Florida-based Rocket Crafters Inc. (RCI) has been awarded a patent for a new method of fuelling hybrid liquid or solid rockets using 3D printing technology.
Set to enter service in 2019, RCI claims that the novel process ensures the fabrication of flawless, high-performance, safer-handling fuel grain.
Hybrid rockets are a sort of halfway design between liquid and solid rockets. Instead of incorporating a solid oxidizer in the fuel, a hybrid uses a liquid or gaseous oxidizer that flows through the combustion chamber of a solid rocket motor, which allows the pilot to throttle the motor and even cut it off without having burned all the fuel.
In addition, it doesn’t present the same risk of explosion as liquid rockets or solid monopropellants, like gunpowder, that incorporate their own oxidizers, and is simpler in design with lower operating costs.
Nevertheless, a hybrid’s solid rocket component suffers from the same difficulties as traditional solid fuel rockets. Solid fuels usually consist of a polymer that looks a bit like synthetic rubber that forms an inner chamber in a geometric pattern where combustion takes place, so the fuel is also the motor.
Turning the solid fuel into a rocket motor involves either melting the fuel and pouring it into a mold, or compacting the solid grains either inside or outside the rocket. If the fuel is relatively insensitive, it can also be milled. Whatever the method, making solid rocket motors is time-consuming, dangerous and imprecise, plus conventional methods produce inconsistencies in the motor’s makeup and generate vibrations in flight. Worse, for hybrid motors, the geometric pattern needs to be more complex and precise to produce the desired performance.
The new patent allows for the construction of safer and less expensive launch vehicles that have only two moving parts, and that can deliver small satellites to orbit at half the price of conventional launchers.
It works by using 3D printer technology to precisely place grains of fuel inside the rocket to make up a geometric pattern, which acts as the motor’s combustion chamber. The fuel is laid down grain by grain in a concentric pattern of layers, with a port in the center where the oxidizer is introduced.
As the fuel burns, the precise setting ensures that the shape of the combustion chamber remains constant, and the burning even and predictable as each layer is consumed. To double-ensure consistency, the grains themselves are manufactured by 3D printing before assembly.
RCI states that it is currently developing its Intrepid-1 booster – billed as the world’s first mass-producible orbital launch vehicle using the 3D-printed fuel hybrid engines – scheduled to enter service in 2019.
Image and excerpts from Orbital ATK/RCI