What really is a “single piece” rocket engine & why we make these at Agnikul? (part 1/n)
Let’s start with some basics. What is a rocket engine? In its simplest form, a rocket engine is a device that is capable of burning gases and sending them out at extremely high velocities. By Newton’s laws, gases going out of a rocket engine’s nozzle will exert an equal and opposite force on the rocket itself, thereby pushing the rocket in the other direction.
So, what are the components within a rocket engine that allow for this combustion to happen? To answer this question — we will first talk about what is really getting combusted in a rocket engine. It could be propellants stored in liquid form, gaseous form or a solid form. At least as far as Agnikul goes, we have realized semi-cryogenic liquid propulsion engines (‘Agnilet’ is the name) — so we will stick to liquid propellants, for now.
Injectors: Oxygen and fuel coming into a rocket engine have to efficiently mix to ensure uniform combustion. Then, this mixture has to become a spray of fine droplets, so that the fuel fully burns. This is achieved by what are called injectors. More on this upcoming blogs. These are extremely complex geometries that usually take 100’s of machining processes such as welding, drilling etc. to make precisely.
Injector plate: This is where all these injectors are assembled. This is painstaking work, if done manually.
Manifolds: Think of these as distribution channels. Fuel and oxygen have to be given to each of these injectors in a uniform manner. This is difficult stuff because the level of uniformity and precision expected is of the order of 0.1% of the mass coming in.
Combustion Chamber: This is where the actual burning happens.
Nozzle: This is where the gases are accelerated as they leave the engine. The faster the exit speed of the gases, the better the thrust (at least roughly speaking).
Cooling channels: This is where life gets tricky. The burning gases end up making the rocket engine extremely hot. So, need to cool the engine. Someone, very early on figured that the liquid fuel itself can be used to cool the engine — just circulate it around the engine and bring it in. There are 100s of cooling channels in a rocket engine and each one of them has to be carefully crafted.
When you make all of this in one shot and as a single component (as opposed to putting together 1000’s of components through conventional fabrication techniques such as welding, brazing etc.) — we have a single piece rocket engine!
How to realize such an engine? Why do this at all? More will follow in the coming days…
