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Hank demonstrates how to build a hybrid rocket engine in your kitchen!

Hosted by: Hank Green

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If you’ve ever taken a science class, you’ve probably done some kind of at-home biology, chemistry, or physics experiment. And for good reason — a baking soda volcano is an easy way to get a hands-on look at how the world works.

Plus you get to make a mess—tons of foam, red food coloring… your mom is like, “Why?” But when it comes to understanding space, at-home experiments are a lot harder. After all, space is a giant vacuum, which you can’t exactly recreate in your basement. And even if you could, you shouldn’t.

One thing you can build at home, though, is a rocket. Specifically, a hybrid rocket engine, which many engineers want to use to explore the solar system. All it takes are some basic household supplies and a little caution.

All rockets work by throwing something out the back to propel the rocket forward, and hybrid rockets are no exception. Like what we use in current rockets, they’re a type of chemical engine, and the big ones generate force with a giant, controlled explosion. We’ll do our best to make sure this experiment doesn’t get all explode-y, but we will create a smaller flame.

And like with a full-sized rocket, we’ll make that fire using two basic components: fuel and an oxidizer. The fuel is whatever you’re burning to propel your spacecraft forward, and the oxidizer helps your fuel catch on fire. Like the name suggests, this is often an oxygen-containing compound.

Current rocket engines will sometimes combine these elements in one solid, pre-mixed block — that’s a solid engine. Or, they might use liquid engines, which have separate liquid components that get mixed as they go. Hybrid engines are special because they use a combination of both solid fuel and liquid or gas oxidizer.

Right now, these engines tend to have less thrust than the other models, so they haven’t been used on many missions. A lot of those limitations have to do with how the fuel burns … which is what you’re about to see for yourself. So, we don’t have a lab or a kitchen in this room, but we do on SciShow Kids, so I’m going to go over to the SciShow Kids studio next door for a little bit of rocket science.

For our hybrid rocket, we’re going to use some cylindrical fuel — this is a pasta noodle, it’s rigatoni, it’s got calories in it. You burn it to make yourself. We’re going to burn it to make a rocket.

And for our oxidizer, we’re going to be using pure oxygen gas, which will be created through a reaction between hydrogen peroxide and active yeast. The yeast contains a protein called catalase, which will break down the hydrogen peroxide into water and pure O2 gas. Besides the pasta, hydrogen peroxide, and yeast, you’ll also need a few other basic staples: some safety goggles, a fire extinguisher just in case, and a lighter or a few matches, and a small mason jar with a hole knocked in the lid.

Our jar is about 230 milliliters, or 8 fluid ounces, and the hole in the top is around a third of a centimeter across. The important part is that the noodle should fit over the hole without covering any of the hole up, and without any of the hole escaping from around the noodle. First, lay out all of your supplies ahead of time so you’re ready to go once the reaction starts.

Then, you fill your mason jar about three-quarters of the way with hydrogen peroxide — or about 175 milliliters. Now, here comes the fun part. Add a quarter of a teaspoon of yeast to your jar, and stir.

You should see some bubbles start to form — that’s the pure oxygen. Quickly place the lid on the jar, and place the noodle upright over the hole. Then — get ready for it — light the top of the noodle on fire!

You should see a small column of flame rise up over the noodle as it burns. There is your engine! That’s a pretty good engine!

Oooh! There, it’s going! Oh my gosh.

Now it isn’t producing much force, and any force it is making is directed into the table. So the engine won’t go anywhere, which is probably a good thing in this case given that—ah, large sizable chunk of it is on fire. The reaction’s either going to continue until the noodle is all burned up, or until the chemical reaction with the yeast stops.

We’re going to have to wait until that gets a little less hot. The main limitation with hybrid rocket engines is that they just aren’t very powerful compared to other rocket types. And a lot of that is because of how the fuel burns.

In our demo, the oxidizer flowed through the rigatoni-fuel, and it’s basically the same process in the real thing. How fast the fuel burns — and how much thrust the engine produces — has to do with how much oxidizer is moving through it. If the oxidizer has just one hole to flow through, like with our noodle, it will only burn a little fuel at a time, so it won’t be very powerful.

The big challenge for engineers is figuring out how to shape the fuel so there’s an optimal flow — enough so that it can propel a rocket efficiently, but not so much that it burns through all the fuel all at once, which would just be an explosion. Teams are working on it, though! There’s been more interest in developing hybrid rockets over the last few years.

And another cool thing about this demo, besides the column of fire, is that it kind of illustrates why. One advantage to this type of engine is that it’s hard to accidentally blow up. Not that I’m encouraging you to try.

But since the fuel and oxidizer are stored separately, there’s a much lower risk of accidental explosion compared to a solid engine, where everything is already blended together. In these solid mixtures, the block can sometimes become damaged, which can lead to uneven firing. And hybrid engines are less complicated than many liquid engines, since hybrids only have one fluid component instead of two.

For our rocket, we didn’t have to worry about continuously mixing fluids and hitting the right ratios and flow rates. There were fewer moving parts. In the real world, these benefits translate to engines that could help us launch rockets more safely and more cheaply than we are right now.

We just have to figure out how to give them some extra thrust. Unfortunately, that probably isn’t a problem we can solve with pasta and mason jars, so we’ll have to leave it to the experts. Thanks for watching this episode of SciShow!

If you’d like to keep learning more about space, we have a channel where we unpack all kinds of mysteries about our universe — and the rockets that help us explore it. You can learn more at [♪OUTRO].