What do astronaut training facilities  and carnivals have in common?

People walking around in weird  suits, yes. But also, centrifuges.

You hop in, get spun right round like a record, and feel like another human  is sitting on your chest. Maybe you get a little nauseated. Maybe you step out when  it’s all over and fall over because your sense of balance got all messed up.

But the centrifuges astronauts get to ride are way more intense than anything you’ll find between a rollercoaster and an overpriced snack stand. And we’re here to talk about the most notorious. It was called the Johnsville Centrifuge, and it gave early NASA astronauts  the ride of their lives.

Because for half a century, this thing was the most powerful  centrifuge in the world. [intro jingle] Centrifuge rides are just one part of your standard astronaut training regimen. And NASA has used them basically from the get-go. Even in the early years at NASA, scientists were beginning  to understand the effects that extreme accelerations had on the human body.

Now to drop a bit of jargon on you, those accelerations are often  referred to by the term G-forces. Because from your own internal reference point, accelerating can appear to have the same effect as the force of gravity. 1g represents an acceleration equal to what you experience just walking around on the surface of the Earth due to the pull of gravity. 9.8 meters per second squared. So for any higher number of gs, you feel like you weigh more than you normally do.

For example, during a space shuttle launch, astronauts were subjected to a maximum of 3gs. So at some point along their journey into orbit, a 60 kilogram astronaut would feel like they weighed 180 kilograms. Meanwhile, a driver at the Texas Motor Speedway can experience as much as 5gs on the turns.

And a roller coaster that really whips you around can top out at around 6gs for very brief periods. That’s similar to what NASA's astronauts in the Mercury and Gemini programs experienced getting into Earth orbit. It’s also similar to what astronauts are expected to experience while landing in a Russian Soyuz spacecraft.

But there was one time, in 2008, where the occupants were subject to over 8gs. One astronaut said she experienced severe trouble breathing during that time, and another was hospitalized for excruciating neck and back pain. And I know what you’re thinking. “I’m not an astronaut…yet.

What can I handle?” Well, “you”, under normal situations the average human can survive about 12gs for very brief amounts of time. And during that time, you feel like you have 11 other yous sitting on your chest. Which, safe to say, isn’t  particularly pleasurable.

But a sustained high-g situation is pretty hard on any body, even one belonging to an  astronaut in tip-top shape. Or should I say, a military test pilot in tip-top shape. Because the Johnsville centrifuge wasn’t built to train astronauts.

Picture it. It’s the 1940s, and the US military realized t probably shouldn’t launch its pilots in a bunch of new-fangled super fast planes without some ground-based testing, first. And thus, in 1947, construction started on a training centrifuge at the Johnsville Naval Air Development Center in Warminster, Pennsylvania.

And by the time NASA had picked a bunch of military test pilots for its first astronaut class, it had a giant centrifuge to stick them into. Not all at once, of course. Though I suppose you could try shoving the whole of Mercury 7 if you really wanted to… Depending on the era, the centrifuge’s gondola was either a 3 meter-by-2 meter spheroid, or a proper 3-meter wide sphere.

And it was stuck on the end of a 15-meter arm, powered by a 4,000-horsepower electric engine. Thanks to all that HP, the centrifuge could whip its rider up to a maximum 40gs in as little as 7 seconds, just in case that was ever gonna be necessary. Spoiler alert: It wasn't.

And for decades, the pilots and astronauts that got their g-force training inside this thing also served as guinea pigs. For the record, this was before Congress passed legislation that regulated human experimentation, although they tested on animals, too. And sadly, several live monkeys, chimpanzees, and even dogs met their end from the extreme accelerations they faced in the Johnsville centrifuge.

But no humans were ever seriously hurt there, despite one of the potential side effects being spontaneous death because your heart is trying so hard to get blood to the rest of your body, it just gives out. Meanwhile, less permanent side effects include temporary loss of vision, and a phenomenon called G-LOC where you black out because blood can't reach your brain. You can also get a measles-like rash as blood leaks through the  capillaries in your skin.

And of course, there’s the standard struggle to breathe. Because after you exhale and your lungs lose all that air, the rest of your chest crumples in around them and you can't inhale again. But all that guinea-piggery led to scientists figuring out the right breathing techniques  and preparatory measures that protect people.

Including the pressurized g-suit, which both helps you breathe and keeps most of your blood where it needs to be. So we owe a lot to the pilots and astronauts that subjected themselves to what Time Magazine once described as a “torture chamber”. But they aren’t the only ones who went for some extreme rides.

Because no matter what field of science you’re dealing with, you’re gonna find a scientist who wants to be a guinea pig, too. Take, for instance, the “Iron  Maiden” experiment from 1958, designed by civilian psychologist, R. Flanagan Gray.

He had noticed that fish don’t seem to be affected by accelerations, so he hypothesized that if you could submerge a human in a bunch of water, they’d better withstand the  stresses of a high-g situation. So Dr. Gray built a roughly human-shaped aluminum capsule, stuck it onto the centrifuge’s arm, filled it with water, got inside, and cranked up the centrifuge basically as high as it would go.

After about 25 seconds, he hit just over 31 gs. And he stayed there for 5 whole seconds. It’s a record that stands to this very day.

Now, reports vary on exactly what physical side  effects Gray experienced, but he was basically fine. The actual paper that got published referred to a “slight frontal sinus pain” during the run and “a few flecks of blood in his handkerchief the following morning”. He also reported abdominal pain once the centrifuge hit 10gs that he could manage by tightening the appropriate muscles.

But while Gray was going for max gs, another researcher was going for max time. His name was Carl Clark. He was a medical zoologist by training, and he wanted to test what would happen if you just hung out in higher-than-normal Gs for super extended periods of time.

Why would humans want to do that? Well, instead of coasting at a constant velocity to the Moon or Mars, astronauts could get there a bit faster if they kept their foot on  the proverbial accelerator. So, Clark brought his La-Z-boy recliner from home, and hung out inside the  Johnsville centrifuge gondola at a cool 2gs for a full 24 hours.

He reportedly cooked, ate, napped, made medical observations on himself, wrote, listened to the radio, and generally carried out  activities of daily life. And the only real symptom he  noted was a feeling of fatigue. Which if you ask me, is probably a combination of feeling twice his natural weight the whole time, and being stuck inside a gondola with nothing important to do.

After the Apollo program, NASA eventually started training astronauts in centrifuges a bit closer to home, like the Brooks centrifuge in San Antonio, Texas. It's capable of accelerating you up to 30gs, but your average astronaut  will only experience 8 max, while training for an emergency reentry. Meanwhile, the Navy abandoned its Johnsville facility in 1996.

The centrifuge itself was decommissioned in 2004. But parts of it are still there, and you can do more than just visit them. You can rent the building for parties!

So if you live in the greater Philly area, consider having your prom, wedding, or bat mitzvah at what was once hailed as the world's most powerful centrifuge! But if you don’t have that kind of money, you can get your hands on a shrunken down version of the Johnsville centrifuge from our merch store. It even spins!

That’s hours of entertainment, right there! This limited edition pin  is available for order now, so get yours by heading  over to DFTBA.com/ SciShow. Thanks for watching! [ OUTRO MUSIC ]