6S CubeSat: an Italian satellite designed by PoliMi students

Hands-on experience is crucial in the formation of an engineer, and aerospace ones are no exception. Fulfilling this need is the aim of the student organization PoliSpace, founded in September 2020 at the Politecnico di Milano. One of the projects it is carrying out is the design, development, and construction of the 6S CubeSat.

6S is an acronym that stands for Student-made Single unit Satellite for Solar cells and Structural battery in-Space testing. As the name suggests, the mission of the CubeSat is to perform in-space testing of two promising technologies: Perovskite solar cells and structural batteries. To do so, two payloads will be carried on board: PESCA and a Volta-made structural battery mock-up.

A mockup of PoliSpace's 6S CubeSat. Two Perovskite solar cells are visible on one side. Credits: PoliSpace — *A mockup of PoliSpace’s 6S CubeSat. Two Perovskite solar cells are visible on one side. Credits: PoliSpace*

PESCA

A Perovskite is any material that follows the same crystal structure as calcium titanium oxide, the first compound to have gone by that name. One promising application for Perovskites is the production of lighter solar cells at contained costs. Unfortunately, Earth-bound applications have been held back by their tendency to degrade due to contact with oxygen and moisture. This problem is clearly not present in space, where their advantages may finally become game-changing.

To test this emerging technology, 6S will carry into space eight different samples of Perovskite solar cells, supplied by the universities of Cambridge and Potsdam. Once there, their performance will be evaluated by PESCA. The PErovskite Solar Cells Analyzer is a testing circuit that will read many parameters. The most important are the open circuit voltage, the short-circuit voltage, and the current-voltage curve (IV curve). These will allow for the individuation of the cells’ maximum power production.

On the left a pair of Perovskite solar cells, on the right the PESCA circuit that will test their performance in space. Credits: PoliSpace — *On the left, a pair of Perovskite solar cells, and on the right, the PESCA circuit that will test their performance in space. Credits: PoliSpace*

Over time, PESCA will measure the response of the cells to various sunlight inclinations and their degradation due to the environment of space. In particular, it has been theorized that Perovskite solar cells may possess radiation self-healing properties. This would make them even more attractive for spaceflight applications. This makes 6S’ mission even more groundbreaking.

Volta

So far, all electricity storage solutions have been entirely dedicated to that single purpose. Structural batteries challenge this concept. By using materials that also have good structural properties, the battery can double as a structural component. The potential advantages are many: mass and volume reduction, and greater ease of integration into a vehicle. All of these qualities are of the utmost importance in the aerospace sector.

The start-up Volta Structural Energy aims at developing and marketing such technology, using aluminum-ion battery chemistry. This choice provides to add durability and fire protection benefits to the mass and volume savings of the structural battery architecture.

To test the structural properties of this product, 6S will carry a mock-up of one such battery attached to a face. This will allow testing of the structural properties in the space environment, thus evaluating the response to temperature and radiation. The data will be precious for Volta engineers to improve their designs.

The Volta structural battery that will fly in space on PoliSpace's 6S CubeSat. Credits: PoliSpace — *The Volta structural battery that will fly in space on PoliSpace’s 6S CubeSat. Credits: PoliSpace*

Orbit

It is rare, and expensive, for CubeSats to fly on dedicated missions. As such, 6S will likely hitch a ride on the launch of a bigger payload or many other small satellites. For this reason, there was no precise choice of orbital parameters and instead, a range was assessed. It has been established that a high-inclination orbit would be the best choice for the mission since the CubeSat uses the Earth’s magnetic field for stabilization, and a high inclination would guarantee optimal control. Such an orbit would also ensure contact with a ground station in Scotland.

The possible final altitude ranges between 450 and 565 km. The orbital parameters are chosen so that atmospheric drag ensures reentry within 25 years. This, of course, is to avoid the creation of space debris in the long run. Safe disposal of the satellite at the end of its life should always be practiced, to avoid worsening the problem.

*6S CubeSat team members at the International Astronautical Conference, held in Paris in 2022. Credits: PoliSpace*

Schedule

One of the first major milestones for the program was the completion of Phase 0 in December 2021. During this phase, the feasibility of launching various payloads was assessed. This led, during Phase A, to the final selection of the two payloads that will actually fly. At this stage, the preliminary design of the satellite was also laid out. With the completion of Phase A in June 2022, the design teams seamlessly transitioned into Phase B, which is still ongoing.

This means that CubeSat is currently in the detailed design stage. PoliSpace will not be alone in this endeavor though. In December 2022, the association was selected by the “Fly your satellite! Design Booster” program. This is an ESA initiative to help students with their space-related projects. PoliSpace was selected after a careful evaluation of the candidates, who all defended their design proposals. This selection means that in the next eighteen months, PoliSpace students will work with professionals to improve and finalize the design of the satellite. This will only add to the learning opportunities which the development of 6S has already provided the students with.