PROPULSION / Comparison
Different engines. Different advantages.
Compare the mechanism before comparing the promise. Choose a mission, then work backward to its requirements.
There is no universally best engine. First choose the mission and identify the mass, power, thermal and environmental constraints. These are mechanism-level comparisons, not Metric Flight performance ratings.
6 candidates shown
Scroll horizontally to compare every column →
| Candidate | Momentum goes to | What must improve | Research role |
|---|---|---|---|
| RF plasma / magnetic nozzle | Expelled plasma | Coil geometry, detachment, total efficiency | Specialist ground research |
| Microfabricated electrospray | Expelled ions or droplets | Emitter uniformity, lifetime, contamination | Precision small-spacecraft study |
| Hall / gridded ion | Expelled ions | Lifetime, propellant utilization, power system | Established-technology benchmark |
| Laser thermal | Heated exhaust | Receiver temperature, beam availability | External-power feasibility |
| Laser ablation | Expelled target material | Impulse repeatability, plume and debris | Pulsed micropropulsion study |
| Electrodynamic tether | Planetary field and plasma system | Deployment, current closure, orbital environment | Environment-specific orbital study |
The whole system decides.
Compare at the same mission duty cycle, input power boundary and useful impulse. Include tanks, power processing, magnets, neutralizers, receiver optics and radiators where required. A lighter emitter is not necessarily a lighter propulsion system.
Reference points, with their boundaries.
These examples describe different devices and operating conditions. They are not six equivalent specifications. Unreported values remain unreported; a patent or concept study is not a lifetime test.
| Route / evidence | Published or derived scale | What this does not establish |
|---|---|---|
| RF nozzle · Takahashi 2022 | 5 kW forward RF; ~30% thrust efficiency. Derived from rounded inputs: ~79 mN, ~3,850 s, ~16 mN/kW. | Not total electrical efficiency; 5 s pulses, no lifetime qualification. |
| Electrospray · ST7 flight record | 5–30 µN; 0.1 µN resolution for colloid microthrusters. | Does not qualify another emitter, propellant or array. No generic power/Isp claim. |
| Gridded ion · NASA NEXT 2014 summary | 0.5–6.9 kW; 26–236 mN; 1,400–4,190 s. Maximum efficiency 71%; endurance >49,900 h reported. | Ranges span operating points, not simultaneous values. NEXT is not a Hall thruster; endurance applies to this test history. |
| Laser thermal | Concept and subsystem studies; no common qualified engine specification selected here. | Optical absorption is not measured thrust. Beam and receiver losses must be included. |
| Laser ablation | Compare impulse per measured incident joule for a specified target, wavelength and pulse. | Patent 9,021,782 supplies no validated performance or lifetime value. |
| Electrodynamic tether | F = I L × B for a simplified segment; geometry, current closure and orbit are required. | No universal thrust, Isp or efficiency independent of the environment. |
THE NEXT MOVE / BUILD THE EVIDENCE
A better engine begins
with a better experiment.
Bring a measurement, a materials capability or a mission requirement. Help turn a promising mechanism into a testable design.