Three methods to reach Alpha Centauri that don’t require wormholes or warp drive
In 1977, two spacecraft were sent outward from Earth and the sun in a first-ever journey to the depths of the solar system. In the nearly forty-four years since Voyagers 1 and 2 were launched, they have not only accomplished their original goal of sending back photographs and data about the four giant outer worlds of our solar system, but have succeeded in going where no other human-made objects have yet traveled — into the interstellar medium.
It was first reported by NASA in 2012 that Voyager 1 had crossed into a new region of space marking the wide and ephemeral boundary between the sun’s domain and the rest of the galaxy, and in the years since both Voyagers have returned mountains of data to their controllers back Earthside.
This is big news, to put it mildly. For at least as long as humans have written modern science fiction, and certainly longer than that (with a specific mention of such dreamers as Giordano Bruno and Johannes Kepler as examples), we have dreamed of traveling beyond the reach of our home star and exploring other planetary systems.
Indeed, ever since it was definitively proven in the 1990s that other stars can and do harbor alien worlds, the yearning to go there has loomed large in our collective unconscious. With the news of ever more discoveries of increasingly Earthlike planets around foreign stars coming in virtually every week, the day would seem to be near at hand that this dream may be realized.
But this is where we run into that old obstacle posed by the laws of physics: thou shalt not travel faster than the speed of light. Why is this a problem for travelling to the other stars of our galaxy, you might ask? Especially when the nearest ones, such as the trio of stars making up the Alpha Centauri system, are practically next door by cosmic standards?
The answer is simple: close by cosmic standards does not mean close by human standards, and that is putting it mildly. Even the aforementioned Alpha Centauri, at approximately 4.3 lightyears away, would take the Voyager probes roughly 70,000 years to reach (if they were even headed that way), and that is at their current speed of roughly 35 thousand miles per hour.
If our aim is for more distant stars, such as those discovered by the Kepler space mission and other deep space planet hunting programs, that distance (and as such, the time table) only increases in magnitude. Suffice to say, current rocket technology is insufficient to get us to even the closest other stars on anywhere near a human timescale.
So what can we do about this? Looking back on the already discussed prevalence of human exploration of alien star systems in science fiction, we might expect that some miracle technology, perhaps not yet available but at most a few decades to a century away, will enable our realization of this fantastic voyage to the stars.
But not so fast: warp drives, wormholes, and more outlandish sci-fi staples such as teleportation (quantum or otherwise) are not only far from the scope of our current technology, they may all be impossible by any standard of known or yet-to-be-known physics. In the end, Einstein always wins.
So, if we cannot simply warp space or drop through a wormhole to the other stars of our galaxy in the search for new worlds and new civilizations, is the quest itself doomed before it begins? Luckily, the answer is no.
There is still the matter of time tables to take into account, however. Barring a miracle discovery such as controlled hibernation, mind-body transfer, or the like (all of which seem in some ways as unlikely as faster than light travel itself), an alternate route must be found or blazed to the stars, and it will take time. The only question is, how much time are we willing to take?
In this writer’s opinion, there are three options: we may take the long route, based around indirectly hopping from asteroid to asteroid, dwarf planet to dwarf planet as we spread slowly out from our own comfortable corner of the solar system; the direct-but-slow route, by which we build massive ships meant to travel straight to their final rendezvous (and travel so slowly that they would necessitate multiple generations of human settlers living and dying within); and, perhaps most daring, the fast-direct route, in which novel yet completely feasible technologies are utilized by our near future descendants (or even our children and grandchildren) to conquer the stars.
The first concept we will overview is the slow and indirect method. As has been pointed out by such minds as Freeman Dyson, this concept is one which dates back much farther even than the concept of travel to other parts of the galaxy, or the solar system for that matter. In fact, its origins may be found in that great island-hopping migration by the ancient Polynesians as they spread by boat across the Pacific, stopping and setting up new societies as they went and leaving a fleet of nation-states in their wake.
The modern concept of island hopping to the stars is not much different, save for the distinction that, by necessity of the vastness of space, it takes place on a much grander scale. Whereas the Polynesians crossed tens of thousands of square miles on their simple catamaran ships, those wishing to hop between resident comets in the Oort Cloud on their way to Alpha Centauri and the other nearby stars will be crossing literally trillions of miles of space.
This should not necessarily dissuade modern humans from attempting the journey, however. Just as the vastness of the Pacific did not prevent the ancient Polynesians from traversing as far from their first point of departure in Southeast Asia and the Philippines as Hawaii and Easter Island, the concept of setting up shop on drifting comets and asteroids at the edges of our own domain and riding them across the wide gulf of space until we reach the alien shores of planets orbiting stars such those of the Alpha Centauri system must ultimately be seen not as an impossibility but as a challenge if we are to achieve the goal of taking root in more than one star system.
The next concept to be covered is the slow but direct method, or in other words, the generation ship. For reference, we must remember that methods of sailing to the New World took long enough in the last great age of human exploration colonization that children could be born aboard ships. Generation ships take this to the ultimate extreme, by playing upon the idea of sending a vessel to the stars which is explicitly designed not to travel fast enough to shrink the voyage to less than one human lifespan.
To elaborate, we should begin by picturing the ship itself. First and foremost, we must understand that such a ship would not be small or compact. In fact, depending on the exact specifications of the design employed, it could be so vast as to require assembly in orbit. But this size is necessitated by the fact that such a ship must keep a crew of hundreds (and possibly thousands) or people comfortable, nourished, stimulated, and secure for the potentially multi-millennia voyage to the destination star. The simple fact of growing enough and processing enough water & air for so many people would necessitate a ship larger than any ever constructed by humanity.
The good news is, we already have concepts on hand that could meet such criteria. In the mid-1970s, a pioneering scientist and space enthusiast named Gerard K. O’Neill wrote a book in which he described “island habitats” in space, which would be built completely from scratch in the vacuum out of material harvested through space mining initiatives.
One of these, the “Island 3” or O’Neill Cylinder habitat, meets all the needs of a generation ship — its huge size can home, feed, and enrich thousands of humans for potentially many centuries, so long as maintenance crews remain diligent — and would require only a method of propulsion to reach the nearby stars. This would surely be easy to accomplish for any 22nd century civilization willing and able to build the generation ships in the first place, especially as a means to achieve interstellar exploration and settlement.
As was previously stated, the last method to be addressed is perhaps the most sensational, is certainly the most daring, and may in the end prove to be our best bet for reaching the worlds of our neighbor stars.
While such technology as warp drive may be centuries off (if it is even possible at all), these technologies are all technologically sound, if unproven in actual physical trials or shakedown flights, and could be accomplished by the end of this century if the collective will and resources of humanity (or even a few especially wealthy nations) were to draw together toward that end.
The secondary benefit of these technologies is that there are a myriad of them. One of those which actually went far enough to be proof-of-concept validated (and as far back as the 1960s, no less) is nuclear pulse propulsion. This method acts upon the classical Newtonian principle that for every action, there is an equal and opposite reaction — in this case, the action is exploding nuclear warheads behind a concussion plate at the rear of the starship, and the reaction is the generation of great thrust, which allows said starship to sail to other star systems on a wave of thermonuclear force.
However, as one might expect, there are two major failings in the nuclear pulse propulsion concept: for starters, the concussion plate used to deflect the majority of the blast away from the crew compartment of the starship and thereby generate the “pulse” or thrust could potentially deform or even break down through use, with a laundry list of problems arising as a result; secondly, the Nuclear Test Ban treaty of 1963 prohibited the use and testing of nuclear weapons in space, effectively shutting the door on any further development in the research into this method of spaceflight.
An alternative arises in the form of nuclear fusion. An alternate program conducted between 1973 and 1978, called Daedalus, involves the use of near-future thermal fusion technology (and another truly massive ship design) to propel a craft to a substantial fraction of lightspeed. By this method, nearby stars such as the Alpha Centauri trio could potentially be reached within one human lifetime. This in turn would nullify the need for sizing up the ship to accommodate generational voyages, and could even make its use financially feasible as a means to reconnoiter other systems prior to settlement.
There is one more fast-direct method we will discuss today, involving a technology that is commensurately less proven but more lucrative than all the others. As seen in the image above, the Bussard ramjet is a means to travel to other stars without the need to pack your own fuel beforehand.
This is because the interstellar ramjet design (as first proposed in 1960 by physicist Robert W. Bussard) utilizes a massive — think something on the order of many dozens of miles in diameter — scoop to pull in hydrogen from the interstellar medium, which is then utilized for a fusion reaction that in turn spits high-intensity propellant out the exhaust nozzle.
An added benefit of this is that, thanks to the fact that the fuel used for spaceflight is captured more or less constantly during the journey, a constant one-G acceleration may be employed. This in turn has two major benefits for the travelers: because the ship may accelerate at a constant one Earth gravity, the crew complement would experience Earth gravity during their journey, thereby rendering the dangers of microgravity spaceflight null and void.
Secondly, the reality of one-G acceleration is that, within the span of only a year of travel, the vessel itself would reach a high percentage of lightspeed. This in turn would render a great deal of time dilation upon the crew, meaning that virtually any journey within our galaxy (or, as Carl Sagan pointed out, outside it) would be possible within the crew’s lifetime.
This is because, as Einstein described over a century ago, the faster you go relative to light, the more time slows down from your perspective. In other words, to reach the stars of Alpha Centauri would take about 5 years from the perspective of Earth, but less than 4 from that of the crew aboard the ramjet vessel which took the journey. As such, the old island hopping method could be employed once again, albeit with ships fast enough to reach the stars within one generation of the onboard passengers.
As we have seen, the methods to travel to, explore, and possibly even settle other star systems and the worlds therein is not only feasible, but may indeed be attainable within our own lifetimes. The only remaining question is whether or not we desire this goal enough to pursue it, or if we are content to remain a single-solar system species. In the end, the choice will likely rest with our descendants, and the decision will be left to them on whether or not our species’ ancient instinct to explore the unknown and conquer the unconquerable shall be left as part of the refuse of our history.