testing them in an environment free of contamination by fluid convection, sedimentation, and hydrostatic pressure.

In particular, experiments in this program have been directed at producing benchmark data sets or testing fundamental theories. Examples of OBPR-funded research in materials science include studies of the role of liquid convection in crystal growth, including its influence on impurities and crystal perfection; isothermal dendritic growth; directional solidification; gravitational effects on distortion during sintering; the accurate measurement of thermophysical properties needed for the computer-aided modeling of manufacturing processes; the formation of metallic glasses (amorphous metals); and the exploration of new and innovative ways to process materials (Sekerka, 2001a). To date, fundamental knowledge of the role of convection in crystal growth has been applied to the production of melt-grown silicon crystals (as a source of substrates for integrated circuits), with an increase in yield approaching two orders of magnitude (Sekerka, 2001b). Scientific research on isothermal dendritic growth in microgravity has established a basis for assessing the validity of competing theories of dendrite growth. Liquid-phase sintering studies in microgravity are expected to provide design parameters for the low-cost fabrication of parts, for example, automobile connecting rods.

The quality of the materials science research funded through the physical sciences program is uniformly high. This is reflected, for example, in the scientific stature of current and previous NASA principal investigators (PIs).3

Impact of ISS Changes

In the Rev. E (June 1999) Assembly Sequence and Research Outfitting design, the dedicated Materials Science Research Rack 1 (MSRR1) was scheduled for delivery to the ISS in February 2003. In Rev. E, the second and third dedicated materials science research racks (MSRR2 and MSRR3) were deferred to 2005 or later. In Rev. F (August 2000), MSRR1 was scheduled for September 2004, a slippage of 19 months. In Rev. F, MSRR2 and MSRR3 were deferred to 2006 or later. Subsequently, in the Core Complete design, MSRR1 is scheduled for January 2005 with an attendant slippage of 4 months, while MSRR2 and MSRR3 are canceled.

The microgravity research program selected 26 materials science flight investigations for execution through 2008 (Wargo, 2002). Eighteen of these flight investigations were to utilize MSRR1, MSRR2, or MSRR3; three investigations were to be carried out in the Microgravity Science Glovebox (MSG) facility, two investigations in the European Electromagnetic Levitation (EML) facility, two in the Japanese Electrostatic Levitation (ESL) facility, and one in the French DECLIC apparatus.

In terms of materials science, the reduction in the NASA ISS research capability budget translated into the elimination of MSSR2 and MSSR3, with attendant cancellation of equipment. The one remaining piece of NASA-provided equipment for MSRR1 is the Quench Module Insert, which will be inserted into the Materials Science Laboratory planned to be built by the European Space Agency (ESA). NASA’s rationale for the elimination of MSRR2, MSRR3, and 10 experimental modules (Robey, 2001) is that substantial funding is associated with these facilities, coupled with the fact that each facility was scheduled far enough into the future to avoid the lay-off of current employees. In addition, the resource analysis from the ISS program office at the Johnson Spaceflight Center (JSC) indicated that activities in the materials science research racks were more crew-intensive than those in the other physical sciences flight research programs (Trinh, 2002a).

NASA reports that as of April 10, 2002, 12 flight investigations remained in the OBPR materials science program (Wargo, 2002) (see Appendix A). Nevertheless, only part of the original proposed scope of work can be conducted in each investigation. This limit on scope will adversely affect the level of meaningful research that can be performed in materials science. Seven flight investigations will use the

3  

Seven are members of the National Academy of Engineering, two are members of the National Academy of Sciences, and five are fellows of the Metals, Minerals, and Materials Society.



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