The closest star to our Solar System is called Proxima Centauri and is 4.24 light years away. What kind of ship would it take for a group of human settlers to arrive there in good condition? A team of scientists has just calculated it, and it’s huge.
The problem of traveling to another solar system, no matter how close it is, is that we do not have the means to reach the speed of light. In fact, our space propulsion technology is incredibly rudimentary. It does not matter if we use traditional fuel, if we rely on ion engines , if we take advantage of the gravitational impulse of some intermediate planet, or if we develop some new and exotic nuclear propulsion system . Whatever the method, the estimated time of arrival at Próxima Centaury is thousands of years (between 19,000 and 81,000 years according to this interesting calculation by Universe Today ).
Whatever the system may be, everything indicates that an interstellar trip will become an event that will last many generations. The colonists who leave the Earth will die in space, and their children will be born and will live for generations inside a spaceship. What minimum size does a similar vehicle have to have to support this trip? Astronomer Frederic Marin and particle physicist Camille Beluffi have coordinated a study that tries to find out just that. For this, they have developed a custom software called HERITAGE that analyzes multiple scenarios of reproduction, life and death of a group of human beings over generations.
Let’s start with the population. In order for a group of descendants to reach another solar system without the risk of genetic defects associated with excess family interrelations, the minimum group of departure must be 98 people. The software even takes into account problems of infertility, pregnancy and percentages of loss of the baby due to different natural causes.
The second problem is the feeding. The idea of accumulating food for the entire trip is not viable simply because it is too long. The ship must be equipped to grow or produce its own food. The production of food depends directly on the space available. This in turn depends on the number of people, their height, weight, physical activity and age. HERITAGE calculates the caloric intake for the group of 98 colonists and how much food they need to produce in a year to maintain that intake. Frederic Marin explains to Universe Today :
Using the Harris-Benedict equation to estimate the basal metabolic rate of an individual, we evaluated how many calories per kilogram should be consumed per person per day to maintain the ideal body weight. We take care of including weight and height variations to take into account a realistic population, which includes heavy / light corpulence and tall / small people. Once the caloric requirement is estimated, we calculate the amount of food by means of geoponic, hydroponic or aeroponic cultivation techniques depending on what they could produce per year and per square kilometer.
In order not to miss the shot, the researchers raised the necessary population to a group of 500 space colonists. The land needed to feed this population with the most modern techniques of farming and livestock is 0.45 square kilometers.
If we assume that the ship is designed to generate artificial gravity by centrifugal force (as in a hollow cylinder), the minimum for this cylinder has to be 224 meters radius and 320 meters long. In reality it is not an impossible structure from the point of view of human engineering. Even though we double its length, the resulting cylinder is still smaller than structures like the Burj Khalifa skyscraper in Dubai, which measures 828 meters. The problem, of course, is to send that building into space or build it in orbit.
The minimum size for an interstellar ship is a cylinder with a radius of 224 meters and a length of 320 meters.
Marin and his team explain that there is only one detail that they have not taken into account in their simulation: water. Both the crops and the settlers need water to live and recycling it would not be enough. It would take a method to generate it during the trip. That will be precisely the goal of your next study.
We may not yet need all these calculations, but the fate of the human species is, sooner or later, in the stars.