Vidar III is the third iteration of the Vidar launch vehicle, featuring significant changes to the oxidizer feed system. These changes include redesigned injector and ignition subsystems. This is the first Vidar rocket to feature a functional payload, which is implemented in accordance with the PocketQube standard. Vidar III was the first of the team's vehicles to achieve a successful launch and recovery, at the 2017 IREC.
Wet Mass: 63.1 lbs
Motor Classification: M
Fuel: Aluminized HTPB
Oxidizer: Nitrous Oxide
Drogue Chute Diameter: 37.5"
Main Chute Diameter: 98"
The payload of Vidar III contains an 8.8 pound dead weight in order to fulfill competition requirements. Additionally, the rocket is equipped with a small functional payload including a GoPro, accelerometer, and gyroscope.
Our avionics module houses two commercial Raven altimeters. Furthermore, there is a GPS module on the rocket for recovery purposes. These electronics are activated by magnetic switches and can be armed and disarmed while the rocket is on the pad.
The recovery module consists of a drogue parachute and main parachute housed in a single fiberglass bay. At apogee, the avionics altimeters initiate deployment. CO2 canisters pressurize the recovery module, splitting the rocket and deploying the drogue parachute. At 1500 ft, a secondary electrical signal triggers pyrocutters that deploy the main parachute. The drogue parachute pulls the main parachute out from the recovery module and slows the rocket to 8 m/s.
The Vidar III oxidizer tank is constructed from aluminium. The tank wall fulfills a secondary purpose as the structural airframe, saving weight and increasing stability. The run tank is designed for pressures of 750 psi, with a safety factor of 2.5. It is sealed on each end by a machined aluminium bulkhead. The top bulkhead has a permanent vent, as well as a dip tube to control ullage in the tank. The run tank is filled from the bottom bulkhead, where a hose can connect to the rocket through the outside of the bulkhead.
The combustion chamber houses the rocket's solid fuel. Like the oxidizer tank, it is made of 6061-T6 aluminium at a 4" OD. The fuel grain consists of aluminized HTPB cast inside an ABS tube, with a pseudo-finocyl grain geometry. The nozzle is machined from graphite.
The fin can is constructed from aluminium, with dimensions determined based on flight simulation using data from static testing. Vidar III uses three trapezoidal fins, which are welded to the can that slips over the combustion chamber.
The nosecone is an elliptical shape, with a length of 8". The elliptical shape was chosen because the rocket is expected to remain subsonic. It is machined out of pine wood, and coated with epoxy.
A complete report of this project, including descriptions of onboard and ground support systems, engineering drawings of all rocket components, and a complete set of assembly and launch procedures for Vidar III can be downloaded here.