Engineering topics

Gregory, G. L.

Publications and source records attributed to Gregory, G. L..

At least 91 records · Page 5

NASA NTRS1980

Summary of aircraft results for 1978 southeastern Virginia urban plume measurement study of ozone, nitrogen oxides, and methane

Ozone production was determined from aircraft and surface in situ measurements, as well as from an airborne laser absorption spectrometer. Three aircraft and approximately 10 surface stations provided air-quality data. Extensive meteorological, mixing-layer-height, and ozone-precursor data were also measured. Approximately 50 hrs (9 flight days) of data from the aircraft equipped to monitor ozone, nitrogen oxides, dewpoint temperature, and temperature are presented. In addition, each experiment conducted is discussed.

Gregory, G. L.↗

NASA NTRS1980

Laboratory investigations of cloud nuclei from combustion of Space Shuttle propellant

Small quantities of solid rocket motor propellant, of the type to launch the Space Shuttle, were burned at ambient pressure in the laboratory to provide aerosol samples for characterization. A portion of each sample was injected into an isothermal cloud chamber and the remainder into a 770-liter holding tank. Portable ice nucleus (IN) counters, filter devices for IN determinations and a cloud condensation nucleus (CCN) counter sampled from the tank. The measurements show that particles resulting from the combustion of the propellant are active IN (3.3 times 10 to the 8th to 1.5 times 10 to the 11th/g active at 20 C). The portable counters and filters detected significantly fewer IN than the isothermal cloud chamber. The propellant aerosol is a prolific source of CCN that swamped the instrument.

Hindman Ii, E. E.↗

NASA NTRS1980

Southeastern Virginia Urban Plume Study design considerations and measurement results

The Southeastern Virginia Urban Plume Study is intended to provide a testing ground for NASA remote sensors designed for urban and regional scale monitoring of air quality phenomena. The air quality experiments it has conducted have incorporated surface, airborne, sonde and balloon platforms which measured air quality and meteorology parameters, with emphasis on photochemically produced O3 and its primary precursors upwind, above, and downwind of the Hampton Roads area urban complex. The results from three years of experiments have shown that such different meteorological conditions as blue/broken skies, high/moderate temperatures and low/high winds have a direct impact on the degree of downwind aging of the summer urban O3 airmass. In 1979, the urban plume was traced at aging times of 0.5, 1.5, and 5 hr.

Mcdougal, D. S.↗

NASA NTRS1979

Summary of southeastern Virginia urban plume measurement data for August 4 and 5, 1977

The measurement program was conducted to define the characteristics of the Southeastern Virginia urban plume with emphasis on the photooxidant species. The measurement area was a rectangle approximately 200 km by 60 km centered in the Hampton Roads area of Tidewater Virginia. This area includes the cities of Norfolk, Virginia Beach, Chesapeake, Newport News, and Hampton. The data set presented includes aircraft measurements for ozone, nitrogen oxides, carbon monoxide, methane, and meteorological parameters such as dewpoint temperature. Surface level data for ozone are presented for 10 stations located throughout the test area. Comprehensive meteorological data from existing National Weather Service stations and special locations selected for the urban plume program are summarized.

Gregory, G. L.↗

NASA NTRS1979

Launch vehicle effluent measurements during the September 5, 1977, Titan 3 launch at Air Force eastern test range

Airborne effluent measurements and cloud physical behavior data are presented. The monitoring program included airborne effluent measurements in situ in the launch cloud, visible and infrared photography of cloud growth and physical behavior, and limited surface collection of rain samples. Effluent measurements included concentrations of HCl, Cl2, NO, nitric oxide, and particles as a function of time in the exhaust cloud. In situ particle mass concentration and number density were measured as a function of time and size in the range of 0.05 micron m to 30 micron m diameter. Measurement results were similar to those of previous launch monitorings. Maximum HCl and nitric oxide concentrations of Cl2 were maximum about 2 minutes after launch and by 10 to 15 minutes had decayed to less than 10 ppb (detection limit). Particle measurements showed most of the particles present to be below about 3-micron m diameter. Postlaunch analyses of collected particle samples showed significant amounts of Al (some cases Cl) from about 3-micron m to 0.04-micron m diameter.

Wornom, D. E.↗

NASA NTRS1979

Launch vehicle effluent measurements during the May 12, 1977, Titan 3 launch at Air Force Eastern Test Range

Airborne effluent measurements and cloud physical behavior for the May 21, 1977, Titan 3 launch from the Air Force Eastern Test Range, Fla. are presented. The monitoring program included airborne effluent measurements in situ in the launch cloud, visible and infrared photography of cloud growth and physical behavior, and limited surface collection of rain samples. Airborne effluent measurements included concentrations of HCl, NO, NOx, and aerosols as a function of time in the exhaust cloud. For the first time in situ particulate mass concentration and aerosol number density were measured as a function of time and size in the size range of 0.05 to 25 micro meters diameter. Measurement results were similar to those of earlier launch monitorings. Maximum HCl and NOx concentrations ranged from 10 ppm and 500 ppb, respectively, several minutes after launch to about 1 ppm and 100 ppb at 45 minutes after launch.

Gregory, G. L.↗

NASA NTRS1978

Detection of hydrogen chloride gas in air

Launch vehicle effluent (LVE) monitoring is part of NASA's overall tropospheric and stratospheric environmental program. Following nine techniques are evaluated and developed in report: bubbler method, pH measurements, indicator tubes, microcoulometers, modified condensation nuclei counter, dual-isotope absorption, gas-filter correlation, chemiluminescent nitric oxide detection, chemiluminescent luminol-oxidation detection.

Gregory, G. L.↗

NASA NTRS1978

Summary of airborne chlorine and hydrogen chloride gas measurements for August 20 and September 5, 1977 Voyager launches at Air Force Eastern Test Range, Florida

Airborne chlorine and hydrogen chloride measurements were made in the tropospheric ground cloud following the Voyager launches of August 20 and September 5, 1977. The maximum observed hydrogen chloride concentration for both launches was about 25 to 30 parts per million (ppm) occurring typically 2 to 6 minutes after launch. By completion of the sampling mission (1-1/2 hours for August, 4-1/2 hours for September), the maximum in-cloud concentration decayed to about 1 to 2 ppm. Maximum observed chlorine concentrations were about 40 to 55 parts per billion (ppb) about 2 to 8 minutes after launch; by about 15 minutes after launch, chlorine concentrations were less than 10 ppb (detection limit). In-cloud chlorine concentrations were well below 1 percent of hydrogen chloride concentrations. The appendix of the report discusses the chlorine instrument and the laboratory evaluation of the detector.

Gregory, G. L.↗

NASA NTRS1977

Experimental measurements of the ground cloud effluents and cloud growth for the May 20, 1975, Titan 3C launch at Air Force Eastern Test Range, Florida

The experiment included surface level and airborne in situ cloud measurements of the exhaust effluents from the Titan IIIC solid rocket boosters. Simultaneous visible spectrum photographic pictures of the ground cloud as well as infrared imaging of the cloud were obtained to study the cloud rise, growth, and direction of travel within the earth's surface mixing layer. The NASA multilayer diffusion model predictions of cloud growth, direction of travel, and expected surface level effluent concentrations were made prior to launch and after launch using measured meteorological conditions. Prelaunch predictions were used to position the effluent monitoring instruments, and the postlaunch predictions were compared with the measured data. Measurement results showed that surface level effluent values were low, often below the detection limits of the instrumentation. The maximum surface level hydrogen chloride concentration measured 50 parts per billion at about 8 km from the launch pad. The maximum observed in-cloud (airborne measurement) hydrogen chloride concentration was 7 per million.

Gregory, G. L.↗

NASA NTRS1977

Evaluation of a hydrogen chloride detector for environmental monitoring

The paper describes a hydrogen chloride detector designed to monitor concentrations of hydrogen chloride gas in the ambient environment. The detector was developed for NASA for use in launch vehicle effluent monitoring. The detector operates on chemiluminescence principles with a lower detection limit of less than 5 x 10 to the -3rd ppm (by volume). The hydrogen chloride in the air sample reacts with a bromide-bromate coating in the inlet tube of the instrument producing bromine. Bromine is then quantitated by chemiluminescent oxidation of luminol. The visible light generated in the chemiluminescent reaction is proportional to the hydrogen chloride concentration of the sampled airstream. The detector is most suited to laboratory or field studies where hydrogen chloride is the dominant pollutant, as compared to the interfering species. Interferences include strong acids, acid-forming gases, and halogen gases. Of the interferences investigated the most serious in these groups are hydrochloric and sulfuric acid, sulfur dioxide, and chlorine, respectively. The detector has been in use since 1974 and has been found to be highly portable, rugged, and stable under extreme environmental conditions.

Gregory, G. L.↗

NASA NTRS1976

Measurement techniques investigated for detection of hydrogen chloride gas in ambient air

Nine basic techniques are discussed, ranging from concentration (parts per million) to dosage only (parts per million-seconds) measurement techniques. Data for each technique include lower detection limit, response time, instrument status, and in some cases, specificity. Several techniques discussed can detect ambient hydrogen chloride concentrations below 1 part per million with a response time of seconds.

Gregory, G. L.↗

NASA NTRS1976

Experimental measurements of the ground cloud growth during the 11 February 1974, Titan-Centaur launch at Kennedy Space Center

The Titan-Centaur was launched from Kennedy Space Center on February 11, 1974 at 0948 eastern daylight time. Ground level effluent measurements were obtained from the solid rocket motors for comparison with NASA diffusion models for predicting effluent ground level concentrations and cloud behavior. The results obtained provide a basis for an evaluation of such key model inputs such as cloud rise rate, stabilization altitude, crosswind growth, volume expansion, and cloud trajectory. Ground level effluent measurements were limited because of changing meteorological conditions, incorrect instrument location, and operational problems. Based on the measurement results, operational changes are defined. Photographs of the ground exhaust clouds are shown. The chemical composition of the exhaust gases was analyzed and is given.

Stewart, R. B.↗

NASA NTRS1975

Effluent sampling of Titan 3 C vehicle exhaust

Downwind in situ ground-level measurements of the exhaust from a Titan 3 C launch vehicle were made during a normal launch. The measurement activity was conducted as part of an overall program to obtain field data for comparison with the multilayer dispersion model currently being used to predict the behavior of rocket vehicle exhaust clouds. All measurements were confined to land, ranging from the launch pad to approximately 2 kilometers downwind from the pad. Measurement systems included detectors for hydrogen chloride (HCl), carbon dioxide (CO2), and particulates (Al2O3). Airborne and ground-based optical systems were employed to monitor exhaust cloud rise, growth, and movement. These measurement systems, located along the ground track (45 deg azimuth from the launch pad) of the exhaust cloud, showed no effluents attributable to the launch. Some hydrogen chloride and aluminum oxide were detected in the surface wind direction (15 deg azimuth) from the pad. Comparisons with the model were made in three areas: (1) assumption of cloud geometry at stabilization; (2) prediction of cloud stabilization altitude; and (3) prediction of the path of cloud travel. In addition, the importance of elemental analyses of the particulate samples is illustrated.

Gregory, G. L.↗

NASA NTRS1974

Effluent sampling of Scout D and Delta launch vehicle exhausts

Characterization of engine-exhaust effluents (hydrogen chloride, aluminum oxide, carbon dioxide, and carbon monoxide) has been attempted by conducting field experiments monitoring the exhaust cloud from a Scout-Algol III vehicle launch and a Delta-Thor vehicle launch. The exhaust cloud particulate size number distribution (total number of particles as a function of particle diameter), mass loading, morphology, and elemental composition have been determined within limitations. The gaseous species in the exhaust cloud have been identified. In addition to the ground-based measurements, instrumented aircraft flights through the low-altitude, stabilized-exhaust cloud provided measurements which identified CO and HCI gases and Al2O3 particles. Measurements of the initial exhaust cloud during formation and downwind at several distances have established sampling techniques which will be used for experimental verification of model predictions of effluent dispersion and fallout from exhaust clouds.

Hulten, W. C.↗

NASA NTRS1974

Three stage gas dilution system for calibration of air quality instrumentation

Tests were conducted on a three stage gas dilution system to evaluate the performance of the system for preparation of gas mixtures in the range of concentrations from 1 to 200 ppm. The test gas used in the evaluation was carbon monoxide. Mixtures of carbon monoxide and air were prepared in the gas dilution system and analyzed on stream with a commercially available infrared CO detector. Results showed the gas dilution system to be accurate to within 5, 3, and 2 percent in the respective ranges of 1-20 ppm, 20-50 ppm, and 50-200 ppm.

Gregory, G. L.↗

NASA NTRS1974

Apollo Saturn 511 effluent measurements from the Apollo 16 launch operations: An experiment

An experiment was performed in conjunction with the Apollo 16 launch to define operational and instrumentational problems associated with launch-vehicle exhaust effluent monitoring. Ground and airborne sampling were performed for CO, CO2, hydrocarbons, and particulates. Sampling systems included filter pads and photometers for particulates and whole-air grab samples for gases. Launch debris was identified in the particulate samples at ground level(taken immediately after launch) and in the airborne measurements (taken 40 to 50 minutes after launch approximately 40 km downwind of the pad). Operational problems were identified and included the need for higher instrumentation mobility and the need for real-time sampling instrumentation as opposed to collection-type samples such as the whole-air grab sample.

Gregory, G. L.↗

NASA NTRS1972

Experimental Investigation of the Mechanical Behavior of a Filled Elastomer at Pressures Below 10 to the -6th Power Torr

The mechanical behavior of a filled elastomer was studied with emphasis on understanding the vacuum-material interactions occurring, and to develop analytical techniques for predicting the vacuum behavior. The test results indicate that two separate mechanisms are involved in the observed property changes: the first controls the time response to applied stress; the second determines the initial internal state of the materials as the result of stresses. It is concluded that the mechanical property changes are attributable to changes in the relaxation processes occurring in the material. These changes are brought about by outgassing of water. Recommendations for future investigations are included.

Gregory, G. L.↗

NASA NTRS1972

Prediction of the mechanical properties of a filled elastomer in vacuum

Constant force creep measurements were made at three stress levels on samples of an ammonium perchlorate filled butadiene-acrylic acid copolymer in vacuum and in the atmosphere (air, 50% relative humidity) at a temperature of 28 C. The creep compliance of the samples decreased as much as 50% after 14 days of vacuum exposure. Shift factors were developed which, when applied to the atmospheric compliance measurements, predicted the behavior in vacuum. The experimental results led to the following conclusions: (1) shift factors can be applied to predict compliance behavior in vacuum from measurements in air, and (2) the shift factors are independent of stress but increase in magnitude with increasing vacuum exposure.

Gregory, G. L.↗