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  • Spacecraft Propulsion and Power  (9)
  • GEOPHYSICS  (4)
  • 36.10.Gv  (3)
  • 11
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    A Preliminary Model for Spacecraft Propulsion Performance Analysis Based on Nuclear Gain and Subsystem Mass-Power Balances (1999)
    In:  Other Sources
    Details
    Publication Date: 2019-07-13
    Description: Rapid transportation of human crews to destinations throughout the solar system will require propulsion systems having not only very high exhaust velocities (i.e., I(sub sp) 〉= 10(exp 4) to 10(exp 5) sec) but also extremely low mass-power ratios (i.e., alpha 〈= 10(exp -2) kg/kW). These criteria are difficult to meet with electric propulsion and other power-limited systems, but may be achievable with propulsion concepts that use onboard power to produce a net gain in energy via fusion or some other nuclear process. This paper compares the fundamental performance of these gain-limited systems with that of power-limited systems, and determines from a generic power balance the gains required for ambitious planetary missions ranging up to 100 AU. Results show that energy gain reduces the required effective mass-power ratio of the system, thus enabling shorter trip times than those of power-limited concepts.
    Keywords: Spacecraft Propulsion and Power
    Type: Jun 20, 1999; Los Angeles, CA; United States
    Format: text
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    NASA TECHNICAL REPORTS
  • 12
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    Consistency of rocket and radar electron density observations - Implications about the anisotropy of mesospheric turbulence (1990)
    In:  Other Sources
    Details
    Publication Date: 2019-07-12
    Description: Quantitative comparisons are made between rocketborne measurements of electron density fluctuations and simultaneous 53.5 MHz radar measurements obtained during the Summer in Northern Europe campaign. Rocketborne radar reflectivity results are of the order of 10 dB greater than would be expected in the case of isotropic electron density fluctuations. There results can be reconciled by assuming isotropic turbulence. A relation is derived between rocket and radar observations which covers the entire range from isotropic turbulent scatter to Fresnel scatter at horizontal density stratifications. The anisotropy is greatest at heights where the electron density displays deep 'bite-outs'.
    Keywords: GEOPHYSICS
    Type: Journal of Atmospheric and Terrestrial Physics (ISSN 0021-9169); 52; 855-873
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    NASA TECHNICAL REPORTS
  • 13
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    The Performance Constraints of Gain-Limited Propulsion Systems (1999)
    In:  Other Sources
    Details
    Publication Date: 2019-07-17
    Description: Rapid transportation of human crews to destinations throughout the solar system will require propulsion systems having not only very high exhaust velocities (i.e., I(sub sp) greater or equal to 10(exp 4) to 10(exp 5) sec) but also extremely low mass-power ratios (i.e., alpha less than or equal to 10(exp -2) kg/kW). These criteria are difficult to meet with electric propulsion and other power-limited systems, but may be achievable with propulsion concepts that use onboard power to produce a net gain in energy via fusion or some other nuclear process. This paper compares the fundamental performance of these gain-limited systems with that of power-limited systems, and determines from a generic power balance the gains required for ambitious planetary missions ranging up to 100 AU. Results show that energy gain reduces the required effective mass-power ratio of the system, thus enabling shorter trip times than those of power-limited concepts.
    Keywords: Spacecraft Propulsion and Power
    Type: Jun 20, 1999 - Jun 25, 1999; Los Angeles, CA; United States
    Format: text
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    NASA TECHNICAL REPORTS
  • 14
    Electronic Resource
    Electronic Resource
    Absolute pionic x-ray intensities in Mg and Fe (1991)
    Springer
    The European physical journal 341 (1991), S. 101-105 
    Details
    ISSN: 1434-601X
    Keywords: 36.10.Gv
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Absolute pionic x-ray intensities have been measured for Mg and Fe. The accuracy achieved was 2% of the line intensity for the most prominent transitions. In the Balmer series of Mg and the Paschen series of Fe the crossover transitions were found to be even more attenuated than the transitions between circular states, as deduced, for example, by comparison with muonic atoms; no crossover transitions were observed in the Fe Balmer series. According to cascade calculations based on the experimental intensities more than half of the pions are absorbed in Fe already from levels with principal quantum numbern〉17 by strong interaction.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01281280
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    Paper (German National Licenses)
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  • 15
    Electronic Resource
    Electronic Resource
    Measurement of the 4f strong interaction level width in light antiprotonic atoms (1986)
    Springer
    The European physical journal 325 (1986), S. 261-265 
    Details
    ISSN: 1434-601X
    Keywords: 36.10.Gv ; 13.75.Cs
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The yields of the atomic 4→3 transitions in antiprotonic14N,16,17,18O,19F, and23Na were measured at the CERN antiproton facility, LEAR. From these, the widths Γup of the 4f levels were determined to be 136±19meV (14N); 603±22 meV (16O); 731±35 meV (17O); 795±23 meV (18O); 2.79±0.16 eV (19F); and 23.8±7.4 eV (23Na).
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01294606
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  • 16
    Electronic Resource
    Electronic Resource
    First direct observation of strong interaction spin-orbit effects in antiprotonic atoms (1988)
    Springer
    The European physical journal 329 (1988), S. 235-241 
    Details
    ISSN: 1434-601X
    Keywords: 36.10.Gv ; 13.75.Cs
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The strong ¯p-nucleus spin-orbit interaction was investigated in a measurement of the strong-interaction effects of the 9→8 transition in ¯p 174Yb at the Low-Energy Antiproton Ring (LEAR) at CERN. This measurement was part of an experimental programme where, for the first time, the fine-structure components of the last observable X-ray transition in a ¯p atom, which carries information on the strong ¯p-nucleus interaction, were resolved and studied individually. The observed splitting ΔE exp=2408±26 eV consists of the electromagnetic fine-structure splitting ΔE FS=2350 eV and an additional splitting Δɛ=58±26 eV. In addition, one finds a significant difference in the level widths of Δ=195±59 eV with the larger value⇊=1216±41 eV for the lower fine-structure level. This experiment follows an earlier measurement on ¯p 138Ba, where the transition 8→7 is influenced by the strong interaction. In this case, however, the fine-structure components could not be resolved. The results for174Yb may be attributed to a spin-orbit (LS) term in the complex strong-interaction potential.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01283780
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