IonDrop, our second payload is an electrospray thruster, a technology based on the acceleration of ions through an electric field.
The propellant is an ionic liquid confined in a porous glass tank, the liquid reaches by capillarity a nickel porous substrate which is in contact with the porous glass. This nickel part has a very thin porosity with a pore size that does not exceed 2 microns and is covered with micro emitters with a height of 100 micrometres that will be soaked with the ionic liquid.
At a distance of 300 microns, a grid drilled with micro-holes provides the magnetic field with the porous nickel emitters on the other side and lets the accelerated ions pass through the holes. This grid (250 microns in diameter and 150 microns in thickness) is one of the key parts for this thruster design because it initiates the thrust. Thus, an extremely precise manufacturing process is required to realize it.
Potomac Photonic is the partner of PolyOrbite that will make this payload possible by creating this part. The newly formed partnership between Photonic Potomac and PolyOrbite is a vary valuable one and, hopefully, it will help PolyOrbite in this and future challenges. The resulting thruster will provide a thrust of 50 micro-Newton, a really small amount on paper, but still sufficient to decelerate the satellite of 150 m/s over long periods (2 weeks or more).
Miniaturizing the electrospray thruster technology is of fundamental importance for nanosatellites because it will allow them to change their orbit and to increase the number of applications realizable with CubeSats. With an Isp of almost 3000s, these thrusters are really efficient and can perform many different tasks, from attitude control to interplanetary propulsion. The thruster design developed by PolyOrbite is specifically meant for CubeSat and it it small enough that four such thrusters can fit on one end of a small satellite.