We're weightless, about 34,000 feet above the Gulf of Mexico, trying not to vomit from motion sickness while wiggling an ultrasound probe into the esophagus of a $26,000 mannequin. In a moment, the hollowed-out Boeing 727 will reach the top of its parabola and plunge 10,000 feet, nose down—there's just enough time before the dive for the three college students conducting this microgravity experiment to snap a few grainy ultrasound images of the mannequin's lifeless heart.
Behind us, a black backpack drifts toward the ceiling. The airplane's seat belts bob up and down, up and down, as though they were underwater. A NASA photographer lets go of his camera, and it hovers in front of his face.
I'm floating a couple of inches above the floor in a seated position (and feeling very much like a genie) when a crew member shouts over the engine noise that we're about to go from weightlessness to two times the force of gravity. The warning is crucial, because you don't want to be upside down when gravity kicks back in. This is also the part of a parabolic flight when most people barf.
Seconds later, I'm flat on my back on the padded floor of the plane as it barrels down to 24,000 feet. The Stanford University students trade seats around the limbless mannequin and strap down their legs, so that when the plane enters its next zero-G parabola, no one floats away from the bolted-down experiment setup. At the front of the plane, a student from another team vomits into a bag.
***This flight is part of NASA's competitive Microgravity University program. High school and college students submit proposals for reduced-gravity experiments; the winning teams come to Houston's Ellington Field for a week that culminates in a parabolic flight.
I'm on the plane to cover Stanford's experiment, which will test whether a portable ultrasound machine takes useful images of the heart in microgravity. The bigger picture concerns the future of human spaceflight: Will our medical devices keep us alive when we're millions of miles from Earth?
In microgravity, Newton's law of equal and opposite reactions is especially salient.
The Stanford team leader is 18-year-old Paul Warren, a freshman computer science student who, as a 16-year-old, designed a biology experiment that flew to the International Space Station. When I first spoke with Warren by phone, his enthusiasm for the future of manned space travel overrode some of my terror at the prospect of the flight. "I believe humans will never be satisfied until we've explored everything and learned everything," he said. "But before we make long-duration spaceflight a reality, we need to have the type of medical equipment in emergency rooms on Earth available in space." The morning I meet him at NASA's Hangar 990 in Houston, he's wearing a SpaceX t-shirt and confidently directing the five other members of the team, most of whom are older than him.
Currently, humans in space have limited options when it comes to medical monitoring and treatments—surgery, for example, is not yet possible. But if there is a medical emergency aboard the International Space Station, the astronauts are only hours away from hospitals on Earth. A manned mission to Mars, however, would put humans in deep space for months or years at a time, which means crew members would need to be prepared to deal with emergencies on their own.
The ultrasound machine the students are testing would be well suited for space missions. It is light and compact, requires very little medical training to use, and the probe can stay in the body for 72 hours at a time. But the technology has only ever been used on Earth, and no one knows whether it would function correctly in zero gravity. The most significant concern is that microgravity will cause the probe to drift out of position.
The team's mentor, cardiac surgeon and space medicine specialist Peter Lee, tells me that an ultrasound probe that sits in the esophagus is an ideal diagnostic tool for extended spaceflights. "If an astronaut far from Earth were to have a cardiovascular event, or for some reason became incapacitated and had to be on a ventilator, there's no imaging currently available [in space] that provides continuous images of the heart," he says. "You can use [external] ultrasound, but the technician has to be there the whole time to hold it on the chest."
The day before our flight, the students are practicing using the ultrasound probe on the mannequin, which is covered in lifelike skin and contains anatomically correct models of internal organs. They snake the flexible probe through the mouth and down the esophagus, where it can capture clearer images of the heart than an external ultrasound could. The probe connects to a black-and-white monitor that displays real-time ultrasound views of the heart. The images reveal if the heart is beating; whether the valves are working properly; where there is fluid around the heart; and if too much blood is flowing in and out.
***The NASA program directors warned us to get plenty of sleep the night before the flight. "Don't drink any alcohol. And try not to eat heavy food." Still, we're all a bit loopy from the scopolamine* injections we received before takeoff. The anti-nausea drug has made my mouth and eyes painfully dry, and my sense of hearing feels dulled.
You'd think the first thing you notice when gravity disappears is that you're floating toward the ceiling. Actually, the first thing you notice is that your brain, struggling with new and strange signals from your inner ear, stops registering the ceiling as being above you. My first thought is that I have somehow flipped upside down. In fact, I’ve hardly moved at all from a few moments before, back when my body had weight. As I begin to lift off the floor, I panic and grab a nearby seat. In front of me, Warren is somersaulting in midair.
Of course, gravity hasn't really switched off; we're still very much in Earth's pull. In the 1950s, aviation scientists discovered they could simulate zero gravity by flying in parabolic arcs. When a plane flies upward at an angle of 45 degrees, its passengers experience hypergravity—commonly about 2 G's—as the force of the climb combines with the pull of Earth's gravity. When the plane starts to bring its nose down, everyone and everything not bolted down inside continues moving up, floating to the middle of the cabin.
Weightlessness lasts about 20 seconds, and then it’s back to double gravity as the plane completes the arc and begins speeding toward Earth, nose first. I feared that this portion of the flight would feel like a two-mile roller coaster drop. Instead, lying on the floor, I feel mostly that I have become very heavy. In hypergravity, even lifting your arms is difficult.
To get the data they need for their experiment, Warren and teammates Sam Beder, 23, and Andy Vu, 18, must take six images of the heart per weightless parabola. At first, they struggle to keep still long enough to operate the probe; in microgravity, Newton's law of equal and opposite reactions is especially salient. The smallest movement of your right hand will propel your whole body to the left. At one point, I shifted my feet and found myself doing a backflip.
Thirty-two parabolas and a little over an hour later, the 727 is headed back toward Ellington Field, and we're buckling into the seats at the back of the cabin. A NASA crew member told us that many flyers fall asleep during the brief return flight; scopolamine is a sedative. By the time we land, though, we're all still awake, grinning, and comparing stories. The barf bags in our pockets are mercifully empty.
The next day, the rest of the team—Diniana Piekutowski, 19, David Gerson, 22, and Lisa Lee, 21—take the mannequin up for another parabolic flight. Piekutowski, unluckily, is the only team member to get sick. "I threw up four times," she says. "They just kept handing me bags." (I hear there is GoPro footage of this, but repeated requests for the video are denied with much hand-waving and laughter.)
After the flight, Warren sends the sets of ultrasound images—ones taken on the ground as well as those captured in microgravity—to a cardiac anesthesiologist, who will rate the quality of each picture. If the doctor judges both sets similarly, it will be a first step toward determining whether the ultrasound probe could someday monitor astronauts in space.
***In early June, two months after the flight, Warren has results to report: The cardiac anesthesiologist saw no significant differences between the images of the heart taken on the ground and those taken in zero-G. Warren plans to send the images to more doctors for review. The team hopes eventually to publish their results.
"One day in the future, someone is going to need surgery in zero gravity," Warren told me before the flight. "How are we going to do it?"
Tips To Beat Motion Sickness During A Zero-G Flight
- Avoid caffeine the day of
- Two hours before takeoff, eat a small meal of bread, rice, or another easy-to-digest food
- Keep your chin up
- Don't close your eyes
- Don't turn your head separately from the rest of your body (pretend you're wearing a neck brace)
- Keep your feet below your head
- Avoid rapid eye movements
- Lie on your back during hypergravity
- Don't look out the window—the sight of the slanted horizon will confuse your brain even more
*yes, that scopolamine
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