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361.
Mathematical models derived for describing the combustion of solid rocket propellants have in the past assumed that the thermal properties, specific heat, and thermal conductivity are constant throughout the solid phase portion of the combustion zone. The values for specific heat and thermal conductivity can vary as much as 50–100 percent for the temperatures in the solid phase combustion wave, values from about 250 to 1100 K. Thus, the variation in solid phase properties due to the temperature variation in the solid phase have significant effects on the burning rate, the temperature sensitivity and the pressure coupled response. The paper is concerned with predicting the effect of the variable solid phase properties on the combustion properties. Parametric calculations were made to illustrate the effect of the magnitude of the variation of solid phase properties with temperature. The results indicate that significant differences exist between the values for the combustion parameters calculated using variable thermal properties as compared to those calculated using constant thermal properties. 相似文献
362.
On 7 June 2006 the Royal Aeronautical Society (RAeS) hosted a one-day conference entitled ‘Space Tourism: From Lofty Dreams to Commercial Reality’ in London. The conference brought together parties interested in the future of passenger flights into space, presenting perspectives on the evolution of the private spaceflight industry over the next decade, with the goal of stimulating enthusiasm for the creation of a profitable industry and affordable space travel for a mass, global market. The conference chairman reports on its outcomes. 相似文献
363.
Scientific and policy developments in the field of Near-Earth Objects (NEOs) since the UN NEO conference in 1995 are briefly outlined. Some areas of research and discovery have exhibited considerable progress while others have languished. In particular, facilities in the southern hemisphere for discovery and tracking of NEOs are inadequate. Suggestions are made both at the scientific and technical levels as well as at the policy level to provide coordinated and coherent progress in developing a long-term approach to NEO hazard mitigation. The next step should be the establishment of a panel of international scientific experts on the subject. 相似文献
364.
The observational and theoretical arguments for spatial fragmentation of the bulk of the thermal and non-thermal components of solar flare plasma are summarised. Observational aspects considered include XUV filling factors, EUV centre to limb variations, andH impact polarisation. Theoretical points addressed are the high flare inductance and beam/return current closure at the acceleration site.A high degree of beam/plasma filamentation implies strong transverse temperature gradients so that cross-field conduction must be included in energy transport modelling. Preliminary results are described for a simple two-component model. 相似文献
365.
John E. Moores Raymond Francis Marianne Mader G.R. Osinski T. Barfoot N. Barry G. Basic M. Battler M. Beauchamp S. Blain M. Bondy R-D. Capitan A. Chanou J. Clayton E. Cloutis M. Daly C. Dickinson H. Dong R. Flemming P. Furgale J. Gammel N. Gharfoor M. Hussein R. Grieve H. Henrys P. Jaziobedski A. Lambert K. Leung C. Marion E. McCullough C. McManus C.D. Neish H.K. Ng A. Ozaruk A. Pickersgill L.J. Preston D. Redman H. Sapers B. Shankar A. Singleton K. Souders B. Stenning P. Stooke P. Sylvester L. Tornabene 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2012
366.
The geomagnetic signal contains an enormous temporal range—from geomagnetic jerks on time scales of less than a year to the evolution of Earth’s dipole moment over billions of years. This review compares observations and numerical models of the long-term range of that signal, for periods much larger than the typical overturn time of Earth’s core. On time scales of 105–109 years, the geomagnetic field reveals the control of mantle thermodynamic conditions on core dynamics. We first briefly describe the general formalism of numerical dynamo simulations and available paleomagnetic data sets that provide insight into paleofield behavior. Models for the morphology of the time-averaged geomagnetic field over the last 5 million years are presented, with emphasis on the possible departures from the geocentric axial dipole hypothesis and interpretations in terms of core dynamics. We discuss the power spectrum of the dipole moment, as it is a well-constrained aspect of the geomagnetic field on the million year time scale. We then summarize paleosecular variation and intensity over the past 200 million years, with emphasis on the possible dynamical causes for the occurrence of superchrons. Finally, we highlight the geological evolution of the geodynamo in light of the oldest paleomagnetic records available. A summary is given in the form of a tentative classification of well-constrained observations and robust numerical modeling results. 相似文献
367.
Blinn John C. Campbell James P. 《IEEE transactions on aerospace and electronic systems》1966,(5):585-590
This paper discusses the results of an analytic study of the feasibility of using microwave radiometry as a technique for navigation data sensing in Army aircraft. The study included a review of Army aircraft characteristics and navigation requirements. Various means of sensing passively aircraft velocity, altitude, and velocity-altitude ratio were considered. While there appears to be no practical method for direct measurement of either velocity or altitude separately, it does appear possible to measure velocity-altitude ratio by comparing radiometric signals received from the terrain along the aircraft ground track. When combined with a radar altimeter, such a sensor could yield navigation data compatible with Army aircraft requirements. Microwave radiometry may also be the basis for direction sensing (to known landmarks) in high-flying aircraft or satellites. 相似文献
369.
John B. Rogerson Jr. 《Space Science Reviews》1963,2(5):621-652
A review is presented of the Orbiting Astronomical Observatories Program together with a detailed of the OAO spacecraft and the four astronomical instruments currently being developed for the first three observations. 相似文献
370.
D'Antonio R. A. Gaffney John E. 《IEEE transactions on aerospace and electronic systems》1968,(5):728-732
This paper describes a radio interferometer that can be employed for beaming and attitude determination. It differs from conventional interferometers in that it employs a carrier modulated by a pseudonoise sequence. This enables it to provide an unambiguous angular resolution of the signal source. 相似文献