What looks like a swarm of bees flying around a ball is actually a map of the junk and debris in low orbit (<2000 km) around the Earth. The plot is from NASA Earth Observatory. The dots are plotted according to the position of the debris at the time. They are not plotted according to their size. The debris pieces are moving as fast as 7,800 m/s, which is 5 miles/sec. They constitute a major problem for any spacecraft in low orbit from possible collisions.
There have been several previous diaries about the problem of Space Debris or Space Junk. Go to the Search feature and put those terms in "quotes" to find them. What is different this time is the proposal by the Swiss to remove some of the debris.
More about the Swiss plan is below the squiggle.
|Scale and Scope of the Debris Problem
This map shows the space junk out to the distance of geosynchronous
satellites, the kind your home satellite dish points toward. Notice the fine ring. Satellites and debris at this distance orbit the Earth in about 24 hours, the same time it takes the Earth to rotate. So, it appears to remain above the same point on Earth above the equator. Following this image is another view of the junk from above the pole of Earth.
This chart from the European Space Agency illustrates the types of objects and the increase in their number up to 2008. Currently, there are over 16,000 tracked objects of 10 cm size or larger. There are possibly 500,000 objects too small to track. This NASA article explains more of the scope of the problem if you want more info. Here is another url offering images and reading into the debris problem.
If you have a school globe handy, the 12" model in your kid's room, most of the junk is in orbit within about 1" of the surface. Most of the satellites of Earth are in orbit within that range of the surface. The International Space Station is in orbit about ⅓" above this school globe model. It has been visited many times by the Space Shuttle and the Russian Soyuz vehicles ferrying equipment and people.
The ISS and the visiting spacecraft all orbit at speeds of 7,800 m/s. When they are going parallel to each other, their relative speeds make it seem like a motionless ballet. Only by looking down to Earth is there a sense of high speed. But, if the motions of the orbiting objects is not parallel, collisions can occur at hyper-velocity. This has happened many times. Space junk collides with other junk. Junk collides with active satellites. For example, upon return of Shuttle flight STS-7, close inspection of one of the windows showed the damage in the image below. An object not much bigger than a fleck of paint caused this damage. A 1 mm scale is marked below the damage.
On flight STS-118, the heat radiator on the opened cargo bay doors was penetrated by an object. The images below show the location of the puncture, the entrance hole, and the exit hole. This posed no danger to the astronauts. But it does illustrate the danger of a strike by even a small piece of debris.
|The Swiss Proposal to Grapple the Junk
On February 15, 2012, the Swiss released the details of a plan
to begin removing the junk.
To combat this scourge, the Swiss Space Center at EPFL is announcing today the launch of CleanSpace One, a project to develop and build the first installment of a family of satellites specially designed to clean up space debris.
EPFL is Ecole Polytechnique Federale de Lusanne
. CleanSpace One is a project to build the first prototype in a family of “de-orbiting” satellites. The first one is to establish a proof of concept for the plan. Later, launches of many in a fleet of these small debris hunters could clear large swaths of orbit altitudes that are populated by many important spacecraft to reduce the likelihood of collisions.
Their plan has three large challenges. First, the satellite has to adjust its orbit to match its target’s orbit. To do this, EPFL laboratories is developing an ultra-compact motor. Second, when within range of its target, it will grab and stabilize it. That is a very challenging task. It is especially difficult, if not impossible if the satellite is rotating. The scientists are developing a grappling device inspired from nature. Finally, the grappled pair will “de-orbit” into the atmosphere, where the two satellites will be destroyed upon re-entry.
The following 4 min video from EPFL clearly presents the problem and their plan. There is also some commentary by Claude Nicollier, astronaut and EPFL professor.
Certainly, this is a problem that is large and won't go away on its own. Some debris will re-enter the atmosphere. But, most of it is so far above the atmosphere, it will take decades or centuries before it decays low enough. As Nicollier stated, it is like the global warming problem we face. Something needs to be done to address it. To do nothing is unacceptable.
I am curious what you think of this proposal.