Think antimatter can’t be used for propelling a rocket? Well, think again.
What if I told you you could travel at something around 40% the speed of light or around 120,000 km/second? Well, grab a chair, some popcorn, a drink and make yourself comfortable because this will blow your mind. When I first learned about this, it sure did blow mine away.
To put that into perspective, the fastest spacecraft we have ever launched is Voyager 2, travelling at 15 kilometres per second.
The technology that makes this possible is antimatter propulsion. With the help of this kind of propulsion, we could travel to Alpha Centauri, the closest star system from us in less than a decade; it is four light-years away.
What Is Antimatter, You Ask?
Before we even get into any of the technical stuff of how antimatter propulsion works, we must first understand what antimatter is.
Antimatter is, well, it’s antimatter. Literally. They are particles that look the same and have the same mass as their normal counterpart, but the only thing different is the charges.
When matter and antimatter interact with each other, they annihilate each other as they have different charges of the same particle. The antimatter versions of parts of atoms are called positrons for antielectrons, antiprotons for protons, and antineutrons for neutrons.
Discovery of Antimatter
The first theory of there being antimatter was published in 1928 by Paul Dirac. Until then, it was thought that only positive energy existed, not its counterpart.
Later on, in an experiment, Carl Anderson observed a particle that had the same mass and properties as an electron; the only thing different? The charges. They were positive. He dubbed this particle as a positron.
We now understand that all particles have both positive and negative counterparts. However, antimatter is significantly less than matter in the observable universe. When the universe was formed, there should have been an equal distribution of matter and antimatter, and therefore nothing should exist. But the universe does exist, and why this is so, is one of the greatest mysteries.
How Antimatter Can Be Created
Antiparticles can be created either naturally or artificially.
In nature, antimatter can be created anywhere where there is a high energy particle collision due to collisions of high-speed particles called cosmic rays. Artificially, scientists can create antimatter in labs. On Earth, we create it manually with the help of immense machines that smash together atoms called particle accelerators.
These machines are traditionally used to uncover how the universe works, but they can also be utilized as “antimatter factories.”
Antimatter is the most potent fuel to be known yet. The fact that all the reaction converts to complete energy is what makes this fuel so powerful. The particles annihilayte with eachother, leaving no room for any of the energy released to go to waste.
Positron Fuelled Rocket
Now that all the context of antimatter is out of the way, let's dive right into the cool stuff. The actual rocket fuel!
While tons of chemical fuel is needed to propel a human mission to Mars, just a few milligrams of antimatter will do the job and in a much faster and a much more efficient way.
Antimatter weighs extremely less in comparison with normal fuel, with one milligram weighing at just about one-thousandth the weight of a piece of M&M candy.
To travel to Alpha Centauri, the closest star system to us, it would take only 17 grams of antihydrogen. That is significantly less than the fuel it takes to get to space currently.
How It Would Work
Normally, the idea for antimatter propulsion has been to take as much of the energy from the annihilation of the particles as possible, and use it to heat hydrogen to high temperatures that are blown out of a rocket. We would use the antiproton as a spark plug to induce fission.
A term given by nuclear scientists, “fission daughter” byproducts emerges from this fission.
Each antimatter annihilation releases about 2 billion electron volts of energy, about 2 GeV.
An antimatter rocket that is launched just outside of the Earth’s atmosphere could provide a lot more thrust than a chemical or even a nuclear rocket using tens of thousands of times less fuel.
There are three main components to a matter-antimatter engine; the magnetic storage rings, feed system, and the magnetic rocket nozzle thruster.
In a magnetic storage ring, antimatter must be separated from normal matter. This helps the storage rings with magnetic fields move the antimatter around the ring until it is needed to create energy.
When the spacecraft needs more power, the antimatter will be released to collide with a target of matter, which releases energy, from the feed system.
Like a particle collider on Earth, along the magnetic nozzle, it will move the energy created by the matter-antimatter through a thruster.
A space probe would work by being struck by antihydrogen protons, a portion of the depleted uranium located on the coated foil inside the spacecraft is caused to fission.
Fission is the action of dividing/splitting something into two or more parts.
The reaction causes the creation of two “fission daughter” byproducts. These byproducts are typically emitted back-to-back with equal momentum.
While the two “daughters” may not be exactly atomically alike, for the known laws of physics to have adhered, their momentum inherently must be equal.
While one fission daughter heads into the direction of the spacecraft’s uranium-coated carbon sail, the other escapes into space. The first fission daughter is decelerated and absorbed which imparts its momentum into the sail.
The other daughter escapes in the form of conventional propellant exhaust. These opposing forces with their powerful kinetic energies, enable the spacecraft to reach such high speeds.
Positron Fuelled Rocket in the Past
Antimatter reactions produce blasts of high energy gamma rays. Gamma rays are not healthy to be around as they penetrate matter and break apart molecules in cells. By fragmenting atoms of the engine material, high-energy gamma rays can also make the engines radioactive.
Gamma rays are electromagnetic radiation of some kind that emerge from the radioactive decay of atomic nuclei.
This is where NIAC comes in to save the day. They are funding a team of researchers to work on a new design for an antimatter-powered spaceship that avoids this nasty side effect that produces gamma rays with much lower energy.
While previous designs of antimatter spaceships used antiprotons that produced high levels of gamma rays when annihilating, the new design will use positrons, anti-electrons, that will produce gamma rays with about 400 times less energy.
The researchers at NIAC are still figuring out whether this idea is feasible or not. If it is, funds are available to successfully develop this technology.
NIAC — NASA Institute of Advanced Research
Advantages of Antimatter Fueled Rocket
A positron powered spaceship would have some advantages over the existing plans for space missions, the most significant one being safety.
Current Reference Mission calls for a nuclear reactor to propel the spaceship to Mars. It is desirable because nuclear propulsion reduces travel time to Mars, which, in turn, increases safety for the crew by reducing their exposure to cosmic rays.
If we take a look at a chemically-powered spacecraft, it weighs much more and costs a lot more to launch.
Nuclear reactors are radioactive even after their fuel is used up. Due to its radioactivity, when the ship arrives at Mars, plans are to direct the reactor into an orbit that will not encounter our planet for at least a million years, after the residual radiation will be reduced to safe levels.
In a positron reactor, however, there is no leftover radiation after the fuel is used up, Because of this, according to the team, there is no safety concern if the spent positron reactor should accidentally re-enter Earth’s atmosphere.
An antimatter powered spaceship will also be safer to launch.
If a rocket carrying a nuclear reactor explodes, it could release radioactive particles into the atmosphere.
If the positron spacecraft were to explode, it would release a flash of gamma-rays, however, the gamma rays would be gone instantly. No radioactive particles would be able to drift on the wind, the flash would be restricted to a fairly small area and the danger zone would only be about a kilometre around the spacecraft.
The danger zone of an ordinary large chemically-powered rocket is about the same size, because of the big fireball that would result from its explosion.
The most significant advantage is speed. It would take 180 days for astronauts to reach Mars with the current Reference Mission spacecraft, however, with the help of antimatter, it would cut down the days to half the time, 45 days!
A challenge to making this kind of spaceship a reality is the cost required to produce the positrons. Due to its effect of annihilation when interacting with normal matter, there is not an abundance of antimatter just sitting around.
The cost to create the spaceships is also quite high. To produce 10 milligrams of positrons, we would need approximately 250 million dollars, using the technology we currently have.
Another challenge to also consider is the storage of the particles. To store a small number of positrons without them annihilating each other is quite difficult. It’s not like we can just store them a bottle and call it a day. They have to be contained with electric magnetic fields.
With the current research project’s progress, we may be able to overcome this challenge fairly quickly.
We have progressed so far ahead in the field of space technologies since the last century. Thinking about it, we had only been discovering anti properties of normal matter in the last decade. Who would have thought we would be on our way to develop a spacecraft fuelled with those same properties? We are incredibly close to developing a spaceship fuelled by antimatter; only a few decades away if all goes right. With antimatter fuelled engines, humans will travel to places in space where no one has ever been in. Antimatter fuel may just as well be the key to unravelling all the future space missions to the journey to infinity and beyond.
- We can travel at a speed of approximately 120,000 km/second, which is around 40% of the speed of light with the help of antimatter fuelled rockets.
- Antimatter is the same as normal matter in terms of mass and appearance, the only thing different is the different charges. When these two particles interact, they annihilate each other.
- Antimatter is created in nature in high energy collisions. On Earth, we do it with the help of a machine called Particle Accelerator.
- Very little fuel is needed for liftoff.
- There are three main components to the rocket; magnetic storage ring, feed system, and the magnetic rocket nozzle thruster.
- It has many advantages over the current rockets used.
About the Author
Hey readers! If you have made it this far, then I would like to thank you for your time! Hopefully, you learned something new from this article! I am super passionate about learning about new things, specifically more about space, astronomy and anything to do with space. If you want to read more articles from me follow me on Medium and connect with me on LinkedIn! If you’d like to be tuned in for my monthly updates, subscribe to my newsletter!