The term photon propulsion seems quite new but it was first introduced in 1960 to make photon propulsion rockets. A kind of rockets that uses the momentum of light particles to travel fast in space.
Photon propulsion theory
According to the third law of Newton, every action has an equal and opposite reaction or simply momentum is always conserved. That’s why when a bullet fired gun recoil in the opposite direction with some momentum.
Using this approach we can use powerful lights or electromagnetic radiation in the form of lasers to make interstellar travel. And since light has the highest velocity in the universe. Its particles ‘photons’ could be utilized to make interstellar travel possible with a very close speed of light.
But as we know photons are massless particles but they have momentum. It is because light also behaves like a wave when it propagates, and a wave has momentum inversely proportional to its wavelength.
But it is observed that the momentum of light particles is very little. Therefore we would need a huge amount of light to make this possible for reasonable use of this principle in real life.
This made scientists of that time think for a solution and they proposed an antimatter photon engine.
Antimatter photon engine
Now, this kind of photon engine uses antimatter to power spacecraft. Antimatter is nothing but the opposite of normal matter. When matter and animated are combined they produce a huge amount of energy and light. And if we could guide this light and energy in one direction then we could possibly make a photon engine.
But that’s a big if. Because it is not an easy task to create antimatter and even if we could create antimatter how would we store that? These questions make scientists think one more time. But what are the other possible ways then?
One other possible way suggests using electromagnetic radiation in the form of lasers. The idea was proposed and continued by Professor Lubin from UC Santa Barbara. And many scientists from the top universities and space research organizations including NASA are working on this project.
The project has named Directed Energy Propulsion for Interstellar Exploration or DEEP-IN. And the best this is that using this technique we may possibly make our first Photon propulsion rocket very soon. Let’s understand DEEP-IN in a bit of detail.
Laser photon propulsion, DEEP-IN
Laser photon propulsion would need a giant set of lasers to push spacecraft away in space. And this kind of photon engine which uses photon propulsion could reach the most speed of light so quickly and make interstellar travel reasonable.
Currently, we use a chemical reaction to produce thrust and push rockets forward. But the photon engine will run with the help of momentum transferred by the collision of the photon behind the spacecraft.
But as mentioned above that photons don’t have mass but has the fastest speed in the universe and also behaves like wave therefore paradoxically they have momentum.
And this where the laser will be used. Giant lasers present in the earth orbit will fire a powerful beam of photons on the spacecraft powered by sunlight or solar energy. And a beam of photons will collide at the reflective surface like a solar sail behind the spacecraft.
The beam will be able to push objects forward. This will happen by transferring momentum of trillion and trillion of photons colliding on its surface.
Over time momentum keep accumulating in the ship which increases its rate of change of velocity and spacecraft starts attaining high velocity.
This not just a theory and many solar sails have already been tested by NASA and some other space agencies. After observing the appealing results of photon propulsion, NASA has started investing in this space technology very before.
In this way, photon propulsion rockets can transfer 100 kg of payload to Mars in just three days. And a crewed ship will be able to reach Mars in a month.
Apart from this, the spacecraft will be able to reach about 30% speed of light. That will surely unlock new limits to humanity.
One of the biggest advantages of photon propulsion is that spacecraft would not need to carry fuel. That means more useful mass or payload can be sent using this technology.
And because the whole machine will be powered using solar energy and lasers. So we don’t need to waste or fire money on fuel. Of course, we would need to send a payload into earth’s orbit first using rockets.
But there are still many challenges to solve in order to see this space technology working. But what are the limitations stopping us to achieve this technology?
Challenges to photon propulsion!
Photon propulsion can send a small number of payloads on mars in 3 days or less. But there is a huge problem associated with the build a spacecraft of this kind.
The solar sail that will use on spacecraft needs to be 10000 meters square. For this idea to be worked properly. And the biggest challenge is to send this much amount of payload to space first.
Not only material for Solar Sail but many high tech equipment and other machinery are also need to be sent to earth’s orbit first. And if we could send this much payload into space then the problem comes with assembling all this stuff in space.
Also Read: SpaceX vs Blue Origin, Which one is better?
Also, spacecraft need to be super strong as it would be moving at one of the top speed in-universe.
Except for this, retardation is another problem. We know how to accelerate spacecraft but don’t know how to stop. Especially when spacecraft is traveling at 30% speed of light. That’s why it’s still a challenge.
It does not mean that this technology is impossible but we need to refine and discover some better and more efficient ways to perform these initial tasks. Science has the answer for everything but the thing required is continuous efforts, patience, and time.
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