NASA’s Four Bed Carbon Dioxide Scrubber (4BCO2) is planned for installation on the International Space Station (ISS) after rigorous ground testing. The next-generation CO2 removal system incorporates a high-speed in-line blower and dual controller from Calnetix Technologies.
The blower assembly includes a compact in-line blower on magnetic bearings (Momentum™) and an integrated hybrid dual controller (Continuum™) to drive the blower. The magnetically levitated in-line blower is an integral component of the CO2 removal system and will drive the airflow through the entire system in a microgravity space environment.
Momentum features an overhung permanent magnet motor; a centrally located, five-axis, active magnetic bearing (AMB) system; backup bearings; and an overhung centrifugal impeller in a compact package. Magnetic bearings were used instead of conventional bearings due to their low transmitted vibration, high-speed levitation, low power consumption, high reliability, oil-free operation, and tolerance to particle contaminants in the air stream.
Continuum consists of an AMB controller and a variable speed drive (VSD) motor controller in a single compact package that supports speeds up to 60,000 RPM with long-term maintenance-free operation. The AMBs were utilized to eliminate lubrication and rotating drag losses, which was an important aspect in meeting NASA’s stringent outgassing requirements.
To meet the application needs, the in-line blower system must survive launch vibrations and acceleration requirements, comply with electromechanical and power quality requirements under NASA SSP 57000, have a shelf life of 15 years, operate 30,000 hours without requiring maintenance, and operate with very low conductive and convection cooling availability. In addition, bearings cannot introduce contaminants, such as lubricants or grease, into the airstream. The blower must tolerate the ingestion of particles, such as particles liberated from the filter media and dust in the cabin air, without incurring damage.
The main design challenge was to fit the new magnetic bearing blower into the same space as the foil bearing-supported heritage blower, which is currently being used on the ISS. The AMB system with position sensors and backup bearings had to be miniaturized to fit into a highly constrained space. To create a compact design, the bearing system was centrally placed to be used with a centrifugal impeller positioned at the air inlet and an overhung permanent magnet motor at the outlet side of the machine. The air flows through an annular passage around the internal components.
Upon successful use of the magnetic bearing blower on the ISS, magnetic bearings could also be used in other aerospace applications such as fluid pumps, reaction wheels, and gyroscopes that challenge conventional bearing technologies.