The Pacis 3 Tx active antenna has sailed through its next major milestone on its path to validation for SpainSat NG. Airbus Defence and Space has successfully tested the Active Antenna Thermal Model at the IberEspacio facilities in Madrid. The latest testing process has demonstrated that the design and thermal hardware mean that the model is capable of extracting heat from the antenna to keep the amplifiers within their operational range.
What is Pacis 3?
Pacis 3 is a Partnership Project (PP) between the satellite operator Hisdesat and the European Space Agency (ESA), supported by Spain’s Centre for the Development of Industrial Technology (CDTI). The Pacis 3 project aims to develop and integrate innovative antennas up to in-orbit validation.
The thermal design of an active antenna such as the Pacis 3 Tx is a complex challenge which is key to the success of the project. Such active antennae need to be able to perform efficiently in challenging conditions as they show very high dissipative loads combined with a high heat flux density. Therefore, all dissipating units need to achieve a reliable temperature equalisation to guarantee that the antenna will perform as required.
Thermal design concept
The design concept for meeting the challenge of thermally controlling the Dual State Solid Power Amplifiers (DSSPAs) of the high dissipative Active Antenna involves a system of six Collecting Heat Pipe Assembles (CHPAs) connected in parallel to eight operating Loop Heat Pipes (LHPs). The CHPAs collect the heat from the antenna itself and the LHPs then transport the heat to four dedicated radiators, remotely located on the S/C wall panels.
Felix Beck, Thermal Engineer for Telecom Satellite Programmes at ESA commented “Whilst the selected concept has great potential in terms of thermal performance and flexibility, in the past, operating several LHPs in parallel has led to a degree of uncertain and unstable behaviour. This has been due to the intrinsic features of the LHP performance, particularly during start-up but also during transients. The design focus here was to resolve those issues and create a reliable control.”
Robust testing
In order to demonstrate and prove the effectiveness of the thermal design concept, engineers built an Active Antenna Thermal Model (Tx-TM) and planned an extensive testing campaign. The tests are designed to cover performance in a wide range of operational scenarios, as well as under steady state and environmental boundary conditions. The testing under vacuum conditions, the first part of the campaign, was completed successfully.
The results of the latest testing are very encouraging. Not only do they confirm the assumptions made during the design phase, but they also provide important evidence about the overall performance and robustness of the thermal control system in the following areas:
- heat transport capability
- thermal conductance across the complete thermal chain
- thermal gradients between the LHPs and DSSPAs dummies.
- LHP start-up, parallel operational and shut-down behaviour, even with an uneven heat load distribution on the LHP evaporators and with different sink conditions for each LHP pair
- heat sharing capability and in particular outstanding robustness to LHP dry-out failure
Responding to the latest test findings, Paula Prado Montes, Antenna Thermal Architect from Airbus Defence and Space said “As the schedule of Pacis 3 is so tight this has been an important corner stone to gain the right confidence of the thermal system to proceed with the build of the flight hardware.”
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