My G-G-Generational Ship

I’d christen it “Golgafrincham Ark B”.

That’s something I was wondering → will money even work? If the planet is doomed in a decade, will money have buying power any more? I know I wouldn’t be concerned with a wad of green printed paper, if it was going to be worthless shortly… How long before we collectively stopped valuing the dollar? 10 days before Earth is doomed, 10 years?

Unfortunately, I think the concept of a generational ship rules out planoforming.

Launch ten years from today? No. Can’t be done. We might be able to get the governments of the world to agree to work together on the concept in two or three years.

What possible evidence could arise TODAY that would convince most of the reputable scientists of the world as well as most of the disreputable politicians if the world that we have to abandon the planet within ten years to preserve the human race?

And since only a very miniscule percentage of the population will be able to get away (I don’t include myself among them), why would the rest of us sacrifice to get this huge ship built?

If the world is going to blow up in ten years, I would rather spend the time partying than working like a dog to give 10,000 strangers a chance to survive it. Maybe we should spend those resources making things as pleasant for ourselves as we can in the time left.

Well, it’s a good question. Basically, money represents labor. People will still have to eat, have electricity, running water and the like. If they want those things, they will still have to work. In the end, I think most people will choose to want to live as long as they can. Some will choose to die in their own way and own time, and some will choose to just give up or party like it’s 1999, but I think most will choose to try and live as long and as well as they can…which means that money is still going to be viable, at least initially. Even if ‘money’ stops working before the end, it’s just a representation of the concept of labor or material goods, and that will still exist. So, if say the dollar collapses (which I doubt will happen until close to the end), the representation in goods and services of the ‘money’ is still valid…and can and will still be used to build the ship.

Like I said, 10 years is too short a time. It’s too immediate, and there are too many hurdles in that time frame for any chance of success. Just getting through the political aspects would be next to impossible, let alone starting to address all of the other issues. More realistically would be something like 50 years or maybe even 100 years…the further out, the more chance of success, since people will want more stability for longer periods of time the longer out it is. For instance, if it’s 50 years out, it’s not really going to effect ME…I’ll be dead by then anyway. It will affect my children and their children, so I’d still want to do everything I could for them in the mean time…and unless I want them to starve and die right now, that means I have to keep working and producing.

Ten years is about right for the panic-mode preparation of a Mars colony that could possibly be viable for some years. No way could it suffice for what the OP proposes.

Why can’t we brute force it? There were 72 orbital launches last year, each with a payload measured in tons. The human race, with less than a third of the population, was able to manage nearly twice as much during the space race. We don’t need Saturn Vs. Yeah, they’d help, but we don’t have them and almost certainly can’t make them in time so tough shit. What we can do is mandate every launch worldwide to this effort. Ramp up production lines and cancel all unneeded services, redistributing as much employment as possible the space effort. The planet is fucked, so fuck the planet - minimal safety and environmental hazards. So what if everyone might get cancer in 10 years? They’re all fucked in 10 years anyways. Redistribute all government efforts, squeeze money and work from everyone, and everyone will go along with it too for the hope that they or their kid will get a chance on this ship.

Which brings us to another uneasy issue - crew. We can’t launch thousand of people. We probably can’t launch hundreds. 80 seems a more realistic goal. Being such an extreme bottleneck genetic testing would be mandatory, so would eugenics-like policies we’ve learned about breeding from breeding other species back from the brink. Even so, for dozens of generations things will be tough. On top of that, send short people, skinny people. Average Asian weight is 127lbs, in space with less muscle we can reduce that to 120lbs a person.

We focus a giant deal of our launches on water. We won’t be able to pick some up in between, so we have to take it with us. Use it for general shielding, both from radiation and micrometorites - many feet of solid ice won’t stop everything but it’ll make it harder to be punctured from within or without.

We launch multiple nuclear power plants, the kind already in production for nuclear subs and ships. Use ion thrusters or similar propulsion. Everything else may fail but we won’t run out of power, for lights, heat, ect.

Which bring us to the things that probably will fail. The closed loop system. We have nothing remotely close to what is needed, so we need redundancy in the extreme, which costs more launches, which we may not be able to spare. It doesn’t matter if the food is boring, send the highest calorie longest lasting densest foods and vitamin supplements we have. We’ll need seeds, and if possible animals (small chicken, fish, insects), and a small garden on ship for recycling waste, as well as importing needed soil bacteria, fungi, ect. And the society. Studies on such have been minimal, and predicted results bad.

All of this necessitates a short trip. In the meantime one program we keep operation are the planet hunting programs, and boost them up in every way possible. Focus only on nearby stars. Use every trick possible to dig every clue possible out of the atmospheres. Truth is, unless there’s already an oxygen atmosphere with no lethal trace elements, and fresh water, we’re screwed no matter what, because we’re nowhere near able to terraform.

So assuming 100 launches a year (less now, more later when production ramps up), 3 tons a launch, and 10 years, we’d have 3000 tons in orbit. Even skimming on everything, cutting corners where possible, and dedicating the efforts of the entire species, can we not come up with even a 5% success rate?

We cannot in the next ten years get a generational spaceship heading toward anyplace that it would ever arrive at with anyone left alive on board. If nothing else, that saves us from having to find someplace to go.

The Hail Mary.

Putting aside the engineering issues, I say we aim for Tau Ceti. It’s a Sol-like star, planets have been detected in its orbit, and it’s relatively close at twelve light-years.

Given that it must by design be filled with young people, why not Baby? Bassinet? Cradle?

Agreed. Also, how did I miss this thread? :slight_smile:

Fifty or a hundred years, maybe. Not ten.
Better to solve the impending doom some other way.

As mentioned upthread, you need a closed ecosystem, that’s a huge hurdle.
Not impossible, just something we can’t do right at the moment.
You’d need fusion power too, no way chemical rockets would suffice.

And the ship has to have facilities to make anything on teh ship.
Every part of every system, you need to be able to make that while traveling.
Modern aircraft carriers have the ability to some extent, but you would want 100% ability for a generation ship.
Doesn’t have to be fast or automated, but you need a machine shop and a semiconductor foundry.

Aiming the ship would not be done when it is launched, rather, some ten years or so later, when it has entered interstellar space. It is generally believed that the galactic core area is probably not a sensible direction, but once a ship is out of the solar system, it seems likely that their survey equipment would be more effective, without having to deal with the local noise. Escape from the system might possibly be aided or accomplished with sails or somesuch, so accelerating in a specific direction would then begin to use onboard fuel. Since it will take generations, the turn could be slow enough that it would not use too much extra fuel. Hopefully the passengers can avail themselves of some sort of hibernation technology, sleeping for months at a time interrupted by a few weeks of being awake and active, in order to reduce the demands of life support, though it is not entirely obvious that hibernation would use enough less energy to pay for itself.

Cool! Let’s call it Boatmurdered.

We already did that, a couple billion years ago on our way to Earth. Remind me why we haven’t been using that ancient stored knowledge?

10 years almost certainly isn’t enough time, but this is what I think we should do (I’ve offered this before in similar threads):

Send automated seedships- dozens of them or more, towards stars in all directions, with enough smarts and sensors to land on suitable planets that they come close to. These ships have no humans on them- just human DNA (or sperm and eggs, or even fertilized embryos). They also have bacterial spores, seeds, and eggs and other genetic material for most kinds of life on earth that is at all useful to humanity.

When the ships find a suitable planet, they land and activate/release their life in waves, starting with microorganisms to aerate and prepare the soil and fish and sea-life into the oceans, then basic plants and animals that the plants need to survive (earthworms, bees, etc), then more “advanced” animals and plants, and finally after the hundreds or thousands of years it takes for this brand new ecology to settle down into an equilibrium, the ship’s robots will grow the first people (in artificial wombs of some sort), teach them how to be humans using recordings from “old Earth”, and release them into the wild new planet.

That’s, uh, space travel doesn’t work that way. You’ve necessarily got a limited budget of fuel because you’re not going to get any chances to top off once you’re up and going, so you want to make every last drop count. This means every bit of thrust used to make course adjustments is thrust you can’t use to go forward faster. It’s much much much better to point yourself in the right direction at launch than it is to wait a decade before figuring out where to go and making a 30° course adjustment. There’s the matter of the Oberth effect, which basically says that the faster you’re going the more efficient additional thrust gives you, so that’s another reason to burn early and precisely. And then there’s gravity assists which can provide huge boosts to velocity for free but require careful flight planning. You really want those extra 13+ km/s to point you in the direction you want to go, rather than just “eh, wherever.”

If you’re using something like an Orion spacecraft you can probably brute-force anything, but there’s still no reason not to plan ahead and use gravity assists pointing you in the right direction to get there faster.

Also, looking at those gravity assists that Cassini went through, it might make sense to crew the generation ship with a skeleton crew and send it through years of inner-system gravity assists, then populate it later with a small and extremely powerful supply ship. I’m not sure what benefits you get by shaving three years off most people’s time in space, but it sure makes things nice and complicated! It also probably plays hell with the ten-year deadline.

I’ve always figured the crew would be kept busy breeding and raising more crew.
You start out with a relatively initial low population, maybe 1000 on board when you leave the L5 construction site and head to Jupiter. Once in orbit at Jupiter, you start filling hydrogen tanks, bringing farm modules online, and add the rest of the starter population, bring it up to 2000 or so.

After 5-10 years harvesting fuel and reaction matter (and other gases such as methane and ammonia) it’s time to head out. That time give the initial crew time to adjust to shipboard life, anyone unstable can be weeded out. But that whole time, the population will be growing. You’d bring eggs and sperm from Earth so that you could maintain genetic diversity.

There are a number of reasons why it is simply not feasible to construct and launch a “generation ship” of the type depicted in science fiction including those already listed (inability to sustain a closed cycle habitat indefinitely, the lack of high volume super-heavy-lift payload-to-orbit capacity or infrastructure for in situ construction of a vessel in space, having a portable energy source which could provide power for the thousands of years necessary for an interstellar transit, et cetera) but the two most damning and essentially irresolvable without major technical breakthroughs are propulsion and thermodynamics. You won’t see these mentioned in fictional literature, either out of ignorance or because they are simply too difficult to deal with; instead, authors invoke technomagical solutions (such as the matter-energy converter in Heinlein’s Orphans of the Sky) or just ignore the completely (Niven’s Known Space slow ships), but the reality is that we are unlikely to travel to other stars in embodied form short of some massive retooling of physics as we know it.

As every freshman physics student discovers, rocket propulsion (regardless of power source) requires that you eject mass rearward in order to make the vessel go forward, maintaining conservation of momentum per the rocket equation. This means that some of the initial mass of your vessel includes this material, which is generically called propellant. In the chemical rockets that we use to launch satellites into space this is composed of fuel (such as kerosene, liquid hydrogen, or some form of hydrazine) and oxidizer (typically liquid oxygen, but can be stabilized nitric acid or even more exotic substances) which also provide the power source in the form of exothermic chemical combustion which heats the products to high temperatures and pressures, forcing them out the nozzle. Nuclear thermal rockets are more of the same, except the propellant is generally hydrogen (favored in vacuum for the low molecular weight). Other systems, like fission fragment, fissionable salt water, nuclear pulse propulsion, et cetera use other propellants such as the fission products themselves combined with water or other propellants, but in the end, there has to be mass ejected in order to effect a change in momentum.

The efficacy of propellants, called specific impulse (I[SUB]sp[/SUB]) is measured in terms of thrust divided by the rate of consumption by weight or mass of propllant per interval of time, giving a mass-independent result in units of seconds. The best chemical rockets have a hard time achieving an I[SUB]sp[/SUB] of 400 seconds even with the best possible mass fraction (mass of propellant over the total gross liftoff weight of the vehicle). Nuclear thermal may give on close order of 1000 seconds. Fission fragment and nuclear pulse propulsion could potentially offer up to around 5000 seconds. Using a hypothetical nuclear fusion power source at temperatures up to 100,000,000 Kelvin could give specific impulse (using diatomic hydrogen as the propellant) of somewhere around 10,000 to 20,000 seconds. By comparison, to have a vessel with a reasonable mass fraction–say, 1 kilogram of spacecraft/payload to 1000 kilograms of propellant–capable of achieving even a small percentage of c would require a specific impulse on the order of 100,000 seconds. Anything less will strand the spacecraft and its hapless inhabitants in the interstellar void for thousands of years. This capability is radically beyond anything we could hope to develop in ten years, or indeed, likely within the next century, and would require some kind of fundamental breakthrough in either energy or propulsion, it just isn’t feasible to send any craft, manned or unmanned, to another star in less than millenia.

The other major issue is the devil that pops up to cause no end of trouble in every area of natural science, thermodynamics. Specifically, the inevitable buildup of heat–not just from this energetic propulsion system, but also from all the other life-sustaining and vehicle maintaining activities–which has to be transferred away lest amount of the heat and thus temperature of the system keeps increasing until it physically breaks down. On Earth, this is not problem; the air and water carry heat away by convection, and the Earth as a whole spends about twelve hours a day radiating all of the heat energy it absorbs from the Sun (except for that used in driving the hydrological cycle) which dwarfs the production by any human activity (provided we don’t significantly alter the composition and resulting emissivity of the atmosphere). In space, however, the only way to reject (get rid of) heat that is produced without having to exhaust more mass to carry it way is to radiate it away. Also the space background is very cold (at 3.7 Kelvin) for a vessel of any significant volume the amount of radiative area required to exhaust excess heat is going to be huge, not withstanding all of the systems needed to convey heat to the radiators. Basically, the vessel would consist of a habitat of some suitable size surrounded by a giant spheroid bubble of radiating surface. Let the temperature go 30 Kelvin below or above optimum, and everybody onboard dies.

This is not a theoretical problem; spacecraft, which have much higher tolerance to temperature than people, have to be regularly rotated (the so-called “barbeque roll”–I swear I am not making this up) or actively cooled, and the Shuttle Orbiter of the now retired Space Transportation System always had the cargo bay doors open in orbit not because it looked cool but so that the radiators on the inside could keep the Shuttle at a liveable temperature. These systems are good for missions of limited duration or low energy output, but for a habitat of indefinite duration that has to produce food, distill water, and propel itself it becomes a massive hurdle which is not readily overcome by any kind of brute force methods, e.g. just make it bigger or throw more power at it.

The practical problems of actually lifting or constructing such a vessel in space, getting the political wherewithal to coordinate and sustain such and effort, deciding who and how to crew it, developing the means to achieve near unity recycling, et cetera can conceivably be worked with some reasonable extension of existing technology and scaling the system to a sustainable level. But the above two issues will require developing fundamentally new technologies or innovations in basic science which are not even on the horizon, and we have no idea when or if they will ever come to pass.

It should also be pointed out that it is unlikely, baring some beyond-magical ‘warp drive’ technology, that we could outpace any calamity which would threaten the entire Solar system (e.g. a gamma ray burst or cosmic dust cloud) or that we would successfully located a truly habitable planet within a reasonable range. Even finding an Earth-sized rocky world within the theoretical habitable zone around its star is not sufficient; we would need to find a world which has an atmosphere something like Earth-like composition, with an axial tilt not terribly extreme or unstable, a rotation rate that provides a reasonable heat-cool cycle (no tidally locked worlds or those which spin so rapidly that your eyes barely adjust to the dark before the next dawn approaches) and any number of other conditions necessary to support life. Otherwise, we may just as well plan to remain in space indefinitely.


Manned, you’re almost certainly right, but unmanned? A couple small, highly redundant probes, with thousands of tons of fuel, spending years slingshotting between plants/moons/the sun to build up momentum, could theoretically return signals from another system within the lifespan of a civilization, right?