Using 0 Fuel to Travel Through space?! —An Intro to Solar Sails ⛵
What comes to mind when someone asks you how do rockets work?
Probably something like combustion chambers, chemical rockets (using them as an example), and other similar things.
Although currently, these chemical rockets that have been the leading system in space exploration aren’t as efficient as we thought so.
Let me explain.
Why chemical rockets aren’t efficient.
Rockets currently aren’t as efficient because there have been other methods of propulsion for space that have been proposed.
Some of these include antimatter propulsion, nuclear propulsion, and solar sails.
Currently, rockets lose a lot of their fuel just to get into space. For example, the Artemis SLS rocket NASA is developing is estimated to weigh about 6 million pounds and 5.4 million of which is just fuel.
In other words, around 87 % of the rocket’s mass is just fuel which is absolutely crazy!
Most of this fuel will be combusted trying to escape Earth’s atmosphere and then we only need a little bit for the rest of the journey because the moon’s orbit will be used for the return.
Ok, now what? We’ve seen that current chemical rockets won’t cut it for longer space missions and traveling outside this solar system so why continue?
Well, the main reason we’re continuing to use chemical rockets is that we don’t have the resources or budget for more ambitious projects such as antimatter propulsion. Currently, it’s estimated that making 10 milligrams of positrons (the opposite particle of electrons in the antimatter spectrum) would cost about 250 million dollars 🤑, we don’t have enough money to fund such an expensive project that has chances to fail.
So going back, what do we do now? Well, I’ve mentioned solar sails in the title, well these solar sails could be a good chance to explore more of space for short-term goals.
What are solar sails?
Solar sails are as the name suggests huge sails in space that travel using sunlight? Sounds crazy right?!
The fundamentals of solar sails are actually simpler to understand compared to something such as antimatter/nuclear propulsion.
Essentially solar sails work by using photons from sunlight that bounce off of a reflective material; currently, most solar sails for prototyping and smaller-scale missions are made out of a reflective sheet of mylar (a space-rated material).
This diagram explains how solar sails propel, the light source in this case is our sun.
The photons that come from the sunrays come into contact with the solar sail material (let’s use mylar in this case). Once the photons hit the mylar reflective sheet, they bounce pack giving the solar sail a very tiny push that allows the sail to propel forward in space.
This is shown as the reaction momentum and reaction force in the diagram.
What if we want the solar sail to go in a different trajectory? Is that even possible? Well of course it is! The way we approach this problem is we orient the sail in a certain direction so the photons bounce in another direction making the outcome as the solar sail travels in a different direction.
This exact scenario is explained by this diagram here :
Let’s slow down for a second. Tiny pushes and that’s how the solar sail propels. Sounds pretty lame. Although that’s not the case at all, the constant exposure to the sun rays enables the solar sail to constantly have these tiny pushes which propels the solar sail at very high speeds.
Think of solar sails as like a little kid on a swing and their parents being the light source giving them a push every now and then until they feel like they’re flying 🛫.
Since solar sails also don’t use any fuel other than the launch vehicle (which I’ll about later in the article), they are often thought of as “slow” in space propulsion systems. Although this isn’t quite the case… it’s predicted that a well-developed solar sail could enable even interstellar travel!
A solar sail project known as light sail 2 showcases the ability of solar sails to travel at greater speeds. The light sail 2 is a 32-square-meter sail and that accelerated at just about 0.058 mm/s².
In just 1 month of constant sunlight, the speed increased by 549 kilometers per hour which is absolutely insane and this was just a small testing project regarding solar sails 🤯.
So why use solar sails?
Here’s a quick overview of why solar sails might be a better bet to travel in space in the next 5–10 years rather than chemical rockets :
- Higher acceleration
- Cheaper (to an extent)
First, let’s talk about higher acceleration.
Due to the constant sunlight exposure to the solar sail for a long duration of time, the solar sail will start to only gain speed which is such an amazing factor.
Chemical rockets will use most of their fuel to escape Earth’s atmosphere and then would just use the speed gained by their additional fuel to gain some speed and maintain that while solar sails can constantly gain speed as long as there is exposure to sunlight.
Launching solar sails is also usually cheaper than chemical rockets. Depending on the size of the solar sail the cost can also vary. If it was a small sail, then it would weigh less, meaning less payload cost and less fuel required, thus a smaller rocket. If it was a bigger solar sail, then a larger rocket required, thus more fuel, thus greater the cost. You probably get the general idea by now.
There’s this 3 step process a solar sail follows to get into space.
Step 1 : The launch vehicle.
Your solar sail will be launched into space using some sort of rocket, like mentioned above, depending on the size, the launch vehicle will vary.
Step 2 : Payload launch.
Once all of the stages have been depleted, the payload will be released (in this case the solar sail). Usually using some sort of rotor system, the solar sail will unravel in a few minutes.
Step 3 : Begin acceleration.
Once the sail comes in contact with sunlight it will start propelling slowly but gain more traction as time passes.
An alternative approach.
An alternative approach that has been proposed to solar sail technology is actually using powerful enough lasers to propel the spacecraft forward in the early stages of launch when it’s slow.
The current problem with this approach is we don’t have lasers of that capability and the cost for the project would also be increased, while smaller laser tech production is cheaper, we’re talking more alongside HUGE laser beams ⚡.
IKAROS
IKAROS is a great first step to demonstrating the potential for solar sail technology.
IKAROS is a solar sail project launched by JAXA (Japan Aerospace Exploration Agency). This project was a demonstration regarding solar sails in space and it showed that while there is still work to be done for solar sails, they have some potential.
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A little bit about me :
I’m Siddhant, a 13-year-old who is passionate about Space Tech and other emerging technologies. Currently, I’m looking into rocket propulsion systems and how they can impact space exploration! Consider using the links below to connect with me :
