Exhibition: Students Aiming for the Stars – Rocketry Engineering with ÆSIR

Project Signý marked a historic milestone for ÆSIR, and for rocketry in Sweden, as the first Swedish rocket to compete at the European Rocketry Challenge (EuRoC) in October of 2023. Standing at 2.49 meters and weighing 12.51 kilograms with motor, Signý was designed to compete in the COTS Solid category (for rockets whose motors used commercial-off-the-shelf, solid-fueled motors) and demonstrated precision engineering, reliable recovery systems, and competitive flight performance.

The rocket is built around a modular three-part airframe – nose cone, middle/upper body tube, and lower body tube with fins. Inside are four critical compartments: payload, avionics, recovery, and propulsion. Each bay plays a specialized role, from housing the payload, to ensuring a safe descent with a dual-event parachute system.

At liftoff, Signý’s solid rocket motor produced 2.4 kN of thrust for 1.9 seconds, propelling the vehicle to 65 m/s off the rail and accelerating at 21 G. The rocket ultimately achieved a peak velocity of 352 m/s (or 1,267 km/h, just over Mach 1) and reached an apogee of 3,384 meters – the fastest and highest flight in ÆSIR’s history up until that point.

Beyond raw performance, Signý showcased technical collaboration and innovation. The avionics system relied on dual COTS flight computers with onboard telemetry, while the payload section carried ARISE, a CanSat experiment developed with the German rocketry team at TU Darmstadt. The recovery system performed nominally, deploying in two stages to ensure a safe and controlled landing.

The flight was not only a success but a triumph for the team. Signý earned 2nd place in Flight Performance and ranked 9th overall out of 19 teams. More importantly, it established Sweden’s presence at EuRoC, setting a foundation for future projects such as the upcoming hybrid-powered Project Freyja.

Mjollnir is ÆSIR’s third major rocket project, carrying our most ambitious goal yet: reaching
10-plus kilometers in altitude. This is our largest rocket to date, standing at around 4.5 meters
tall with an outer diameter of 16 cm — also making it Sweden’s largest student-designed rocket!

The project started in 2020 after the successful launch of the Sigmundr rocket in December of
2019. The Mjollnir rocket is propelled by Sindri, a pressure-fed N2O/Paraffin hybrid rocket
engine designed and tested by the association. It is manufactured both internally and with the
help of several sponsors and external suppliers in Sweden, including SAAB and FMV.

The rocket uses a pyrotechnic charge to deploy the recovery system: our first such system to
use both a drogue and a main chute, as opposed to a single main chute or a reefed parachute
as seen in other projects, such as the Signý rocket. It is critical that this recovery system works
as intended, enabling retrieval of the rocket for reusable flight and collection/validation of data.

“With great altitude comes great requirements” — and our case is no exception. Our avionics
and telemetry system aims for live collection of data during flight, making for a great new
challenge not encountered previously by the association.

Some would say that the engine is the most crucial part of a rocket, and they would be correct.
Without an engine a rocket is merely an unconventional coat hanger. A 4.5 meter tall coat
hanger in this case. This brings us back to Sindri, named after the creator of Thor's hammer —
ensuring Mjollnir serves its purpose: to graze the stratosphere, and to leave its mark in the
Swedish space sector — one prominent enough that it cannot be overlooked.

Boasting 4000 N of peak thrust and an expected burn time of about 12 seconds, Sindri features
ÆSIR’s own paraffin fuel grain, whose recipe has been optimized and engineered through
extensive research and numerous iterations. Sindri also features a student-researched and
developed pneumatic valve that operates faster than the blink of an eye.

Who are we?
ÆSIR is a student rocketry association founded in 2016 at KTH Royal Institute of Technology in
Stockholm. We have around 60 members every year, which are all students at KTH. Roughly
half of us are international students and we cover many disciplines and levels of study, although
most of our members study Aerospace Engineering, Computer Science, Vehicle Engineering,
Electrical Engineering, Engineering Physics and Mechanical Engineering.

The association is focused on rocketry, but is much more than just a place where rockets are
built. It is a community and meeting place for people with interest in rocketry or space. Our
members also get the chance to experience real-world advanced engineering projects, that can
provide them with skills and knowledge which make them stand out from the crowd.

Our Mission
ÆSIR was created to provide a forum for students with an interest in rocketry, where they can
develop their passion and knowledge in practical aerospace projects. Our goal is to educate
students in rocketry and engineering and give our members real world engineering experience.
The activities of the association will further strengthen the position of KTH as one of the leading
Aerospace Universities.

Our mission is to become one of the top student organisations for rocket building in the world,
by breaking and holding the student rocketry altitude record in Europe (which is currently above
63 kilometers). Ultimately, we intend to reach altitudes beyond the 120 kilometer mark.