In an age where many radio based systems have fallen into disuse due to effective countermeasures, the Elite Dangerous stealth system is based almost entirely on heat. The range at which you are picked up by a ship's scanner is directly proportional to the amount of heat you are generating. If your ship is giving off no heat, another ship has to get very close indeed to properly register you.
There are two ways in Elite Dangerous to reduce heat signature: Silent Running and Cool Running.
- Main article: Silent Running
Silent running can be toggled in your ship's interface (Right Panel: Functions) or by pressing a key binding. When in Silent Running mode your shields and radiators will shut down. This means your ship will hold on to almost all the heat it generates, reducing its heat signature to virtually zero and becoming nearly invisible to other ships' scanners.
Although this can be useful, confining heat to the body of a ship means it can quickly overheat and start to take damage if you leave Silent Running mode active for too long. You should avoid using excessive thrust and energy weapons while in this state, and it is advisable to have a Heatsink Launcher on hand.
Also note that upon exiting Silent Running mode, your shields will take several seconds to come back online and regain full strength. If you exit Silent Running in an overheating ship, the release of excess heat will make your ship highly visible on all scanners in the local area, making you very vulnerable while your shields are still charging up.
Cool Running is when most, if not all, modules or systems of a ship are switched off. This causes the temperature of the ship to drop to single digits or even zero. Currently, there is no convenient way to initiate Cool Running without third-party software. Instead, the player must use the Modules tab in the Systems Panel (the right-hand panel in the cockpit) to manually turn off non-essential systems. Because Cool Running mode does not confine all heat to a ship, it avoids both the risk of overheating and the short time limit imposed on the player before their ship becomes too hot and takes damage. This means a ship can remain in Cool Running much longer than would be possible in Silent Running.
Which of a ship's modules are considered non-essential depends on the situation. For example, where one wishes to smuggle illegal goods into a starport, all but Drives and Sensors would be considered non-essential, so should be switched off. If one wishes to ambush another pilot, all but Thrusters, Shields and Life Support may be considered non-essential, allowing the Shields to be fully operational as the ambush takes place.
As a ship's temperature drops to zero in Cool Running, ice will form on the cockpit's glass. However, this can take a considerable amount of time, so a heatsink may be used to speed the process up.
The best sneaks and smugglers use a combination of Cool and Silent Running. They will use Cool Running on approach to get their temperature to zero and stay off the scanner, and then use Silent Running when they get up close. The combination of a low temperature starting point and already having many systems off means that Silent Running can last a very long time this way.
And finally it's worth noting that many players turn Flight Assist off while Cool Running so they can be moving while their drives are off. While this helps, it is not in any way necessary in most situations, unless you want to approach with your shields ready to go.