Going with the flow: Michel Louge studies the science of granules

By Larry Klaes

NASA's recent mandate from the White House to place humans on Mars in the coming decades has led the space agency to intensify its studies of human physiology to ensure that astronauts making the long journey to the red planet remain in good health during their interplanetary voyage.

Michel Louge is more concerned about the landing.

Michel Louge, professor of mechanical and aerospace engineering, right, and Steve Keast, a research technician, stand by a prototype Keast created in Kimball Hall. Louge is using the prototype to conduct experiments to assess the impact of a large manned spacecraft landing on the Martian surface. Nicola Kountoupes/University Photography

The Cornell professor of mechanical and aerospace engineering has teamed up with Mark Hopkins of the U.S. Army Corps of Engineers and Phil Metzger of NASA's Kennedy Space Center to draw the space agency's attention to the effect of a blast of retrorockets on the Martian surface as a large manned spacecraft slows to a soft landing.

"If you take the force of the retrorockets firing on the Martian surface minerals and their being flung across the ground on a planet with a gravity and atmosphere thickness much less than Earth's, then everything in a wide radius from the landing ship will get sandblasted," warns Louge.

Future spaceships would have to land far away from a Mars base, once it was established, creating travel and fueling issues. "Perhaps landing on Mars with a plane would be the key," Louge speculates.

Assessing the impact of spaceships on the Martian surface is only one area of Louge's expertise. He has also studied how to make fuels cleaner and more efficient, how to prevent mud and snow avalanches, and how encroaching sand dunes affect the environment.

All of these areas concern the study of granular flow -- a subject, said Louge, that "spans all three aspects of matter: solid, liquid and gas."

One of the best ways to study the interactions of matter in these phases is in the state of weightlessness called microgravity. Studying the flow of materials in a reduced or near zero level of gravity "helps us to see the trees for the forest," explained Louge.

One NASA research project that Louge conducted with colleague James Jenkins, the W.S. Carpenter Jr. Professor of Engineering, over eight years was how grains -- microscopic solids of two sizes or two densities -- collide and separate when agitated. From this, Louge said, researchers hope to learn how to improve the mixing of granular materials and to prevent them from separating, both on Earth and in space. The experiment involved the use of one of the few places besides space where the near absence of Earth's massive pull can be counteracted, even if for only a few brief moments.

The microgravity environment was achieved in a modified KC-135A aircraft, part of NASA's Reduced Gravity Research Program, which made a series of sharp dives to simulate brief periods of weightlessness, usually lasting no more than 20 seconds. "Reducing or removing the gravity is the only way to study how velocity fluctuation can separate solid particles," said Louge.

While working on the microgravity project, Louge and his then-student Michael Adams came across an interesting phenomenon: When a solid ball was bounced against certain flexible surfaces at an angle, the ball shot back up with a greater vertical velocity than it was originally given.

The action seemed to defy the laws of physics. "At first we thought our data was wrong," explained Louge.

More tests soon showed that Louge and Adams were seeing something real. It turned out that with certain surfaces like Lexan, the polycarbonate resin actually flows under the angled impact of the solid sphere, forming some of the plastic into a shape that shoots the ball away from the plate faster than it arrived.

It was, said Louge, "like a ski jump."