Because fuel accounts for 80 to 90 percent of the total weight when launching rockets, even efficiency gains of only a few percent are worth their weight in gold. Rockets could fly more cost effectively – or carry larger loads into space. 

Research into such engines has been ongoing for a long time, but they are not yet ready for the market. The challenges are simply too daunting and too numerous. 

Consider, for example, material loads and stress: The detonation waves travel through a ring chamber up to 20,000 times per second. At high frequency, the waves expose the material to extremely high pressure and very high temperatures. 

Tests with RDREs have already been carried out in various countries. In the USA, NASA has ignited engines on a larger scale on ground-based test stands. A Polish institute has tested RDREs with liquid fuel. Japan is the only country to have actually ignited such an engine in space. 

So, if the Pegasus engine produces stable detonation waves for even a single second today, the team members will be able to count themselves among an elite group of genuine pioneers.  

After two years of studies: just go for it 

While his team colleagues pack the boxes for the test in the hangar, Mattia Röösli tells us how it all began. 

He became interested in the subject early on. “Rockets fascinate me because they fly simply by accelerating fuel backwards. The principle is actually quite simple.” 

After two years of studying the basics, he was motivated by new territory: “There is no one who can tell you exactly how to do it because so much is still unexplored. Working at the forefront of research like this is pretty cool!” 

The injector that Röösli has developed is a critical component. RDREs require highly precise injection technology that must mix and deliver the fuel in less than a millisecond, without the detonation wave reverberating back into the supply lines. 

How do you approach such a task? He spent three weeks familiarising himself with the subject. Then he just got started. “Maybe I shouldn’t have read so much,” he says in hindsight. “It’s a mistake to think you can fully understand the topic before you start. There are simply far too many unanswered questions.” 

Sketches, discussions, prototypes 

So, he started with something higher-level: the question of which elements belong to such an injector and how they can be connected. “The first thing you do is make sketches and discuss them as a team. The others then draw your attention to things you have not yet considered. Then you continue calculating and sketching. You break big problems down into smaller ones until they become solvable.” 

The team gradually progressed to the first prototypes from a metal 3D printer. “When the first prototypes are on the table, new challenges become apparent again.” 

Röösli emphasises: “You don’t need to be exceptionally talented to develop a rocket engine after two years of study. You go step by step and help each other.” 

The predecessors serve as coaches, and a start-up looks on 

The expertise of the Aris project team was also very helpful last year – they pass on their knowledge year after year as coaches. If something goes wrong with one team, the next team benefits from this experience. A charred electronic component on a shelf of prototypes in the hangar bears witness to such a lesson.