Image taken from the movie Interstellar as the ship enters the wormhole.
For thousands of years, mankind has looked up to the sky and dreamed of one day visiting the stars. As human beings, curiosity has always driven us to explore untouched territories and set foot in unknown places. Although we have demonstrated that we have the technology to send spacecrafts into interstellar space in direction of other solar systems, how long will it take to reach them and what does this mean for our future exploration missions.
Our current advancements
Artist rendition of Voyager 1 as it enters interstellar space. Credits: NASA
At the time of writing this article, there are a total of 5 spacecrafts that have either already left our solar system or are on a trajectory to do so; the oldest one being Voyager 1. The Voyager 1 spacecraft which was launched in 1977 is now approximately 23.5 billion kilometers away from Earth traveling towards the star closest to our sun: Alpha Centauri C, otherwise known as Proxima Centauri. Although it is traveling at a speed of about 17 kilometers per second, it will take the spacecraft about 16,000 years to reach the star.
One interesting aspect regarding this destination is the exoplanet Proxima Centauri b, which rotates around its star and is located in its habitable zone.
The habitable zone is the area around a star where it is not too hot and not too cold for liquid water to exist on the surface of surrounding planets.
Therefore, finding a planet located within this zone is a good indication for the presence of water, which as we know, is essential for the existence of life.
To put this into comparison, the habitable zone for our Sun starts after Venus and ends after Mars. However, as the Sun ages and most of its Helium and Hydrogen are consumed, the Star will expand into a red giant, therefore naturally extending this habitable zone to a new range, as seen in the image below.
Current and future habitable zones for the Sun. Credits: Cornell University.
The wait calculation
The issue concerning such long interstellar travel is that due to our technological advancements increasing at an exponential rate, it is probable that a spacecraft sent at a later date would actually arrive earlier than a spacecraft that was to leave tomorrow.
Let's say that NASA was to send an expedition crew to Proxima Centauri b this month and that it would take the spacecraft 16,000 years to reach its destination. It may well be that in 500 years we develop new propulsion methods that enable us to travel 5 times faster than what we can achieve with our current technology. Therefore, the crew that left this month would arrive at the planet only to find out that it has already been colonised by humans for thousands of years.
The wait calculation involves trying to determine the optimal time to wait for technological progress to improve spaceship speeds, before committing to the journey
If you are interested in finding out more about the wait calculation, you can check out this YouTube video where it is explained in greater detail.
What about wormholes or portals ?
Depiction of how a wormhole alters the fabric of spacetime. Credits: ISTOCK
Just like in Christopher Nolan's Interstellar, we all wish that we could travel very long distances with the use of wormholes, where the fabric of space and time is modified to our advantage. This, in turn, would enable us to get from point A to B much quicker than light would in normal conditions. However, there is currently no evidence for such a phenomenon and we are therefore left with our own propulsive technology.
In 2021, NASA launched the Double Asteroid-Redirection Test (DART) spacecraft, which is propelled by the NASA Evolutionary Xenon Thruster (NEXT). This spacecraft utilises in-space electric propulsion and has the ability to generate electricity through the onboard solar panels to accelerate Xenon particles at a speed of 145,000 km/h, or 40km/s.
NEXT (ion thruster). Credits: NASA
Can we be cryogenically frozen ?
Image taken from the movie Passengers showing the pods where the crew and passengers sleep. Credits: Columbia Pictures Industry.
If you've watched Morten Tyldum's movie Passenger, then you probably know what this would entail. If not, being cryogenically frozen would involve safely freezing and thawing our bodies in order to preserve life functions on a journey longer than life expectancy. Alcor Life Extension Foundation now has the ability to cryogenically freeze human corpses and brain in liquid nitrogen and hopes to one day restore them to full health if new technology is developed in the future.
Is all of this realistic ?
No person who is currently reading this article will probably see one of the space agencies fill a spaceship with people and send them to Proxima Centauri. Mainly due to our technological limitations and the large timescale which is required to consider. However, if mankind one day hopes to migrate to a new system, then it will have to happen.
This article was written by Chris Chellembrom
Chris is currently undertaking his MSc at Politecnico di Milano in the field of Space Engineering. Having years of academic experience in the space sector, he hopes to transmit his knowledge and enthusiasm to the younger generation and adults unaffiliated with STEM.