NASA Scientific and Technical Aerospace Reports

density and microstructure uniformity have improved. 2 in. dia. x 2 in. tall UHTC billets have been successfully hot pressed:
scaled up billets have slightly higher density gradients axially than 1 in. billets. Hot press schedule has not been optimized
for scaled up billets. Strengths and strength distributions are improving with experience: need to evaluate strength uniformity
in the center of the billets. CTE or ARC materials compares favorably with heritage materials. Thermal conductivity of ARC
materials considerably different than that of heritage materials.
Derived from text
Hot Pressing; Thermal Conductivity; Billets
20040045298 NASA Ames Research Center, Moffett Field, CA, USA
Materials Science Work at NASA Ames Research Center
Kuhns, Joy B.; Johnson, Sylvia; Stackpoole, Mairead; Loehman, Ron; Kotulas, Paul; [2003]; 29 pp.; In English
Report No.(s): Rept-90; No Copyright; Avail: CASI; A03, Hardcopy
The paper discusses the following: Thermal Protection System -TPS development and testing; Material for the shuttle;
Ablators; Coating; Integrated vehicle health management; Sharp leading edges.
CASI
Management Planning; Ablative Materials; Thermal Protection; Performance Tests
20040045326 NASA Glenn Research Center, Cleveland, OH, USA
The Effects of an Unsteady Reduced Gravity Environment on the Soldering Process
Struk, Peter M.; Pettegrew, Richard D.; Downs, Robert S.; Watson, J. Kevin; February 2004; 16 pp.; In English; 42nd
Aerospace Sciences Meeting and Exhibit, 5-8 Jan. 2004, Reno, NV, USA
Contract(s)/Grant(s): WBS 22-101-58-10
Report No.(s): NASA/TM-2004-212946; E-14386; AIAA Paper 2004-1311; No Copyright; Avail: CASI; A03, Hardcopy
An improved understanding of the effects of reduced gravity is important to applications of soldering during both current
and future human space missions. Recently, we conducted a series of manual soldering experiments aboard NASA’s KC-135
reduced gravity aircraft. This paper focuses on the interpretation of the unsteady (g-jitter) acceleration environment measured
aboard the aircraft as it affects the experimental results. The results presented here use a through-hole geometry that was
soldered with the same hardware that is currently on orbit aboard the International Space Station. As presented elsewhere, we
observed significant changes in porosity and geometry of solder joints formed in reduced gravity. Based on acceleration
measurements during periods when the solder was molten, we examined a data filtering technique to determine the influence
of g-jitter on our data. The results of this filter indicate that joint geometry is largely unaffected by the unsteady variations in
acceleration as seen aboard the KC-135. We deduced that the increase in voids observed in low gravity can be described by
decreases in buoyancy driven bubble motion. An acceleration environment which oscillates about zero gravity further
increases joint porosity by keeping bubbles within the joint. Additionally, by examining some partial gravity results we
observed that acceleration levels near Martian levels and higher result in porosity data sets similar to our normal gravity
results. This suggests the existence of a threshold acceleration level below which gravitational effects become important for
joint porosity in the though-hole geometry. The techniques and interpretations presented in this paper may be beneficial to
others using the KC-135 research aircraft.
Author
Soldering; Microgravity; Space Missions; Mars (Planet); Unsteady State; Gravitational Effects
20040046907 Containerless Research, Inc., Evanston, IL, USA
Microgravity Studies of Liquid-Liquid Phase Transitions in Alumina-Yttria Melts
Guynes, Buddy, Technical Monitor; Weber, Richard; January 31, 2004; 11 pp.; In English
Contract(s)/Grant(s): NAS8-98092; No Copyright; Avail: CASI; A03, Hardcopy
The scientific objective of this research is to increase the fundamental knowledge base for liquid- phase processing of
technologically important oxide materials. The experimental objective is to define conditions and hardware requirements for
microgravity flight experiments to test and expand the experimental hypotheses that: 1. Liquid phase transitions can occur in
undercooled melts by a diffusionless process. 2. Onset of the liquid phase transition is accompanied by a large change in the
temperature dependence of melt viscosity. Experiments on undercooled YAG (Y3A15012)- and rare earth oxide aluminate
composition liquids demonstrated a large departure from an Arrhenian temperature dependence of viscosity. Liquid YAG is
nearly inviscid at its 2240 K melting point. Glass fibers were pulled from melts undercooled by ca. 600 K indicating that the
viscosity is on the order of 100 Pans (1000 Poise) at 1600 K. This value of viscosity is 500 times greater than that obtained
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