Rich Lueptow

Cassini orbiter

The Cassini orbiter

Exploring the depths of space

Research helps solve key problems for missions to Mars, Saturn, and beyond

“To boldly go where no man has gone before.”

It’s a lofty goal, and a logistical nightmare. As scientists prepare spacecraft to explore the universe, they are challenged with designing for environments where there are often more questions than answers. Two projects from Richard Lueptow, professor and interim chair of mechanical engineering, are providing tools to help NASA and the European Space Agency clear key hurdles in their quest to explore our universe through manned and unmanned space missions.

One of the foremost challenges facing NASA engineers preparing for a manned mission to Mars is the ability to provide clean drinking water for the astronauts. “These missions are projected to be two to three years long, with at least three astronauts, probably more,” explains Lueptow. “When you have a crew of that size, it’s impossible to bring enough water along.”

In order to make a long-term space flight possible, washwater, flushwater, humidity condensate from the cabin atmosphere, and urine must be recycled. While there are a variety of ways to purify and reuse water, few meet the demanding needs presented by spaceflight — such as the ability to operate in zero gravity.

One common purification method here on Earth is reverse osmosis, a process in which water molecules are forced through a membrane with subnanometer pores that are impermeable to contaminants. Lueptow and his research team have developed a prototype water filtration system that makes reverse osmosis a viable option in space by using a cylindrical rotating filter. As Lueptow explains, the secret to their success is in the swirls.

“The rotation of a cylindrical filter generates vortices, or swirls, that constantly wash the dirt and contaminants off of the reverse osmosis membrane. If you don’t have these swirls, the pores eventually plug up with contaminants, or the contaminants build near the surface of the membrane.”

Using the advantages of the rotating filter, Lueptow’s system purifies water more efficiently than others. Traditional reverse osmosis typically recovers only 20 to 30 percent of the water; his prototype system is able to recover 80 to 90 percent. And at just six inches wide and four inches tall, the prototype filter module also saves space — an important consideration in the crowded confines of a spacecraft.

After eight years of work on the prototype filter, Lueptow and his team have transferred the technology to NASA’s Johnson Space Center in Houston for further testing. There, the Exploration Life Support Team will test the system under conditions that would be typical for space flight.

In addition to water recovery for manned space missions, Lueptow’s research has also found application for unmanned probes exploring the moons of Saturn. After publishing a paper about his work with NASA on the development of acoustic sensors for detecting gases in spacecraft cabin atmospheres, Lueptow was contacted by a team working on the Cassini-Huygens space probe to see if the same analytical techniques could be used to predict acoustical properties in the atmosphere of Titan, one of Saturn’s moons. The Cassini-Huygens mission is a collaboration of NASA’s Jet Propulsion Laboratory and the European Space Agency and consists of the Cassini orbiter and the smaller Huygens landing probe.

“We considered the gases that are present on Titan and thought we could absolutely predict the acoustics there,” Lueptow says. “The reason that this is important is that often there are acoustic sensors on these probes. For instance, on the Huygens probe, there’s a sensor that tracks changes as the probe moves through the atmosphere and lands on the surface.”

While some past probes have used acoustic sensors, they haven’t been standard on spacecraft, and there hasn’t been a clear understanding of the acoustics in different atmospheres. Lueptow’s modeling techniques, which are based on quantum mechanics and the kinetic theory of gases, gave scientists the tools they needed to predict the acoustical properties of an atmosphere in order to better use the data captured by the sensors. During descent, measurements of the speed of sound provide information on atmospheric composition and temperature. In addition, the sensors provide the ability to acoustically monitor thunder related to electrical storms, which can provide important data about an atmosphere.

Lueptow describes this project as an unintended yet exciting result of his collaborations with NASA. And his work is providing solutions that may bring us one step closer to a deeper understanding of our universe.

—Kyle Delaney