KELLER Sensors in Space

On September 22, 2018, a Japanese H-IIB rocket was launched carrying the HTV supply vehicle with the ACLS module for the International Space Station. ACLS is designed for the recirculation and processing of CO2 into oxygen through electrolysis. KELLER developed and manufactured highly reliable absolute and differential pressure sensors for this module.

The International Space Station orbits the Earth at an altitude of about 400 km. Oxygen at this altitude is practically absent, so it must either be delivered from Earth or generated on site. Transporting oxygen to the station is an incredibly expensive process, with the cost of 1 kilogram of cargo to the ISS being about 33,000 euros. Considering the crew's expected oxygen consumption, the optimal solution is to recycle the CO2 exhaled by astronauts into breathable oxygen.

This is the purpose of the ACLS system, which was delivered to the American Destiny module (US laboratory) of the ISS on September 22, 2018. Airbus developed ACLS on behalf of the European Space Agency ESA. In the ACLS cycle, oxygen is generated thanks to the carbon dioxide exhaled by the crew.

CO2 is converted into methane and water using hydrogen obtained from the splitting of water molecules. Then, breathable oxygen is produced from water by electrolysis. According to Airbus, the system is designed for a crew of three astronauts and saves 450 kg of additional water load per year. At full capacity, ACLS extracts 3 kg of CO2, supplies 2.5 kg of oxygen, and produces 1.2 kg of water every day.

ACLS requires exclusively reliable components to ensure safe operation under space station conditions. The Swiss manufacturer KELLER AG from Winterthur won the contract to develop pressure measurement technology for the system. The project posed extreme challenges, as at an altitude of 400 km above the Earth's surface, components cannot be quickly replaced in case of failure. KELLER's contribution to this mission was the supply of high-precision absolute and differential pressure sensors operating in the range of 50 mbar ... 20 bar with an operating temperature of 0 ... 110 °C.

"Keller sensors operate flawlessly in various aerospace applications despite the most severe operating conditions. This once again proves that the reliability of Keller devices not only meets MTBF (mean time between failures) but sometimes even exceeds the requirements for the service life of sensors for such complex tasks," said Jürg Dobler, Managing Director of KELLER, after the project implementation.

"It goes without saying that our initial aerospace sensor projects are based not only on our many years of experience in aviation but, of course, also on equally extensive experience in general industrial applications. Moreover, the experience gained in aerospace projects will definitely be used in a wide range of KELLER pressure sensors available to any customer," commented Dr. Günther Kaden, aerospace sensor consultant. You can familiarize yourself with the range of devices mentioned by Dr. Kaden in our catalog. And you can choose the sensor suitable for your tasks with the help of our specialists.