Defying zero gravity

PSU helps astronauts keep their fluids down

While many of us filter through our emails each morning over a cup of coffee, Portland State Mechanical and Materials Engineering professor Mark Weislogel and his team of graduate students get emails from space.

PSU helps astronauts keep their fluids down


Brentley Wiles sets up the antigravity experiment in the Dryden Drop Tower. The tower is 102 feet tall and simulates zero gravity.

While many of us filter through our emails each morning over a cup of coffee, Portland State Mechanical and Materials Engineering professor Mark Weislogel and his team of graduate students get emails from space.

While we daydream that one day our big ideas will be recognized, Weislogel’s students have theirs tested by NASA astronauts in orbit.

“My involvement with the PSU-based NASA research has been simply surreal,” graduate student William Blackmore said, referring to PSU’s ongoing communication with the astronauts aboard the International Space Station.

The astronauts are performing experiments designed by Weislogel, more of which were delivered earlier this month during the first commercial resupply mission in the history of space exploration.

On Oct. 10, Space Exploration Technologies shot an 882-pound cargo of supplies and science experiments into space, toward the space station. Along with various crew provisions, the rocket Dragon delivered the 50th round of experiments called Interior Corner Flow Vessels (ICF-2) created by Weislogel and his team.


Drew Wollman points out the Dryden Drop Tower.

Working in conjunction with NASA and Germany’s University of Bremen’s ZARM Institute, this shipment of supplies will allow astronauts to continue Weislogel’s work on how liquid responds in zero gravity.

“We are studying how fluids behave when gravity is gone,” Weislogel said. “We are studying the effects of wetting, spreading, surface tension and container shape on liquid configurations.” The purpose of these experiments is to find a way to modify containers so that liquid in space behaves the way it does on Earth.

“When gravity’s gone, where is the liquid in your stomach?” Weislogel asked. “It isn’t where you think it is. Where’s the liquid in the fuel tank? It’s not where you think it is. It can go anywhere.”

Living in a gravity-based world, this isn’t a concept we often ponder. But in space, making sure liquid is in the correct place is a weighty concern.

For example, consider accelerating a spacecraft: How can it move if the fuel isn’t in the right place?

“Currently what we do is we turn on the thrusters and we force it—put it in artificial gravity—so that all the liquid comes to the bottom. And these days that’s a big waste. The fuel should just be sitting there ready to use,” Weislogel said.

By using surface tension to replace the role of gravity, Weislogel and his students aim to remodel spacecraft for liquid efficiency. But since they are not in space themselves, they have to simulate zero gravity here on Earth.

More specifically, they have to simulate it on campus.

Running up the center of the stairwell in the bustling Engineering Building, the Dryden Drop Tower is a 102-foot-tall chute that allows the ICF-2 experiments, encased in a 253-pound box called a drag shield, to free fall for 73 feet. This allows the experiment to experience 2.13 seconds of microgravity. A camera enclosed with the ICF-2 records the results. The drag shield plummets with the force of 14 gravitational forces, landing right above the heads of students studying below.

“They’re used to it,” said Drew Wollman, an associate professor of Mechanical and Materials Engineering and part of Weislogel’s research team.

The ICF-2 experiment itself looks simple: a glass cylinder that has been tapered at the top end, looking similar to an eyedropper. Secured in a rigid frame, the cylinder is filled with fluid, placed in the drag shield and dropped in the tower. What the camera captures is video of a small liquid droplet shooting out the end of the tube during those 2.13 seconds of microgravity.

Previously, this kind of reaction was considered impossible. In a basic cylinder without a tapered end, the liquid in microgravity will rise to the top, but never gain enough energy to actually break free from the tube.

“The droplet shooting out of the tube in low gravity alone is a publishable thing. It means the fluid has enough energy in it to shoot itself,” Weislogel said. “We went nuts with it. It’s highly repeatable.”

According to Wollman, PSU is leading the way in this area of research. The department has done more than 1,000 drops this year, proving time and again that liquid in microgravity can be controlled using only surface tension provided by altering container shapes.

The drop tower and the engineering lab at PSU act as both an experimental and support facility for the astronauts aboard the space station, who perform the experiments as instructed by Weislogel and his team.

The lab itself looks like something from MythBusters, and is frequently abuzz with giddy engineers watching videos of droplets the way most people watch Ninja Warriors—with lots of animated commentary and exclamations.

A few doors down is the control room where Weislogel and his team monitor four live feeds from the ISS and watch video of the astronauts performing their experiments in real zero-gravity conditions.

“NASA enables [the students] to speak directly to the astronauts during the experiment,” Weislogel said. Several students have even visited NASA’s Johnson Space Center in Texas to train the astronauts.

“It’s one thing to participate in hands-on science in a lab—to have a visceral connection to the questions you are trying to answer. However, it’s quite another thing to train an astronaut in your experiment, watch them perform it in orbit, and have instant feedback on their observations,” Blackmore said.

“You feel as if anyone, even yourself, may be able to one day go to space and investigate some exciting and unknown science.”

While gravity is keeping their feet firmly planted on the ground, it’s exciting to see PSU students rewarded for having their heads in the stars.