The Real Reason SpaceX Developed The Raptor Engine!

The Starship Super Heavy rocket that Elon Musk and his SpaceX team are creating at Starbase, Texas is set to become the largest and most powerful spacecraft ever built. And we are not just talking about an incremental gain here. The Starship will launch with double the thrust of the previous most powerful rocket, which was the Apollo program's Saturn V moon rocket. But what makes the Starship so powerful? At the heart of the 69 meter tall Super Heavy booster is a very special rocket engine called the Raptor. Actually a lot of them, 33 in total, which is a beyond unprecedented concentration of nozzles. But this isn't just a game of numbers. To pull off a feat like the Starship, we need both quantity and quality. And the Raptor engine brings that in spades. This is an exceptional engine. It pushes the limits of what is physically possible with chemical combustion. And SpaceX accomplishes this by implementing a design that no one before them has been brave enough or crazy enough to even attempt. So today we are going to break down what makes the Raptor engine so special. And we're going to do this in a very simple and casual way that you absolutely do not need to be a rocket scientist to understand. This is just enough to help you get stoked for the Starship launch this summer. And you'll know what's happening when you see that booster light up. And you can use this information to sound like a genius in front of your friends. So let's get going. Let's talk briefly about how a rocket engine works, just so that we're all on the same page. The basic concept here is actually kind of simple. Inside the rocket, there are two propellant tanks. One is for oxygen and the other is for fuel. The oxygen side is the same for every kind of rocket because fire needs oxygen to burn. This is like blowing air into your campfire to intensify the flames. To make oxygen into rocket propellant, you first have to liquefy it. You convert oxygen from a gas to a liquid state simply by super cooling it to a cryogenic temperature. The boiling point of oxygen is negative 183 degrees Celsius or negative 297 Fahrenheit. So at any temperature below that, it will stabilize as a liquid. Pretty cool. Then on the fuel side, this will vary by the rocket. Most use a chemical called RP-1, which is basically just purified kerosene. It's cheap and accessible and is liquid at ambient temperature. RP-1 is a good rocket fuel, but it's also a very dirty fuel. Burning kerosene leaves behind a lot of soot and solid carbon matter as a byproduct, which sticks to the inside of the engine. This is called coking. Now, since most rocket boosters are disposable, this doesn't really matter. But, for a reusable booster like the Falcon 9, this is a big pain in the ass because they have to scrub the Merlin engine clean after every flight. So, since SpaceX plans to rapidly reuse the Starship and booster up to multiple times per day, they don't have time to deal with coking. To solve this, Starship uses methane as its fuel source. This is what we commonly refer to as natural gas, and we know this is a very clean burning fuel because we use it in our furnaces and stovetops without having to worry about scrubbing them out on a daily basis. The same applies to a methane burning rocket engine. You can use it over and over again without maintenance in between. The same as oxygen, methane needs to be converted into a liquid form in order to be used as rocket fuel. So, it also needs to be super cooled to the same cryogenic temperatures. This adds extra complexity to the entire system, having two cryogenic liquids. And that's a big reason why other companies don't do it. The Raptor is the first methane burning rocket engine to launch, and will likely become the first to reach orbit. Okay, so we've got our fuel and our oxygen, now where do we go? Again, the basic concept here is pretty simple, so we'll do an overview and then we'll get into how Raptor takes this to the next level. When the rocket engine starts, two pumps will move both the oxygen and fuel at very high pressure into the combustion chamber, where they are ignited. And that combustion is going to release a massive amount of energy as the propellants burn and expand to create pressure. All of this energy will exit the combustion chamber through the throat. This is like blowing out a candle by pushing air in your lungs out through a small opening in your lips. You create a high pressure inside your mouth by forcing the gas to exit through a small opening. Then, all of that high pressure, high temperature combustion exhaust enters the nozzle, where it expands from the size of the throat to the size of the nozzle opening. This expansion actually accelerates the exhaust to an even faster speed than when it left the throat. The greater the expansion ratio from the throat to the end of the nozzle, the greater the acceleration of the exhaust. This process converts pressure into thrust. The faster we can throw that exhaust gas out the back of the nozzle, the faster the rocket will move forward. Every action has an equal and opposite reaction. The basic concept to keep in mind here is that pressure always flows from high to low. There is high pressure at the throat, and there is low pressure at the tip of the nozzle. Therefore, the exhaust flows in that direction. This is also why the whole rocket doesn't just explode like a bomb. As long as the pressure in the pumps is higher than the pressure in the combustion chamber, then the combusted gas can't flow backwards. I also wanted to give a quick shout out to our amazing discord community. Here is our question of the week, and this was our favorite answer. And here is the meme of the week winner. Join our discord community to participate next week through the link in the description below. The beauty of the Raptor engine is that it takes this process to the absolute limits of what is physically possible by combining an extremely high pressure with an extremely efficient combustion. The design of the Raptor is called a full flow stage combustion cycle. Like we said off the top, this is something that has never been brought to production by any other aerospace company, and that's due to the exceptionally complex system design. Again, we're going to keep this as simple as possible while still getting the main point across. Not rocket science, just enough to understand what's going on in there. So to visualize what's going on inside a Raptor, we need to add one more component to the path that our propellants take from the tank to the combustion chamber. In the Raptor cycle, the liquids are pumped out of the tanks and then directly into a pair of gas turbines. Both the fuel and the oxygen hit individual turbines. Many rocket engines will use a single turbine either on the oxygen side or, in rare cases, the fuel side, but Raptor is the only engine with dual gas turbines. When the cryogenic liquid reaches these turbines, the first thing it will encounter is a pre-burner. This is like a miniature rocket engine in itself that combusts the liquid just enough to transform it into a gas. But since neither of these liquids can combust on their own, there needs to be a cross connection between the two pre-burners that allows a little bit of oxygen to join the methane flow, and a little bit of methane to join the oxygen flow. This combustion converts the liquid to gas and that gas is then blasted into the turbine housing where it spins the blade. The turbine blade spins the pump and that blasts out now gaseous propellants into the combustion chamber at extreme pressure. Now hold up a second. If the turbine spins the pump and the pump sends the liquid into the turbine, then how does the process get started in the first place? SpaceX uses equipment on the launch mount to externally spin start the turbines. This is what they were testing when the booster exploded at Starbase in mid-June. Too much methane came out when they spun the turbines and it pooled underneath the rocket and ignited off a nearby generator. So now we have both our oxygen and methane exiting the turbines as very hot and very high pressure gases. And that gas on gas reaction when they hit the combustion chamber is going to produce the most efficient combustion possible. Significantly more energy is going to generate by gas on gas than by liquid on liquid. Elon Musk says that this reaction is 99% efficient, the maximum that physics will allow. Elon says that only God himself could possibly do a better job at combining molecules than the Raptor combustion chamber. And this is part of the reason that SpaceX had to develop this new Raptor V2 engine. Elon also has revealed that with the latest Raptor version 2, there is no need to even have an igniter in the combustion chamber. The gases will self-combust. He wouldn't explain the details of how that happens, but he did say that removing the igniter system allows for a significant reduction in complexity, which in turn makes the engine cheaper to build and lighter overall. Now if that all sounded very complicated, that's because it is. Elon has referred to igniting the Raptor engine as a delicate dance between the fuel system and the oxygen system. Everything is interconnected and everything affects everything else. So if anything goes wrong, the whole engine will explode, or at the very least parts will melt. Elon says that SpaceX has blown up at least 20, if not 30 Raptor engines already during the course of their testing. He says they've melted at least 50 combustion chambers. But that's okay, because SpaceX has built their infrastructure to allow an extremely high production rate for the Raptor, about 1 engine per day. The higher the production rate, the faster you can iterate, or change the design. Faster production allows for many iterations on the Raptor design, and it doesn't really matter if you blow some up in the process because a new one is already on the way. So we know how the Raptor does what it does. Let's talk about what that all means for the performance and the power of this engine. The Raptor is a small engine that produces a massive amount of thrust. The current Raptor version 2 is creating 230 metric tons of thrust at sea level. This is not the most powerful rocket engine, that title goes to the F1 engine that lifted the Saturn V rocket. It had more than twice the thrust of a Raptor, but it was also an absolutely humongous engine that you could park a jeep inside of. The Raptor is a super compact 3 meters tall and 1.5 meters wide at the nozzle. This allows SpaceX to pack 33 of them into the 9 meter diameter booster. Raptor is much smaller than the RS-25 engines that powered the space shuttle, and have also been adapted to the SLS moon rocket. But the RS-25 produces about 190 metric tons of thrust, so Raptor punches well above its weight in terms of brute force. The Raptor 2 weighs in at just 1600 kilograms, while the RS-25 is nearly 3200. And it accomplishes this by running the combustion chamber at significantly higher pressure than any other rocket engine in the world. The Raptor 2 chamber pressure is currently 300 bar, which converts to about 4351 pounds per square inch. The RS-25 chamber pressure is down at about 206 bar. Remember that the rocket engine uses the throat and nozzle to convert pressure into thrust, so more pressure means more thrust. Elon Musk says that SpaceX likely still has some room for improvement with the Raptor 2 design, and could reach a maximum of 250 tons of thrust at some point in the near future. Elon says that they are still losing some performance by overcooling the engine. Right now, they are optimizing for the overall robustness of the engine, as opposed to performance, because first they want to get to orbit without exploding, and then they might get a little more brave after that. We didn't even touch on how rocket engines are cooled. Obviously, they need a very complex cooling system to prevent the whole thing from melting down, but that's just too much information for one day, so just know that there is a system in place to maintain the temperature. Now Elon Musk says that the work going forward on the Raptor design will be primarily to make the engine more simplified, and therefore cheaper, and faster to produce. This comes back to one of Elon's favorite sayings, the best part is no part, which is at the core of his first principles philosophy. The steps that Elon follows when he's designing something are to first question the constraints and requirements, and make them less dumb, aka don't follow any rule that doesn't make sense. Then second, delete any part of the design process that isn't necessary. If you aren't forced to put back at least 10% of the things that you deleted, then you didn't delete enough things. Step three, optimize. Step four, accelerate. And step five, automate. And we can already see that in action with the transition from Raptor 1 to Raptor 2. There are significantly fewer parts visible on the new engine. Elon says that he wants to delete all of the fiddly bits from the engine. That means integrating more of the small pipes, and wiring into larger conduits, and replacing bolted flanges with solid welds. Elon says that by integrating more components of the engine, they can actually remove the shrouds, which are essentially protective heat shields. Obviously removing anything from a rocket ship design is going to make it lighter and cheaper, which is absolutely critical for sustainable space flight. This process will also continue to make Raptor cheaper and more production friendly, which again is the ultimate main goal. You may wonder, why do you need so many engines if the rocket is going to be fully reusable? Well, we've got to think longer term here. That's where Elon's head is at. His end goal with Starship is to make these rockets as common as jet airliners are today. A fleet numbering at least 1,000 ships or more. These ships would be in constant operation for transit between the Earth and Mars, the Earth and the Moon, or even using the ship as a point to point transport on the Earth itself. The end game of the Starship is to become one of the most important vehicles ever created in human history. This is right up there with the first sailing ships that crossed the ocean and connected the globe. The Starship can connect the solar system. And that is a pretty damn cool thing to be able to watch play out in real time. So shout out to Elon Musk for being chill and sharing all of this information with us and letting everyone follow along on the journey. Hopefully you learned something today about rockets and at least have a better understanding about why the Starship and the Raptor engine in particular is such a unique invention. Let us know what you think in the comments section below. Don't forget to give this video a thumbs up today if you liked it. That is so important for getting our content out to more people. If you enjoy the content then you'd probably also enjoy our weekly newsletter. So sign up with the link down below at theteslaspace.com. A huge thank you to all of our Patreon supporters who are listed on the screen now. You help us make the best content we can and we really appreciate it. Thanks for watching and we'll see you in the next one.