Success of the ATHENA ion propulsion system for small satellites

In recent years, the space propulsion sector explores new systems to grant mobility to satellites through ion propulsion, as it is lighter and cheaper.

Now, for the first time, a Spanish company, Ienai Space, founded in 2019, is entering the market thanks to its propulsion technology developed for small satellites. The company recently received two contracts with the European Space Agency (ESA) to bring the technology to commercialization by the end of 2023.

The recognition that Ienai Space now receives with these contracts and with the interest in it aroused in the astronautics sector is due in large part to the success of its technology achieved in space. On October 1, 2022, Ienai Space, based in Leganés (Madrid), became the first Spanish company to have a propulsion system in Earth orbit, entirely designed in Spain; specifically an experimental version of his ATHENA system. The launch was carried out with a Firefly Alpha rocket, developed by the American company Firefly Aerospace.

The launch put two satellites weighing less than 1 kilogram into orbit.

The goal of that first demonstration mission was to test the thrusters in the space environment, after extensive qualification on the ground. Specifically, the mission sought to demonstrate the ability to extend the time in orbit of satellites that, without propulsion systems, would have fallen back to earth due to friction with the tenuous Earth’s atmosphere that is still in orbit. After the mission is over, it is this friction that is harnessed to ensure that the satellite re-enters the earth, preventing it from becoming space junk.

ATHENA (“Adaptable THruster based on Electrospray powered by NAnotechnology”) is an ion propulsion system that can be embarked on practically any platform, since it is completely modular and scalable, in terms of operating power and quantity of propellant on board. Scalability and its high efficiency are the main differences, a technology based on ‘electrosprays’, which separates it from plasma-based electric propulsion systems.

The ‘electrospray’ technology developed is based on the extraction and acceleration of the ions that form the ionic liquids, through the application of a potential difference between some “emitters” and an extractor grid. The company’s main innovation is related to the design and manufacture of these “emitters”, for which micro-manufacturing techniques are used. Thus, greater motor efficiency is achieved. The design and manufacturing methods have been patented by Ienai Space, together with the Barcelona Microelectronics Institute (IMB).

Distribution of micromachined chips on a silicon wafer. (Photo: IMB / CNM / CSIC)

“The objective of the ATHENA engines is to offer the space market a very compact and low-power but highly efficient propellant, capable of being integrated into small-sized satellites. This has not been possible until recently, because attempts to miniaturize other more traditional technologies have not been successful; hence the need to develop a completely new technology”, indicates Daniel Pérez, CEO of the company Ienai Space.

The founders of the company are Mick Wiijnen, Daniel Pérez Grande and Sara Correyero Plaza, the last two alumni of the Polytechnic University of Madrid (UPM) where they obtained their aeronautical engineering degree in 2010 and 2015 respectively.

The technological development embodied by Ienai has been possible thanks to the transfer of technology and knowledge carried out by the Higher Council for Scientific Research (CSIC) in Spain, in a collaboration that began at the end of 2019.

“The collaboration consisted of manufacturing the emitter matrices with a conical shape and a height of hundreds of microns and, on the other hand, in demonstrating the possibility of nanostructuring this three-dimensional surface to allow control of the operating regime of the emitters. , thanks to the control of the flow of propellant to them”, indicates Borja Sepúlveda, a researcher at the Institute of Microelectronics of Barcelona.

To manufacture the emitting microcones, the extensive experience of the White Room of the Barcelona Institute of Microelectronics in processes of deep silicon micromachining by reactive ions was used, which allowed the generation of structures hundreds of microns high. The nanostructuring of the 3D surface was carried out using colloidal nanolithography technology, which had been previously developed for wireless cellular electro-stimulation devices, in a collaboration between the Institute of Nanoscience and Nanotechnology (ICN2) and the Institute of Microelectronics of Barcelona. This micro- and nano-fabrication process gave rise to an international patent application.

“The nanostructuring of three-dimensional and sharp surfaces was one of the biggest challenges, as well as demonstrating the ability to tune the density of nanostructures on the surface, which is essential to control the type of emission”, indicates Sepúlveda.

In the White Room of the Institute of Microelectronics of Barcelona, ​​the results were good and, according to Roser Mas, a process engineer from the aforementioned institute, “a high level of ionic emission was achieved in the propellant”.

At this time, work continues on optimizing the design of the emitter chips and their protection to ensure their maximum durability, as well as exploring new manufacturing processes in view of the eminent industrialization of the technology.

A sample of the good expectations that Ienai Space is arousing lately can be found in the award that was made to it of the “Aeronautical Innovation Award 2022” from the Official College of Aeronautical Engineers of Spain (COIAE) in the SME category in the sixth edition of these awards. The COIAE recognizes the company for its efficient satellite propulsion system.

The award went to Ienai Space for its installable ion propulsion system aboard small satellites that allows small satellites to change orbit, stay in orbit longer (thus extending their service life), perform anti-collision maneuvers, and re-enter the orbit. Earth’s atmosphere just at the end of its useful life (in order to comply with regulatory frameworks that seek to mitigate the growing problem of space debris).

The director of operations and co-founder of Ienai Space, Sara Correyero, also received another COIAE award in March 2022, that of “TALENT: [email protected] young man of the year 2022” (first edition), for his relevant professional career. This award recognizes the talent of those aeronautical engineers who, despite their youth, already have experience and notable projects in the professional or academic fields. (Sources: IMB / CSIC / CNM / UPM)