Illumination

From MegaTravellerWiki

Tentative technology list:
TL0  Bonfire, Primitive Torch
TL1  Candle, Improved Torch, Brazier, Lamp
TL2  Enclosed Candle, Lantern, Oil Streetlight, Bullseye Lantern
TL3  Gas Streetlight, Basic Omni Light, Basic Occluded Light, Mirrored Lantern
TL4  Improved Omni Light, Improved Occluded Light, Mirrored Light
TL5  Halogen Omni Light, Halogen Mirrored Light
TL6  Basic LED Omni Light
TL8  Advanced LED Omni Light, LED Mirrored Light
TL9  Basic Beamed Light
TL10 Improved Beamed Light
TL11 Pinpoint Light

Types of Illumination

Omnidirectional Lights

Omnidirectional lights emit illumination 360 degrees from the source (barring the area occluded by the source -- for instance, a lantern held in front of you will illuminate your chest, but not your back or anything behind you).

At tech level 0, bonfires and primitive torches are the only light sources available. Tech level 1 brings about the advent of improved torches, of wax- or tallow-based candles, and of open braziers and lamps which burn hydrocarbons directly. Tech level 2 brings about advanced knowledge of wicking properties of fuel, allowing lanterns and bullseye lanterns which use wick to siphon fuel instead of burning the fuel directly, and provides better knowledge of air supply allowing enclosed candle-based lanterns. Tech level 3 marks the advent of rudimentary electric lights and these begin to replace oil lamps on streets.

Omnidirectional lights that are mounted inside a dome or container of some sort can be coloured. Omnidirectional lights that are open to atmosphere cannot be coloured and take on the properties of their ordinary format (for instance, a fire in an oxygen-nitrogen atmosphere produces a yellow-orange glow).

Occluded Lights

Occluded lights are essentially omnidirectional lights that have been obscured on most of their sides to produce illumination in a single cone. The amount of occlusion determines the angle of the cone emitted, but because the occluded surface is generally just something that absorbs light, the unoccluded sides are not made any more powerful.

The earliest occluded light appears at TL2 with the advent of the bullseye lantern, which has a variable-width shutter allowing it to produce an illumination cone ranging from 180 degrees to 45 degrees.

Mirrored Lights

Mirrored lights use mirrors and other reflective elements to collect light emitted by an omnidirectional light and emit it in a cone. They are similar to occluded lights except the beams are more focused and attenuate less rapidly. The other distinction is that mirrored lights are rarely capable of adjusting the width of their illumination cone except with an occlusion-type iris.

Mirrored lights begin to appear around TL3 with the mirrored lantern, used in lighthouses among other things. Once mirrored lights are invented, they essentially supersede the occluded light and all illumination technology becomes mirrored.

Spotlights/searchlights at tech levels 5 through 9 are mirrored lights that concentrate light energy into as narrow a beam as possible. They are not true beamed lights.

Beamed Lights

Beamed lights rely on focusing crystals, gasses, and other elements to achieve a precise, powerful emission of light in the visible spectrum that does not expand in a conical fashion at all: each extreme of the beam's radius is perfectly parallel.

Beamed lights are basically very weak lasers in the visible light spectrum and are invented at TL9.

Pinpoint Lights

Pinpoint lights are advanced lights which emit rapid pulses of unique physical particles; these pulses spontaneously dissipate into photons with no harmful radiation after a certain lifetime measured in millionths of seconds. These have the advantage that the light emitter is not evident: the light is sourced from the destination point and not the emission point. The particles, however, do not penetrate even light clothing, impacting and "sticking" to the surface until they spontaneously emit their light. Any intervening obstacle in the path of the pinpoint light source thus appears to spontaneously emit light, much like a person illuminated by an ultraviolet "black" light, which can be rather off-putting.

A pinpoint light requires exponentially more power in order to increase the distance that the particles remain intact until emitting light, so pinpoint lights are generally seen only in close-range applications. The basis of the pinpoint lighting technology is eventually permuted into holographic technology.

Pinpoint lights are highly-technological compared to basic lighting and do not appear until TL11.

Illumination Technologies

TL 0

Bonfire

The bonfire is the most basic form of illumination and is the foundation of tech level 0; upon discovering the ability to ignite fires through the use of tools and raw combustible materials, a species is generally considered sapient.

Bonfires are the centres of tribal villages of pre-technological cultures. Cave-dwelling humans would build moderate-sized bonfires near the entrance to the village's cave, allowing the smoke to exit while deterring Hunter-type animals from entering the cave and harassing the villagers. The women of the village would share the fire for cooking while the men of the village would be hunting for prey or obtaining dead wood for use in the fire. As tools improved, men would begin chopping trees for firewood. Humans gradually began to build free-standing shelters around late TL0, and would maintain smaller-apportioned bonfires inside their shelters, surrounded by stones to contain the fire and retain heat, with ventilation holes to allow (most of) the smoke to exit.

Before a bonfire can be started, wood or flammable material must be obtained and placed into an area relatively devoid of other flammable materials (otherwise, the fire will spread and undoubtedly cause considerable damage). Bonfires can be started instantly with any high-energy or incendiary weapon, or by the use of any accelerant (such as hydrocarbons) and open flame. If these are not available, a character must attempt to start a fire manually:

The amount of light emitted by a bonfire is proportional to the size of the bonfire. Throwing more material into a bonfire increases its size, but also increases its rate of material consumption.

Bonfires progress according to the following chart:

  Burn Radius         Illum. Radius          Material Consumption
------------------  ---------------------  ------------------------
  same tile only      Short     (1.5 m)           12 kilograms/hr
  Dngr 1.5            Medium     (10 m)           40 kilograms/hr
  Dngr 3              Medium     (40 m)          120 kilograms/hr
  Dngr 9              Long       (90 m)          360 kilograms/hr
  Dngr 12             Long      (160 m)        1,080 kilograms/hr
  Dngr 15             Very Long (250 m)        3,240 kilograms/hr
  Dngr 18             Very Long (360 m)        9,720 kilograms/hr
  Dngr 21             Very Long (490 m)       29,160 kilograms/hr
  Dngr 24             Distant   (640 m)       87,480 kilograms/hr
  Dngr 27             Distant   (810 m)      262,440 kilograms/hr
  Dngr 30             Distant    (1 km)      787,320 kilograms/hr

The materials consumed are assumed to be the basic commodity Plants (Wood) or Plants (Lumber), which can be burned in a bonfire even if not specifically marked as Flammable. Any other commodity that is marked as Flammable can be substituted at the same rate. Other commodities might be able to be substituted, even if not marked as particularly Flammable: the referee should use common sense to decide what can be burned.

Note that the table above is rather generous -- the higher-order "bonfires" are full-fledged forest fires (many such fires would exist on a line at the leading edge of a forest fire). Such fires could also represent crashes of fully-laden fuel tankers, or fuel depots being struck by incendiary bombs. Further ranks of fires could be extrapolated, following the same pattern (Dngr (Level*3), Illum (Level*Level*10), Consumption (PreviousConsumption*3)), but bear in mind that the Dngr 30 fires are gigantic as it is.

Every hour, a bonfire "demands" its current category of fuel consumption; to indefinitely sustain a bonfire, the bonfire must be provided that amount of fuel every hour by tossing it into the bonfire's radius. If enough material is thrown onto the bonfire to allow it to move to a higher category, it does so. A bonfire can increase any number of categories at one time.

If the bonfire does not receive enough fuel, it will continue to burn at its present size and will drop one category after a number of hours equal to its burning radius' Danger Space (e.g., a Dngr 30 bonfire will drop to a Dngr 27 bonfire after burning for 30 hours with insufficient added fuel). Bonfires are assumed to have considerable supplies of unburned material within their boundaries and the largest bonfires can burn for days before they petre out. A "same tile only" bonfire will burn out within an hour if not provided sufficient fuel.

Keep track of those hours where the fire does not receive enough fuel even if they are interspersed with hours where the fire does receive enough fuel; if the cumulative total of the hours exceed the margin, the fire will drop one category, regardless of occasional proper fueling.

Bonfires produce an extreme amount of smoke and heat. Normal smoke rises naturally, so such a smoke will not generally interfere with lasers or other beam weapons on the ground unless the smoke is somehow restricted from rising. The number of kilograms of fuel consumed per hour should be divided by three to determine the number of kilolitres of smoke produced over that hour. For instance, a Dngr 30 fire produces 262,440 kilolitres of smoke per hour: a forest fire, which consists of several such fires in a line, produces enough smoke to blot out the sun.

Primitive Torch

Tech level 0 brings about the most rudimentary torch: a thick piece of wood is held in the hand and dipped into a water source of some kind to dampen one end. Grasp is switched to the damp end and the dry end is then ignited, allowing the user to carry around the resulting primitive torch to provide illumination on the run. Lighting a piece of wood in this fashion with no higher technology is no small task: the torch is almost impossible to alight unless inserted into an already-existing bonfire of some kind. Such torches burn too coolly and unevenly to light one another, although particularly flammable substances can be easily ignited with a primitive torch.

Because of the lack of any fuel other than the wood itself, the primitive torch will burn for no more than five minutes per kilogram of wood before the flames reach the damp part of the wood and begin to sizzle. At this point, the torch should be dropped and stamped out -- if allowed to continue to burn, it will slowly evaporate the water and ultimately cause a Minor Mishap (assume five more minutes before this happens, no chance to avoid). A primitive torch that has no damp end will burn to the user's hand and cause a Minor Mishap as soon as the usable area is burned.

Every five minutes a primitive torch is allowed to burn, it will drop ashes and embers; the wielder must roll on the following task to avoid being burnt:

A basic primitive torch weighs 6 kilograms (with five kilograms of usable burning area lasting 25 minutes) and occupies 9 litres. However, as a primitive torch is effectively just a piece of wood, mass and volume can vary considerably. If you want to put it to chance, roll 1d6+3 for weight and 1d6+6 for volume, and assume that one kilogram's worth of the mass cannot be burned without burning the wielder's hand.

TL 1

Candle

The candle brought about by Tech Level 1 is a surprisingly complex construction which consists of a cylindrical or rectangular length of wax or rendered animal fat into which a wick is inserted. The wick is then ignited through the use of a flint and steel or sparker.

Though when the candle was invented the phenomena of wicking was probably not understood, the underlying principle of a candle involves a complex reaction where the flame draws liquid wax or fat up through the wick, burning the wax or fat instead of the wick. As time passes, the flame slowly and evenly burns away the fat or wax and the wick gradually recedes; on a microscopic scale, the flame burns the available fuel and consumes the wick until the flame can acquire more of the fuel. Ultimately, the candle lasts for as long as the flame can both melt wax and burn wax simultaneously; if the wick should collapse into a puddle of molten wax and run out of oxygen, or if the wick should burn away all of the wax, the candle will go out.

A rudimentary candle produces a small, subtle glow, enough to identify facial features but not enough to provide bright illumination -- enough to read by if a paper is held up directly to the candle, enough to see fairly clearly within 1 metre, and enough to provide a barely-visible illumination within 3 metres. Such a candle burns for an hour.

Improved Torch

The improved torch of TL 1 is a significant advancement over the primitive torch. Instead of causing the wood itself to burn, the improved torch relies on the wood only as a basic handle; the actual element burned is a porous material, usually cloth, that has been soaked in a hydrocarbon-based material of some sort. This attachment will burn relatively safely (rarely dropping ashes or other points of ignition) for sixty minutes.

An open flame cannot directly ignite hydrocarbons as it requires the presence of oxygen; if a bucket of gasoline is instantly inverted onto a lit match, the lit match will be doused (but please don't try this at home). Therefore, the hydrocarbon fuel that is soaking the porous material cannot be burned directly: only the fuel that is on the surface of the torch's head can be ignited. As the flames burn away the fuel on the surface the porous material itself becomes dry and unprotected and so the surface layers of the porous material then burn away. This process happens continuously, with the hydrocarbons slowly burning and the material slowly burning until the head (and a fair portion of the underlying handle) is burned away entirely.

Anyone wanting to light an improved torch may do so in the same fashion as starting a fire on any bed of dry kindling due to the high flammability of the torch's head. However, if the torch becomes wet it will not light until completely dry.

An improved torch weighs 4 kilograms and occupies 5 litres.

Brazier

The oil brazier from Tech Level 1 is the simplest hydrocarbon-burning illumination vessel which paved the way for the lantern. It is filled with hydrocarbon-based fuel, as well as heat-retaining stones or other fireproof objects, and this fuel is then ignited. Fuel cannot burn without oxygen, so only the extreme surface of the brazier between the stones is actually lit, with the remainder of the brazier consisting of fuel waiting to be burnt.

A brazier must be extinguished before it can be safely refueled; generally this means that the brazier is allowed to burn out before it is filled. After burning out, the brazier is very hot for approximately one hour, and spontaneous ignition of hydrocarbons poured into the brazier may occur.

Braziers are essentially controlled bonfires and behave similarly in terms of illumination. The radius of the brazier's font (the hydrocarbon receptacle) determines the amount of hydrocarbons fuel consumed per hour according to the following:

TODO Brazier size chart

A brazier is ignited by carrying a burning torch and touching the torch to the edge of the fuel where it touches the side of the font. No other method of igniting a brazier is safe.

Lamp

The oil lamp (such as the Genie's Lamp of Arabian Nights fame) invented at TL 1 is a system which uses hydrostatic pressure from a central reservoir to push hydrocarbon fuel up a spout and wick opposite the handle. The tip of this wick is ignited and will continue to burn until the level of the fuel in the lamp is so low that the flame has burned the wick too far down the spout to be able to get any oxygen.

A small oil lamp contains approximately 20 millilitres of hydrocarbon fuel and burns this fuel gradually and evenly. A large oil lamp contains double the amount of fuel. It does not have a larger spout.

Both lamps provide the same amount of illumination as one another. The lamp illuminates a radius of 2 metres clearly, with light bright enough to read by within one metre, and illuminates a radius of up to six metres with bare illumination (enough to distinguish shapes but not details).

A small oil lamp burns for one hour. A large oil lamp burns for two hours.

Standard Lights

In general, various cultures have adopted certain standards of lighting which are required for safety or visibility purposes.

Contact Vehicles

Most surface friction vehicles are equipped with several lights:

• Two Beamed Lights, coloured white, to illuminate the path ahead of the vehicle. Usually these are mounted directly to the vehicle's forward grille, though on occasion they may also be installed in sponson turrets to allow the headlights to track ahead during a turn. Two lights are provided in order to give a sense of depth and to allow redundancy in the event that one is damaged or destroyed. The length of the light beam should be sufficient enough that the operator can stop in the distance that the beams illuminate (otherwise the driver should limit their top speed accordingly). A typical vehicle requires five seconds to stop at high speed: a vehicle that travels at 120 km/h (33.3 m/s) on-road should have beams that illuminate up to 150 metres ahead. Actual braking efficiency depends on tech level, terrain, and vehicular mass, so this is a guideline only.

• Two Omni Lights, coloured red, are attached to the rear of the vehicle to signify to other vehicles that this vehicle is slowing or stopping. These lights activate when brakes are applied in the case of contact-based vehicles, or when the vehicle is travelling faster than its throttle setting in the case of thrust-based vehicles. At night, these lights are usually engaged at half-strength to allow the vehicle's position to be better estimated. These lights do not need to be particularly powerful: the minimum illumination radius of 1.5m is more than sufficient to allow other pilots to see the vehicle from behind.

• Two Omni Lights, coloured white, are attached to the rear of the vehicle to signify to other vehicles that this vehicle is moving in reverse or about to do so. These lights activate when the throttle is moved into reverse in the case of thrust-based vehicles or when the transmission is engaged in reverse gear in the case of contact-based vehicles. Some vehicles choose to omit these in favour of a mild high-pitched warning siren, and some have both the siren and the reverse lights. These lights are usually powerful enough to provide the driver with illumination within 5 metres behind the vehicle.

• Four Omni Lights, coloured yellow, are attached to the four corners of the vehicle to indicate when the vehicle is about to change direction or position. These lights strobe at even rates and can be activated or deactivated from the vehicle's control panel.

• One or two Omni Lights, coloured white, intended to illuminate the vehicle's rear-mounted registration marks, although these are usually optional if the registration marks are painted in retroreflective colours that make them clearly visible when illuminated externally from any angle.

Hydrocraft, Aerocraft, and Aerospacecraft

• Two Omni Lights, coloured yellow and red, are attached to the left and right extremes of the vessel's port and starboard. These lights are called "running lights" and strobe periodically.

• Two more Omni Lights, coloured white and green, are attached to the fore and aft extremes of the vessel, which also strobe periodically and make up part of the vehicle's running lights.