A methodology for selective removal of orbital debris

Earth-orbiting objects, large enough to be tracked, were surveyed for possible systematic debris removal. Based upon the statistical collision studies of others, it was determined that objects in orbits approximately 1000 km above the Earth's surface are at greatest collisional risk. Russian C-1B boosters were identified as the most important target of opportunity for debris removal. Currently, more than 100 in tact boosters are orbiting the Earth with apogees between 950 km and 1050 km. Using data provided by Energia USA, specific information on the C-1B booster, in terms of rendezvous and capture strategies, was discussed

Low Gravity Guidance System for Airborne Microgravity Research

Microgravity research techniques have been established to achieve a greater understanding of the role of gravity in the fundamentals of a variety of physical phenomena and material processing. One technique in use at the NASA Lewis Research Center involves flying Keplarian trajectories with a modified Lear Jet and DC-9 aircraft to achieve a highly accurate Microgravity environment by neutralizing accelerations in all three axis of the aircraft. The Low Gravity Guidance System (LGGS) assists the pilot and copilot in flying the trajectories by displaying the aircraft acceleration data in a graphical display format. The Low Gravity Guidance System is a microprocessor based system that acquires and displays the aircraft acceleration information. This information is presented using an electroluminescent display mounted over the pilot's instrument panel. The pilot can select the Microgravity range that is required for a given research event. This paper describes the characteristics, design, calibration and testing of the Low Gravity Guidance System Phase 3, significant lessons from earlier systems and the developmental work on future systems

Piloted Evaluation of an Integrated Methodology for Propulsion and Airframe Control Design

An integrated methodology for propulsion and airframe control has been developed and evaluated for a Short Take-Off Vertical Landing (STOVL) aircraft using a fixed base flight simulator at NASA Lewis Research Center. For this evaluation the flight simulator is configured for transition flight using a STOVL aircraft model, a full nonlinear turbofan engine model, simulated cockpit and displays, and pilot effectors. The paper provides a brief description of the simulation models, the flight simulation environment, the displays and symbology, the integrated control design, and the piloted tasks used for control design evaluation. In the simulation, the pilots successfully completed typical transition phase tasks such as combined constant deceleration with flight path tracking, and constant acceleration wave-off maneuvers. The pilot comments of the integrated system performance and the display symbology are discussed and analyzed to identify potential areas of improvement

The Costs of Carnivory

Mammalian carnivores fall into two broad dietary groups: smaller carnivores (<20 kg) that feed on very small prey (invertebrates and small vertebrates) and larger carnivores (>20 kg) that specialize in feeding on large vertebrates. We develop a model that predicts the mass-related energy budgets and limits of carnivore size within these groups. We show that the transition from small to large prey can be predicted by the maximization of net energy gain; larger carnivores achieve a higher net gain rate by concentrating on large prey. However, because it requires more energy to pursue and subdue large prey, this leads to a 2-fold step increase in energy expenditure, as well as increased intake. Across all species, energy expenditure and intake both follow a three-fourths scaling with body mass. However, when each dietary group is considered individually they both display a shallower scaling. This suggests that carnivores at the upper limits of each group are constrained by intake and adopt energy conserving strategies to counter this. Given predictions of expenditure and estimates of intake, we predict a maximum carnivore mass of approximately a ton, consistent with the largest extinct species. Our approach provides a framework for understanding carnivore energetics, size, and extinction dynamics

The Phylogenetic-Relationships of the Genus Eimeria Based On Comparison of Partial Sequences of 18s Ribosomal-Rna

Reverse transcription of ribosomal RNA (rRNA) was used to obtain partial sequences of the small subunit rRNA (ssrRNA) of three species of Eimeria: Eimeria maxima, Eimeria stiedae and Eimeria tenella. These sequences were aligned with the homologous ssrRNA sequence segments of a range of other organisms in the phylum Apicomplexa, along with representatives of the ciliates, fungi, flagellates, higher plants and higher eukaryotes. Two phylogenetic tree building methods were used to investigate the phylogenetic relationships among the Eimeria species, and between the Eimeria and the other organisms represented, using Vairimorpha necatrix as an outgroup. The results show that Eimeria is almost certainly monophyletic with the apicomplexans Sarcocystis, Toxoplasma and Cryptosporidium. The three species of Eimeria differ among each other at a maximum of 9 out of 600 nucleotides at the ssrRNA locus. Such intrageneric variation is high by vertebrate standards, but low by protist standards

Predicting White Spruce Cone Crops in the Boreal Forests of the Southern and Central Yukon

White spruce cone crops were measured at five regional centers in the southern and central Yukon for 30 years at one site from 1986 to 2015 and at four other sites from 9-11 years to select the best climatic model that use cues from growing season temperature and rainfall to predict the size of cone crops. We evaluated six climate models that use summer temperature and rainfall of years t-1, and t-2 to predict cone crops in year t. July temperatures provided the best predictors of white spruce cone crops and no rainfall variable was related to the size of cone crops. We explored three variants of July temperatures: mean temperature, degree-days > 5°C, and maximum temperatures. For each of these we used the ΔT model that uses the difference in the July temperature measures of year t-1 and t-2. We compared the resulting 6 models with AICc to determine their relative predictive performance. The best model combined ΔT measures of degree-days >5°C and the four highest daily maximum July temperatures with R2 = 0.65. By comparison the ΔT model involving only mean July temperatures was less successful (R2 = 0.49). There was good regional synchrony (rp = 0.7 to 0.8) in high cone crops over the southern and central Yukon during 1986 to 2015.The accepted manuscript in pdf format is listed with the files at the bottom of this page. The presentation of the authors' names and (or) special characters in the title of the manuscript may differ slightly between what is listed on this page and what is listed in the pdf file of the accepted manuscript; that in the pdf file of the accepted manuscript is what was submitted by the author