Floating ball with propeller drive

The various movements of the mission companion are controlled by switching individual propellers on and off and by the speed of the respective drive motors. © Airbus Space

On board the ISS, the medicine ball-sized assistant floats weightlessly in space despite its mass of five kilograms. To enable it to move purposefully without bumping into anything, it is equipped with seven tubular air nozzles, each containing two small propellers. They also allow him to interact using body language. "Four tubes are aligned in the x-axis and are responsible for moving forwards and backwards, where we need the highest speed," explains Philipp Schulien, Science Engineer at Airbus in Friedrichshafen. "With appropriate control of the individual propellers, they also give the mission companion the ability to nod or 'shake its head'. Two tubes are designed for lateral movement, one for up and down. This arrangement - instead of one larger propeller per axis - was chosen partly because of the strict noise protection regulations of the ISS."

When the little helper is working with a crew member, it is supposed to stay in a "box", an imaginary cuboid in the station's airspace. In order to stay in place, however, CIMON has to make some effort, as its permitted area also moves in circles due to the constant rotation of the ISS. In addition, the air on board is constantly being circulated. The prevailing airflow and the rotation would quickly push it against the next side of the ship without any resistance. The propellers in its air nozzles therefore regularly provide small thrust pulses to correct its position.

Holding the position with servomotors

The compact brushless DC servomotors are just 24.1 mm long with a diameter of 8 mm and deliver a torque of 1.1 mNm. © Faulhaber

The various movements of the mission companion are controlled by switching individual propellers on and off and by the speed of the respective drive motors. The latter are brushless servomotors from the 0824...B series from the portfolio of drive specialist Faulhaber. The SC1801 speed controller from the same manufacturer translates the commands from the navigation software and regulates the speed accordingly. Philipp Schulien cites several reasons for this choice: "Faulhaber motors have already proven themselves in space travel. Since every gram and every cubic centimeter counts when it comes to space travel, we always need as much drive power as possible with as little weight and volume as possible. The chosen combination is extremely compact. Absolute reliability, durability and freedom from maintenance are just as important. Last but not least, the drives should also consume as little energy as possible and be very quiet so as not to cause additional noise for the crew." For the same reasons, other Faulhaber motors have also flown to the ISS: they drive the peristaltic pumps for a bio-experiment that is also being carried out during the Horizons mission.

The astronaut assistant remained on board after the mission was completed and continued his own training. His feedback is intended to help the developers on Earth to perfect the concept. After the trial and learning phase, he should be able to suggest solutions to technical problems. For example, it could guide repair work by announcing the necessary steps and pointing a laser pointer at screws that need to be loosened. It is also planned that one day it will be able to independently monitor the functions or status of on-board equipment and act as an early warning system in the event of difficulties. With such capabilities, the assistant could then take on important tasks during long-term missions to the moon or Mars, for example. As "Project CIMON" can also smile and tell jokes, terrestrial versions of the little helper are also planned for the future, for example to work in hospitals or in the social sector.

Dipl.-Ing. (BA) Andreas Seegen, Head of Marketing at Faulhaber, and Ellen-Christine Reiff, M.A., Redaktionsbüro Stutensee / am