Fundamental Studies Relating to Systems Analysis of Solid Propellants

In this report the groundwork is laid for the proposed work scope which stressed the need for a greater understanding of the solid mechanics of grains. Particular emphasis will be directed toward the multi-axial behavior of thick walled configurations. The work falls naturally into three areas; (1) analysis procedures, (2) material properties, and (3) failure criteria. As a necessary preliminary to treating specific designs, certain material of general applicability must be developed, collected, and summarized. The following sections therefore deal with a general description of viscoelastic analysis and material representation, discussed by contrast with more conventional engineering analysis. By this means a background is established for the collection of elastic design formulas which are included in the second section of the report

Fundamental Studies Relating to Systems Analysis of Solid Propellants

The earlier progress reports presented some essentials of model representation and a summary of some elastic solutions as preliminary material for viscoelastic analyses of solid propellants under various loading conditions. The present report is a continuation of the above with a brief section on Thermal Distributions, a section called Engineering Analysis, and one on Failure Criteria. The thermal distributions, obtained from heat transfer theory, are required for the thermoelastic formulations of section II. The Engineering Analysis section includes several varied examples to assist in understanding the analysis techniques presented in the other sections. The final section relates to mechanical failure of propellants and presents some preliminary thoughts as to how the study of this important problem area will be conducted

Fundamental Studies Relating to Systems Analysis of Solid Propellants

As in the previous progress reports, the contents in this report have been categorized so as to present a clear picture of their role in contributing to the problem of mechanical failure analysis. The subject of material representation by mechanical failure analysis. The subject of material representation by mechanical models is discussed in Section I, while Section II contains additions to the subject of Elastic Solutions for cylinders. The Engineering Analysis section includes an example of the strain response of an internal star grain to pressure. A damped sinusoid has been assumed for the pressure rise, and the use of stress concentration factors for a star grain is demonstrated. Section V on failure includes some preliminary test results which indicate the feasibility of the cumulative damage concept for composite (polyurethane) propellants, at least in the limited range tested. Recommendations are given which would expand this testing to show how damage accumulates under other conditions such as low temperatures, high strain-rates and with other types of propellant

Fundamental Studies Relating to Systems Analysis of Solid Propellants

In this report the groundwork is laid for the proposed work scope which stressed the need for a greater understanding of the solid mechanics of grains. Particular emphasis will be directed toward the multi-axial behavior of thick walled configurations. The work falls naturally into three areas; (1) analysis procedures, (2) material properties, and (3) failure criteria. As a necessary preliminary to treating specific designs, certain material of general applicability must be developed, collected, and summarized. The following sections therefore deal with a general description of viscoelastic analysis and material representation, discussed by contrast with more conventional engineering analysis. By this means a background is established for the collection of elastic design formulas which are included in the second section of the report

Field Analysis of Microbial Contamination Using Three Molecular Methods in Parallel

Advanced technologies with the capability of detecting microbial contamination remain an integral tool for the next stage of space agency proposed exploration missions. To maintain a clean, operational spacecraft environment with minimal potential for forward contamination, such technology is a necessity, particularly, the ability to analyze samples near the point of collection and in real-time both for conducting biological scientific experiments and for performing routine monitoring operations. Multiple molecular methods for detecting microbial contamination are available, but many are either too large or not validated for use on spacecraft. Two methods, the adenosine- triphosphate (ATP) and Limulus Amebocyte Lysate (LAL) assays have been approved by the NASA Planetary Protection Office for the assessment of microbial contamination on spacecraft surfaces. We present the first parallel field analysis of microbial contamination pre- and post-cleaning using these two methods as well as universal primer-based polymerase chain reaction (PCR)

Systemic immunosuppression depletes peripheral blood regulatory B cells in patients with immune thrombocytopenia

Regulatory B (Breg) cells are potentially implicated in the pathogenesis of immune thrombocytopenia (ITP). We analysed a prospective cohort of newly diagnosed steroid naïve ITP patients enrolled in the multicentre FLIGHT trial and found that the numbers of Bregs in their peripheral blood were similar to healthy controls. In contrast, Breg numbers were significantly reduced in ITP patients treated with systemic immunosuppression (glucocorticoids or mycophenolate mofetil). We also demonstrate that glucocorticoid treatment impairs Breg interleukin-10 production via an indirect T-cell-mediated mechanism

Fundamental Studies Relating to Systems Analysis of Solid Propellants : Progress Report No. 5 - GALCIT 101, Subcontract No. RU- 293, October l, 1959-December 31, 1959

Previous reports of this series have attempted to define some of the important parameters affecting the structural integrity of solid propellant rocket grains. Three general areas have been discussed, namely material properties, analytical procedures, and criteria for mechanical failure. This particular report is devoted to a more detailed examination of the properties of a filled viscoelastic resin, and their representation by appropriate mechanical models. In addition, a comparison of two methods of computing viscoelastic strains in a pressurized cylinder is presented. In the category of material properties, linear viscoelastic model theory is reviewed, and certain important relations among sets of experimental data are deduced. A justification for the application of this theory is provided by the analytic representation of available dynamic data in terms of a well-known distribution function. Since the inception of this work additional experimental data on propellants has become available. In the category of analytical procedures, the usual approach of representing material properties by a four-element model, as determined from the dynamic data in a limited frequency range, is compared with the more sophisticated Fourier transform method in which the entire frequency range is utilized. The two approaches are applied to calculate the viscoelastic hoop strain at the inner boundary of an internally pressurized infinitely long hollow cylinder subjected to a ramp-type pressure pulse. In this example, the dilatation is assumed elastic or frequency independent and the distortion viscoelastic. In the following quarter, primary effort will be devoted to the determination of a criterion for mechanical failure of propellants. Two steps are involved. One is the analytical representation of ultimate strain as a function of temperature on strain rate by means of a mechanical model. In addition to the usual distribution of relaxation (or retardation) times, this model will be supplied with a distribution of ultimate strain. Step two involves the choice of a suitable criterion for compounding ultimate strain or ultimate stress components into a single parameter, which, when exceeded at a given rate and temperature, denotes the onset of fracture or mechanical failure