by Launchspace Staff
Bethesda MD (SPX) Oct 16, 2012
Space debris issues continue to proliferate and concern continues to build. It is not surprising that the big aerospace companies are gearing up to take advantage of any future debris removal contracts. The fact is that space debris is really a "ticking time bomb" that will go off sometime within the next several years.
No one knows when a chain reaction of debris/satellite collisions will take place, but it surely will happen. There are several hundred active satellites in low earth orbits. These are joined by an unknown number of dangerous debris objects.
Estimates place the number of potentially life-ending objects at over 100,000. This number could be much higher. We do know that there are over 20,000 objects that have a dimension of at least 10 cm. But, there are many smaller objects that cannot be tracked.
Every one of these objects is traveling at over 7 km/sec. Each has its own orbit. Thus, closing speeds between objects and active spacecraft can be higher than 14 km/sec.
The volume of space that includes low earth orbits is big, but it is filling up with debris. It is only a matter of time before collision frequencies exponentially increase and all operational spacecraft in orbits between 700 and 1,100 km altitude are violently destroyed.
Many methods of removing space debris have been proposed. The more popular approaches involve high-powered lasers, space tethers, harpoons, nets and grappling devices. The latest proposed idea involves the use of ballistic gas. Boeing has just filed a patent application that describes a method of removing space debris by hitting them with puffs of gas.
In effect, the idea is to slow down large debris objects, resulting in a reduction in perigee altitude and exposing the object to increased atmospheric drag. This, in turn leads to re-enter and burn up in the atmosphere.
All of the suggested approaches have one common element: high cost. Almost every idea that is physically viable would have a very expensive price tag. The majority of large debris objects consist of expired satellites and expended upper stages. These large objects would be the targets for any debris removal program.
When removing individual debris bodies, there are two major cost items: the launch vehicle and the removal device. One must weigh these costs against the benefit achieved. The value of each piece of debris is zero, because it offers no service, but only represents a potential threat to space traffic. In addition, no one knows which debris objects should be removed.
Obviously, we would want to remove a minimum number of the most threatening objects in order to reduce the collision threat to a yet-to-be-determined acceptable level. Let's say that magic number of removals is five-per-year and the cost of each removal is $250,000,000.
Each year we would have to invest over $1 Billion. How are we to pay for this? One way is to tax every new satellite launch. Since there are roughly 125 satellites launched each year, the tax would be about $10,000,000 per spacecraft.
The Boeing patent suggested the use of "ballistic gas," a quantity of cryogenic gas, such as xenon or krypton, delivered by a small satellite. The gas would be released as a cloud in the same orbit as the targeted debris, but traveling in the opposite direction. The cloud would be short-lived but hopefully long enough to hit the targeted debris.
In theory, by the time it hit the gas would have expanded to the extent that the debris would not be damaged, but only slowed down. The inventor further claims that for larger satellites or those in higher orbits, multiple puffs might be needed. Of course, one obvious question must be asked; What happens to the gas-filled satellite? Does it become a piece of space debris?
With all of these ideas on removing debris maybe some reality show producer will come up with "The Amazing Space Debris Race."
Space Technology News - Applications and Research
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