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Jones, J.

Publications and source records attributed to Jones, J..

62 records · Page 4
All sourcesNASA NTRSDOE OSTI
NASA NTRS1995

Cross-tail magnetic flux ropes as observed by the GEOTAIL spacecraft

Ten transient magnetic structures in Earth's magnetotail, as observed in GEOTAIL measurements, selected for early 1993 (at (-) X(sub GSM) = 90 - 130 Earth radii), are shown to have helical magnetic field configurations similar to those of interplanetary magnetic clouds at 1 AU but smaller in size by a factor of approximately = 700. Such structures are shown to be well approximated by a comprehensive magnetic force-free flux-rope model. For this limited set of 10 events the rope axes are seen to be typically aligned with the Y(sub GSM) axis and the average diameter of these structures is approximately = 15 Earth radii.

Lepping, R. P.↗
NASA NTRS1994

Overview of the space environmental effects observed on the retrieved Long Duration Exposure Facility (LDEF)

The Long Duration Exposure Facility (LDEF), which encompassed 57 experiments with more than 10,000 test specimens, spent 69 months in Low Earth Orbit (LEO) before it was retrieved by the Space Shuttle in January 1990. Hundreds of LDEF investigators, after studying for over two years these retrieved test specimens and the onboard recorded data and systems hardware, have generated a unique first-hand view of the long-term synergistic effects that the LEO environment can have on spacecraft. These studies have also contributed significantly toward more accurate models of the LEO radiation, meteoroid, manmade debris and atomic oxygen environments. This paper provides an overview of some of the many LDEF observations and the implications these can have on future spacecraft such as Space Station Freedom.

Kinard, W.↗
NASA NTRS1988

Flow-induced vibrations of the SSME LOX inlet tee vanes

This paper describes the results of a program initiated to identify the cause and the mechanism of 4-kHz vibrations of the Space Shuttle main engine's (SSME's) LOX inlet tee, which were revealed in 17 percent of the SSMEs during ground tests. The results of the engines' inspection, structural analyses, computational fluid dynamics studies, literature reviews, expert consultations, and laboratory testings identified the probable cause of the 4-kHz vibrations being related to the fact that the walls of some tees were thinner than in the mojority of tees, resulting in less stiff structures. The mechanism of the vibrations was identified as vortex shedding in combination with a structural coupling with the thrust cone, which increased the vane mobility, which, in turn, aggravated the fluid coupling with the thrust cone. As a result, the vane mobility was increased, aggravating the fluid coupling with the vanes. An internal modification was developed and was successfully demonstrated on an engine that had previously exhibited a 4-kHz problem.

O'Connor, G. M.↗
NASA NTRS1987

Embedded expert system for space shuttle main engine maintenance

The SPARTA Embedded Expert System (SEES) is an intelligent health monitoring system that directs analysis by placing confidence factors on possible engine status and then recommends a course of action to an engineer or engine controller. The technique can prevent catastropic failures or costly rocket engine down time because of false alarms. Further, the SEES has potential as an on-board flight monitor for reusable rocket engine systems. The SEES methodology synergistically integrates vibration analysis, pattern recognition and communications theory techniques with an artificial intelligence technique - the Embedded Expert System (EES).

Pooley, J.↗
NASA NTRS1987

Using automatic robot programming for space telerobotics

The interpreter of a task level robot programming system called Handey is described. Handey is a system that can recognize, manipulate and assemble polyhedral parts when given only a specification of the goal. To perform an assembly, Handey makes use of a recognition module, a gross motion planner, a grasp planner, a local approach planner and is capable of planning part re-orientation. The possibility of including these modules in a telerobotics work-station is discussed.

Mazer, E.↗
NASA NTRS1985

Automated Extraction of Absorption Bands from Reflectance Special

A multiple high order derivative spectroscopy technique has been developed for deriving wavelength positions, half widths, and heights of absorption bands in reflectance spectra. The technique is applicable to laboratory spectra as well as medium resolution (100-200/cm) telescope or spacecraft spectra with moderate (few percent) noise. The technique permits absorption band positions to be detected with an accuracy of better than 3%, and often better than 1%. The high complexity of radiative transfer processes in diffusely reflected spectra can complicate the determination of absorption band positions. Continuum reflections, random illumination geometries within the material, phase angle effects, composite overlapping bands, and calibration uncertainties can shift apparent band positions by 20% from their actual positions or mask them beyond detection. Using multiple high order derivative analysis, effects of scattering continua, phase angle, and calibration (smooth features) are suppressed. Inflection points that characterize the positions and half widths of constituent bands are enhanced by the process and directly detected with relatively high sensitivity.

Huguenin, R. L.↗
NASA NTRS1984

An integrated dynamical and geochemical approach to lunar origin modelling

The three major categories of models of lunar origin which explain the Moon's properties are complete and a more general scenario is presented. The model presented is as the Earth grew by planetesimal bombardment, a circumterrestrial cloud of particles was created from a combination of impact ejected mantle material and planetismals captured directly into orbit around the Earth. The compositional properties are explained two ways: (1) a few big late planetismals of diverse composition are captured in orbit and/or hit the Earth; and (2) the circumterrestrial swarm acts as a filter, preferentially capturing small weak silicate bodies, while passing large iron planetismals.

Greenberg, R.↗