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The toolkit of the average NASA engineer of the 1960’s contained mostly standard equipment: screwdrivers, pliers, welding torches, and...broomsticks? Yeah, turns out those engineers weren’t helping out the janitorial staff. Brooms played a vital role in keeping everyone safe from fuel leaks and dangerous explosions, and it all comes back to the most basic atom there is: Hydrogen. [♪ INTRO] In the 1930s, passenger airships were a popular, exciting way to see the world.

Commercial zeppelins, held buoyant in the sky by hydrogen or helium gas, had been ferrying passengers between continents for decades. But on May 6th, 1937, all of that came to an end. On that day, a passenger airship was carrying 97 people from Frankfurt, Germany, to Lakehurst, New Jersey, in the US.

You may have heard of this ship; it was called the Hindenburg. When the ship began its descent, it caught fire and was fully ablaze within minutes. 36 people lost their lives: 13 passengers and 23 of the Hindenburg’s crew, one of whom was on the ground. Now, chances are that if you’ve heard about the Hindenburg, you might also know the reason for its tragic end.

Experts at the time, and in the decades since, have agreed that the fire most likely started when the airship’s hydrogen gas system developed a leak, and a wayward spark ignited the ball of flammable gas This is the most infamous disaster involving hydrogen gas in history, and it basically ended the entire passenger airship industry in just a few short minutes. The role that hydrogen gas played in the Hindenburg disaster also demonstrates two things that we know about hydrogen. It’s incredibly dangerous, and it has immense potential as a fuel source, since the main thing that fuel has to do is burn.

But it’s hard to overstate just how dangerous hydrogen fuel is, which is why we aren’t filling up our gas tanks with the stuff. First of all, hydrogen atoms are small. A hydrogen atom is the smallest and simplest arrangement of matter that exists in our universe.

That means it’s really hard to prevent leaks. Even the tiniest crack in a fuel cell, or the smallest flaw in a container, can allow hydrogen molecules to escape. And it only takes one spark to light up a cloud of hydrogen gas and cause a massive disaster in just seconds, like with the Hindenburg.

Even just being under too much pressure can make hydrogen gas spontaneously burst into flames. But the most dangerous thing about hydrogen fire is that it’s basically invisible. Hydrogen gas is colorless and odorless, which means that it’s extremely difficult to detect a gas leak.

And hydrogen flames don’t burn very brightly, so a hydrogen fire can be hard to see in a well-lit environment. Until the fire ignites something else, that is. And since hydrogen burns at about 2,180 degrees Celsius, that’s basically inevitable.

But the benefits of using hydrogen fuel are incredibly tempting, once you get past the whole invisible flames thing. For starters, it’s clean and efficient, which makes it a big step up from the coal and natural gas that currently power most of our world. When hydrogen fuel is burned, it produces much smaller amounts of carbon-based gasses, which have the biggest impact on the greenhouse effect.

Hydrogen’s fuel byproducts can be prevented from entering the atmosphere more easily, and it can even be used in self-contained fuel cells, where the only byproduct left behind is water. So that means that harnessing hydrogen fuel sources could be crucial in the fight against climate change. And we do use hydrogen fuel in a few places.

Hydrogen is super lightweight and powerful, so it’s perfect for fueling rocketships. Every pound matters when you consider how to launch something outside of Earth’s atmosphere, so hydrogen fuel gives us the most bang for our buck. Which is why NASA has used liquid hydrogen to power its launches for decades.

And that means they have a lot of experience with managing the dangers of dealing with that much invisible fuel. In order to get that hydrogen from its storage tanks to the launchpad, it has to go through miles of pipes. And that’s a lot of opportunities for leaks.

Which brings us, finally, back to the broomsticks. Back in the 1960s and '70s, when NASA was working on the Apollo missions, liquid hydrogen fuel was new. They didn’t have much experience with it, and leaks were a constant fear, since a hydrogen fire can derail launches and endanger lives.

So how did they hunt for invisible flames? Well, the solution that NASA came up with was for their workers to walk around holding broomsticks out in front of them, since if the bristles touched an invisible hydrogen fire, they’d burn too, just, you know, visibly. Since they had no other way to detect hydrogen fires, this was the best solution they had to manage the risk.

Obviously, this wasn’t ideal. For starters, you probably want to catch a dangerous fuel leak before it turns into an invisible flaming ball of doom. And fortunately for everyone, we’ve gotten a lot better at detecting hydrogen leaks over the years.

For example, in the 1970s and early '80’s, NASA developed a simple hydrogen detector, similar to the carbon monoxide detectors used in lots of homes and buildings. Whenever the sensors inside the device detected hydrogen gas, an alarm would go off, letting workers know that there was a leak before a fire started. But because the detector was just an alarm, it couldn’t pinpoint the exact location of a leak.

It still took a long time to actually find the flaw in the piping that allowed hydrogen to escape, which could delay launches and cause setbacks. In 2003, researchers started to develop a more convenient way to detect the presence of leaking hydrogen. They wanted to come up with something that’d be a visual indicator to pinpoint the exact place where a leak started.

It took a few years to figure out the details, but in the end they came up with what’s called a chemochromic tape, meaning a tape that changes color in response to a chemical substance, in this case hydrogen. And getting it just right was harder than you’d think! The change in colors has to be visible to the human eye, so no changing from blue to like, slightly lighter blue.

The change in colors also needed to happen fast, in order to catch a leak before it could ignite. And, if this tape was going to be useful in rocket launches, it needed to be weather-resistant and fire-resistant. They finally deployed what’s probably the most extensively researched tape in all of human history in 2007, during the launch of the Space Shuttle Endeavour’s STS-118 mission to the International Space Station.

It worked exactly as the scientists had hoped, and was applied to welded seams, along pipelines, and to fuel cells. It’s been used on all following launches of the Endeavor, and the technology has been adapted for use in rocket launches ever since. And NASA’s decades of research into making hydrogen fuel safer hasn’t only been good for space travel.

Their inventions have made it possible to store and use hydrogen gas in industrial environments like oil refineries and chemical plants. The hope is that with more time and more safety innovations like chemochromic tape, we can make hydrogen fuel safe enough to use for powering our homes, cars, and other aspects of our daily lives. Which would be awesome for the planet, and for us!

And we may never have been able to explore the upsides of hydrogen fuel if not for all those NASA employees wandering around wielding brooms. So, thanks, guys. Hope you didn’t feel too silly doing that.

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Thanks to Linode for supporting this SciShow video and thank you for watching! [♪ OUTRO]