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Crull, T. J.

Publications and source records attributed to Crull, T. J..

Space shuttle descent design: From development to operations

The descent guidance system, the descent trajectories design, and generating of the associated flight products are discussed. The programs which allow the successful transitions from development to STS operations, resulting in reduced manpower requirements and compressed schedules for flight design cycles are addressed. The topics include: (1) continually upgraded tools for the job, i.e., consolidating tools via electronic data transfers, tailoring general purpose software for needs, easy access to tools through an interactive approach, and appropriate flexibility to allow design changes and provide growth capability; (2) stabilizing the flight profile designs (I-loads) in an uncertain environment; and (3) standardizing external interfaces within performance and subsystems constraints of the Orbiter.

Crull, T. J.

RTLS entry ranging analysis

Definition of the ranging capability of a mission 3A return-to-launch-site entry is reported. The limits on downrange and crossrange are established at the initiation of RTLS entry so that terminal area energy management interface conditions were achieved satisfactorily. The downrange and crossrange limits were defined for both nominal RTLS entry conditions and a composite set of dispersed RTLS entry conditions. The results indicate a wide range of acceptable downrange and crossrange positions are available at RTLS entry initiation for nominal conditions. This is greatly reduced when dispersions are considered. For dispersed RTLS entry conditions, an 18 nautical mile range of acceptable downranges is available at zero crossrange.

Crull, T. J.

RTLS entry load relief parameter optimization

The results are presented of a study of a candidate load relief control law for use during the pullup phase of Return-to-Launch-Site (RTLS) abort entries. The control law parameters and cycle time which optimized performance of the normal load factor limiting phase (load relief phase) of an RTLS entry are examined. A set of control law gains, a smoothing parameter, and a normal force coefficient curve fit are established which resulted in good load relief performance considering the possible aerodynamic coefficient uncertainties defined. Also, the examination of various guidance cycle times revealed improved load relief performance with decreasing cycle time. A .5 second cycle provided smooth and adequate load relief in the presence of all the aerodynamic uncertainties examined.

Crull, T. J.