The Edinburgh-based operation, Skyrora, has been developing what they call an “eco rocket” for several years based on a 3D printed rocket engine. It’s “eco” because its design produces far less greenhouse gas than conventional rocket mixtures.
The key to their chemistry seems to be the use of a kerosene fuel that’s been developed from waste materials. This fuel, called “Ecosene”, is made in only 24 hours by processing “certain waste plastics”. From one tonne of waste, they can produce 600kg, or ca. 1300 pounds, of Ecosene fuel.
As the oxidizer in the rocket — because fuel must always have an oxidizer — they have chosen to use hydrogen peroxide. This is the same oxidizer used in the Werner von Braun designed German V2 rocket during WWII. The advantage in using hydrogen peroxide is that it is a stable liquid in a wide range of temperatures, unlike other oxidizers, like liquid oxygen, which must be stored at less than -297F. Maintaining liquid hydrogen peroxide is a relatively simple matter in comparison.
The engine for the Skyrora SK-1 is designed to handle these materials, and it is entirely 3D printed. This is quite advantageous for rocket engines*, which typically have tiny cooling channels built into the engine bell, which are extraordinarily difficult to manufacture using conventional methods. This has resulted in Skyrora having a rocket engine with far fewer parts.
Fewer parts not only means it’s less expensive to assemble, but it’s also lighter weight: there is less need for bolts, nuts and lugs to hold pieces together and a lighter engine requires less fuel for launch. Finally, the engine should be more reliable because there are fewer seams and pipes to act as points of failure.
In the past few weeks Skyrora has been actively testing the first engines made using this technique and they were successful. Skyrora fired the engines for a series of 30 second tests without error.
This is an outstanding example of how 3D printing technology can enable designs not previously possible. And in this case, it allows a startup company to launch satellites to 500km orbits.
* The Saturn V's first stage F-1 engines (image below), which helped carry our astronauts to the moon, are the most powerful single-nozzle liquid fueled rocket engines ever flown, with a thrust of 1,500,000 lbs. The F-1 burned RP-1 (rocket grade kerosene) as the fuel and used liquid oxygen (LOX) as the oxidizer. A high speed turbo-pump was used to inject fuel and oxygen into the combustion chamber.
One notable challenge in the construction of the F-1 was the need for regenerative cooling
of the thrust chamber. Chemical engineer Dennis “Dan” Brevik was faced with the task of ensuring the preliminary combustion chamber
tube bundle and manifold
design produced by Al Bokstellar would run cool. In essence, Brevik’s job was to “make sure it doesn’t melt.” Through Brevik’s calculations of the hydrodynamic
characteristics of the F-1, he and his team were able to fix an issue known as ‘starvation’. This is when an imbalance of static pressure leads to 'hot spots' in the manifolds. The material used for the F-1 thrust chamber tube bundle, reinforcing bands and manifold was Inconel-750, a refractory nickel based alloy capable of withstanding high temperatures.
Image from NASA