In order to test the hypothesized existence of a powerful, thermal wind in active galactic nuclei, the hydrodynamic effects of such a wind on a model galactic interstellar medium (ISM) are investigated. The properties of several model ISMs are derived from observations of the Milky Way's ISM and those of nearby spiral and elliptical galaxies. The wind is assumed to be highly supersonic with spherical symmetry and constant mechanical luminosity, L(W). The propagation of the wind into the low density gas component of the ISM is studied using the Kompaneets approximation of a strong explosion in an exponential atmosphere. Flattened gas distributions are shown to experience "blow-out" of wind gas along the symmetry axis. The results show that for typical ISM gas pressures ( < 10⁻¹¹ ergs cm⁻³), the extent of the wind can range from 1 to 10 kpc for wind luminosities of 10⁴² to 10⁴⁶ ergs sec⁻¹ in a timescale of less than 10⁷ years. The steady state wind flow pattern and an estimate of the timescale required to reach a quasi-steady state are also determined. Next, the interaction of dense, interstellar clouds with the wind is investigated. The stability and mass loss of clouds in the wind are studied and it is proposed that clouds survive the encounter with the wind over large timescales ( >10⁷ yrs.). The physical structure and motion of the clouds are calculated, showing that large clouds (10³ solar masses) can be accelerated to velocities in excess of the galactic escape velocity. Finally, it is proposed that the Narrow Emission Line Regions (NELR) of active galaxies are the result of the interaction of active nuclei photons and a thermal wind on large, interstellar clouds. The physical state of the NELR is re-examined and shown to be compatible with this hypothesis. Arguments are presented to show that the NELR clouds must be massive and unable to be accelerated to NELR velocities by photon momentum alone. A Monte Carlo-type calculation is made to determine Narrow Emission Line profiles from an ensemble of photoionized interstellar clouds in the wind. These theoretical line profiles are shown to agree reasonably well with observed line profiles.

International Telemetering Conference Proceedings / October 25-28, 1993 / Riviera Hotel and Convention Center, Las Vegas, Nevada / Highly reliable data storage for satellites and spacecraft is a challenging technology. The space environment is a unique combination of many environmental factors which impact the reliability and even the very survival of electronic systems. The need for space qualified memory is becoming even more important with the advent of on-board data processing which requires rapid access to large data bases. This paper describes the unique environmental and design considerations that must be taken into account for a magnetic disk that is designed to operate for years in the space environment.

Thesis (Ph. D.)--Virginia Polytechnic Institute and State University, 1991. / Vita. Abstract. Includes bibliographical references (leaves 130-134). Also available via the Internet.

This thesis presents a study on possible genetic consequences of the exposure to the space environment during space missions The present study was undertaken in co-operation with the Canadian Space Agency, and involved the analysis of the lymphocyte samples taken from experienced cosmonauts and trainees. For the analysis of genotoxicity of the space environment, a T-lymphocyte hprt clonal assay has been employed. In order to distinguish between artefacts associated with this method and the spaceflight-related effects, we have conducted a series of in vitro reconstruction experiments. In these experiments we have analysed interactions between plating efficiency (PE) of T-lymphocytes and efficiency of mutant recovery. Using 12 pairs of independent wild type (WT) and mutant clones, we have demonstrated an inverse correlation between initial viability of the WT cells and survival of mutant cells (r = 0.3496, p < 0.05). Our data suggest that the presence of WT cells in the selection plates does suppress the recovery of mutants in HPRT assay. This effect is stronger in samples with high PE, and may be a source of large error in estimation of mutant frequencies (approx. 3-fold in the range of PEs from 10% to 60%), which is especially relevant when samples with different PEs are compared. Analysis of samples from cosmonauts was conducted in two experiments. The first experiment involved 5 samples taken in 1992 from cosmonauts who have completed spaceflights ranging in duration from 7 to 365 days. Hprt mutant frequencies (MF) in these samples were 2.5–5 times higher than the age-corrected values for healthy, unexposed subjects in Western countries (Tates et al., 1991; Branda et al., 1993), and 2-3-fold higher than those determined for unexposed individuals residing in Russia (Jones et al., 1995). The cosmonaut mutational spectrum differed from that of unexposed healthy subjects (p = 0.042), and showed a higher incidence of splicing errors, frameshifts, and complex mutations. Distribution of base substitutions was remarkably similar to that observed in Russian twins sampled at the same period (Curry et al., 1998), thus suggestive of possible environmental, diet, or life-style related exposures. The second study was conducted on samples taken 5 years later and involved trainees and a group of cosmonauts with more uniform (at least 6 months) and recent flight experience. Hprt MFs in both cosmonaut and trainee groups were virtually identical (17.2 ± 0.6 and 17.6 ± 4.7 × 10⁻⁶ respectively), and approximately 2-fold higher than in matching Western controls, although considerably lower than in our previous observations. Mutational spectra in both datasets were very similar to that observed in our earlier study, and were significantly different from spontaneous data (p = 0.031–0.038). Distribution of base substitutions, however, did not show any differences. Our data indicate that the space environment is not genotoxic at the hprt locus. At the same time, uniformly high MFs observed in all studied groups suggest that the level of the mutagenic burden in at least megalopolis areas of Russia may be considerably larger than in the West. Also, there are some indications of a possible restructuring of mutagenic burden in post-transitional Russia. / Graduate

The NASA Long Duration Exposure Facility (LDEF), a passive experimental satellite, was placed into low-Earth orbit by the Shuttle Challenger in April 1984. The LDEF spent an unprecedented 69 months in space. The flight and recovery of the LDEF has provided a wealth of information on the long-term space environmental effects of a variety of materials exposed to the low-Earth orbit environment. Surface characterization of LDEF materials included polymers, composites, thermal control paints, and aluminum. X-ray photoelectron spectroscopy (XPS}, Auger electron spectroscopy (AES), scanning electron microscopy (SEM), and contact angle analysis were used to document changes in both the surface composition and surface chemistry of these materials. Detailed XPS analysis of the polymer systems, such as Kapton®, polyimide polysiloxane copolymers, and fluorinated ethylene propylene thermal blankets on the backside of the LDEF revealed significant changes in both the surface composition and surface chemistry as a result of exposure to the low-Earth orbit environment. Polymer systems such as Kapton®, polyimide polysiloxane copolymers, and polysulfone showed a common trend of decreasing carbon content and increasing oxygen content with respect to the control sample. Carbon ls curve fit XPS analysis of the composite samples, in conjunction with SEM photomicrographs, revealed significant ablation of the polymer matrix resin to expose the carbon fibers of the composite during exposure to the space environment. Surface characterization of anodized aluminum tray clamps, which were located at regular intervals over the entire LDEF frame, has provided the first results to evaluate the extent of contamination with respect to position on the LDEF. The XPS results clearly showed that the amount and state of both silicon and fluorine contamination were directly dependent upon the position of the tray clamp on the LDEF. / M.S.

The space environment contains many harsh characteristics that are harmful to spacecraft and threaten the success of space missions. Atomic oxygen (AO) and outgassing are among the chief concerns that spacecraft engineers must design for in order to ensure the safety of a spacecraft. AO is monatomic oxygen (O1) that is created when Ultraviolet (UV) radiation photochemically disassociates diatomic oxygen (O2) in space. AO is the dominant atmospheric constituent between 175 and 600 km, and is a great concern in low earth orbits. Orbital AO has an average impact energy of 4.5 ± 1 eV with orbiting spacecraft and is also very reactive; this makes AO very corrosive to spacecraft materials. Outgassing is the process by which trapped and adsorbed gases are expelled from materials. The high temperatures and low pressure of the spacecraft environment exacerbate the process of outgassing. Outgassing is problematic for spacecraft because outgassed material can condense on sensitive surfaces such as optical and thermal surfaces, or the material can create clouds that impede sensors ability to observe their target. While it has been shown that many aspects of the spacecraft environment act synergistically together to further degrade spacecraft performance, there is very little information and data available on the interactions between AO and outgassing. Cal Poly’s Space Environments Lab is equipped with an AO simulation vacuum chamber (MAX) and an outgas testing chamber (Micro-VCM) which is capable of testing materials for total mass loss (TML) and collected volatile condensable mass (CVCM) outgassing values. MAX and Micro-VCM were used in tandem to test different spacecraft materials in order to determine if AO exposure had any effect on the respective materials TML and CVCM values. Prior to conducting testing, Micro-VCM was refurbished and validated since it was recently donated to Cal Poly and was not in working order upon arrival. Three Sheldahl materials were tested: aluminum coated 1.0 mil Kapton tape, 2.0 mil Kapton film coated with ITO on one side and aluminum on the other, and 2.0 Kapton film coated with aluminum. The materials were exposed to an average AO fluence of 1.33 ± 0.130 × 1021 atoms/cm2 for AO testing. The TML and CVCM results from four of the six tests did not show any significant changes between AO samples and control samples, partially due to large error bars that stem from using a semi-microbalance instead of a full microbalance. However, the AO exposed ITO-Kapton-Al did show an increase in TML from -0.03 ± 0.09% to 0.19 ± 0.08% for one procedure, while the aluminum Kapton tape CVCM decreased from 0.81 ± 0.12% to 0.63 ± 0.12% for another procedure. These results show that two materials exhibited a change in their outgassing properties after AO exposure. More testing on the subject is warranted and should be conducted in order to collect more data points and begin defining trend lines that can further describe the effects of AO on outgassing.

Graduation date: 2004

Thesis (Ph. D.)--University of Texas at Austin, 2006. / Vita. Includes bibliographical references.

Thesis (M.S. in Electrical Engineering)--Naval Postgraduate School, December 2009. / Thesis Advisor(s): Kragh, Frank E.; Loomis, Herschel. "December 2009." Description based on title screen as viewed on January 27, 2010. Author(s) subject terms: data compression, signal analysis, Software Defined Radio (SDR), system generator, Fast Fourier Transform (FFT), Field Programmable Gate Array (FPGA), Xilinx, Virtex (TM), error detection, parity, space-based computing. Includes bibliographical references (p. 101-102). Also available in print.

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