4 ms·

What does “viable” mean, though? For us, it might not be viable, but for organisms that live on a different (or even variable) time scale it might be just fine

What does “viable” mean, though? For us, it might not be viable, but for organisms that live on a different (or even variable) time scale it might be just fine.

valuearb 9y ago
I loved Rendezvous with Rama, and one of it's central lessons is anything is possible when you talk about alien civilizations. We can't assume to know their motivations and technologies. But looking at the basic physics/engineering involved, if it's an alien vehicle it raises some interesting questions and skepticism. Imagine we wanted to build a similar vehicle. If we wanted to send people to nearby stars, we'd likely need vehicles as big, or likely larger, than Oumuamua. If we were in a hurry to do it with present day technologies we'd have to build hundreds of SLS boosters to launch payloads so that astronauts could assemble a vehicle weighing tens of thousands of tons in orbit. And then we'd fuel it with tens of thousand of tons of fuel. So we could build it. What would we use for propulsion? Not chemical rockets, 40KM/sec is only achievable for tiny payloads to fuel ratios with chemical rockets. Maybe we could do it with Nuclear rockets, which were tested and proven to be twice as efficient in the 1960s, ala NERVA. Even then we'd only be able to use a bit more than half the fuel to accelerate towards our destination, if we wanted to stop there. So 40 km/sec would be extremely difficult to reach given how heavy it would be. And at 40 km/sec it would take 8,000 years, nearly a hundred generations before reaching the nearest star. Assuming the life support systems could last that long, they didn't run out of food, water, air, etc. That the engines weren't degraded by radiation over 8,000 years so they would still work when reaching the target. It's extremely unlikely we could count on any of this being true. But if we were ever to launch such a vehicle it would likely be outclassed very quickly. We already know how to build better propulsion systems. Existing ion drives are far more efficient, and theoretically offer over 100KM/sec speeds, we just haven't been able to scale them up yet. If we can scale up ion drives or similar technologies, we already have designs for Project Orion are entirely feasible, and offer massive speed increases. Freeman Dyson's interstellar designs offer 1,000-10,000 KM/sec speeds. If it took us a hundred years to build one, it would likely pass a hundred year old NERVA ship within a year or two. My point is we'd never launch such a slow vehicle as Oumuamua, because it would be relatively easy to build a significantly faster one. Even with todays technologies. So it's reasonable to think that an Alien civilization that could build a ship the size and speed of Oumuamua, could build much larger, faster ships for interstellar travel. If Oumuamua is a ship, the question would be why didn't they? One possible answer if Oumuamua is artificial, that it's not an interstellar vehicle. It's an interplanetary vehicle that had a complete failure of it's systems, and had just enough velocity to leave it's star system, and has been drifting for tens of thousands of years. But in that were the case, how did it came so close to our Sun? It's reasonable to assume that many billions or trillions of asteroids and comets have been ejected by star systems, so that occasionally a few come close enough to ours to make the tight orbit around the Sun that Oumuamua did. But it's hard to imagine there are billions or trillions of space wrecks wandering the milky way such that one randomly passes this close to our sun.
- ethbro 9y ago
  > If Oumuamua is a ship, the question would be why didn't they [build a larger and faster ship]? Because they didn't know we were here? Supposing you're exploring the galaxy, hyper advanced technology doesn't free you from efficient resource use as a priority until you can easily build enough to explore every star. Given how many stars there are, I wouldn't be surprised if high tech civilizations still used the cheapest ships they could build. I'd be curious if our EM emissions would have yet reached any potential source of the object...
  - valuearb 9y ago
    Time always matters. Getting information back in 1,000 years instead of 10,000 years is huge. And faster ships aren't necessarily less efficient, in many ways they are more efficient. Chemical rockets are incredibly inefficient.
- Santosh83 9y ago
  > My point is we'd never launch such a slow vehicle > as Oumuamua, because it would be relatively easy > to build a significantly faster one. Even with > todays technologies. There is one plausible reason. If a civilisation had serious doubts about surviving much longer, they might launch a slow ship as a last ditch effort, in case they didn't make it soon after. After all, even we could theoretically keep improving propulsion tech before sending out probes, but that didn't stop us from launching with our best efforts so far, even if only to test. And that's another reason. Maybe this is a test craft... We will never know for certain unless we can send a probe to this rock.
  - valuearb 9y ago
    We could have built project Orion in the 70s to get to another star system in hundreds of years or less. There is no way we'd use chemical rockets, or even NERVA type nuclear to go to another star system, there is simply no hope they'd even get there as anything other than dead hulks in thousands or tens of thousands of years.

What does “viable” mean, though? For us, it might not be viable, but for organisms that live on a different (or even variable) time scale it might be just fine.

valuearb 9y ago

I loved Rendezvous with Rama, and one of it's central lessons is anything is possible when you talk about alien civilizations. We can't assume to know their motivations and technologies. But looking at the basic physics/engineering involved, if it's an alien vehicle it raises some interesting questions and skepticism. Imagine we wanted to build a similar vehicle. If we wanted to send people to nearby stars, we'd likely need vehicles as big, or likely larger, than Oumuamua. If we were in a hurry to do it with present day technologies we'd have to build hundreds of SLS boosters to launch payloads so that astronauts could assemble a vehicle weighing tens of thousands of tons in orbit. And then we'd fuel it with tens of thousand of tons of fuel. So we could build it. What would we use for propulsion? Not chemical rockets, 40KM/sec is only achievable for tiny payloads to fuel ratios with chemical rockets. Maybe we could do it with Nuclear rockets, which were tested and proven to be twice as efficient in the 1960s, ala NERVA. Even then we'd only be able to use a bit more than half the fuel to accelerate towards our destination, if we wanted to stop there. So 40 km/sec would be extremely difficult to reach given how heavy it would be. And at 40 km/sec it would take 8,000 years, nearly a hundred generations before reaching the nearest star. Assuming the life support systems could last that long, they didn't run out of food, water, air, etc. That the engines weren't degraded by radiation over 8,000 years so they would still work when reaching the target. It's extremely unlikely we could count on any of this being true. But if we were ever to launch such a vehicle it would likely be outclassed very quickly. We already know how to build better propulsion systems. Existing ion drives are far more efficient, and theoretically offer over 100KM/sec speeds, we just haven't been able to scale them up yet. If we can scale up ion drives or similar technologies, we already have designs for Project Orion are entirely feasible, and offer massive speed increases. Freeman Dyson's interstellar designs offer 1,000-10,000 KM/sec speeds. If it took us a hundred years to build one, it would likely pass a hundred year old NERVA ship within a year or two. My point is we'd never launch such a slow vehicle as Oumuamua, because it would be relatively easy to build a significantly faster one. Even with todays technologies. So it's reasonable to think that an Alien civilization that could build a ship the size and speed of Oumuamua, could build much larger, faster ships for interstellar travel. If Oumuamua is a ship, the question would be why didn't they? One possible answer if Oumuamua is artificial, that it's not an interstellar vehicle. It's an interplanetary vehicle that had a complete failure of it's systems, and had just enough velocity to leave it's star system, and has been drifting for tens of thousands of years. But in that were the case, how did it came so close to our Sun? It's reasonable to assume that many billions or trillions of asteroids and comets have been ejected by star systems, so that occasionally a few come close enough to ours to make the tight orbit around the Sun that Oumuamua did. But it's hard to imagine there are billions or trillions of space wrecks wandering the milky way such that one randomly passes this close to our sun.

ethbro 9y ago
> If Oumuamua is a ship, the question would be why didn't they [build a larger and faster ship]? Because they didn't know we were here? Supposing you're exploring the galaxy, hyper advanced technology doesn't free you from efficient resource use as a priority until you can easily build enough to explore every star. Given how many stars there are, I wouldn't be surprised if high tech civilizations still used the cheapest ships they could build. I'd be curious if our EM emissions would have yet reached any potential source of the object...
- valuearb 9y ago
  Time always matters. Getting information back in 1,000 years instead of 10,000 years is huge. And faster ships aren't necessarily less efficient, in many ways they are more efficient. Chemical rockets are incredibly inefficient.
Santosh83 9y ago
> My point is we'd never launch such a slow vehicle > as Oumuamua, because it would be relatively easy > to build a significantly faster one. Even with > todays technologies. There is one plausible reason. If a civilisation had serious doubts about surviving much longer, they might launch a slow ship as a last ditch effort, in case they didn't make it soon after. After all, even we could theoretically keep improving propulsion tech before sending out probes, but that didn't stop us from launching with our best efforts so far, even if only to test. And that's another reason. Maybe this is a test craft... We will never know for certain unless we can send a probe to this rock.
- valuearb 9y ago
  We could have built project Orion in the 70s to get to another star system in hundreds of years or less. There is no way we'd use chemical rockets, or even NERVA type nuclear to go to another star system, there is simply no hope they'd even get there as anything other than dead hulks in thousands or tens of thousands of years.