Engineering topics

Ries, Heidi R.

Publications and source records attributed to Ries, Heidi R..

5 records

NASA NTRS1997

Transpiration Cooling Experiment

The transpiration cooling method was considered for a scram-jet engine to accommodate thermally the situation where a very high heat flux (200 Btu/sq. ft sec) from hydrogen fuel combustion process is imposed to the engine walls. In a scram-jet engine, a small portion of hydrogen fuel passes through the porous walls of the engine combustor to cool the engine walls and at the same time the rest passes along combustion chamber walls and is preheated. Such a regenerative system promises simultaneously cooling of engine combustor and preheating the cryogenic fuel. In the experiment, an optical heating method was used to provide a heat flux of 200 Btu/sq. ft sec to the cylindrical surface of a porous stainless steel specimen which carried helium gas. The cooling efficiencies by transpiration were studied for specimens with various porosity. The experiments of various test specimens under high heat flux have revealed a phenomenon that chokes the medium flow when passing through a porous structure. This research includes the analysis of the system and a scaling conversion study that interprets the results from helium into the case when hydrogen medium is used.

Song, Kyo D.↗

NASA NTRS1996

An Integrated Approach to Laser Crystal Development

Norfolk State University has developed an integrated research program in the area of laser crystal development, including crystal modeling, crystal growth, spectroscopy, and laser modeling. This research program supports a new graduate program in Chemical Physics, designed in part to address the shortage of minority scientists.

Ries, Heidi R.↗

NASA NTRS1993

Materials education activities

Last year, at NEW: Update '91, a panel discussion was held to address the unique difficulties of attracting and retaining minorities and women in technical studies. Unfortunately, retention in technical majors is a problem of varying proportions for the entire student population, and must be improved in order to maintain the strength of the nation's industrial base. To investigate the cause of student attrition in technical majors, in-depth interviews of both current and former (non-graduating) engineering students at four colleges and universities in Colorado were conducted by Hewitt and Seymour. They found that there was no significant difference in the level of high school preparation and undergraduate academic performance in these two groups, despite the prevailing faculty perception that most students who switch from technical to nontechnical majors were underprepared. The majority of engineering students who changed majors reported that they were turned off by science, while one-third complained of poor teaching.

Ries, Heidi R.↗

NASA NTRS1990

Dielectric determination of the glass transition temperature (T sub g)

The objective is to determine the glass transition temperature of a polymer using a dielectric dissipation technique. A peak in the dissipation factor versus temperature curve is expected near the glass transition temperature T sub g. It should be noted that the glass transition is gradual rather than abrupt, so that the glass transition temperature T sub g is not clearly identifiable. In this case, the glass transition temperature is defined to be the temperature at the intersection point of the tangent lines to the dissipation factor versus temperature curve above and below the transition region, as illustrated.

Ries, Heidi R.↗

NASA NTRS1986

Electron-radiation effects on the ac and dc electrical properties and unpaired electron densities of three aerospace polymers

The effects of gigarad-level total absorbed doses from 1-MeV electrons on the post-irradiation alternating-current (ac) and direct-current (dc) electrical properties and the unpaired electron densities have been studied for Kapton, Ultem, and Mylar. The unpaired electron densities (determined from electron paramagnetic resonance spectroscopy) and the dc electrical conductivities of the irradiated materials were monitored as functions of time following the exposures to determine their decay characteristics at room temperature. The elevated-temperature ac electrical dissipations of the Ultem and Mylar were affected by the radiation. The dc conductivity of the Kapton increased by five orders of magnitude, while the dc conductivities of the Ultem and Mylar increased by less than an order of magnitude, due to the radiation. The observed radiation-generated changes in the ac electrical dissipations are explained in terms of known radiation-generated changes in the molecular structures of the three materials. A preliminary model relating the dc electrical conductivity and the unpaired electron density in the Kapton is proposed.

Long, Sheila Ann T.↗