A Question of Supply

How much food does your star ship carry?

 

A 40x8x8 ft iso container can hold an average of 1200 cases. Averages are based on common 750ml bottles in 12 pack cases.  A ssl "star ship layout" cargo pod is 33x13x9 ft in size, with its internal volume divided into 2 rooms of 13x11x8 ft. Thus the total cargo capacity is very close to the same as the old iso container.

If we assume 1 bottle is enough concentrated food for 1 person / day, then a cargo pod would hold 14,400 man-days of food. Enough food for a crew of 10 for 4 years. If we use a less efficient and more varied food supply, (the crew likes this) we need about 2 bottles / person / day, so a Cargo Pod will provide our crew of 10 food for 2 years. 

 

Thus it is reasonable to stuff a small ship with 1 year worth of food, in its internal cargo bays.

For Example;

The long range Sabre ALREX, wich replaced the Ranger as the main exploration ship,  has a crew of 20 and will need about 1 cargo pod worth of food for one year. Thus its internal cargo bay #3, slightly larger than a cargo pod, will be optimized for food storage. 

 

Something to drink with that?

 

Water tanks used are normally 15x5ft = 2,200 gallons / 8,330 litters. 

A person should drink about 2 litters (0.5 gallons) per day.

The average person use at home uses about 80-100 gallons of water per day. This can easily be cut to 50 gal/day on a ship. So our crew of 10 on a small trip, using 500 gallons / day have no problem assuming the water filtration system works. 

Several 2,200 gallon tanks with a filtration system should be good for 1 year of ship operations. If you aim to have your ship do 1 year missions, you will install the right number of tanks plus a bit extra. Keeping in mind even with a good recycling system some water will be lost in use.

A Ranger for example usually has 4 of these water tanks.

How is the air in there?

Air tanks are the same size as the water tanks, holding 8,330 litters each. 
The average person consumes 1.5 litters of oxygen / minute.  Thus one tank would give one person about 92.5 hours or 3.8 days of breathable air, assuming the filtration system was not working. Now consider how fast this number changes if the entire crew of 10 is present.  They have about 9 hours. 
Also consider that a ship has a large volume of air in it already, all the various rooms.  
A Ranger for example has 8 air tanks. 

What about growing it fresh?

 

A 40ft iso container used as a hydroponics farm can grow the same as 3-5 acres of land, depending on crop type. In a space setting a wide mix of crops are preferred to add variety to the diet. 

A ssl Cargo Pod can be outfitted a similar way as a hydroponic farm. 

The VF-Growers Company does produce a specialized pod, in which half is a traditional hydroponic farm while the other half is a fish farm. Although the total food yield produced is on the low end, the variety is a great supplement to the canned supplies.  

Making something out of nothing. 

We often see in fiction that a ship is running out of air or water or fuel. This would only be the case if the ship is badly damaged. Water is broken down into hydrogen and oxygen by electrolysis. This is always a subsystem in the life support unit that can do this. Thus you may sacrifice water to keep breathing and to fuel your engines. Or you can use the system to force combine oxygen and hydrogen into water, if that is what you are running out of.  

 

Alternative Supply Numbers

The info below comes from a documentary about the planned expedition to Mars. 

 

One person consumes about 2.5 kg of food, 3 kg of water, 1 kg of oxygen per day. 

Thus a crew of 10 consumes 25 kg food, 30 kg water, 10 kg oxygen per day. 

A life support system will include reclamation units that can recover some of the water and oxygen, however the food is basically a wast product once it passes through a person. A sub unit of life support, can process the poo into a compact fertilizer powder, good for the hydroponic garden if you have one. 

 

The amount of supplies carried will depend on the mission time table, but are usually measured in months / 10 man crew.  For example; Food 759 kg. Water 900 kg. Oxygen 300 kg.  

A ship on a 6 month mission, would need; Food  4,500 kg. Water 5,400 kg. Oxygen 1,800 kg. 

Reminder there is 1000 kg / ton.