Pioneering bi-liquid propulsion and guided recovery. A first in Swiss student rocketry.

HERMES is a student-built rocket developed by ARIS, the Academic Space Initiative Switzerland at Swiss Federal Institute of Technology in Zurich (ETH), one of the leading universities in the world, known for its excellence in science, technology, engineering, and mathematics (STEM) fields. It’s designed for the European Rocketry Challenge (EuRoC) – Europe’s first and only rocket launch competition for university teams, organized by the Portuguese Space Agency and hosted in the Alentejo region.

With over 55 students working together, HERMES aims to be Switzerland’s first bi-liquid propulsion rocket to reach an altitude of 8000 m – powered by cryogenic fuel and guided to land using a dual-parachute recovery system. Everything from the propulsion to the electronics is designed, built, and tested from the ground up. It’s a true showcase of curiosity, teamwork, and the pioneering spirit that fuels the next generation of engineers.

Where does the HERMES project stand right now?

Thomas: We’ve wrapped up the full design of the rocket and are now transitioning into manufacturing and system integration. As soon as all components are delivered, we’ll begin assembling and testing each subsystem.

Pablo: That’s where things get exciting – designs on paper are now becoming real hardware. Some subsystems have already started early tests, and the engine is going through its first test campaigns. It’s a pivotal point in the project where we can physically see the results of months of design work take shape.

What’s the biggest technical challenge your team is working on?

Thomas: A lot of our systems are sophisticated on their own – the bi-liquid engine, guided recovery, electronics – but the real challenge lies in bringing everything together into a functioning rocket. With so many subsystems, every gram and every interface matters. And because it all needs to be compact and assembled quickly, integration becomes a major technical hurdle.

Pablo: Exactly – and once those systems are integrated, we need to verify that every single part behaves exactly as intended. That means rigorous documentation, detailed testing campaigns, and step-by-step integration. From individual valve tests to full subsystem rehearsals, we're making sure that when we get to the launch pad, we know the vehicle has been systematically verified for flight. It’s a huge effort that involves every team member.

How does curiosity drive innovation in your work?

Thomas: All 55+ members who join us bring their own motivations, but without curiosity, none of this would happen. It’s often the first time any of us has worked on a rocket, and it’s that constant drive to learn and improve that pushes the project forward.

Pablo: Curiosity is what got this project off the ground in the first place. Switching to bi-liquid propulsion wasn’t just a technical upgrade – it was a leap into unknown territory. Every challenge we face, from safely handling cryogenic liquids to feeding propellant at just the right pressure, begins with a “what if?” and evolves through whiteboard sessions, iterations, and breakthroughs. That exploratory mindset is baked into everything we do.

What role does teamwork play in making HERMES a reality?

Thomas: It would be impossible without strong teamwork. HERMES involves nearly every engineering domain, and none of us could do it alone. Especially because we’re all students volunteering our time, it takes mutual understanding and support to keep things moving forward.

Pablo: Absolutely. HERMES exists because over 55 students came together to build something far beyond what any of us could do individually. From printed circuit boards to the recovery system to the remote filling station – every part of this rocket depends on collaboration. That shared responsibility is what makes the project work.

What are the next big milestones leading up to EuRoC 2025?

Thomas: One of the most important steps will be our first full dry run, where we assemble the entire rocket and check whether all systems and interfaces work together as intended. After that comes the Vertical Integrated Firing, where we ignite the engine with the rocket fully assembled and secured to the ground – our final full-scale test before launch.

Pablo: In parallel, we’re moving through a series of critical campaigns. On the propulsion side, we’re finalizing manufacturing of the Propellant Supply System and preparing for cryogenic and flow tests. For guided recovery, we’ll run cargo and drop tests to tune our control algorithms and validate the separation mechanism. Everything leads up to our Flight Readiness Review in September, followed by the HERMES Reveal Event where we present the rocket to our sponsors, friends, and families – and then it’s time to prepare for Portugal.