Investigation of spectral properties of ultraviolet gratings Semiannual status report, 1 Sep. 1967 - 29 Feb. 1968

Space environment simulation experiments on possible electron impact damage to gold replica grating

Numerical Analysis of the Transient Response of Advanced Thermal Protection Systems for Atmospheric Entry

Equations for the transfer of heat through thermal protection shields are derived in finite difference form. These equations are applicable to charring ablators, impregnated ceramics, subliming ablators, heat sinks, and insulating materials and have been programed for solution on a high-speed digital computer. In the program, thermal properties can be functions of temperature. Provision is made for analysis of heat shields subjected to simultaneous convective and radiative heat inputs. Some typical results are presented. Limited comparisons with experimental results are made

One-dimensional numerical analysis of the transient thermal response of multilayer insulative systems

A one-dimensional numerical analysis of the transient thermal response of multilayer insulative systems has been developed. The analysis can determine the temperature distribution through a system consisting of from one to four layers, one of which can be an air gap. Concentrated heat sinks at any interface can be included. The computer program based on the analysis will determine the thickness of a specified layer that will satisfy a temperature limit criterion at any point in the insulative system. The program will also automatically calculate the thickness at several points on a vehicle and determine total system mass

Evaluation of a low-density polyimide foam in a dynamic, high temperature environment

A low density polyimide foam material was tested in an arc tunnel to determine its potential for heat shield application on aerospace vehicles. The results show that the material has some reuse potential at surface temperatures as high as 750 K. When a black refractory paint was applied to the surface of the material, the surface recession was negligible at 750 K. An analytical thermal conductivity was derived for this material which, combined with measured thermal property values, can be used to make preliminary design thickness calculations for heat shield applications

Surface recession characteristics of a cryogenic insulation subjected to arc-tunnel heating

Specimens of a cryogenic insulation, proposed for use on the space shuttle external tank, were tested in an arc tunnel over a range of heating rates, pressures, and enthalpies corresponding to the shuttle ascent environment. A regression analysis was used to correlate the test data. Correlation equations involving surface recession rate as a function of heating rate, pressure, and enthalpy were developed. These equations can be used to make total surface recession predictions for shuttle ascent flight environments

Analytical determination of the effect of thermal property variations on the performance of a charring ablator

Effects of thermal-property variations on performance of charring ablato