4 ms·

It's a Trap ;) On a serious note, if we can travel close to the speed of light , say 95%, using for example, nuclear rockets, how long would it take to arrive

by ionwake 10y ago

It's a Trap ;) On a serious note, if we can travel close to the speed of light , say 95%, using for example, nuclear rockets, how long would it take to arrive ? ( from the travellers perspective )

jxcole 10y ago
It's 39 light years so no fewer than 39 years from our perspective. The closer to the speed of light the travelers are the less time will appear to have elapsed from their perspective. If you had rockets that could instantaneously accelerate to infinitessimally close to the speed of light, no time at all would appear to have elapsed from the travelers perspective (or no time that they would notice), but this is very unlikely.
trcollinson 10y ago
Well it is approximately 40 light years away from our solar system. So the basic calculation would say about 42 years but this doesn't account for acceleration and deceleration and such.
vkou 10y ago
At a constant 1g of acceleration, you could travel there, from the traveler's point of view, in ~2-3 years. (And in ~40 years from a stationary observer's point of view.) Mind you, a constant 1g acceleration (Or accelerating any human-carrying spaceship to relativistic speeds, really,) is about as plausible as a spaceship driven by pixie dust and unicorn farts.
- ionwake 10y ago
  Not according to public research on theoretical designs that have been about for decades . Unless you consider them unicorn farts! I'm only a coder though so I have no knowledge of this domain tho. I think the problem is simply it's too expensive to build space ships that probably won't work at all :( wasnt NASAs budget slashed ?
  - twoodfin 10y ago
    It's not money, it's the basic rocket equation: Newtonian acceleration requires fuel and the mass of fuel makes acceleration more costly. Relativity makes things even worse.
    - ionwake 10y ago
      See comment above yours, does your point still apply?
      - dragonwriter 10y ago
        Absolutely.
        ionwake 10y ago
        oh ok , you win , thanks for your replies ^_^
  - gus_massa 10y ago
    > Not according to public research on theoretical designs that have been about for decades. Which ones? Do you have a link? The only one I remember is https://en.wikipedia.org/wiki/Project_Orion_(nuclear_propulsion) https://en.wikipedia.org/wiki/Project_Orion_(nuclear_propuls... but it's more a general idea that a detailed blueprint that only need some money to get built.
    - ionwake 10y ago
      Thats the one I read. It sounds awesome. Srsly give me 5% of the GDP of the US and I'll put a monkey on Trappist within 5 years. Monkey time. *Im not being serious, I have no idea how much it would cost or if it would even work.
      - dragonwriter 10y ago
        Project Orion doesn't get you anywhere close to 1G constant acceleration to turnover and constant deceleration the rest of the way; a fairly high performance Orion concept for interstellar use did have 1G acceleration, but only for 10 days on each end of a 133 year trip to Alpha Centauri -- and needed 300,000 nuclear bombs with 1 megaton yield each as fuel. > Srsly give me 5% of the GDP of the US and I'll put a monkey on Trappist within 5 years. No, you won't. First, you won't design and build and launch a ship that will ever get to TRAPPIST-1 within 5 years at that (or any) price, and second TRAPPIST-1 is close to 40 light-years away, so even if you had a ship built and ready to launch today, you aren't getting anything there within 5 years.
- shireboy 10y ago
  You would just blow by it though. If you wanted to stop there, your ship would have to turn around and aim the unicorn farts forward to decelerate you 1g the second half of the trip, bringing the time to ~7-8y
- logfromblammo 10y ago
  If pixie dust is plutonium and unicorn farts are tetradeuterium-methane, you could get there in 400 years or so, Earth-time, 398 years shipboard time. So you really need your pixie dust to be antimatter, and your unicorn farts to be terawatt lasers. For now, the wait calculation suggests that anyone leaving now will reach their destination after someone who waits to leave until after the next breakthrough in space propulsion technology.
  - stagbeetle 10y ago
    I see "antimatter" and "black hole" being thrown around as a source of propulsion in this thread. Is this based on anything real like using the energy created from the radiation or just sci-fi speculation?
    - logfromblammo 10y ago
      Positrons cost $25M/mg and antihydrogen costs $62.5B/mg. An interstellar trip to Alpha Centauri using antihydrogen-hydrogen annihilation reactions would cost more than 50 years of the entire economic output of the planet (as of 2016) just for the fuel. Since we need a large portion of that economic output for basic survival needs, there will be no antimatter rockets built any time soon. As far as I am aware, we currently lack the capability to create a singularity massive enough to persist long enough to observe as a black hole. But it is possible that we might be able to locate a primordial black hole near enough to build a propulsion system around it, or even trap one as it passes through Earth. This would, of course, require that primordial black holes exist, and that they emit Hawking radiation. Yes, for now it is purely speculation. Anything beyond chemical-energy rockets is speculation until we actually demo the technology in a real spacecraft. If you launched today, bound for Alpha Centauri, the best you could do is drop fusion bombs behind your vessel until you get to about 0.08c, turn around at some point and throw fusion bombs in your path to decelerate, and be prepared to arrive a long, long time from now.
wallace_f 10y ago
The answer for an outside observer is: @ 1g of acceleration it would take 11 months to accelerate to the speed of light. A formula you can put in Google is: (285000000/9.8)/(60x60x24). So 39-(.475x2) = 38, and 38/.95 = 40. So 42 years is your answer. I have no idea how to calculate the relativistic spaceship's elapsed time. It's all wishful thinking. The fastest thing man has created, the Juno spacecraft, travels, by some quick calculations, @ 0.00147% of the speed of light.
- OscarCunningham 10y ago
  This isn't how it works. As you approach the speed of light acceleration becomes less effective (i.e. you feel 1g but don't get faster at 10m/s^2). The interesting thing is that it's actually easier to calculate in the spaceship's reference frame. The two relativistic distortions cancel out and the Newtonian calculation gives the correct answer. So if you accelerate for the first half of your journey it takes you sqrt((28500000040/2)/(365246060*9.81/2)) = 6 years, and the same amount of time to decelerate, meaning 12 years in total.
  - wallace_f 10y ago
    >you feel 1g but don't get faster at 10m/s^2). how does this work? it's consistent with what I've read about c requiring infinite energy, and I'm sure it has something to do with relativity, but I don't have an intuitive sense of it

by ionwake 10y ago

It's a Trap ;) On a serious note, if we can travel close to the speed of light , say 95%, using for example, nuclear rockets, how long would it take to arrive ? ( from the travellers perspective )

jxcole 10y ago

It's 39 light years so no fewer than 39 years from our perspective. The closer to the speed of light the travelers are the less time will appear to have elapsed from their perspective. If you had rockets that could instantaneously accelerate to infinitessimally close to the speed of light, no time at all would appear to have elapsed from the travelers perspective (or no time that they would notice), but this is very unlikely.

trcollinson 10y ago

Well it is approximately 40 light years away from our solar system. So the basic calculation would say about 42 years but this doesn't account for acceleration and deceleration and such.

vkou 10y ago

At a constant 1g of acceleration, you could travel there, from the traveler's point of view, in ~2-3 years. (And in ~40 years from a stationary observer's point of view.) Mind you, a constant 1g acceleration (Or accelerating any human-carrying spaceship to relativistic speeds, really,) is about as plausible as a spaceship driven by pixie dust and unicorn farts.

ionwake 10y ago
Not according to public research on theoretical designs that have been about for decades . Unless you consider them unicorn farts! I'm only a coder though so I have no knowledge of this domain tho. I think the problem is simply it's too expensive to build space ships that probably won't work at all :( wasnt NASAs budget slashed ?
- twoodfin 10y ago
  It's not money, it's the basic rocket equation: Newtonian acceleration requires fuel and the mass of fuel makes acceleration more costly. Relativity makes things even worse.
  - ionwake 10y ago
    See comment above yours, does your point still apply?
    - dragonwriter 10y ago
      Absolutely.
      - ionwake 10y ago
        oh ok , you win , thanks for your replies ^_^
- gus_massa 10y ago
  > Not according to public research on theoretical designs that have been about for decades. Which ones? Do you have a link? The only one I remember is https://en.wikipedia.org/wiki/Project_Orion_(nuclear_propulsion) https://en.wikipedia.org/wiki/Project_Orion_(nuclear_propuls... but it's more a general idea that a detailed blueprint that only need some money to get built.
  - ionwake 10y ago
    Thats the one I read. It sounds awesome. Srsly give me 5% of the GDP of the US and I'll put a monkey on Trappist within 5 years. Monkey time. *Im not being serious, I have no idea how much it would cost or if it would even work.
    - dragonwriter 10y ago
      Project Orion doesn't get you anywhere close to 1G constant acceleration to turnover and constant deceleration the rest of the way; a fairly high performance Orion concept for interstellar use did have 1G acceleration, but only for 10 days on each end of a 133 year trip to Alpha Centauri -- and needed 300,000 nuclear bombs with 1 megaton yield each as fuel. > Srsly give me 5% of the GDP of the US and I'll put a monkey on Trappist within 5 years. No, you won't. First, you won't design and build and launch a ship that will ever get to TRAPPIST-1 within 5 years at that (or any) price, and second TRAPPIST-1 is close to 40 light-years away, so even if you had a ship built and ready to launch today, you aren't getting anything there within 5 years.
shireboy 10y ago
You would just blow by it though. If you wanted to stop there, your ship would have to turn around and aim the unicorn farts forward to decelerate you 1g the second half of the trip, bringing the time to ~7-8y
logfromblammo 10y ago
If pixie dust is plutonium and unicorn farts are tetradeuterium-methane, you could get there in 400 years or so, Earth-time, 398 years shipboard time. So you really need your pixie dust to be antimatter, and your unicorn farts to be terawatt lasers. For now, the wait calculation suggests that anyone leaving now will reach their destination after someone who waits to leave until after the next breakthrough in space propulsion technology.
- stagbeetle 10y ago
  I see "antimatter" and "black hole" being thrown around as a source of propulsion in this thread. Is this based on anything real like using the energy created from the radiation or just sci-fi speculation?
  - logfromblammo 10y ago
    Positrons cost $25M/mg and antihydrogen costs $62.5B/mg. An interstellar trip to Alpha Centauri using antihydrogen-hydrogen annihilation reactions would cost more than 50 years of the entire economic output of the planet (as of 2016) just for the fuel. Since we need a large portion of that economic output for basic survival needs, there will be no antimatter rockets built any time soon. As far as I am aware, we currently lack the capability to create a singularity massive enough to persist long enough to observe as a black hole. But it is possible that we might be able to locate a primordial black hole near enough to build a propulsion system around it, or even trap one as it passes through Earth. This would, of course, require that primordial black holes exist, and that they emit Hawking radiation. Yes, for now it is purely speculation. Anything beyond chemical-energy rockets is speculation until we actually demo the technology in a real spacecraft. If you launched today, bound for Alpha Centauri, the best you could do is drop fusion bombs behind your vessel until you get to about 0.08c, turn around at some point and throw fusion bombs in your path to decelerate, and be prepared to arrive a long, long time from now.

wallace_f 10y ago

The answer for an outside observer is: @ 1g of acceleration it would take 11 months to accelerate to the speed of light. A formula you can put in Google is: (285000000/9.8)/(60x60x24). So 39-(.475x2) = 38, and 38/.95 = 40. So 42 years is your answer. I have no idea how to calculate the relativistic spaceship's elapsed time. It's all wishful thinking. The fastest thing man has created, the Juno spacecraft, travels, by some quick calculations, @ 0.00147% of the speed of light.

OscarCunningham 10y ago
This isn't how it works. As you approach the speed of light acceleration becomes less effective (i.e. you feel 1g but don't get faster at 10m/s^2). The interesting thing is that it's actually easier to calculate in the spaceship's reference frame. The two relativistic distortions cancel out and the Newtonian calculation gives the correct answer. So if you accelerate for the first half of your journey it takes you sqrt((28500000040/2)/(365246060*9.81/2)) = 6 years, and the same amount of time to decelerate, meaning 12 years in total.
- wallace_f 10y ago
  >you feel 1g but don't get faster at 10m/s^2). how does this work? it's consistent with what I've read about c requiring infinite energy, and I'm sure it has something to do with relativity, but I don't have an intuitive sense of it