5 ms·

Tau Ceti's planets nearest around single, Sun-like star

43 points by morphics 14y ago

Tichy 14y ago
Just looked on Wikipedia, it is 12 light years away. So how long to get there with conventional technology? I suspect speed isn't even the worst problem, harder to deal will radiation? Also I suppose any such mission would have to be fully automated, remote debugging would be too frustrating with a 24 year round trip for information. Have there been any spacecraft besides Voyager even launched beyond the boundaries of our solar system?
- simfoo 14y ago
  > Have there been any spacecraft besides Voyager even launched beyond the boundaries of our solar system? No. > So how long to get there with conventional technology? I don't have any precise numbers but I guess it would be in the neighborhood of 100000 years one-way with today's technology (if even possible)
  - Tichy 14y ago
    I just looked it up on Wolfram Alpha, apparently the speed of Voyager is 17km/s, or ~1/18000th the speed of light? So it would take Voyager 216000 years to make the journey? Bummer :-( We probably couldn't even build a probe that would last long enough?
    - simfoo 14y ago
      50 km/s is a speed I think we could reach (by clever gravitational maneuvers for example). Even then the trip would take 72000 years. Better wait another few hundred years until we hopefully can launch a probe at a significant fraction of the speed of light.
      - uvdiv 14y ago
        Ion engines have been tested at effective exhaust velocities of 90 km/s [0], which allows delta-v's up to 500 km/s or so. [0] https://en.wikipedia.org/wiki/High_Power_Electric_Propulsion https://en.wikipedia.org/wiki/High_Power_Electric_Propulsion
- etfb 14y ago
  We'll need either three or four quantum leaps in technology, or a sudden discovery that invalidates much of what we know about physics and/or cosmology, before even the Alpha Centauri planets become reachable. "Like it or not, for the moment, the Earth is where we make our stand."
  - EliRivers 14y ago
    A quantum leap is (on the order of, if you skip a level) the smallest possible increment. We're going to need much bigger leaps than that to do it in four or five leaps. :)
    - epsylon 14y ago
      Relevant SMBC: http://www.smbc-comics.com/index.php?db=comics&id=2628 http://www.smbc-comics.com/index.php?db=comics&id=2628
    - unwind 14y ago
      Some writers of dictionaries disagree: http://www.merriam-webster.com/dictionary/quantum%20leap http://www.merriam-webster.com/dictionary/quantum%20leap. You're using the technical (or jargon) meaning, which is not the same as the mainstream ("popular") meaning.
      - MalphasWats 14y ago
        I think that's generally how jokes work.
    - deleted 14y ago
      [deleted]
    - etfb 14y ago
      I was using the term in neither the mainstream nor the technical sense, but in the Dr Sam Beckett sense. Oh, boy!
- randallsquared 14y ago
  Using 1960s engineering (and many, many nuclear bombs), an Orion-powered starship could make it there in less than 150 years, one-way. And no slowing down; it would be a flyby. http://en.wikipedia.org/wiki/Project_Orion_(nuclear_propulsion)#Interstellar_missions http://en.wikipedia.org/wiki/Project_Orion_(nuclear_propulsi...
  - rdl 14y ago
    Can't you just turn around midway and start throwing bombs out in front of your path of travel to slow down?
    - jasonkester 14y ago
      One of the interesting things in that Wikipedia link is that you only need to run your Orion for 36 days to get it up to speed. Beyond that, detonating more bombs won't accelerate you any further. So yes, you could turn it around. But surprisingly it seems you can wait until a month before arrival to do so. The downside, however, is that your max velocity gets cut in half if you bring enough bombs to slow down. With better explosives, you could get a higher max velocity and therefore closer to the "accelerate halfway, decelerate halfway" ideal case, but at the moment such explosives don't exist.
      - rdl 14y ago
        I'm not sure how that works out. Do 36 days of acceleration at the beginning (or spread it over a year to reduce peak acceleration) -- go from 0 to 0.1c or whatever the cruise speed is. Coast for ~100 years. Spend the last year going from 0.1c to 0. It does mean you have to carry twice as many bombs, and carry half of the bombs for 149 years, but bombs are really lightweight relative to the ship. It also means you can't just jettison the pusher plate, which is probably a bigger deal.
        randallsquared 14y ago
        In this case, the weight of the bombs is larger than the rest of the ship: 50K tons for the ship structure, 300K for the weight of the bombs [1]. Twice as many bombs essentially doubles launch mass. Orion is a great concept for tooling around the solar system easily, but what it buys us over interstellar distances is that it makes macroscopic payloads and reasonable travel times possible; they're still not easy. [1] Table 2 in http://galileo.phys.virginia.edu/classes/109.jvn.spring00/nuc_rocket/Dyson.pdf http://galileo.phys.virginia.edu/classes/109.jvn.spring00/nu...
- eloisius 14y ago
  A pretty interesting read that addresses these questions is Deep Space Propulsion: A Roadmap to Interstellar Flight http://www.amazon.com/Deep-Space-Propulsion-Interstellar-Astronomers/dp/1461406064 http://www.amazon.com/Deep-Space-Propulsion-Interstellar-Ast...
- TorKlingberg 14y ago
  Radiation can be handled, just put shielding around the astronauts. That adds weight of course, which makes the spacecraft harder to accelerate. Btw, even Voyager 1 is only 0.002 light years from earth.
ndonnellan 14y ago
I remember playing Outpost as a kid. Tau Ceti was definitely the best bet. I loved/hated the fact that you could send your colonists to a solar system that wasn't habitable and then the game would just be over in 5mins; your creepy AI giving you the bad news. - http://en.wikipedia.org/wiki/Outpost_(video_game) http://en.wikipedia.org/wiki/Outpost_(video_game)
martinkallstrom 14y ago
Perhaps Tau Ceti is even close enough to not be trapped to the paradox of interstellar travel: "No matter when you launch a voyage somewhere, some one else will build a better spaceship and get there before you." Is there a sci-fi novel about this? (an interstellar space voyage for a remote planet discovers humans launching after them already have colonized it when they get there)
- wazoox 14y ago
  "The forever war" uses the time dilation of relativistic travel, which is a related concept.

43 points by morphics 14y ago

Tichy 14y ago

Just looked on Wikipedia, it is 12 light years away. So how long to get there with conventional technology? I suspect speed isn't even the worst problem, harder to deal will radiation? Also I suppose any such mission would have to be fully automated, remote debugging would be too frustrating with a 24 year round trip for information. Have there been any spacecraft besides Voyager even launched beyond the boundaries of our solar system?

simfoo 14y ago
> Have there been any spacecraft besides Voyager even launched beyond the boundaries of our solar system? No. > So how long to get there with conventional technology? I don't have any precise numbers but I guess it would be in the neighborhood of 100000 years one-way with today's technology (if even possible)
- Tichy 14y ago
  I just looked it up on Wolfram Alpha, apparently the speed of Voyager is 17km/s, or ~1/18000th the speed of light? So it would take Voyager 216000 years to make the journey? Bummer :-( We probably couldn't even build a probe that would last long enough?
  - simfoo 14y ago
    50 km/s is a speed I think we could reach (by clever gravitational maneuvers for example). Even then the trip would take 72000 years. Better wait another few hundred years until we hopefully can launch a probe at a significant fraction of the speed of light.
    - uvdiv 14y ago
      Ion engines have been tested at effective exhaust velocities of 90 km/s [0], which allows delta-v's up to 500 km/s or so. [0] https://en.wikipedia.org/wiki/High_Power_Electric_Propulsion https://en.wikipedia.org/wiki/High_Power_Electric_Propulsion
etfb 14y ago
We'll need either three or four quantum leaps in technology, or a sudden discovery that invalidates much of what we know about physics and/or cosmology, before even the Alpha Centauri planets become reachable. "Like it or not, for the moment, the Earth is where we make our stand."
- EliRivers 14y ago
  A quantum leap is (on the order of, if you skip a level) the smallest possible increment. We're going to need much bigger leaps than that to do it in four or five leaps. :)
  - epsylon 14y ago
    Relevant SMBC: http://www.smbc-comics.com/index.php?db=comics&id=2628 http://www.smbc-comics.com/index.php?db=comics&id=2628
  - unwind 14y ago
    Some writers of dictionaries disagree: http://www.merriam-webster.com/dictionary/quantum%20leap http://www.merriam-webster.com/dictionary/quantum%20leap. You're using the technical (or jargon) meaning, which is not the same as the mainstream ("popular") meaning.
    - MalphasWats 14y ago
      I think that's generally how jokes work.
  - deleted 14y ago
    [deleted]
  - etfb 14y ago
    I was using the term in neither the mainstream nor the technical sense, but in the Dr Sam Beckett sense. Oh, boy!
randallsquared 14y ago
Using 1960s engineering (and many, many nuclear bombs), an Orion-powered starship could make it there in less than 150 years, one-way. And no slowing down; it would be a flyby. http://en.wikipedia.org/wiki/Project_Orion_(nuclear_propulsion)#Interstellar_missions http://en.wikipedia.org/wiki/Project_Orion_(nuclear_propulsi...
- rdl 14y ago
  Can't you just turn around midway and start throwing bombs out in front of your path of travel to slow down?
  - jasonkester 14y ago
    One of the interesting things in that Wikipedia link is that you only need to run your Orion for 36 days to get it up to speed. Beyond that, detonating more bombs won't accelerate you any further. So yes, you could turn it around. But surprisingly it seems you can wait until a month before arrival to do so. The downside, however, is that your max velocity gets cut in half if you bring enough bombs to slow down. With better explosives, you could get a higher max velocity and therefore closer to the "accelerate halfway, decelerate halfway" ideal case, but at the moment such explosives don't exist.
    - rdl 14y ago
      I'm not sure how that works out. Do 36 days of acceleration at the beginning (or spread it over a year to reduce peak acceleration) -- go from 0 to 0.1c or whatever the cruise speed is. Coast for ~100 years. Spend the last year going from 0.1c to 0. It does mean you have to carry twice as many bombs, and carry half of the bombs for 149 years, but bombs are really lightweight relative to the ship. It also means you can't just jettison the pusher plate, which is probably a bigger deal.
      - randallsquared 14y ago
        In this case, the weight of the bombs is larger than the rest of the ship: 50K tons for the ship structure, 300K for the weight of the bombs [1]. Twice as many bombs essentially doubles launch mass. Orion is a great concept for tooling around the solar system easily, but what it buys us over interstellar distances is that it makes macroscopic payloads and reasonable travel times possible; they're still not easy. [1] Table 2 in http://galileo.phys.virginia.edu/classes/109.jvn.spring00/nuc_rocket/Dyson.pdf http://galileo.phys.virginia.edu/classes/109.jvn.spring00/nu...
eloisius 14y ago
A pretty interesting read that addresses these questions is Deep Space Propulsion: A Roadmap to Interstellar Flight http://www.amazon.com/Deep-Space-Propulsion-Interstellar-Astronomers/dp/1461406064 http://www.amazon.com/Deep-Space-Propulsion-Interstellar-Ast...
TorKlingberg 14y ago
Radiation can be handled, just put shielding around the astronauts. That adds weight of course, which makes the spacecraft harder to accelerate. Btw, even Voyager 1 is only 0.002 light years from earth.

ndonnellan 14y ago

I remember playing Outpost as a kid. Tau Ceti was definitely the best bet. I loved/hated the fact that you could send your colonists to a solar system that wasn't habitable and then the game would just be over in 5mins; your creepy AI giving you the bad news. - http://en.wikipedia.org/wiki/Outpost_(video_game) http://en.wikipedia.org/wiki/Outpost_(video_game)

martinkallstrom 14y ago

Perhaps Tau Ceti is even close enough to not be trapped to the paradox of interstellar travel: "No matter when you launch a voyage somewhere, some one else will build a better spaceship and get there before you." Is there a sci-fi novel about this? (an interstellar space voyage for a remote planet discovers humans launching after them already have colonized it when they get there)

wazoox 14y ago
"The forever war" uses the time dilation of relativistic travel, which is a related concept.