A group of ETH Zurich Aris students is attempting to do something only a few nations have done before: they are designing and testing an engine that uses controlled detonations. The Rotating Detonation Engine (RDRE), a system which can increase efficiency, is a detonation rocket engine.
This new technology allows fuel to be burned at a constant rate rather than a rotating state.
Four screens are huddled around a table in a small hut that serves as the hub of control. The operators work out-of-sight at a distance safe from the booster. The footage from multiple cameras shows the hexagonal part of copper, which is roughly plate size and looks like an over-sized nut.
It’s then placed in a disc made out of stainless steel attached to a trailer.
The complex testing rig that surrounds it is made up of aluminum profiles, tubes and pipes, sensors cables and pressure tanks. The liquid oxygen is vented from the engine and pre-cooling of the system. You can observe green light all over the place under the high-speed cameras. The data collected will only indicate if a detonation has occurred. If this project succeeds, Aris will be the first team of students in the world that ignites a liquid-fueled RDRE.
Copper was used to print the engine. On the rear is where you will find the injector. The injector is located on the back.
It is a tension that you can feel. There are announcements coming from the control centre that punctuate the silence. “Temperature: -100 degrees. Pressure: nominal.” The site has been cleared by security guards. Stage is ready.
Mattia Rousseli, a third-year student in mechanical engineering, created the injector.
The team decided to use liquid oxygen and propane as both fuels and oxidizers for the rocket engine.
The Roosli injector ensures a precise mixture is injected. Pegasus is a student-funded project that will build and test a biliquid RDRE. Materials, funds, and services were provided by industry partners.
The expectations are high. RDREs are capable of increasing power from 10-20% with the same fuel.
The detonation creates waves of explosive energy that circulate in an area and generate extremely high temperatures, unlike steady combustion. This allows for a more efficient use of energy and reduces the complexity required to build engines.
Fuel alone accounts for up to 90% of the launch mass for a rocket. Any small improvement in fuel efficiency can have a huge impact on spaceflight by either lowering costs, or allowing heavier payloads.
But significant challenges still remain. The detonation wave can move as quickly as 20,000 times a second through the annular room, causing materials to be compressed.
NASA tested the RDREs in the field, Poland tested the liquid version, but Japan remains the only nation to have successfully lit a RDRE from space. These students would be among the elite pioneers if Pegasus could hold even one second of stable explosion.
Roosli reflects on his trip: Rockets are fascinating to me, because they can fly by simply accelerating the fuel in reverse.
It is actually very simple.
He embraced the unknown after two years of studying: There is so much that is yet unexplored. No one can give you the exact steps to take.
It’s pretty awesome to be at the cutting edge of science.
It was impossible for his injector to cause echoes. Sketches, calculations and team discussion were followed by 3D-printed prototypes.
You don’t have to be a genius to create a rocket after just two years of studying. “You go step-by-step and work together.”
Aris places a high value on knowledge transfer. Each year teams are formed to teach and mentor the next generation.
Sometimes, lessons have been learned through broken parts. Pegasus is getting help from a startup nearby that builds RDREs. ETH is an infrastructure hangar, with workbenches and 3D printers as well as meeting rooms and testing spaces.
Safety comes first. Before ignition, engines are pressure and flow tested. The team spent months perfecting safe protocols. Six hours prior to the test, they met in a meeting for a short briefing. Each member wore a different colored waistcoat to indicate their roles: Test conductor: Blue; Safety Officer: Green; Engineer: Orange; Data Acquisition Specialist: Yellow.
Equipment loaded: gas canisters, cables, extinguishers and snacks for the brain.
The trailer containing the test stand was transported to the airport the next day. The military police opened the gate. Team members deployed rapidly, using checklists and connecting oxygen cylinders in order to fill the valves. Instantly, ice crystals appeared.
At 19:00 CT, the engine started. There was a hiss, thud and screech followed by fire. Was it detonation?
They checked the sensors and found that they were not working. The team refueled the engine and made adjustments to parameters. The engine temperature reached a cool 130degC at 8:45pm.
“3, 2, 1, go!” The fire streamed out in a steady, long line, whistling and buzzing at high frequency.
Roosli smirked faintly. Radio confirmed the news: “Yes! “Yes! Before the focus returned, cheers erupted.
Pride replaced tension as the dismantling started. As the dismantling began, pride replaced tension. The students had achieved something that only few have done in the history of mankind: they ignited liquid fuel to spin a detonation engine.
