Eliminating space debris with ion beams
A dive into the space debris problem + Ion Beam Shepherd as a solution.
Out in outer space, we have a lot of junk. The Low Earth Orbit (LEO) is littered with dead satellites, used rocket stages, and even particles from the collision of other debris.
Currently, there are 4, 500+ satellites orbiting earth; and 14, 000 old rocket parts/ pure crap (2018 South China Morning Post).
It’s dangerous too.
Space debris poses a threat to the current and future safety of satellites… which risks the quality and ability to retrieve satellite imaging for data. Look: In 2018, a $162-million US worth satellite, CryoSat-2 faced the threat of a collision (Nature). This is important in 2 parts:
1. Economic investment. A 162 million project would be thrown out the window if the satellite had crashed. Meaning, that the project was a waste of money~ and the economic risk to launch satellites would be higher…jeopardizing our willingness to pursue future launches or any type of exploration.
2. Quality of satellite imaging. CryoSat-2 specifically monitors the ice on Earth. Debris would compromise our ability to get important data to understand our Earth better.
Satellite data provides is with crucial information, especially within agricultural, and environmental industries. The graph on the left (GLERL) represents the changes in ice-coverage on the Great Lakes. We can use this data to determine climate patterns, monitor lake water levels, water temperature structure, and water movement patterns.
The more crowded, and dangerous our orbit becomes, the harder it would get long-term sustained datasets.
One more thing: debris would threaten our abilities to develop multi-planetary systems and any type of exploration. Sorry, Elon Musk and your dreams to go to Mars.
How dangerous could space debris really be? *skepticism*
Short answer: Extremely.
Debris moves at high speeds (17, 500 mph): The energy of a collision is based on the speed of the two objects colliding, rather than size. Making it possible for a paint flake/small metal fragment to create a 7mm-wide dent impact in one of the windows of the International Space Station (ISS)’s cupola.
Sidenote: The Cupola is strong…its windows are 80cm thick, made up of fused silica, and borosilicate glass.
A piece of small debris really did that:
Even bigger debris (larger than 10cm) would utterly shatter a satellite/ spacecraft into smaller pieces (The Guardian).
To put into context of the absurd strength obtained by debris…
Being hit by a ‘sugar-cube’ of space debris is the equivalent of standing next to an exploding hand-grenade. -Stuart Clark
Currently, we avoid collisions by performing avoidance maneuvers. However, the number of debris only increases each year, increasing the cases in which we perform avoidance maneuvers… a reactive system is time-taxing, ineffective, and a short-term band-aid solution. A reactive solution isn’t going to cut it anymore.
Our space junk problem??
It’s not looking too great. There are fruit flies buzzing around the trash, and it’s starting to stink.
Let’s take out the trash.
Ok, but…No one really wants to. The incentives to launch satellites and spacecraft is much stronger than deorbiting junk. The economic benefits that you get from launching a satellite are far more visible than taking one down.
It’s all within everyone’s benefit to establish a sustainable space industry. In cases where companies acknowledge the importance of removing space junk, removal systems are simply, just too expensive.
Take Iridium, a satellite company (responsible for 66 active satellites) for example:
Desch, the CEO of Iridium said he would pay for an active-debris-removal venture to deorbit its dead satellites… the twist is… “for a low enough cost.” He’s quantifying “low” as $10K per orbit. 10K is far from the reality of how much a debris-removal company is willing to operate. (Space News)
Incentivization is one part of the problems we have to tackle. But let’s ignore that for a sec, and look at the science.
How are we going to do this? -The approach.
Somebody: Just launch fewer satellites/spacecraft in the first place.
Two things wrong with this…
- Space debris accumulates regardless if we launch more satellites, due to atmospheric drag decay of current spacecrafts. According to a study by Liou and Johnson.
- Satellites provide us with essential useful data and telecommunication services. Each day, we are becoming more and more reliant on its technologies. The growth of satellite launches makes sense.
Currently, debris accumulates because we launch space crafts… and naturally existing spacecrafts in orbit breakdown into smaller pieces.
We can’t really remove anything from the equation. But, we can add something to the equation.
Again… How are we going to do this?
Ion beams could be our answer.
Active Debris Removal (ADR for short) methods can be categorized into:
- Contact-based methods
Contact methods require debris to be docked… and that debris is uncooperative, moving chaotically. To overcome that hurdle brings up a multitude of technical problems.
Imagine trying to shoot a net to capture a wildly flying school bus. Pretty hard, right?
The Ion Beam Shepherd reduces the technical complexities, cost, and risk that you get with contact methods.
Tell me more…
One type of contactless method: Ion Beam Shepherd
The IBS is a generic spacecraft body that would eject ions to deorbit debris. The ion beams provide enough force on the target to move it out of orbit. All this happens through the magic of an ion beam thruster.
Ion Beam Thrusters- how do they work
A hot-cathode will shoot electrons (green dots)into the ionization chamber. While a propellant (purple) enters the chamber.
The electrons that are shot from the cathode are attracted to the positive grid…so it will travel in that direction.
However, on its way… the electron collides with the propellant atoms. As a result, the electron knocks loose the propellant atom’s electrons… making the propellant atom: cations.
As atoms pass through the positive grid, they are attracted to the negative grid. This attraction allows the ions to move in high velocities out of the thruster.
Another thing… the cations must be neutralized when it leaves the ship, otherwise, it would be attracted towards the ship- making any thrust ineffective.
We neutralize the cations by ejecting electrons through a cathode attached outside of the ship.
It looks like this (sci-fi vibes):
The IBS uses two ion beam thrusters to propel debris out of orbit. The primary force will deorbit debris. The second force is to compensate for the first force, so the shepherd doesn’t act as a rocket.
Currently, the Ion Beam Shepherd is a concept and hasn’t been tested to understand its feasibility. The technology faces practical issues, such as minimizing pointing errors.
So what now?
Most research papers about the IBS are from 2010–2012. The project has been held on hold, because of funding. Implementing an active debris operation system has many legislation and political difficulties.
Who provides the license for debris removing satellites? This is a question of international affairs. In January 2018, China published a paper. The paper pitched a solution for the debris problem: space-based lasers. However, some were skeptical about China’s intention.
If China has the ability to deorbit any satellite… will it use it to develop a sustainable space industry, or militarize space? (South China Post)
How can we perfect this technology? … But also make it economically realistic for private companies like Iridium/ SpaceX to use it? These are imminent questions that are becoming more and more urgent to answer.
SpaceX’s project, Starlink plans 60 satellites, as often as every three weeks in 2020. If successful, they will employ 42, 000 satellites!
So many satellites for what?
- high-speed internet from space to everywhere on earth
The only way that we can establish a sustainable space industry, and maintain our reliance/ launches of satellites… is to develop an active debris removal operation.
Let’s find a way to take out the trash.
A special thanks to Matteo Cappella for joining a call to answer some of my questions, and his kind guidance.
Other special thanks to Claudio Bombardelli, for his prompt email reply to my questions about his research paper.
If you have any questions or want to talk about the content… You can reach me through Linkedin.