Objectives

The availability of an autonomous mean of positioning in a geostationary platform is essential in reducing the dependence on the ground control, especially when low-thrust electrical propulsion is used to transfer the satellites to the GEO orbit, a manoeuvre that lasts several months. In this case, the on-board GNSS function can autonomously feed the avionic systems in charge of controlling the trajectory and the attitude, and schedule in this way the requested thrusters actuations and attitude variations.

Nowadays the use of GNSS Receivers in GEO satellites is a reality, although their cost is quite high. The first part of the project has been focused on the cost-wise analysis of the architecture of a GNSS receiver to identify the potential areas where a significant reduction of the recurring cost can be achieved.

In the second part, a novel architecture of the RF-IF section of the receiver has been designed and manufactured using a highly integrated solution based on a hybrid RF-digital MMIC developed for this purpose in the frame of the project.

Finally an elegant breadboard incorporating both the RF-IF section and an AGGA-4-based digital board has been assembled and tested to verify the overall performance of the GNSS receiver.

Challenges

• Revisit current navigation receiver implementations for GEO satellites to define an architecture and physical implementation compatible with the target cost of 200 k€ for the final space qualified flight model.
• Develop an elegant breadboard implementing an innovative, highly integrated RF-IF section using a new hybrid RF-digital MMIC design.

System Architecture

The Elegant Breadboard designed and developed in the frame of the project consist of a RF-IF section, based on a highly integrated MMIC designed and manufactured ad hoc, and of a digital section based on AGGA-4 processor. These two sections represent the core elements of a GNSS receiver and allow to verify the overall performance.

Plan

The project started in May 2017 and is split into three phases.

Phase 1: architectural trade-off, receiver specifications and preliminary design. Phase 1 ended with Preliminary Design Review, held in November 2017

Phase 2: EBB detailed design (RF-IF board and digital board) and  MMIC manufacturing. Phase 2 ended with Detailed Design Review, concluded in July 2018.

Phase 3: RF-IF Board manufacturing and test and EBB integration and performance test. Test Review Board held on June 2020.

The duration of phase 3 has been affected by the COVID-19 pandemic.

Current Status

The project has been completed.

Companies

Thales Alenia Space Italia

https://www.thalesgroup.com/en/worldwide/space-italy

Italy

Digimimic S.r.l.

https://digimimic.com/

Objectives

The aim of this project was mainly to reduce the mass of the packaging of an already existing typology of battery while implementing an individual cell replacement feature. The mass improvement will  increase as well specific energy of the battery making it also interesting for GEO missions. The individual cell replacement feature will be mainly useful if an issue occurs on the battery during spacecraft MAIV/T activities. This allow to just replace one or multiple cells affected by the issue instead to the whole battery.

Challenges

Main challenges of this project were to reduce the structural mass of the battery packaging by more than 50% while introducing a new feature of individual cell replacement.

System Architecture

System architecture is to replace actual battery packaging made of aluminium by a CFRP structure which have a dedicated thermal heatsink for cell thermal dissipation. The cell clamping system developed allows as well individual cell replacement

Plan

The project started with a state of the art and a material & process trade-off. The packaging factor and mass breakdown of several batteries was analysed. After choosing the materials and processes, the optimisation and sizing of the packaging was performed wrt thermal and mechanical loads. An EM was then manufactured and tested and compared to the prediction (correlation) and to the existing packaging.

Current Status

Project has been completed.

The resulting manufactured Engineering Model (EM) battery showed a mass recovery of almost 2kg with respect to the corresponding battery. The target of 1.3 for the packaging factor was almost achieved with a value of 1.327.

Battery test results showed good thermal and electrical performance as expected in the simulation and similar to those of the comparative battery. Mechanical tests were unsuccessful and stopped after Random Z load because of glue detachment between the CFRP core and the thermal middle plate. This non-conformance occurred during thermal cycling but it is more linked to the gluing process and surface preparation than the thermo-elastic loads.

Almatech is nevertheless confident that both mechanical performance and packaging factor target can be achieved in further project steps by especially mastering the bonding process between interfaces and by modifying slightly the thermo-mechanical design.

Companies

Almatech SA

http://www.almatech.ch

Switzerland

SAFT SA

http://www.saft.com

France

Objectives

The intention of this study is based on the fact that for modern Electric propulsion systems the PPU is representing one of the most complex but also one of the most expensive items. This is driven by very specific requirements for the different thruster technologies which require a very strongly customized design and complexity. Beside the different ranges of the output parameters for the needed voltage- and current supplies there are other driving requirements like robustness to high noise during ignition of the thruster, accepting of alternating ground shifts during operation or to cope with shorts at the output caused by beam events.

The intention of this study was to start at exactly that point where technical solutions are available but always tailored for only one dedicated thruster technology and always customized for a specific mission.

The activity comprises the evaluation of the different requirements, finding the best intersection of them, defining a suitable PPU architecture and finally performing the detailed design activities, build and test the modular PPU breadboard. Accompanying to these activities several trade-offs and analysis have been performed to determine the most suitable technologies and topologies.

Challenges

The main challenge of this study was to develop a PPU which provides a high grade of flexibility and modularity to serve a wide spectrum of thruster assemblies. This approach combined with the approach that the developed PPU shall also be competitive in terms of recurring costs, manufacturing and testing effort but also provide a small mass and acceptable envelope have been the demanding challenges of this study.

System Architecture

After detailed trade-off, the most suitable PPU architecture — following the modular approach of this study —  a standard core design was determined which is representing a kind of platform that can be customized individually. The idea behind the modular standard core approach is to define a standard core which contains all non-thruster specific power supplies. However, all thruster specific supplies like the RFG supply for the RIT are also added into the same box. The main logic of this concept is to provide a full developed core periphery with the flexibility to customize for the different thrusters and missions. Beside the possibility to add the thruster specific supplies to the box, for the core harmonised electrical and mechanical I/Fs have been defined to allow the easy exchange of the modules if this is required for a dedicated application.

The block diagram of this PPU concepts and the thruster periphery is shown below. 

The PPU follows a modular design concept, which allows an easy tailoring of the unit for different satellite platforms and operation concepts of the propulsion system. Beside the measures to prevent single point failures or failure propagation, no additional redundancy within the PPU is established in alignment with the trade-off results. 

Plan

Baseline Requirements Review (BRR), Architecture Review (AR), Design Review (DR), Test Readiness Review (TRR) and Final Review (FR)

Current Status

Completed 

Companies

Airbus

https://www.airbus.com/space/telecommunications-satellites.html

France

Objectives

There are two primary objectives for project ICEYE:

• The use of the FEEP (field emission electric propulsion) ion thruster technology for propulsion. This allows high efficiency in terms of propellant use and superior controllability from the sub-µN range up to the mN range.
• The PPU for operating the thruster is based on COTS components and was specifically tailored to the needs of a FEEP propulsion system. The in-orbit test is used to verify its functionality.

The following secondary objective for project ICEYE is:

• The housing for the seven IFM nano modules is made of aluminum with the additive layer manufacturing process combined with CNC machining and surface treatments. This mission will also prove the usability of ALM manufactures for space applications.

Challenges

Apart from the ion emitter itself, the module including housing, reservoir, heater and electrodes needs to be miniaturised. This is particularly challenging since a high voltage of up to -10 kV / +10 kV is being used.

The PPU being able to generate high voltage for emitter and extractor, drive the heater and neutralisers, and measuring the reservoir contactless, has been developed from scratch with COTS components only.

Compared to existing ion sources, the large amount of propellant (up to 250g) presents a challenge in terms of heating, surface tension and spilling.

System Architecture

The cluster for project ICEYE consists of seven individual and individually controllable IFM nano thruster modules embedded into a common housing.

A common power bus is shared between the seven individual modules but mechanical relays can selectively remove modules therefrom. Two RS-485 communication busses are implemented (one branch with three, another with four modules attached to) which allow communication with the OBC.

The RS-485 transceivers are rad-hard and guarantee unblocking the bus once the supply voltage is removed. This allows the OBC to decide which IFM nano thrusters shall be active.

Plan

The project started after the PDR. Before that, prior work was performed to estimate the major risks of the project. All work before kick-off has been reviewed in a PWR. After the design of the housing and the mechanical and thermal simulation, a CDR was successfully completed. Then the thrusters and the housing were manufactured. The performance of the IFM nano thruster modules were determined individually. After integration into the common housing and a successful operation of the entire cluster, the Flight-Readiness Review was completed.  In-orbit commissioning of the thrusters was successful and the thrusters are now operating as intended.

Current Status

The project is now complete and the in-orbit experience has helped to substantially boost further sales of the IFM nano thrusters. This project was supported under an ARTES Competitiveness & Growth – Demonstration Phase – Atlas project.

Related Links

• ICEYE

Companies

FOTEC Forschungs- und Technologietransfer GmbH

https://www.fotec.at/

Austria

Objectives

The project aim was to take the previous ‘breadboard’ development of a High Pressure Proportional Valve that started in 2008, further develop all aspects of this design and then build an Electronic Pressure Regulation sub-system and take it through extensive development and Engineering Model testing with a range of commonly used spacecraft propellants.

System Schematic  (shown with redundant branch)

The valves feature Nammo’s heritage hard sealing technology, making the whole system compatible with Xenon, Helium, Nitrogen, Hydrazine, and MON. Note the use of a specifically designed Heater unit in the above schematic to eliminate Joule Thompson issues regarding Xenon phase change through orifices at higher flow rates such as those required for Cold Gas Thrusters. The heater is not required for the other gases and propellants.

Challenges

The key challenges associated with meeting the demanding project objectives were:

• Coping with a pressure range from 0 to 310bara, a flow range of <3 to 600mg/s Xenon & Helium and accommodating 3 different propellants (Xenon, Nitrogen and Helium) with a single proportionally regulating valve design.
• Overcoming Xenon Joule Thompson issues
• Developing hard material sealing technology
• Thermally compensating design

System Architecture

The Engineering Model EPR can be seen above in ‘as tested’ configuration. The gold plated Xenon heater can be seen on the left. This flows pre-conditioned Xenon into the High Pressure Proportional Valve (HPPV) immediately to its right and thence to the thruster interface at the bottom of the picture.

The HPPV seen at the top is functioning as a high pressure isolation valve as this has been proven at 310bara to perform to requirements. The valve is low mass and compact when compared with mechanical isolation valves, therefore an ideal choice for our system.

Plan

The ARTES project took the Nammo Electronic Pressure Regulator system through from design concept to an all-welded, flight representative, extensively tested Engineering Model. The testing was equivalent to the perceived flight Qualification Testing that represents the next stage of the EPR readiness for flight.

Current Status

As stated above, the EPR is at a development stage where it is ready to undergo a Critical Design Review (CDR). Upon successful completion of the CDR the Electronic Pressure Regulator is ready to undergo full qualification. Full qualification would involve qualification level environmental testing (vibration, shock, thermal cycling, etc.) and qualification level testing including on/off cycles and Tvac testing.

The Nammo thermal vacuum facility used for EM testing is shown below.

Companies

Nammo UK

https://www.nammo.com/who-we-are/locations/uk/westcott/

United Kingdom