Universe Today

The U.S. Air Force began upgrading its ability to predict possible collisions in space after two satellites collided in February 2009, and has now done a collision analysis on over 800 maneuverable satellites. They hope to be able to track 500 more non-maneuvering satellites by year's end. But maneuverable satellites aren't the problem. The amount of space debris has risen by 40 per cent in the past four years alone. The Air Force Space Command now tracks 21,000 orbiting objects that are 10 centimeters or more across – including the 800 working satellites – and estimates that there are 500,000 smaller fragments in orbit.
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One of the emerging concerns in space exploration is space debris; the outer space equivalent of pollution on Earth. Over the past 40 years, abandoned or obsolete man made space objects have been left in orbit around the Earth. In general we don't worry much about them because most will eventually fall out of their orbit and burn up in the Earth's atmosphere. However, these objects can collide creating the scattered fragments we call space debris.

The problem is further exacerbated by two facts. First, these objects are traveling at very high velocities around the earth. To put this in perspective, a bullet is deadly because it is an object traveling at high speeds; its momentum comes mainly from its high velocity. Now think of much smaller objects traveling at speeds 10 times faster than a bullet; there are thousands of them out there, and they can come from any direction at any time. This is the environment most space craft and astronauts operate under on a regular basis.

The second problem is the proliferation of space debris. As space debris scatters, they collide with other objects to create even more debris and so on. This phenomenon is call the Kessler syndrome. While space debris might be a manageable threat now, it can seriously hinder space exploration in the future if not dealt with.

The seriousness of the situation came with two recent events in space. The International Space Station had to alter its orbit to avoid a particularly dangerous patch of space debris. The damage, even to a station as well armored as this one, would have been in the millions and halted a lot of important research. The second event was the first collision of two satellites in February of 2009. What if this had happened to a major communications satellite? The damage would also have high cost and only further exacerbate the problem with more space debris.

Fortunately, steps are already being taken. The United States Military and NASA both have agencies that monitor debris and are working on solutions to deal with them. One hindrance to implementing some solutions are the political implications. For example, if Strategic Command – the Military Debris monitoring agency – was to use laser to get rid of space debris, the technology would be the first step to a space weapon and raise the concerns of other nations. Hopefully solutions can be found that will agreeable to everyone.

If you enjoyed this article there are several others on Universe Today that you might enjoy. There is an article on space debris with illustrations that show the extent of the problem. There is another article about debris coming dangerously close to the Hubble Telescope.

You can also find other resource about the subject on the internet. Wired.com has an interesting article about how to track space debris online. There is another great article on the Howstuffworks website that goes into detail about the problem.

You can also listen to a podcast on the issue on Astronomy Cast. Episode 82 Space Junk is quite interesting.

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Space junk is the abandoned equipment, trash, and broken parts left behind in space. They can be anything from deactivated satellites to an astronaut's lost toothbrush. This junk puts littering into a whole new frontier.

It might seem easy to dismiss the potential problems posed by space junk. For starters, it's all outside our atmosphere, so there is no immediate threat to the planet. It's all in the vacuum of space, so there is little that can be really disturbed by the presence of our man made stuff; especially in a region of space that has natural debris such a meteors, asteroids, and space dust. If it comes to the worst most of the stuff would simply burn up in the atmosphere if their orbits decayed enough to be pulled in by the Earth's gravity.

However, this thinking is dangerously nonchalant. If not dealt with effectively, space junk can present new and unnecessary challenges to future space exploration. The main reason is the speed of the objects in space. If you have ever been in a hurricane or tornado you know one of the things you are told to do is board up the windows of your home and try to keep indoors in an enclosed space. We know to do these things high speed winds can accelerate every object, turning them into lethal missiles. This is just with objects probably flying through the air at 200 km per hour. Think about being in a storm where objects could travel at 15,000 km per hour. You wouldn't even be safe in the innermost room of your house. This is the potential danger to equipment and people posed by space junk.

The first space collision between space debris and functioning equipment just occurred this year over Siberia when a satellite was destroyed. Another problem is that whenever pieces of space junk collide, they create even more debris, which increases the chances of dangerous collisions. This is called the Kessler syndrome, and it raises a warning signal that the problem needs to be more aggressively resolved.

Fortunately there are already agencies monitoring space junk and looking for solutions. One of them is the US Strategic command which has already tracked 13,000 detectable objects. NASA also has an Orbital Debris Protection Agency that also helps with monitoring, and is working to protect craft and astronauts from space debris. Hopefully workable solution that mitigate the problem will develop.

If you liked this article there are others on Universe Today you might enjoy. Space debris illustrated is an article that shows in pictures the scope of the problem. Another great article is about low orbit where the majority of space junk resides.

There are other interesting resources on the web. You can go to the NASA Orbital Debris Protection website to see what NASA is doing to deal with the problem of space debris. Wired.com also has an interesting call about the International Space Station's close call with space debris.

You can also listen to Astronomy Cast. You will definite like Episode 82 Space Junk.

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Low orbit is the general region at the top of a planet's atmosphere but still within the influence of its gravitational field. When most people in aeronautics refer to low orbit they are referring to low Earth orbit, the region below 2500 km above the Earth's surface.

This region is very important when talking about spaceflight in general. The space shuttle, for example, is actually a low orbit space vehicle. It can't be used to go anywhere outside this region of space and is normally used to carry payloads and conduct experiment in the region of space near the Earth. It's also the region where many of the artificial satellites hold their orbit. Any higher and they leave the influence of Earth's gravity. It's also the area of space where important structure like the International Space Station are. Another characteristic is that most objects in this region are still subject to atmospheric drag. This explains why the orbit of man made objects decays over time. The friction slowly reduces the orbit speed of artificial satellites until they are no longer fast enough to resist the pull of gravity.

Despite its importance to many aspects of spaceflight, low orbit also present some unique challenges. One of them we created ourselves. We now know that the space between planets isn't empty. As a matter of fact, this region of space has numerous objects, such as meteoroids, that vary in size from a grain to the size of a bowling ball. Some of these debris collide with satellites and other space vehicles and break off pieces. Over time, this has left a cloud of man made debris that now populates the entire low Earth orbit region. This is a problem because many of these pieces of space junk now move at incredibly high speeds that can make them deadlier than bullets or debris thrown by tornadoes and hurricane force winds. This presents a potentially dangerous hazard for manned space missions. According to NASA, there are now around 8,500 pieces of space debris that are identified as being larger than 10cm. That is not including the estimated millions of pieces of debris that are smaller than this.

Another problem that may loom in the future is that we may run out of space. Low Earth orbit is vast, but finite, and current satellites can only keep orbit within Low Earth Orbit. Already there have been a couple of reports of satellites colliding. Hopefully in the future advances in aeronautics will find solutions to these problems. This just underscore the importance of low orbit to the future of spaceflight.

If you enjoyed this Universe Today article there are others you might enjoy. Here is an article on space debris. Another is an interesting article on the collision of two satellites.

Here are some resources that I found helpful. This article on NASA website had some helpful info. Also this was an another article on space debris.

You will also like this episode of Astronomy Cast.

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