6 ms·

Musk ever spoken about what he'd do to get outside of the solar? Speed of light is a bastard of a limitation to have to beat...

m4r35n357 6y ago
Even if it were _not_ a physical limit, we still wouldn't get anywhere near it with a real (even fantasy) rocket. One of the first things I tried in Frontier (ancient space game).
d_silin 6y ago
There is plenty of stuff to explore and colonize in Solar System alone. But interstellar travel is not that unfeasible. Sending an unmanned probe to Alpha or Proxima Centauri might be just possible in the next century.
- brutt 6y ago
  We can send probe right away by throwing few dozen billions on it, but it will arrive in the next century.
admax88q 6y ago
Only for those left behind, time dilation is magic. As per wikipedia: > a constant 1 g acceleration would permit humans to travel through the entire known Universe in one human lifetime So it's really only a challenge of propulsion. You're not making a return trip to any recognizable civilization though.
- jandrese 6y ago
  Yeah, but have you ever worked out the rocket equation for a spaceship that accelerates at 1G for a full year? There literally isn’t enough mass in our solar system, even with a ridiculous engine with an ISP of 5000 and perfect alchemy to convert all raw mass in the solar system to rocket fuel.
  - yread 6y ago
    Project Orion could do ISP of 100,000. Even nuclear thermal engine could reach 5000
    - jandrese 6y ago
      As far as I know Nuclear Thermal rockets have topped out around 1000. Project Orion is entirely theoretical and the ISP calculations should be taken with a grain of salt.
- d_silin 6y ago
  The amount of energy required to keep that 1g acceleration though...
  - brutt 6y ago
    Sun have lot of energy, so it can be used as energy source. If you plan to travel at % of c, you will need strong enough radiation and thermal shield anyway. And if you have such shield, why not just dive into Sun for refueling? Humans can stay at high orbit, when interstellar locomotive refuels.
    - kzrdude 6y ago
      At the speed you are going, the sun will quickly be a pale white dot
      - fabiospampinato 6y ago
        Potentially you could bring the sun along with you.
        misnome 6y ago
        Where does the energy to accelerate the sun at 1g come from?...
        fabiospampinato 6y ago
        From the sun itself, potentially it might be doable
        cgriswald 6y ago
        From the sun: https://en.m.wikipedia.org/wiki/Stellar_engine https://en.m.wikipedia.org/wiki/Stellar_engine
        misnome 6y ago
- olvy0 6y ago
  Explored in Paul Anderson's novel Tau Zero. https://en.wikipedia.org/wiki/Tau_Zero https://en.wikipedia.org/wiki/Tau_Zero
  - cure 6y ago
    Nitpick, it's Poul Anderson. Yes, that is an odd spelling of his first name.
    - ochrist 6y ago
      Not in Denmark where his family came from.
  - kwhitefoot 6y ago
    Brilliant book! I recommend it highly.
- dylan604 6y ago
  And you're also never stopping anywhere, so it would only ever be a permanent sight seeing tour.
- empath75 6y ago
  Stopping is sort of a problem.
- hellofunk 6y ago
  > a constant 1 g acceleration would permit humans to travel through the entire known Universe in one human lifetime Wow that is actually very fascinating, it never occurred to me that it works that way. I’m always thinking of 11 light years as too far away for someone to achieve in a lifetime, but I am of course thinking about that from the perspective of the person who is not traveling.
  - cmehdy 6y ago
    I'm not sure how they calculate the 1g thing past the speed of light (which takes you something short of a year to get to by classical mechanics). But say we just break physics as we know it, and somehow the prophesized amount of time to travel is accurate. You're still going in a straight line and not stopping, unless you want to take another lifetime or be crushed by forces that would hurt just a little bit. So don't turn, only decide to stop in the first half of your life (or you won't live to see the end of the journey), beat light and physics by the end of year one of your life, and enjoy the ride. I'm not sure what you'll "see" outside of your spaceship though, and I do hope for you that there's not a single speck of dust in your path and no wall at the end.
    - californical 6y ago
      I didn't read their idea, but you wouldn't ever need to go faster than the speed of light for this to work -- just approaching it infinitely close would be enough. Sure it might take a hundred million years for your journey from an observer watching you on earth, but thanks to time dilation, it could still be less than a lifetime for the person on the ship
      - cmehdy 6y ago
        Well then how do you get to the parts of our universe that are receding at a speed faster than light due to space expansion? I'm not nearly as comfortable with relativity as I'd like to be, but too much in this hypothetical "woahdude" scenario ends up being a logical roadblock to me.
- deleted 6y ago
  [deleted]
- mikro2nd 6y ago
  > only a challenge of propulsion Also a challenge of ablation. At any reasonable fraction of c your spacecraft has a serious erosion problem.
  - TheOtherHobbes 6y ago
    Possibly also the challenge of getting baked by the Unruh Effect.
- philipkglass 6y ago
  This substitutes the challenge of inventing a warp drive with the challenge of inventing a limitless free energy machine. An antimatter fueled rocket can't keep up with what "1G, indefinitely" demands. Not even beamed power propulsion driven by a Dyson swarm can do that. I like the Revelation Space universe, but its fictional Conjoiner drive and the near-light-speed Lighthugger spacecraft powered by it are no closer to realization than any of Star Trek's technobabble. The same goes for the forever-accelerating Bussard ramjet vessel of Tau Zero.
- bryanrasmussen 6y ago
  what is one human lifetime? that seems an uncertain measure. Also most astronauts I've seen look like they're halfway through one human lifetime when they first get off planet.
gpm 6y ago
As far as we know Musk isn't keen on the idea of interstellar travel. SpaceX's COO Gwynne Shotwell is, and has spoken publicly about it (and has allude to Musk's opinions on it [1]). That said the basic requirement is a significant propulsion breakthrough [2], current technology just isn't good enough. You don't beat the speed of light, you just travel at an appreciable fraction of it an accept the fact that by the time you arrive everyone on earth will have aged n (>11?) years. [1] https://www.ted.com/talks/gwynne_shotwell_spacex_s_plan_to_fly_you_across_the_globe_in_30_minutes/transcript#t-1278869 https://www.ted.com/talks/gwynne_shotwell_spacex_s_plan_to_f... [2] https://twitter.com/thesheetztweetz/status/1187745445361180672?ref_src=twsrc%5Etfw%7Ctwcamp%5Etweetembed%7Ctwterm%5E1187745445361180672%7Ctwgr%5E&ref_url=https%3A%2F%2Fforum.nasaspaceflight.com%2Findex.php%3Ftopic%3D49353.0 https://twitter.com/thesheetztweetz/status/11877454453611806...
- kitsunesoba 6y ago
  I think the first strides in interstellar travel will probably occur once long-term habitation and manufacturing in space have been mastered, because then it's feasible to construct ships that are either too large to drag out of a planetary gravity well and/or too dangerous to build in the gravity well of an inhabited body (nuclear propulsion).
- nickpeterson 6y ago
  Another thing is that human lifespan might well improve in the meantime. Pair that with deep sleep/suspended animation and you have a pretty potent combo for conquering long distances.
  - einpoklum 6y ago
    In the near future, human lifespan might improve, but mostly in the form of surviving in poor health at old age.

m4r35n357 6y ago

Even if it were _not_ a physical limit, we still wouldn't get anywhere near it with a real (even fantasy) rocket. One of the first things I tried in Frontier (ancient space game).

d_silin 6y ago

There is plenty of stuff to explore and colonize in Solar System alone. But interstellar travel is not that unfeasible. Sending an unmanned probe to Alpha or Proxima Centauri might be just possible in the next century.

brutt 6y ago
We can send probe right away by throwing few dozen billions on it, but it will arrive in the next century.

admax88q 6y ago

Only for those left behind, time dilation is magic. As per wikipedia: > a constant 1 g acceleration would permit humans to travel through the entire known Universe in one human lifetime So it's really only a challenge of propulsion. You're not making a return trip to any recognizable civilization though.

jandrese 6y ago
Yeah, but have you ever worked out the rocket equation for a spaceship that accelerates at 1G for a full year? There literally isn’t enough mass in our solar system, even with a ridiculous engine with an ISP of 5000 and perfect alchemy to convert all raw mass in the solar system to rocket fuel.
- yread 6y ago
  Project Orion could do ISP of 100,000. Even nuclear thermal engine could reach 5000
  - jandrese 6y ago
    As far as I know Nuclear Thermal rockets have topped out around 1000. Project Orion is entirely theoretical and the ISP calculations should be taken with a grain of salt.
d_silin 6y ago
The amount of energy required to keep that 1g acceleration though...
- brutt 6y ago
  Sun have lot of energy, so it can be used as energy source. If you plan to travel at % of c, you will need strong enough radiation and thermal shield anyway. And if you have such shield, why not just dive into Sun for refueling? Humans can stay at high orbit, when interstellar locomotive refuels.
  - kzrdude 6y ago
    At the speed you are going, the sun will quickly be a pale white dot
    - fabiospampinato 6y ago
      Potentially you could bring the sun along with you.
      - misnome 6y ago
        Where does the energy to accelerate the sun at 1g come from?...
        fabiospampinato 6y ago
        From the sun itself, potentially it might be doable
        cgriswald 6y ago
        From the sun: https://en.m.wikipedia.org/wiki/Stellar_engine https://en.m.wikipedia.org/wiki/Stellar_engine
        misnome 6y ago
olvy0 6y ago
Explored in Paul Anderson's novel Tau Zero. https://en.wikipedia.org/wiki/Tau_Zero https://en.wikipedia.org/wiki/Tau_Zero
- cure 6y ago
  Nitpick, it's Poul Anderson. Yes, that is an odd spelling of his first name.
  - ochrist 6y ago
    Not in Denmark where his family came from.
- kwhitefoot 6y ago
  Brilliant book! I recommend it highly.
dylan604 6y ago
And you're also never stopping anywhere, so it would only ever be a permanent sight seeing tour.
empath75 6y ago
Stopping is sort of a problem.
hellofunk 6y ago
> a constant 1 g acceleration would permit humans to travel through the entire known Universe in one human lifetime Wow that is actually very fascinating, it never occurred to me that it works that way. I’m always thinking of 11 light years as too far away for someone to achieve in a lifetime, but I am of course thinking about that from the perspective of the person who is not traveling.
- cmehdy 6y ago
  I'm not sure how they calculate the 1g thing past the speed of light (which takes you something short of a year to get to by classical mechanics). But say we just break physics as we know it, and somehow the prophesized amount of time to travel is accurate. You're still going in a straight line and not stopping, unless you want to take another lifetime or be crushed by forces that would hurt just a little bit. So don't turn, only decide to stop in the first half of your life (or you won't live to see the end of the journey), beat light and physics by the end of year one of your life, and enjoy the ride. I'm not sure what you'll "see" outside of your spaceship though, and I do hope for you that there's not a single speck of dust in your path and no wall at the end.
  - californical 6y ago
    I didn't read their idea, but you wouldn't ever need to go faster than the speed of light for this to work -- just approaching it infinitely close would be enough. Sure it might take a hundred million years for your journey from an observer watching you on earth, but thanks to time dilation, it could still be less than a lifetime for the person on the ship
    - cmehdy 6y ago
      Well then how do you get to the parts of our universe that are receding at a speed faster than light due to space expansion? I'm not nearly as comfortable with relativity as I'd like to be, but too much in this hypothetical "woahdude" scenario ends up being a logical roadblock to me.
deleted 6y ago
[deleted]
mikro2nd 6y ago
> only a challenge of propulsion Also a challenge of ablation. At any reasonable fraction of c your spacecraft has a serious erosion problem.
- TheOtherHobbes 6y ago
  Possibly also the challenge of getting baked by the Unruh Effect.
philipkglass 6y ago
This substitutes the challenge of inventing a warp drive with the challenge of inventing a limitless free energy machine. An antimatter fueled rocket can't keep up with what "1G, indefinitely" demands. Not even beamed power propulsion driven by a Dyson swarm can do that. I like the Revelation Space universe, but its fictional Conjoiner drive and the near-light-speed Lighthugger spacecraft powered by it are no closer to realization than any of Star Trek's technobabble. The same goes for the forever-accelerating Bussard ramjet vessel of Tau Zero.
bryanrasmussen 6y ago
what is one human lifetime? that seems an uncertain measure. Also most astronauts I've seen look like they're halfway through one human lifetime when they first get off planet.

gpm 6y ago

As far as we know Musk isn't keen on the idea of interstellar travel. SpaceX's COO Gwynne Shotwell is, and has spoken publicly about it (and has allude to Musk's opinions on it [1]). That said the basic requirement is a significant propulsion breakthrough [2], current technology just isn't good enough. You don't beat the speed of light, you just travel at an appreciable fraction of it an accept the fact that by the time you arrive everyone on earth will have aged n (>11?) years. [1] https://www.ted.com/talks/gwynne_shotwell_spacex_s_plan_to_fly_you_across_the_globe_in_30_minutes/transcript#t-1278869 https://www.ted.com/talks/gwynne_shotwell_spacex_s_plan_to_f... [2] https://twitter.com/thesheetztweetz/status/1187745445361180672?ref_src=twsrc%5Etfw%7Ctwcamp%5Etweetembed%7Ctwterm%5E1187745445361180672%7Ctwgr%5E&ref_url=https%3A%2F%2Fforum.nasaspaceflight.com%2Findex.php%3Ftopic%3D49353.0 https://twitter.com/thesheetztweetz/status/11877454453611806...

kitsunesoba 6y ago
I think the first strides in interstellar travel will probably occur once long-term habitation and manufacturing in space have been mastered, because then it's feasible to construct ships that are either too large to drag out of a planetary gravity well and/or too dangerous to build in the gravity well of an inhabited body (nuclear propulsion).
nickpeterson 6y ago
Another thing is that human lifespan might well improve in the meantime. Pair that with deep sleep/suspended animation and you have a pretty potent combo for conquering long distances.
- einpoklum 6y ago
  In the near future, human lifespan might improve, but mostly in the form of surviving in poor health at old age.