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

Large Deployable Reflector Science and Technology Workshop. Volume 3: Systems and Technology Assessment

The results of five technology panels which convened to discuss the Large Deployable Reflector (LDR) are presented. The proposed LDR is a large, ambient-temperature, far infrared/submillimeter telescope designed for space. Panel topics included optics, materials and structures, sensing and control, science instruments, and systems and missions. The telescope requirements, the estimated technology levels, and the areas in which the generic technology work has to be augmented are enumerated

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

Parametric performance of circumferentially grooved heat pipes with homogeneous and graded-porosity slab wicks at cryogenic temperatures

A recently developed, potentially high-performance nonarterial wick has been extensively tested. This slab wick has an axially varying porosity which can be tailored to match the local stress imposed on the wick. The purpose of the tests was to establish the usefulness of the graded-porosity slab wick at cryogenic temperatures between 110 K and 260 K, with methane and ethane as working fluids. For comparison, a homogeneous (i.e., uniform porosity) slab wick was also tested. The tests included: (1) maximum heat pipe performance as a function of fluid inventory, (2) maximum performance as a function of operating temperature, (3) maximum performance as a function of evaporator elevation, and (4) influence of slab wick orientation on performance. The experimental data was compared with theoretical predictions obtained with the computer program GRADE

Apalachee During the Brisih Occupation

According to Prof. F. H. Hodder, in the introduction to his reprint of Pittman’s work entitled “The Present State of the European Settlements on the Mississippi,” there are but few available biographical data pertaining to Pittman. Hodder there presents such information as he was able to collect. Apparently Pittman must have accompanied the first British detachment occupying Florida, he states that he “resided four years as an engineer in those parts” and it is known that he left towards the close of 1768. Apparently during 1767 he was occupied in making surveys in different parts of West Florida, as records survive indicating his departure from. Pensacola for Apalachee on June 16, 1767. However the four reports here considered, submitted by Lieut. Pittman to General Haldimand bear no date. They are preserved among the Haldimand papers in the Public Archives of Canada, where they are calendared as Series B (Haldimand) Vol. 17, pp. 313-325. They are respectively numbered 313, 316, 319 and 322.