15 research outputs found
Experiment Pointing Subsystems (EPS) requirements for Spacelab missions
The goal of the experiment pointing subsystems (EPS) is to accommodate a broad spectrum of instrument types by providing a number of stability and control functions that greatly exceed the capability of the shuttle. These functions include target acquisition, target tracking through wide gimbal ranges, stabilization, simultaneous pointing to one or more targets, instrument rastering, and on-orbit calibration. The experiments will vary widely in size, weight, geometry, and instrument types, and many have not been completely defined. This great diversity of requirements reflects the long term plans of the user community and establishes challenging performance requirements for the EPS
An assessment of the Instrument Pointing Subsystems (IPS) requirements for spacelab missions
Instrument Pointing Subsystem requirements for Spacelab missions in solar physics, stellar astronomy, and earth observation are analyzed and design guidelines for fine pointing instrument platforms are presented. The requirements for the platforms are time-phased based on NASA projections of flight mission models and payload scheduling. The experiments used for these projections are to be viewed as representative payloads. Other experiments or experiment groupings within any one discipline may be accommodated by an Instrument Pointing Subsystem that meets these requirements
Performance comparison of dwarf laying hens segregating for the naked neck gene in temperate and subtropical environments
This study compares laying performances between two environments of dwarf laying hen lines segregating for the naked neck mutation (NA locus), a selected dwarf line of brown-egg layers and its control line. Layers with one of the three genotypes at the NA locus were produced from 11 sires from the control line and 12 sires from the selected line. Two hatches produced 216 adult hens in Taiwan and 297 hens in France. Genetic parameters for laying traits were estimated in each environment and the ranking of sire breeding values was compared between environments. Laying performance was lower, and mortality was higher in Taiwan than in France. The line by environment interaction was highly significant for body weight at 16 weeks, clutch length and egg number, with or without Box-Cox transformation. The selected line was more sensitive to environmental change but in Taiwan it could maintain a higher egg number than the control line. Estimated heritability values in the selected line were higher in France than in Taiwan, but not for all the traits in the control line. The rank correlations between sire breeding values were low within the selected line and slightly higher in the control line. A few sire families showed a good ranking in both environments, suggesting that some families may adapt better to environmental change
Analyses of Cryogenic Propellant Tank Pressurization based upon Ground Experiments
The pressurization system of cryogenic propellant rockets requires on-board pressurant
gas. The objective of this study was to analyze the influence of the pressurant gas temperature
on the required pressurant gas mass in terms of lowering the launcher mass. First,
ground experiments were performed in order to investigate the pressurization process with
regard to the influence of the pressurant gas inlet temperature. Second, a system study
for the cryogenic upper stage of a small Two Stage to Orbit (TSTO) launch vehicle was
performed with focus on the influence of the pressurant gas temperature on the propellant
management system mass. One important experimental result is that for evaporated propellant
as pressurant gas, the maximum applicable gas temperature is best for reducing
the needed pressurant gas, but on condition that all pressurization lines are chilled down.
Moreover, the use of helium is very advantageous with regard to lowering the pressurant gas
mass. Also significant is that an immediate pressure drop occurred after the pressurization
end. The conclusion drawn from the system analysis is that an increased evaporated propellant
and helium pressurant gas temperature resulted in a decrease of the total propellant
management system mass, despite the application of external helium vessels
Value-at-Risk and Conditional Value-at-Risk Minimization for Hazardous Materials Routing
This chapter provides fundamentals of value-at-risk and conditional value-at-risk models applied to routing problems in hazardous materials transportation