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Rockets are among the most powerful machines ever designed. Their job is essentially to collect millions of gallons of explosive fluid and control the reaction so as to allow a very small piece of steel and circuitry to travel beyond. It's a marvel, of course. And these monsters operate almost every week somewhere on the Earth – often lobbing tiny satellites or other projects in orbit around our planet.
Of course, at the other end of the spectrum, is the current king of the private rocket – SpaceX. Its Falcon Heavy rocket, launched for the first time this year, holds the record for the most powerful operational launch system. Despite this, the American start-up has its eyes on the horizon and plans its next vehicle, the Big Falcon Rocket.
This mastodon will work on the already tested Raptor engine. And in addition to being one of the most advanced engines ever developed (we'll talk about it later), it will use methane instead of purified jet fuel called RP-1, used by most modern rockets. . Rocket fuels have two distinct components: fuel and oxidant. The latter is almost always liquid oxygen for the first stages of the liquid fuel rocket (RCS thrusters, upper floors, and boosters use other mechanismsBut the fuel itself can be just about anything that is powerful and responsive to oxygen. Hydrogen, kerosene, ethanol are just some of the most popular choices. The fuel used by these machines may not seem particularly important – after all, if they have enough fuel punchwhat does it do, yes? Except that it does not work at all.
Photo credit: SpaceX
The type of fuel essentially determines everything that concerns the rocket. Questions such as: What is the size of the tanks (and therefore the size of the rocket)? What temperatures does the rocket engine have to withstand? How are you going to pump tens of thousands of gallons of stuff per second? All of these things depend on the fuel.
And they cover the whole gamut of hypergolic hyper-toxic fuels of Russian rocket Proton all the way to the Spaceship, which emits clean water vapor as an exhaust.
Methane is a type of intermediate fuel. This is not good for the environment because it is one of the most powerful greenhouse gases, but it burns cleanly and retains enough energy, which means you can pack it in tanks smaller ones. The clean burning bit is actually a huge deal, however. SpaceX wants these engines to turn on and off repeatedly, and accumulating soot and other compounds common to engines driven by the RP-1 will not pose the same problem. This is especially true when turbopumps supplying the fuel required by the main engines are taken into account.
In many rockets, these pumps are driven by smaller versions of the main engine. The problem is that it takes so much fuel that one of the most efficient ways to power the engines is to produce smaller versions that work a little differently. Because they are designed to drive pumps instead of rocket ringtones, the fuel / oxidizer ratio gets a boost, thus reducing reaction efficiency, but also producing a crapload of energy that is a bit more docile than the one you will get from the metric. current engines.
RS-25 Engine Test (Photo Credit: NASA)
Now, if you start to exhaust yourself a bit, you start to get an idea of what makes rocket science so difficult. Even the simplest ones require a little background. However, by gathering all these ideas, we can see what makes the Raptor so special – and understand why methane is ideal for SpaceX's upcoming missions.
The liquid methane and oxygen of the Raptor each feed a turbopump driven by a smaller version of the main engine. The methane tank gets a mixture rich in oxidant, oxygen a mixture rich in methane. The exhaust gases of the two – which contain respectively additional LOX and methane – combine in the primary combustion chamber. This even allows you to use the leftover pumps (which are often unnecessarily discharged from the rocket with other engines) as extra power.
This can only work because methane burns so cleanly. Because SpaceX intends to light rockets, reuse them, re-fire them again and again with relatively little maintenance, turbo pump systems are extremely critical. And they are the most vulnerable to soot formation.
Methane, some say, is the fuel of the future. The next wave of rockets will have to be reusable to reduce costs. Alongside this, we look for efficient motors that can be used again and again with a minimum of maintenance. It is a difficult bill to respect and only suitable for methane.
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