esampson
SOC-13
So I was thinking about water on starships in the Traveller universe (initially with whether life support recycles it or what) and I came across some interesting facts.
The first is that discounting watering the lawn the average person uses approximately 50-100 gallons of water per day. This includes things such as water used for showers, toilets and washing dishes. That corresponds to about 180-350 liters per day. Around half of that will be used for showering. For toilets you can probably assume less around 30 liters. Less than 4 liters of the daily water usage is actually spent in drinking.
Assuming none of it is recycled that adds up to about 2500 liters per week or less than .2 DTons, which is very little (though not inconsequential, especially when multiplied by an entire crew) space.
This leads to some interesting concepts. In the case of military and 'working class' ships we can probably assume very heavy recycling of water. It isn't that the water will take up enormous amounts of space but as an example just a meager Scout/Courier would probably have to set aside nearly 1.6 DTons for water (this would allow for up to 8 crew members for a week).
So for ships of that nature carrying enough freshwater for a trip (with adequate safety margins) isn't practical, but what it is practical for are things such as yachts, especially if you use water from the bath/shower/dishes (with filtering) for things such as flushing the toilet.
If a ship were to have freshwater for drinking, throw away water used by the toilet, and recycle all other water after filtering the water usage per person would be approximately 10 gallons or 35 liters per day. The ship would need a standing supply of, say, 90 liters per person + 250 liters per week. For the example of the Scout ship that works out to 4720 liters or only .35 tons.
So this gives us a figure of about .04 DTons of water per passenger with passengers drinking freshwater and 'throwing away' black water. While that is far from the minimum a ship might need (the minimum being less than .01 DTons per passenger with full recycling) it seems to me like a good number for passengers on a mid passage. In the case of passengers who have booked high passage there wouldn't be any point to more than .2 DTons per passenger (and you could quite likely get by with a lot less with recycling).
Of course space on a ship is precious, so it might be hard to scrape up 20 DTons to set aside on a Nobles yacht, right? Actually, it should be easier than you think.
Every molecule of water is approximately 11% hydrogen by weight. Since 1 DTon of water is 13.5 cubic meters of water that means it weight 13.5 tons. 11% of 13.5 tons means that there is actually a bit more than 1.5 tons of hydrogen per DTon of water.
That's right, water contains more hydrogen than liquid hydrogen by volume.
The biggest problems are that water weighs a whole lot more and the hydrogen isn't immediately accessible. It's pretty easy to break it apart using electricity from a ship's power plant but it still takes time. Because of this you probably want to carry enough liquid hydrogen for the jump drives since they can gobble it up in a hurry, but for your power plant it should be quite possible (and in fact more space efficient) to run on water.
And the best thing about running your power plant on water? Breaking down the water will produce more oxygen than you could possibly need. A human being consumes approximately 5.5 kg of oxygen per week. 1 ton of oxygen is enough for 200 people for 1 week, approximately, and the process of breaking down water for hydrogen releases 8x as much oxygen by weight. That means that every ton of hydrogen a power plant consumes per week produces enough oxygen for about 1500 people.
The first is that discounting watering the lawn the average person uses approximately 50-100 gallons of water per day. This includes things such as water used for showers, toilets and washing dishes. That corresponds to about 180-350 liters per day. Around half of that will be used for showering. For toilets you can probably assume less around 30 liters. Less than 4 liters of the daily water usage is actually spent in drinking.
Assuming none of it is recycled that adds up to about 2500 liters per week or less than .2 DTons, which is very little (though not inconsequential, especially when multiplied by an entire crew) space.
This leads to some interesting concepts. In the case of military and 'working class' ships we can probably assume very heavy recycling of water. It isn't that the water will take up enormous amounts of space but as an example just a meager Scout/Courier would probably have to set aside nearly 1.6 DTons for water (this would allow for up to 8 crew members for a week).
So for ships of that nature carrying enough freshwater for a trip (with adequate safety margins) isn't practical, but what it is practical for are things such as yachts, especially if you use water from the bath/shower/dishes (with filtering) for things such as flushing the toilet.
If a ship were to have freshwater for drinking, throw away water used by the toilet, and recycle all other water after filtering the water usage per person would be approximately 10 gallons or 35 liters per day. The ship would need a standing supply of, say, 90 liters per person + 250 liters per week. For the example of the Scout ship that works out to 4720 liters or only .35 tons.
So this gives us a figure of about .04 DTons of water per passenger with passengers drinking freshwater and 'throwing away' black water. While that is far from the minimum a ship might need (the minimum being less than .01 DTons per passenger with full recycling) it seems to me like a good number for passengers on a mid passage. In the case of passengers who have booked high passage there wouldn't be any point to more than .2 DTons per passenger (and you could quite likely get by with a lot less with recycling).
Of course space on a ship is precious, so it might be hard to scrape up 20 DTons to set aside on a Nobles yacht, right? Actually, it should be easier than you think.
Every molecule of water is approximately 11% hydrogen by weight. Since 1 DTon of water is 13.5 cubic meters of water that means it weight 13.5 tons. 11% of 13.5 tons means that there is actually a bit more than 1.5 tons of hydrogen per DTon of water.
That's right, water contains more hydrogen than liquid hydrogen by volume.
The biggest problems are that water weighs a whole lot more and the hydrogen isn't immediately accessible. It's pretty easy to break it apart using electricity from a ship's power plant but it still takes time. Because of this you probably want to carry enough liquid hydrogen for the jump drives since they can gobble it up in a hurry, but for your power plant it should be quite possible (and in fact more space efficient) to run on water.
And the best thing about running your power plant on water? Breaking down the water will produce more oxygen than you could possibly need. A human being consumes approximately 5.5 kg of oxygen per week. 1 ton of oxygen is enough for 200 people for 1 week, approximately, and the process of breaking down water for hydrogen releases 8x as much oxygen by weight. That means that every ton of hydrogen a power plant consumes per week produces enough oxygen for about 1500 people.