Wow, that's really close so far as these things go. With the nearest star being 4ly, this can be reached with essentially the same tech level if we'd want to visit that with a rover or generational ship one day
We'd need some fast tech for sure. However, what is also interesting is that the light from it is only 124 years old. So the planet is still very similar today probably.
> this can be reached with essentially the same tech level
I'm not so sure about that. I mean, at the moment both are impossible, but it's much easier to imagine traveling 4ly than 124ly. 4ly can be reached in a single lifetime if you accelerate a shop to .9c, which is technically possible. 124ly is going to be a multigenerational undertaking no matter what. The 248y communication lag is also a much bigger obstacle than an 8y lag.
I think once you can travel 124ly, you can travel 1000+ ly. You need to be completely self-sufficient and you're going to lose contact with home anyway. If you send a robot, you're not going to hear from that robot again in centuries, if ever.
Fair points. It's all guesses about the unforeseeable future, but I would estimate that a multigenerational ship is in arm's each if we really wanted to, whereas accelerating so much as an orbiter (let alone a lander, or a whole rover, or a live person) to 0.9c probably requires a tech level we don't have due to the fuel requirement for deceleration. Maybe a fly-by could work, then burst back the results with some enormous amount of energy, but that's a lot of cost for very little information.
When making a generational ship, for safety we'd still want to do years of testing on orbit to see whether a chosen ecological system really does form a closed loop. Water recycling on the ISS is 98% efficient according to NASA, so with refuelings from ice moons every couple decades (solar system hopping) that should be covered. Ion engines are apparently also a thing (still sounds like science fiction to me, but they've been in production on space missions for a long time apparently!), I don't know what kind of longevity those have though, or whether refueling is realistic (might requires landers with expansive equipment for refinement of elements). Things like floor space, the way that I see it, that's a matter of cost more than a matter of ability, so having enough privacy so you don't kill each other is within our current tech level – again, iff we'd really care to do this. Hence I'd say we can do this nearly today, and then it also doesn't matter much if you need 400 years for 4ly or 12'400 years for 124ly.
On the other hand, by 10k years from now, I would think we can make a 0.9c human-sustaining craft, so maybe you're right that we'd rather choose to wait a thousand years and see where things stand then rather than putting effort into launching a generational ship next century, whereas with a 4ly target the generational ship is much more likely to be faster. Maybe you're right that this distance difference does matter. Not for ability so much as for psychological "would we spend that effort given the perspectives" reasons
Even worse if we are still limited by Newtonian dynamics it will take thousands of years for a probe to reach there. The rocket equation is a harsh mistress. In practical terms we will never visit that world without completely upending physics as we know it.
The problem is when you work out the math on rocket that can sustain 1G for multiple days with any Earthly isp you realize the math just doesn't work. Even if you go nuts and plug in a number like 1 million seconds (our best chemical rockets are more like 450 seconds) for the isp it is still nowhere close to feasible using only the mass of our solar system.
As long as you are stuck flinging mass out of the back of your rocket to accelerate you don't get to go anywhere outside of our solar system.
A beamed core proton-antiproton rocket could produce millions of ISP and allow accelerations of up to 0.7C, using relativistic mesons as the reaction mass. It is entirely theoretical though.
>The problem is when you work out the math on rocket that can sustain 1G for multiple days with any Earthly isp you realize the math just doesn't work.
>our best chemical rockets are more like 450 seconds
If we're talking about leaving the Solar system, and 1G rockets, why on Earth would you ever even think about primitive chemical rockets? Obviously, nuclear rockets are a mandatory first-step before getting close to that level of technology.
And given that we already have nuclear power plants, as well as designs (untested) for nuclear rockets, why even bring up chemical rockets?
Dyson proposed a fusion pulse propulsion system in the 1960s that was estimated at 70000 isp. Maybe 1m wouldn’t have been that far off from the limits of these crafts if test ban treaties didn’t kill their development.
Would it melt before then? Interstellar space is extremely thin, on the order of 1 atom per cubic centimeter (estimates vary). But, as we learned when Voyager finally left the solar system a few years ago, it is hot as hell. More than 54,000 degrees F according to National Geographic:
The Voyagers didn't have today's ion engines. I don't know how much that gains us, though, as the main speed gain was by leeching momentum from planets' momenta, rather than from the hydrazine thrusters it carries
Orion drives can get up to some respectable fraction of the speed of light. Just need a billion or so 1-kiloton nukes. No biggy. No worries about sneaking up on them and startling them either.