ALBERT

Description: Abstract Aim To investigate biotic and abiotic correlates of reef‐fish species richness across multiple spatial scales. Location Tropical reefs around the globe, including 485 sites in 109 sub‐provinces spread across 14 biogeographic provinces. Time period Present. Major taxa studied 2,523 species of reef fish. Methods We compiled a database encompassing 13,050 visual transects. We used hierarchical linear Bayesian models to investigate whether fish body size, reef area, isolation, temperature, and anthropogenic impacts correlate with reef‐fish species richness at each spatial scale (i.e., sites, sub‐provinces, provinces). Richness was estimated using coverage‐based rarefaction. We also tested whether species packing (i.e., transect‐level species richness/m2) is correlated with province‐level richness. Results Body size had the strongest effect on species richness across all three spatial scales. Reef area and temperature were both positively correlated with richness at all spatial scales. At the site scale only, richness decreased with reef isolation. Species richness was not correlated with proxies of human impacts. Species packing was correlated with species richness at the province level following a sub‐linear power function. Province‐level differences in species richness were also mirrored by patterns of body size distribution at the site scale. Species‐rich provinces exhibited heterogeneous assemblages of small‐bodied species with small range sizes, whereas species‐poor provinces encompassed homogeneous assemblages composed by larger species with greater dispersal capacity. Main conclusions Our findings suggest that body size distribution, reef area and temperature are major predictors of species richness and accumulation across scales, consistent with recent theories linking home range to species–area relationships as well as metabolic effects on speciation rates. Based on our results, we hypothesize that in less diverse areas, species are larger and likely more dispersive, leading to larger range sizes and less turnover between sites. Our results indicate that changes in province‐level (i.e., regional) richness should leave a tractable fingerprint in local assemblages, and that detailed studies on local‐scale assemblage composition may be informative of responses occurring at larger scales.

Description: Inversion of ordinary linear differential equation in matrix form for application to class of trajectory perturbation problems

Description: Inversion property of the fundamental matrix in trajectory perturbation problems

Description: Trajectory energy requirements for low-thrust flights throughout solar system using nuclear- electric propulsion

Description: Earth to Mars transportation requirements are derived for a permanent Mars base of 20 people operating in the 2035 time frame. In order to satisfy these requirements, various transportation modes are developed assuming an existing space infrastructure including propellant tankers, crew and consumable transfer vehicles, orbital facilities and extraterrestrial propellant factories. These transportation modes are compared with respect to total propellant requirements, number of vehicles required, flight times, frequency of opportunity and several other characteristics. Directions for further studies and analysis are indicated.

Description: A probabilistic analysis, based on orbital mechanics, is performed to evaluate the chances of meteoroids entering into earth orbit and the potential population of such objects. The problem is addressed in terms of meteoroids on earth collision courses, slowed by atmosphere entry/exit, entering elliptical orbits with apogees above the atmosphere. The overall capture probability is derived by integrating the capture fraction dependence on velocity and size over the probability frequency distribution of the collision courses. Account is taken of eventual orbit decay, lunar infall and ejection after encounters with the moon. The results indicate that the probability that a natural 10-100 m diam object has achieved earth orbit is negligibly small.

Description: The results of a study performed to characterize the propellant mass requirements of two new types of orbit transfers between earth and Mars are discussed. These new orbit types, called VISIT and Up/Down Escalators, cycle continuously between the two planets, allowing a large crew facility, or CASTLE, to remain in this orbit with smaller crew transfer vehicles, or Taxis, used to shuttle between planetary orbits and this vehicle. Trajectory options and infrastructure elements are discussed along with the assumptions made in this study. The latter include the existence of a mature Martian base and the production and use of extraterrestrial propellants. Performance results from each of the three orbit transfer options presented here are discussed.

Description: This paper describes the basic characteristics of circulating (cyclical) orbit design as applied to round-trip transportation of crew and materials between earth and Mars in support of a sustained manned Mars Surface Base. The two main types of nonstopover circulating trajectories are the socalled VISIT orbits and the Up/Down Escalator orbits. Access to the large transportation facilities placed in these orbits is by way of taxi vehicles using hyperbolic rendezvous techniques during the successive encounters with earth and Mars. Specific examples of real trajectory data are presented in explanation of flight times, encounter frequency, hyperbolic velocities, closest approach distances, and Delta V maneuver requirements in both interplanetary and planetocentric space.