Periodic Reporting for period 2 - ASPIRE (Advanced Space Propulsion for Innovative Realization of space Exploration)
Reporting period: 2022-01-01 to 2024-03-31
The recent developments in high-power Hall thrusters, are enabling a wide set of mission scenarios. The technological advantages, coupled with the increasing availability of power onboard satellites, are encouraging spacecraft manufacturers to focus on the implementation of high-power Electric Propulsion Systems (EPS).
The most promising scenarios envisage the introduction of a new class of service platforms characterized by versatility and a high level of reusability, the so-called Space Tug. Other applications are the active debris removal, to mitigate the possible collision risks and several exploration and scientific missions, such as Mars Sample Return.
Despite the potential advantages, several factors have limited the possibility of reaching the qualified status for these systems, such as huge costs and availability of suitable test facilities.
ASPIRE aims at increasing to 6 the Technology Readiness Level (TRL) of the European 20 kW Hall-effect EPS. The project covers many aspects, from mission scenarios analysis to upgrade of system design, upgrade of the thruster unit to prequalification, development of alternative/supporting qualification strategies for enabling reduced-cost qualification. Krypton is maintained as baseline propellant. The increase of TRL is pursued through a refined design loop, a test campaign and the development of dedicated analysis and simulation tools.
ASPIRE also aims at augmenting the numerical modelling capability necessary for qualifying such high-power EPS. The numerical models, developed and refined in the frame of this project, are compared and validated with the data gathered during a test campaign of the EPS. Artificial intelligence is used to develop a novel simulation-aided qualification strategy, representing an exclusive European asset for future qualification and flight in the 2020-2030 decade.
The most promising scenarios envisage the introduction of a new class of service platforms characterized by versatility and a high level of reusability, the so-called Space Tug. Other applications are the active debris removal, to mitigate the possible collision risks and several exploration and scientific missions, such as Mars Sample Return.
Despite the potential advantages, several factors have limited the possibility of reaching the qualified status for these systems, such as huge costs and availability of suitable test facilities.
ASPIRE aims at increasing to 6 the Technology Readiness Level (TRL) of the European 20 kW Hall-effect EPS. The project covers many aspects, from mission scenarios analysis to upgrade of system design, upgrade of the thruster unit to prequalification, development of alternative/supporting qualification strategies for enabling reduced-cost qualification. Krypton is maintained as baseline propellant. The increase of TRL is pursued through a refined design loop, a test campaign and the development of dedicated analysis and simulation tools.
ASPIRE also aims at augmenting the numerical modelling capability necessary for qualifying such high-power EPS. The numerical models, developed and refined in the frame of this project, are compared and validated with the data gathered during a test campaign of the EPS. Artificial intelligence is used to develop a novel simulation-aided qualification strategy, representing an exclusive European asset for future qualification and flight in the 2020-2030 decade.
The work carried out, stated through project specific objectives, is summarized below:
SO-1. "Study and refinement of the application cases of a high-power Hall thruster system and consolidation of the system design and requirements."
A value analysis has been performed, to identify specific missions that can take advantage from the use of a 20 kW EPS. A set of specifications was then identified and consolidated. After a specific trade-off analysis dedicated to the system architecture, the design of the Electric Propulsion System (EPS) was performed, based on the value analysis and the mission cases assessed. The system architecture and relevant requirement specifications have been assessed and consolidated at the d-PDR milestone.
SO-2. "Advancement of the electric propulsion system units and characterizing their behaviour in coupled configuration."
The project has matured the design of each subsystem of a 20 kW Hall EPS, to set the ground to qualification and to future in-orbit demonstration. The activities dedicated to the design of the subsystems (Flow Management System (FMS), Thruster Unit (TU) and Power Architecture (PA)) started with the analysis of trade-offs and the identification of relevant requirements at subsystem level. The design has been consolidated with a dedicated CDR for each unit. The units were manufactured and assembled. Test activities dedicated to verification of the design of the FMS, the TU and the PA have been performed. Finally, a coupling test of the full EPS has been successfully performed, resulting in the verification and update of the requirements.
SO-3. "Develop a set of analysis and simulations tools in order to predict the system behaviour in the long term."
ASPIRE has developed alternative qualification strategies, based on advanced numerical tools, aimed at reducing the significant cost and time requirements of a qualification campaign of a 20kW Hall thruster system. The academic Partners in the Project team, each with unique expertise and capabilities in advanced computational and experimental analyses of plasma propulsion systems, collaborated to achieve the expected progress. During the EPS coupling test the plume data necessary for the first validation of the developed simulation tools have been obtained, demonstrating good agreement with simulation results.
SO-4. "Characterize the system at different background pressures and with alternative propellants."
The effect of alternative propellants (Kr) on thruster and cathode performance and discharge stability as well as on the facility background pressure and on plasma-S/C interactions has been investigated through simulations and test. Numerical and simulation tools have been developed to assess facility effects: the set-up of the “thruster + facility” conditions has been defined, and simulations have been run. The TU has been also ignited and characterized in the range of 7-20 kW 300-400 V operating with argon, demonstrating full compatibility with this propellant, too.
SO-5. "Sketch a roadmap for in-orbit demonstration of the high-power electric propulsion system, based on the existing Space Tug designs and on the planned exploration and transportation missions."
The way forward for future EPS qualification has been paved. The engineering assessment has been performed based on the lessons learnt to update the subsystems requirements and providing insights into optimization of the future test campaigns. Several qualification approaches have been analysed demonstrating the time and budget savings the AQS could offer.
SO-1. "Study and refinement of the application cases of a high-power Hall thruster system and consolidation of the system design and requirements."
A value analysis has been performed, to identify specific missions that can take advantage from the use of a 20 kW EPS. A set of specifications was then identified and consolidated. After a specific trade-off analysis dedicated to the system architecture, the design of the Electric Propulsion System (EPS) was performed, based on the value analysis and the mission cases assessed. The system architecture and relevant requirement specifications have been assessed and consolidated at the d-PDR milestone.
SO-2. "Advancement of the electric propulsion system units and characterizing their behaviour in coupled configuration."
The project has matured the design of each subsystem of a 20 kW Hall EPS, to set the ground to qualification and to future in-orbit demonstration. The activities dedicated to the design of the subsystems (Flow Management System (FMS), Thruster Unit (TU) and Power Architecture (PA)) started with the analysis of trade-offs and the identification of relevant requirements at subsystem level. The design has been consolidated with a dedicated CDR for each unit. The units were manufactured and assembled. Test activities dedicated to verification of the design of the FMS, the TU and the PA have been performed. Finally, a coupling test of the full EPS has been successfully performed, resulting in the verification and update of the requirements.
SO-3. "Develop a set of analysis and simulations tools in order to predict the system behaviour in the long term."
ASPIRE has developed alternative qualification strategies, based on advanced numerical tools, aimed at reducing the significant cost and time requirements of a qualification campaign of a 20kW Hall thruster system. The academic Partners in the Project team, each with unique expertise and capabilities in advanced computational and experimental analyses of plasma propulsion systems, collaborated to achieve the expected progress. During the EPS coupling test the plume data necessary for the first validation of the developed simulation tools have been obtained, demonstrating good agreement with simulation results.
SO-4. "Characterize the system at different background pressures and with alternative propellants."
The effect of alternative propellants (Kr) on thruster and cathode performance and discharge stability as well as on the facility background pressure and on plasma-S/C interactions has been investigated through simulations and test. Numerical and simulation tools have been developed to assess facility effects: the set-up of the “thruster + facility” conditions has been defined, and simulations have been run. The TU has been also ignited and characterized in the range of 7-20 kW 300-400 V operating with argon, demonstrating full compatibility with this propellant, too.
SO-5. "Sketch a roadmap for in-orbit demonstration of the high-power electric propulsion system, based on the existing Space Tug designs and on the planned exploration and transportation missions."
The way forward for future EPS qualification has been paved. The engineering assessment has been performed based on the lessons learnt to update the subsystems requirements and providing insights into optimization of the future test campaigns. Several qualification approaches have been analysed demonstrating the time and budget savings the AQS could offer.
ASPIRE contributes to develop, in the mid-term, the European capabilities to compete in the area of high-power EPS at a worldwide level. The use cases and applications of the 20kW-class EP system are an important pillar on which ASPIRE is based, ensuring that the system is an effective response to the needs of the potential end-users.
Space transportation and exploration for scientific and potentially commercial reasons is strongly tied to the development of suitable power and propulsion modules that meet the demanding requirements of these scenarios; requirements that become increasingly more stringent and challenging as the mission destination gets farther from the Earth.
The 20kW system developed within ASPIRE incorporates several design solutions at the forefront of technology. These are necessary due to the challenges associated with such systems, such as high thermal loads, potentially critical response to vibrational loads, high propellant throughput and long lifetime. Surface treatments, additive manufacturing, and magnetic shielding of the thruster channel walls are only some of these high-tech solutions.
To render the studied missions feasible, implementation of high-power EPS based on Hall technology is a necessity. This means that the 20kW Hall thruster system of ASPIRE serves as the cornerstone technology for the realization of near-future robotic platforms and mission concepts which are increasingly gaining attention around the world. As a result, not only ASPIRE has an application-oriented view to development, but also aims at advancing a system that boosts European capacities in the soon-to-come global competition for servicing satellites, tugs and logistics transportation platforms.
Besides, ASPIRE consortium sees the alternative qualification strategy, complemented by predictive numerical tools and the de-risk efforts and investigations, as essential to enable delivering a qualified EPS in time for potential European on-orbit demonstration missions in the second half of 2020s.
Space transportation and exploration for scientific and potentially commercial reasons is strongly tied to the development of suitable power and propulsion modules that meet the demanding requirements of these scenarios; requirements that become increasingly more stringent and challenging as the mission destination gets farther from the Earth.
The 20kW system developed within ASPIRE incorporates several design solutions at the forefront of technology. These are necessary due to the challenges associated with such systems, such as high thermal loads, potentially critical response to vibrational loads, high propellant throughput and long lifetime. Surface treatments, additive manufacturing, and magnetic shielding of the thruster channel walls are only some of these high-tech solutions.
To render the studied missions feasible, implementation of high-power EPS based on Hall technology is a necessity. This means that the 20kW Hall thruster system of ASPIRE serves as the cornerstone technology for the realization of near-future robotic platforms and mission concepts which are increasingly gaining attention around the world. As a result, not only ASPIRE has an application-oriented view to development, but also aims at advancing a system that boosts European capacities in the soon-to-come global competition for servicing satellites, tugs and logistics transportation platforms.
Besides, ASPIRE consortium sees the alternative qualification strategy, complemented by predictive numerical tools and the de-risk efforts and investigations, as essential to enable delivering a qualified EPS in time for potential European on-orbit demonstration missions in the second half of 2020s.