Crystal Growth Research On Space Shuttle Helps Industry And Paves Way For Future Experiments

A series of space shuttle crystal growth experiments led by a team from Rensselaer Polytechnic Institute is helping increase productivity in the iron and steel industry.

At the same time, Rensselaer's latest Isothermal Dendritic Growth Experiment, which is aboard the space shuttle Columbia flight this week, is serving as a testbed for the type of remote telescience that will be needed when scientists begin placing experiments on the International Space Station.

And the presence of a high-tech NASA control room on the Rensselaer campus is giving students in about 25 elementary, middle-school, and high-school classrooms a firsthand view of shuttle science.

Pure Science That Is Making a Difference

The IDGE team, led by Rensselaer professors Martin E. Glicksman and Matthew B. Koss, is studying the formation of dendrites, needle-like crystals shaped something like Christmas trees, which are formed when metals solidify. Understanding how conditions such as temperature affect growth rate and shape would help engineers design better foundry and casting processes.

But convective processes on Earth complicate dendrite formation, making it very difficult to isolate various parameters to understand how they affect the crystals. In the microgravity environment of a space shuttle, it is possible to study crystal formation without the complications caused by gravity. On the second and third United States Microgravity Payload (USMP) shuttle flights in 1994 and 1996, the IDGE team repeatedly solidified samples of succinonitrile under carefully controlled conditions. This material forms crystals much like many common metals such as sodium, calcium, and iron, known as "body-centered" because of the shape of their crystal lattice.

At a Nov. 12 briefing, held to describe the science planned for the upcoming shuttle flight, NASA officials were asked how five years of microgravity research has changed our lives. They referred the question to Glicksman, saying the IDGE is a good example of the impact microgravity research can have.

The data gathered on the first two flights was used to derive and verify scaling laws that tie process rate, temperature, and other parameters to the size and shape of the dendritic structure in materials such as iron and steel, Glicksman said. Information published after the first flight is already being used by engineers to build foundry and casting models, which translate directly into improved metals, he added.

Doru Stefanescu, a professor at the University of Alabama who has worked with industry, said such models have created quantitative leaps in productivity in the metal cast industry. Before computer models, casts were designed by trial and error, often requiring a week or two to test each variation.

With models derived with information such as that generated by the IDGE, the industry now can cast a product on computer screens, making changes until the desired results are achieved. This cuts design-to-pouring time from weeks to less than a day. Such productivity advances help industry keep jobs in the United States rather than moving them to areas where labor costs less, Stefanescu said.

On the current USMP-4 flight, the IDGE team will work with pivalic acid, which forms crystals with a "face-centered" structure like aluminum, gold, or silver. In addition, the variation of surface energy with respect to crystal structure is much stronger for pivalic acid than for succinonitrile. The surface energy is a critical property affecting how dendritic crystals form.

These pivalic acid tests are expected to help extend and verify the scaling laws and models, making it possible to build data bases for additional metals.

Testbed for Telescience

USMP-4 may carry the last microgravity shuttle experiments, with future research scheduled for the International Space Station. On the space shuttles, most experiments have been autonomous or have been controlled by astronauts. Improved equipment for sending images and data to Earth and commands to the experiments aboard the shuttle has made it possible to monitor and control experiments from the ground. To do this, scientists generally travel to the Marshall Space Flight Center in Huntsville, Ala., for the duration of the flight.

On the Space Station, however, experiments will frequently operate for six months or longer. Science teams clearly will not be able to leave university or industry labs and work at a NASA center for that long.

To solve that problem, NASA has been using the IDGE experiments to pioneer remote operation of telescience. In 1996, NASA established a control room on the Rensselaer campus and trained students to operate it. For the last few days of the experiment, the Rensselaer team took control of the experiment.

As a result of the success of that test, the science aboard the current flight will be controlled from Rensselaer for the entire 16 days of the flight. Thirty-six Rensselaer undergraduate and graduate students have been trained by NASA to assist in the control room, giving them an experience that would be impossible if the experiment were controlled from the Marshall Space Flight Center.

The Rensselaer experience has shown that when the Space Station is in operation, researchers will be able to participate in space experiments from their home campuses, Glicksman said.

The dramatic improvements in NASA's ability to conduct telescience can be seen by looking at the three IDGE flights. The 1994 experiment was one of the earliest to include downlinked television and extensive teleoperation. During that mission, the IDGE gathered data with two 35 mm cameras. The data from these cameras could not be evaluated until the mission was over and the film was recovered and developed.

But images also were sent to Earth during the mission by telescience, enabling the science team to make real-time adjustments in the experiment. This relatively unsophisticated system greatly reduced wasted photos and enabled the team to gather data from twice as many crystallization cycles, Glicksman said. On the second IDGE flight, an improved system sent back images that provided velocity data almost as good as the data from the 35 mm films. On USMP-4, video equipment has been added, which will provide additional information on dendrite dynamics.

Outreach to Local Schools

The presence of a functioning NASA control room on the Troy, N.Y., campus has also inspired a substantial outreach program to local schools.

"When I asked my students what were the words Neil Armstrong first spoke on the moon, one fellow answered "Yippee!"

"But that kind of summarizes the enthusiasm these kids have for this microgravity project," says Bob Lawrence, a middle-school teacher in Guilderland, N.Y.

His students are learning what it's like to become an astronaut and live and work in outer space.

Lawrence was one of 25 teachers who spent two weeks at Rensselaer this summer learning the secrets from engineers, scientists, and NASA experts.

These teachers are now using the wonders of microgravity to fire the imagination and improve the math and science skills of school children in five New York counties.

The children are building rockets, simulating microgravity with a Rensselaer-designed "drop tower," and performing mock interviews for the NASA space program.

The program will last most of the year, and they'll visit the campus during Rensselaer's participation in the 16-day shuttle flight. There, they will get a firsthand view of real microgravity science.

In a special discovery room, the students will view shuttle telemetry and download experiment data. They'll see what's happening at NASA ground control, watch NASA feeds from space, and eavesdrop on Rensselaer's own operations center. In addition, they will be briefed by members of the IDGE team.

"This partnership with one of the nations best universities is helping our schools meet New York's rigorous new standards for math, science, and technology education," says Ellen Sullivan, of the Greater Capital Region Teacher's Center. Sullivan helped develop the project in cooperation with the Rensselaer Center for Initiatives in Pre-College Education (CIPCE) and the IDGE team. NASA provided $30,000 in program support.