Ion Thrusters
Ion Thrusters use only electricity to provide propulsion to their vessels and are at their best in the vacuum of deep space.
Ion Thruster
Sci-Fi Ion Thruster
Warfare Ion Thruster
Large Ion Thruster
Sci-Fi Large Ion Thruster
Large Warfare Ion Thruster
If you have purchased the Sparks of the Future Pack DLC, you can build sci-fi skinned Ion thusters with a sharper thruster flame. If you have purchased the Warfare 2 Pack DLC, you can build rectangular Ion thusters with a martial look. All DLC variants have the same functionality, sizes, and recipes.
Gallery
You recognise Ion thrusters by their blue flame
Big Blue Ship with Ion Thrusters
SOTF Patrol Bot with SciFi Ion Thrusters on an asteroid base.
SOTF Shuttle with SciFi Ion Thrusters
Comparison
Compared to atmospheric thrusters and hydrogen thrusters, ion thrusters provide slightly less force (even under ideal conditions) and draw more energy from their power supply. Similar to how atmospheric thrusters can only work in an atmosphere, ion thrusters work best in a vacuum: inside an atmosphere, ion thrusters only produce 20% as much thrust.
If your destination takes too long to reach in space even with ion or hydrogen thrusters, consider a 
Jump Drive.
Thrust Force
| Ion Thruster Size | Force of thust | Relative force (approx.) | |||
|---|---|---|---|---|---|
| Small-Grid small thruster | 14.4 kN | 1 | 1/12 | 1/24 | 1/300 |
| Small-Grid large thruster | 172.8 kN | 12 | 1 | 1/2 | 1/25 |
| Large-Grid small thruster | 345.6 kN | 24 | 2 | 1 | 1/12.5 |
| Large-Grid large thruster | 4300.0 kN | 300 | 25 | 12.5 | 1 |
For reference, 1 Newton (unit abbreviation 'N') is defined as the unit of force necessary to accelerate 1 kg of mass at 1 m/s^2. A planet with 1 G has an acceleration from gravity of 9.81 m/s^2. Thus 9.81 N of force is required to counter the gravity of 1 kg of grid mass against 1 G of gravitational acceleration (and, of course, more is needed to actually go _up_ and carry cargo). 1 kN is 1000 N, and 1 MN is 1000 kN (1,000,000 N).
Trivia
After newer Space Engineers versions have added two other kinds of thrusters, atmo and hydrogen, Keen Software House decided to make these thrusters "more-end-game orientated." With that in mind, they renamed them to Ion thrusters, and required them to be made with Platinum for Thruster Components. In the game file, Ions are simply called "thrust."
In real life, ion thrusters are used by spacecraft such as the Dawn probe which excites charged molecules to produce thrust. Currently, they are favored for long-distance space craft due to their fuel efficiency and reliability. However, unlike in Space Engineers, most current and practical forms of ion propulsion do consume some manner of fuel. Ion thrusters also make common appearances in many contemporary fictional settings as a slower but more efficient or reliable form of deep space propulsion.
Construction
If you have Progression enabled, you must build a cockpit or 
Remote Control first to unlock Ion Thrusters.
They require 
Thruster Components, which themselves need Platinum, making them expensive and tedious to craft and typically only available in mid to late game.
Ion thrusters' compact design gives them more surface areas for attaching to other blocks, making them a lot easier to design and build around compared to the round Atmospheric thrusters or conveyor-dependent Hydrogen thrusters.
Ion thrusters for small grids have the smallest mass compared to their counterparts, however the inverse is true for Large grids; large grid Ion thrusters are bigger and heavier than their sister thrusters.
See Also
