Rice team crunches numbers to smooth astronauts’ landings

Rice team crunches numbers to smooth astronauts’ landings
NASA parachutes get a lift from Rice engineers

By MIKE WILLIAMS
Special to the Rice News

Parachutes are tried and true, but there’s always room for improvement. With that in mind, a Rice professor and his team are working for many happy landings for NASA’s future astronauts.

Tayfun Tezduyar, Rice University’s James F. Barbour Professor in Mechanical Engineering and Materials Science and an expert in computer modeling of fluid-structure interactions and parachute aerodynamics, is helping optimize the parachute system that will return NASA’s next-generation Orion crew exploration vehicle safely to land or sea.

Employing the computational prowess of Rice’s Cray XD1 supercomputer, Tezduyar and his Team for Advanced Flow Simulation and Modeling (http://www.mems.rice.edu/TAFSM/) have spent two years simulating the performance of the three-parachute system that will be used to land the capsule.

The goal is to simulate the fluid dynamics through and around the parachutes, the dynamics of the parachute structure and the interaction between the two. This fluid–structure interaction modeling will help improve the performance of the parachutes and make the landing more comfortable for the astronauts — as many as six of them — when the missions begin with flights to the international space station in 2014. In 2020, NASA hopes to send four astronauts on board Orion to the moon.

The three parachutes Orion will deploy are no small things. Though the design is in the testing stage, they’re expected to be approximately 120 feet in diameter each, and collectively they must be able to slow a payload of roughly 17,000 pounds to about 23 feet per second for landing.

“When it comes to fluid–structure interaction modeling of parachutes, we are the leading group in the world,” said Tezduyar, noting his previous experience with computer modeling of parachutes for the U.S. Army. “We’re studying the parachute’s reefed and fully open configurations. Even the fully open configuration is dynamic due to the unsteady nature of the interaction between the fluid and structural dynamics.”

“The geometric complexity of Orion’s parachutes, with their component “rings” and “sails,” makes the computer modeling very challenging. Through the special methods Tezduyar and his team developed in recent years, they have overcome these challenges.

With these fluid-structure interaction modeling techniques, the team was able to compute and animate airflow around and through the parachute for varying conditions, including the early, or “reefed,” stages of deployment. Tezduyar explained Orion’s parachutes are designed to reach their fully open configurations gradually, slowing the craft by degrees rather than slamming on the brakes.

Another calculation told the team how far the capsule is likely to drift if side winds are present above the landing site — a good thing to know if you want to be on target.

Tezduyar said NASA might consider cutting the capsule’s weight, perhaps by jettisoning its heat shield just before touching down, reducing the landing speed. For the astronauts on board, the slower the better. The team’s simulations include that scenario.

Tezduyar’s vision extends far beyond bringing humans back from the moon. “The fluid–structure interaction modeling techniques and computer programs we have developed represent a very general-purpose technology,” he said of his team’s methods, which have also been used to study in fine detail the arterial dynamics and blood flow for aneurysms, potentially deadly distortions of blood vessels.

“There’s a spectrum of applicability from arterial dynamics to parachutes. Most people might not right away see a relationship between the two, but when it comes down to computational technology, there is. And in fact, for us, modeling arterial dynamics is relatively simpler.”