FEEP Technology

Field Emission Electric Propulsion

Best in propulsion

Field Emission Electric Propulsion (FEEP) produces thrust by ions and an applied electrostatic field. By changing the field’s parameters, thrust and specific impulse can be varied as required. In a FEEP thruster, the metal propellant is liquified in orbit, and a strong electrostatic field extracts, ionizes and accelerates the propellant from the ion emitter.

FEEP. Means. Easy and Safe.

The ion emission is supplemented by electron emission from neutralizers to maintain charge stability of the spacecraft. Emitted propellant is replaced in a fully passive manner by capillary forces which maintain propellant supply from the propellant reservoir up to the emitter tips, relying on surface tension of the propellant itself. A FEEP thruster therefore does not require any external forces like pressurization or pumps. Since propellant liquification is only done once in space and for ground vacuum testing, the FEEP system is fully solid and inert during ground handling, integration, and launch.

ENPULSION holds a worldwide exclusive perpetual license to commercialize 30 years of know-how and IPs related to the electric propulsion technology.

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Flight Heritage

The ENPULSION NANO Thruster (formerly named ‘IFM Nano’) had its first successful In-Orbit-Demonstration with independently confirmed orbit changes in January 2018. Since then, it has been successfully tested in orbit on multiple customer spacecraft.

Mature Technology

The FEEP technology was developed under ESA contracts for > 15 years. 1 000 + emitters have been tested and an ongoing lifetime test has demonstrated > 30 000 hours of firing without degradation of emitter performance.

Controllable Specific Impulse up to 6,000 s

Due to the efficient process in which up to 60% of the evaporated indium atoms can be ionized, our emitters can provide a very high specific impulse and can accurately control the ISP anywhere from 1 000s to 6 000s.

Debris Safety

Even when active, no part of the thruster is pressurized, and no chemical energy is stored. This means that no explosive reaction can harm the spacecraft system and create additional debris in case of collision.

no propellant containment Issues during launch

Our technology has no moving parts, and the propellant is in solid state during launch. The lack of pressurized tanks and gaseous, liquid, and reactive propellants avoids any risks of propellant containment during launch.

Compact Building Blocks

Our Thruster modules can be used as compact pre-qualified building block in order to provide custom solutions at a commodity price and ultra-short lead times. A whole cluster can be operated as a single plug-and-play unit.

Instantaneous Thrust

FEEP emission is an electrostatic process from a Taylor cone with a ms response time. FEEP Thrusters can enter a hot-standby mode where propellant stays liquified. Response time is then only limited by electronics control.

Dynamic precise thrust Control

Thrust can be controlled through the electrode voltages, providing excellent controllability over the full thrust range down to a precision of a few µN, as well as low thrust noise.

Safe Propellant

Our emitters use indium, a non-toxic, non-reactive and non-radioactive metal as propellant, with negligible evaporation even in vacuum at high temperature.

fast integration & Simple handling

The FEEP thruster technology is an entirely passive system using no hazardous materials and an unpressurized solid propellant during all process stages. Thrusters are delivered in a ready-to-fly state and are designed for simple and fast integration.

Indium – solid metal propellant

Indium, 49In in the periodic table, is used as propellant in our thrusters. It is a very soft, lustrous white metal which was discovered by Ferdinand Reich et al. in 1863. Its name comes from Greek indikón, Latin indicum, as it means indigo blue.

Advantages of indium

  • It is compact due to its higher density — The graph above presents a comparison of tank sizes between the ENPULSION MICRO R³ and a Hall-Effect thruster (operating at 1 200 s ISP @ 100 w) of same total impulse using different propellants.
  • Thrusters are shipped full — Propulsion systems using other propellants usually have to be shipped empty and filled at the launch facility, introducing additional expenses and procedures.
  • It is safe — Indium is non-toxic and easier to handle than other propellants. It is stored unpressurized and, unlike high pressure tanks, it does not need special authorizations (launch waivers) to be launched as secondary payloads, and is RoHS and REACH compliant.
  • It is readily available — Indium is currently a by-product of zinc refining and benefits from industrial scale production. Since peaking at $700 / kg in 2007 indium prices have stayed below $400 / kg.

FEEP technology for a wide range of missions and spacecraft

ENPULSION FEEP Propulsion Systems have been used successfully for:

  • Constellation deployment
  • Station keeping
  • Orbit raising
  • Orbit phasing and Ground Track Improvement
  • Formation Flight
  • Collision avoidance
  • Drag Compensation
  • Small GEO Demo Missions
  • Commercial BIU Missions
  • VLEO Missions
  • Several units in space are foreseen to perform de-orbit maneuvers once the first operational missions are over

FMs have also been delivered (but not yet launched) for:

  • SmallSat exploration of the solar system

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Thruster Framework Download

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    Felix is what you call a global citizen. He grew up on 3 different continents and has called Buenos Aires, Chicago, Brussels as well as Athens his home. Naturally, Felix is also passionate about travelling and especially enjoys all kinds of water sports. For example, you can regularly catch him stand up paddleboarding in the early morning. Prior to joining ENPULSION Felix worked in Business & Strategy Consulting in Austria’s largest Banking Group and thus brings more than 5 years of experience in the Financial and Banking sector to the Management team. Besides, Felix’s future-oriented, clear-sighted approach to planning allows ENPULSION to tackle new challenges well-prepared.

    CEO & Founder

    Alexander Reissner started his career in the space business with RUAG Space, working in Thermal Hardware and later in Mechanical Engineering on projects like Sentinel or Bepi Colombo. He then joined the Austrian Institute of Technology and became the Team Leader for Electric Propulsion Systems. In 2013, he became the head of the Department of Aerospace Engineering shortly after it was moved to FOTEC. After growing this department from 5 to 17 scientists and engineers, he realized the potential of the FEEP technology in the SmallSat market and founded ENPULSION. His education took him from a Dipl.Ing. (MSc) in Physics at the Technical University of Vienna to the Korean Advanced Institute of Science and Technology (KAIST) in South Korea where he started a PhD program in Aerospace Engineering. He then followed his supervisor to the Technical University of Dresden where he finished his PhD Program. Alexander Reissner was also appointed to be the General Chair of the International Electric Propulsion Conference (IEPC) in 2019, which took place in Vienna.

    CHRO & Co-Founder

    Thomas likes to make sure everything works smoothly, efficiently and he is always ready to solve a problem. He has a master’s degree in political science as well as specialized higher education in international business communications. He is additionally an ISO/IEC certified trainer and safety chancellor. Thomas brings to ENPULSION over ten years of work experience in project and general operations management. He has previously worked at the University of Vienna, the Vienna Chamber of Labor, and most recently at Casinos Austria, a worldwide, leading player in the global gaming industry. When he is not helping ENPULSION to thrive and reach its fullest potential, Thomas enjoys traveling, strolling through his home town Vienna, and grilling the perfect steak on his terrace!


    David is a Research Associate at MIT (Massachusetts Institute of Technology) and avid traveller. He received his M.S. in applied physics in 2008, and Ph.D. in mechanical engineering in 2012 from Vienna University of Technology, Austria, and a M.A. in political science in 2012 from University of Vienna. Before joining ENPULSION, he was Research Scientist in the Department of Aeronautics and Astronautics working on the design and characterization of micromachined ionic liquid electrospray thrusters, which include multiple flight experiments. Before joining MIT's Space Propulsion Laboratory, he embarked on trip across the world, writing post-doc grant proposals along the way; secretly it was for beaches and sun. Aside from some teaching, he was previously working on the development of various types of electric and chemical propulsion systems. He worked on chemical green bi-propellant thrusters for small satellites and pulsed plasma thrusters for CubeSats at FOTEC and the Austrian Institute of Technology.

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