Q1: Why are we developing this?
We are developing the HiperLoc EP thruster because we want to offer all small satellites the possibility of having the advantages of a propulsion system. Over the last decade, the number of nano- and microsatellites has grown extremely rapidly and today we see hundreds of these small satellites being launched every year. However, most of them have no propulsion capability at all and this limits their functionality. We want to change this by offering the small satellite community a propulsion solution that has high performance but at very low cost.
Q2: What is electrospray EP?
Electrospray electric propulsion (EP) sometimes referred to as colloid, is one type of EP wherein small charged droplets of propellant are released in order create thrust. The propellant is normally an extremely good electrical conductor. By releasing these small droplets into an electric field, the charged droplets are accelerated away from the thruster hence creating a counteracting force, this being the thrust created. The combination of a strong electric field and very small droplets makes this a very efficient thruster. In extreme cases the droplets are so small that they are merely single molecules (or since they are charged; molecular ions). This is often referred to as ionic mode and has the highest performance in terms of specific impulse. In this mode the thrust is low due to the small mass of each ion. Thrust may be increased at lower specific impulse by releasing charged fluid drops, or colloids in which case this is termed droplet mode.
Q3: What are the advantages of electrospray over other types of EP?
A principal advantage of electrospray is that it can be highly efficient. In terms of specific impulse, defined as thrust created per rate of propellant consumed (or in analogy with a car: miles per gallon). This is especially true running in ionic mode when the specific impulse can be around 2500 seconds which is better than many other EP technologies. In droplet mode the specific impulse is around 1000 seconds. Other advantages are scalability, manufacturability and cost. Electrospray is a technology that is easily scaled down in size without a loss in performance and thus is particularly suitable for the small satellite market we are targeting. By using established low cost manufacturing methods from other industries, we believe that our HiperLoc EP thruster will be low cost, again a feature that is attractive to the growing market of micro- and nanosatellites wherein low cost is essential.
Q4: What are the high level goals of the project?
The two most important goals of the project are:
- To prove the performance of our electrospray thruster in our laboratories.
- To demonstrate that we can manufacture the thruster with established and well-known materials and processes so that we can produce this product at a low cost.
In other words, and using the Technology Readiness Level scale, our goal is to reach TRL-4. We do also have a plan for how to mature and develop this concept after this project, beyond TRL-4 (Target: 250 m/s deltaV, for a 1/2 U propulsion system on a 3U CubeSat).