1. The engine that trades time for fuel

Arthur C. Clarke’s 2001: A Space Odyssey returns as the recalled work because Discovery’s journey is made possible by engines that are efficient rather than fast, turning a small amount of propellant into a large change in velocity over months and years. Electric propulsion does the same for small satellites.

This entry reads about electric propulsion for small satellites.

2. Electrospray thrusters

Electrospray thrusters extract charged droplets or ions from an ionic liquid using electrostatic fields. An arXiv study of electrospray plume impingement notes their advantages: specific impulse above 1,000 seconds, power consumption below 10 W, and scalability to sub-100 gram systems. Thrust levels are typically 1 to 100 micronewtons per emitter.

Challenges include:

  • Plume divergence: half-angles of 25 to 47 degrees can contaminate solar arrays and sensors.
  • Lifetime: current electrosprays are expected to operate reliably for roughly 500 hours at nominal thrust.
  • Neutralization: emitted charges must be neutralized to avoid spacecraft charging.

3. Hall-effect thrusters

Hall-effect thrusters ionize propellant, usually xenon, and accelerate it with an electric field crossed with a magnetic field. A University of Alabama thesis on micro-Hall thrusters compares Hall systems to other electric options: higher thrust than electrospray but also higher complexity and power consumption.

For small satellites, Hall thrusters are attractive when more thrust is needed than electrospray can provide, but they require more power, more mass, and more thermal management.

4. Pulsed plasma and other options

A NASA Space Grant review summarizes pulsed plasma thrusters and vacuum arc thrusters as low-power, non-toxic options with fewer failure points but limited flight heritage compared to electrospray and Hall systems.

5. When electric propulsion fits

Electric propulsion is best for:

  • Long-duration orbit maintenance where thrust can be low.
  • Missions with limited propellant mass.
  • Platforms with surplus solar power.
  • End-of-life deorbit where a slow spiral is acceptable.

It is less suitable for:

  • Rapid collision avoidance.
  • Large orbit changes under time pressure.
  • Missions with tight power budgets.

6. What this changes

  • Electric propulsion is a strong candidate for the desktop’s orbit maintenance and deorbit.
  • Plume impingement and lifetime must be considered in the platform layout.
  • The desktop’s power system must support electric propulsion when it is operating.
  • The next entry will read about chemical and green propulsion.