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Disimile, P. J.

Publications and source records attributed to Disimile, P. J..

13 records
All sourcesNASA NTRSDOE OSTI
NASA NTRS1991

Oxygen detection using the laser diode absorption technique

Accurate measurement of the concentration and flow rate of gaseous oxygen is becoming of greater importance. The detection technique presented is based on the principal of light absorption by the Oxygen A-Band. Oxygen molecules have characteristics which attenuate radiation in the 759-770 nm wavelength range. With an ability to measure changes in the relative light transmission to less than 0.01 percent, a sensitive optical gas detection system was configured. This system is smaller in size and light in weight, has low energy requirements and has a rapid response time. In this research program, the application of temperature tuning laser diodes and their ability to be wavelength shifted to a selected absorption spectral peak has allowed concentrations as low as 1300 ppm to be detected.

Disimile, P. J.↗
NASA NTRS1991

Rocket engine plume diagnostics using video digitization and image processing - Analysis of start-up

Video digitization techniques have been developed to analyze the exhaust plume of the Space Shuttle Main Engine. Temporal averaging and a frame-by-frame analysis provide data used to evaluate the capabilities of image processing techniques for use as measurement tools. Capabilities include the determination of the necessary time requirement for the Mach disk to obtain a fully-developed state. Other results show the Mach disk tracks the nozzle for short time intervals, and that dominate frequencies exist for the nozzle and Mach disk movement.

Disimile, P. J.↗
NASA NTRS1991

Optical leak detection of oxygen using IR-laser diodes

The ability to accurately measure the concentration of gaseous oxygen and its corresponding flow rate is becoming of greater importance. The technique being presented is based on the principal of light attenuation due to the absorption of radiation by the A-band of oxygen which is located in the 759-770 nm wavelength range. With an ability to measure the change in the light transmission to 0.05 percent, a sensitive optical leak detection system which has a rapid time response is possible. In this research program, the application of laser diode technology and its ability to be temperature tuned to a selected oxygen absorption spectral peak has allowed oxygen concentrations as low as 16,000 ppm to be detected.

Disimile, P. J.↗
NASA NTRS1990

Space vehicle propulsion systems: Environmental space hazards

The hazards that exist in geolunar space which may degrade, disrupt, or terminate the performance of space-based LOX/LH2 rocket engines are evaluated. Accordingly, a summary of the open literature pertaining to the geolunar space hazards is provided. Approximately 350 citations and about 200 documents and abstracts were reviewed; the documents selected give current and quantitative detail. The methodology was to categorize the various space hazards in relation to their importance in specified regions of geolunar space. Additionally, the effect of the various space hazards in relation to spacecraft and their systems were investigated. It was found that further investigation of the literature would be required to assess the effects of these hazards on propulsion systems per se; in particular, possible degrading effects on exterior nozzle structure, directional gimbals, and internal combustion chamber integrity and geometry.

Disimile, P. J.↗
NASA NTRS1990

A high severity space hazard - Orbital debris

This paper examines the orbital debris-meteoroid hazard that will be encountered by the Space Station Freedom. Recent reports on the orbital debris studies are discussed with special attention given to the procedures and techniques that can be used to minimize the impact damage, to avoid the collision, and to design shielding distribution so as to reduce the penetration damage.

Bahr, G. K.↗
NASA NTRS1990

Space vehicle propulsion systems - Environmental space hazards

An evaluation of hazards which exist in geo-lunar space and have the potential to negatively affect a long-term mission-oriented spacecraft systems is presented based on published data. The hazards are categorized as pervasive (radiation), incident specific (meteoroids and thermal shock), and chemically corrosive (monatomic oxygen). It appears that the number one priority should be the development of new materials; and the secondary concern should be the development of fabrication techniques for the exterior hull, so that incident specific hazards can be minimized in an active fashion. The pervasive hazard can be dealt with by exploring on-board circuit technology with ancillary monitoring systems. Effects of thermal shock on the exterior nozzle, directional gimbals, and internal combustion chamber geometry seem to need more investigation.

Bahr, G. K.↗
NASA NTRS1986

Transverse vorticity measurements using an array of four hot-wire probes

A comprehensive description of the technique used to obtain a time series of the quasi-instantaneous transverse vorticity from a four wire array of probes is presented. The algorithmic structure which supports the technique is described in detail and demonstration data, from a large plane shear layer, are presented to provide a specific utilization of the technique. Sensitivity calculations are provided which allow one contribution to the inherent uncertainty of the technique to be evaluated.

Foss, J. F.↗
NASA NTRS1986

Quasi-instantaneous transverse vorticity measurements in an excited, two-dimensional, single stream mixing layer

Quasi-instantaneous transverse vorticity time series were obtained with a four-wire array at each of the 414 points in the measurement grid. These vorticity measurements indicate absolute values of peak vorticity which are an order of magnitude greater than those indicated by phase averaged transverse vorticity measurements. These large quasi-instantaneous transverse vorticity fluctuations indicate strong mixing throughout the core and periphery of the newly formed and saturated vortical structures. Although the magnitude is approximately the same throughout these structures, the frequency of occurrence of these large fluctuations appears to be less on the low speed side of the newly formed vortex.

Disimile, P. J.↗
NASA NTRS1986

The MSU free shear flow facility

A free shear layer wind tunnel has been constructed in order to undertake detailed, high quality transverse vorticity measurements in an isothermal, single stream mixing layer. The large 50 x 80 cm primary flow and 3-m test section length allows the generation of large, isolated vortical motions in high Reynolds number flow. A uniformly developed, irrotational secondary flow is achieved by means of an entrainment module.

Disimile, P. J.↗
NASA NTRS1985

Phase averaged transverse vorticity measurements in an excited, two-dimensional mixing layer

Experiments were run to characterize the global vorticity distribution in an excited plane mixing layer. A reciprocating piston excited the mixing layer at a 0.0053 intensity, a Strouhal number of 0.97, and a 15 Hz frequency. An X-wire anemometer and a pitot tube furnished data in the 13 m/sec free stream velocity flow. Deep depressions were observed in the velocity contours on the high-speed side of the mixing layer, while primary vortex growth occurred on the low-speed side. The cores of the vortices moved at highly differentiated velocities. Phase plots were also generated to show tearing and fusing of the vortex contours.

Disimile, P. J.↗
NASA NTRS1985

Entrainment region phenomena for a large plane shear layer

The subatmospheric test section of the present free shear layer facility allows the entrainment air to be introduced with a negligible disturbance level. The very low frequency oscillations, which are prominently observed in the entrainment stream and which are present throughout the shear layer, are attributed to an inherent instability in the transition from a boundary layer to a free shear layer state. The basic features of the disturbance field are documented herein.

Ali, S. K.↗