of the fracture toughness of aluminum-lithium alloy C458 for use in cryotank structures. Topics cover include: cryogenics, alloy composition, strengthing precipitates in C458, cryogenic fracture toughness improvements, design of experiments for measuring aging optimization of C458 plate and effects of aging of properties of C458 plate.
A large portion of the space based applications in the near future are for low Earth orbit (LEO) including the Space Station Freedom (SSF). The lifetime needs for materials on the SSF is 30 years. Materials must be selected which can withstand the deleterious effects of LEO. Environmental effects in the LEO include atomic oxygen, UV, ionizing radiation, and hypervelocity impact. These effects can adversely affect the surface properties of materials. This is particularly critical in the case of thermal control materials where the efficiency of the thermal control is dependent on the stability of the surface properties. The current baseline thermal coating for the SSF radiators is Ag Teflon. The surface property requirements for the coatings are a solar absorptance of 0.2 and an infrared emittance of 0.8. The effects of atomic oxygen and UV radiation on the baseline coating and several other candidate thermal control materials were studied. The thermal control radiator materials included Ag and Al backed Teflon, H2SO4 anodized Al, sputter deposited SiO2 on Al, and Ag and Al backed polychloro trifluoroethylene. The simulation of several of the LEO environment constituents provided a data base to aid in the selection of the radiator thermal control material to meet the life requirements of the SSF. The effects are illustrated of the environment on thermal control coatings and the importance of this factor in the selection process for long life spacecraft materials.
Viewgraphs on welding/brazing for space station repair are presented. Topics covered include: fabrication and repair candidates; debris penetration of module panel; welded repair patch; mechanical assembly of utility fluid line; space station utility systems; Soviet aerospace fabrication - an overview; and processes under consideration.
Tests were performed on candidate graphite yarns for the overwraps to be used on the Space Station Freedom's pressure vessels. The objective was to determine the performance and ranking of these overwraps to ensure that sustained loads would not be a problem during their 30-yr life in space. Tests were conducted at high stress levels for short time periods on subscale composite bottles. The average delivered fiber stresses were determined from the measured burst pressures via SCI analysis that accounts for both geometry and the properties of the resin and yarn.
The relationship between analysis, design, fabrication, and testing of thin shells is illustrated by Saturn S-IVB, Thor, Delta, and other single-use and reusable large-size cryogenic aluminum tankage. The analyses and design to meet the design requirements are reviewed and include consideration of fracture control, general instability, and other failure modes. The effect of research and development testing on the structure is indicated. It is shown how fabrication and nondestructive and acceptance testing constrain the design. Finally, qualification testing is reviewed to illustrate the extent of testing used to develop the Saturn S-IVB.