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Tanna-Sheru, Alkaidin System

This article originally appeared on the Freelance Traveller website in 2008, and was reprinted in the October 2013 issue.

Alkaidin system is a typical frontier colony system, abnormal only in having both a Navy and Scout base in the system.

Alkaidin (“The Bases”) is a typical M2V red dwarf star with three planets and an asteroid belt. The sun is a blood-red cinder of a star, speckled with black and orange sunspots, about 40% Solar mass with only 3% Solar luminosity, emitting mostly in the infrared.

That is, unless there’s a flare. Though not large enough to qualify Alkaidin as a true flare star, solar flares of brilliant white erupt at irregular intervals over a period of days to weeks, lasting hours to days. Though only increasing brightness by a few percent, the increase is mostly UV, effectively changing the star's spectrum for a short interval.

Alkaidin I (Orbit 0) is a double planet, Tanna (B6A72M7-A) and Sheru (B563411-C). This double main world has a total population of around 50,000, mostly on Sheru. These are the only bodies in the system with official names.

Alkaidin Belt (E000312-B, Orbits 1-2) is a medium-density double asteroid belt scattered between the first two planets. With a population of 6000 belters, it is the only other “inhabited world” in the system and a mainstay of the system's economy.

Alkaidin II (VLGG, 1000 T-mass, Orbit 3) is a Very Large Gas Giant with a thin ring and twelve moons at about 1 AU. At three Jupiter masses, Alkaidin II has too high a surface gravity, too strong a magnetosphere, and too violent an atmosphere to be suitable for fuel skimming. Massive upwellings contaminate the atmosphere with impurities from the depths, giving the planet the appearance of “Jupiter with Smallpox”. The twelve moons cluster in three main orbital groupings:

Alkaidin III (LGG, 100 T-mass, Orbits 4-6) is a smaller but still Large Gas Giant in an eccentric resonance orbit that sweeps the outer system from 2 to 5 AU. A “ringless Saturn” with three large moons, its color varies over time; Saturn-yellow with some white cloud bands at perihelion, and featureless Uranus-cyan at aphelion. Its size and calm atmosphere make Alkaidin III the preferred choice for fuel skimming. The outermost and largest moon is of interest: a Size 6 “Super-Triton” with a thin inert atmosphere, continents of ice, and oceans of liquid nitrogen (freezing over at aphelion), its retrograde orbit marks it as a capture from further out.

Alkaidin III’s eccentric orbit has swept a clear zone out to 10 AU from the sun (and probably caused massive planetismal/asteroid/comet bombardments in the system’s early history). Beyond this, some iceballs may remain undiscovered and a thin Kupier belt hints at the extreme age of the system; all other asteroids and comets have been swept out by Alkaidin III or eaten by Alkaidin II.

Tanna-Sheru (Alkaidin Ia and Ib)

Named after a legendary pair of lovers, Tanna and Sheru form a double planet with an orbital period and tidal-locked day of about 100 hours, with a year of only 12.2 local days. Temperature variations are extreme, warming to temperate/warm over the fifty hours of ruddy daylight, followed by fifty hours of freezing night. Tidal stress from the nearby sun (three times that of the Earth/Moon system) ensures both worlds are seismically and volcanically active, with spectacular mountains.

Both worlds have similar gravity—about 0.75G—and similar atmospheric pressure—about that of Earth at 1500m altitude.

The red dwarf sun looms huge in the dark indigo sky of both worlds, a dull speckled red disk edged by visible prominences, over three times “normal” size but casting only a dull red twilight (at least to human eyes—a species that can see infrared will find the daylight much brighter, if still limited in color). UV emissions are so low that a human on either world’s surface can stare at the sun for several minutes without eye injury, studying the ever-changing patterns of convection cells speckling the surface.

The only exception to the dull red light is during a solar flare, where the color shifts to a more “normal” tone for hours to days and the sun cannot be stared at safely.

And over half of each world looms its companion world, filling six full degrees of sky, four times the apparent diameter of the sun. From Sheru, Tanna would be dull dirty white and frost-greys if it weren’t tinted red by the sunlight. From Tanna, Sheru is more colorful—with darker patches and continents below the clouds and between the large polar icecaps, still color-shifted by the sunlight. Sheru’s small landlocked oceans are a bit more interesting; at the morning terminator they are iced over, red-tinted frost-grey; as the day sweeps across the surface the ice cracks and melts; first tidal crackings like on the gas giant’s moons, then splitting off into giant icebergs (visible from orbit) amid lines of blue-black which grow until at the evening terminator the oceans are the blue-black of open water.

Alkaidin II and III also stand out in the night sky as bright reddish-orange planets (changing color to white and yellowish during solar flares); the largest moons of both gas giants are visible to the naked eye.

Tanna (Alkaidin I-A) B6A72M7-A Poor/NonInd/NonAg Navy Base

Tanna is a “snowball world”, with an almost all-nitrogen atmosphere and frozen-over oceans despite its volcanic activity—from orbit, the world looks like a dirty iceball with dark volcanic fallout plumes marking the locations of landmasses. Though frozen on the surface, the deep oceans are kept liquid by tidal-fueled geothermal heat, the enormous tides cracking the ice to the surface and pulling up water in upwellings that sink and re-freeze as the tide drops. The resulting temporary open water absorbs enough greenhouse gases from the atmosphere that the planet will probably not thaw for several million years. There is no known indigenous life, though deep-ocean microbes are possible around geothermal vents.

The only settlement on Tanna is Alkaidin Navy Base, with a permanent population of only 300 (Navy dependents and small Startown) but a transient population of maybe ten times that number. The base serves a local patrol squadron of destroyer-sized ships and acts as a logistics way station. The base has a reputation as a “bad posting”—not unpleasant, just boring. Confined to the base complex by the unbreathable atmosphere (requires O2 tanks and mask), with outside temperatures never above freezing, and some mountain crags on the horizon the only scenery other than a permafrost plain, the only alternative is shore leave on Sheru, which is barely surface-habitable and not much more settled.

Sheru (Alkaidin I-B) B563411-C Poor/NonInd Scout Base

The slightly-smaller half of the double planet, Sheru is a cold borderline-habitable world with a thin breathable atmosphere and enough greenhouse gases in its atmosphere to keep from snowballing like its companion. The main difference is Sheru is more volcanically active and is a life-bearing world—primitive multicellular life, but still life.

Sea life is primarily algaes, sponges, and plankton both uni- and multi-cellular; the most advanced form large black algae mat colonies that drift through the seas. The most advanced land life are lichens and a para-crystalline colony bug similar to Mithril’s “Crystallice”. All photosynthetic life (plants, such as the algae and lichen) are black or maroon to maximize light capture from the red dwarf sun. Almost all land life has a very fast life-cycle, growing during the fifty-hour day and then either encysting or sporating and dying off during the fifty-hour night in the manner of Mithril’s “Ephemeral Glades”. Solar flares have been known to stimulate exaggerated growth and bring to life some normally-dormant forms. All known life-forms are asexual, reproducing by fission or budding/sporating.

(The encounter tables from the double-adventure scenario Mission to Mithril will work for Sheru, with the exceptions that the “ephemeral glades” run through their life-cycle entirely within a local day. Local “vegetation” would only be mosses and lichens instead of Mithril’s true plants, and there would be no “animals” large enough to see with the naked eye.)

Sheruvian geography is primarily rugged tundra and maroon-lichened treeless savanna with a few landlocked “oceans” (Hydro 30%); about half the seas are connected by rift-valley “tidal-bore rivers” whose flow can reverse due to the massive suntide. Despite the drab terrain, the world has some spectacular glacier-carved mountains and active volcanic fields; some of the larger shield volcanoes rise up out of the breathable atmosphere, and the most violent eruptions can shoot debris into orbit.

The settled areas on Sheru all hug the equator, as this is where the temperature is the most tolerable (at least in the daytime). Above about 30 N and S latitude, the climate becomes too cold for permanent settlements.


Safe Jump distance from Alkaidin is 0.45 AU (100 solar diameters)—approximately the outer edge of Alkaidin Belt, about 70 milllion km outside Tanna-Sheru’s orbit. Boosting out this far takes 45 hours for a 1-G ship to 22 hours for a 6-G ship, giving Alkaidin Base about one standard day’s early warning of any attack—and a similar time to intercept anyone (like player-characters) trying to flee the system.

Every Tanna-Sheru day (four standard days) roll 2D for the chance of solar flare; on a natural 2 or 12, there is a flare whose effects last for 1D standard days (1D/4 Tanna-Sheru days). Effects of a flare are:

On Sheru, there is little organic material outside of lichens and molds; except for basic foodstuffs, all other organic materials must be imported. Sheruport and other “company towns” are built under dome-roofs; similar but cheaper “inflatable greenhouses” cover the local agricultural land. Outside of these towns (such as on homesteads), architecture is either imported prefabs or local masonry (unmortared stone or rammed-earth), heavily-insulated against the freezing 50-hour nights. Most homesteaders will go outside only during the "warm" daytime; at night, they stay inside unless absolutely necessary.

Cautions and Hazards

Tanna’s atmosphere is unbreathable (not poisonous per se, but has no free oxygen), and the surface temperature is below freezing except for a few hours during the hottest part of the day.

Sheru is habitable, but temperatures usually drop well below freezing during the fifty-hour night—if caught in the open at night without cold-weather gear or a way to keep warm for two standard days, you will freeze to death. (A temporary “igloo” snow shelter and a portable heater will provide enough shelter except during blizzard conditions; making a slow fire of dried native lichens is a desperation move only because of the resulting stench and irritating smoke.) In addition, the daily thawing can cause ice-dam flash floods; these are a constant hazard on watercourses in the late afternoon.

Several varieties of local lichen have become a mold/mildew nuisance—the warmer colony/building interiors trigger their “ephemeral glade” life-cycle nonstop; any spores or fragments tracked in grow rapidly into a form of mildew which is a major nuisance. This can come as a surprise to offworld visitors.

Also, three of the native life forms—two unicellular microbes and one multicellular—are pathogenic to humans.

The two microbes are analogous to anthrax, causing fatal necrosis (flesh-eating) and sepsis (blood poisoning) upon infection. Called “Black Blood” and “Black Crater” from the visible effects, both these diseases are fatal (99+%) if untreated but like true anthrax are not casually contagious; though common on Sheru where they are endemic, there has never been an offworld case of the disease or a case of contagion once removed from the planetary environment. There is an effective vaccine available. (Treat either of these diseases as anthrax in effects; infection can be cutaneous (skin), pneumonic (lung inhalation), or intestinal (digestive), with similar effects and progression to true anthrax.)

Because of these two diseases, all visitors to Alkaidin system must first put in at the Highport stations, be vaccinated against the twin diseases, and wait 24 hours for the immunity to take before continuing on-planet.

Compared to these, the multicellular pathogen is only a serious nuisance, though it can still put you in a hospital. The pathogen is a microscopic multicellular colony-creature that encysts itself through the long night and becomes active and reproduces asexually during the day. Looking like a faint sparkling dust, it burrows into sources of warmth (like a human body) to reproduce, causing massive skin irritation and rash like a souped-up scabies. (Treat as “crystallice” from Mission on Mithril.)

Because of the red dwarf sun, long-term visitors can get used to looking directly at the sun for short periods (a few minutes) without harmful effects. This can set them up for eye damage (retinal burns) if they do the same during a solar flare.

History and Population

At the time of its first survey, about 150 years ago, the system had no name—just a catalog number, a typical red dwarf (like 80% of all stars) with a VLGG whose only peculiarity was a double snowball in close orbit. The Scout Service did mark this particular red dwarf as a possible site for settlement, due to the lack of flare activity and one of the two close-in snowballs being life-bearing.

So the matter stood until a little over 50 years ago, when the system was selected for both a minor Navy and Scout base. Renamed “Alkaidin” (“the bases” in a language with Semitic roots), the double main world was also given names and divided between Navy (on Tanna) and Scouts (on Sheru). Detailed Scout survey also discovered Sheru’s two lethal diseases and nuisance parasite, and soon developed a vaccine against the former.

With the local pathogens under control, the world was now clear for settlement; that is, if anyone would be interested in such a harsh world. This was remedied by the continuing survey, which had found several interesting organic compounds in the local lichen and plankton—interesting enough to attract the attention of a megacorp.

Leasing Sheru as a company world, the megacorp began developing and exploiting the organic compounds, harvesting lichen and farming plankton blooms for the organic compounds. Over the past 50 years, this has provided modest but steady returns, enough to attract a population of 50,000—Scouts and dependents, starport staff, base/starport support town (and Startown), corpos, and independent homesteaders (most of them franchise-subcontracted to the corpos).
Once the Scout base was operational and a permanent population established insystem, the local asteroid belt attracted the attention of belters. These started prospecting the carbonaceous chondrites of Alkaidin Belt for hydrocarbons and metals, finding enough to attract the attention of another megacorp. This megacorp leased major claims in Alkaidin Belt, grudgingly accepting the existing belters as subcontractors and freelancers while starting more organized mining and exploitation. Though still small-scale compared to belts in major systems, the corporate and independent operations are enough to support a population of about 6000, centered around the main corporate station (a hollowed-out asteroid from the first wave of prospecting).

Both independent homesteaders and Belters include among their number some “crazy hermit” types who have as little to do with the outside world as possible. Even without the crazy hermits, there is often a rift between the corporate-affiliate types and the true frontier-attitude independents.

Within the independents and homesteaders, there is a tradition of extending hospitality to strangers seeking shelter overnight or in a blizzard-storm. This hospitality customarily lasts for only one night or the duration of the storm, after which the visitors are expected to be on their way.

Economy and Trade

Alkaidin System is classified as Poor/Non-industrial, with an Eaglestone Trade Index of 2. This translates to a maximum of 100 passengers and 1500 tons of freight per week, much of that Navy and Scout Base support.

The system economy is based on resource extraction—organics from Sheru and hydrocarbons and metals from the Belt—with some base support and through-ship servicing. Not much to hang an economy on; both megacorps consider their insystem holdings as backwaters, and if they were ever to pull out, the colony would pretty much go bust.

Megacorp-run “lichen plantations” grow the commercially-viable species of lichen around-the-clock, using floodlights and heaters to simulate ephemeral glade conditions through the night. The lichens are harvested and processed daily; outside the lit and heated areas, the lichens die off/go dormant during the night, preventing runaways; to shut down a plantation that is growing out of control, just turn off the lights and heaters and the crop will die back.

Offworld trade of the “cash crops” and major imports is largely handled by the megacorps or megacorp-contracted carriers. Free-traders have a niche for secondary items too small or too inconvenient for the megacorp shipments, and for independent scheduling between the regular (and infrequent) corporate shipment dates.

The system does have enough agriculture to feed itself, though the local climate and sunlight don't grow human-edible crops very well. Much of the agriculture is based on mutant crop plants grown in artificially-lit greenhouses and under clear inflatable “valley roofs” using artificial soils fertilized by treated sewage. Locally-produced foodstuffs are adequate but monotonous; there is always a market for seasonings or exotic imported foodstuffs.

Ports and Facilities

Most of the port facilities are at the two Downports—Alkaidin Base on Tanna and Sheruport on Sheru. Both are rated as Class B Starports, except Tanna’s is restricted to military and emergency traffic. Though both ports are rated Class B and have all the amenities of such, they are both very small.

Refined fuel is readily available, skimmed from Alkaidin III by fuel lighters and refined enroute. (Alkaidin II has too high a surface gravity to be skimmable and too contaminated an atmosphere to be practically refinable.) The three fuel lighters are all technically Navy, though one of the three is on (unofficial) long-term loan to the Scout Service and handles the Scout/civilan facilities at Sheru Highport.

Both ports have minimal highport facilities, basically small space stations at the L4 and L5 points, forming a rosette with the two worlds. The military highport (consisting of about 1/3 of the base) exists primarily to service unstreamlined ships and provide Zero-G repair facilities; the smaller civilian highport (rotating population of about 300) primarily serves as a customs point and vaccination site for all visitors, and secondarily for service and maintenance of Scout and civilian ships. Sheru Highport’s shipyard facilities are scaled around Scout Service needs, and can fit only ships of up to 400 tons (Scout-configured Type Ts); the Navy base’s yards are scaled for frontier escorts and patrol craft, with a size limit of around 2-3000 tons (such as Longsword, Kanin, or Krupny-class light DDs).

Surrounding Sheru Downport is Sheruport, the only “city” on the planet (permanent population about 15,000), built under a series of overlapping geodesic domes for climate control during the long day-night cycle.


The system has no single government. Tanna and its highport are a military reservation auxiliary to the Navy base, and Sheru and Alkaidin Belt are corporate holdings of two different megacorps, ruling their holdings according to different charters.

Megacorps vary in how they govern. Though they are there to make as much money as they can from the world’s resources, they usually don’t follow the activists/media’s portrayal of the Rich Corporate Overlords exploiting the Poor Defenseless Locals who only have Us Concerned Activists for help—such neo-feudal attitudes have gotten megacorps run off the planet, sabotaged, and/or resisted in real life. Wars, unrest, and resentment from the locals are bad for business in the long run—that is, unless you’re a mercenary company. There is some exploitation - in the sense that the corp does get the better end of the deal whenever it can—but not to the level generally thought.

Armed Forces

There are no indigenous armed forces per se. The Navy base and its attached system defenses and Marine contingent fill the function. Marines also provide security at both highports and Sheru Downport.

System defenses run about 1500 tons of dedicated SDBs and fighters from the Navy base, plus whatever Navy starships are in-system at the time.

In addition, the Corporation on Sheru maintains its own security forces, the paramilitary (as opposed to police) elements of which total somewhere around a reinforced company, equipped to TL10-12. Due to the local environment, these elements are grav-mobile (G-carriers), trained for search and rescue as well as combat, and equipped for Arctic conditions.

Scenario Nuggets

Sheru and Alkaidin Belt are chartered and held by different, possibly rival megacorps. There is always the possibility of friction and conflict between them. Though the Navy/Marine presence would inhibit outright local tradewar, there could be industrial espionage or just plain non-cooperation as each corp protects its turf from the other.

In addition, one or both megacorps might be casting an eye on expanding their operations to Tanna, subleasing from the Navy. Or a third megacorp might be interested in Tanna if there’s something found there to exploit. Though most of the action would be outside the system - lobbying efforts in the local capital—there is still the possibility of a corporate “bootleg” operation with the tacit approval (or at least non-objection) of the Navy Base commander. (Probably under the cover of a corporate exploration/scouting/mapping project with all information forwarded to the Navy.) Tanna’s a big place, and a total population of a few hundred Navy personnel can only effectively control the area of the surface base itself and most of the approach routes.

And there is always the possibility of friction between the megacorps and the locals. Belters and “crazy hermit” frontier colonists are notoriously independent, and one "pointy-haired" planetary manager can spark a lot of trouble from “uppity frost-heads”. Free-traders, as equally-independent spacers, often get dragged into this.

Note: For the classic “crazy hermit” lifestyle, think Unabomber without the bombs. Small insulated “cabin” with most of the space taken up by storage of supplies, a couple dug-in inflatable greenhouses to grow food, occasional trips to “town”, otherwise minimal facilities, and the attitude of a “Mountain Man”.

A world of only 50,000 (most of those concentrated in Sheruport and scattered corporate enclaves) and settled for less than 100 years has a lot of unexplored territory. There is always the possibility that some hitherto-unknown life-form or local condition could be the basis for a whole new industry. Or adventure.

Accordingly, the megacorp(s) do sponsor exploration teams, either corporate or (more often) independent contractors.

Travellers going overland on Sheru (or forced down by a blizzard-storm) could be trapped during the freezing night for an arctic-survival adventure. Taking shelter in a homestead could cause problems with the locals—there is an unwritten custom of hospitality to strangers during the night/storm, but there is also something called Cabin Fever. Or you could end up holed up in a homestead-cabin with a real Crazy Hermit…