The key design issues currently reside with the pointing mechanism development. The ETPM offers a robust configuration capable of supporting different Hall Effect thruster variants.
The ETPM deployable building blocks are also designed to be (in the future) compatible for antenna deployment.
The ETPM is a critical component for the mission execution. As such, it must propose a robust and reliable solution to ensure flawless mission executions while ensuring a clear mass gain justifying its competitivity compared to existing solutions.
To meet this goal the ETPM structure and single components must be thoroughly tested and meticulously designed, manufactured assembled and tested.
When compared to existing thruster module assemblies, the benefits of the ETPM may be listed as:
- Offers mass benefits for any given thruster payload
- Supports a wide range of thruster variants
- Enabler for full electrical telecom satellite
- Modular, completely self-contained assembly
- Low shock, non-explosive release of the launch lock assembly
- Benign load transfer function
- Proven actuating life
- Competitive cost compared closely to currently existing thruster pointing systemproposed solutions, through a standardized and multi-application building block approach.
The Extendable Thruster Pointing Mechanism’s, subject of this study, aims at enhancing the overall competitiveness and performance of E3000 satellites in order to fully answer operators’ needs and requirements. The recent introduction of much cheaper launcher for low/medium launch masses created an economic opportunity to extend the use of PPS on a much wider range of payload. The use of EOR (Electric Orbit Rising) instead of chemical propulsion for the transfer phase allows reducing propellant mass, and therefore to increase the maximum allowable spacecraft dry mass.
The Extendable Thruster Pointing Mechanism’s, is one of the main enablers allowing an intensive and efficient use of electric propulsion on Eurostar 3000 telecommunications satellites, both for the orbit raising phase (EOR) and the station keeping manoeuvers. As a consequence, it contributes to Eurostar 3000 competitiveness allowing AIRBUS DS to:
- Propose a reduced cost per transponder
- Access to a larger range of launchers, with cheaper launch costs
The proposed Extendable Thruster Pointing Mechanism’s allows:
- To minimize the orbit raising duration, this phase being done with the maximum possible thrust, with all HET oriented towards the same direction (satellite Z-axis).
- To optimize the station keeping strategies with both a better North-South station keeping efficiency and the ability to perform East-West station keeping and angular momentum control.
The missions of the Extendable Thruster Pointing Mechanisms are to deploy and point a payload supporting Hall-Effect Thrusters (HET), and to allow the HET operation in various phases of the mission. Its mission is decomposed in several phases:
- Launch in stowed configuration, clamped on the Satellite Service Module Y walls.
- Release & Deployment : this phase occurs during the first hours of mission
- Orbit raising, in a configuration with the thruster force direction along Zsat. The Hall Effect Thrusters are operated with the P-DPS pointing mechanisms operating in closed loop for control of satellite angular momentum.
- Operational Mission: after reconfiguration such that the thruster force direction is close to Y-sat and aligned with the center of mass, the HET are operated for station keeping maneuvers, with the DPS pointing mechanisms operating in closed loop for control of the satellite angular momentum. These maneuvers allow performing the control of inclination, longitude and eccentricity, and control of the angular momentum.
The ETPM is launched in a stowed configuration, locked in position by a Hold Down Release Mechanism. The HDRM is released after the launcher separation by a low shock, non-explosive device.
The extendable pointing mechanism is then deployed to its thrust position through a defined sequence. Once deployed, the thruster module can be re-positioned using the complete capacity of its rotating compact hinges. The hinges are driven by stepper motors powered from the onboard control electronics.
The Xenon fuel is routed through the ETPM through a low pressure line to the thruster module assembly in any pointing position with a careful care to its thermal environment and space environment protection.
The development of the ETPM prototype and linked R&D of the ARTES 5 Line 1 PPS equipments is critically linked into the supply of Airbus Defence & Space's Eurostar 3000 / Alphabus / Eurostar NEO spacecraft platforms.
The ETPM is well placed to equip flight programmes on Airbus Defence & Space’s Eurostar3000 platform within the next 2 years.
The ETPM will further assist to enhance Airbus Defence & Space's product portfolio, adding value for money to their large haul spacecraft platforms, increase business base and improve and develop an additional EHP/ Airbus Defence & Space collaboration on a complex product.
The ETPM design with regard to major design aspects has been declared successful versus EuroStar 3000 applicable requirements. Further risk mitigation activities have been performed at component and building blocks technological level prior achievement of full qualification status to occur 2015.