VentureStar… reaping the benefits of the X-33 program

Major X-33 flight hardware has been delivered, and assembly of the vehicle is well underway in anticipation of its flight test program commencing in the summer of 1999. Attention has now turned to the operational VentureStar^TM, the first single-stage-to-orbit (SSTO) reusable launch vehicle. Activities are grouped under two broad categories: (1) vehicle development and (2) market/business planning, each of which is discussed. The mission concept is presented for direct payload delivery to the International Space Station and to low Earth orbit, as well as payload delivery with an upper stage to Geosynchronous Transfer Orbit (GTO) and other high energy orbits. System requirements include flight segment and ground segment. Vehicle system sizing and design status is provided including the application of X-33 traceability and lessons learned. Technology applications to the VentureStar^TM are described including the structure, propellant tanks, thermal protection system, aerodynamics, subsystems, payload bay and propulsion. Developing a market driven low cost launch services system for the 21st Century requires traditional and non-traditional ways of being able to forecast the evolution of the potential market. The challenge is balancing both the technical and financial assumptions of the market. This involves the need to provide a capability to meet market segments that in some cases are very speculative, while at the same time providing the financial community with a credible revenue stream. Furthermore, the market derived requirements need to be assessed so as not to impose unnecessary requirements on the vehicle design that add unreasonable cost to the development of the system, yet provides the right capabilities for new markets that could be triggered by dramatically lower space transportation prices.     

Electrical Charging of Volcanic Plumes

Many explosive terrestrial volcanic eruptions are accompanied by lightning and other atmospheric electrical phenomena. The plumes produced generate large perturbations in the surface atmospheric electric potential gradient and high charge densities have been measured on falling volcanic ash particles. The complex nature of volcanic plumes (which contain gases, solid particles, and liquid drops) provides several possible charging mechanisms. For plumes rich in solid silicate particles, fractoemission (the ejection of ions and atomic particles during fracture events) is probably the dominant source of charge generation. In other plumes, such as those created when lava enters the sea, different mechanisms, such as boiling, may be important. Further charging mechanisms may also subsequently operate, downwind of the vent. Other solar system bodies also show evidence for volcanism, with activity ongoing on Io. Consequently, volcanic electrification under different planetary scenarios (on Venus, Mars, Io, Moon, Enceladus, Tethys, Dione and Triton) is also discussed.     

Voyager photopolarimeter observations of Saturn and Titan

The Voyager 2 photopolarimeter experiment observed the intensity and polarization of scattered sunlight from the atmospheres of Saturn and Titan in the near-UV at 2640 Å and in the near-IR at 7500 Å. Measurements of Saturn's limb brightening and polarization at several phase angles up to 70° indicate that a significant optical depth of UV absorbers are present in the top 100 mbar of Saturn's atmosphere in the Equatorial Zone and north polar region, and possibly at other latitudes as well. UV absorbers are prominent in polar regions, suggesting that charged particle precipitation from the magnetosphere may be important in their formation.The whole-body polarization of Titan is strongly positive in both the UV and near IR. If spherical particles are responsible for the polarization, no single size distribution or refractive index can account for the polarization at both wavelengths. The model atmosphere proposed by Tomasko and Smith [1], characterized by a gradient in particle size with altitude, seems capable of explaining the Voyager observations. If non-spherical particles predominate, the Voyager observations place important constraints on their scattering properties.     

使用高温粘方法修理和替换内衬密封条

在大多数商用飞机使用高效率的涡轮风扇喷气发动机时代到来的同时,飞机维修人员也面临着新的挑战,即如何修理和替换发动机上的耐磨损内衬密封条,也称风扇轨道。装在涡轮喷气飞机上涡扇发动机,一般其装在前部的风扇由它位于初级涡轮后面的二级涡轮驱动,它的作用是增加发动机中心的气流,以减少燃油消耗并提供更大的推力。为了得到涡轮风扇发动机提供的高空气通过率,必须迫使尽量多的空气通过风扇,因此需要使风扇顶端到风扇罩内核之间的间隙尽可能地小。如果风扇叶片和发动机内罩都是金属结构,由温度升高或离心力引起的任何叶片长度膨胀都可能…     

The Cassini Ultraviolet Imaging Spectrograph Investigation

The Cassini Ultraviolet Imaging Spectrograph (UVIS) is part of the remote sensing payload of the Cassini orbiter spacecraft. UVIS has two spectrographic channels that provide images and spectra covering the ranges from 56 to 118 nm and 110 to 190 nm. A third optical path with a solar blind CsI photocathode is used for high signal-to-noise-ratio stellar occultations by rings and atmospheres. A separate Hydrogen Deuterium Absorption Cell measures the relative abundance of deuterium and hydrogen from their Lyman-α emission. The UVIS science objectives include investigation of the chemistry, aerosols, clouds, and energy balance of the Titan and Saturn atmospheres; neutrals in the Saturn magnetosphere; the deuterium-to-hydrogen (D/H) ratio for Titan and Saturn; icy satellite surface properties; and the structure and evolution of Saturn’s rings.This revised version was published online in July 2005 with a corrected cover date.     

Metabolic energy required for flight.

This paper reviews data available from U.S. and U.S.S.R. studies on energy metabolism in the microgravity of space flight. Energy utilization and energy availability in space seem to be similar to those on Earth. However, negative nitrogen balances in space in the presence of adequate energy and protein intakes and in-flight exercise, suggest that lean body mass decreases in space. Metabolic studies during simulated (bed rest) and actual microgravity have shown changes in blood glucose, fatty acids, and insulin levels, suggesting that energy metabolism may be altered during flight. Future research should focus on the interactions of lean body mass, diet, and exercise in space and their roles in energy metabolism during space flight.     

采用高温粘接方法修理和替换耐磨损内衬密封条

在许多商用飞机使用高效率的涡轮风扇喷气发动机的情况下,飞机维修人员面临着一个挑战,即如何修理和替换发动机上的耐磨损内衬密封条--风扇轨道.     

Ultraviolet-stimulated fluorescence and phosphorescence of aromatic hydrocarbons in water ice

A principal goal of astrobiology is to detect and inventory the population of organic compounds on extraterrestrial bodies. Targets of specific interest include the wealth of icy worlds that populate our Solar System. One potential technique for in situ detection of organics trapped in water ice matrices involves ultraviolet-stimulated emission from these compounds. Here, we report a preliminary investigation into the feasibility of this concept. Specifically, fluorescence and phosphorescence of pure benzene ice and 1% mixtures of benzene, toluene, p-xylene, m-xylene, and o-xylene in water ice, respectively, were studied at temperatures ranging from ～17 K up to 160 K. Spectra were measured from 200-500 nm (50,000-20,000 cm(-1)) while ice mixtures were excited at 248.6 nm. The temperature dependence of the fluorescence and phosphorescence intensities was found to be independent of the thermal history and phase of the ice matrix in all cases examined. All phosphorescent emissions were found to decrease in intensity with increasing temperature. Similar behavior was observed for fluorescence in pure benzene, while the observed fluorescence intensity in water ices was independent of temperature.     

X-ray and radio observations of the galaxy cluster 3C 129

The galaxy cluster 3C 129 contains two radio galaxies, the prototypical head tail radio galaxy 3C 129 and the weaker radio galaxy 3C 129.1. The tail of the first radio galaxy extends over more than 15′ across the sky. In this paper, we report on Chandra spectroscopy observations of the galaxy cluster, complemented by new and archival radio data taken with the Very Large Array (VLA) at 0.33, 1.4, 5, and 8 GHz and by HI-observations performed with the dominion radio astrophysical observatory (DRAO). We describe the Chandra results on the properties of the Intra-Cluster Medium (ICM) and discuss extended X-ray emission detected from the host galaxy of the radio galaxy 3C 129.1 and from the inner jet of the radio galaxy 3C 129. Finally, we report on the results of an ICM/radio plasma pressure balance study along the tail of the radio galaxy 3C 129.     

Galileo Ultraviolet Spectrometer experiment

The Galileo ultraviolet spectrometer experiment uses data obtained by the Ultraviolet Spectrometer (UVS) mounted on the pointed orbiter scan platform and from the Extreme Ultraviolet Spectrometer (EUVS) mounted on the spinning part of the orbiter with the field of view perpendicular to the spin axis. The UVS is a Ebert-Fastie design that covers the range 113–432 nm with a wavelength resolution of 0.7 nm below 190 and 1.3 nm at longer wavelengths. The UVS spatial resolution is 0.4 deg × 0.1 deg for illuminated disc observations and 1 deg × 0.1 deg for limb geometries. The EUVS is a Voyager design objective grating spectrometer, modified to cover the wavelength range from 54 to 128 nm with wavelength resolution 3.5 nm for extended sources and 1.5 nm for point sources and spatial resolution of 0.87 deg × 0.17 deg. The EUVS instrument will follow up on the many Voyager UVS discoveries, particularly the sulfur and oxygen ion emissions in the Io torus and molecular and atomic hydrogen auroral and airglow emissions from Jupiter. The UVS will obtain spectra of emission, absorption, and scattering features in the unexplored, by spacecraft, 170–432 nm wavelength region. The UVS and EUVS instruments will provide a powerful instrument complement to investigate volatile escape and surface composition of the Galilean satellites, the Io plasma torus, micro- and macro-properties of the Jupiter clouds, and the composition structure and evolution of the Jupiter upper atmosphere.