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Variant Ship Life Support Rules for Mongoose Traveller

This article originally appeared in Issue #009 of the downloadable PDF magazine.

I find the Mongoose Traveller Life Support rules to be lacking. The system, as presented in the Rulebook, lacks granularity, assumes monthly re-supplies and thus ignores the possibility of deep, long-range space forays that might last for many months, or even years, without return to civilized space, and simplifies the matter to a simple exercise of economics. It also fails to provide answers to what will happen when a starship’s life support systems are forced to supply sustenance for more beings than it was originally designed to.

This simple system, while adding a bit of extra math to the game, will hopefully help sort the conundrums indicated above. It will also provide a means of extending the life support of a ship for crews wishing to do so. These rules were extrapolated from the notes on page 142 of the Traveller rulebook, the standard life support costs and the stateroom occupancy rules. While they may change the game somewhat, I believe they remain faithful to the concept of how starship life support systems are suppose to work in the Traveller Universe.

New Concept: The Life Support Unit

The “Life Support Unit” (or “LSU”, henceforth), is an abstract measuring unit that represents the minimum materials and consumables necessary to maintain an average human being (or an equivalent sophont or life-form) alive aboard a starship for one week. It includes food, water, atmosphere, pressure, temperature, recycling, etc.

Each ship will be able to “carry” a maximum number of LSUs depending on its design. The total number and nature of living beings aboard will determine how many LSUs are lost per week. At properly equipped starports extra LSUs may be purchased, much the same way one purchases fuel, up to the maximum LSU limit for the ship. It is also possible to buy extra equipment that will increase the maximum LSU limit of a vessel without any re-design required; this shall be explained further bellow.

Starship Autonomy

First, it is necessary to determine just how many LSUs a starship is able to carry. This will determine the maximum possible autonomy with its current crew before a replenishment of life support consumables is required. The formula below calculates this:

[Maximum LSUs = Staterooms 48]

So your typical Type-S Scout ship, with its total of 4 Staterooms has a maximum LSU capacity of 192. [4 48]

A brand-new ship will, of course, come with a full complement of LSUs. A second-hand (or third, fourth, etc.) ship will have a random number of LSUs remaining in its stores, roll two dice per stateroom and multiply the result by four.

Remaining LSUs on 2nd-hand Ship =

[2 Staterooms]d6 4

To determine how long a starship can maintain its crew and passengers alive for, we need to determine the weekly expenditure of LSUs. Dividing the remaining LSUs of the ship by this number gives us that period in weeks.

Different People, Different Needs

This is where it gets more complicated. The same way that food and beverages differ a lot in quality between what is found aboard a modern-day nuclear submarine and a luxury ocean liner, each being aboard the starship might have different needs according to its nature. This means in the number of LSUs each consumes per week can vary. Each living creature on the ship will fall under one or more of the categories indicated bellow.

Crewmembers: this category includes everyone, from the captain to a passenger on a working passage, that has a working role inside the ship. As all work under a military, or quasi-military, structure, efficiency is paramount and luxury is dispensable. A non-crewmember might also fall under this category, for example, a friend of the PCs taking a free ride aboard their ship that does not demand the same conditions as a paying passenger.

Crewmembers consume the absolute minimum LSU to keep them healthy, alive and in working condition, 1 LSU/Week.

Middle or High Passengers: passengers expect a minimum (or a whole lot) of comfort for their money, and to ensure conditions aboard the ship are as similar as possible to a non-closed environment, the life support system must work overtime. This will ensure they are provided with much more palatable food, remarkably stable pressure and temperature conditions and “clean” air, fully devoid of troublesome odours that crewmembers have long since become immune to. Such luxury (from a crewman’s perspective) does not come without a price; each of these passengers devours a full 6 LSUs/Week.

Low Passengers: technically dead, or at least as near to it as possible that they might still be brought back, low passengers do not consume any LSUs.

Refugees: not necessarily a “true” refugee, but most often found under this class on account of being one, a refugee is anyone aboard the ship that exceeds the maximum number of lifeforms it was designed to carry comfortably at any given time. For each starship this number limit is determined by the formula below:

[Maximum Lifeforms = 2 x Staterooms]

It is easy to see that the maximum number of beings a starship can carry without need of overdriving the life support system is equal to having all its staterooms in double occupancy.

With no more available staterooms, there is nothing to prevent someone from “roughing it” aboard a starship wit no vacant staterooms by settling on the cargo hold. But what will be the effect on the ship’s life support system of providing for a living creature pressure, temperature, breathing air in an area that was not properly designed for it? And what will be the effect be on the food processing and recycling systems when they have to work beyond their normal parameters and specifications to account for the extra creatures? The answer is that each refugee will spend 2 LSU/Week, equivalent to twice the LSUs require for a human or human-equivalent crewmember residing in a stateroom.

So, a Type-S Scout with its 4 staterooms, carrying 20 people aboard would have 8 “crewmembers” (with each stateroom in double occupancy) and 12 “refugees” in the cargo hold for a total weekly LSU expenditure of 32. [8 crew + (12 refugees 2)]

Physical space is not usually an issue. One displacement ton can carry a whole lot of people when all you need is a spot on the ground to sleep. A Type-S, even with its minute cargo space could carry a small village; a Free Trader could hold an entire extended tribe of over a hundred. However, scheduling meal times and bathroom trips might be a bit of a chore...

Exotics: exotics are creatures that have very specific life support needs and/or those that vary considerable from the human norm.

Examples include lifeforms that are used to extreme high or lows of temperature or pressure, breathe exotic atmospheres, need rare trace elements for their respiration, or have radically different biological make-ups, such as a silicon-based lifeform. An exotic consumes an extra 5 LSUs/Week in addition to what a normal lifeform of its class (crewmember, passenger, refugee) would require. If the creature is considerably larger than a human (see below) the LSU consumption multiplier is applied after all other modifiers.

The larger the lifeform, the greater its life support requirements. If it breathes more, eats more and...well, excretes more, it will put extra strain of the ship’s life support system. For simplicity, humanoids down to Droyne size and dog-sized animals (not lap dogs) count as human for LSU consumption. Anything smaller than these (a cat, rabbit, pet parrot) is not factored in for the LSU consumption equations. Aslan or similarly-sized humanoid creatures also count as a normal human despite being bigger.

The number of LSUs consumed per week for a creature considerably larger than a man is multiplied by the ratio (rounded) of the creature’s mass to that of the average human (treat the average human mass as 100kg).

For example: a bovine beast of roughly 500kg mass would consume five times the required LSU of a normal human, or 5 LSUs/Week. If this bovine was a sophont paying passenger he would consume a staggering 30 LSU/Week. [6 (passenger) 5 (size)]

And should he need argon for breathing and considerable amounts of colloidal silver in its food, the total weekly LSU consumption would be a whopping 55! [(passenger) 6 + (exotic) 5] 5 (size)]


Weekly Consumption of LSUs
Class  LSUs/Week
Crewmember  1
Refugee  2
Low Passenger  0
Middle Passenger  6
High Passenger  6
Apply the following modifiers, in order,
after determining the base requirement above
Exotic Requirements  +5
Size   (Creature mass 100kg, rounded)

LSU Costs

Minimum Starport Quality
for LSU Replenishment
Ship Class  Starport Class
Non-Jump  C (Routine)
Starships  B (Good)
Capital Ship  A (Excellent)

LSUs are bought and replenished at a starport much the same way fuel is. But it is not a simple matter or replenishing air and buying food. A fully-working life support system requires precious or rare metals, high-tech filters, exotic chemicals and nanotechnology components that are either spent, or loose their efficacy over time. Furthermore, since LSU purchase includes the replacement of technical parts, the class of ship of determine the minimum class of Starport where it may “refuel” LSUs. Non-Jump ships can top up LSUs at any starport of class C or above, Starships require a class B Starport or better, while Capital Ships can only acquire LSUs at class A starports.

The price of each LSU is variable, and like all other products subject to the economical laws of supply and demand. To determine the price per LSU at any particular starport, roll two dice and multiply the result by ten.

Price per LSU: 2d6 10 Credits

Increasing Autonomy

Under this system the maximum life support autonomy for every player character type ship is 6 months for full double occupancy of staterooms, or 1 year for full single occupancy.

Six months to one year, not counting with extra LSU expenditures for passengers, should serve for the needs of most player character crews. But what happens in a campaign dealing with deep forays into uncharted space, where high-tech civilization and life support replenishment might not be available for years? Read on...

New Ship Equipment:
Extended Life Support Module

Extended Life Support modules (ELS, henceforth) are the standard method of augmenting the autonomy of a ship without need for any redesign of its architecture. ELS modules are self-contained mechanisms/stores roughly 14 cubic meters (1 displacement ton) in volume that increase and extend the capacity of the life support system, and can be lodged in the cargo hold much like a standard cargo crate. Every module can hold the equivalent of 12 LSUs. For every four full modules in the hold, add one to the maximum lifeforms aboard the ship for the purpose of determining Refugee status.

Each module takes up one ton in the ship’s cargo hold and costs Cr62,000. It takes one day to install a ELS module in the ship’s hold, and this can be done at any class of starport where the ship is able to purchase LSUs.

An Example

Complement Aboard the “Reggie”
Entity  Class  LSUs/Week
Piago Pian  Crewmember 1
Tensher Wolf (“Tiger”)  Crewmember 1
Curtis Tyrone  Crewmember 1
Johannes “Slew” Barton  Crewmember 1
Pakea Dimiigur  Crewmember 1
Rolf Edmundsun  Crewmember 1
Total Weekly LSU Consumption   6

Let us take the Type-S from the Traveller campaign where I currently play: the “Reggie”, a second-hand starship leased by the IISS to retired Senior Scout Paigo Pian.

First, determine how many LSUs the ship has remaining; with 4 staterooms I get to roll 8 dice: 6, 5, 4, 3, 3, 2, 1, 1 for a grand total of 25. Multiplying this by four I get a round 100 for the current LSUs of the ship.

The complete list of entities aboard the “Reggie” and their class and LSU requirements can be seen to the right.

Summary LSU Data: Type-S “Reggie”
Staterooms  4
Maximum Lifeform Carrying Capacity  8
Maximum LSU Capacity (No ELS modules)  192
Current LSUs  100
Weekly LSU Expenditure  6
Remaining Estimated Autonomy  16.6 weeks

100 LSUs divided by 6 is 16.6, so the “Reggie” should be able to operate for more than 16, but not quite 17, weeks before needing to replenish LSUs (at a Class B or better starport). The final LSU info for the "Reggie" appears to the right.