Wikipedia has a good section on this. It estimates 44 years to get there with the Orion probe.
Project Orion (nuclear propulsion)
There's also this intriguing idea, which I found from that article:
Use of Mini-Mag Orion and superconducting coils for near-term interstellar transportation
It's actually about an idea to send a stream of mini solar sails - just a pellet in a Mylar sheath - as a way of refueling an interstellar spaceship in flight through its acceleration phase from Earth. You don't get spreading of the beam as you do for laser transferred power - so can do at high efficiency during the acceleration phase.
You could just use the momentum of the solar sails for acceleration, as in this earlier concept by Jordin Kare Sailbeam (slides) - Paper (to get an idea of how it works see the Figure 1: SailBeam Concept in the paper),
Jordin Kare thinks there's a chance you could manage 0.1c or faster with this method.
But the authors' idea in Use of Mini-Mag Orion and superconducting coils for near-term interstellar transportation is that it's more efficient to send fuel for the spaceship rather than just use it for momentum exchange.
For decelerating, the spacecraft generates a magnetic field which acts as a brake against the solar wind of the destination star. In this idea, it uses a superconducting coil to generate the magnetic field
It's a Magnetic sail
A similar idea to the MagSail is the Electric sail (or e-Sail) which is being investigated by the ESA as a way to propel spacecraft to the outer solar system, it uses many thin wires spreading out from the craft, and an electron gun in the centre fires electrons away (shown blue below) thus creating a current which flows in from the wires to the centre - this creates a magnetic field which makes an obstacle to the solar wind - rest is as for the MagSail, here is an artist's impression.
Paper about esail - Slide presentation about it
The paradoxical thing about interstellar travel is that so long as the timescale is of order of centuries, it's worth your while waiting for the technology to improve as otherwise later departures get there before you - until the time required goes down to a few decades. But if timescale was just 44 years, could be worth setting off right away.
Surely unmanned probes first?
An even faster way to get there is being explored at the University of Michigan, the Nanofet drive, which fires small particles at close t the speed of light designed for tiny spacecraft
Nano-particle field extraction thruster
Theoretically these could let nano spacecraft fly at almost light speed - and larger craft also
Firing Off Charged Nanoparticles Might Allow Spaceships to Move at Near-Light Speed
Though there would be many practical issues with a big spacecraft going close to light speed through the interstellar medium, .
Another more way out idea being researched, Quantum vacuum plasma thruster
- idea is - to separate out particles from quantum fluctuations on the vacuum and accelerate this as your reaction mass so you don't have to carry it with you..
and lots of other ideas.
Personally I'm not at all sure we should colonize the galaxy, though great to explore it. The problem is, that if, as the author of that paper suggests, humans fill the galaxy quickly, say in a million years or so, then - what would all those humans turn into?
We worry about aliens invading Earth. But it's pretty clear that no alien species have colonized our galaxy yet, and it would be just an extraordinary coincidence for one to arise today, within a million years or so of humans, out of the billions of years since the galaxy was born. If they were at all like humans as we are now, and colonized the galaxy, then some of them at least would probably have colonized Earth itself long before we evolved, and transformed it to their liking (maybe changed atmosphere and planted their own biology).
Or, there is no need for visiting ETs to take over the Earth - they'd have the technology to easily reproduce anything they want - and you can use the materials from comets and asteroids to make habitats in space. With the technology an ET would have after a few million years of development they could do that easily at almost no time cost to themselves, just set some automated robots working for a few years and you have your Stanford Torus or whatever in space to live in.
But if they were like us, and really were also keen to colonize the galaxy - they might just do that anyway - or - if they were into making habitats from asteroids and comets, then by now the entire solar system should be full of their free floating habitats in space. That we look up and don't see the sky filled with bright lights of ET spacecraft shows that no ET has set out to colonize the galaxy - or at least not successfully.
So is pretty clear that's not happened. If there are ETs then for whatever reason, they clearly aren't the galaxy colonizing or planet occupying type.
But humans, if we spread at our present stage of civilization, then some of use at least are like that.
So, I think we should instead worry about future humans and things they create - as potential Earth invaders rather than ETs. Just because they are our descendants a thousand generations removed, doesn't mean that they are going to be kindly disposed towards Earth and leave it alone, and be more gently disposed to us than ETs.
Plus, they could also trash the galaxy by accident. We almost have the technology to do that already - if you can make a self replicating self improving "Von neumann" machine, basically just a nanoscale 3D printer able to print out a computer chip and to make copies of itself - and it could spread just as life does, but using asteroids and comet materials to make copies of itself.
If you let it loose on the galaxy, it could turn entire galaxy into copies of itself, getting better and better at doing that as time goes on - and evolve, like life, maybe into things powerful and impossible to stop.
So - I don't know why people simultaneously want to colonize the galaxy - and then - worry about ETs invading Earth.
I've posted about this a few times in various places, mainly comments on my column at Science20, not had any truly reassuring answers to explain how we can colonize the galaxy in a safe way and be sure this won't happen.
Of course if you stick to just exploring, not settling down anywhere except a few firmly delineated safe places, with some way to be pretty certain that humans won't spread beyond them permanently - but can explore as much as they like - it's not a problem.
Also nomadic colonies traveling through the galaxy are fine, so long as there is something that limits them, prevents them from splitting up into more colonies as time goes on - or do so only very very slowly like very few billion years.
If you have any ideas of how colonizing the galaxy by humans can be done safely, without a significant risk of trashing it both for ourselves and any future evolving ETs, do say.
---------------------
Mukul Jain has just made an interesting comment suggesting
Project Orion (nuclear propulsion)
There's also this intriguing idea, which I found from that article:
Use of Mini-Mag Orion and superconducting coils for near-term interstellar transportation
It's actually about an idea to send a stream of mini solar sails - just a pellet in a Mylar sheath - as a way of refueling an interstellar spaceship in flight through its acceleration phase from Earth. You don't get spreading of the beam as you do for laser transferred power - so can do at high efficiency during the acceleration phase.
You could just use the momentum of the solar sails for acceleration, as in this earlier concept by Jordin Kare Sailbeam (slides) - Paper (to get an idea of how it works see the Figure 1: SailBeam Concept in the paper),
Jordin Kare thinks there's a chance you could manage 0.1c or faster with this method.
But the authors' idea in Use of Mini-Mag Orion and superconducting coils for near-term interstellar transportation is that it's more efficient to send fuel for the spaceship rather than just use it for momentum exchange.
For decelerating, the spacecraft generates a magnetic field which acts as a brake against the solar wind of the destination star. In this idea, it uses a superconducting coil to generate the magnetic field
It's a Magnetic sail
A similar idea to the MagSail is the Electric sail (or e-Sail) which is being investigated by the ESA as a way to propel spacecraft to the outer solar system, it uses many thin wires spreading out from the craft, and an electron gun in the centre fires electrons away (shown blue below) thus creating a current which flows in from the wires to the centre - this creates a magnetic field which makes an obstacle to the solar wind - rest is as for the MagSail, here is an artist's impression.
The paradoxical thing about interstellar travel is that so long as the timescale is of order of centuries, it's worth your while waiting for the technology to improve as otherwise later departures get there before you - until the time required goes down to a few decades. But if timescale was just 44 years, could be worth setting off right away.
Surely unmanned probes first?
An even faster way to get there is being explored at the University of Michigan, the Nanofet drive, which fires small particles at close t the speed of light designed for tiny spacecraft
Nano-particle field extraction thruster
Theoretically these could let nano spacecraft fly at almost light speed - and larger craft also
Firing Off Charged Nanoparticles Might Allow Spaceships to Move at Near-Light Speed
Though there would be many practical issues with a big spacecraft going close to light speed through the interstellar medium, .
Another more way out idea being researched, Quantum vacuum plasma thruster
- idea is - to separate out particles from quantum fluctuations on the vacuum and accelerate this as your reaction mass so you don't have to carry it with you..
and lots of other ideas.
Personally I'm not at all sure we should colonize the galaxy, though great to explore it. The problem is, that if, as the author of that paper suggests, humans fill the galaxy quickly, say in a million years or so, then - what would all those humans turn into?
We worry about aliens invading Earth. But it's pretty clear that no alien species have colonized our galaxy yet, and it would be just an extraordinary coincidence for one to arise today, within a million years or so of humans, out of the billions of years since the galaxy was born. If they were at all like humans as we are now, and colonized the galaxy, then some of them at least would probably have colonized Earth itself long before we evolved, and transformed it to their liking (maybe changed atmosphere and planted their own biology).
Or, there is no need for visiting ETs to take over the Earth - they'd have the technology to easily reproduce anything they want - and you can use the materials from comets and asteroids to make habitats in space. With the technology an ET would have after a few million years of development they could do that easily at almost no time cost to themselves, just set some automated robots working for a few years and you have your Stanford Torus or whatever in space to live in.
But if they were like us, and really were also keen to colonize the galaxy - they might just do that anyway - or - if they were into making habitats from asteroids and comets, then by now the entire solar system should be full of their free floating habitats in space. That we look up and don't see the sky filled with bright lights of ET spacecraft shows that no ET has set out to colonize the galaxy - or at least not successfully.
So is pretty clear that's not happened. If there are ETs then for whatever reason, they clearly aren't the galaxy colonizing or planet occupying type.
But humans, if we spread at our present stage of civilization, then some of use at least are like that.
So, I think we should instead worry about future humans and things they create - as potential Earth invaders rather than ETs. Just because they are our descendants a thousand generations removed, doesn't mean that they are going to be kindly disposed towards Earth and leave it alone, and be more gently disposed to us than ETs.
Plus, they could also trash the galaxy by accident. We almost have the technology to do that already - if you can make a self replicating self improving "Von neumann" machine, basically just a nanoscale 3D printer able to print out a computer chip and to make copies of itself - and it could spread just as life does, but using asteroids and comet materials to make copies of itself.
If you let it loose on the galaxy, it could turn entire galaxy into copies of itself, getting better and better at doing that as time goes on - and evolve, like life, maybe into things powerful and impossible to stop.
So - I don't know why people simultaneously want to colonize the galaxy - and then - worry about ETs invading Earth.
I've posted about this a few times in various places, mainly comments on my column at Science20, not had any truly reassuring answers to explain how we can colonize the galaxy in a safe way and be sure this won't happen.
Of course if you stick to just exploring, not settling down anywhere except a few firmly delineated safe places, with some way to be pretty certain that humans won't spread beyond them permanently - but can explore as much as they like - it's not a problem.
Also nomadic colonies traveling through the galaxy are fine, so long as there is something that limits them, prevents them from splitting up into more colonies as time goes on - or do so only very very slowly like very few billion years.
If you have any ideas of how colonizing the galaxy by humans can be done safely, without a significant risk of trashing it both for ourselves and any future evolving ETs, do say.
---------------------
Mukul Jain has just made an interesting comment suggesting
- "A type 4 civilization (or even a sufficiently advanced type 3 one) may be able to work with technology that makes their actions indistinguishable from natural phenomena" The Kardashev Scale – Type I, II, III, IV & V Civilization
- "With our current evolutionary status, we cannot even colonise parts of the planet without damaging the natural order of things. But please understand that a million years of evolution (or even a few hundred thousand), gives a civilisation enough time to evolve socially as well, so I would still give humanity (in whatever form it may be in the future) a good chance of being able to successfully colonise the galaxy."
http://www.quora.com/Could-we-get-a-space-probe-to-Alpha-Centauri-by-2121-if-it-got-top-priority/answer/Robert-Walker-5/comment/9035608?srid=ptwx&share=1
About the Author
Robert Walker
Writer of articles on Mars and Space issues - Software Developer of Tune Smithy, Bounce Metronome etc.Studied at Wolfson College, Oxford
Lives in Isle of Mull
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