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  • Other Sources  (17)
  • AIRCRAFT
  • ASTRODYNAMICS
  • BIOTECHNOLOGY
  • COMPUTERS
  • SPACE VEHICLES
  • 1990-1994  (11)
  • 1970-1974  (6)
  • 1
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    Orbit/deorbit analysis for a Mars rover and sample return mission (1990)
    In:  Other Sources
    Details
    Publication Date: 2011-08-19
    Keywords: ASTRODYNAMICS
    Type: Journal of Spacecraft and Rockets (ISSN 0022-4650); 27; 425-432
    Format: text
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    NASA TECHNICAL REPORTS
  • 2
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    Aerobraking for capture into Martian orbit (1990)
    In:  CASI
    Details
    Publication Date: 2013-08-31
    Description: A summary is given of several studies into problems associated with aerobraking a manned vehicle into a Martian capture orbit. The problems investigated are the establishment of entry flight path angle windows that allow aerocapture; the determination of the sensitivity of the entry trajectory to initial flight path angle; the determination of the effect on aerocapture of the assumed Martian atmosphere model; and the determination of the effect of random atmosphere disturbances on adaptive guidance systems that may be used for aerocapture. As a result of investigating the above problem areas, entry windows were established for three different vehicle configurations. Sensitivities to changes in initial flight path angle were also obtained for these three configurations. One configuration was chosen to determine the effect of Martian atmospheric model changes and random variations of density within a specific atmospheric model. Of particular interest was the effect of random density variations on adaptive guidance techniques. The effect of entry velocity on the size of the entry window was also examined.
    Keywords: ASTRODYNAMICS
    Type: NASA, Goddard Space Flight Center, Flight Mechanics(Estimation Theory Symposium, 1990; p 491-510
    Format: application/pdf
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    NASA TECHNICAL REPORTS
  • 3
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    Evaluation of a stall-flutter spring-damper pushrod in the rotating control system of a CH-54B helicopter (1974)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: Results of a design and flight test program conducted to define the effect of rotating pushrod damping on stall-flutter induced control loads are presented. The CH-54B helicopter was chosen as the test aircraft because it exhibited stall induced control loads. Damping was introduced into the CH-54B control system by replacing the standard pushrod with spring-damper assemblies. Design features of the spring-damper are described and the results of a dynamic analysis are shown which define the pushrod stiffness and damping requirements. Flight test measurements taken at 47,000 lb gross weight with and without the damper are presented. The results indicate that the spring-damper pushrods reduced high frequency, stall-induced rotating control loads by almost 50%. Fixed system control loads were reduced by 40%. Handling qualities in stall were unchanged, as expected.
    Keywords: AIRCRAFT
    Type: NASA. Ames Res. Center Rotorcraft Dyn.; p 223-232
    Format: application/pdf
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  • 4
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    The MSFC UNIVAC 1108 EXEC 8 simulation model (1972)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: A model is presented which simulates the MSFC Univac 1108 multiprocessor system. The hardware/operating system is described to enable a good statistical measurement of the system behavior. The performance of the 1108 is evaluated by performing twenty-four different experiments designed to locate system bottlenecks and also to test the sensitivity of system throughput with respect to perturbation of the various Exec 8 scheduling algorithms. The model is implemented in the general purpose system simulation language and the techniques described can be used to assist in the design, development, and evaluation of multiprocessor systems.
    Keywords: COMPUTERS
    Type: NASA-CR-61379
    Format: application/pdf
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  • 5
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    Discrete approximations to optimal trajectories using direct transcription and nonlinear programming (1990)
    In:  Other Sources
    Details
    Publication Date: 2019-07-13
    Description: A recently developed method for solving optimal trajectory problems uses a piecewise-polynomial representation of the state and control variables, enforces the equations of motion via a collocation procedure, and thus approximates the original calculus-of-variations problem with a nonlinear-programming problem, which is solved numerically. This paper identifies this method as a direct transcription method and proceeds to investigate the relationship between the original optimal-control problem and the nonlinear-programming problem. The discretized adjoint equation of the collocation method is found to have deficient accuracy, and an alternate scheme which discretizes the equations of motion using an explicit Runge-Kutta parallel-shooting approach is developed. Both methods are applied to finite-thrust spacecraft trajectory problems, including a low-thrust escape spiral, a three-burn rendezvous, and a low-thrust transfer to the moon.
    Keywords: ASTRODYNAMICS
    Type: AIAA PAPER 90-2963 , AIAA/AAS Astrodynamics Conference; Aug 20, 1990 - Aug 22, 1990; Portland, OR; United States
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  • 6
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    Optimal finite-thrust spacecraft trajectories using collocation and nonlinear programming (1990)
    In:  Other Sources
    Details
    Publication Date: 2019-07-13
    Description: A new method is described for the determination of optimal spacecraft trajectories in an inverse-square field using finite, fixed thrust. The method employs a recently developed optimization technique which uses a piecewise polynomial representation for the state and controls, and collocation, thus converting the optimal control problem into a nonlinear programming problem, which is solved numerically. This technique has been modified to provide efficient handling of those portions of the trajectory which can be determined analytically, i.e., the coast arcs. Among the problems that have been solved using this method are optimal rendezvous and transfer (including multirevolution cases) and optimal multiburn orbit insertion from hyperbolic approach.
    Keywords: ASTRODYNAMICS
    Type: AAS PAPER 89-350 , AAS/AIAA Astrodynamics Conference 1989; Aug 07, 1989 - Aug 10, 1989; Stowe, VT; United States
    Format: text
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  • 7
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    Outer planet mission guidance and navigation for spinning spacecraft (1974)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: The orbit determination accuracies, maneuver results, and navigation system specification for spinning Pioneer planetary probe missions are analyzed to aid in determining the feasibility of deploying probes into the atmospheres of the outer planets. Radio-only navigation suffices for a direct Saturn mission and the Jupiter flyby of a Jupiter/Uranus mission. Saturn ephemeris errors (1000 km) plus rigid entry constraints at Uranus result in very high velocity requirements (140 m/sec) on the final legs of the Saturn/Uranus and Jupiter/Uranus missions if only Earth-based tracking is employed. The capabilities of a conceptual V-slit sensor are assessed to supplement radio tracking by star/satellite observations. By processing the optical measurements with a batch filter, entry conditions at Uranus can be controlled to acceptable mission-defined levels (+ or - 3 deg) and the Saturn-Uranus leg velocity requirements can be reduced by a factor of 6 (from 139 to 23 m/sec) if nominal specified accuracies of the sensor can be realized.
    Keywords: ASTRODYNAMICS
    Type: NASA-CR-136764
    Format: application/pdf
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  • 8
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    The effects of trajectory characteristics on scientific objectives for major planetary orbiters. (1972)
    In:  Other Sources
    Details
    Publication Date: 2019-06-27
    Description: Outline of specific solutions in the areas of attitude control, interplanetary trajectory parameters, and orbital configurations of major planetary spacecraft. It is shown that inertia wheel supplementation to a three-axis, stabilized attitude control system will substantially reduce propellant weight and attitude jet firings, especially when considering three-year orbital lifetimes as well as interplanetary trip times of several years. Eight interplanetary trajectory parameters including the earth injection energy and the declination of the launch asymptote are shown for a 1980 earth launch mission to Jupiter. The effects of the interplanetary trajectory parameters on the deboost velocities and resulting orbits about Jupiter are summarized. Orbital mode and science interfaces are defined, and a celestial mechanics experiment independent of earth tracking is briefly outlined.
    Keywords: SPACE VEHICLES
    Type: Journal of the Astronautical Sciences; 20; Sept
    Format: text
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  • 9
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    Discrete approximations to optimal trajectories using direct transcription and nonlinear programming (1992)
    In:  Other Sources
    Details
    Publication Date: 2019-07-12
    Keywords: ASTRODYNAMICS
    Type: Journal of Guidance, Control, and Dynamics (ISSN 0731-5090); 15; 4 Ju; 994-1002
    Format: text
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  • 10
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    Mishaps with Oxygen in NASA Operations (1971)
    In:  CASI
    Details
    Publication Date: 2019-08-14
    Description: Data from a substantial number of oxygen mishaps obtained from NASA and contractor records are presented. Information from several Air Force records, concerning oxygen accidents involving aircraft operations, are also included. Descriptions of the mishaps and their causes, for both liquid and gaseous oxygen in ground test facilities and space vehicle systems, are given. A number of safety regulations aimed at reducing the accident probability is discussed. The problems related to material compatibility and materials testing are considered, and the limited information on factors affecting the ignition of materials in oxygen is presented. In addition, details are given of several of the accident/incidents listed in order to define the combination of conditions causing the mishap. In addition to propellant system mishaps, accident/incidents which occurred in space and ground system structures were included, as well as those in electrical systems, ground support facilities, ordnance, and related operations.
    Keywords: BIOTECHNOLOGY
    Type: NASA-TM-X-67953 , E-6604 , Oxygen Compressors and Pumps Symp.; Nov 09, 1971 - Nov 11, 1971; Atlanta
    Format: application/pdf
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