With the rapid development and large-scale deployment of microsatellite technologies, plasma thrusters—known for their high efficiency, low propellant consumption, and lightweight system design—have gradually become a core technology for precise orbit control and sustainable satellite operations, replacing conventional chemical propulsion systems in many microsatellite applications. With support from the National Science and Technology Council, Distinguished Professor Yueh-Heng Li of the Department of Aeronautics and Astronautics at National Cheng Kung University has led the ZAP LAB research team in building upon prototype technologies of the Vacuum Cathode Arc Thruster (VCAT) and the Pulsed Plasma Thruster (PPT). The team successfully developed the Vacuum Arc Induced Pulsed Plasma Thruster (VAI-PPT) and further upgraded and opti-mized the ignition stability and overall system performance of the VCAT.
Since 2014, the team has devoted itself to research on plasma propulsion technology and has established a variety of plasma thrusters and propulsion sys-tems for satellite applications. A plasma thruster uses electrical energy to convert matter into plasma—charged particles—which is then expelled at high speed to generate thrust and propel a satellite forward through reaction force. The VCAT developed by the team uses solid metal as its propellant and does not require high-pressure fuel tanks like conventional rockets, making it lighter, smaller, and safer. These advantages make it particularly suitable for CubeSats with limited volume. Weighing less than 1 kilogram and occupying only about a 10-centimeter cube, or 1U, the VCAT consumes less than 5 watts of power while en-abling orbit maintenance and attitude control in space.
One of the major challenges of VCAT is that prolonged operation may lead to failure due to unstable discharge. To address this issue, the team proposed a multi-layer insulation design, replacing the conventional single insulation layer and surface graphite layer with a sandwich structure composed of alternating in-sulation and graphite layers. This design significantly improves thruster stability, increasing the number of discharge cycles from approximately 1,000 to more than 400,000 and greatly extending the operational lifetime of the thruster.
The team has completed more than 400,000 ground-test firing cycles and has also passed space-environment tests, including vibration, thermal vacuum cy-cling, and electromagnetic interference testing. The technology has reached Tech-nology Readiness Level 7 (TRL 7), indicating that it is approaching readiness for practical space applications. Following the successful completion of preliminary in-orbit flight verification in 2025, this achievement also demonstrates that Tai-wan now possesses independent technical capability in microsatellite electric pro-pulsion.
In addition to the VCAT, the team has continued developing another type of thruster: the Pulsed Plasma Thruster (PPT). This type of propulsion system uses an igniter to trigger an instantaneous high-voltage discharge between electrodes, vaporizing and ionizing the surface of a Teflon propellant into high-temperature plasma. The plasma is then expelled at high speed to generate small amounts of thrust, making PPTs highly suitable for precise satellite attitude control. However, conventional PPTs have long faced a major issue: the igniter tends to fail over time due to carbon deposition, similar to fouling in a motorcycle spark plug. To solve this problem, the team proposed the Vacuum Arc Induced Pulsed Plasma Thruster (VAI-PPT), which replaces the conventional igniter with a vacuum arc, greatly improving long-term operational stability. Related technologies have been patented in Taiwan, Japan, and the United States.
More importantly, the team successfully reduced the operating voltage of the thruster from as high as 2,000 volts to 300 volts. This not only reduces electro-magnetic interference and minimizes the impact on satellite electronic systems, but also improves propulsion efficiency to more than three times that of conven-tional systems. In addition, the thrust level can be adjusted according to different mission requirements. In low-thrust mode, the system can perform satellite atti-tude control and orbit maintenance; in high-thrust mode, it can support missions such as space debris avoidance or satellite deorbiting for atmospheric reentry and burn-up. This provides microsatellites with significantly greater mission flexibil-ity.
Beyond small-satellite thrusters, the team is also developing space propul-sion systems suitable for medium and large satellites, including RF ion thrusters, Hall thrusters, and cusp field thrusters, all of which have achieved important pro-gress. Looking ahead, the ZAP LAB team will continue applying plasma propul-sion technologies to satellite orbit maintenance, space debris mitigation, multi-satellite formation flying, deep-space exploration, and low-Earth-orbit satellite communications. The team will also continue improving thruster performance and conducting in-orbit flight verification, gradually building Taiwan’s inde-pendent space propulsion technology and industrial capacity, while helping Tai-wan secure a significant position in the global development of space technology.
Media Contact：
Yi-Chun Lin
Program Manager/Assistant Research Fellow
Department of Engineering and Technologies
National Science and Technology Council
Tel: +886(2) 2737-7529
E-mail: yclin@nstc.gov.tw
