Deep Space Propulsion
The figure above shows the flow of water in and around the chamber. Cool water is injected directly into the path of the concentrated sunlight on top of the chamber, quickly heating it into a gas which forces its way out, creating thrust. As an additional measure to conserve heat, water is pumped along the sides of the chamber to collect the otherwise wasted heat.
In order to use the water mined from asteroids as propellant, TransAstra has created the Omnivore™ Thruster. The Omnivore thruster is a breakthrough in water-based propulsion that eliminates the need for highly processed and/or dangerous propellants, making it attractive for in-space cargo transport applications.
The Omnivore Thruster is projected to operate in a vacuum at 360 Isp (exhaust velocity), meaning that it uses propellant at an extremely efficient rate. This high Isp is achieved by using the sun to reach temperatures near 3000 K, causing the water to vaporize and leave the chamber at high speed. A high efficiency means that costs will be lower and spacecraft more capable.
The ceramic foam inserts are a porous network of bubbles, which allow water and gas to flow through to the exhaust. Additionally, the ceramic foam is able to absorb heat upwards of 3000 K while maintaining its shape. Finally and most importantly, ceramic foam has a high thermal conductivity, meaning that it can quickly transfer the heat from the sun into the incoming water.