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Space debris: Where does it come from, and what can we do about it?


November 12, 2012

Representation of a satellite being destroyed by collision with orbital debris (Image: ESA)

Representation of a satellite being destroyed by collision with orbital debris (Image: ESA)

Image Gallery (9 images)

Orbital debris is (nearly) forever, and threatens to render near-Earth space (under 1250 miles, or 2000 km altitude) unusable, and all but impassible. The 2007 Chinese anti-satellite test and the accidental collision between two communications satellites in 2009 highlighted the need to study orbital collisions of modern satellites. The NASA Standard Breakup Model (SBM), based on hypervelocity collision studies of 1960s-era satellites, fails to accurately describe collisions of modern satellites, owing to advances made in materials and construction. To address this problem, NASA is updating the SBM by enlisting the University of Florida to build and destroy a modern dummy satellite called DebriSat.

DebriSat is a dummy 110 lb (50 kg) satellite, 20 inches (50 cm) on a side, whose construction will be representative of modern near-Earth satellites.

DebriSat will have a structure as close to that of a functional modern satellite as possible (Photo: Mark Werremeyer and University of Florida)

Although DebriSat is a nonfunctional engineering model, it will incorporate new materials and construction methods such as multi-layer insulation, composite materials, modern computers and communication equipment, and solar panels with high-efficiency solar cells. For example, electronic circuitry will be made of modern chips, components, and board materials, but need not function. The DebriSat design is intended to be representative of all sizes of near-Earth satellites, and will undergo a hyper-velocity impact test at Arnold Air Force Base.

Hypervelocity impact damage (Photo: NASA)

The image above shows a 1.2-cm (0.47-in) aluminum sphere striking a seven inch (18 cm) thick aluminum plate at a velocity of 6.8 km/s (4.2 miles per second), giving some idea of the destructive power of hypervelocity impacts. The projectile fired at the DebriSat will be a two inch (5 cm) aluminum sphere impacting at a speed of seven km/s, giving the collision a total energy equivalent to about four pounds (1.8 kg) of TNT, more than enough to thoroughly disassemble DebriSat. The resulting fragments will be counted and studied to provide a better understanding of future satellite breakups.

Trackable (>4 in. or 10 cm) orbital debris in orbit around Earth. Largest ring are satellites in geosynchronous orbit (Image: NASA)

Just how important is the problem of orbital debris? At present (2012), there are roughly one thousand operational satellites, half of which are in near-Earth space, according to the Union of Concerned Scientists Satellite Database. But in addition to about 40 derelict satellites, the U.S. Space Surveillance Network is tracking more than 22,000 pieces of debris, each of which is larger than about 4 inches (10 cm), the reliable detection limit of their radars and telescopes. Only two weeks ago the explosion of a Russian upper stage rocket added over 500 large pieces of debris to the problem.

Dispersing orbital debris from the Iridium-33 - Cosmos 2251 collision up to a year following impact (Image: NASA)

Collectively, this debris has caused a number of second-hand collisions or near misses, where a large fragment from an earlier collision threatens an unrelated vehicle. Here are some of the instances of second-hand collisions that history records:

  • 1981 – Cosmos 1275 destroyed
  • 1991 – Shuttle avoidance of fragment of Cosmos 955
  • 1996 – CERISE (Fr.) damaged by Ariane upper stage fragment
  • 2006 – Express-AM11 (Rus.) disabled
  • 2009 – Massive collision of Iridium-33 and Cosmos 2251
  • 2009 – ISS near-miss of fragment from Cosmos 1275
  • 2012 – ISS avoidance of fragment of Iridium-33

It is clear that the number of collisions or near-misses with orbital debris is increasing in recent years. This is not because of a jump in the number of operational satellites, but rather is due to rapidly increasing amounts of sizable orbital debris. Like shooting for quail, it is far easier to succeed when using a shotgun than a rifle.

Two things make this analogy imperfect: in space, the orbital debris is around for decades instead of a few seconds, and when you hit a quail, it doesn't break into hundreds of pellets, each of which can kill another bird. What this does sound like is nuclear fission chain reactions, which brings us to the Kessler Syndrome.

Very roughly, the Kessler Syndrome is entered when the amount of orbital debris in near-Earth space exceeds a critical value. At that point, more new orbital debris is generated from collision of objects already in orbit than is removed by re-entry or comminution into relatively harmless dust. This increases the rate of collisions, which increases the amount of debris, and so on. In the end, near-Earth space looks like it has gone through a grinder – filled with unpredictable swarms of relatively small but thoroughly lethal orbital debris that, in the end, can make near-Earth space unusable, and all but impassible.

Projected amount of orbital debris resulting from the Kessler Syndrome if spaceflight is stopped for the next 200 years (Image: NASA)

The pace of the Kessler Syndrome is slow in the early stages, owing to the rarity of large-scale collisions. But once the amount of orbital debris passes the critical value, the syndrome will continue to completion even if no additional satellites or launch vehicles are added to the picture. Most calculations today suggest that the density of orbital debris is above the critical value in large portions of near-Earth space, especially above about 500 miles (800 km).

If the estimates are valid, we are left with only two broad courses of action. We can give up using space for a thousand years or so while the debris is falling from the sky, or we can clean up our mess. The models predict that simply reducing the amount of mess we make in the future won't work. We have to actively remove a significant fraction of the orbital debris. Dodging better won't work either in the end, as this doesn't stop or even substantially slow the Kessler Syndrome.

There is no real question of being able to remove large hunks of debris. Dozens of possible methods have been suggested, and several are under development. However, when you get down to fundamentals, this is a classic short-term vs long-term dilemma. The cost of removing defunct satellites is much larger than the short-term risk that they will eventually destroy another satellite, but is far smaller than the long-term near certainty that humanity will lose access to space if the debris problem is simply ignored. Short-term your company wins; long-term your species wins. It's our decision to make, and the sooner the better.

Source: NASA Orbital Debris Program

About the Author
Brian Dodson From an early age Brian wanted to become a scientist. He did, earning a Ph.D. in physics and embarking on an R&D career which has recently broken the 40th anniversary. What he didn't expect was that along the way he would become a patent agent, a rocket scientist, a gourmet cook, a biotech entrepreneur, an opera tenor and a science writer. All articles by Brian Dodson

My word, isn't human progress a wonderful thing.

If we ignore archaic hominids, it has taken H. Sapiens something like 200,000 years to turn the 197 million square miles of the surface of the planet, including the oceans, into a festering, polluted. trash can. Now, with all the "improvements" [sic] in technology we have managed to do the same to 24.5 billion cubic miles of the space surrounding us in a mere 55 years.

Before anyone feels the need to tell me that space debris is mainly metal and therefore not "festering" just remember that the vast majority of it has a coating of the human excrement that has been discharged into space.

Does the species really have a continuing right to exist?


What about using a huge space-sail type of sheet anchored at 3 or 4 corners to 'sweep' through the debris field and redirect the smaller debris so they fall out of orbit and burn on re-entry?

Bob Fately

Space debris, is the New Recycling Job Opportunity waiting to Happen! How can you ask, what do you do? You get it back, melt it down and make new products! 1. Nasa and everyone involved for putting rocket stages out there etc., needs to make going out into space as safe as possible. 2. Higher and trian people to work out in space. 3. develop ways to retreive metals and plastics floating in space, then get them...


Bob, the velocities of those tiny fragments gives them TREMENDOUS amounts of kinetic energy. Just look up the ballistics of a few bullets to see what I'm talking about here. A 130 Grain bullet in .270 caliber has a muzzle velocity of 3,200 Feet per second and 2,955 Ft.Lbs of kinetic energy in it. A 150 Gr bullet of the same caliber has a MV of 3060 FPS and KE of 3118 Ft.Lbs. A 55 Gr. .223 caliber bullet moves out at 3,200 FPS and has 1250 Ft. Lbs of KE in it. I saw just a copper plated lead (NOT armor piercing!!) .223 (5.56 NATO) round punch clean through two plates of mild steel (one was .125" thick, the other behind it was .250") like a hot knife going through butter. The holes in the plates were about .375" in diameter with jagged edges. Even a small flake of paint going about 22,000 MPH hit one of the windscreens on the shuttle and cracked it! Just a flake of paint! What kind of material can absorb that kind of energy without being destroyed in the process? It would have to be light enough to be able to get it up where it could be used, and cheap enough to be affordable for the job it's doing. Maybe some sort of a quilt made up of Kevlar and ballistic Nylon could work. With the filling part of the quilt several CM thick and made up of wadded up Kevlar to give it a stretchiness to slow the debris down a bit, it might be able to collect up debris like flypaper. And if there is some kind of adhesive or goopy foam that could be sprayed on it after being deployed and would remain in that state in space, it might be able to entrain the debris until enough of it was collected where it was cost effective to then de-orbit the whole mess. That foam that they use for crowd control might be worth a try. It's too costly to go after 22K pieces of junk piece by piece, but boy oh boy, talk about job security!!


Expanded Viewpoint

solar mirror to vaporize them.could also slow them down.


soon you won't be able to see the earth from the moon, it will protect us from aliens. just try and get us through our debris field.


If our response to climate change is any guide, then we will do nothing. It will come as no surprise to future generations, who will be all to well aware of how good their ancesters were at passing them the buck.

Mel Tisdale

If a high power electromagnet was orbited it could alter the path of every bit of electrically conductive material that crosses its field; the greater the difference in velocity the bigger the change it would make. With an electromagnet it can be turned off when passing still functioning satellites or debris that it would make more dangerous rather than less.


It is good to see that more interest is being taken over the serious problem of SPACE DEBRIS or Junk, particularly the debris in Low Earth Orbit. We are continually told that Space Debris is only a threat to the multitude of satellites in range of it’s orbital path, but I firmly believe it is also poses a very serious problem to everything here on Earth. Whether it’s natural or unnatural debris, I believe that Space Debris is continually managing to survive its frictional path through the atmosphere to impact with our Earth and is a far bigger hazard than most scientists are prepared to admit to. Although, there is some action of the tracking and detection the debris in LEO, it’s really only the first step on a very high ladder. The main problem and objective being when and how to return it all back to Earth safely and so eliminating the potential threat it poses to everything on here on Earth. JOHN HALL

John Hall
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