NASA's upcoming Artemis I mission to the Moon will see the space agency attempt another new feat in the field of space exploration: Sending a small probe to chase down and visit a tiny asteroid.
The target of this mission is 2020 GE, a near-Earth asteroid (NEA) less than 18 meters in diameter. For comparison, that's about twice the length of an average double-decker bus in London, which measures 8.38 meters.
This small asteroid is no threat to Earth and based on calculations by NASA's Jet Propulsion Laboratory (JPL), it won't be impacting the planet in the near future. Of course, even if it did impact, the damage would be, at best, minimum.
For comparison, the last known significant asteroid impact was on February 15, 2013, when an asteroid exploded in the air above Chelyabinsk, Russia. This asteroid was 17-20 meters wide, and while it didn't result in any casualties, although it did the shock wave from the explosion shattered windows in six different Russian cities and caused 1,600 people to require medical attention.
How will NASA go about chasing after this small asteroid?
The Near-Earth Asteroid Scout (NEA Scout) is a shoebox-sized probe propelled by a solar sail harnessing solar radiation. It comes equipped with a camera with a resolution of fewer than 10 centimeters per pixel, which it will use to get a close look at this asteroid.
It is set to be launched as one of the 10 secondary payloads aboard the Space Launch System (SLS) rocket that will be sent to space around March 2022 in the Artemis I mission, alongside the Orion spacecraft.
And this is significant, too, because while space probes have come close and even landed on asteroids before, they were always much bigger, at least 100 meters in diameter. One this small has never been studied up close before.
Why does NASA want to study this asteroid?
Simply put, to learn more so we can be prepared for any further damage. This is because, despite not being the size of some massive cataclysmic-level asteroids, these smaller objects can still pose serious damage.
“Although large asteroids are of most concern from a planetary defense perspective, objects like 2020 GE are far more common and can pose a hazard to our planet, despite their smaller size,” the mission's principal science investigator Julie Castillo-Rogez said in a statement.
Thanks to the asteroid that struck the Earth over Chelyabinsk in 2013, we know how much damage such an impact could do. And 2020 GE isn't just similar to the Chelyabinsk asteroid in size – they are also thought to be the same class of asteroid.
Further, according to Castillo-Rogez, this type of asteroid is one we don't know much about.
What is NASA trying to find out about it?
The answer to that is composition. Is the asteroid solid like a bolder or is it essentially just a conglomeration of rocks, dust and other minerals that were drawn together, like other asteroids such as the massive Bennu.
But sending the NEA Scout on its intrepid mission serves other purposes as well.
It will act as a scout for future missions, whether that be by humans or robots, that could potentially exploit these objects for resources. Asteroids can be rich in different minerals ranging from iron, nickel, platinum, iridium and more. And unlike mining on Earth, asteroid mining can be a more environmentally-friendly option.
But the NEA Scout will also serve as a means of scientific and technological demonstration.
“The genesis of this project was a question: Can we really use a tiny spacecraft to do deep-space missions and produce useful science at a low cost?” said Les Johnson, the mission’s principal technology investigator at Marshall Space Flight Center in Huntsville, Alabama.
The big problem is propulsion, as in the CubeSat, there is simply not enough room for large propulsion systems and the fuel they need.
To fix this problem, the NEA Scout needs a different means of propulsion.
Enter the solar sail.
Unfurling to be around 86 square meters in size, this sail is made out of plastic-coated aluminum and is thinner than a human hair. It's lightweight and has mirror-like qualities, and it will be the primary means of propulsion for the NEA Scout.
How does it work?
Essentially, it is pushed by quantum particles of light from the Sun, specifically the solar photons. While light does not have mass, it does have momentum. In fact, it is a constant force. As such, it can essentially push on the sail to give it speed in the same manner the sail on a boat uses the wind.
This parallel goes further, as just like the sail on a boat, adjusting the solar sail can adjust the NEA Scout's speed and trajectory.
How fast will the solar sail propel the NEA Scout? According to NASA, it can be several miles per second.
The NEA Scout will make its close approach to 2020 GE in September 2023, when it is set to catch up with the asteroid during its approach to Earth.
This demonstration is important, as it will be an effective demonstration of solar sail capability. NASA plans to take this technology further.
In mid-2022, the agency is set to launch the Advanced Composite Solar Sail System (ACS3), a novel approach in deploying solar sails from a CubeSat.
In 2025, NASA is set to launch an even bigger demonstration of solar sail technology, the nearly 1,700 square-meter Solar Cruiser.
But, NASA isn't alone in studying this.
The idea of a solar sail is similar in concept to the light sails that are the goal of Breakthrough Starshot, a project from the Breakthrough Initiatives, a program founded by Russian-Israeli billionaire Yuri Milner. Their light sail technology is a bit different, but it ultimately plans to use light propulsion rather than rockets for faster ravel that could, in theory, see space crafts go at speeds of around 161 million kilometers per hour, a significant fraction of the speed of light.
If one were to use this to send a spacecraft to Alpha Centauri, the closest star system to our own located just 4.37 light-years away, the trip could take just over 20 years.
As such, the solar sail demonstration is an important and significant step forward in seeing the viability of these types of light-based propulsion systems to help expand humanity's horizons further in the cosmos.