Delfi-C³ Structure, Mechanisms & Thermal Control

Structural Subsytem

The Delfi-C³ structure is based on the 3-unit solid chassis from Pumpkin Inc. A 3-unit CubeSat has a total structure length of 326.5 mm and a cross-section of 100x100 mm. The total length of the satellite is 340.5 mm, the extra length is from support feet at both ends (top and bottom). The function of these support feet is to keep the 1-unit CubeSats separated from each other in the P-POD and to house separation springs.

The primary structure consists out of the tube chassis and the top and bottom panels. Together these components absorb the mechanical loads during launch and provide the electrical ground. The primary structure components are made from Aluminum 5052-H32 and are alodyned, the P-POD contact surfaces have been hard-anodyzed.

The secondary structure supports the PCB stack inside the primary structure. It consists out of four threaded rods that run the full length of the structure that are connected to all three the components of the primary structure to increase the rigidity.

The Solar panel structure is a segmented design, mainly to minimize the mass and optimize the overall performance during the launch phase. The main section or substrate of the Solar panel structure supports the GaAs (TEC1) triple junction Solar cells and a separate frame located at the end of the panel suspends the thin film solar cell (TFSC) payload.

Mechanical Subsystem

The Mechanical subsystem of Delfi-C3 comprises several mechanisms to deploy the solar panels and the antennas. There is one similarity between to two mechanisms eventhough the deployables are completely different: the same release mechanism is used.

There are five distinct phases to the deployment of the solar panels on Delfi-C3: hold down, release, deployment, confirmation and stopping/locking. Each phase or action is performed by a different component of the solar panel deployment mechanism. The solar panels are deployed to an angle of 35o to obtain the most omni-directional power from the incoming Sun light; the deployed configuration resembles a tetrahedron.

The antennas are part of the communication subsystem of the satellite. Since the antennas are longer than the satellite body, they need to be folded in a way. The Modular Antenna Boxes (MABs) store the antennas during the launch and deploy the antennas 5 minutes after POD ejection. The hold down mechanism is similar to the solar panels. A lid keeps the resilient antenna in place during launch.  

Thermal Subsystem

The Thermal Control Subsystem (TCS) maintains the subsystem and payload temperatures within the allowable temperature ranges. Excess heat generated by the satellite is dissipated to cold space by means of radiation. Also, the TCS monitors the temperature of spacecraft subsystems and payloads. In order to keep the thermal control subsystem as simple as possible, a completely passive TCS design has been made. No active components like heaters or coolers have been incorporated in the design.

The Delfi-C3 Satellite is free to rotate about all axes. This means that all surfaces will receive heat fluxes at arbitrary times. The satellite does not have a dedicated radiator surface pointing to cold space at all times, the radiators will also encounter direct sunlight. Thermal tapes are used to reflect part of the sunlight and radiate part of the heat.