COMMS Antenna deployer

Introduction

The antenna deployment mechanism will consist of two elements: a dyneema string attached to the end of the COMMS antenna, and a low-impedance resistor mounted on a lateral board. The dyneema string will wrap around the satellite as illustrated in the renders below and will be connected to the low-impedance resistor, also known as the thermal knife. The cable needs to be tensed so that the antenna cannot wiggle during the launch.

Description

The resistor is currently set at 4.7 Ohms, but further tests—including deployment in vacuum conditions—are planned to confirm its suitability. Other resistor values may offer better performance, so a trade-off analysis is needed to optimize results.

Due to the power limitations of our PocketQube, the system does not include a second thermal knife. However, the thermal knife can be activated multiple times if necessary, ensuring proper deployment.

The wire connecting the antenna to the thermal knife is a dyneema, specifically commercially used fishing wire made from polyethylene. More precisely, it is ultrahigh-molecular-weight polyethylene (UHMWPE), a material known for its remarkable properties, including extremely high tensile strength (up to 26 kg), making it ideal for high-stress environments, such as rocket launches. In terms of thermal properties, UHMWPE has a breaking temperature between 120°C and 130°C.

The antenna is made from metallic metric tape, a coated stainless steel material. One end of the wire will be secured to the antenna with a knot, while the other end will be tied to the thermal knife using a knot through the holes designed for this purpose on the lateral board. A final knot design is yet to be selected, as it will need to be validated during the vibration phase of environmental testing.

There are two inhibitors preventing the antenna's deployment:

1. Physical Inhibitor: The kill switches on the satellite, which disconnect the PocketQube from the battery while inside the deployer.
2. Software Inhibitor: The INIT mode, which enforces a 45-minute standby period after the kill switches are depressed, as described in the Satellite Operation Modes section.