@book{Ley1998,
  author    = {Ley, Wilfried},
  title     = {Internationale Raumstation : Konfiguration, Betrieb und Nutzung ; Gemeinschaftsveranstaltung der FH Aachen, der DGLR und des DLR / 11. Raumfahrt-Kolloquium an der Fachhochschule Aachen, 26. November 1998. / Ley, Wilfried [Hrsg.]},
  publisher = {DGLR},
  address   = {Bonn},
  isbn      = {3-932182-04-9},
  pages     = {VIII, 208 S. : Ill., graph. Darst., 30 cm},
  year      = {1998},
  language  = {de}
}
@book{Ley1997,
  author    = {Ley, Wilfried},
  title     = {Raumfahrtmissionen zur Erkundung des Sonnensystems : Gemeinschaftsveranstaltung der FH Aachen, der DGLR und des DLR / 10. Raumfahrt-Kolloquium an der Fachhochschule Aachen, 5. November 1997 / Ley, Wilfried [Hrsg.]},
  publisher = {DGLR},
  address   = {Bonn},
  isbn      = {3-922010-99-7},
  pages     = {VIII, 251 S. : Ill., graph. Darst., 30 cm},
  year      = {1997},
  language  = {de}
}
@book{Ley1995,
  author    = {Ley, Wilfried},
  title     = {Tr{\"a}gersysteme : Gemeinschaftsveranstaltung der FH Aachen und der DGLR / 8. Raumfahrt-Kolloquium an der Fachhochschule Aachen, 9. November 1995 / Ley, Wilfried [Hrgs.]},
  publisher = {DGLR},
  address   = {Bonn},
  isbn      = {3-922010-92-X},
  pages     = {VII, 245 S. : Ill., graph. Darst.},
  year      = {1995},
  language  = {de}
}
@book{Ley1990,
  author    = {Ley, Wilfried},
  title     = {Seilgefesselte Raumflugk{\"o}rper, -Tethertechnik- : Gemeinschaftsveranstaltung der FH Aachen und der DGLR ... / 3. Raumfahrt-Kolloquium an der Fachhochschule Aachen, 13. Dezember 1990. [Wiss. Programmleitung: W. Ley, W. Hallmann]},
  publisher = {DGLR},
  address   = {Bonn},
  isbn      = {3-922010-59-8},
  pages     = {Getr. Z{\"a}hl. : graph. Darst.},
  year      = {1990},
  language  = {de}
}
@book{Ley1982,
  author    = {Ley, Wilfried},
  title     = {Bewertung von Solarkollektormessungen unter natuerlichen und simulierten Bedingungen},
  publisher = {Inst. f. Raumsimulation},
  address   = {K{\"o}ln},
  pages     = {190 Seiten, 133 Bilder, 19 Tabellen, 43 Quellen},
  year      = {1982},
  language  = {de}
}
@book{Ley1988,
  author    = {Ley, Wilfried},
  title     = {Handbuch der Raumfahrttechnik : Grundlagen - Nutzung, Raumfahrtsysteme - Produktsicherung u. Produktmanagement / Willi Hallmann; Wilfried Ley},
  publisher = {Hanser},
  address   = {M{\"u}nchen [u.a.]},
  isbn      = {3446151303},
  pages     = {XVIII, 792 S : Ill., graph. Darst.},
  year      = {1988},
  language  = {de}
}
@book{Ley2008,
  author    = {Ley, Wilfried},
  title     = {Handbuch der Raumfahrttechnik / Ley, Wilfried ; Wittmann, Klaus ; Hallmann, Willi [Hrsg.]},
  publisher = {Hanser},
  address   = {M{\"u}nchen},
  isbn      = {978-3-446-41185-2},
  pages     = {814 S. : zahlr. Ill., graph. Darst.},
  year      = {2008},
  language  = {de}
}
@article{LeyPlescherScholzetal.2007,
  author    = {Ley, Wilfried and Plescher, Engelbert and Scholz, Artur and Piepenbrock, Johannes},
  title     = {COMPASS-1 picosatellite project / Ley, Wilfried ; Plescher, Engelbert ; Scholz, Artur ; Piepenbrock, Johannes},
  series = {Small satellites for earth observation : digest of the 6th International symposium of the International Academy of Astronautics, Berlin, April 23 - 26, 2007 / ed. by Rainer Sandau; Hans-Peter R{\"o}ser; Arnoldo Valenzuela},
  journal   = {Small satellites for earth observation : digest of the 6th International symposium of the International Academy of Astronautics, Berlin, April 23 - 26, 2007 / ed. by Rainer Sandau; Hans-Peter R{\"o}ser; Arnoldo Valenzuela},
  publisher = {Wissenschaft und Technik Verl.},
  address   = {Berlin},
  isbn      = {9783896855718},
  pages     = {147 -- 150},
  year      = {2007},
  language  = {en}
}
@book{LeyWittmannHallmann2009,
  author    = {Ley, Wilfried and Wittmann, Klaus and Hallmann, Willi},
  title     = {Handbook of space technology},
  publisher = {Wiley},
  address   = {Chichester},
  isbn      = {978-0-470-69739-9},
  pages     = {XIII, 882 S. : Ill., graph. Darst.},
  year      = {2009},
  language  = {en}
}
@inproceedings{LoebSchartnerDachwaldetal.2011,
  author    = {Loeb, Horst W. and Schartner, Karl-Heinz and Dachwald, Bernd and Ohndorf, Andreas and Seboldt, Wolfgang},
  title     = {An Interstellar - Heliopause mission using a combination of solar/radioisotope electric propulsion},
  series = {Presented at the 32nd International Electric Propulsion Conference},
  booktitle = {Presented at the 32nd International Electric Propulsion Conference},
  pages     = {1 -- 7},
  year      = {2011},
  abstract  = {There is common agreement within the scientific community that in order to understand our local galactic environment it will be necessary to send a spacecraft into the region beyond the solar wind termination shock. Considering distances of 200 AU for a new mission, one needs a spacecraft travelling at a speed of close to 10 AU/yr in order to keep the mission duration in the range of less than 25 yrs, a transfer time postulated by ESA.Two propulsion options for the mission have been proposed and discussed so far: the solar sail propulsion and the ballistic/radioisotope electric propulsion. As a further alternative, we here investigate a combination of solar-electric propulsion and radioisotope-electric propulsion. The solar-electric propulsion stage consists of six 22 cm diameter "RIT-22"ion thrusters working with a high specific impulse of 7377 s corresponding to a positive grid voltage of 5 kV. Solar power of 53 kW BOM is provided by a light-weight solar array. The REP-stage consists of four space-proven 10 cm diameter "RIT-10" ion thrusters that will be operating one after the other for 9 yrs in total. Four advanced radioisotope generators provide 648 W at BOM. The scientific instrument package is oriented at earlier studies. For its mass and electric power requirement 35 kg and 35 W are assessed, respectively. Optimized trajectory calculations, treated in a separate contribution, are based on our "InTrance" method.The program yields a burn out of the REP stage in a distance of 79.6 AU for a usage of 154 kg of Xe propellant. With a C3 = 45,1 (km/s)2 a heliocentric probe velocity of 10 AU/yr is reached at this distance, provided a close Jupiter gravity assist adds a velocity increment of 2.7 AU/yr. A transfer time of 23.8 yrs results for this scenario requiring about 450 kg Xe for the SEP stage, jettisoned at 3 AU. We interpret the SEP/REP propulsion as a competing alternative to solar sail and ballistic/REP propulsion. Omiting a Jupiter fly-by even allows more launch flexibility, leaving the mission duration in the range of the ESA specification.},
  language  = {en}
}