Necessary conditions of optimality are derived for trajectories whose structure is limited to climb, steady cruise, and descent segments. The performance function consists of the sum of fuel and time costs, referred to as direct operating cost (DOC). The state variable is range to go and the independent variable is energy. In this formulation a cruise segment always occurs at the optimum cruise energy for sufficiently large range. At short ranges (500 n. mi. and less) a cruise segment may also occur below the optimum cruise energy. The existence of such a cruise segment depends primarily on the fuel flow vs thrust characteristics and on thrust constraints. If thrust is a free control variable along with airspeed, it is shown that such cruise segments will not generally occur. If thrust is constrained to some maximum value in climb and to some minimum in descent, such cruise segments generally will occur. Computer calculations of typical short-range trajectories obtained about a 1% cost penalty for constraining the thrust.

  • Corporate Authors:

    Ames Research Center

    National Aeronautics and Space Administration
    Moffett Field, CA  United States  94035
  • Authors:
    • Erzberger, H
    • Lee, H
  • Publication Date: 1978-9

Media Info

  • Pagination: 39 p.

Subject/Index Terms

Filing Info

  • Accession Number: 00186517
  • Record Type: Publication
  • Source Agency: National Technical Information Service
  • Report/Paper Numbers: NASA-TM-78519, A-7592
  • Files: TRIS
  • Created Date: Feb 27 1979 12:00AM