Space is a hostile environment, where materials need to withstand harsh conditions for years or even decades. This is an ongoing challenge as atomic oxygen in low Earth orbit as well as cosmic radiation have a devastating effect on the materials that are used in satellites, which include construction details, subsystems and nanomaterials used in electronics. Damaged materials can cause the satellite to malfunction, turn it into uncontrollable space debris and endanger other satellites. Global problems like these can only be solved by efficient collaboration between the private and public sector. A fine example of such collaboration is the pilot project for testing future materials in space that will be carried out on the satellite ESTCube-2. In this project, the deep tech company Captain Corrosion and the Laboratory of Thin Film Technology of the University of Tartu have joined forces to usher in a new era in materials science and the exploration of space.
The next generation satellite module “Enterprise”
The pilot project for testing future materials will be carried out by using an innovative compact satellite module that is compatible with most board computers. Currently there are already different models of this satellite module and the model used on ESTCube-2 is called “Enterprise”, which has a size of 41 x 65 mm and allows to test up to 15 material samples, simultaneously, in space. For testing, the materials are applied on the sensor areas of the module, which is then covered with a panel that has gates in strategic positions. These gates allow atomic oxygen to interact with the studied materials in addressable detector sites, inducing signals which can be detected by the board computer. The detection is done by dialing the appropriate gate on the module and performing the measurement either automatically at predetermined time intervals or manually. For instance, the data can be gathered once per second during the whole mission or, alternatively, manually once per month/per mission/per second, depending on the nature of the experiment. This allows the module to work offline most of the time and operate with a low power consumption.
Photo of the satellite module „Enterprise“, that is used for studying the behavior of materials in space on ESTCube-2. Photo: Maido Merisalu
High performance nanostructured coating for aerospace industries
One of the materials tested on the satellite module is a novel nanostructured coating that has been developed for high precision aluminum alloy parts used in aerospace applications. The nanostructured coating is prepared in two stages. First, the aluminum components are treated electrochemically, which results in a porous anodic aluminum oxide (AAO) layer. In the second stage, the aforementioned pores are sealed by atomic layer deposition (ALD) with a ceramic material. Thorough corrosion tests performed at the University of Tartu as well as at the European Space agency have shown that the coating provides excellent protection against corrosion in both terrestrial and space applications. The coating has also been made sufficiently conductive to mitigate the issues caused by charging due to cosmic radiation. Furthermore, the coating is ceramic by nature and well adhered to the substrate, which gives it enhanced wear resistance. The latter is particularly important for preventing cold welding in space, which causes mobile parts to get stuck, i.e., adhere, hampering movements. Nanostructured coatings are already being adopted in the space industry as functional parts of several satellites due to distinct advantages over several existing technological solutions.
The preparation of the nanostructured coating for aerospace applications such as communication satellites. Figure: Maido Merisalu
Future material graphene and nanofilms for electronics
The heart of a satellite is its board computer that controls its subsystems. All of these systems, including the board computer itself, contain nanomaterials, which include semiconductors, dielectrics and conductors that are all endangered by atomic oxygen and ionizing radiation in space. Therefore, it is important to know the mechanism behind the deterioration of the critical properties of the aforementioned materials, ultimately leading to the malfunction of the devices. However, the behavior of nanomaterials in space is not yet thoroughly studied and this is particularly problematic for modern and next generation electronic devices, which should be more powerful and compact than previous models.
The development of novel nanomaterials for the electronics industry has been conducted for decades in the Laboratory of Thin Film Technology of the Institute of Physics of the University of Tartu. In these studies, materials scientists utilize modern nanotechnologies and state of the art scientific instruments to look at atomic layers and arrange them into new types of materials with desired composition and structure. This opened up an opportunity for the materials scientists of the Laboratory of Thin Film Technology to participate as an external partner in the pilot project for testing future materials in space. In the pilot project, partners investigating materials of interest were searched in an open call from the public and private sector to give them an opportunity to bring their research literally onto a whole new level – the space.
In order to learn how the module works, the materials scientists were provided with commercial, one atomic layer thick material, graphene, which was already known to be compatible with the module. The materials scientists already possessed expertise in handling graphene, which made the learning process fast and allowed them to proceed, applying their own innovative materials in the module. The most interesting candidates were thin films of conductive materials that were developed at the University of Tartu. The thickness of these conductive films was comparable to the diameter of a SARS-CoV-2 virus particle. By the time of publishing this article, the module with nanomaterials has already been delivered to the team of ESTCube-2, who integrate the module onto the satellite.
Illustration of the one atom thick future material graphene, which will be studied on the Enterprise module. Illustration: Maido Merisalu
Back to the Future
So, what does the future have in store for us? By now it is already clear that the mutually beneficial collaboration between the public and private sector drives the rapid development of new materials and their practical adoption in the aerospace industries. This will make the next generation satellites sturdier, more compact and weigh less, while mitigating the space debris issue and enabling the population of new orbits that pass through Van Allen belts or are below 200 km. The future is bright and it is already being assembled by materials scientists, atom by atom.
Photo of satellite swarm prototypes that are based on future materials. Photo: Maido Merisalu