Propulsion (PROP)

Also known as PROP, Micropropulsion, Thrusters

Changes or holds the orbit. Small satellites fly cold-gas, electrothermal, green monopropellant and electrospray thrusters; for PocketQubes, holding a low orbit needs micronewton thrust from a few tens of grams, a combination not yet demonstrated.

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SQ-SS-006
Updated
20 Oct 2026
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Definition#

A propulsion system expels mass to change the velocity, and therefore the orbit, of a spacecraft. In small satellites its main uses are holding altitude against drag, phasing the members of a constellation, formation flying, collision avoidance and lowering the orbit at the end of the mission. Dumping momentum from is a secondary job.

Technology families#

Cold-gas systems are simple, mature and safe, but their total impulse is modest. Electrothermal thrusters (resistojets) heat the propellant electrically to raise the specific impulse; some simple designs run straight from the spacecraft bus. Electrospray thrusters accelerate ionic liquids, or in FEEP thrusters low-melting metals such as indium and gallium, in an electric field and reach specific impulses of thousands of seconds. Propellant safety is one of the main reasons propulsion remains rare on low-cost CubeSats[1].

Flight examples#

  • MarCO (6U, 2018). Trajectory corrections on the way to Mars used eight cold-gas thrusters fed from one common tank of R-236fa, the compressed gas also used in fire extinguishers[2].
  • FEEP on a 3U. Enpulsion’s FEEP thruster flew on a Planet Flock 3p CubeSat in an orbit of about 491 × 510 km; flight data agreed well with the commanded thrust of about 220 µN[1].
  • Water . The ARM-A system of AuroraSat-1 provides 70 N·s of total impulse from 70 g of water through six resistojets[1], an effective specific impulse of about 100 s.

Propulsion and PocketQubes#

Propulsion is regarded as the main enabling technology for future PocketQubes, and the constraint is quantitative[3]. MEMS fabrication is the main route to fitting a thruster into 50 mm boards[4]. TU Delft developed two water-based micro-resistojet concepts, a vaporizing-liquid microthruster and a low-pressure microthruster[5], and allocated Delfi-PQ a propulsion payload with a wet mass below 75 g, a peak power of 4 W and an envelope of 42 × 42 × 30 mm[6].

At the smallest end, the open-source AIS-gPPT3-1C pulsed-plasma module (34 g, 40 × 38 × 24 mm) produced an impulse bit of about 0.65 µN·s, roughly 0.2 µN at 0.33 Hz, before development stopped because sub-joule pulsed-plasma thrusters could not deliver useful thrust[7]. AMSAT-EA’s GENESIS PocketQubes, meant to demonstrate a miniature pulsed-plasma thruster, were caught in both Firefly Alpha anomalies[3].

References

  1. [1]NASA Small Spacecraft Systems Virtual Institute. (2026). In-Space Propulsion. State-of-the-Art of Small Spacecraft Technology (2026 edition), Chapter 4. NASA Ames Research Center.nasa.gov(accessed 20 October 2026)
  2. [2]NASA Jet Propulsion Laboratory. (2018). InSight landing press kit: Mars Cube One (MarCO).jpl.nasa.gov
  3. [3]nadir lab. (2026). PocketQube picosatellites: A review of standards, mission trends and miniaturization constraints, with lessons learned from Grizu-263A, Türkiye’s first PocketQube [Preprint]. nadir lab.Read on nadir lab.
  4. [4]Silva, M. A. C., Guerrieri, D. C., Cervone, A., & Gill, E. (2018). A review of MEMS micropropulsion technologies for CubeSats and PocketQubes. Acta Astronautica, 143, 234–243.doi:10.1016/j.actaastro.2017.11.049
  5. [5]Cervone, A., Zandbergen, B., Guerrieri, D. C., De Athayde Costa e Silva, M., Krusharev, I., & van Zeijl, H. (2017). Green micro-resistojet research at Delft University of Technology: new options for Cubesat propulsion. CEAS Space Journal, 9, 111–125.doi:10.1007/s12567-016-0135-3
  6. [6]nadir lab. (2026). Materials engineering for PocketQube picosatellites: A scaling-based review and design guide [Preprint]. nadir lab.Read on nadir lab.
  7. [7]Applied Ion Systems. (2019). AIS-gPPT3-1C propulsion module: first integrated open-source thruster for PocketQubes. Libre Space Foundation community forum.community.libre.space(accessed 20 October 2026)
  8. [8]Wertz, J. R., Everett, D. F., & Puschell, J. J. (Eds.). (2011). Space Mission Engineering: The New SMAD. Microcosm Press.
  9. [9]Krejci, D., & Lozano, P. (2018). Space propulsion technology for small spacecraft. Proceedings of the IEEE, 106, 362–378.doi:10.1109/JPROC.2017.2778747
  10. [10]Lemmer, K. (2017). Propulsion for CubeSats. Acta Astronautica, 134, 231–243.doi:10.1016/j.actaastro.2017.01.048
  11. [11]The CubeSat Program, Cal Poly SLO. (2022). CubeSat Design Specification, Rev. 14.1 (CP-CDS-R14.1). California Polytechnic State University.nasa.gov

Cite this SatWiki entry

@misc{nadirlab2026propulsion,
  author       = {{nadir lab.}},
  title        = {{Propulsion (PROP)}},
  year         = {2026},
  month        = oct,
  howpublished = {nadir lab. SatWiki SQ-SS-006 (Rev. 3)},
  url          = {https://nadirlab.space/en/wiki/propulsion/}
}