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Thursday, July 19, 2018

Traveller Thursday: Life Support

I'm not 100% back to writing about Traveller. I just happened to have a sudden realization about something that has been bugging me for years and I wanted to write it down before I forgot.

My use of Traveller setting and dress falls under
fair use guidelines for both Mongoose and Far Future Enterprises.

The thing which bugs me most about ship design in Mongoose Traveller is that there's no mention of life support. I realize that life support has been ex post facto folded into stateroom tonnage, but that doesn't quite make sense because stateroom tonnage has already been explained as covering both the rooms themselves and the common areas.

(Quick digression for those who don't recall what I'm talking about: in Traveller, staterooms displace 4 tons but in most deckplans they are displayed as only displacing 3. That extra dton is allocated for corridors, common rooms and the like. The problem is, when you get anal and decide to count how many dtons of corridors and room space there are, it adds up to way more than the number of staterooms in the ship.)

What's funny is that I realized the actual number of staterooms doesn't matter. What matters is "How many people can you cram onto a ship", and that's actually a completely different question than "How many staterooms are there", because you could fit a bunch of refugees into an empty cargo bay. No, what matters is how much food, air and water they consume. In other words, we need to calculate how many dtons of life support one person requires.

So let's work this out:
  • One person in a low berth displaces 1/2 dton and requires no life support. 
  • Because people who aren't in cold sleep need food, water, oxygen, and space to move around, let's double that for human-sized crew. 
    • K'kree and other livestock-sized animals displace twice that amount. 
    • Hivers also displace the same amount of space as humans; we just think they take up more space because their longest axis is horizontal whereas ours is vertical. 
  • Since everything is based around the standard jump time of 1 week, let's assume that life support dtonnage is done by the week. This reflects food that needs to be bought, filters that need to be changed out, waste that needs recycling into water, etc. 
  • Don't forget that transit time to and from the jump point, so you probably should have 2 weeks per person. This could probably be extended in an emergency through rationing and depressurizing non-inhabited parts of the ship, but that's a subject for a different article. 
  • This gives us a hasty figure of 2 dtons per person for a commercial ship -- or half a stateroom, which is in line with the core rules when they say "No stateroom can contain more than two persons, as it would strain the ship’s life support equipment." This seems reasonable and tells me I'm on the right track. 
  • But what about ships that stay on station for weeks or months at a time, like Scouts on survey or the military on patrol? Well, this is handily addressed in High Guard (1st edition High Guard, to be clear -- I don't play 2e Mongoose Traveller) when it talks about endurance and nicely accounts for food packs, oxygen scrubbers/filters, and other assorted spare parts that are needed for basic maintenance and are stored in compact form:
Endurance
Ships are able to operate for one month without needing to go into a spaceport for maintenance, assuming an adequate supply of fuel. This is increased by one month for every 1% of total tonnage dedicated to cargo. If fleet support vessels are in attendance then another three months can be added to the time needed before maintenance is required.
  • In other words, each 1% of total tonnage dedicated to supplies represents an additional month of life support as already allocated. If you have more people than your life support is rated to handle, you're going to be dipping into supplies early.  

At this point I imagine some of you are saying Whoop-tee-doo, Erin. If life support requires 2 dtons per person for an average trip, how is this any different from stateroom tonnage? and my answer to that is this:
  1. It frees up tonnage from the obligatory "The captain (and sometimes senior officers) always get their own private stateroom aboard ship";
  2. It allows the Navy to pack crew in tight (1 dton/person) for maximum warfighting efficiency, because fleet support ships exist to solve this very problem;
  3. It adds realism, and possibly dramatic tension, to scenarios where a player character's ship is used to rescue a bunch of people and/or has a cargo hold full of live animals;
  4. It gives ship designers one less thing to worry about. Staterooms stop being gameable spaces and become set dressing like common rooms. 
Maybe no one will care about this. Maybe this was all a waste of time. I don't know. What I do know is this: Something which had been bugging me is no longer bugging, and that makes me happy. 

I just make the free ice cream. Whether or not you eat it is your business.

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