[FlamingCobra]

Ummmmm...... generation ships.

problems:
1. retarded
2. extremely hard to do (self sufficient)
3. won't get there any time soon.

but still possible.

[Nuke]

im curious of how feasable it would be to (eventually) construct a large railgun out in the outer solar system (like on pluto) with the sole purpose of firing small probes at near relativistic speeds at exoplanets and then have them send back telemetry about the solar systems it passes through. if you know enough about the target solar system you could probably get that probe to fly fairly close to the potentially habitable exoplanet. the biggest problem with this would actually be transmitting the data back to earth (maybe a quantum entanglement transmitter) where radio signals and lasers would attenuate greatly after a couple of light years. we know how to build railguns and we know how to get to pluto. this is one of those maybe in the next several hundred years kinda ideas.

Don't see much of a reason behind doing this on Pluto. It's a classic case of using Earth-based spacial and distance awareness in space. Which doesn't work. Why? To move from one point to another on Earth, you need to apply constant force to move in most cases, because gravity, friction and drag will do their best to stop you. If you constantly have to transport something to the United States, then Mexico or Canada make for better departure points than Europe. Because they're closer and you need to spend less energy/resources to get there. Yes.
In space, things work differently. You don't need to constantly apply thrust to keep moving. Furthermore, you can use other gravitational sources to augment your speed  without spending a drop of additional fuel - if you calculate your trajectory well enough.

Two of the most difficult things to overcome in launching a probe are getting the thing in orbit in the first place, and financing the whole infrastructure needed to do it. Pluto would work great with the first thing, as it has a relatively low surface gravity. It would be pretty horrible with the other since the costs and technical challenges of setting up and maintaining the needed infrastructure would be prohibitively high. And there would be no reason. If you don't want to deal with all that pesky atmo and gravity to achieve orbit in the first place, then a Lunar base would serve much better. You don't need much fuel to achieve orbit, and you can use Earth, the Sun and possibly Jupiter/Saturn as gravitational slingshots for such probes. There's no need for a Pluto base just because Pluto is further away from Earth. Once you get going, you set up your transfer orbits and eventually reach solar escape velocity, it's going. A departure point far away from Earth just needlessly complicates matters. You'd probably end up firing probes back inside the solar system that way so you can use the Sun for gravity assist maneuvers to pick up more speed.

The second problem is that rail guns accelerate mass while it's being fired. Once the mass being fired has cleared the railgun, unless it has it's own propulsion unit, acceleration under it's own power is over and it's at the mercy of gravity. This means that to achieve speeds needed for a suggested space probe system you'd need to fire it at incredible accelerations. The G-forces would probably destroy the probe, or at least it's scientific and comm equipment. Rail guns are a "accelerate stuff very quickly to their max speed" kind of systems. For space probes you really want a slow-burning, fuel efficient system that is capable of producing a large delta-v over longer periods of time. You could, I suppose, have a rail gun assisted launch system on a low grav environment such as the Moon, fire a probe to give it initial speed (at an acceleration rate that doesn't tear it apart), and then do delta V with some sort of an ion drive or something, and using gravitational sources to gain more speed. Whether or not we'll ever do that will depend on how the tech advances and whether or not the cost/benefit ratio will go in it's favor.

first off you dont need to tell me how space works. dont worry about launching it (this will require existing in-space infrastructure), that would be impossible  because it would need to be a very large railgun to get a massive object to near relativistic speeds and would probably need a 10th generation nuke reactor to power it. theres math to figure out how big the railgun would need to be and how much power it would need, but i dont want to look it up and do it. i figure to hit such a distant target would need to have very accurate aim, and that entails launching from an area of low gravitational influence, where orbital velocities are about as fast as grandma's driving, and losses from the solar system gravity could be minimized. i used pluto as an example but im sure a further out kuiper belt object would be even better. think of it as the sniper shot from hell, you definitely want to control your breathing.

after some thought i very much doubt an object at relativistic speed would stay in anythings gravity well long enough to adversely effect its trajectory. a launch from a railgun on the moon is likely possible and also doesn't preclude the possibility of a gravity assist from jupiter (though that limits potential trajectories somewhat). you still need to compensate for massive objects (stars, large gas giants) in our solar system as well as the target's. also it would be a flyby, save possible aerobreaking/aerocapture manuvers, and the probe's delta-v capabilities would be rather low, making these difficult or impossible.

probe itself would need to be fairly lightweight. things like an engine or some kind of rcs system (using a 2x2 grid of hall effect thrusters pointing down the z axis with them angled outward from the center about either the x or y axis by a few degrees would provide thrust and 3 axis rotational control, by firing the thrusters in pairs) would be for vernier control only, minor course corrections, and orientation control (to align sensors/antennea), it would not need to be powerful or large. probe needs a sensor device, and some kind of transmitter, a computer to run the show, and needs to be powered/heated for most of the trip. im curious if collisions with particles in the interstellar medium would cause significant heating at relativistic speeds to power some kind of heat differential device. like a stirling engine or thermoelectric cell that you might be able to draw power from/keep the spacecraft alive, or perhaps a small rtg with a decent life span. now fit all this into a package the size of a football (american of course), load it in the railgun, and fire at your target. oh and it needs to survive launch too

let me reiterate that this would be a very long term plan and has many prerequisites that we haven't even got started on yet, and even then only works for nearby solar systems, at half the speed of light 44 years to gleise and another 22 for return telemetry (baring entanglement transmitter), something doable in a human life span. there is also the slow burn mentality where you send out a large probe and have electric engines, reactors, propellant, though it does have the potential to bring more sensor equipment to bear. but a single massive probe sent to a single target i dont think is a very good idea. instead mass produce those tiny football probes, give em all the velocity they would ever need, have em take a photo and a spectagraph and send back the results, then you will know what planets are ripe for sending the larger probes too (or perhaps warships).

[Nuke]

Ummmmm...... generation ships.

problems:
1. retarded
2. extremely hard to do (self sufficient)
3. won't get there any time soon.

but still possible.

go rent cosmos, watch it all, watch it again, and then come back.
according to carl sagan a ship at .9c would experience so much time dilation that time experienced on ship would be within the range of a human life span dispute being able to cross large distances. catch is by the time you made it home thousands and thousands of years would have passed and your planet might not be there any more.  of course, thats not a generation ship.

a more plausable way to make a generation ship is go to the kuiper belt, find an ice dwarf, and build massive nuclear-water rockets pointing skyward, around which you build ice mining camps to produce propellant for them. you can then hollow out the interior and build habitats there. several meters of ice will provide awesome radiation shielding. power reactors could also be built outside so as not to contaminate the interior. one of these days il do actual maths to figure out how much delta-v you can get out of an ice dwarf.

[Dragon]

Wrong. You are suffering from the same misconceptions that the original SETI people suffered from. Let me explain.
[snip]
This means that the chances of catching a civilization in that developmental stage are astronomically low, and establishing two-way communications is practically impossible.

Oh, and of course that is all predicated on having an alien species that follows the same path of technological discovery we did.

I did take that into account.
While technology-based emissions are indeed reduced, scientists are sending signals into space exactly for the purpose of looking for aliens. Assuming the aliens do that too, and noticed Earth as a possible place for life to exist, chances of establishing some sort of contact increase greatly. My post was extremally optimistic, as it assumed many other things would not go wrong. (like aliens having a vastly different definition of life than us or never using EM emissions in first place.) I also assumed that the alien civilization is on the similar (or slightly higher) tech level as humanity and that they also wanted to look for other life forms. In other words, I was considering the best possible scenario.

go rent cosmos, watch it all, watch it again, and then come back.
according to carl sagan a ship at .9c would experience so much time dilation that time experienced on ship would be within the range of a human life span dispute being able to cross large distances. catch is by the time you made it home thousands and thousands of years would have passed and your planet might not be there any more. 

This could be calculated, time dilation would indeed make the journey seem much shorter for the crew. I doubt a planet would go anywhere in about 1000 years, so this sounds quite reasonable. People on Earth, on the other hand, would have to wait a bit for any news from the colony.
Accelerating to such speeds is the main problem, as at these velocities, most of kinetic energy goes into mass. And after getting to the target, you need to decelerate without breaking the ship apart.

[redsniper]

If it can handle the acceleration, it can handle the deceleration.

(Just flip it around)

[Mongoose]

The obvious answer to all of this is warp drive/hyperspace/subspace.  Get on it, someone!

[LordPomposity]

The obvious answer to all of this is warp drive/hyperspace/subspace.  Get on it, someone!

To provide a semi-serious response, somebody already has (warning, pdf).

Background: current estimates put the age of the universe at about 14 billion years, while the radius of the observable universe is about 45 billion light-years. Since the universe began at a single point, you'll probably notice a contradiction here.

The gist of the explanation is this: while relativity prevents any particle, wave, or the like from equaling or exceeding the speed of light, the rate at which space itself can expand and contract is under no such restriction.

What Alcubierre describes in the paper I linked is the metric by which space might be collapsed in front of a ship and expanded behind it to give the effects of FTL travel without actually exceeding the speed of light. His work has been extensively peer-reviewed, and nobody has been able to find any disagreement with established physical laws or theories.

There are only three problems:
1. Alcubierre himself fully expects that some future discovery will probably invalidate his theory.
2. Even if the theory is sound, nobody has any idea how we would actually generate such a field.
3. Even if we knew how to generate such a field, doing so would require more energy than the total output of the sun over its entire lifetime.

[Mongoose]

I was actually thinking of the joke Stephen Hawking made when he guest-starred on Star Trek: TNG.  He was taking a tour of the sets, and when they came to Engineering/the warp core, he stopped and said, "I'm working on that."

[watsisname]

after some thought i very much doubt an object at relativistic speed would stay in anythings gravity well long enough to adversely effect its trajectory.

I think the change in velocity while escaping the planetary or solar gravitational well is negligible for an object traveling at a significant fraction of c.  (Still have tiny corrects for the curvature of spacetime though -- even photons will be deflected to some degree.)  And if it's not negligible, then no big deal... it's a predictable effect and thus no more difficult than calculating the gravitational slingshot trajectories for space probes like Voyager or Cassini.

Come to think of it, though without doing the math to demonstrate it, I'm under the impression that the more significant factor for "aiming" a relativistic interstellar probe are the heliocentric velocity of the object it was launched from, and the relative velocities of the sun and the target star, AND the orbit of the target planet. (How embarrassing would it be to shoot off your probe only to have it arrive when the target planet is on the other side of its orbit!)

So even if we can neglect gravitational perturbations, the relative orbital motions still make it a fairly complex problem, though of course not unsolvable.

[Flipside]

The one thing that does make me laugh about the reporting of this is that most news reporters seem to think that the artists impression of the world is an accurate depiction of it. Science is good, but it's not that good, at least not yet

[watsisname]

Heh, reminds me of what one of the guys working at the Smithsonian Astrophysical Society said in a lecture.

"I had to teach myself how to make celestial artwork on my computer, because the reporters kept telling me they couldn't write about my research if it didn't have any pretty pictures."

[Unknown Target]

My friend and I talk about the sort of generation ship where everyone's consciousness is basically stored on a computer, and they share a general reality that runs at a much slower clock cycle than the rest of the universe; making the entire trip seem like days to them. Once they arrive their bodies are reconstructed using nanobots, which may or may not be included on the ship.

It's really far out there but once you start looking at the mathematics to support human life in space, especially for long durations, the ship starts to become exceedingly heavy, complex, and gigantic.

[Alex Heartnet]

-snip-
2. Even if the theory is sound, nobody has any idea how we would actually generate such a field.
3. Even if we knew how to generate such a field, doing so would require more energy than the total output of the sun over its entire lifetime.

How about using a black hole to power the starship?  All the gravity you would ever need!  And it is better then antimatter for several reasons, such as being not quite as dangerous as antimatter, and not requiring any new physics.

We really need to see one of these get blown up in a sci-fi show, as a change of pace from exploding reactor cores.

[Herra Tohtori]

Burrow deep into the planet.

Attach big thrusters on equator, 100 km+ tall structures that dump propellant (matter from the planet in significant quantities) into space at really high speeds. The higher the speed, the better the impulse, of course.

First, adjust planetary velocity as required to keep at suitable distance from the Sun while it expands. This should extend the useable life time of our planet some, but we'll need to conserve quite a bit of propellant for the Big Trip, too - the one that we'll have to make once the Sun shrinks into a black dwarf that only radiates residual heat.

Once that time comes, we'll have to see if there are any other possible means of survival available.

Geothermal heat should provide sufficient energy reserves for a viable human population living underground. There'll be a temperature gradient between deeper and higher, which can be used to power thermal cycle, and that's really all you need to run a turbine.

Obviously, a planet will travel quite slowly, but it WILL be able to support life long after the Sun dies, provided there's not catastrophic impact event of some sort. The biggest problem, really, is propulsion even at slightest scale, since the energy and propellant requirements are, frankly, quite insane. However, if we can avoid getting swallowed by the expanding Sun, then humanity will be able to survive within Earth for quite a while. If the propulsion problem is solved, then it's just a matter of time to float to another suitable star, which will ideally melt all the frozen water, nitrogen, oxygen and other stuff that basically rains down when the atmosphere cools down sufficiently, and the atmosphere will form again.

Of course, seeds of aquatic and other life would need to be maintained underwater, which might provide unique challenges, but hey, if we can ever figure out how to move an entire planet through space, I'd say that's the least of our worries.


Needless to say, this kind of space travel would take long, long, long time to get anywhere.

But, if you consider the viability of life underground, it's not that far-fetched after all.

In fact, now that I think of it, there may be countless wandering burrowing civilizations...  making them, quite literally, planetary in the original meaning of the word.


The idea does hold some appeal. Technically, we could even convert the planet into some kind of megaengineered space station - some could argue that this happens as soon as the propulsion system is constructed. Some sort of relativistic matter ejectors would probably do the trick... problem would be energy to drive them, and matter to eject.


Coincidentally, these propulsion systems would double as extremely formidable weaponry.

[Nuke]

My friend and I talk about the sort of generation ship where everyone's consciousness is basically stored on a computer, and they share a general reality that runs at a much slower clock cycle than the rest of the universe; making the entire trip seem like days to them. Once they arrive their bodies are reconstructed using nanobots, which may or may not be included on the ship.

It's really far out there but once you start looking at the mathematics to support human life in space, especially for long durations, the ship starts to become exceedingly heavy, complex, and gigantic.

i thought about a cloner ship that would transfer frozen embryos or gamete cells transported on an ai ship. when the ship found a planet that was habitable, it would then use the stored genetic material to grow humans in an artificial womb of sorts. these children would be raised by robots and trained to start a colony. the ship would also come with a number of tools, building materials, farming machines, seed stock, perhaps also genetic material for livestock, everything the would need to start a colony. the ship would land automatically before producing the colonists. such a ship would need a pretty beefy propulsion system to be able to survey multiple star systems that it would take to find a habitable location. it would also take some pretty advanced ai systems to be able to raise children without a lord of the flies thing going on. given the state of genetics it might actually be possible to have the ai tweak human physiology to adapt it to the colony planet's environment.

[Nuke]

Burrow deep into the planet.

Attach big thrusters on equator, 100 km+ tall structures that dump propellant (matter from the planet in significant quantities) into space at really high speeds. The higher the speed, the better the impulse, of course.

First, adjust planetary velocity as required to keep at suitable distance from the Sun while it expands. This should extend the useable life time of our planet some, but we'll need to conserve quite a bit of propellant for the Big Trip, too - the one that we'll have to make once the Sun shrinks into a black dwarf that only radiates residual heat.

Once that time comes, we'll have to see if there are any other possible means of survival available.

Geothermal heat should provide sufficient energy reserves for a viable human population living underground. There'll be a temperature gradient between deeper and higher, which can be used to power thermal cycle, and that's really all you need to run a turbine.

Obviously, a planet will travel quite slowly, but it WILL be able to support life long after the Sun dies, provided there's not catastrophic impact event of some sort. The biggest problem, really, is propulsion even at slightest scale, since the energy and propellant requirements are, frankly, quite insane. However, if we can avoid getting swallowed by the expanding Sun, then humanity will be able to survive within Earth for quite a while. If the propulsion problem is solved, then it's just a matter of time to float to another suitable star, which will ideally melt all the frozen water, nitrogen, oxygen and other stuff that basically rains down when the atmosphere cools down sufficiently, and the atmosphere will form again.

Of course, seeds of aquatic and other life would need to be maintained underwater, which might provide unique challenges, but hey, if we can ever figure out how to move an entire planet through space, I'd say that's the least of our worries.


Needless to say, this kind of space travel would take long, long, long time to get anywhere.

But, if you consider the viability of life underground, it's not that far-fetched after all.

In fact, now that I think of it, there may be countless wandering burrowing civilizations...  making them, quite literally, planetary in the original meaning of the word.


The idea does hold some appeal. Technically, we could even convert the planet into some kind of megaengineered space station - some could argue that this happens as soon as the propulsion system is constructed. Some sort of relativistic matter ejectors would probably do the trick... problem would be energy to drive them, and matter to eject.


Coincidentally, these propulsion systems would double as extremely formidable weaponry.

your thrust velocity needs to be greater than escape velocity or you create a situation where reaction mass turns around and falls back to earth, giving you no net velocity change. once you leave the habitable zone you have a limited time to reach your destination before your planet looses its heat. on the plus side all you need is to find a new place to park and you already have everything needed to restart the ecosystem (which you will likely destroy in the process).

im less concerned with the sun increasing its output because it might provide enough energy to re-heat mars before it melts the earth, and that we may planet hop all the way to ceres as the sun heats up further. ceres could be heated up by slamming asteroids into it as a precursor to transforming. especially ice bearing bodies like comets and stuff from the kuiper belt.

[Mongoose]

I'm gonna go out on a limb and say that a ship full of frozen embryos destined to be flung onto some alien planet and raised by AI to survive there brings up some massive ethical issues.  Not that that's something you'd concern yourself with, of course.

[deathfun]

Because **** decimals.

Long live significant figures!

[Nuke]

I'm gonna go out on a limb and say that a ship full of frozen embryos destined to be flung onto some alien planet and raised by AI to survive there brings up some massive ethical issues.  Not that that's something you'd concern yourself with, of course.

the idea is you let them get a planet going so later on you can send in the warships and invade them, horke their stuff, bang their women, and enslave them.

[redsniper]

We should abandon planets and instead live on comets. Life originally came from comets anyways, so it's only fitting we return to them. Then where the cometary halos of other solar systems overlap, we can jump over to new comets and (very very slowly) expand throughout the galaxy.