Engineering Papers⌕ Search

Engineering topics

Nealy, J. E.

Publications and source records attributed to Nealy, J. E..

At least 37 records · Page 2
All sourcesNASA NTRSDOE OSTI
NASA NTRS1991

Concepts for manned lunar habitats

The design philosophy that will guide the design of early lunar habitats will be based on a compromise between the desired capabilities of the base and the economics of its development and implantation. Preferred design will be simple, make use of existing technologies, require the least amount of lunar surface preparation, and minimize crew activity. Three concepts for an initial habitat supporting a crew of four for 28 to 30 days are proposed. Two of these are based on using Space Station Freedom structural elements modified for use in a lunar-gravity environment. A third concept is proposed that is based on an earlier technology based on expandable modules. The expandable modules offer significant advantages in launch mass and packaged volume reductions. It appears feasible to design a transport spacecraft lander that, once landed, can serve as a habitat and a stand-off for supporting a regolith environmental shield. A permanent lunar base habitat supporting a crew of twelve for an indefinite period can be evolved by using multiple initial habitats. There appears to be no compelling need for an entirely different structure of larger volume and increased complexity of implantation.

Hypes, W. D.↗
NASA NTRS1991

Martian regolith as space radiation shielding

Mars exploration crews will be exposed to such high radiation dosages in route from earth that as to sharply reduce the allowable dose they should receive while on the Martian surface. An account is presently given of the possibility of using Martian regolith as crew shielding to maintain very low short-term dose limits. NASA-Langley's nucleon and heavy-ion transport computer codes are used to predict the propagation and interaction of the free-space nucleons and heavy ions through the Martian atmosphere and then through various thicknesses of regolith. The largest reduction in dose occurs in the first 15-20 cm of regolith material.

Simonsen, L. C.↗
NASA NTRS1991

Practical response to radiation assessment for spacecraft design

An innovative radiative assessment system that combines the advantages of computer-aided design and enhanced radiative transport codes is described. An analysis of a Space Station habitat module is carried out. A scheme that makes it possible to account for anisotropies existing in the radiation environment of LEO is developed.

Appleby, M. H.↗
NASA NTRS1989

A concept for using the external tank from a National Space Transportation System (NSTS) for a lunar habitat

A concept for using the external tank from a National Space Transportation System for a lunar habitat is described. The tank is inserted in low earth orbit where it is outfitted as a 12-person lunar habitat. The tank modifications utilize existing structures and openings for man access without compromising the structural integrity of the tank. The modifications include installation of living quarters, instrumentation, and airlock; and thermal-control, environmental-control and life-support, and propulsion systems. The habitat is designed for unmanned transport to low lunar orbit and autonomously soft landed on the lunar surface. Supply to the habitat is provided by a space transfer vehicle and manned cargo lander. The lunar habitat concept is feasible by the year 2000 with the concurrent development of a space transfer vehicle and manned cargo lander for crew changeover and resupply.

King, C. B.↗
NASA NTRS1985

Transport processes in the stratosphere: Model simulations and comparisons with satellite observations

A three dimensional atmospheric model was used to study transport processes and to simulate the distribution of chemically active species in the stratosphere. The present results are part of a long term simulation of the seasonally varying structure of stratospheric trace constituents. The occurrence of a midwinter stratospheric warming and the associated transport of O3 and HNO3 during the simulation are described. Comparison of the simulated distributions of O3 and HNO3 are made with data from the Limb Infrared Monitor of the Stratosphere (LIMS) experiment. In addition, distributions of Ertel's potential vorticity on isentropic surfaces (IPV) are evaluated as a diagnostic for interpreting transport processes. Comparisons are made with IPV distributions inferred from LIMS temperature data.

Grose, W. L.↗
NASA NTRS1981

Analysis of UV protection requirements and testing of candidate attenuators for the Haloe optical instrument

Results of calculations are presented which simulate photolytic processes occurring in HALOE gas calibration cells exposed to extra-terrestrial solar ultraviolet photons. These calculations indicate that significant photolysis takes place in two of the sapphire-enclosed cells over the exposure periods of the proposed mission. A subsequent laboratory investigation is also described in which a high-voltage discharge hydrogen light source is used in conjunction with a vacuum ultraviolet spectrograph. The UV emission from this lamp was used to expose two candidate UV attenuators (ZnSe and coated Ge) to ascertain their suitability as UV filters while maintaining original infrared optical properties. Both materials were found to be effectively opaque to vacuum UV radiaton and suffered no adverse effects regarding their infrared transmissivity.

Nealy, J. E.↗
NASA NTRS1981

Solar UV variability - Effects on stratospheric ozone, trace constituents and thermal structure

The effect of long-term (11-year solar cycle) solar UV variability on stratospheric chemical and thermal structure has been studied using a time-dependent one-dimensional model. Previous studies have suggested substantial variations in local and total ozone, and in stratospheric thermal structure from solar minimum to solar maximum. It is shown that significant variations also occur in some of the trace constituents. Members of the HOx family and N2O exhibit the largest variations, and these changes, if detected, may provide additional means of verifying the presence of solar UV variability and its effects. Some of the species show large phase differences with the assumed solar flux variation. The role of chemical and transport time constants on the time variations of the trace species is examined. Comparisons with reported ozone and temperature data show reasonable agreement for the period 1960 to 1972.

Natarajan, M.↗
NASA NTRS1981

A statistical analysis of simulated data from potential stratospheric satellite missions

A simplified one-dimensional model is used to analyze simulated data from typical proposed satellite measurements of trace species in the stratosphere. Uncertainties are introduced in simulated species concentration measurements and applied to the basic physical and chemical model data. The results of the calculations are then used to predict uncertainties in the species concentrations computed by the model. Candidate satellite missions can be evaluated for net information acquired by applying the error analysis. An abbreviated depiction of the computational procedure is given, and sample histograms based on an accumulation of 200 calculations are shown for H2O2 and ClNO3, demonstrating that emergent species distributions are roughly Gaussian in the logarithm of number density. Calculated vertical concentration profiles for these two species are presented.

Nealy, J. E.↗
NASA NTRS1979

Ozone and temperature trends associated with the 11-year solar cycle

Evidence is presented which suggests that trends in the ozone concentration and stratospheric temperature, reported between the early 1960's and 1976, are to a large extent due to solar ultraviolet flux variability associated with the 11-year solar cycle. Radiative-convective-photochemical simulations of ozone and temperature variations have been made with a solar ultraviolet flux variability model. Results for temperatures and ozone concentrations, when compared with published data, show good agreement.

Callis, L. B.↗
NASA NTRS1979

A coupled radiative-convective-photochemical model of the stratosphere

A one-dimensional atmospheric model is described. The neutral photochemical processes of the troposphere and stratosphere are presented by a reaction set of 87 kinetic processes and 28 photolytic reactions, with vertical transport being taken into account by an eddy diffusion parameter. The vertical temperature profiles are coupled with the chemical calculations by means of a radiative-convective code. The model has the capability of including effects of multiple scattering and diurnal variations in species concentrations. The numerical solution methodology is described in detail, and current input data are given along with results obtained in a sample calculation.

Boughner, R. E.↗
NASA NTRS1978

Solar UV variability and its effect on stratospheric thermal structure and trace constituents

Observational evidence suggests the presence of solar UV variability in the spectral range 0.175-0.310 micron during the 11-year solar cycle. The present paper reports the results of a study using a steady-state 1-D radiative-convective-photochemical model conducted to determine the response of stratospheric temperatures and O3, O(1D), O(3P), and N2O constituent distributions to UV variability. Results show that concentrations of constituents and the thermal structure may be altered significantly for the altitude interval between 20 and 55 km.

Callis, L. B.↗
NASA NTRS1977

The effect of UV variability on stratospheric thermal structure and trace constituents

The paper examines the effect of observed UV flux variability in the spectral region of 0.175-0.3 microns on: (1) atmospheric concentrations of O3, O(1 D), OH, NO2, HNO3, and N2O; (2) stratospheric temperature structure; and (3) the calculated surface temperature. It is shown that perturbations in the number densities of the above constituents may be as large as 90 percent and that temperature deviations may range from 2 to 8 K for the altitude interval 20-40 km. These results have been determined using a 1-D radiative-convective-photochemical model.

Callis, L. B.↗
NASA NTRS1976

Tables and charts of equilibrium thermodynamic properties of ammonia for temperatures from 500 to 50,000 K.

Equilibrium thermodynamic properties for pure ammonia were generated for a range of temperature from 500 to 50,000 K and pressure from 0.01 to 40 MN/sq m and are presented in tabulated and graphical form. Properties include pressure, temperature, density, enthalpy, speed of sound, entropy, molecular-weight ratio, specific heat at constant pressure, specific heat at constant volume, isentropic exponent, and species mole fractions. These properties were calculated by the method which is based on minimization of the Gibbs free energy. The data presented herein are for an 18-species ammonia model. Heats of formation and spectroscopic constants used as input data are presented. Comparison of several thermodynamic properties calculated with the present program and a second computer code is performed for a range of pressure and for temperatures up to 30,000 K.

Simmonds, A. L.↗
NASA NTRS1975

Absolute calibration of a hydrogen discharge lamp in the vacuum ultraviolet

A low-pressure hydrogen discharge lamp was calibrated for radiant intensity in the vacuum ultraviolet spectral region on an absolute basis and was employed as a laboratory standard source in spectrograph calibrations. This calibration was accomplished through the use of a standard photodiode detector obtained from the National Bureau of Standards together with onsite measurements of spectral properties of optical components used. The stability of the light source for use in the calibration of vacuum ultraviolet spectrographs and optical systems was investigated and found to be amenable to laboratory applications. The lamp was studied for a range of operating parameters; the results indicate that with appropriate peripheral instrumentation, the light source can be used as a secondary laboratory standard source when operated under preset controlled conditions. Absolute intensity measurements were recorded for the wavelengths 127.7, 158.0, 177.5, and 195.0 nm for a time period of over 1 month, and the measurements were found to be repeatable to within 11 percent.

Nealy, J. E.↗
NASA NTRS1975

An experimental study of ultraviolet radiation behind incident normal shock waves in CO2 at Venusian entry speeds

Radiation intensity profiles behind incident normal shock waves in pure CO2 have been measured spectroscopically in the Langley Arc-Driven Shock Tube. These profiles, which were obtained for shock velocities between 9 and 13 km/sec and ambient densities corresponding to Venus altitudes between 100 and 80 km, were measured in the vacuum ultraviolet regime. Wavelengths of 127.7, 158.0, 177.5, and 195.0 nm were monitored simultaneously using a four-channel vacuum spectrograph equipped with sodium-salicylate-coated photomultipliers, thereby including the CO(4+) band system which is the most prominent radiator. Measured nonequilibrium overshoots are modeled to provide a means of estimating the effect of nonequilibrium radiation heating to the stagnation region of proposed aero-shells for Venusian entry. These results indicate a significant increase in radiative heating due to nonequilibrium effects. The measurements are believed to represent the most accurate data available on the effect of nonequilibrium radiative heat transfer for Venus entry. This accuracy is primarily due to improved spectrographic instrumentation, which is discussed in some detail regarding its application in related studies.

Nealy, J. E.↗
NASA NTRS1975

A computer program for calculation of spectral radiative properties of gas mixtures

A computer code is described whereby calculations of radiative properties of gas mixtures may be made. The program is arranged so that distinct radiative processes for each species are computed in individual subroutines. Provision is made for calculating radiative properties in nonequilibrium situations - separate rotational, vibrational, and electronic temperatures may be used. These features should provide a flexibility not currently available in such programs. The basic equations and the program listing in FORTRAN 4 language are presented. Sample calculations are given for high temperature air and carbon dioxide and are compared to calculations made with previously developed programs.

Nealy, J. E.↗