Engineering topics

Hwang, B.

Publications and source records attributed to Hwang, B..

5 records

NASA NTRS1978

Rocket exhaust ground cloud/atmospheric interactions

An attempt to identify and minimize the uncertainties and potential inaccuracies of the NASA Multilayer Diffusion Model (MDM) is performed using data from selected Titan 3 launches. The study is based on detailed parametric calculations using the MDM code and a comparative study of several other diffusion models, the NASA measurements, and the MDM. The results are discussed and evaluated. In addition, the physical/chemical processes taking place during the rocket cloud rise are analyzed. The exhaust properties and the deluge water effects are evaluated. A time-dependent model for two aerosol coagulations is developed and documented. Calculations using this model for dry deposition during cloud rise are made. A simple model for calculating physical properties such as temperature and air mass entrainment during cloud rise is also developed and incorporated with the aerosol model.

Hwang, B.↗

NASA NTRS1978

A Simulation Model of the Planetary Boundary Layer at Kennedy Space Center

A simulation model which predicts the behavior of the Atmospheric Boundary Layer has been developed and coded. The model is partially evaluated by comparing it with laboratory measurements and the sounding measurements at Kennedy Space Center. The applicability of such an approach should prove quite widespread.

Hwang, B.↗

NASA NTRS1978

A comparative study of tropospheric ground cloud diffusion models

Calculated values obtained from several diffusion models are compared with field measurements. The diffusion models that are examined include: NASA/MSFC multilayer diffusion models, the meteorological effluent transport simulation model, the TREATS model, the atmsopheric diffusion particle in cell model, and a model for diffusion in shear flow (DISF). The atmospheric turbulence in the PBL turbulent wind field above and below 150 m is calculated. Concentrations calculated from the DISF model are found to correlate, in general, quite well with flight measurements.

Hwang, B.↗

NASA NTRS1976

Environmental Effects of Space Shuttle Solid Rocket Motor Exhaust Plumes

The deposition of NOx and HCl in the stratosphere from the space shuttle solid rocket motors (SRM) and exhaust plume is discussed. A detailed comparison between stratospheric deposition rates using the baseline SRM propellant and an alternate propellant, which replaces ammonium perchlorate by ammonium nitrate, shows the total NOx deposition rate to be approximately the same for each propellant. For both propellants the ratio of the deposition rates of NOx to total chlorine-containing species is negligibly small. Rocket exhaust ground cloud transport processes in the troposphere are also examined. A brief critique of the multilayer diffusion models (presently used for predicting pollutant deposition in the troposphere) is presented, and some detailed cloud rise calculations are compared with data for Titan 3C launches. The results show that, when launch time meteorological data are used as input, the model can reasonably predict measured cloud stabilization heights.

Hwang, B.↗

NASA NTRS1975

NO sub X Deposited in the Stratosphere by the Space Shuttle Solid Rocket Motors

The possible effects of the interaction of the plumes from the two solid rocket motors (SRM) from the space shuttles and mixing of the rocket exhaust products and ambient air in the base recirculation region on the total nitrous oxide deposition rate in the stratosphere were investigated. It was shown that these phenomena will not influence the total NOx deposition rate. It was also shown that uncertainties in the particle size of Al2O3, size distributions and particle/gas drag and heat transfer coefficients will not have a significant effect on the predicted NOx deposition rate. The final results show that the total mass flow of NOx leaving the plume at 30 km altitude is 4000 g./sec with a possible error factor of 3. For a vehicle velocity of 1140 meter/sec this yields an NOx deposition rate of about 3.5 g./meter. The corresponding HCl deposition rate at this altitude is about a factor of 500 greater than this value.

Pergament, H. S.↗