Space Debris | Space junk removal around Earth

Space Debris

Earth Actual Look From The Space

  This is the actual look of the planet Earth from the Space. The junk you see around is called Space Debris. Since the beginning of spaceflight, over 9,000 satellites have been launched into orbit. But with the speed of launches increasing exponentially, space is close to get much busier. In addition to every satellite currently in Earth’s orbit, there is around 100,000 tonnes of debris, most of which is too small for us to track. But what proportion damage can a small object really do to a spacecraft? And how do we shield the ISS from such dangers?

   In this article, we’re going to look at the powerful physics behind space impacts. We’re also going to look at the different methods used to shield the ISS and how we put them to the test here on Earth. Out of all the objects hurtling around Earth, only those larger than a baseball are often tracked. If a spacecraft is on a path to collide with a piece of debris, it performs a maneuver to avoid being completely destroyed. But for the many tiny objects that can’t be tracked, a collision could still be catastrophic.

   A raindrop weighing 0.2 grams will fall on your head with about 0.8 millijoules of energy. But an equivalent raindrop flying around as space debris would have over 1,000,000 times more energy, albeit its speed is merely 1000 times faster. The reason that velocity makes such a difference here is because in the formula for kinetic energy, mass is directly proportional but the velocity is squared. This is obviously nothing new to scientists. But when operating within the vacuum of space, these tiny impacts are unavoidable. Even things like flecks of paint have led to visible impacts on the windows of the Space Shuttle.

    Micrometeoroids coming from outside of Earth’s orbit can be moving at even greater velocities like 20 kilometres a second. Since the ISS is that the size of a whole football feild , it's constantly within the firing line of debris.

On-Board img. of damage ISS

whole caused by debris

While on-board the space station, astronaut Chris Hadfield took this photo of one of the solar arrays with a bullet-sized hole right through it. In order to shield something as large because the ISS, instead of using heavy thick plating, it uses something called a “whipple shield”. This consists of a skinny outer wall followed by alittle gap and a thick inner wall. The outer wall doesn’t take much speed out of the impact but it shatters the projectile into much finer pieces.

This means the K.E. is opened up into many smaller impacts on the inner wall. In some areas of the shield, the space between the two walls is stuffed with a high impact material such as kevlar or aluminium oxide. On the ISS, there are over a hundred different shield configurations, as a balance needs to be found between the weight and the amount of protection. Fortunately, we’re ready to do an excellent deal of testing on these sorts of impacts here on Earth. Since a typical firearm can’t generate orbital velocities, scientists back within the 60’s invented something called the Light-Gas Gun.

This works by using an charge to maneuver a piston and compress a sealed chamber of gas. The end of the chamber has a thin bursting disk, scored with a cross which bursts at a specific pressure. Once it bursts, the rapid expansion of gas accelerates the projectile up to orbital velocities. This is an example of what a small object can do to a block of aluminum. The projectile in this experiment was made out of polycarbonate and weighed just 7 grams. But when it collided with the aluminum block at 7km/s, it carved out a crater 5 times wider and 5 times deeper than its own diameter. To understand what goes on in orbital impacts, it helps to seem at the impact piecemeal . As the projectile collides with an object it decelerates extremely quickly, which compresses both the projectile and therefore the object. 

As the pressure of both objects increases, the temperature gets hot enough to melt the impact area and vaporize the projectile. The compression sends a shock wave through the object with enough strength to completely tear apart the material. All of this happens in a fraction of a second, meaning astronauts on-board the ISS would never see it coming.

But there's a replacement solution under research at the instant that would provide even greater protection to the ISS. While current whipple shields use kevlar or alumina between the walls, it's possible that this might get replaced with a replacement material that performs something called Rapid Puncture-Initiated Healing. This involves replacing the filling of the whipple shield with a liquid. As the debris passes through the shield at high velocity, the warmth and friction will stimulate the liquid to flow into the opening and plug it because it hardens. One test involved the liquid reacting with oxygen, which sealed the opening in but a second. Shields like these will got to be constantly improved as we send humans beyond our field of trackable space debris. Lighter shields that are easier to repair also will be crucial for end of the day trips to Mars and beyond.

Space junk removal around Earth

ISS

ClearSpace-1 are going to be the primary space mission to get rid of an item of debris from orbit, planned for launch in 2025. The mission is being procured as a contract with a startup-led commercial consortium, to assist establish a replacement marketplace for in-orbit servicing, also as debris removal.

Following a competitive process, a consortium led by Swiss startup ClearSpace – a spin-off company established by an experienced team of space debris researchers based at Ecole Polytechnique Fédérale de Lausanne (EPFL) research institute – are going to be invited to submit their final proposal, before starting the project next March.

Either way, we will be thankful that we've an environment here on Earth which protects us every single day. So make sure you're subscribed, so you can join in the discussion as we continue to learn more about all things space. Thank you very much for reading and I'll see you in the next article.


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