Engineering topics

Tucker, D. S.

Publications and source records attributed to Tucker, D. S..

7 records

NASA NTRS2017

Nuclear Rocket Ceramic Metal Fuel Fabrication Using Tungsten Powder Coating and Spark Plasma Sintering

Nuclear thermal propulsion is an enabling technology for crewed Mars missions. An investigation was conducted to evaluate spark plasma sintering (SPS) as a method to produce tungsten-depleted uranium dioxide (W-dUO2) fuel material when employing fuel particles that were tungsten powder coated. Ceramic metal fuel wafers were produced from a blend of W-60vol% dUO2 powder that was sintered via SPS. The maximum sintering temperatures were varied from 1,600 to 1,850 C while applying a 50-MPa axial load. Wafers exhibited high density (>95% of theoretical) and a uniform microstructure (fuel particles uniformly dispersed throughout tungsten matrix).

Barnes, M. W.↗

NASA NTRS2007

Vacuum Strength of Two Candidate Glasses for a Space Observatory

The strengths of two candidate glass types for use in a space observatory were measured. Samples of ultra-low expansion glass (ULE) and borosilicate (Pyrex) were tested in air and in vacuum at room temperature (20 C) and in vacuum after being heated to 200 C. Both glasses tested in vacuum showed an increase in strength over those tested in air. However, there was no statistical difference between the strength of samples tested in vacuum at room temperature and those tested in vacuum after heating to 200 C.

Manning, T. a.↗

NASA NTRS1998

Effects of Gravity on Crystallization of Fluorozircante Optical Fibers

ZBLAN (ZrF4-BaF2-LaF3-AlF3-NaF) optical fibers were flown on NASA's reduced gravity KC135 aircraft and Conquest I sub-orbital rocket. The purpose of these experiments was to determine the effects of gravity on the crystallization process of this material. Fiber samples encapsulated in evacuated quartz ampoules were heated to the crystallization temperature during flight in reduced gravity and on the ground in unit gravity. Scanning electron and transmission electron microscopy were utilized to study the crystallization behavior. Samples heated under unit gravity conditions exhibited significant crystallization, while fibers heated to the crystallization temperature in reduced gravity showed no signs of crystallization. A mechanism based on microcellular convection is proposed to explain these observed behaviors.

Tucker, D. S.↗

NASA NTRS1992

Glass fiber processing for the Moon/Mars program: Center director's discretionary fund final report

Glass fiber has been produced from two lunar soil simulants. These two materials simulate lunar mare soil and lunar highland soil compositions, respectively. Short fibers containing recrystallized areas were produced from the as-received simulants. Doping the highland simulant with 8 weight percent B2-O3 yielded a material which could be spun continuously. The effects of lunar gravity on glass fiber formation were studied utilizing NASA's KC-135 aircraft. Gravity was found to play a major role in final fiber diameter.

Tucker, D. S.↗

NASA NTRS1992

A reduced gravity fiber pulling apparatus

A reduced gravity fiber pulling apparatus (FPA) was constructed in order to study the effects of gravity on glass fiber formation. The apparatus was specifically designed and built for use on NASA's KC-135 aircraft. To date, four flights have been completed during which E-glass fiber was successfully produced in simulated lunar gravity.

Tucker, D. S.↗

NASA NTRS1991

Materials and processes laboratory composite materials characterization task, part 1. Damage tolerance

A test run was performed on IM6/3501-6 carbon-epoxy in which the material was processed, machined into specimens, and tested for damage tolerance capabilities. Nondestructive test data played a major role in this element of composite characterization. A time chart was produced showing the time the composite material spent within each Branch or Division in order to identify those areas which produce a long turnaround time. Instrumented drop weight testing was performed on the specimens with nondestructive evaluation being performed before and after the impacts. Destructive testing in the form of cross-sectional photomicrography and compression-after-impact testing were used. Results show that the processing and machining steps needed to be performed more rapidly if data on composite material is to be collected within a reasonable timeframe. The results of the damage tolerance testing showed that IM6/3501-6 is a brittle material that is very susceptible to impact damage.

Nettles, A. T.↗

NASA NTRS1991

Proof test diagrams for Zerodur glass-ceramic

Proof test diagrams for Zerodur glass-ceramics are calculated from available fracture mechanics data. It is shown that the environment has a large effect on minimum time-to-failure as predicted by proof test diagrams.

Tucker, D. S.↗