Traveling the Solar System using ion engines
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A simple method of estimating vehicle parameters appropriate for interplanetary travel can provide a useful tool for evaluating the suitability of particular propulsion systems to various space missions. Although detailed mission analyses for interplanetary travel can be quite complex, it is possible to derive hirly simple correlations which will provide reasonable trip time estimates to the planets. In the present work, it is assumed that a constant thrust propulsion system propels a spacecraft on a round trip mission having equidistant outbound and inbound legs in which the spacecraft accelerates during the first portion of each leg of the journey and decelerates during the last portion of each leg of the journey. Comparisons are made with numerical calculations from low thrust trajectory codes to estimate the range of applicability of the simplified correlations.
Waveforms known well enough to detect some EMRIs today. Soon, enough to realize Gair et al estimate of approx. 100's to 1000's of detections to z = 1. Not yet enough to for precision parameter estimation of Barack and Cutler (mass and spin to 10(exp -4)). Some turning to the more exotic: non-Kerr background, gas interaction, third body, ... More status and refs: Drasco, gr-qc/0604115.
Recent chondritic meteorite finds in Antarctica have included CB, CH, CK and R chondrites, the latter two of which are among the most oxidized materials found in meteorite collections. In this study we present petrographic and mineralogic data for a suite of CK and R chondrites, and compare to previous studies of CK and R, as well as some CV chondrites. In particular we focus on the opaque minerals magnetite, chromite, sulfides, and metal as well as unusual silicates hornblende, biotite, and plagioclase. Several mineral thermometers and oxy-barometers are utilized to calculate temperatures and oxygen fugacities for these unusual meteorites compared to other more common chondrite groups. R and CK chondrites show lower equilibrium temperatures than ordinary chondrites, even though they are at similar petrologic grades (e.g., thermal type 6). Oxygen fugacity calculated for CV and R chondrites ranges from values near the iron-wustite (IW) oxygen buffer to near the fayalite-magnetite-quartz (FMQ) buffer. In comparison, the fO2 recorded by ilmenite-magnetite pairs from CK chondrites are much higher, from FMQ+3.1 to FMQ+5.2. The latter values are the highest recorded for materials in meteorites, and place some constraints on the formation conditions of these magnetite-bearing chondrites. Differences between mineralogic and O isotopic compositions of CK and R chondrites suggest two different oxidation mechanisms, which may be due to high and low water: rock ratios during metamorphism, or to different fluid compositions, or both.
Probes are an essential element in the scientific study of planets with atmospheres. In-situ measurements provide the most accurate determination of composition, winds, temperatures, clouds, and radiative fluxes. They address fundamental NASA objectives concerning volatile compounds, climate, and the origin of life. Probes also deliver landers and aerobots that help in the study of planetary surfaces. This talk focuses on Venus, Titan, and the giant planets. I review the basic science questions and discuss the recommended missions. I stress the need for a balanced program that includes an array of missions that increase in size by factors of two. Gaps in this array lead to failures and cancellations that are harmful to the program and to scientific exploration.
Water ices in surface crusts of Europa, Enceladus, Saturn's main rings, and Kuiper Belt Objects can become heavily oxidized from radiolytic chemical alteration of near-surface water ice by space environment irradiation. Oxidant accumulations and gas production are manifested in part through observed H2O2 on Europa. tentatively also on Enceladus, and found elsewhere in gaseous or condensed phases at moons and rings of Jupiter and Saturn. On subsequent chemical contact in sub-surface environments with significant concentrations of primordially abundant reductants such as NH3 and CH4, oxidants of radiolytic origin can react exothermically to power gas-driven cryovolcanism. The gas-piston effect enormously amplifies the mass flow output in the case of gas formation at basal thermal margins of incompressible fluid reservoirs. Surface irradiation, H2O2 production, NH3 oxidation, and resultant heat, gas, and gas-driven mass flow rates are computed in the fluid reservoir case for selected bodies. At Enceladus the oxidant power inputs are comparable to limits on nonthermal kinetic power for the south polar plumes. Total heat output and plume gas abundance may be accounted for at Enceladus if plume activity is cyclic in high and low "Old Faithful" phases, so that oxidants can accumulate during low activity phases. Interior upwelling of primordially abundant NH3 and CH4 hydrates is assumed to resupply the reductant fuels. Much lower irradiation fluxes on Kuiper Belt Objects require correspondingly larger times for accumulation of oxidants to produce comparable resurfacing, but brightness and surface composition of some objects suggest that such activity may be ongoing.
Here, we compare Sm-147-Nd-143 and Sm-146-Nd-142 data for lunar norite 78236 to those for approximately 4.54-4.56 Ga old cumulate eucrite Yamato 980318/433 and show that the norite data are compatible with its derivation from an isotopic reservoir similar to that from whence the eucrite pair came. Thus, lunar-like Sm-Nd isotopic systematics are not unique to the Earth-Moon system.
"Space weathering" is the term given to the cumulative effects incurred by surfaces which are exposed to the harsh environment of space. Lunar sample studies over the last decade or so have produced a clear picture of space weathering processes in the lunar environment. By combining laboratory and remote spectra with microanalytical methods (scanning and transmission electron microscopy), we have begun to unravel the various processes (irradiation, micrometeorite bombardment, etc) that contribute to space weathering and the physical and optical consequences of those processes on the Moon. Using the understanding gleaned from lunar samples, it is possible to extrapolate weathering processes to other airless bodies from which we have not yet returned samples (i.e. Mercury, asteroids). Through experiments which simulate various components of weathering, the expected differences in environment (impact rate, distance from Sun, presence of a magnetic field, reduced or enhanced gravity, etc) and composition (particularly iron content) can be explored to understand how space weathering will manifest on a given body.
Presentation topics include: what is NASA's mission, why the Moon next, options for Moon landings, NASA's exploration roadmap, building on a foundation of proven technologies - launch vehicle comparisons, Ares nationwide team, Ares I elements, vehicle integration accomplishments, Aires I-X test flight, Ares I-X accomplishments, Orion crew exploration vehicle, Altair lunar lander, and Ares V elements.
The workshop blended three major themes: (1) How can elements of the Constellation program, and specifically, the planned Ares-V heavy-launch vehicle, benefit the planetary community by enabling the launch of large planetary payloads that cannot be launched on existing vehicles, and how can the capabilities of an Ares V allow the planetary community to redesign missions to achieve lower risk, and perhaps lower cost on these missions? (2) What are some of the planetary missions that either can be significantly enhanced or enabled by an Ares-V launch vehicle? What constraints do these mission concepts place on the payload environment of the Ares V? (3) Technology challenges that need to be addressed for launching large planetary payloads. Presentations varied in length from 15-40 minutes. Ample time was provided for discussion.
This presentation will address: (1) Communications capabilities that will be needed for space missions for Small Planetary Body exploration (2) Utilization of large ground-based radar capabilities for Small Body remote sensing and mission planning
Viewed from a cosmic perspective, Earth is a dry planet yet its oceans are enriched in deuterium by a large factor relative to nebular hydrogen. Can comets have delivered Earth s water? The question of exogenous delivery of water and organics to Earth and other young planets is of critical importance for understanding the origin of Earth s water, and for assessing the possible existence of exo-planets similar to Earth. Strong gradients in temperature and chemistry in the proto-planetary disk, coupled with dynamical models, imply that comets from the Oort Cloud and Kuiper Disk reservoirs should have diverse composition. The primary volatiles in comets (ices native to the nucleus) provide the preferred metric, and taxonomies based on them are now beginning to emerge [1, 2, 3]. The measurement of cosmic parameters such as the nuclear spin temperatures for H2O, NH3, and CH4, and of enrichment factors for isotopologues (D/H in water and hydrogen cyanide, N-14/N-15 in CN and hydrogen cyanide) provide additional important tests for the origin of cometary material.
The field of astrochemistry investigates the origin of the chemicals necessary for the formation of life. Astrochemists use remote observations, laboratory simulations, and analysis of extraterrestrial samples to understand the inventory of pre biotic chemicals present on the early Earth. Among the problems investigated by astrochemists is the origin of homo chirality in terrestrial life. Analysis of meteorites shows that they may have delivered an excess of L-amino acids to the Earth's surface, perhaps leading to homochirality.
Viewed from a cosmic perspective, Earth is a dry planet yet its oceans are enriched in deuterium by a large factor relative to nebular hydrogen. Can comets have delivered Earth's water? The question of exogenous delivery of water and organics to Earth and other young planets is of critical importance for understanding the origin of Earth's water, and for assessing the possible existence of exo-planets similar to Earth. Strong gradients in temperature and chemistry in the proto-planetary disk, coupled with dynamical models, imply that comets from the Oort Cloud and Kuiper Disk reservoirs should have diverse composition. The primary volatiles in comets (ices native to the nucleus) provide the preferred metric, and taxonomies based on them are now beginning to emerge [1,2,3]. The measurement of cosmic parameters such as the nuclear spin temperatures for H2O, NH3, and CH4, and of enrichment factors for isotopologues (D/H in water and hydrogen cyanide, N-14/N-15 in CN and hydrogen cyanide provide additional important tests for the origin of cometary material. I will provide an overview of these aspects, and their implications for the origin of Earth's water and prebiotic organics.
No abstract available
Energetic ions present in the diverse plasma conditions in space play a significant role in the formation and modification of solid phases found in environments ranging from the interstellar medium (ISM) to the surfaces of airless bodies such as asteroids and the Moon. These effects are often referred to as space radiation processing, a term that encompasses changes induced in natural space-exposed materials that may be only structural, such as in radiation-induced amorphization, or may involve ion-induced nanoscale to microscale chemical changes, as occurs in preferential sputtering and ion-beam mixing. Ion sputtering in general may also be responsible for partial or complete erosion of space exposed materials, in some instances possibly bringing about the complete destruction of free-floating solid grains in the ISM or in circumstellar nebular dust clouds. We report here on two examples of the application of high-resolution and analytical transmission electron microscopy (TEM) to problems in space radiation processing. The first problem concerns the role of space radiation processing in controlling the overall fate of Fe sulfides as hosts for sulfur in the ISM. The second problem concerns the known, but as yet poorly quantified, role of space radiation processing in lunar space weathering.