Planning for Performance Augmentation of Space Shuttle

Augmented performance is necessary to assure that the full Space Shuttle payload deployment capability of 32,000 Ibs can be achieved for the 98° inclination, 150 nautical mile circular mission launched from Vandenberg AFB, Calif. The performance-augmented Space Shuttle meets all design mission requirements, and offers potential payload growth to accommodate new payloads and new concepts. Consequently, it is important to the future national space capability that performance augmentation be developed and made available to meet payload requirements which exploit the capability of the Space Shuttle. This paper presents the options under consideration which include uprating the Space Shuttle Main Engines (SSMEs) to the range of 115 percent of rated power level for nominal operations, Solid Rocket Motor (SRM) filamentwound case segments, and the Liquid Boost Module (LBM). These candidates will be studied in detail for the remainder of FY81 and FY82. Selection and initiation of development in FY83 will support the early 1987 need date

Paper Session III-A - Human Exploration Initiative

Reliable access to space through the use of a mixed fleet of launch vehicles, including the Space Transportation System (STS) and other existing and new systems, will be needed to provide the capability to accommodate the major new initiative for the Human Exploration (HEI) Program. The operational Space Station Freedom (SSF) will be established as a transportation node for Lunar and planetary missions and will required the Shuttle-C for assembly and implementation. The proposed Lunar mission schedule beginning in 1999 will also require a heavy lift launch vehicle (HLLV) capability in the class of the Shuttle- C. The large payloads and associated quantities of propellent needed for the establishment and maintenance of Lunar and Mars outposts will require a heavy-lift launch capability not now available to the United States with existing Earth-to-orbit transportation systems,. This augmented mixed fleet of launch vehicles will require extensive expansion and modification in the vehicle and payload launch processing operations, to meet current commitments and to accomplish this bold new initiative. This paper will provide an update of the planning for the Human Exploration Initiative announced by President Bush on July 20, 1989. It will review the activity that has transpired during the period following this announcement and will discuss the various options in mission design, proposed launch vehicles and program phasing under consideration, with special emphasis on the planning for the ground processing capabilities required at the Kennedy Space Center

Dislocation interactions during low-temperature plasticity of olivine and their impact on the evolution of lithospheric strength

The strength of the lithosphere is typically modelled based on constitutive equations for steady-state flow. However, strain hardening may cause significant evolution of strength in the colder load-bearing portion of the lithosphere. Recent rheological data from low-temperature deformation experiments on olivine suggest that strain hardening occurs due to the presence of temperature-independent back stresses generated by long-range elastic interactions among dislocations. These interpretations provided the basis for a flow law that incorporates hardening by the development of back stress. Here, we test this dislocation-interaction hypothesis by examining the microstructures of olivine samples deformed plastically at room temperature either in a deformation-DIA apparatus at differential stresses of ≤4.3GPa or in a nanoindenter at applied contact stresses of ≥10.2GPa. High-angular resolution electron backscatter diffraction maps reveal the presence of geometrically necessary dislocations with densities commonly above 1014m−2 and intragranular heterogeneities in residual stress on the order of 1 GPa in both sets of samples. Scanning transmission electron micrographs reveal straight dislocations aligned in slip bands and interacting with dislocations of other types that act as obstacles. The resulting accumulations of dislocations in their slip planes, and associated stress heterogeneities, are consistent with strain hardening resulting from long-range back-stresses acting among dislocations and thereby support the form of the flow law for low-temperature plasticity. Based on these observations, we predict that back stresses among dislocations will impart significant mechanical anisotropy to deformed lithosphere by enhancing or reducing the effective stress. Therefore, strain history, with associated microstructural and micromechanical evolution, is an important consideration for models of lithospheric strength. The microstructural observations also provide new criteria for identifying the operation of back-stress induced strain hardening in natural samples and therefore provide a means to test the applicability of the flow law for low-temperature plasticity.This research was supported by Natural Environment Research Council grants NE/M000966/1 to LNH, AJW, and DW and 1710DG008/JC4 to LNH and AJW; European Plate Observing System Transnational Access grant EPOS-TNA-MSL 2018-022 to LNH; Advanced Photon Source General User Proposal 55176 to LNH, DLG, and WBD; and National Science Foundation Awards EAR-1361319 to WBD, EAR-1625032 to JMW, and EAR-1806791 to KMK

Rheological and Thermal Properties of Icy Materials

From the issue entitled "Satellites of the Outer Solar System: Exchange Processes Involving the Interiors"Laboratory measurements of physical properties of planetary ices generate information for dynamical models of tectonically active icy bodies in the outer solar system. We review the methods for measuring both flow properties and thermal properties of icy planetary materials in the laboratory, and describe physical theories that are essential for intelligent extrapolation of data from laboratory to planetary conditions. This review is structured with a separate and independent section for each of the two sets of physical properties, rheological and thermal. The rheological behaviors of planetary ices are as diverse as the icy moons themselves. High-pressure water ice phases show respective viscosities that vary over four orders of magnitude. Ices of CO2, NH3, as well as clathrate hydrates of CH4 and other gases vary in viscosity by nearly ten orders of magnitude. Heat capacity and thermal conductivity of detected/inferred compositions in outer solar system bodies have been revised. Some low-temperature phases of minerals and condensates have a deviant thermal behavior related to paramount water ice. Hydrated salts have low values of thermal conductivity and an inverse dependence of conductivity on temperature, similar to clathrate hydrates or glassy solids. This striking behavior may suit the dynamics of icy satellites

Dislocation interactions during low-temperature plasticity of olivine and their impact on the evolution of lithospheric strength

The strength of the lithosphere is typically modelled based on constitutive equations for steady-state flow. However, strain hardening may cause significant evolution of strength in the colder load-bearing portion of the lithosphere. Recent rheological data from low-temperature deformation experiments on olivine suggest that strain hardening occurs due to the presence of temperature-independent back stresses generated by long-range elastic interactions among dislocations. These interpretations provided the basis for a flow law that incorporates hardening by the development of back stress. Here, we test this dislocation-interaction hypothesis by examining the microstructures of olivine samples deformed plastically at room temperature either in a deformation-DIA apparatus at differential stresses of ≤4.3GPa or in a nanoindenter at applied contact stresses of ≥10.2GPa. High-angular resolution electron backscatter diffraction maps reveal the presence of geometrically necessary dislocations with densities commonly above 1014m−2 and intragranular heterogeneities in residual stress on the order of 1 GPa in both sets of samples. Scanning transmission electron micrographs reveal straight dislocations aligned in slip bands and interacting with dislocations of other types that act as obstacles. The resulting accumulations of dislocations in their slip planes, and associated stress heterogeneities, are consistent with strain hardening resulting from long-range back-stresses acting among dislocations and thereby support the form of the flow law for low-temperature plasticity. Based on these observations, we predict that back stresses among dislocations will impart significant mechanical anisotropy to deformed lithosphere by enhancing or reducing the effective stress. Therefore, strain history, with associated microstructural and micromechanical evolution, is an important consideration for models of lithospheric strength. The microstructural observations also provide new criteria for identifying the operation of back-stress induced strain hardening in natural samples and therefore provide a means to test the applicability of the flow law for low-temperature plasticity