The primary objectives for project IFM Nano are:
- The adaptation of an established FEEP (field emission electric propulsion) ion thruster design for use on micro and nano satellites (particularly CubeSats). Such spacecraft could use the thruster either for continuous drag compensation in LEO or even as an efficient main drive.
- A full characterization and test campaign including functional and environmental tests to verify the design’s specifications and its fitness to operate reliably in orbit.
- The IFM Nano Thruster shall be able to survive typical loads expected during ground handling and LEOP. In particular long and thin ‘needle’-like structures could be venerable to such loads.
- In the present design, only COTS components are used for thermal sensors and electronics. The radiation hardness of these components is not known. The thruster shall be able to operate, however, for at least a couple of years in a radiation environment typically expected in LEO.
- The functionality of the neutralization concept is based on extensive simulation of the electric fields, but no experimental verification has been conducted so far. Also the lifetime as well as lifetime limiting factors are currently not known.
- The plasma plume shape partly determines the thruster efficiency. Any plume divergence shall be minimised as much as possible. At present, the shape if the plume as well as its characteristics are unknown.
The IFM Nano Thruster addresses the urgent need of a propulsion system for micro- and nano-satellites: its wide range of thrust (1μN to 1mN), the excellent throttlability, and a high specific impulse (up to 5000 s), allow to significantly increase the mission range of such satellites in low orbits. The high Isp on the other hand allows for very high delta-v manoeuvres at a high propellant mass utilization efficiency (80%). The modularity and the small volume (less than 1 dm³ including propellant and electronics) and its light mass (0.8 kg), make the thruster suitable for all small satellites from 1 to 500 kg. The combination of high Isp with medium very well controllable thrust levels in a small and light package makes the IFM Nano thruster a strong competitor for existing colloid, cold gas, or Hall effect thrusters.
- Design based on a decade-long ESA-approved evolution and development process.
- Thrust level 1 µN — 1 mN at Isp up to 5000 s, capacity of 10kNs and a power to thrust ratio of <80 W/mN.
- Monolithic outer structure in a 10x10x10 cm³ package weighting less than 1 kg, including electronics, tank, and thruster.
- Power interfaces 3.3V and 12V, control via I2C or UART
- No moving parts, all-solid in OFF state (during launch)
- Fully tested according to relevant ESCC standards
- COTS components tested for radiation and thermal compliance
Mechanically, the thruster comprises a tank filled with the metal propellant and rigidly connected to the crown emitter. The extractor anode, which is part of the top plate, is separated via an isolator from the electronics compartment and the tank. An optional housing encloses all parts but is not required for mechanical stability.
Electrically, the thruster is commanded via the spacecraft bus via I2C or UART. The central command and control module is connected to the independent power supplies for the heater, the two cathodes (two separate supplies), the emitter, and the extractor.
The project starts with a PDR after which two engineering models are manufactured. Both engineering models are subjected to environmental tests including shock and vibration tests, thermal vacuum tests and performance tests. Three dedicated test campaigns are initiated:
- a test campaign for cathodes is performed to investigate failure mechanism as well as to select the most suitable cathode for our application
- the PPU subjected to low dose as well as high dose radiation tests to determine how much radiation the PPU equipped with COTS components can survive and to identify components most vulnerable to radiation
- a plume diagnostics system is designed and used to characterise the plume of the IFM Nano Thruster.
The project is finished. All the work as outlined in the project plan is performed. Meanwhile, a successful in-orbit demonstration of the IFM Nano Thruster has taken place. A spin-off company was founded (Enpulsion GmbH) that commercially sells the thruster. Several thruster are currently flying in space. Derivatives of the IFM Nano Thruster are currently under development in a joint effort between FOTEC and Enpulsion.