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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 253 records · Page 14

Applications Study of Aero-Maneuvering Orbit-to-Orbit Shuttle (AMOOS), Executive Summary

Preliminary designs and the supporting analysis for both the Aeromaneuvering Orbit-to-Orbit Shuttle (AMOOS) and the Aeromaneuvering Recovery System (AMRS) are presented. The AMOOS design is shown to yield from twice to almost three times the high energy, round-trip payloads as a purely propulsive vehicle of the same weight. Typically AMOOS can perform a crew rotation mission to equatorial geosynchronous orbit in one space shuttle launch. The flight test program analysis modeled parameters such as maximum dynamic pressure, heating rates, guidance, stability and recovery. Two model flight schedules were developed, one consisting of four flights and the other of two flights. The former is considered a very low risk, high information return program whereas the latter is a minimal cost program consistent with reasonable data returns and chance of success. The AMOOS and AMRS guidance scheme developed using linear regulator theory proved a precise and accurate guidance scheme. Both it and a classical linear system's based scheme were evaluated using 65 simulated trajectories in which the position in the entry corridor and the atmospheric density were varied randomly.

White, J.↗

Four-D global reference atmosphere

Model generates values for pressure, density, temperature, and winds from surface level to orbital altitudes. Program can define altitude profiles of atmospheric parameters for simulated trajectory.

Robertson, B.↗

Three-dimensional random earth atmospheres for Monte Carlo trajectory analyses

A set of four computer tapes containing random three dimensional Earth atmospheres is available for Monte Carlo trajectory analyses. The tapes contain sufficient atmospheric tables to allow replications of any trajectory below an altitude of 99 km. The atmospheres were provided by an empirical model designed to generate random atmospheres whose distributions match those in a data base of sounding rocket measurements. A readily implementable means of linking the tapes to any existing trajectory simulation computer program is described involving the addition of three subroutines which are listed in an appendix.

Campbell, J. W.↗

A preliminary study of the attitude control for the Shuttle Tethered Satellite System

The objective of this investigation is to determine the equations of motion governing the attitude of a tethered satellite and subsequently to gain insight toward obtaining an appropriate control law. This study relates the coupling of the rotational dynamics of the satellite with the dynamical system of the Orbiter already constructed. In particular, a simplified approach is utilized to describe the satellite as constrained to planar motion. Modifications to the existing tethered satellite trajectory simulation provide a conceptual study of the satellite's behavior and its effect on the overall system.

Rupp, C. C.↗

An Economical Semi-Analytical Orbit Theory for Retarded Satellite Motion About an Oblate Planet

Brouwer and Brouwer-Lyddanes' use of the Von Zeipel-Delaunay method is employed to develop an efficient analytical orbit theory suitable for microcomputers. A succinctly simple pseudo-phenomenologically conceptualized algorithm is introduced which accurately and economically synthesizes modeling of drag effects. The method epitomizes and manifests effortless efficient computer mechanization. Simulated trajectory data is employed to illustrate the theory's ability to accurately accommodate oblateness and drag effects for microcomputer ground based or onboard predicted orbital representation. Real tracking data is used to demonstrate that the theory's orbit determination and orbit prediction capabilities are favorably adaptable to and are comparable with results obtained utilizing complex definitive Cowell method solutions on satellites experiencing significant drag effects.

Gordon, R. A.↗

Elliptical Orbit Performance Computer Program

Elliptical Orbit Performance (ELOPE) computer program for analyzing orbital performance of space boosters uses orbit insertion data obtained from trajectory simulation to generate parametric data on apogee and perigee altitudes as function of payload data. Data used to generate presentation plots that display elliptical orbit performance capability of space booster.

Myler, T.↗

An economical semi-analytical orbit theory for micro-computer applications

An economical algorithm is presented for predicting the position of a satellite perturbed by drag and zonal harmonics J2 through J4. Simplicity being of the essence, drag is modeled as a secular decay rate in the semimajor axis (retarded motion) with the zonal perturbations modeled from a modified version of Brouwers formulas. The algorithm is developed as an alternative on-board orbit predictor; a back up propagator requiring low energy consumption; or a ground based propagator for microcomputer applications (e.g., at the foot of an antenna). An O(J2) secular retarded state partial matrix (matrizant) is also given to employ with state estimation. The theory has been implemented in BASIC on an inexpensive microcomputer, the program occupying under 8K bytes of memory. Simulated trajectory data and real tracking data are employed to illustrate the theory's ability to accurately accommodate oblateness and drag effects.

Gordon, R. A.↗

Estimating Geophysical Parameters From Gravity Data

ORBSIM program developed for accurate extraction of parameters of geophysical models from Doppler-radio-tracking data acquired from orbiting planetary spacecraft. Model of proposed planetary structure used in numerical integration along simulated trajectories of spacecraft around primary body. Written in FORTRAN 77.

Sjogren, William L.↗

Global Reference Atmosphere Model (GRAM)

GRAM series of four-dimensional atmospheric model validated by years of data. GRAM program, still available. More current are Gram 86, which includes atmospheric data from 1986 and runs on DEC VAX, and GRAM 88, which runs on IBM 3084. Program generates altitude profiles of atmospheric parameters along any simulated trajectory through atmosphere, and also useful for global circulation and diffusion studies.

Woodrum, A. W.↗

An economical semi-analytical orbit theory for micro-computer applications

An economical algorithm is presented for predicting the position of a satellite perturbed by drag and zonal harmonics J sub 2 through J sub 4. Simplicity being of the essence, drag is modeled as a secular decay rate in the semi-axis (retarded motion); with the zonal perturbations modeled from a modified version of the Brouwers formulas. The algorithm is developed as: an alternative on-board orbit predictor; a back up propagator requiring low energy consumption; or a ground based propagator for microcomputer applications (e.g., at the foot of an antenna). An O(J sub 2) secular retarded state partial matrix (matrizant) is also given to employ with state estimation. The theory was implemented in BASIC on an inexpensive microcomputer, the program occupying under 8K bytes of memory. Simulated trajectory data and real tracking data are employed to illustrate the theory's ability to accurately accommodate oblateness and drag effects.

Gordon, R. A.↗

Optimization of interplanetary trajectories with unpowered planetary swingbys

A method is presented for calculating and optimizing unpowered planetary swingby trajectories using a patched conic trajectory generator. Examples of unpowered swingby trajectories are given to demonstrate the method. The method, which uses primer vector theory, is not highly accurate, but provides projections for preliminary mission definition studies. Advantages to using a patched conic trajectory simulation for preliminary studies which examine many different and complex missions include calculation speed and adaptability to changes or additions to the formulation.

Sauer, Carl G., Jr.↗

Polar wind ion bands after neutral sheet acceleration

The transport of polar wind protons from their ionospheric source through the magnetosphere is examined, using three-dimensional particle codes. The trajectory simulations demonstrate the escape of the high-latitude polar wind in the boundary layers during the quiescent magnetosphere, and, in contrast, its trapping in the nightside plasma sheet at times of high Kp. It is shown that the equatorial curvature of the magnetic field lines plays the role of an acceleration filter which yields, during active conditions, an 'ion band'-like precipitation of the polar wind protons characterized by a decrease of the downflowing ion energy with latitude, from several hundred down to a few electron volts. A further comparison between data and computations tends to indicate that, during disturbed times, the dayside originating polar wind provides an important contribution to the hundreds of electron volt downflowing protons in the nightside sector.

Delcourt, D. C.↗

Aerobrakes For A Manned Mars Mission

Paper presents results of study of aerobraking in manned mission to Mars. Describes geometry and aerodynamic characteristics of aerobraked vehicle. Discusses computer program, WTRAJ, used to simulate trajectories near planets. Analyzes aerocapture processes for both Mars and Earth. Examines mass efficiency, or saving in propellant mass, afforded by aerobraking.

Menees, G. P.↗

Advanced Software Development Workstation Project

The Advanced Software Development Workstation Project, funded by Johnson Space Center, is investigating knowledge-based techniques for software reuse in NASA software development projects. Two prototypes have been demonstrated and a third is now in development. The approach is to build a foundation that provides passive reuse support, add a layer that uses domain-independent programming knowledge, add a layer that supports the acquisition of domain-specific programming knowledge to provide active support, and enhance maintainability and modifiability through an object-oriented approach. The development of new application software would use specification-by-reformulation, based on a cognitive theory of retrieval from very long-term memory in humans, and using an Ada code library and an object base. Current tasks include enhancements to the knowledge representation of Ada packages and abstract data types, extensions to support Ada package instantiation knowledge acquisition, integration with Ada compilers and relational databases, enhancements to the graphical user interface, and demonstration of the system with a NASA contractor-developed trajectory simulation package. Future work will focus on investigating issues involving scale-up and integration.

Lee, Daniel↗

Global Reference Atmosphere Model-1988

Four-D Global Reference Atmosphere computer program (GRAM) developed from empirical mathematical model of atmosphere generating values for pressure, density, temperature, and winds from surface level to orbital altitudes. Generates altitude profiles of parameters of atmosphere along any simulated trajectory through atmosphere. Developed from design applications in Space Shuttle program. Other potential applications include studies of global circulation and diffusion and generation of profiles for comparison with results of other atmospheric-measurement techniques such as satellite-measured temperature profiles and wind profiles from infrasonic measurements. Written in STANDARD FORTRAN 77.

Johnson, D. L.↗

Algorithmically Specialized Parallel Architecture For Robotics

Computing system called Robot Mathematics Processor (RMP) contains large number of processor elements (PE's) connected in various parallel and serial combinations reconfigurable via software. Special-purpose architecture designed for solving diverse computational problems in robot control, simulation, trajectory generation, workspace analysis, and like. System an MIMD-SIMD parallel architecture capable of exploiting parallelism in different forms and at several computational levels. Major advantage lies in design of cells, which provides flexibility and reconfigurability superior to previous SIMD processors.

Fijany, Amir↗