Under optimistic projections, we will set forth on the first interstellar voyage before 2100, perhaps within the expected life span of today’s children. According to pessimistic projections, for all intents and purposes human interstellar travel is impossible, and the reality is that “you can’t get there from here.” The problem, given present-day technology, is distance. Distances between the stars (including our own Sun and its neighbors) are measured in light-years. Since light travels at the speed of 300,000 kilometers per second, one light-year is almost 10 trillion kilometers. (A trillion is a million million.) With the exception of astronomers, who are taught to think big, it is almost impossible for people to grasp the enormity of such distances. Eugene Mallove and Gregory Matloff note that the nearest star, Proxima Centauri, 4.3 light-years from here, is about 273,000 times the distance from Earth to the Sun. 1 If we represent the Sun by a circle with a diameter of 1 centimeter, Earth would be a dot with a diameter of .1 millimeter, located 1 meter away. Pluto would be 42 meters from the Sun, and Proxima Centauri would be 292 kilometers farther out.
The challenge of interstellar travel is covering immense distances within a time frame that keeps the journey meaningful. We have already launched interstellar probes. Pioneer 10 and 2 have completed their work within our solar system and will make their closest approach to other stars as early as 32,600 or as late as 497,000 years from now. 2 Since their primary function is to explore our solar system, they are not taking the most direct route to our nearest neighbor. If we could travel at the speed of light, then 4.3 years’ travel time to Proxima Centauri might not be too bad. Given what we know right now, however, we can’t come close to this. Estimated starship speeds are measured in hundredths of the speed of light, and a ship that topped out at .06 times the speed of light would be a snappy performer. Yet because it would take years to accelerate to this speed (and years to decelerate in order to stop at the destination) average speed would be much lower than this. By many estimates, even a “short” interstellar voyage could take centuries. This might not bother an automated probe, but could cause problems for humans.
Detailed planning for interstellar spacecraft has been under way since before the first orbital flights. Over the years, many different designs have been brought forward. Some of these are based upon optimistic predictions about future science and technology, but others involve either known technologies and construction techniques or ones that should soon become available. Like airplane, ship, and automobile designs, starship plans reflect trade-offs among size, fuel requirements, and speed. Without question, nuclear rockets are the most promising.
We can divide interstellar missions into two categories: multigeneration and single generation. All starship designs that use known or reasonably demonstrable technologies will require multigeneration missions, but some, known as slowships, will require more generations to travel to a given star than will others, known as fastships. As for singlegeneration interstellar missions, many space scientists would say that we have only hazy or wishful ideas about how to accomplish them, if they are possible at all.
This Brings us to the most fundamental and critical question regarding the interstellar migration. If a multigeneration Interstellar ship were to leave for another solar system today, would you consider volunteering for the greater good of humanity? Use the opinions poll and let us know!
In the meanwhile, enjoy these artist's renderings of futuristic interstellar vehicles.