1. The drive that defines the ship

James S. A. Corey’s The Expanse returns as the recalled work because every ship in that universe is limited by its drive: how much delta-v it carries, how fast it can burn, and what happens when the propellant runs low. A small satellite is the same. The propulsion system determines not just where it can go but how long it can stay there.

This entry reads about propulsion technologies for small satellites.

2. The propulsion landscape

A NASA Small Spacecraft Systems Virtual Institute overview and a Technology Area Roadmap describe the main categories:

  • Chemical propulsion: high thrust, lower specific impulse, useful for rapid maneuvers and attitude control.
  • Electric propulsion: low thrust, high specific impulse, useful for orbit maintenance and efficient delta-v.
  • Cold gas: very low thrust, simple, useful for precise attitude control and small maneuvers.
  • Solar sail and other propellantless options: continuous low thrust from photon pressure, but limited pointing and control authority.

An MDPI review of CubeSat propulsion technologies surveys what has actually flown and what remains experimental.

3. The thrust-specific impulse trade-off

The fundamental trade is between thrust and efficiency. High thrust lets a spacecraft complete a maneuver quickly but consumes more propellant for a given delta-v. High specific impulse uses propellant efficiently but produces low thrust, so maneuvers take longer and may require more power.

For a LEO desktop this matters because:

  • Drag makeup and stationkeeping can be done slowly with electric propulsion.
  • Collision avoidance may need a quicker response, favoring chemical or higher-thrust electric.
  • End-of-life deorbit may be required within a regulatory timeline.

4. Propulsion functions

Small-satellite propulsion systems are asked to do several jobs:

  • Orbit maintenance: counteract atmospheric drag and other perturbations.
  • Orbit change: raise or lower altitude, change inclination, or perform phasing maneuvers.
  • Attitude control: provide torque for pointing when wheels are saturated or unavailable.
  • Collision avoidance: execute a maneuver to reduce conjunction probability.
  • End-of-life disposal: deorbit or move to a graveyard orbit.

A single propulsion system may not be optimal for all of these. This has led to interest in multimode or bimodal systems that combine chemical and electric capabilities.

5. What this changes

  • The desktop’s propulsion choice is not one technology but a strategy for multiple maneuvers.
  • Electric propulsion is attractive for orbit maintenance but may be too slow for some collision avoidance scenarios.
  • Chemical or cold-gas systems may be needed for rapid attitude control and emergency maneuvers.
  • The next entry will read about electric propulsion specifically.