The small satellite market has been expanding rapidly over the past decade. CubeSats are no longer used solely for educational purposes but have evolved into a vital tool for Earth observation, telecommunications, scientific research, and commercial constellations. As the mission complexity grows, so do the requirements for propulsion systems.
Missions that use CubeSats previously relied on passive orbital lifetimes. However, today’s mission operators demand precise orbit maneuvering, station-keeping, collision avoidance, constellation phasing, and reliable end-of-life deorbiting. Thus, propulsion systems have to deliver controlled thrust with high efficiency. On top of that, it has to remain compatible in terms of mass, volume, and power constraints.
What Is Field-Emission Electric Propulsion (FEEP)
Field emission electric propulsion (FEEP) is an electrostatic propulsion method. An ion thruster, which uses liquid metal as a propellant. Usually, this type of thruster uses caesium, indium, or mercury.
Thrust is generated by electrostatic acceleration of metal ions. Ionization occurs due to liquid fuel: a strong electric field is created between the metal propellant and a special electrode. Under its influence, propellant particles become charged (they become ions).
The propellant is liquified only once, in space or during vacuum testing on Earth. Therefore, during assembly, integration, and launch, the FEEP system remains solid and inert. The propellant is supplied automatically: capillary forces and surface tension cause it to flow from the tank to the emitter without pumps or pressure. Even after the mission is complete, the system does not need to be additionally deactivated; it self-passivates.
Advantages of FEEP
The FEEP system simplifies assembly, testing, and launch. It is delivered fully assembled and fueled, with the tank and propellant already inside. No additional refueling is required at the satellite manufacturing facility or at the launch site.
There are no pressurized components in the system, and propellant is safe: it is non-toxic, non-reactive, and non-radioactive. This eliminates the need for complex safety measures, saving satellite manufacturers time and money.
Main advantages include:
- There are no high-pressure components in the design
- No additional safety procedures are required
- There is no refueling process before launch
- Safe materials are used, with no toxicity, reactivity, or radiation
- There are no special conditions for launch preparation
Limitations and Challenges of FEEP
Despite its many benefits, FEEP does have certain drawbacks.
- Low thrust. Ion thrusters generate low thrust levels, approximately at the micronewton level. Thus, it requires long burn times to achieve significant velocity changes.
- Erosion of the grid. Due to the impact of ions, the grids are influenced by erosion, which limits the lifetime of the thruster.
- System complexity. The system requires power supplies and complicated control systems.
FEEP vs. Alternative Propulsion Technologies for Small Satellites
Parameter | FEEP | Cold Gas | SteamJet Propulsion |
|---|---|---|---|
Thrust Level | Very Low | Low–Medium | Low–Medium |
Precision | Extremely High | Moderate | High |
Isp | Very High | Low | Moderate |
Power Consumption per Unit Thrust | Highest | Lowest | Low |
Propellant Safety | High (solid, non-toxic) | Lower (pressurized gas) | Highest |
Scalability | Limited | Good | Very Good |
Structural Complexity | Highest | Moderate | Lowest |
System size | Small | Largest | Smallest (0U) |
Cost | Highest | Lower | Low |
In conclusion, propulsion systems are critically important for small satellite missions. These systems enable orbital maneuvers, enhance operational flexibility, and significantly expand overall mission capabilities. In addition, propulsion extends mission lifetime by allowing station-keeping, collision avoidance, drag compensation, and controlled deorbiting at end-of-life..
Each mission has its own unique set of requirements. Different types of propulsion systems are designed to address specific needs. Field-Emission Electric Propulsion (FEEP) is well-suited for missions that demand excellent thrust control and minimal disturbance. According to NASA’s State-of-the-Art Small Spacecraft Technology report, FEEP systems are uniquely capable of delivering the fine thrust control required for complex maneuvers like station-keeping and drag compensation in Low Earth Orbit. At the same time, broader commercial and constellation missions may prioritize scalability, safety, ease of integration, and cost efficiency.
About SteamJet Space Systems
SteamJet Space Systems is a leading UK-based provider of high-performance satellite propulsion solutions. We specialise in water-based thrusters designed specifically for CubeSats and Small Satellites (SmallSats), with a strong focus on water-based thruster safety.
By pioneering the use of green propellants and intelligent thermal engineering, SteamJet enables complex LEO (Low Earth Orbit) manoeuvres — including orbital maintenance, collision avoidance, and de-orbiting — without the risks associated with toxic hydrazine or high-pressure cold gas systems, advancing green propulsion for space missions.
Steamjet Propulsion Technology
Our modular systems are engineered for seamless integration and maximum safety compliance:
Steam TunaCan Thruster: A compact, high-efficiency solution for 1U-3U CubeSats.
Steam Thruster One: Scalable propulsion for larger SmallSat constellations.
Discover how SteamJet’s sustainable space propulsion innovations are providing the safety and reliability required for the next generation of crewed and robotic missions. Contact our engineering team for technical specifications and ICDs.