Testing Astronaut Health in 30 Seconds of Weightlessness
Inside a giant airplane, researchers wait to make their move as the aircraft climbs steeply at a 45-degree angle. At a precise moment, the aircraft pitches downward, and everyone inside is suddenly suspended in the air, experiencing microgravity. The researchers have less than 30 seconds to collect their measurements before gravity pulls them back down.
Last summer, this sequence repeated 30 times per flight for Rich Whittle, an assistant professor of mechanical and aerospace engineering at the University of California, Davis. He was part of an international team of researchers on the 87th European Space Agency, or ESA, Parabolic Flight Campaign in Bordeaux, France, who observed how microgravity affects blood flow and tested a potential countermeasure to protect astronauts during long-duration spaceflight.
The team’s first findings, recently published in the Journal of Applied Physiology, show that increasing levels of lower-body negative pressure, or LBNP, progressively improved blood flow through the internal jugular vein during microgravity. The researchers also developed a new measure, the Flow Directionality Index, to detect subtle changes in blood flow that existing methods may miss.
Creating Microgravity on Earth
On Earth, gravity naturally keeps much of the body’s blood in the lower parts of the body. In the microgravity environment of space, fluids shift toward the head, which has been linked to several health-related conditions, including abnormal jugular vein blood flow, blood clots and vision problems collectively known as Spaceflight-Associated Neuro-ocular Syndrome, or SANS.
LBNP works by applying gentle suction around the lower body, pulling blood back toward the legs. The technology has long been used on astronauts right before they land on Earth to help them adjust to the gravitational effects on blood flow. But researchers don’t know what level of negative pressure would be most effective during extended space missions.
“When people land, they are at risk of passing out because spaceflight reduces the amount of blood in the body, and when this is pulled down towards the feet by gravity, not enough blood is getting to the head,” Whittle said. “We’re looking at the potential for LBNP as a long-duration countermeasure, but part of that is understanding the dose response. Does 10 millimeters of mercury of LBNP affect different parts of the cardiovascular system? How does 20 or 30 millimeters of mercury affect the blood pressure or heart rate?”
To answer those questions, the researchers needed to recreate the conditions of space. During each parabolic flight, the aircraft repeatedly climbed and descended in a carefully controlled arc, creating between 20 and 30 seconds of weightlessness at a time. The team went on three flights, with 30 parabolas per flight, giving researchers brief windows to collect measurements.
“It’s a totally unreal experience,” Whittle said. “The best way I can describe it is if you’ve been on a roller coaster and you come up on the crest and you come out of your seat for a bit before you fall back down into it. Imagine that feeling, but you don’t come down again for 30 seconds. There’s nothing quite like it.”
A Laboratory in the Sky
To transform the vehicle into a flying laboratory, the team worked with Technavance, a company that specializes in LBNP chambers, to build a device to the aircraft’s exact specifications.
The chamber was fastened to metal plates, which were bolted securely to the aircraft floor and outfitted with equipment to continuously monitor cardiovascular measurements, including blood pressure, heart rate and cardiac output.
The three astronaut participants remained inside the chamber during the flights. The researchers focused on collecting different measurements from the participants for each parabola. Some measured blood flow through the jugular veins using ultrasound, while others measured venous pressure.
The study shows that increasing negative pressure progressively improved jugular blood flow during microgravity, supporting LBNP as a promising countermeasure for future space missions. The findings also provide a foundation for larger studies that could help determine individualized LBNP doses for astronauts during long-duration missions to the Moon and Mars.
The researchers will participate in future flight campaigns to expand the study to more participants, helping Whittle and his team better understand how the human body responds to life beyond Earth.
“We’re trying to find [out] how true microgravity affects us,” he said. “You never know what insights that might open up.”
The research team was led by Professor Ana Diaz Artiles of Texas A&M University and included researchers from Texas A&M University, UC Davis, Universidad Carlos III de Madrid, University of Florida, the Medical College of Wisconsin in Milwaukee, and other international partners. This research was supported by the NASA Human Research Program.
