🛸 Ion Thruster — Electric Propulsion

Ion thrusters accelerate charged particles (usually xenon) using electric fields to generate thrust. They produce very low force but achieve extremely high specific impulse (Isp), making them ideal for long-duration deep-space missions where propellant mass must be minimized.

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Ion Thruster

Mission ΔV Planner

Thruster Stats

Thrust—
Exhaust velocity—
Mass flow rate—
Propellant needed—
Wet/Dry ratio—
Burn time—

vs Chemical Rocket

🛸 Ion (this)
Isp = — s
Prop = —
🔥 Chemical
Isp = 310 s
Prop = —
Physics:
F = 2ηP / (Isp·g₀)
ve = Isp·g₀
ΔV = Isp·g₀·ln(m₀/m₁)
mp = mdry·(eΔV/ve−1)

How Ion Thrusters Work

A neutral propellant gas (typically xenon) is ionized by electron bombardment or RF energy. The ions are then accelerated by a strong electric field to exhaust velocities of 20–80 km/s — compared to 3–4 km/s for chemical rockets. This gives ion thrusters a 10-30× higher Isp, meaning far less propellant is needed for the same ΔV. The tradeoff: thrust is extremely low (millinewtons to tens of millinewtons) and requires continuous power. NASA's Dawn spacecraft used ion thrusters to orbit both Vesta and Ceres; JAXA's Hayabusa used them for asteroid sample return. Modern Hall-effect thrusters and gridded ion engines are now standard for GEO satellite station-keeping.

About Ion Thruster Simulator

An ion thruster is an electric propulsion device that accelerates ions to produce thrust. Propellant (typically xenon gas) is ionised inside a discharge chamber — electrons are emitted by a hollow cathode, collide with xenon atoms, and strip electrons to create Xe+ ions. These ions are electrostatically accelerated through a high-voltage grid assembly and expelled at velocities of 30–80 km/s, far exceeding the 2–4 km/s exhaust velocity of chemical rockets.

The key figure of merit is specific impulse (Isp), the thrust produced per unit of propellant weight flow rate. Ion thrusters achieve Isp values of 2,000–10,000 seconds, compared to 300–450 seconds for the best chemical rockets. While thrust levels are very low (millinewtons to hundreds of millinewtons), the high efficiency means a spacecraft can achieve the same velocity change (delta-v) with a fraction of the propellant mass, dramatically reducing launch mass for deep-space missions.

Ion thrusters are used in deep-space probes (Dawn, Hayabusa2, Psyche) and satellite station-keeping. NASA's Dawn spacecraft used xenon ion propulsion to orbit both Vesta and Ceres, the first spacecraft to orbit two extraterrestrial bodies. Hall-effect thrusters, a closely related technology, use a magnetic field to trap electrons and are widely deployed in commercial communication satellites for orbit raising and station-keeping.

Frequently Asked Questions

How does an ion thruster produce thrust?

An ion thruster ionises propellant (usually xenon), then uses a strong electric field between a perforated screen grid and an accelerator grid to accelerate the ions to high velocity and eject them from the spacecraft. By Newton's third law, the ejected ions produce a reaction force — thrust — on the spacecraft.

Why can't ion thrusters be used for launch from Earth?

Ion thrusters produce very low thrust (typically millinewtons to a few newtons), far less than the weight of even a small satellite. They are only useful in the vacuum of space where small continuous accelerations can accumulate over months or years into large velocity changes. Chemical rockets are required to overcome Earth's gravity and atmospheric drag at launch.

What is specific impulse and why does it matter?

Specific impulse (Isp) is the thrust produced per unit weight flow of propellant, measured in seconds. High Isp means more thrust per kilogram of propellant burned. Ion thrusters achieve Isp of 2,000–10,000 s compared to 300–450 s for chemical rockets, requiring ten times less propellant for the same velocity change — critical for long-duration space missions.

What is xenon used as propellant in ion thrusters?

Xenon is an ideal propellant because it is chemically inert (will not corrode the thruster or storage vessel), has a high atomic mass (131 u) so ions carry significant momentum, is a gas at room temperature but liquefies under moderate pressure for dense storage, and is easily ionised with modest energy. It is expensive but available in high purity from industrial air separation.

What is the difference between an ion thruster and a Hall-effect thruster?

Both are electrostatic ion accelerators using xenon, but Hall thrusters trap electrons in a crossed electric and magnetic field (Hall drift), using them to ionise propellant without a separate discharge chamber. Hall thrusters operate at lower Isp (~1,000–3,000 s) but higher thrust density than gridded ion thrusters. They are dominant in commercial satellite applications due to their simpler construction.

About this simulation

This simulation shows how an electric ion thruster converts electrical power into thrust by accelerating xenon ions through a high-voltage grid. Adjust the input power, specific impulse (Isp) and thruster efficiency to see how thrust, exhaust velocity and propellant consumption respond, then use the built-in mission planner to work out how much xenon a spacecraft would need for a given delta-v. A live comparison bar shows how the same manoeuvre would look with a 310-second chemical rocket instead.

🔬 What it shows

The animated beam represents ionised xenon accelerated out of the grid assembly and ejected as a stream of glowing particles; particle speed on screen scales with the Isp slider. Behind the scenes, thrust is calculated as F = 2ηP / (Isp·g₀), where g₀ is standard gravity, so raising power or efficiency raises thrust, whilst raising Isp for the same power actually lowers it, since more energy goes into each ion's speed rather than the number of ions.

🎮 How to use

Set Power (0.5–50 kW), Isp (500–10,000 s) and Efficiency η (0.30–0.90) in the Ion Thruster panel to change the thruster itself. In the Mission ΔV Planner, drag Spacecraft mass (kg) and Mission ΔV (km/s) to size a manoeuvre; the Thruster Stats panel then updates thrust, exhaust velocity, mass-flow rate, propellant mass, wet/dry ratio and burn time, whilst the vs Chemical Rocket card benchmarks your Isp against a 310-second chemical stage.

💡 Did you know?

NASA's Dawn spacecraft used three xenon ion thrusters, throttled between roughly 0.4 and 2.3 kW, to become the first probe to orbit two separate bodies beyond Earth, Vesta and Ceres, whilst carrying under 500 kg of xenon propellant across its entire multi-year mission — a feat no chemical rocket could match on the same propellant budget.

Frequently asked questions

How is thrust calculated in this simulation?

Thrust follows F = 2ηP / (Isp·g₀), where P is electrical input power, η is thruster efficiency, Isp is specific impulse in seconds and g₀ is standard gravity (9.81 m/s²). Because this equation divides by Isp, pushing the Isp slider higher whilst holding power fixed actually reduces thrust, since the same power is spent accelerating fewer ions to a higher exhaust velocity.

What does the Mission ΔV Planner calculate?

It applies the Tsiolkovsky rocket equation, ΔV = Isp·g₀·ln(m₀/m₁), rearranged to find the propellant mass mp = mdry·(e^(ΔV/ve) − 1) needed for the spacecraft mass and delta-v you set. Burn time then follows by dividing that propellant mass by the mass-flow rate, showing how long the thruster would need to fire continuously.

Why is exhaust velocity so much higher than a chemical rocket's?

Exhaust velocity here equals Isp × g₀, and because the thruster accelerates ions electrically rather than through combustion, it can reach 20–80 km/s, several times the 2–4 km/s typical of chemical propellants. That higher exhaust velocity is what lets ion propulsion achieve large delta-v with comparatively little propellant mass.

Why does the chemical rocket comparison need so much more propellant?

For the same delta-v, the propellant mass required falls exponentially as Isp rises, following the rocket equation. A chemical stage fixed at 310 s of specific impulse must expel propellant far faster relative to its exhaust velocity than an ion thruster running at, say, 3,000 s, so the wet/dry mass ratio and propellant mass shown for the chemical case are typically many times larger.

Why is efficiency η included in the thrust equation?

Not all electrical power fed into the thruster ends up as directed kinetic energy in the ion beam; some is lost ionising propellant, heating grids and other inefficiencies. Efficiency η, adjustable between 0.30 and 0.90 in this simulation, scales the usable power in the thrust formula, so a less efficient thruster produces less thrust from the same input power.