As NASA continues to focus on sending explorers to Mars, two scientists at UMR are working on ways to house the astronauts when they arrive on the red planet by building with Martian minerals.
"When we begin to think about going to places like Mars beyond the moon for more than an hour’s visit, we will have to utilize some of the resources that are there," says Dr. Delbert Day, Curators’ Professor emeritus of ceramic engineering at UMR. "Astronauts can stay in the landing vehicle for a short time, but eventually we’ll need to construct some type of structure for people to stay in."
Because of the limited resources available on Mars, Day and Dr. Chandra Ray, research professor of ceramic engineering at the Graduate Center for Materials Research at UMR, are examining the properties of glass formed by melting simulated Martian soil. "You can think of it as making concrete without cement," Day explains. "You would gather up Martian soil and rocks and then glue them together with glass, rather than cement. A solar furnace could be the source of heat to melt the material."
What remains unknown is how the lower gravity field would affect the process of forming glass. Day and Ray have conducted glass-melting experiments for more than 20 years, including two aboard the space shuttle Challenger in the mid-1980s, and plan to conduct another experiment on the International Space Station in the future.
"There are many things on Earth that interfere with our study of the crystallization process," Day explains. "On the Earth, any liquid has to be held within some type of container and those container walls can cause crystals to grow. When you heat water in a pan, the bubbles always form at the wall first."
For the experiments aboard the space shuttle Challenger, the researchers used an acoustic levitator to hold a suspended molten drop for long periods of time. "Sound waves are just little pressure waves," Day says. "We can put a small sample the size of a pea at one of the low pressure points in the furnace and if the sample tends to drift out of that spot, it encounters higher pressure that forces the sample back to where we want it."
The surprising result of these first experiments was that when melts in space were cooled, they tended to form glass easier than what they did on Earth. In other words, fewer crystals were formed in the glass. For the International Space Station experiment, the researchers want to explore why fewer crystals formed, because gravity is not included in the mathematical equations that govern the crystallization of a melt.
No one has actually heat-treated a glass in space and on Earth in an identical manner, and then measured the nucleation rate and the crystal growth rate for the two samples, Day says. "Our experiment is designed to provide that data for the first time," Day says. "We believe the crystals will grow slower and the nuclei will form less rapidly. If that occurs, we need to re-examine the rather complicated mathematical equations that govern these processes and determine how they need to be modified for a change in gravitational force."
Ray is currently studying the properties of simulated Martian soils using an electrostatic levitator at NASA’s Marshall Space Flight Center in Alabama as part of the Intergovernmental Personnel Program. An electrostatic levitator uses an electrical field between two electrodes to hold the levitated sample in place. Lasers then zap (heat) the material, turning it into a floating molten sphere that can later cool without ever touching a container.
"Before the time of space travel, we didn’t care about gravity and glass melting because all glass melting was done on Earth," Day says. "We take advantage of gravity in a lot of the processing that we do with glass on Earth, such as removing gas bubbles. But the gravity on Mars is 60 percent less than it is on Earth, so we need to know how differences in gravity might affect the way glass can be processed on other planets. Using the resources located on a planet is one of the important challenges to be met in establishing a permanent presence on any planet."