CU Boulder research in zero g during parabolic flight

Caroline Austin is floating up from her airplane seat toward the ceiling.

And so is everyone else on the flight.

Austin, an aerospace PhD student, is experiencing microgravity as part of a parabolic flight campaign. She is part of a three-member University of Colorado Boulder team testing experiments that would otherwise only be possible in space.

Before the day is done, they will have taken part in 20 parabolas in the skies east of Dubendorf, Switzerland, aboard a modified Cessna Citation II jet, each time experiencing about 15 seconds of microgravity and 20-25 seconds of hyper gravity (2.5G).

Now safely back in Boulder, Austin, fellow PhD student Renée DePencier Piñero, and Postdoctoral Researcher Aaron Allred are sharing details of the flight, including the science and personal experience of weightlessness.

“It was definitely a bucket list item to do a parabolic flight,” Austin said.

“I’d absolutely do it again,” said DePencier Piñero, who is also a Smead Scholar.

“It’s very cool, and there is nothing I can compare it to, in terms of other human experiences,” Allred said. “It was also really cool to be doing experiments you’re invested in.”

“I think the experiment was cooler than the parabolas,” Austin added.

She is not kidding.

Allred and DePencier Piñero aboard the plane.

Allred and DePencier Piñero preflight.

The flight pilots at altitude flying above the clouds.

Both pilots, during a lull above the clouds.

Austin aboard the plane preflight.

Experiments at Altitude

The team, all part of the Ann and H.J. Smead Department of Aerospace Engineering Sciences, combined microgravity, virtual reality goggles with a custom gamified interface, and a galvanic vestibular stimulator to test responses of the human vestibular system—contributing to your sense of balance—in scenarios relevant to space travel.

The vestibular system, which is part of your inner ear, relies heavily on gravity. When astronauts reach orbit, the sudden lack of it can cause motion sickness. The brain eventually adapts, but it takes time.

The research aims to build a robust standard for tracking that adaptation to guide space mission planning. It also has relevance here on earth for senior citizens and others with balance issues.

“The goal of this tool is to capture how the brain and vestibular system change during spaceflight,” Allred said. “It’s something that is very hard to test with actual astronauts because the crew is busy doing other things during the adaptation window when they first get to space.”

How It Worked

In the parabolic flight experiments, the trio took part in spatial orientation tasks while subject to visual and vestibular stimuli producing changes in perceived orientation.

The experiment used combinations of three variables: parabolic flight; VR headsets showing a scene which can induce a visual sensation of movement; and electric galvanic vestibular stimulators, with electrodes placed behind the ears which can cause a vestibular-driven sensation of moving.

“When it is turned on, it can make you feel like you’re tilting sideways. I’m also one of the people who can feel the electrical stimulation on my skin as a tingling or zapping sensation. That type of skin sensation varies from person to person,” DePencier Piñero said.

By tracking perception in the presence of varying visual and vestibular stimuli, the research aims to better understand integration of multi-sensory cues and develop a first-of-its-kind assessment tool that can track how the brain adapts over time.

Motion Sickness

The experiments, unsurprisingly, can cause considerable motion sickness. Austin said they took extensive precautions to stay focused on the science.

“We were very conscious that each aspect of the experiment can cause motion sickness, and we were choosing to combine them. We ate lunch well before the flight, stayed away from extra snacks, took Meclizine pills, wore acupressure wristbands, had rubbing alcohol swabs, and medical grade vomit bags,” Austin said.

DePencier Piñero struggled the most, but all three emerged with their stomachs intact.

“Before the flight, the other teams had jokingly voted our group most likely to throw up because we were using both VR headsets and galvanic vestibular stimulators, so we were pretty proud that none of us did,” DePencier Piñero said.

Data Analysis

The team is now combing through the flight data and the results of similar experiments conducted on the ground. They plan to present their analysis at the 2027 NASA Human Research Program Investigators' Workshop in January.

“We’re starting to, very preliminarily, see differences in the outcomes of the spatial orientation measures,” Allred said. “This was only three people. It’s just a case study, but we’re hoping this can snowball into a larger study in the future.”

Allred is principal investigator on the project, with funding support provided by Torin Clark, an associate professor in aerospace whose research focuses on the vestibular system in space contexts. Clark serves as both Austin and DePencier Piñero’s PhD advisor.

The research was conducted during the 8th Swiss Parabolic Flight Campaign, organized by the Center for Space and Aviation Switzerland and Liechtenstein and Swiss SkyLab. CU Boulder’s experiment was one of eight selected projects through a pilot program organized by Swiss SkyLab and Ohio State University, offering research groups shared parabolic flights to reduce costs.