F = 2·η·P / ve (thrust from jet power)
ṁ = F / ve (propellant mass flow)
Isp = ve / g0
Δv = ve·ln( m0 / (m0 − ṁ·t_eff) )
- Power budget — every spacecraft has a limited electrical bus (solar array + battery). All three thruster types here draw the exact same power, so any difference in their thrust or Isp comes purely from how efficiently each converts electricity into directed exhaust kinetic energy.
- Resistojet / arcjet — resistively or arc-heats a light propellant gas; low exhaust velocity means each watt buys a lot of thrust but wastes propellant fast (low Isp) — closer to chemical propulsion.
- Hall-effect thruster — crossed E×B fields ionize and accelerate xenon; a middle ground between thrust and efficiency, the workhorse of station-keeping and orbit-raising.
- Gridded ion thruster — electrostatic grids accelerate ions to very high exhaust velocity; thrust is tiny (millinewtons) but propellant use is extremely efficient — ideal for long, patient deep-space burns.
- Mission comparison — for a fixed propellant mass, if the burn duration is short, only a high-ṁ thruster (resistojet) can burn through enough propellant to build meaningful Δv in time. Given a long burn duration, the high-Isp ion thruster eventually uses the same propellant mass far more efficiently and wins on total Δv. Drag the burn-duration slider to watch the winner change.