Tuesday, December 8, 2015

Satelit Iridium

an Iridium communications satellite stopped transmitting. In the following hours, the U.S. space surveillance network reported that it was tracking two large clouds of space debris. One was the silent Iridium satellite and the other to a defunct Russian military satellite called Cosmos 2251.

Those space debris were the result of a collision at high speed, the first that is known of this type of collision between satellites in orbit. The impact generated more than 1,000 fragments of at least 10 cm and one much larger number of smaller debris. Waste was scattered around the planet in the form of a deadly cloud.

Space debris represent an urgent problem for ships orbiting around the Earth, and might worsen enough. When these remains density exceeds a certain threshold, forecasters predict that the fragmentation caused by collisions will generate a reaction chain that will fill our skies with ever more amounts of fragments. By some estimates, that process may already have begun.
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An obvious solution would be to find a way to remove these residues. One possibility would be to shoot them with a laser, steam them for parts and cause that remains out of our orbit. However, the smaller remains cannot be destroyed in this way to be too difficult to locate and track.

Another option would be to send a special ship able to pick up the fragments with a network or any other type of capture process. But these missions are severely limited by the amount of fuel that can lead.

Today, Lei Lan and his companions of the Tsinghua University in Beijing (China) proposed a different solution. His idea is to build a motor that converts the debris in fuel so that it can move almost indefinitely while clean sky.

The concept is simple in principle. At a temperature high enough, any element can be converted into a plasma of electrons and positive ions. This can be used as fuel to accelerate it by an electric field.

But the details are complex. In particular, the task of turning waste into useful plasma is not at all easy.

Lei team concentrate their efforts in the debris of one size of less than 10 centimeters, the things that the laser ablation can not address. His idea is to capture the debris with a network after transfer to a ball mill, a rotating cylinder partially filled with abrasion-resistant balls which sprayed debris.

The resulting powder is heated and is introduced into a system that separates the positive charge of the electrons from negatively charged ions. Positive ions then pass through a powerful electrical field that accelerates them, converting them into high energy and generating momentum while they are expelled as exhaust. Electrons are also expelled to maintain electrical neutrality of the special ship.

Of course, real momentum that produce these processes depends on the density of waste, the nature of the dust generated, the size of the positive ions... and so. All of these factors are difficult to determine.

And while the ship would not have why to carry fuel, you will need a power source. Exactly where it will be is not clear. The team of Lei says that solar and nuclear energy will be sufficient, but they do not address the serious concerns which would create any vessel powered by nuclear energy in orbit around the Earth.

However, the work gives what to think. Space debris are a problem that looks rather worse in fencing future. It is an area that desperately needs new ideas until the next big collision fill the orbits of the Earth with even more trash.

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