Nishanth Surianarayanan received a NASA grant to develop fluid mechanics models of cerebrospinal fluid flow, which behaves uniquely during long durations in microgravity. (Purdue University photo/Jared Pike)

“NASA conducts many detailed studies on the health of their astronauts,” said Nishanth Surianarayanan, a Ph.D. student in mechanical engineering. “But this issue is a relatively recent discovery.”

The issue involves the glymphatic system, a biological process which was first confirmed in living humans in October 2024. Cerebrospinal fluid, the material that comes out during a spinal tap, typically circulates through the brain and spinal cord. It flows around the brain’s blood vessels in annular gaps known as perivascular space, and serves a similar function to blood — bringing vital materials in, and removing metabolic waste products.

“But during long periods of microgravity, that outflow is reduced,” Surianarayanan said. “The fluid flows into the brain, but it doesn’t flow out to remove waste products. As a result, those waste products linger.”

The exact neurological effects of this are not fully understood, but similar blockages have been observed in non-astronaut patients with conditions like dementia or multiple sclerosis. So this reduced fluid cycling during long periods of microgravity has the potential to cause negative effects on astronauts’ brain health.

As such, NASA wants to know what durations of microgravity tend to cause this, and what mitigations might be available to reduce the risk. That’s why they have turned to Purdue University fluid mechanics researchers to better understand this cerebrospinal fluid flow.

NASA have awarded Surianarayanan a Future Investigators in NASA Earth and Space Science and Technology (FINESST) award, designed to support graduate students as “future investigators” to tackle space-related issues in various scientific fields. Among the total of 1,120 proposals submitted last year, Surianarayanan’s was one of four selected to address the category of Biological and Physical Sciences. He will receive $50,000 a year over the next two years.

“My first goal is to build a fundamental model of how this cerebrospinal fluid flows in the brain,” Surianarayanan said. “This will be a challenge because that fluid is not only interacting with the soft tissue of the brain, but also with the arterial pulsations caused by the heart. My second goal will be to model the effects of spaceflight — how long periods of microgravity affect this flow over time.”

Surianarayanan’s faculty advisor at Purdue is Ivan Christov, associate professor of mechanical engineering. Christov is an expert in modeling complex fluid flows, especially in biological systems. He helped to establish a new theory for flow in blood vessels, and applied it to understanding how brain aneurysms grow.

While most of Surianarayanan’s work will be modeling and simulation, he has real-world data from NASA studies and other sources to draw from. “I’ve always been interested in biology,” he said, “so to be able to apply mechanical engineering principles to study something biological is really a dream for me. It’s my hope that NASA can use these models to protect their astronauts in the future.”

Source: Nishanth Surianarayanan, nsuriana@purdue.edu; Ivan Christov, christov@purdue.edu

Writer: Jared Pike, jaredpike@purdue.edu, 765-496-0374