A three-time space shuttle commander uses the Galvanic vestibular stimulation (GVS) system during a space shuttle landing simulation. The GVS delivers small amounts of electricity to the vestibular nerve, which then sends the signals to the brain, resulting in sensorimotor disturbances that are similar to those experienced by astronauts when returning to Earth.
Credit: Human Aerospace Laboratory at the Mount Sinai School of Medicine
A new contraption that artificially induces the dizzying effects of spaceflight in human brains without the pesky need to actually leave Earth is gaining ground as a tool to train new pilots and astronauts. ?
The system was created by a research group led by Steven Moore, an associate professor of neurology at Mount Sinai School of Medicine in New York.
Called the galvanic vestibular stimulation (GVS) system, the tool induces the sensory and mobility disturbances that are typically felt by astronauts when they re-adapt to Earth's gravity following a space mission. It can make people dizzy and feel clumsy with impaired motor control.
"You can train for spaceflight tasks under normal conditions on Earth, but that will not give you an indication of what an astronaut will feel like," said Moore, a member of the Sensorimotor Adaptation Team at the National Science Biomedical Research Institute, a nonprofit science institute located in Houston. "The GVS system will make mission simulations more realistic. This will be quite useful for astronaut training, especially for astronauts that have not flown before."
Spaceflight side effects
side effects include sensory and mobility disturbances that can affect vision
and neurological function, impacting an astronaut's ability to land a
spacecraft during the return to Earth (and its gravity).
And once on the ground, astronauts often have trouble maintaining their balance, and performing basic physical functions, such as walking.?
The GVS system uses electrodes behind the ear to deliver small electric shocks to the vestibular nerve. These signals are sent to the brain ? essentially tricking it into experiencing the side effects from spaceflight such as dizziness or clumsy motor functions.
"We know that GVS is a good model of how microgravity affects astronauts," Moore said. "What we didn't know is how good of an operational analog GVS is for the effects of spaceflight. We now have a validated, ground-based analog for the effects of spaceflight on neurological function that is not just posture, balance and eye movement."
Shuttle landing simulations
Moore tested the system on 12 volunteers in the Vertical Motion Simulator at NASA's Ames Research Center in Moffett Field, Calif. The subjects included a veteran shuttle commander, NASA test pilots and U.S. Air Force pilots.
Each subject flew 16 simulated shuttle landings, with the pilots experiencing the GVS analog during eight of the simulations. The results of the study were compared with data collected from more than 100 real shuttle landings.
Of the real shuttle landings, one out of every five has been outside what is considered the optimal performance range, in terms of touchdown speed and sink rate, Moore said. Pilots using the system landed at slightly faster speeds than those without, similar to the shuttle pilots in the real landings, he explained.
"Without GVS, they were right on the target ? around 204 knots," Moore said. "With GVS, the average speed was pushed up to about 210 knots, which is at the upper limit of the target range."
The test subjects also experienced GVS-induced problems during a routine landing approach braking maneuver, in which the pilots were required to make big changes in the shuttle's glide angle.
During real shuttle landings, this is the point during approach at which pilots typically experience sensory and motor control issues and increased gravitational forces due to acceleration.
"The GVS stimulation of the nerves is making the simulator pilots think the spacecraft is moving around," Moore said. "We are happy with that result. GVS induced similar decrements in simulator landings to those during actual shuttle landings."
So, even though the research used shuttle landings as the test bed, Moore said the GVS is a viable analog for other space vehicles and operations as well, such as landing on Mars.
The researchers also tested 60 separate subjects to determine their tolerance to the GVS stimulation during 15- to 20-minute sessions.
Over 90 percent of those tested had a high tolerance, and the results showed that GVS stimulation impairs cognitive abilities related to spatial processing. Future research will study whether people have the ability to adapt to the use of GVS over multiple sessions.
And while the GVS system could be a useful tool for training astronauts, it could also be used to train aircraft pilots and to prepare people with vestibular disorders for the effects following surgery.
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