Reduced Gravity Landing Research Vehicle Design

Human and robotic missions beyond low earth orbit (LEO) are key components of NASA\u27s currently emerging strategy for space exploration. These missions will inevitably include humancrewed lunar and planetary surface landings. Trips to near-earth asteroids are also in the incipient planning stages. A permanent presence on the surface of an extra terrestrial body like Mars or the Moon will require many landings by both human-crewed and robotic spacecraft. Planetary and lunar surface landings are inherently dangerous undertakings, and successful landings are indeed rare events. Since the end of the Apollo era with the completion of the Apollo 17 mission in December 1972, only five successful soft-landings have been achieved on the lunar surface, with the last landing being Luna 24 in 1976. During that same period there have been only six successful Martian surface landings with nearly as many failures. Although surface geology was a secondary consideration in selecting the Apollo landing sites, a primary consideration was crew safety and mission success. Thus all of the Apollo landing sites occurred in a narrow equatorial strip, near the lunar basaltic plains or Maria. These landing sites were mostly free of significant surface hazards. Martian surface landing sites have been selected for similar benign surface terrain characteristics. With a long term human extra-terrestrial surface presence, scientific objectives will become increasingly more important, and the landing site terrain will become increasingly more diverse. Correspondingly, as these surface landing sites become more interesting, they will also become more hazardous. Thus, the development of a research and testing platforms allowing pin-point autonomous landing systems to be evaluated, refined, and matured is essential. Only a free flying-platform can develop surface landing technologies to a sufficient technology readiness level (TRL) to be considered for ultra-expensive, extra-terrestrial missions. Additionally, as was demonstrated during the Apollo era, the development of a flying human-pilot training vehicle for extra-terrestrial surface landings will become a long-term exploration necessity

In Situ Flame Structure Imaging of Composite Propellants using High-Speed Planar Laser-Induced Fluorescence

Ammonium perchlorate (AP) is the most commonly used oxidizer in solid rocket propellants due to its availability, high oxygen balance, and combustion characteristics. Models of AP composite propellants have been made since the 1950s and have become highly advanced in recent years. However, experimental data have not kept pace, and the data required to validate models has lagged behind the models themselves. Recently, high-speed OH planar laser-induced fluorescence (PLIF) imaging has been applied to AP composite propellants to determine how microscale propellant flame structure varies with propellant formulation and pressure. Propellants with monomodal AP particle size distributions, changing coarse-to-fine AP particle size ratios, and different sizes and locations of burning rate catalysts have been investigated to determine the effect of propellant formulation on burning rate. It is found that AP particle size, propellant formulation, and pressure have a definite effect on propellant flame structure and burning rate. All propellants with AP particles below about 150 μm display similar flame structures for the pressures investigated (0.1-0.7 MPa). For propellants with AP particles larger than about 150 μm, all propellants burning at 1 atm display jet-like flames above individual coarse AP crystals. If the coarse AP concentration is high enough, group diffusion flames are seen where many coarse AP particles burn with one diffusion flame. At elevated pressures lifted arched diffusion flames are often seen; however, the circumstances under which the lifted flames develop depend on the propellant formulation. Burning rate was seen to increase as the average AP particle size decreased, and vice-versa

Experimental investigation of the freely cooling granular gas

Using diamagnetically levitated particles we investigate the dynamics of the freely cooling granular gas. At early times we find good agreement with Haff's law, where the time scale for particle collisions can be determined from independent measurements. At late times, clustering of particles occurs. This can be included in a Haff-like description taking into account the decreasing number of free particles. With this a good description of the data is possible over the whole time range.Comment: 4 pages, 5 figure

Factors Associated With the Development of Chronic Kidney Disease in Children With Congenital Anomalies of the Kidney and Urinary Tract

Congenital anomalies of the kidney and urinary tract (CAKUT) are the most common cause of end-stage renal disease in children and adolescents. The diversity of the malformations summarized by CAKUT is high and there are numerous associated syndromes. The genetic background of these malformations remains unknown in the majority of cases. The aim of this study was to evaluate factors associated with the development of chronic kidney disease (CKD) and underlying genetic aberrations in children and adolescents with CAKUT. For this purpose, data from patients with CAKUT presented at the pediatric nephrology outpatient clinic were analyzed in a cross-sectional single-center study. Among the 405 patients, the commonest findings related to CAKUT were renal hypoplasia/dysplasia (65%), followed by hydronephrosis (43%). Forty-four percent of the patients were suffering from CKD, 6% were ranked as end-stage renal disease. In the univariate analysis, male gender and premature birth were associated with higher CKD stages (p = 0.004 resp. p < 0.001). Children with an abnormal prenatal ultrasound had more often a glomerular filtration rate of <30 ml/min/1.73 m2 (p = 0.004). Patients with urinary tract infections as first symptom whereas had significant lower CKD stages (p = 0,006). In the multivariate analysis, premature birth (p = 0.033) and urinary tract infection as the first symptom (p = 0.043) were significantly associated with CKD stage ≥ II. Among the 16% of the children who have undergone genetic analyses the most frequent genetic aberration was a mutation in HNF1β-gene. These results can be used for the care of patients with CAKUT subject to factors associated with developing CKD

Estabilidad de las técnicas sociométricas en la etapa de educación infantil

Segones Jornades de Foment de la Investigació de la FCHS (Any 1996-1997

STRUCTURAL DETERMINATION OF THE CHIRAL MOLECULE 2-BROMO-1,1,1,3-TETRAFLUOROETHANE BY CP-FTMW SPECTROSCOPY

\begin{wrapfigure}{r}{0pt} \includegraphics[scale=0.2]{2bromotetismspic.eps} \end{wrapfigure} Dipole forbidden, nuclear electric quadrupole allowed transitions in microwave spectroscopy are manifested through a linkage in off-diagonal components of the quadrupole coupling tensor. It is hypothesized that these transitions, due to their transition pathways, could possibly be used to differentiate chirality in a microwave three-wave mixing (3WM)-type experiment. In order to test this hypothesis, 2-bromo-1,1,1,3-tetrafluoroethane was chosen, as it is chiral, possesses a large quadrupolar nucleus and is heavy enough to generate the needed mixing to bring about these forbidden transitions. Because this the first known rotational study of the molecule, traditional rotational spectroscopy utilizing CP-FTMW techniques was performed first. This presentation will describe the collection of spectra, structural analysis, and observed dipole forbidden transitions of the title molecule