Since the beginning of space exploration, we have achieved a great many things from successfully launching people on the moon to landing rovers on Mars and Titan, one of the natural satellites of Saturn. Today, we have human-made satellites all over the solar system, but have you ever wondered when we would be able to reach another star? I mean, is it even possible?
Voyager 1, the farthest human-made probe left the solar system a decade ago or so and was launched way back in 1977. After more than 40 years of traveling, the unmanned probe is now at a distance of 21 billion kilometers from the Sun with a steady velocity of 16.99 kps. It is also the fastest spacecraft to leave the solar system.
Some would say, if we can do that, reach the outskirts of our solar system, then we can definitely reach other stars. Well, let’s not jump into any conclusion right away.
Reaching Proxima Centauri, The nearest star to Earth
According to Einstein’s special relativity, the speed of light is the highest limit at which any matter or information can travel in the universe. Although it’s generally associated with light, in reality, it is the speed at which all massless particles travel in a vacuum. The exact value of the speed of light is 299,792,458 m/s.
Four closest star system to the Sun Image Courtesy: NASA
The nearest star to our planet, Proxima Centauri, is more than four light-years away. That means, even the light from the star, traveling at the speed of light (299,792,458 m/s), would take four years to reach the Earth and vice versa.
Due to its relative proximity, the star system has been one of the possible flyby destinations for the first interstellar space travel. Researches have found out that the star is currently moving towards us at an estimated rate of 22.2 km/s. With that speed, the star system will come within 3.11 light-years from the Earth after 26,700 years.
Voyager 1 is currently traveling at a speed of 17,000 m/s relative to the Sun. At that speed, if by any chance the Voyager probe was heading towards the Proxima Centauri, it would take over 76,000 years to reach the star.
The fastest human-made probe to date is the Helios B, launched to study Sun’s process, which recorded a maximum speed of 70,220 m/s or 252,792 km/h.
In case, a probe can attain the groundbreaking speed of Helios B; it would take no less than 19,000 years to reach the red dwarf. The latter sounds better, but it is still not viable.
The current state of space travel technology
The technology we use today is bound to be improved, and that includes the technology we use in space travel. Currently, one of the most advanced forms of propulsion used in spacecraft is the ion drive engine. There was a time when ionic propulsion was considered science fiction, but today it is a matter of reality.
In recent years, the ion thrust technology is used in various ongoing interplanetary missions, including Deep Space 1 and Dawn. It was also used on ESA’s SMART-1 lunar orbiter, which completed its mission in 2006. Now, if we use ionic propulsion in our quest to reach Proxima Centauri, the thrusters would require massive amounts of propellant (xenon).
If we assume that 82 kilos of xenon (maximum capacity of Deep Space 1) drives the prove at a maximum velocity of 56,000 km/hr, then it would take the probe more than 81,000 years to reach Proxima Centauri.
Gravity Assist Method
Apart from advanced thrusters, space travel can also be made faster with the successful implementation of the Gravity Assist method. It involves a spacecraft using the gravitational force of a planetary body to alter its speed and trajectory or path. Gravitational assists are an instrumental technique to conduct space missions outside the asteroid belt.
In 1974, NASA’s Mariner 10 became the first space mission to use Venus’ gravitational pull to slingshot it towards Mercury. Then in the 1980s, the Voyager 1 probe used Jupiter’s and Saturn’s gravitational field to attain its current velocity, which drives it into interstellar space.
Here is what Future Looks Like
EM Drive Prototype
Electromagnetic (EM) Drive
Another popular futuristic concept is the Radio Frequency Resonant Cavity Thruster, or simply, EM Drive. The idea behind this technology is to produce thrust from an electromagnetic field inside a cavity. It was initially proposed by British scientist Roger K. Shawyer back in 2001.
In 2015, scientists confirmed that EM Drive enabled spacecraft could make a trip to Pluto in just 18 months (New Horizons achieved that feat in 9 years). However, researchers don’t have a clear idea of how it would work. Based on that calculation, an EM Drive spacecraft bound to Proxima would take more than 13,000 years to reach there. I think we are getting closer.
Nuclear Thermal and Nuclear Electric Propulsion
Then there is a concept of spacecraft using nuclear engines. An idea that NASA has been pondering for decades. In a Nuclear Thermal Propulsion (NTP) rocket, deuterium or uranium is used to heat liquid hydrogen inside a reactor, turning it into plasma, which is then expelled through a rocket nozzle to generate thrust.
A visual representation of Antimatter rocket
Have you ever heard about antimatter? In case you haven’t, antimatter is a material of antiparticle, with opposing charge of regular particles. Antimatter uses the product of the interaction between matter and antimatter as for propulsion. A report presented at the 39th AIAA/ASME/SAE/ASEE Joint Propulsion Conference and Exhibit indicate that a two-stage antimatter engine powered rocket would need more than 800,000 metric tons of fuel to reach Proxima Centauri.
Although a single gram of antimatter would generate an immense amount of energy, producing that one gram would need 25 million billion kilowatt-hours of electricity and a heck lot of dollars. Currently, human has only been able to create less than 20 nanograms of antimatter to date.
So, it’s clear that unless we make some extraordinary breakthroughs in the area of propulsion, we might just be limited to our solar system, or we have to come up with a scary long term haul transit strategy.