Human beings are explorers by nature. We look at the stars and we can’t help that itch to discover remote things that Melville was referring to in ‘Moby Dick’. But to get out of the solar system, the current technological means barely reach us, and you have to use theory and mathematical formulas to find a way to shorten the enormous distances that separate us from other stars.
One of the scientists who do it is Kelvin F. Long, a British physicist and aerospace engineer, director of the Initiative for Interstellar Studies and author of books such as ‘Deep Space Propulsion: A Roadmap to the Stars’ (‘Propulsion for deep space: a roadmap to the stars’, in Spanish ).
In this book, Long proposes a rigorous analysis of the different technologies that have been proposed so far to achieve engines that allow us to make interstellar travel. In his lecture for the Space Studies Institute (Instituto de Estudios Espaciales, in Spanish), Long gives a brief summary of the main space engines. Obviously, many of these technologies are still on a theoretical level and require a level of technological maturity that we have not yet reached.
Summary talk of Kelvin F. Long’s book
Long distingue four types of motors that use the elements in space: energy, mass, space and time. Power Driven Motors, which are the ones we use right now and that push the aircraft upwards by burning the fuel stored inside it. Those systems, Long says, can range from chemical to fusion or antimatter systems.
Mass Driven Motors They do not need to carry the fuel inside the ship, but rather that mass comes from an external energy source. They can be mass drivers, particle beams, lasers, or solar.
Engines powered by space They do not carry fuel in their aircraft and neither does it come from outside, but they collect hydrogen or other compounds that are found on the road and use them as a source of energy.
Time-Driven Engines They would be the most exotic for Long, because they are very theoretical and in some cases defy the laws of relativity. Examples of this type of engine would be those of propulsion by distortion, the holes of worm or the trips in the time.
We are not going to analyze all the examples here because it would be too long and that is what Long’s book is for, but we are going to recall some of the most prominent to see where the shots go.
The Orion Project was developed in 1958 by Freeman Dyson. The idea was propel your engine thanks to a series of nuclear bomb explosions at the bottom of the ship. The project was scrapped a few years later out of concern about the possible consequences that nuclear detonations could have on Earth.
It was a project carried out by the British Interplanetary Society in the 1970s to create an unmanned interstellar probe for scientific use. The rocket would use a deuterium / helium-3 mixture to achieve fusion necessary for its propulsion. The conditions set by its creators during its design were that the ship must use existing technology and be able to reach its destination within a human lifetime.
We recently saw a study here that proposed a new fusion engine that uses the same principles as solar flares to power spacecraft. It is called the principle of magnetic reconnection and it is capable of obtaining energy through two isotopes of hydrogen, deuterium and tritium.
This theoretical engine uses energy emitted by a beam from outside the spacecraft to propel itself. The beam can come from a laser or microwave and can be pulsed or continuous. Physicist Robert L. Forward proposed in 1989 a concept that used a solar sail to reflect a laser beam. This idea, called a laser-powered light sail, promised to be a lightweight interstellar travel method that did not involve carrying fuel.
Black hole radiation
This idea, first proposed by Arthur C. Clarke in his book ‘Imperial Land’, consists of artificially create a black hole and use it as an energy source to propel an aircraft. The concept is entirely theoretical, but in 2009 scientists Louis Crane and Shawn Westmoreland analyzed this theory and concluded that it was possible to create an artificial black hole, although the consequences of its construction would be totally unpredictable.
This theoretical propellant was proposed for the first time by the Mexican astrophysicist Miguel Alcubierre in 1994, and it relies on the expansion and contraction properties of the spatial fabric to achieve superluminal speeds.
The big problem with his theory is that it would require a large amount of negative energy to propel itself and today there is no scientific evidence that this type of phenomenon exists. But a recent article proposes a new approach that does not require the use of negative energy. That would make it possible, although it is still unlikely that we will see it come true.
For Kelvin F. Long, the only feasible means with the technology we have is the fusion engine, although there have been theoretical advances in other models. Long himself has made a timeline with all the steps that must be followed so that we become a species capable of going beyond our solar system. The date is 2111 and even Long himself considers it too optimistic. So much anti-aging techniques are going to have to advance for us to have any chance of seeing it.