During a recent school visit, a student asked me how long it would take an astronaut to journey to the nearest star beyond our solar system. That would be Proxima Centauri, a small, low-mass star about 4.25 light years from our Sun. Proxima Centauri is part of the Alpha Centauri system, and is itself a red dwarf with a mass just under 13 percent of our Sun’s. Proxima is about one-seventh the Sun’s diameter.
Proxima is about 269,000 astronomical units (AU) from Earth, meaning it is 269,000 times more distant than Earth is from our Sun. At the speed of the Voyager 1 probe (3.5 AU/year), it would take a spacecraft about 77,000 years to cross the distance to Proxima Centauri (Voyager 1 is not traveling in that direction, though).
Voyager 2 is traveling a little more slowly, so at 3.22 AU/year, it will take about 83,500 years to reach the distance of Proxima Centauri. Again, Voyager 2 is not headed in Proxima’s direction.
The fastest human-built craft is the Parker Solar Probe, which is traveling 37.2 AU/year as it swoops close to the Sun in its orbit. At that rate, Parker would take 7230 years to cross the distance between us and Proxima Centauri.
I don’t think I’ll buy a ticket to Proxima on any of these spacecraft, even if they were headed in the proper direction. They’re just too slow. These spacecraft were propelled with chemical propellant rockets, and there’s a limit to how hot the combustion products from a chemical engine can get–and thus how fast the rocket exhaust can exit the nozzle. We need better engine technology if we’re to go faster.
One candidate is an electrically powered (by the Sun or nuclear energy) ion engine, where electric fields propel charged particles from the nozzle at very high speeds. NASA’s NEXT-C ion engine propels its exhaust at up to 90,000 miles per hour, and its efficiency in terms of specific impulse is about 4200 seconds (compare that to my space shuttle main engine’s chemically-driven specific impulse of 452 seconds). The ion engine is at least 9 times more efficient. Given enough propellant and a long-lasting power source like a nuclear reactor, an ion engine might achieve cruise speeds fast enough to cut the trip time to Proxima down to a few centuries.
In the near-term, NASA and the Defense Advanced Research Projects Agency (DARPA) are working to test within five years a nuclear reactor-driven rocket between the Earth and Moon . The Demonstration Rocket for Agile Cislunar Operations (DRACO) engine would heat hydrogen fuel to high temperatures by passing it through the hot reactor and out the exhaust nozzle. At a specific impulse of about 900 seconds, the nuclear thermal rocket would double the efficiency of chemical rockets. A nuclear thermal rocket like DRACO won’t get us to Proxima Centauri (too little fuel, too short-lived a reactor), but it’s a first step to applying nuclear fission, then fusion, to advanced propulsion. Progress toward fusion-driven propulsion is the direction we’ll need to go for practical travel to other stars. Robots will go first, perhaps propelled by lasers or solar sails, but no doubt humans of future centuries will head toward other solar systems to explore and settle.
(Comments on this post are now closed–The Author.)
I am hoping at 74 yrs of age that I may live long enough to see mankind land on Mars! I have always believed that Mars once had water and life. I also believe that we are definitely being visited by more advanced beings. Secret Journey to Planet Serpo by Len Kasten definitely happened and the Ebens have been helping us to advance for decades. Why the coverups? Mankind is so ready to know the Truth and our government leaders have an obligation to reveal it all! Of course in America we continue to allow the daily lies which must stop. Also, knowing that WE are not Alone in this Universe is crucial to our future on this planet called Earth.
Hi Janet:
I agree with you on Mars’ ancient ability to support life, but we need extensive samples from there or human astrobiologists on Mars to get an answer one way or another.
No scientific evidence that I’m aware of points to visits to our world by intelligent beings, but it’s probable in my mind that other technical civilizations exist in our Milky Way. Whether life exists elsewhere is a great scientific question for our civilization.
TJ
Absolutely, & well said….!! Government’s Owe the People of any Particular Nation the Truth about everything pertaining to their Constituents and other Countries as well respectively, & Stop Playing God. That’s what they weren’t elected to do.
Sorry Janet, but aliens don’t stop here, not even for gas. They roll up their windows and try to get past us as quickly as they can. They know that there is no intelligent life here.
I too believe Mars once did have life on its surfac as photos of the surface seem to show dried-up river beds, tributaries and suchlike.
It looks like life may have got going but Martian “climate change” put paid to nascent development.
Could a electro magnetic engine in a small vessel get there faster
James:
We can imagine many future propulsion systems, but none are available in the near future. It’s obvious that a small ship with a more efficient rocket could go faster, but the technological advances necessary are not here yet. I imagine a nuclear-fusion-powered engine with the ability to scoop hydrogen into its tanks from gas-giant planets might be a good approach. — TJ
We are the only habitable zone and inhabitants. No other earth like planets exist. There are no two fingerprints alike, no two DNA alike, facial recognition says no two mug shots are alike, voice recognition, none alike, no 2 snowflakes are alike, identical twins are not exactly the same? So why do we think there are numerous planets like ours just waiting to be inhabited???? Get real.
Gary–
There are an estimated 40 billion Earth-sized planets within the habitable zones of Milky Way Galaxy stars. Chances are good life is out there. — TJ
Jajajaja
So we are the only intelligent beings in the universe?
Good joke
Hello, Friends:
I’m closing further comments on this topic, because it’s about space propulsion, and not about ETs, alien life, government policy, or UFO controversies. Thanks for the comments to this point. See you on my other blog topics. I respectfully request that we stay on topic.
I follow your logic but I think it’s flawed, to be frank.
I’d be astonished if, given the billions of stars in the Milky Way galaxy alone, presumably with planetary systems revolving around them, not to mention the billions of other galaxies each containing many billions of stars and THEIR planetary systems revolving around them too, that many millions do not support life, some of it intelligent maybe, some of it alien animal or plant life.
Would any life on any such planet know of us, billions of light-years away, perhaps?…I doubt it…anymore than we know of any ourselves.
Hi Tom
I am not a astronomer nor a physicist. I am a physician. I read your enlightening article. I tend to agree with your opinion that there are other civizations.Some of them may be more advanced and some not so much advanced. It is my belief that universe is endless with infinite time and space and infinite number of galaxies. Our ability to look other distant galaxies limited due to lack of powerful enough telescopes. JWST just one step in that direction. If we have powerful enough telescopes we can find more and more galaxies out there. All of this discussion leads me to believe that big bang may not be the sole source of universe since it stops the time at some 13 plus billion years. I do not believe that there is a beginning nor an end to universe though this goes against all common and established science.
MRK,
You can “believe” whatever you want; if that is your religion. But the “established science” says there was a beginning, commonly referred to as the “Big Bang”. But the topic is “Space Craft Propulsion”. Star Trek used something called a “warp drive”, which is one of the few things they got right, for we can’t use reaction propulsion to get us to nearby stars in a lifetime. Reaction propulsion (squirting chemicals or ion out the end of the nozzle to use Newton’s 3rd Law of Motion) will never achieve the speeds necessary, but once the speeds are reached, we have to spend the second half of the voyage slowing down. NOTE: Voyager 1 has been traveling for nearly 50 years and has only made it 166 AU. Plus, obtaining speeds that are percentage of the speed of light, means the people on earth will age faster than the space craft occupants. Warping space is a fantasy method of overcoming the need for speed, but will require enormous energy.
If you can travel x amount of light years in one direction who’s to say what is or isn’t out there, we humans may never know, I study the skies with a telescope, but that only goes so fari for one would really like to know I do believe that the government knows a lot more than what we think they do, but at so many light years away I don’t think they even really know, there could be aliens among us, if so how would we know the universe is very interesting, and I would like to know more about it someday,, but until then I will keep searching for as long as human time will allow, who knows maybe there is something closer than we think we just don’t know it.
I would like to have seen that students reaction. I find the fact it will take Voyager 77000 years terrifying. The Sun is less than a millimetre away really. Andromeda? Local galaxy. millions of years travel. Owch.
Personally, I believe we could go way faster than even the fastest spacecraft out there. Of course , using the Sun to propel us would be a good start obviously you can go about 10 times faster than the voyagers, then you have to throw in some theoretical things that are probably not too far distant future using lasers wind sails or even some sort of plasma and thermonuclear power. But yes at our current technological rate it would take way too long. However, in 5 or 10 years we might be able to cut it down to a much faster rate and get to closer to the speed of light. Using the Sun as a slingshot and then using a combination of wind sails, lasers or even some kind of nuclear power which we’ve never used before we could drastically condense space travel. It’s obvious that chemical propellants won’t do the job, they’re too heavy for liftoff and they don’t get you fast enough. I read an article recently saying that if he used lasers or wind sails that we could get there in 75 years. Again it’s theoretical but I believe that the technology is very close. So I think it’s very disheartening to tell children that I would take 75,000 years based on technology from 1977. I think your article said if we use the same slingshot technique that the one probe used that we could get there in 7,500 years. But If we used lasers or wind sails or other technologies guess what that moves the decimal point a few places over now doesn’t it….. All I’m saying is within a few decades or even sooner we could get there much faster.
I love science fiction as much as any other space fan but I do think it’s given people the impression that human space travel between planets, stars, and even galaxies should be easy and quick—perhaps even near instantaneous. This is great for stories that are about the travelers, not the travel itself, but space is incredibly (i.e. mind-bogglingly?) big and it’s possible that 1. faster-than-light travel physically cannot happen, now or ever by anyone, and 2. even light speed itself is unreachable by any physical object of mass (and let’s add in 3. even if it is obtainable through some as yet unknown loophole in physics, the travel process itself could be extremely destructive to a vehicle and crew or even those nearby.) These are unfortunate ideas for anyone eager for warp drives and wormhole trips between planetary systems, but it could very well be that the Universe is just too big for human-scale convenience. We may be limited to local planets and moons—or at best local star systems and generational ships where one’s ancestors (hopefully) reach the destination. Still, I do hope humans can someday find a way to work together toward such a goal—that would be the real achievement as a species.
Currently 5500 exoplanets have been observed. While our present technology do not allow for detailed analysis, none have shown anything similar to being habitable.
For an indefinite time mankind will be limited to our solar system’s planets and moons.
I think that at the moment Fission is our best bet as at least we can do that in a controlled manner with Fusion we can’t and there’s no real evidence of any real advancement.Fission would cut the transit time from Earth to Proxima down to a few hundred years rather than 8000.Of course it still has major problems not least at the moment small Fission reactors don’t exist, the you have the fuel, maintenance (assuming that it’s uncrewed) and one big matter how to stop when you arrive!
Thank you, Dr. Jones for your contributions to our nation’s defense, our space program, scientific discovery and for this blog.
I do respect your mandate that posts should remain on topic – propulsion – however, this leaves me with a question; If the various (video supported) observations of UFOs, UAPs, USOs, etc. by qualified personnel including military pilots “can be” believed then the only reasonable conclusion is that these are non-human visitors. If so, does this not support the idea that interstellar means of travel/propulsion/positional translation DO exist ? And so the “ET issue” (however distasteful, academically) actually may have relevance to the discussion. i.e., If they can get here by whatever means, then some such means do exist. ( Big if, granted ). It does seem likely that such travelers would be of species much older than humans- perhaps billions of years more advanced?
Hello, Capt. Gilje,
Yes, people see things in the sky. My own opinion is that if the sightings are real, the simplest explanation is that they are advanced terrestrial craft. I like to think we have a few technical secrets in our portfolio that are not public knowledge. But I am open to the possibility of intelligent life elsewhere. If we find concrete evidence of their presence, let’s consider it. The sightings so far don’t convince me. See: https://www.kpbs.org/news/2025/01/21/nova-what-are-ufos for some alternative explanations.
Friends:
Comments on this blog post are now closed.
Thanks for your interest.
Tom Jones