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ILJackson In reply to space-commander [2013-11-02 19:51:05 +0000 UTC]

Depending on the ship, I figured there's a balance point where a trip is too short to require cryosleep and too long to go without putting everyone in the tubes. The biggie has got to be water. That's going to be the heaviest, hardest to transport consumable, even with advanced recycling, and the one that takes up the most space. 

I think a ship's cryotube policy would be based on personnel and mission. For example, marines being transported go into cryo at launch and aren't awakened until they arrive at their destination. While a space naval vessel's crew is awake for well into a trip, because they need to drill, learn to work together, etc...naval vessels do a LOT of onboard training and doing that while in FTL is a great use of time. But that means their range is affected and they have to stop frequently at what I call anchorages for resupply. If they are going outside of controlled territory, where there's no infrastructure, it's into the cryotubes for all but a rotating skeleton crew and the captain and the department heads.

For a big civilian ship, anything over a week would be everyone in cryotubes while in FTL, with ship functions run by an A.I. onboard computer. They would be awakened a day or two before they drop from FTL to account for medical emergencies, cryosickness, new orders or course corrections (hey! the update says the planet we were heading to got hit by a comet the week after we left! There goes  this mission...) and other unexpected issues, as well as briefings and such.

For small civilian ships it would depend on the captain's budget. But most would want the crew in cryosleep most of the time in FTL to save money.

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Zomvee In reply to ILJackson [2013-11-11 19:38:19 +0000 UTC]

Couldn't you just solve the problem with the water by just having two tanks of hydrogen and one tank of Oxygen, you could save alot of room by going with that idea, I would think.

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ILJackson In reply to Zomvee [2013-11-12 04:38:30 +0000 UTC]

that's more dangerous to transport. Hydrogen and oxygen, on their own, are extremely volatile. And you aren't saving any room or weight. You just have to add the machinery to combine them. It's still the same atoms and molecules, just divided up into two heavy tanks instead of one and needing to expend energy to create the water you need.

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Zomvee In reply to ILJackson [2013-11-12 20:20:47 +0000 UTC]

Well you are right about them being both extremely volatile, but the machinery to combine them isn't even really big since you only need to have a spark to do it so you could make it as small as a remote controlled toy car, and if I remember correctly you can't compress H2O but you can with Hydrogen and Oxygen. If you worry about the dangers of having them in the ship you could build something like a tank on the outside and say 20ft away from the ship and make the side towards the ship thicker, I would think that would solve the dangerous part.

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space-commander In reply to ILJackson [2013-11-03 19:52:25 +0000 UTC]

So basically what you are saying is that the optimal time for a trip without cryosleep is about a week, which I suppose is fairly consistent with the life support requirements for an average Apollo trip.  The main limiting factor is the ship's ability to efficiently recycle oxygen, nitrogen, and water, and this would largely depend on the volume need for an effective recycling system (I am assuming that one of your anchorages would have such a system but a star ship's would be much less efficient). 

Another curiosity that this conjures up is the life support-to-transit fuel cost ratio.  Assuming warp drive as well as most of the other systems on the ship are powered by fusion, one would assume that this overall process requires a fairly small amount of He-3 compared to the mass of O2, N2, and H2O used for life support.

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ILJackson In reply to space-commander [2013-11-04 03:46:26 +0000 UTC]

In my universe, civilian ships generally use Helium 3, which is not too pricy. However it still is more expensive than food, air and water. Afterall, it still needs to be mined and processed and transported, usually from airless worlds. So all that is reflected in the cost. Think of it as we think of oil today. Its traded as a commodity on markets. Worlds that have it in abundance use it to get rich and threaten embargoes when they don't get their way. Refineries are expensive and most of them are worked by guild miners (unions).

Military ships on the other hand, are usually powered by anti-matter, which is very expensive but has a much higher output. It can only be manufactured in exacting conditions that require a lot of power and resources themselves. However, you get far more bang for your buck from antimatter than from Helium, but you burn through it quicker.

So a civilian transport might have a He-3 fusion reactor and during the course of doing the Ysmir Corridor Run and fighting off the occasional pirate, may need to refuel an HE-3 tank the size of a couch once every month. 

But the Crossbow Space Superior Fighter runs off of a 1/2 ounce antimatter lozenge, that needs to be replenished after each mission. A battleship may run off a 2-pound block of antimatter for a week, but carries 10-20 of these blocks in storage. However, each block is about as expensive as about a year's supply of helium 3 but generates 10 times the energy in a shorter amount of time.

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space-commander In reply to ILJackson [2013-11-04 23:05:29 +0000 UTC]

I would certainly expect any fuel to be more expensive kilogram-to-kilogram than food, air, or water, but the real question is total cost compared to total cost.  However, if one is trying to maximize the carrying capacity of a cruiser by carrying a million marines in cryo instead of 10,000-40,000 passenger style like in a Star Wars Star Destroyer then cost of food, air and water would be irrelevant anyway because there simply would not be enough volume on board the ship to accommodate beyond a given population density. 

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