3 Advanced Propulsion Methods to Travel in Interstellar Space š!
Understanding rocket propulsion methods that might enable us to travel interstellar.
Whenever I was a little kid I would always think that airplanes are rockets and how I was so lucky to see one every day. Of course, theyāre airplanes although that got me to think about how we donāt see occasional rocket launches. Of course until recently with SpaceX. Even if we do rockets arenāt efficient.
These rockets that we have currently donāt have the ability to take us to other solar systems in a personās lifetime. In fact, thereās a huge disconnect.
Currently, it would take a chemical rocket 30 000 years to reach our closest star which is Proxima Centauri. This star is 38 000 000 000 000 km away from Earth.
Lucky for us that the closest planet to Proxima Centauri is possibly a habitable exoplanet known as Proxima B. Unfortunately for us, thereās no point in trying to reach there right now with our current technology. We need to figure out a way to travel to exoplanets to help spread out our growth because Earth will face many devastating struggles.
In fact, say the astronauts we launch are 40 years old and they live up to 100 years old, they will only be able to survive up to 0.0000000000015789474% of the trip. Yup, thatās right, we have no chance of ever reaching Proxima B with current chemical propulsion systems.
Although now what? What do we do now? Well, there have been some other rocket propulsion methods that have been proposed to make us travel through interstellar space at very high velocities, and thatās what Iām here to talk about!
Quick Breakdown š
Across this article Iāll cover 3 different topics :
- Antimatter Propulsion
- Nuclear Propulsion
- Ion Propulsion
Without any further to do letās dive into the first propulsion concept; Antimatter propulsion!
What is Antimatter Propulsionš®?
Antimatter propulsion is probably the definition of moonshot thinking. Itās a super-ambitious approach to travel interstellar.
Antimatter propulsion uses the energy created from the reaction when matter and antimatter are annihilated (This will be explained later).
First of all, what even is antimatter? Antimatter is as the name suggests the opposite of matter. Antimatter has different anti-particles which bind together to create antimatter. These anti-particles are made of positrons (the opposite of electrons), antiprotons (opposite of protons), antineutrons (opposite of neutrons), etc. The major difference in antimatter and matter is the electrical charge of the particle, for example, positrons have a positive charge while electrons contain a negative charge.
Using antimatter and matter we can annihilate them (sounds brutal š) although not so much, the result is like magic! When matter and antimatter come into contact they basically cancel each other out due to the same properties such as spin, mass (just electrical charges are different for counterparts). The end product of this annihilation is just pure energy that can be harnessed to create thrust.
The picture below describes 2 processes. pair production and pair annihilation. Annihilation is described with photo (a) and how annihilation works was mentioned previously.
Letās look at what pair production is. When an incident photon (which has a certain light frequency), this photon once coming into contact with a nucleus has the possibility to create a positron and an electron at once, pair production is an essential component of understanding antimatter (there will be more information regarding pair production soon) (Pair production is mentioned on photo (b)
This discovery of āmodern-dayā antimatter was first theorized in 1928 by Paul Dirac who is a famous physicist. When Dirac solved an equation about the relativistic mechanics of the energy of a particle he came out with 2 results, negative and positive. He then theorized if this was a whole different class of particles. This theory was later backed up by Carl D. Anderson in 1932 when he saw that the curvature of a high-energy particle traveling through a cloud chamber was in the opposite direction.
Now that weāve covered the basics of antimatter we can start to look at the propulsion aspect.
As mentioned previously, antimatter propulsion uses the energy created from the annihilation and gets directed in a way to create propulsion. Of course, there hasnāt been an antimatter rocket created and launched into space although this is how fundamentally it would work. Now let me talk about some of the problems that are holding antimatter rockets from being launched sooner.
How is antimatter artificially created?
Antimatter isnāt around us to harness it to create propulsion. If it was then due to annihilation there wouldnāt be the same amount of life. What now? To make antimatter propulsion possible there is a way to create antimatter artificially!
Antimatter is artificially created by using pair production. A photon comes into contact with a nucleus and then creates antimatter. Essentially this is why pair production is so important because this is how we create very small amounts of antimatter currently.
At CERN they use an antiproton decelerator to slow down the antiprotons to effectively trap and store them.
Currently, this process is very expensive and energy demanding. Read the next section for more info on this ā¬ļø.
Whatās holding us back? š
In this section, Iāll talk about the 3 major things that are keeping antimatter propulsion from becoming a reality sooner.
- Price + Energy (Production)
- Trapping Antimatter
- Directing
First of all the price + energy demands to create antimatter is way TOO much for it to be a financially feasible project. It currently takes $62.5 trillion to make 1 gram of antimatter! Thatās absolutely crazy, we canāt find antimatter because if there was antimatter around us then theoretically there would be no life due to annihilation. It also takes huge amounts of energy to artificially create antimatter due to the specific process needed. For these reasons artificially creating antimatter is not feasible due to the high demand for money values and energy usage.
The next major factor thatās holding us back from developing antimatter propulsion systems is trapping the antimatter. We canāt necessarily trap the antimatter because the rocket is made up of matter and this would cause annihilation to occur literally deconstructing the rocket into pure energy. A company known as positron dynamics (coming up in the next section) is working on solving the technical barriers to antimatter propulsion.
Finally, another major factor that is stopping us from developing an antimatter propulsion system is directing the energy created through annihilation. This energy released is high energy-dense radiation which is extremely hard to control meaning that directing the rocket to approach the rocketās trajectory will also be an issue.
A company to watch in the next 10ā20 years ā Positron Dynamics! š
Positron Dynamics is an emerging company that is working on some amazing things in the field of antimatter propulsion. Their mission is to help bring antimatter propulsion to life to go visit exoplanets and to develop civilizations outside of our solar system. In short, theyāre trying to push the boundaries of space exploration using antimatter rockets.
This company is definitely one to watch in the next 10ā20 years with more and more research being poured into this field of rocket propulsion. Check out their website here and hereās a talk given by the founder of the company :
Nuclear Propulsion š§Ø
Now that weāve covered the concept of antimatter propulsion; how it works, what is antimatter, whatās holding us back from developing an antimatter rocket, and Positron Dynamics, itās time for us to look at nuclear propulsion and how it works!
Nuclear energy was recognized very early on in the development of space tech because of the high energy densities of fission and fusion. Some researchers even put these concepts into books before we knew a lot about these concepts. A lot of work was put into nuclear propulsion during WW II although efforts were still being made during the Space Race period.
In the upcoming sections, Iāll talk about how nuclear fission and fusion propulsion work, whatās holding us back from implementing this rocket propulsion method, and some projects regarding nuclear propulsionā¬ļø!
How does nuclear fission propulsion work ā¢ļø?
Nuclear fission reactions produce approximately 10ā· times larger amounts of energy than energetic chemical reactions. There are 3 general approaches to nuclear fission propulsion. These include fission reactors, fission pulse, and direct use of fragments from the fission reaction that was generated.
The reactor approach works by the energy from a fission reaction to heat up a propellant like in chemical rockets which would expand and create thrust. This approach is similar to chemical rockets although there is just a fission reaction involved. Typical specific impulse/Isp (how efficient the rocker engine is at producing thrust) would be between 8 km/s and 70 km/s for this type of rocket. Another limiting factor of this design is the amount of heat created so the materials used are very limited and some are not space-rated materials.
To achieve larger isp levels we need to eliminate the need for a reactor and use actual fission products created from the reaction such as in the Orion project (Iāll talk about that later)š.
How does nuclear fusion propulsion work?
There are 2 main techniques to sustain a fusion propulsion system; inertial confinement fusion (ICF) & magnetic confinement fusion (MCF). Using either of these 2 fusion techniques would result in a very different rocket design. Further in this section, Iāll discuss 2 concepts for both an ICF rocket engine design and an MCF one.
ICF ā¬ļø
The way ICF propulsion works is by utilizing a fusion fuel pellet which is being compressed through high-power lasers or particle beams. The pellet is then heated because of the compression and the constant energy the lasers emit on the pellet. The pelletās inertia would be sufficient enough to confine the energy being released to have a useful fusion reaction. Above is a concept for an ICF propulsion engine ā¬ļø.
MCF ā¬ļø
In contrast to ICF propulsion, an MCF reactor would instead confine fusion plasma using magnetic fields. This is possible because the fusion plasma contains ions and electrons which are possible to confine using Lorentz forces (force exerted by magnetic fields). This is a very simple explanation of MCF reactors for propulsion although refer to the note below ā¬ļøalongside look at the picture above for an MCF reactor concept for rocketsā¬ļø.
*Note : Stay tuned on my medium for a future article I write regarding nuclear propulsion at a much deeper level*
ICAN (Antiproton-Catalyzed Microssion/fusion Propulsion) š
Now that weāve looked at both nuclear and antimatter propulsion, what if I told you there is a way to combine both of the propulsion systems into one! Well introducing (as the subheading suggestsā¦) ICANš„³!
The way ICAN or Antiproton-Catalyzed Microssion/fusion Propulsion works is a pellet that consists of uranium fission fuel and deuterium-tritium fusion fuel. This pellet is then compressed using ion beams, lasers, etc. When this compression process is at its peak, a few antiprotons are released to catalyze the fission process.
Due to the antiprotons, the number of neutrons per fission increased to about 16 from 2ā3 before the pellet was bombarded with the antiprotons. This fission reaction causes a high-energy fusion reaction to heat up a propellant which would then produce thrust. The amount of Isp or Specific Impulse would be HUGE for this kind of rocket and if developed has huge potential in the rocket propulsion industry š!
Some nuclear propulsion projects/proposals ā¬ļø
In this section, Iāll talk more about 2 different projects/proposals for nuclear propulsion and what happened to them/what progress was made!
The 2 projects Iāll be talking about are :
- Orion
- Daedalus
Project Orion š
Project Orion was a study that was conducted by the United States Air Force, NASA, and DARPA to see if nuclear propulsion was effective or not. The method that was being studied here was nuclear pulse propulsion which literally uses explosives to create thrust, thatās mindblowingš¤Æ (pun intended)!
The way the Orion rocket was supposed to work was these explosives would be dropped from a distance away from the vehicle in which a pusher plate would help absorb shocks as well.
These were directional explosives that would be used to help create thrust to the rocket while using that pusher plate mentioned previously to help absorb shocks created from the blast to mitigate damage to the rocket.
The reason project Orion wasnāt completed was primarily because of the international treaties regarding nuclear explosives and also the ban against storing them in space anyway. Because of this huge limitation, Orion couldnāt be completed.
Soon after in my opinion the scientists working on the rocket would realize that the amount of resources + moonshot thinkingš required just wasnāt there at that time.
Project Daedalus š
Another nuclear propulsion project I wanted to touch on was project Daedalus. Project Daedalus was a study conducted by the Britsh Interplanetary Society between 1973 to 1978. It was supposed to explore possibilities of interstellar travel using futuristic technological methods. The initial goal of this project was to travel to Bernardās star in a humans life time.
The way this rocket was intended to work was by using a fusion propulsion concept as mentioned previously and would be a 2 stage rocket proving huge amounts of thrust.
Ion Propulsion āļø
The final method of propulsion I wanted to talk about was ion propulsion! While ion propulsion yields usually a lower isp than antimatter and nuclear propulsion, itās a propulsion system thatās being researched into today. It still provides high levels of Isp and efficiencies as well.
The way ion propulsion works is by adding or removing electrons from propellants to produce ions which would be used as thrust. More specifically using a technique known as electron bombardment which makes a electron (which is negatively charged) collide with a neutral propellant atom resulting in positive ions ā.
Usually the most common type of propellant used in ion thrusters is xenon which can easily be ionized which increases efficiency in the thruster. Usually electrons in ion thrusters are generated using a discharge hollow cathode which is method for electrical conduction at a lower voltage.
Simplified, through a series of further operations the positively charged ions are pushed through the actual ion thruster to produce thrust.
NEXT (NASA Evolutionary Xenon Thruster) Ion Thruster āØ
NASA Evolutionary Xenon Thruster or NEXT is an ion thruster that is paving the way for more and more research into the field of ion thrusters and improving their efficiency! NEXT is 3 times more powerful than NSTAR which was a previous ion thruster launched by NASA!
Thank you so much for taking the time to read my article and I hope you learned something new regarding rocket propulsion! If you did feel free to clap š it and share šØāš©āš¦āš¦ it with others who might benefit from it!
Hi, Iām Siddhant š, a 13yo who is currently researching about rocket propulsion and going deep into the field of Space Techš! Some other things Iām SUPER passionate about are alternative energies, gene editing, and how genetics correlates with space exploration! I love writing, going outside/admiring nature, etc.
If youād like to connect hereās my Linkedin, my Medium if youād like to follow for future articles on Space Tech, and here is the subscription link to my monthly newsletter where I talk about my growth, lessons Iāve learned, and how everything is in general!
Peace out š,
Siddhant
