Visibility, Stealth and Detection.

In the era of high-tech science and stealth technology with a relatively long history of science-fiction imagination it is easy to simply dismiss stealth technology as a type of future-magic without backing such ideas using existing knowledge of how such technology really works. One of the main contributors to this problem is that owners of stealth technology are reluctant to openly discuss how Stealth Tech actually works for fear that an easy counter-measure will render their secrets useless.

The basic theory is that all items radiate a means of detection. In the most primative case this is optical detection - the ability to directly view the object. Other sensory methods include audio, radio, heat radiation, smell, displacement, exhaust materials and wake trails; all of which can not only be detected, but theoretically can also be disguised or hidden.

Take for example a submarine. This avoids optical detection by sinking below the water level, using the water as an optical barrier to hide it's visible profile. This also helps hide the vessel from other sensors such as smell - it's hard for a tracker dog to smell the crew of a submarine through a hundred meters of water and the vessel's thick hull.

Unfortunately for submariners the vessel is not only noisy in itself but noise carries more efficiently under water than it does in the open air, making a submarine easier to detect via sound than by sight. This is why we have developed sonar, and also why submarine movies show the crew being extremely quiet - not even daring to whisper - when anti-sub technology is being used to hunt for them.

A moving submarine with it's periscope raised, while having a much lower visible profile, can still be spotted by the splashing wake trail behind the periscope arm, or by the pattern of waves generated by the large spinning blades that drive the vessel forwards. Newer models of submarine now use arrays of much smaller propellers to help hide this wake trail when travelling under water.



Such technology of Stealth and Counter-Stealth often come with a reason not to use the detection systems to counter the effects of stealth.

It's important to remember that the spectrums by which we can analyise each detection method can be influenced beyond human's biological capability. In total darkness even a large building can be easily hidden from human sight by the simple absence of light. This was done to good effect during World War II when blackout curtains were used to hide entire cities from enemy bomber aircraft. Current technology allows for infra-red and infra-green (or light-enhancement) wavelengths to be used to spot objects in absoloute darkness.

In order to view something within the extended Red/Green spectrum you first need to expose a special light to the area. While this light allows you to more easily spot the enemy, it also allows them to spot you. You are effectively shining a huge floodlamp into darkness, just on a wavelength that you cannot see with human eyes. This is exactly the same principle as walking into a dark room with a torch in your hand. The enemy will likely see the light from your torch much faster than you can find them hiding in the darkness. If they can see into the used spectrum then any counter-measure will also expose your own location.

The same is true for using sonar to find submarines. In order to "ping" a submarine you have to intentionally transmit a signal than will reveal your location, and then wait for the echo to bounce back to identify the enemy location. The problem with this is that your enemy will get hit by the intial ping that reveals your location to them before you get the echo back that reveals their vessel.

For other detection equipment there are similar reasons not to deploy them - sniffer dogs are loud, smelly animals; electronic equipment will emit heat and electromagnetic waves; exhaust material and wake trail patterns will be disrupted if you pass through them.


For gaming mechanics, a developer needs to decide which detection factors are relevent to the vessel and environment where the game operates. You don't need to worry about how much a spaceship smells in the vacuum of space or when covering huge distances as smell would be the least plausible detection system. However you should still consider factors similar to smell, such as exhaust fumes, that can be considered as an alternative spectrum in the same way that optical light can mean using infra-red in darkness.

Also remember that if an object doesn't have any Stealth Technology that doesn't mean that it is automatically detected. Small objects are hard to spot, exhaust fumes don't identify the unique vessel that generated them etc.

For spaceship detection technology the following aspects should be the basic profiles for detection.

Optical Profile : The physical size of the vessel. Bigger vessels have a larger profile and are harder to disguise. Stealth Tech can be anything from simply using black paint or using advanced non-reflective surface material, or even smoke bombs. Note that at very long ranges used in space even a very large craft would appear tiny or even impossible to detect. Imagine looking for something the size of an office block - if you're in the same neighbourhood it should be easy to find, but if it was on surface of the moon you wouldn't be able to see it even if you know where to look.

Red-frequency Radiation : The heat given off by the vessel. In space, heat management is essential and heat dispersal provides a highly visible profile under infra-red. The physical size of the vessel does not increase the detection profile, but heat-producing engines, weapons and radiator vents will typically scale with the size of the vessel. Stealth tech involves redirecting heat internally to keep the outer hull as cold as the surroundings, or spraying heat around externally to provide a "cloud" effect that hides the ships exact location from infra-red sensors. Chaff and Flare countermeasures use this technique against heat-seeking devices.

Green-frequency Radiation : Low-light enhancement doesn't have an easy Stealth solution. While the size of the target vessel will increase the visible profile at close range it is not as powerful at long range. However, the amount of light given off by the vessel would significantly increase the green-spectrum detection as any light emitted from the target would could a large and easily detected glow in low-light enhancement. At long range you could simply "close the hatches" to block escaping light. The "hide in a cloud" solution is to bombard the area around the vessel with bright lights to blind or confuse the viewer, similar to the way Chaff and Flare operate. High frequency Strobe lights could also confuse sensors within close range, but long-range stealth would require more fictitious solutions.

Sonar / Radar : Physically larger craft would have a bigger surface area to reflect radar and enable detection. Internal components that emit radio frequencies would also reveal the prescence of a vessel and common triangulation techniques could be used to quickly locate the target. Dedicated equipment placed around a single scout ship could measure the tiny differences in signal strength and the time it takes for each receiver to detect the same signal and this provides the scout with a fairly good estimate of the direction and distance to the target. Avoiding radar can be done using two simple methods. The first is to "fly under the radar" which places the vessel close enough to expected objects that they are indistinguishable from the background noise. For both air and submarine vessels this can be done by simply hugging the ground level. While more popular in Sonar than Radar there is also the option to hide beneath a thermal layer. Water temperatures are known to vary suddenly between layers of warmer and colder areas, causing the density of the water to change in a way that creates a type of wall that deflects and confuses sonar scans. In theory the same could happen in space where radiowaves from distanct stars would create a travelling wave of radar noise that could esily hide a spacecraft. More advanced techniques are to use a special coating to the hull that absorbs radio waves instead of reflecting them.