3,986 research outputs found

    Radiosondes for Characterizing the Martian Atmosphere

    Get PDF
    The National Weather Service (NWS) releases approximately 75,000 radiosondes each year to measure pressure, altitude, temperature, relative humidity, wind and cosmic radiation [1]. The data obtained from these measurements have led to a more thorough understanding of the Earth s lower atmosphere. On the contrary, there have been only six fully successful landings on Mars, and there is much less known about the variations in winds, density, etc., in the mid-regions of the Martian atmosphere (see Fig. 1). This data is vital to understanding Martian weather and the development of Mars landers for larger payloads [2,3,4]. Mars has too much atmosphere to land like is done on the moon, and too little atmosphere to land like is done on Earth. It is suggested that radiosondes could be added as secondary payloads on Mars missions and used to map physical properties in the different regions of the Martian atmosphere

    Fission Systems for Mars Exploration

    Get PDF
    Fission systems are used extensively on earth, and 34 such systems have flown in space. The energy density of fission is over 10 million times that of chemical reactions, giving fission the potential to eliminate energy density constraints for many space missions. Potential safety and operational concerns with fission systems are well understood, and strategies exist for affordably developing such systems. By enabling a power-rich environment and highly efficient propulsion, fission systems could enable affordable, sustainable exploration of Mars

    Structure and variation of human ribosomal DNA: molecular analysis of cloned fragments

    Full text link
    Eco-RI-A fragments of the human ribosomal RNA gene family from two types of tissue and three individuals were cloned in [lambda] vectors and compared by restriction enzyme digestion and electron microscopy. The EcoRI fragment A contains (i) 0.2 kb of the 3' end of the 18S rDNA, (ii) 2.5 kb of internal transcribed spacer and the 5.8S rDNA, and (iii) 4.6 kb of the 28S rDNA gene. All of the six cloned rDNA fragments isolated are identical by these analyses. Moreover, all contain a HincII site that is absent in about 50% of the rDNA identified by genomic blotting. Polymorphism in the nontranscribed spacer rDNA was studied on genomic blots of BamHI-digested DNA, using the 3' end of the 28S rDNA as a probe. The boundaries between the 18S rDNA, internal transcribed spacer, 28S rDNA, and external nontranscribed spacer were determined by R-loop analysis, further defining the organization of the ribosomal RNA precursor.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/24168/1/0000426.pd

    Design and Analysis of a Turbopump for a Conceptual Expander Cycle Upper-Stage Engine

    Get PDF
    This viewgraph presentation reviews the motivation for the study, the numerical method used, the numerical simulations of the vaneless diffuser and vaned diffuser. It also reviews the conclusions from the stud
    • …
    corecore