And, as such, nobody should even bother looking into the technologies that may allow this into the future? There seems to have been a lot of that in this thread.
-Joe
Where?
No, what I believe he’s saying is that there is little practical purpose in planning on highly speculative technologies. We should focus on what can be done with extensions of existing technology (robotic exploration of the Solar System, efforts to improve our technology and our understand of habitation in space) rather than spin wheels trying to develop or plan on far-out, highly speculative capabilities (cryogenic suspension, warp drives, et cetera). Once we can crawl, then we can think about taking a few unbolstered steps, but to continue the metaphor right now we’re barely able to hold our head up and look around.
Stranger
I disagree. I think if cost wasn’t an option, and risk wasn’t factored in, we could certainly get living humans to the nearest star (not that this would do much good as, IIRC there isn’t anything at the nearest star worth going there for).
Lets do a run down of our current technologies and see. Can we move stuff into orbit? Yep. If cost isn’t a factor, we can move a LOT of stuff into orbit…enough to build one huge ship in fact. Check. Can we build a self sustaining completely closed ecological system? I don’t think so. We might be able to get something like 70% efficiency if we REALLY pushed, but lets say we can get 50% as a conservative estimate. So, we would have to solve that problem of the short fall. How? Well, one thing we could do is launch a series of unnmanned supply ships on the same trajectory we plan to take in the finally manned mission. Time and money aren’t factors, so we can take 200 years or more to do this project and it can cost what it costs.
Ok, that should take care of the supplies, spare parts, etc. We need to solve the problem of radiation next. How? Well, we are building in space and money isn’t a factor. I’d say that we could put a water jacket around the entire exterior (this will also serve as the water reserve, though of course we’ll be recycling and have those supplies to make up the short falls). Couple that with perhaps an electro-magnetic field around the ship and maybe just plain lead shielding around the crew areas. Probably won’t be 100% shielded, but I doubt the crew will die off before they can breed, and thats all that counts. Risk isn’t a factor after all.
We’ll be doing a generation ship of course, so we need young couples of known fertility AND their children. I’m not sure what the optimal crew size would be, but lets say 100 breeding pairs with another 50 children…crew of 250 then. We’d need all the various technical skills from all the adult crew members…shouldn’t be too hard to get. And of course the crew itself would need to be cool with the fact that life expectancy would be WAY lower than staying here on earth…maybe only something like 40 years tops.
Power? Simple. A shit load of fission reactors. Resupply of the fissionable material will be in the resupply ships let off ahead of the manned ship.
Propulsion? Well, my thoughts on that are a combination of solar sails (especially for the unmmaned ships), a scaled up Ion type drive and the use of an Orion style propulsion system (since someone brought it up earlier and several people said it wouldn’t work). We have enough fissionable material on earth to make quite a few 1MT fission bombs to be tossed out the back of the thing, and price and risk aren’t factors. We ought to be able to get some fairly significant speeds out of the combination drive…and none of that technology requires a single extra component that we’d need to develop.
The ship would be massive…completely over engineered, full of as much redundancy as we could put into it. It would have machine shops, labs, hospitals…everything needed to sustain the crew and ship on a very long voyage. The trip would take generations…hundreds or even thousands of years. Since the ship would travel at a specified rate, and since the unnmanned resupply ships would also travel at specific (slower) rates (or some on simply ballistic trajectories) there should be a constant resupply of needed materials (fisionables, water, perhaps food, parts, etc). After the final launch (perhaps a few hundred years after the project starts) new resupply ships could perhaps also be sent out if newer, faster propulsion systems are found…but when the ship launches it should have everything onboard or already in flight for what is needed to achieve the goal of getting to a distant target star.
We could do all this NOW…if the world was willing to put everything it had into the effort with cost and risk not factors. There is absolutely nothing that would prevent my scenerio from working (though of course I’m sure others could refine it better, fix probles like if you would need 10MT or 100MT bombs out the back or other things, or add features or other improvements…this is all just off the top of my head mind you) with todays technology.
The only reason its impossible is that cost IS a factor, and risk IS a factor…and you can’t get even the US and EU to cooperate on such a venture, let alone literally the entire world. But from a technology and problem solving perspective there is nothing preventing us from sending people to a distant star with our existing technology.
-XT
What about the space debris I mentioned? At the needed speeds, anything at all will destroy the ship or at least damage it severely at just the first strike. You can’t really shield against anything larger than a grain of rice because we don’t have material that can withstand it. We can’t manuever away from things with existing technology either because we won’t see small debris it in time.
We’re not going to be going at relativistic speeds (as we speculated earlier with speeds such as .1C)…it won’t be as much of a factor. Put a huge shield in front made out of the strongest materials available. We don’t care how long it takes or what it costs to make after all…over engineer the thing 6 ways to sunday.
-XT
By the time you’re up to the kind of speed you seem to be describing the vessel would be in the intestellar medium… and really there isn’t anything out there to hit. We’re talking a few molecules of hydrogen and helium per square meter, max. I mean, it’s kind of like talking about starting a voyage from Murmansk in fall and ending in Tierra del Fuego for their late fall. You want to start out slow because of the possibility of hitting berg ice but once you are out in the open Atlantic it’s not really a danger anymore. When you get close to danger again, slow back down. I also don’t think a grain of rice sized object will be quite as destructive as you think. I did some calculations and at .10c striking an object with a mass of one gram will release the energy equivalent of 107 tons of TNT… that’s pretty huge… yeah, but with the time of hollowed asteroid/comet generation ship I’m envisoning it would be somewhat like having a moderate earthquake here on earth I would think. The number of objects in the interstellar medium with a mass of a gram or more is less than a trace number… really really rare.
I’d like to see your estimate of how much food it woul take to supply 250 people for a few thousand years. Granted that you’ve stipulated that cost isn’t a factor, but there will have to be a limit when you approach what the entire population of the Earth can provide with the resources we have available, and still feed and clothe themselves.
Space debris is still a bigger problem that just making bigger shields will address. That adds to the weight and complexity. What about the energy requirements? I don’t think there’s enough energy available to get all that stuff in orbit and propel it to the nearest star, plus have enough fuel for them to slow down.
You use words that indicate that it’s just a question of applying more resources to the problem, but it really is a deeper problem than you’ve acknowledged. Nothing is infinite, especially not here on Earth.
How big is the volume of space that this ship would pass through on the way to another star?
Pretty big in human terms, but in the scale of interstellar space? Vanishingly small. A cross section of a kilometer or two perhaps… over a few lightyears. A veritable thread between the stars. Again, nothing that a hundred meters of iron/nickel or water ice couldn’t handle.
Well, there are actually several, but let’s start with this one:
-Maintaining all shipboardf systems, including working nuclear fission power plants for thousands, or tens of thousands of years. Can we do that? How?
I agree. Although the technology for colonising other planets is quite a but far fetched, it is the most logical step.
There are so many ways the Human Puplation can end, wether it be a meteor, the expansion of the sun into Red Giant, over-poplation, etc.
Maybe NASA, and other space-related companies ought start thinking about this option, even if they do it in a “distant” manner.
Go back 150 years, and tell a person you have an Ipod-like device in which you could hear music from a slim box, or tell them that you can take an Airplane and head to Australia in less than a day, and they’d call you crazy.
It’s best to think that this could be a possility at the very least.
XT the biggest problem with your theory is that the unmanned rockets have to be sped up to the speed the colony rocket is going. Which means you still run into the propellant problem:
ie http://www.nasa.gov/centers/glenn/research/warp/scales.html
"Here are four examples [large graphic] of what it would take to send a canister about the size of a Shuttle payload (or a school bus) past our nearest neighboring star…and allowing 900 years for it to make this journey.
Well…If you use chemical engines like those that are on the Shuttle, well…, sorry, there isn’t enough mass in the universe to supply the rocket propellant you’d need.
So let’s step up to next possibilities, nuclear rockets with a predicted performance that’s 10 to 20 times better!
Well…it’s still not looking all that good. For a fission rocket you would need a BILLION SUPERTANKER size propellant tanks to get you there, and even with fusion rockets you would still need a THOUSAND SUPERTANKERS!
Even if we look at the best conceivable performance that we could engineer based on today’s knowledge, say an Ion engine or an antimatter rocket whose performance was 100 times better that the shuttle engines, we would need about ten railway tanker sized propellant tanks.
That doesn’t sound too bad, until you consider that we didn’t bring along any propellant to let us stop when we get to the other star system…or if we want to get there quicker than 9 centuries."
And thats for Alpha Centauri - 4 light years. So those unmanned rockets would need those kind of fuel amounts for every shuttle load you’re trying to get to your colony ship. The payloads just get literally astronomical.
Otara
Sorry missed the solar sails bit - all I can say to that is consider what size sails they’d need to be for any reasonable sized payload, let alone something like an asteroid. Also the acceleration would be so low that my bet is you’d be talking multiple millenia instead of 900 years just to get to AC.
And we havent even successfully used this technique yet for something that weighs 100kg as far as Im aware.
Otara
This is a common theme in this thread and it’s nothing much more than a tiresome argument by analogy. Just because people in the past might have thought iPods crazy, doesn’t mean any crazy thing we currently choose to point our fingers at will become true in the future.
Of course not, my example does not prove anything other than it’s best to be open-minded about the possibilty of some sort of “super-technology” being developed in the future.
To say that it is imposible to conquer other planets, or to say that it is a complete waste of time is ignorant, In my opinion.
Solar sails (assuming you could make a material light and resilient enough for the purpose) are fine in the insystem, but beyond the orbit of Saturn the photon flux from the Sun is small enough that you might as well just get out and shove.
No matter what kind of propulsion you use–chemical, pulse fission, ion, fusion, antimatter, whathaveyou–you still have the limiting case of the mass of propellent; you have to carry not only enough propellent to get you up to speed, but have to carry enough to boost the extra propellent you’ll need to slow back down. Even with conceptual high impulse drives using fusion or antimatter, the this produces a very constrained limiting case on how fast you can go. A back of the envelope calculation based upon a average specific impulse of 100,000 seconds (vastly in excess of anything we can do currently and on the upper margin for expected specific impulse from a fusion-based motor) requires a mass ratio on the order of 1000:1 for fuel[sub]acc[/sub]:fuel[sub]dec[/sub]. Multiply this by the required impulse to accelerate and deccelerate your actual craft (engines, lifesystem, provisions, ablative shield, et cetera) to the desired velocity in order to get an idea of how much mass of propellent you’ll need to carry. Unless you are prepared to almost literally inch your way to the next system, the requirements are prohibitive.
If you can create a system that doesn’t require carrying the propellent–say, throwing the propellent out in front of the craft to be collected later, or a system with a fixed laser pushing the ship via a lightsail–then you be a little more reasonable, but such systems are highly speculative. To say that we can do it with existing technology, at any cost, is just plain wrong. Could we do it someday? Possibly (I would like to think even probably), but most likely not in the form that you imagine, i.e. carrying animated bags of contaminated water across the void.
Stranger
The people saying it is impossible (or practically so) are describing genuinely huge problems; Ignorance is when people wave those away and say “oh, but we’ll just solve that - I don’t know how, but I’m sure we will”
Yes, we can’t stay here forever and I’d like to think we are capable of more. I doubt we’re anywhere near close to being capable of such an accomplishment just yet but we are certainly heading in that direction.
xtisme, you may be interested in this article a 200+ year life span may not be impossible.
The people saying heavier than air flight is impossible (or practically so) are describing genuinely huge problems; Ignorance is when people wave those away and say “oh, but we’ll just solve that - I don’t know how, but I’m sure we will”
Do you doubt our ability to solve problems?