# How long could it take us to reach Alpha Centauri with current technology?

I was searching somewhere on how far away the nearest star system was and what that system was. Am I correct in that it is Alpha Centauri at roughly 4.75ish lightyears? If so, a probe or ship or whatever we send could reach there in a relatively short amount of time, right? Please tell me if I am wrong.

• Alpha Centauri is 4.37 ly from us; one component of the system, Proxima Centauri, is a third, small star orbiting the others (αCen A and B) distantly and is only 4.24 ly from us (and will remain the closest for a while, as its orbital period is half a million years). Jan 3, 2019 at 3:23
• I don't think we can reach Aplha Centairi with current tech, on any timescale. It has a relative motion to our Sun of some 41.3km/s, and while sortof approaching at present will very soon (25000years) be moving away from closest approach. To send a probe there, we would need to send it as 41.3km/s plus whatever speed we add to decrease the distance. And right now, 41.3km/s is more than out best sol escape speed achievable, which is in the 20km/s class. Dec 16, 2021 at 19:11

Current technology can't get us anywhere close to the speed of light (c); the Voyager probes are moving at something on the order of 1/17500 c. At speeds like that, it's about 75,000 years to Alpha Centauri.

There are proposals for small probes accelerated by laser-driven light sails to speeds on the order of 15% of light speed -- 25 years to Alpha Centauri -- but there are a large number of engineering challenges in building such things that we haven't even begun to solve.

• And it is important to note that "small probe" in this case means centimeter-sized, weighing a few grams. Transporting much mass makes it an even harder engineering problem. Jan 3, 2019 at 20:40
• Also current starshot-like proposals don't plan on stopping or slowing down at Alpha Centauri, just a quick flyby Jan 4, 2019 at 20:59
• Aliens will be asking us why we threw a penny from our solar system to theirs. Jan 6, 2019 at 0:01
• @MagicOctopusUrn Unless they have already done so. I'm pretty sure it is unlikely that we would detect that size of a probe if it flew through our solar system. Of course, in theory comms might be detectable, but that assumes they use a type of communication that we're looking for in a way that will make it show up easily. Jan 7, 2019 at 14:16

The JHUAPL Interstellar Mission proposal uses minimal development of current technology (mainly qualifying a large solid upper stage) to achieve a speed 4x higher than Voyager, so on the order of 18750 years to get to Alpha Centauri.

The British Interplanetary Society has spent some time looking at this, first with Project Daedalus 1973-78 taking 50 years to flyby Barnard's Star (5.9 ly) and in a high degree of technical detail in Project Icarus 2009-14 which spawned the Initiative for Interstellar Studies - i4is.org

Numerous papers have been published as a result of this work.

• Daedalus is supposed to use a fusion engine, that we don't know how to build. Does not count as current technology per the question. Jan 4, 2019 at 4:43
• The project was to use current or near-future technology; they thought they knew how to build such an engine.
– user20636
Jan 4, 2019 at 22:36
• My apologies! I remembered wrong. Deleting comment. Jan 4, 2019 at 23:42
• What is the basic theory behind a fusion drive? I have heard of these before but never fully understood them. Jan 7, 2019 at 2:31
• See the link in JRCM's answer. Basically a series of tiny fusion bombs would be exploded. Jan 7, 2019 at 7:45