Although this expression may be familiar to many, it is very possible that this frontier will soon - figuratively speaking - be sensed by humanity as a barrier made up of a pile of space debris.
In the coming years, various satellite constellations for communication purposes will be continuously built and expanded, and although they use low Earth orbits (LEO), where the braking effect of the upper atmosphere causes all space objects or space debris to eventually disintegrate when entering the denser atmosphere without continuous orbit raising, this self-cleaning process can take many years or even decades depending on the orbit altitude.
Thus, if, for example, a cascade reaction starting from a collision of satellites would destroy several dozen or even several hundred satellites, the tens of millions of new space debris would practically make it impossible to safely use low Earth orbits, the only place where the harsh conditions of space weather are made a little more livable by the Earth’s magnetic shield. Due to the high-energy ionizing radiation of the Van Allen belt, even medium Earth orbit (MEO) is dangerous for space activities.
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| International Space Station (Credit: NASA) |
Although in recent years numerous solutions have been developed for towing uncontrollable satellites to lower orbits, enabling their rapid disintegration in the atmosphere, if a collision of satellites has already occurred, there is currently no good solution for quickly collecting the thousands of smaller and larger pieces of space debris and preventing further satellite disasters.
This is not surprising, as while it is relatively easy to capture an undamaged satellite that is drifting only due to a technical failure or, for example, lack of propellant, especially if the satellite is equipped with the magnetic docking technology developed specifically for this purpose by the Japanese space industry company Astroscale, a few centimeter piece of space debris traveling at a speed of about 27,000 km/h and rotating hectically along all three axes is far from it.
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| Astroscale Docking Plate (Credit: Astroscale) |
Obviously, if NASA, ESA and JAXA had unlimited financial resources, the space agencies could afford to launch several dozen catcher satellites equipped with robotic arms and metal nets specifically to prepare for such disaster situations. However, due to the tight budgets of the space agencies, this will never be a real possibility.
From a financial point of view, the only realistic solution is for civil space industry companies like SpaceX and OneWeb to handle the space debris they can cause, making it part of the conditions for issuing licenses for satellite constellations. In this case, new perspectives could open up, for example, every communication satellite to be launched into low Earth orbit in the future could be prepared for the possible collection of space debris.
Currently, these satellites use gyroscopes for orientation and xenon or possibly krypton in their ion engines for orbit changes. However, in 2021, the French space industry company ThrustMe successfully tested the use of iodine as a propellant. Its significance is that unlike noble gases, iodine can be stored on the satellite in solid form and only heated to gas state just before starting the ion engine.
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| ThrustMe NPT30 iodine plume (Credit: ThrustMe) |
Another significant research and development effort is related to the Mitsubishi Electronic Research Laboratory (MERL), the ability to manufacture satellite antennas in space using 3D printing. This allows the use of a special light-sensitive resin material to significantly save on launch costs by creating one of the key elements of their communication system, their dish-shaped antenna, only in Earth orbit.
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| 3D printing in Earth orbit (Artist's Concept) (Credit: Mitsubishi Electric Research Laboratories) |
By combining the two research and development programs, the solid-state storable ion engine propellant and the 3D printing of large structures in space, a research and development program aimed at managing space debris could be launched with the aim of developing a dual-use material that could be used in space both as an ion engine propellant and as a 3D printing material for building structures.
In case of its success, in the future every communication satellite orbiting in low Earth orbit could have limited ability to capture space debris, as in an emergency they could create lattice structures or even completely closed structures at the expense of their fuel reserves, with which they could capture selected pieces of space debris and, if necessary, even tow them to lower Earth orbit.
These structures, unlike parabolic antennas created by 3D printing, would not be built from a single piece, but like the petals of a flower, they would be foldable. Thus, the structure used for capture would already surround the piece of space debris before contact with it, preventing it from breaking away from the catcher satellite on an unpredictable trajectory due to its collision with the structure - no matter how minimal its force due to the coordinated speed of the objects - or from creating a new debris cloud by breaking into several pieces as a result of the collision.
Since in the future a total of several tens of thousands of communication satellites could belong to low Earth orbit satellite constellations such as Starlink and similar ones, if most such satellites were required to have space debris capture capability as well, there would be an opportunity to respond in the event of any significant debris-causing satellite disaster.
Obviously, a dual-use ion engine propellant suitable for 3D printing could be much less efficient than the currently widespread xenon. In addition, satellites prepared to handle space debris problems would have to have multiple times the amount of propellant compared to the current ones in order to have enough propellant to create structures that can be used for capture in case of an emergency, not to mention the extra weight of the 3D print head and other special accessories. As a result, the construction costs of satellite constellations could increase significantly in the future.
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| Millions of space debris and micrometeorites around Earth (Artist's Concept) (Credit: NASA) |
At the same time, it is unlikely that while there are already tens of millions of pieces of space debris around the Earth today, and the International Space Station has to slalom on its orbit due to regular collision risks, then with tens of thousands of satellites specifically developed for cheap mass production, the risk of the Kessler syndrome would be negligible, which would automatically bankrupt companies like SpaceX in the event of its occurrence. Thus, preparing for disaster situations is also in the interest of civil space companies.
(I wrote this concept for an article for the Future Factory website, where it was published in Hungarian on April 21, 2023. The English translation for this blog was made with ChatGPT, so apologies for any possible grammatical errors.)