Slowboats

I've been having a discussion about slowboats with Thalaba over on the RPG Haven which you may find interesting:

Thalaba:
What technology propells these slowboats? What fuel? I assume they spend most of the trip drifting with the occasional course correction?

clash:
It's a fusion torch, fueled with deuterium - heavy hydrogen. They build up speed with a long slow burn over time to a fraction of c, drift for centuries, turn, then brake into the target system.

Thalaba:
Incidentally, what are the by-products of deuterium fueled fusion? Are they using the same reactors on Earth to generate electricity?

clash:
Helium, mostly, with other light elements like lithium as traces. Yes, energy is cheap and abundant in the Solar system.

Thalaba:
Are the people inside in suspended animation? All of them? Are the crews on rotation? If so, how much to the crew memebers age while the rest do not?

clash:
Most of the ships use a cold sleep technique which is a low-temperature hibernation, where the sleeper ages one hour in 20. The passengers are awake in decade-long shifts, with the vast majority being asleep at any given time. These shifts are generational - even with a one-in-twenty dilation, plus some relativistic dilation, the passengers age too fast to survive a substantial portion of the trip. The Passengers were the crew, though most of the passengers were busy teaching, learning, growing up, having children, and having as normal a life as possible.

The last few ships used a new cold sleep technique, where the passengers did not age in cold sleep. These passengers survived the entire trip from Earth to the Cluster, and they had a separate, much smaller, generational Crew which spent the voyage in shifts, though since they didn't age in their sleep times, they lasted far longer into the voyage.

Thalaba:
(Suggestions) Other uses of cryo technology back home:
Illness: Freezing the terminally ill.
Jumpers: People with a sense of adventure and enough money to freeze themselve for the sole reason of getting to the future to either a) see what it's like, or b) cash in on investments without having to spend all that time waiting for them to mature.
Livestock: Frozen while still alive to either store them until they are needed for food, which might have a stabilizing effect on the markets and lead to 'cattle vintages', or to transport them to the colonies so fresh meat can be had.

clash:
Makes sense, but 1 in 1000 die from the process, so it's a bit of a lottery. The later cold sleep is safer, with only 1 in 10,000 dying.

Thalaba:
What about life-support systems? Is the organic system inside the ship completely recycled, or does it accept inputs (presumably from storage). What happens to waste?

clash:
The assumption is that there will be loss, because no system is perfect, but with much better efficiencies than we can maintain.

Thalaba:
This suggests that bio-recycling systems back home should be much improved, leading to a cleaner environment.

clash:
Very much so!

Thalaba:
What about energy - is there a net gain, net loss, or a constant amount of energy over 1200 years? I'm having trouble believing a ship travelling that long would not suffer some sort of mishap that could lead to catastophe if the systems were finely balanced.

clash:
There is always a net loss. Energy is maintained by a fusion reactor - not the big torches - which uses the same fuel as the drives. Albert Bailey designed this "slowboat" system with me, and he is an actual rocket scientist - a plasma physicist. The drives and energy are the part we have the most faith in.

Thalaba:
One reason I ask is that the technology required to send a ship over such a long distance would surely drive domestic innovation, too.

clash:
It certainly would! Not only is the better "Cold Sleep" introduced later in the process, but the ships themselves get better and better - faster, better designed, and more idiot proof. The last ships to get out are actually the first to arrive, as their transit is faster. The first ships to leave have not yet arrived. The later the ship leaves, the more certain it is of getting to the Cluster whole.

Now some ships die out, going silent on the long journey and never braking. On others, society melts down and people revert to a kind of savagery in the halls, leaving the ships on robotic autopilot. All kinds of mishaps occur! Systems - not just technological, but institutional and cultural - evolve to enhance the likelihood of arriving. There are more than enough ships sent to assure that some will arrive.

Thalaba:
Very compelling stuff. Do the slow-boats communicate with one another while in transit?

clash:
Yes, they do, via radio waves, correspondingly doppler shifted as required. When a ship falls silent, the other ships will know that either the culture aboard has degraded too far, or that no one is alive. While the faster ships pass the slower ones, the pace of communication speeds up, then slows as the light speed lag decreases and increases. The steadiest communication is between ships launched at about the same time, with the same relative speed. At a certain point, it's useless to try to talk with ships light-lagged years or decades ahead or behind you, though.

This Diaspora is a central factor in all the descendant humans of the Cluster, like the journey of the Mormons to Utah, only extending for centuries. The necessarily static shipborne cultures had troubles when they finally got to their goals, as well. Static cultures do not thrive in an open and unfamiliar environment.

-clash