Method for Rapid Interplanetary Trajectory Analysis using ΔV Maps with Flyby Options

This paper develops a convenient tool which is capable of calculating ballistic interplanetary trajectories with planetary flyby options to create exhaustive V contour plots for both direct trajectories without flybys and flyby trajectories in a single chart. The contours of V for a range of departure dates (x-axis) and times of flight (y-axis) serve as a “visual calendar” of launch windows, which are useful for the creation of a long-term transportation schedule for mission planning purposes. For planetary flybys, a simple powered flyby manoeuvre with a reasonably small velocity impulse at periapsis is allowed to expand the flyby mission windows. The procedure of creating a V contour plot for direct trajectories is a straightforward full- factorial computation with two input variables of departure and arrival dates solving Lambert's problem for each combination. For flyby trajectories, a “pseudo full-factorial” computation is conducted by decomposing the problem into two separate full- factorial computations. Mars missions including Venus flyby opportunities are used to illustrate the application of this model for the 2020-2040 time frame. The “competitiveness” of launch windows is defined and determined for each launch opportunity

A Generalized Multi-Commodity Network Flow Model for the Earth-Moon-Mars Logistics System

Simple logistics strategies such as "carry-along" and Earth-based "resupply" were sufficient for past human space programs. Next-generation space logistics paradigms are expected to be more complex, involving multiple exploration destinations and in-situ resource utilization (ISRU). Optional ISRU brings additional complexity to the interplanetary supply chain network design problem. This paper presents an interdependent network flow modeling method for determining optimal logistics strategies for space exploration and its application to the human exploration of Mars. It is found that a strategy utilizing lunar resources in the cislunar network may improve overall launch mass to low Earth orbit for recurring missions to Mars compared to NASA’s Mars Design Reference Architecture 5.0, even when including the mass of the ISRU infrastructures that need to be pre-deployed. Other findings suggest that chemical propulsion using LOX/LH[subscript 2], lunar ISRU water production, and the use of aerocapture significantly contribute to reducing launch mass from Earth. A sensitivity analysis of ISRU reveals that under the given assumptions, local lunar resources become attractive at productivity levels above 1.8 kg/year/kg in the context of future human exploration of Mars.Jet Propulsion Laboratory (U.S.). Strategic University Research Partnerships Progra

Roles of environmental cues for embryonic incubation and hatching in mudskippers.

Reproduction on mudflats requires that eggs are protected from different environmental challenges during development and hatch when environmental conditions are favorable for survival of juveniles. Mudskippers are air-breathing, amphibious gobies of the subfamily Oxudercinae, and one of a few vertebrates that reside on mudflats. They excavate burrows in mudflats and deposit eggs in them. However, these burrows are filled with extremely hypoxic water, in which eggs could not survive. To secure embryonic development within their burrows, the burrow-guarding parental fish (a male or mating pair) store fresh air in an egg chamber, located near the bottom or at mid-depth in a burrow, by transporting mouthfuls of air during each low tide. The Japanese mudskipper, Periophthalmus modestus, is the best-studied species regarding reproductive strategies. The air-supplying behavior appears to be predominantly governed by the oxygen levels within egg chambers, but also by some other factor that is possibly related to the tidal cycle. When embryonic development is complete, the burrow-guarding male P. modestus removes the air from the egg chamber and releases the air outside the burrow on a nocturnal rising tide. Consequently, the tide floods the egg chamber and induces hatching. Because P. modestus eggs only have a 5-6 day window for hatching competence, the male\u27s initial selection of the position for the burrow in the intertidal zone and the timing of spawning relative to the tidal cycle are both important factors in hatching success. This is particularly crucial for those burrows in higher intertidal zones, which may be reached only by spring high tides. Not much is known for other mudskippers, but it is likely that they also employ similar reproductive strategies. The objective of this review is to summarize available information on reproductive strategies of mudskippers, and to discuss future directions to better elucidate mechanisms and adaptive significance for the reproduction of mudskippers. Further comparative studies with both mudskippers and other oxudercine gobies dwelling mudflats could shed new light on how vertebrates solved problems of reproduction when they expanded habitats to environments in an air-water interface

Systems-theoretic Safety Assessment of Robotic Telesurgical Systems

Robotic telesurgical systems are one of the most complex medical cyber-physical systems on the market, and have been used in over 1.75 million procedures during the last decade. Despite significant improvements in design of robotic surgical systems through the years, there have been ongoing occurrences of safety incidents during procedures that negatively impact patients. This paper presents an approach for systems-theoretic safety assessment of robotic telesurgical systems using software-implemented fault-injection. We used a systemstheoretic hazard analysis technique (STPA) to identify the potential safety hazard scenarios and their contributing causes in RAVEN II robot, an open-source robotic surgical platform. We integrated the robot control software with a softwareimplemented fault-injection engine which measures the resilience of the system to the identified safety hazard scenarios by automatically inserting faults into different parts of the robot control software. Representative hazard scenarios from real robotic surgery incidents reported to the U.S. Food and Drug Administration (FDA) MAUDE database were used to demonstrate the feasibility of the proposed approach for safety-based design of robotic telesurgical systems.Comment: Revise based on reviewers feedback. To appear in the the International Conference on Computer Safety, Reliability, and Security (SAFECOMP) 201

Implantation of Radioactive 119Sb

開始ページ、終了ページ: 冊子体のページ付

Decay of 59zn studied by ISOL

開始ページ、終了ページ: 冊子体のページ付

An In-Beam Study of Hyperfine Interactions of 69Ge in Zn

開始ページ、終了ページ: 冊子体のページ付

Effects of Ocean Acidification on Learning in Coral Reef Fishes

Ocean acidification has the potential to cause dramatic changes in marine ecosystems. Larval damselfish exposed to concentrations of CO2 predicted to occur in the mid- to late-century show maladaptive responses to predator cues. However, there is considerable variation both within and between species in CO2 effects, whereby some individuals are unaffected at particular CO2 concentrations while others show maladaptive responses to predator odour. Our goal was to test whether learning via chemical or visual information would be impaired by ocean acidification and ultimately, whether learning can mitigate the effects of ocean acidification by restoring the appropriate responses of prey to predators. Using two highly efficient and widespread mechanisms for predator learning, we compared the behaviour of pre-settlement damselfish Pomacentrus amboinensis that were exposed to 440 µatm CO2 (current day levels) or 850 µatm CO2, a concentration predicted to occur in the ocean before the end of this century. We found that, regardless of the method of learning, damselfish exposed to elevated CO2 failed to learn to respond appropriately to a common predator, the dottyback, Pseudochromis fuscus. To determine whether the lack of response was due to a failure in learning or rather a short-term shift in trade-offs preventing the fish from displaying overt antipredator responses, we conditioned 440 or 700 µatm-CO2 fish to learn to recognize a dottyback as a predator using injured conspecific cues, as in Experiment 1. When tested one day post-conditioning, CO2 exposed fish failed to respond to predator odour. When tested 5 days post-conditioning, CO2 exposed fish still failed to show an antipredator response to the dottyback odour, despite the fact that both control and CO2-treated fish responded to a general risk cue (injured conspecific cues). These results indicate that exposure to CO2 may alter the cognitive ability of juvenile fish and render learning ineffective