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Hybrid engine
R&D 2019-2022

The Hybrid engine project was a multi-year project aimed to develop Propulse’s first SRAD engine. It started as a part of the main project for Team 2020, with Project Mjølner, but became a research and development project. It formed the basis for developing a liquid engine for Project Bifrost.


Paraffin & liquid Nitrous Oxide


Target thrust
5000 N


5.8 m


Target Apogee
3000 m

Engineering breakdown

Bifrost's bi-liquid propulsion system is fully researched and developed in-house, using knowledge and test facilities from our previous Hybrid engine R&D project. The airframe is in large a flight-proven design previously used on Stetind (2021) and Birkeland (2022), with the SRAD recovery system and avionics also building upon previous years' designs. You can find a more detailed description below.


Outer Structure - The airframe is load-bearing and the lower half is filament wound carbon fiber, while the upper sections are glass fiber due to avionic’s requirement of radio transparency. Four carbon-fiber fins ensure proper vehicle stability.

Inner Structure - Designed with modularity and assembly in mind, while still handling flight forces and minimizing the mass.


Payload - Biosat, a 3U CubeSat made by our friends at Orbit NTNU.

Recovery - Ensures successful recovery of the rocket with two self-sewn parachutes. The separation of the forward and aft airframe is done by filling the airtight chute bay with pressurized gas. The recovery functions can be activated by both our self-designed system and a COTS system.

Avionics - The flight computer, engine control and other electronics. Responsible for controlling and monitoring propulsion and recovery systems, gathering and logging sensor data, doing onboard processing, and transmitting data to the ground station.

Feed System - Supplies the combustion chamber with fuel and oxidiser, allowing the engine to generate thrust once ignited. The system consists of propellant tanks, a nitrogen pressurization system, and plenty of valves and piping to enable filling, control and emptying of the tanks.

Combustion Chamber - As the most complex part of the rocket, the combustion chamber is where the propellants are injected and burned to provide thrust. The system consists of a 3D printed burn chamber and bulkhead, an injector plate and an exit nozzle.

Ground Station & Radio Tracker - Receives and stores telemetry data from the rocket, as well as arming the software and enabling the filling process. The radio tracking system keeps the ground radio pointed to the rocket, ensuring an optimal connection and an additional source of position data to aid with recovering the rocket.


Test Site - The facilities & logistics concerned with propulsion testing in a controlled environment. Initial hardware is tested in a horizontal configuration, with the combustion chamber parallel to the ground. New generations of flight hardware will eventually be tested in a vertical configuration.

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Welding of the test stand
Preparing for engine testing
Hotfire #1
Hotfire testgroup
Avionics flight computer PCBs
Kalman filter course at the office
Successful coldfire day
Propulstion test setup
Sewing recovery drogue chute
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