The engine, Gnome Child MK IV is 3D printed in steel by Danish industry partners and is the same design as the previous rocket Valkyrie. The re-use of the engine design would allow us to skip the hotfires, but this year we decided to have a hotfire anyway. This is done primarily for educating the team, since it’s a very different team than who participated in 2021. A static fire will also be conducted before EuRoC, but the hotfire is a safer way to get team experience with lighting a bi-liquid engine.

The “brain” of the rocket – the flight computer – consists of a backplane with five slot-in boards, each of which has unique jobs which control and monitor the entire rocket. Besides the custom flight computer, we have designed battery boards to monitor and charge the battery, a switch board to easily turn off power, a black box to store the valuable flight data, and a middleman board to take the outputs (pyro channels) of both of the COTS flight computers to deploy the recovery system. We have used two COTS computers to ensure deployment of the parachutes.

Valkyrie uses the fourth iteration of DanSTAR’s Gnome Child biliquid rocket engine as its propulsion unit.

Like its predecessors, Gnome Child v4 uses nitrous oxide and a custom isopropanol fuel blend, and produces 3.1 kN of thrust at a chamber pressure of 19 bar with a specific impulse of 195 seconds. This puts it at the forefront of efficiency among student rocket engines, and to our knowledge it is the only flight-proven student-developed liquid engine in all of Europe.

After the successful launch of Dragonfly in 2020, the engine underwent several design improvements, saving 1.5 kg of mass and reducing the pressure drop in the cooling channels. Due to its regenerative cooling system and well-tested injector design, the engine achieves an extremely high combustion efficiency during operations. Gnome Child v4 is the culmination of three years of engineering, designing and testing, and it is a testimony to DanSTAR’s ambitiousness and dedication.

The Rack is the flight computer which controls the Valkyrie rocket. It is the successor to the Stack, which was used in the Dragonfly rocket. While the Stack consisted of seven unique PCB boards stacked on top of each other, the Rack consists of six unique PCB boards which are slotted into a backplane PCB, in much the same way RAM is slotted into a motherboard on a computer.

This slotting system allows for boards to be independently added, removed, iterated, replaced, and tested easily throughout the entire design process of the Valkyrie rocket.
Each PCB in the Rack has a unique purpose, including controlling the flow of propellants with servo motors, measuring pressures and temperatures in the engine, and wirelessly communicating with Mission Control via on-board antennas.

Each of the six PCBs is equipped with STM32 microcontrollers, all of which are communicating with each other using CAN-FD protocol, a protocol used in modern high-performance vehicles. This ensures that data and information about the rocket is gathered, stored, and transmitted to where it needs to be at all times before, during, and after flight. Many of the Rack boards are also controlling other peripheral PCBs in the rocket which are not a part of the flight computer; the Actuator board is controlling three different Servo boards, the Main board controls the Ignition board, and the Power Supply board monitors four different Battery boards.

The Rack is designed and programmed entirely by DanSTAR’s electronics and software teams, making every aspect of it specialized for the operation of the Valkyrie rocket.

Gnome Child is the name of the rocket engine that propels Dragonfly upwards for the approximately 16 seconds long boost phase. During this period, the rocket sees acceleration of more than 3G as the fuel tanks empty. Around 18 kg of pure propellant is burnt in this period.

The engine is kept cool with an advanced regenerative cooling system, meaning all of the fuel is circulated around the combustion chamber immediately before being injected into the engine. This has a two-fold advantage in that the engine is kept cool, but the fuel is also heated up, reducing the energy needed for evaporation.

This is done in close cooperation with Danish Technological Institute who gracefully offered us the opportunity to 3D print the engine in metal. 3D printing is a new and emerging technology within rocketry that allows for complex designs of cooling systems within the actual engine itself that could not be manufactured with traditional methods. This means DanSTAR is on the forefront within actual rocketry development, and it allows our students to get hands-on experience with state-of-the-art technology before graduating.

RICHARD is short for Robust Internal Controller for High Altitude Rocket Dragonfly. This is our internal flight computer, which additionally also controls the test stand. Sometimes refered to as the flight stack for its many stacked PCBs, it utilises STM32 microcontrollers for a low learning curve and reliable platform to work with. The stacked PCB design allows for easy iterations of individual computer models and adding new features a breeze.

The internal communication is done with a modern CAN interface, the same also used in the automotive industry, which allows the boards to communicate quickly and easily among eachother, ensuring infomation is where it’s needed when it’s needed.

The multi-board design consists of an actuator board, temperature sensor board, pressure sensor board, telemetry board, high-power board, low-power board, and lastly the main board. This configuration has all the functionality that is needed within Dragonfly during flight and recovery, and controls everything from the auto-ignition sequence to recovery events.

When used on the test stand, a test stand board is added to the stack, which increases the amount of connected sensors and valves that can be controlled.

The launch rail is a quarter ton heavy and 13 meter tall behemoth structure that DanSTAR had to develop from scratch to facilitate launching a rocket the size of Dragonfly. The launch inclination can be adjusted down to a single degree because of its special hinge construction. This means DanSTAR can carefully decide the rocket flight direction, which is helpful for safer launch events.

The structure itself consists of a steel center piece and legs with an aluminum mast. This ensures most of the weight is located at the bottom of the structure, making it stable even in windier conditions. The mast is in constant tension because of the steel wires which keep it firmly in place when the launch rail is deployed.

The launch rail is able to be completely disassembled, which is a requirement for shipping it to the US, in order to distribute the shipping weight throughout several flight cases.

The test stand’s fluid system is intended to emulate the one as seen in Dragonfly. This provides a test bed with close to the same conditions present as in the rocket itself, and build on the principles of ‘test as you fly, fly as you test’ laid out by Copenhagen Suborbitals.

Similar to the rocket, it contains three large volumes. A 10 L tank for storing the 300 bar dinitrogen, a 35 L insulated nitrous tank, and a 15 L fuel tank. This is approximately three times as large as seen on the rocket, allowing for quick turnover times between hot-fires by reducing fueling time as well as enabling longer duration engine burns to be test.