Planetary Properties Guide

# Planet Properties

On every single planet's page, there will be labels on the varying properties of the planet regarding the atmosphere, biosphere, and the temperatures and the like that are important to keep in mind. These tags are listed here and taken straight from the Stars Without Number rulebook.

## Atmosphere

### Corrosive

Corrosive Atmospheres are dangerously hostile to conventional vacc suits and other protective gear. Corrosive worlds have a number of intrinsic adventure complications, the largest being the way that every activity outside of a hab building comes with a built-in time limit. Whatever the party chooses to do outside of a building, it has to accomplish before their suit seals fail or the atmosphere corrodes a hole in their vehicle hull.

### Inert

Inert gas atmospheres aren’t hostile or poisonous, but they’re unbreathable by humans. If the planet’s climate is otherwise tolerable, the natives might be able to live and work outdoors without anything more than an air tank and face mask.

### Airless/Thin

Whatever atmosphere exists is too thin to support human life, if it exists at all, and the world is largely naked to the chill of space and the blaze of stellar heat. Exposure to the planet’s surface without a vacc suit or pressurized building is as lethal as exposure to hard vacuum.

### Breathable Mix

Breathable mix atmospheres can support human life without additional equipment or gengineered modification. Any world that has a human population in the millions or more almost certainly has a breathable mix atmosphere.

### Thick

Thick atmospheres can usually be breathed with the aid of a filter mask, though the mix of contaminants renders it slowly or quickly toxic to humans who attempt to breathe it straight. Thick atmospheres are often at least semi-opaque, and some worlds have thick atmospheres that are completely impenetrable to ordinary light. Deep banks of permanent fog might shroud the planet, or natives might have to go about with sophisticated ultraviolet or infrared viewing equipment if they don’t wish to be blind.

### Invasive

Invasive toxic atmospheres are composed of a substantial proportion of molecules small enough to infiltrate past the seals of most vacc suits. This infiltration doesn’t harm the suit, but the molecules have to be steadily flushed by the system’s purification sensors before they build up to a debilitating level.

### Invasive and Corrosive

Corrosive and invasive atmospheres exist at the very border of what human society can tolerate. Combining all the worst traits of an eroding, corrosive atmosphere and the invasive intrusion of toxic molecules, a planet cursed with an atmosphere like this is far more hostile than any mere airless rock.

## Temperature

### Frozen

Frozen worlds are those with so weak a stellar primary or so great a distance that the average temperature is close to absolute zero. Any atmosphere that once existed has long since frozen into drifts of solidified oxygen or lakes of liquid helium. Exposure to these drifts is very dangerous. Vacc suits maintain a tolerable temperature easily because the stellar void is very empty, and there is little conduction of heat between the suit and empty space. Dunking a suit into a lake of thermally-conductive superchilled liquid can force the heating elements into sudden and drastic overload, draining a power cell in minutes or even seconds.

### Cold

Cold worlds are uncomfortable, but a human can survive on them in nothing more than heavy clothing. The worst of the cold worlds are similar in condition to Earth’s Antarctic regions, barren wastes of ice and wind. The more clement ones have brief warmer seasons or equatorial bands that get enough solar radiation to support substantial agriculture.

### Temperate

Temperate worlds were the most popular colony sites, and most of the truly populous worlds of the frontier have a temperate climate. Many temperate worlds have temperature ranges not unlike that of Earth, though most are canted a little further toward cold or heat depending on their angle and proximity to the local star.

### Warm

Warm worlds come in two main flavors, depending on the prevalence of water. Desert worlds are hot enough or arid enough to be deprived of most surface water. The other common variety of warm world is one blessed with an abundance of surface water.

### Burning

Burning worlds are too hot for a human to survive without equipment similar to a vacc suit in effectiveness. Rivulets of molten lead or copper might bleed from open veins on the hillsides, and many of the same perils that face an explorer on a frozen world have hotter equivalents on a burning one. Ash drifts, pools of molten metal, and superheated liquid vents can bring quick death to an unwary explorer, and the miners who inhabit such worlds must be forever vigilant against the perils of their burning home.

## Biosphere

### Biosphere Remnants

Biosphere remnants are the wreckage of a ruined ecology. Petrified trees, drifts of preserved bones, forests of dead plant life; something killed all the life on this planet in the relatively recent past.

### Microbial

Microbial life is often the only thing that exists on the more inhospitable planets, yet the wide variety of environments that can accommodate life means that these little beasts show up in some of the most unlikely places.

### No Native Biosphere

No native biosphere is occasionally found on even the most temperate and otherwise habitable worlds. For one reason or another, life simply never evolved on these worlds, leaving them a blank slate for the agricultural and ecological efforts of humans.

### Human Miscible

Human-miscible biospheres are those in which some substantial portion of the native life is biologically compatible with human nutritional needs. The local plants and animals may not be tasty or terribly nourishing, but they can support life without the serious importation of Terran crop seeds and livestock.

### Immiscible

Immiscible biospheres are not friendly to humans. None of the local plants or animals are edible, and anything the colony needs to eat will have to be grown from Terran stock. Worse, it is common for the pollen and other microbial life of these worlds to be highly allergenic to humans, requiring the regular use of tailored antiallergenics to prevent eventual respiratory failure or exotic immune-system reactions.

### Hybrid

Hybrid biospheres are a stable intermixing of Terran flora and fauna with local life forms. Most such worlds have been colonized for centuries before the Silence, giving the local ecology time to shake out into a relatively stable configuration of Earth-born organisms and native life. The native biology may or may not be miscible with human life, but it is unlikely to be particularly hostile in any case, or else the interloping life forms would not have been able to get a foothold on the planet.

### Engineered

Engineered biospheres are among the rarest, as they require enormous time and effort on the part of a highly advanced civilization. Whatever life exists on this planet has been extensively altered by an alien race or by advanced pretech gengineering methods. Some such worlds are paradise planets, carefully sculpted by some fabulously wealthy predecessor to suit their own tastes.

## Tech Level (TL#)

### Tech Level 0 (TL0)

Tech level 0 represents a world with technologies similar to neolithic-era humanity. Natives of a world at this tech level might retain elaborate cultural artifacts and a very sophisticated society. Existing resources tend to be exploited to the hilt, with large populations producing massive stone cities, human-powered engines for irrigation, and vast displays of foodstuffs and craft work for the ruling class. Despite this, the lack of metal, domesticated beasts of burden, and petrochemicals puts a hard stop on the technological development of most of these worlds.

### Tech Level 1 (TL1)

Tech level 1 represents a world with technologies similar to medieval-era humanity. These worlds have managed to find and exploit metal deposits and likely have imported or domesticated beasts of burden. Those worlds with easy access to fossil fuels or a similarly energy-dense substance can advance to greater things, but a culture trapped at TL1 is unlikely to have access to such helpful resources.

### Tech Level 2 (TL2)

Tech level 2 represents a world with technologies similar to industrial-age humanity. These worlds are blessed with the presence of fossil fuels or a feasibly abundant biofuel source. Internal combustion engines are crude things compared to the power of a fusion plant, but they can be built with primitive tools and a basic degree of education. The mechanization that results from this resource vastly increases the efficiency of local farming, the speed of travel, and the productivity of factory workers. Most tech level 2 worlds are “knockdowns”; planets that once had a much higher degree of sophistication but were recently crippled by disease, disaster, or invasion. The natives tend to be keenly aware of the glories of former generations, and work fiercely to redevelop lost techniques and reclaim old knowledge.

### Tech Level 3 (TL3)

Tech level 3 worlds are those that have developed to a level much like that of the more advanced nations of late twentieth-century Earth. The main difference between tech level 3 worlds and level 4 worlds is the lack of fusion power or spike drive manufacture. Simply providing a world with the necessary technical data for advancement doesn’t mean that advancement will be quick or even.

### Tech Level 4 (TL4)

Tech level 4 worlds are the most common in human space, and their technical expertise is the baseline for modern post-Silence “postech”. These worlds can create spike drives rated up to drive-3, fusion power plants, grav vehicles, simple energy weapons, and medicines that extend human life to a hundred years of vigorous good health. They can manage sophisticated gengineering on simple life forms, and some tech level 4 worlds have even attempted to improve the genetic structures of human life itself.

### Tech Level 4+ (TL4+)

Tech level 4 with specialties is an unusual case of a normal tech level 4 world that has retained some pretech industries or has developed their own local technical expertise beyond baseline postech in certain specific fields.

Most such specialties are relatively narrow in scope; grav tech, medicine, hydroponics, force field generation, or some field of roughly similar breadth. These specialties are usually either the product of a few irreplaceable pretech manufactories or the result of some unique local resource that serves amazingly well for the purpose at hand. In both cases, the world will jealously guard the tech, and much local conflict may relate to control over these resources.

### Tech Level 5 (TL5)

Tech level 5 is the highest tech level that might merit random placement. A world with this level of technological expertise has somehow managed to hold on to the majority of the pre-Scream technology base, and can produce a wide range of goods that are unknown on less sophisticated worlds. Miniaturized fusion plants, drive-6 rated spike drives, exotic grav weaponry, and even the development of psionics-based “psitech” is possible on such a world.

### Tech Level 6 (TL6)

Such worlds are advanced to the point beyond recognition. These would typically include transhumanist societies with values and philosophies incomprehensible to the current human populace and technology that would put pre-tech to shame. This is a theoretical Tech Level in the context of SWN and is only here for hypothetical comparison. If such a society were to exist, then their technology would routinely abuse commonly assumed principles of known TL4 and TL5 physics. Some alien artifacts may be at Tech Level 6.