Electric Propulsion in Space
Boron Nitride-based ceramics are being designed into more diverse and complex ion thruster applications than ever. Hall Effect Thrusters are rapidly incorporating Boron Nitride grades into the discharge channel, where the magic happens. Specifically, M26 Boron Nitride, HP Boron Nitride, and Shapal Hi-M Soft (an aluminum nitride / boron nitride composite).
Why are ion thruster designs settling on Boron Nitride-based ceramics for Low Earth Orbit (LEO), Geostationary Orbit (GEO), Deep Space Exploration satellites, swarms and constellations?
It’s the unique combination of properties that makes Boron Nitride so critical.
- Lower density than the alternatives like alumina. Shapal is approx. 2.7, followed by M26 2.0 and HP’s 1.95.
- Easily machined into the increasingly complex designs needed to optimize the electromagnetic fields involved. This is even more important in the design stage, for the evolving iterations.
- It’s scalable. HP and M26 are hot-pressed in billets of 490mm x 490mm x 400mm. Shapal Hi-M Soft is hot-pressed in billets up to 300 x 300 x 84mm.
- Boron Nitride has a relatively low “sputtering yield”, giving it a longer life when compared to other materials. This is design-dependent, and is the focus of much design effort to minimize further.
- Some Boron Nitride grades have lower outgassing rates. Shapal Hi-M Soft is the best, being near-density, M26 with the silica binder is next, followed by HP.
- Some grades are harder than others, with Shapal the hardest, followed by M26, and then HP. But all are still machinable.
- Moisture resistance is an ongoing concern in this application. Shapal’s near-zero porosity is best, followed by M26 and its silica binder, with HP requiring some post-machining protection to prevent moisture pickup.
- Boron Nitride dielectric properties are uniformly good, with a dielectric strength of >40 KV/mm. M26 and HP also have a relatively low dielectric constant k of approx. 4
It is this combination of properties that enables Boron Nitride grades to excel in the increasingly demanding Ion Thruster applications in this rapidly growing market!
Contact Precision Ceramics USA to help you work through the available options.