Growing Amount of Space Debris Threatens Satellites: Allianz Report

July 11, 2012

A study from Allianz Global Corporate & Specialty (AGCS) warns that “man-made space junk poses a serious threat to all space vehicles including those with humans on board.” The report goes on to explore possible ways to clean up space.

As an example the report cites an incident in April 2012 when the “European Space Authority lost contact with its Earth observation satellite Envisat, rendering it inoperative. Envisat will orbit Earth for approximately another 150 years before burning up upon re-entry into the atmosphere. If the enormous 8-ton ghost satellite were to collide with another object and break apart, the resulting debris cloud would escalate the already serious threat to operating satellites.”

The possibility of space collisions aren’t a remote possibility, as thye have already happened. Allianz noted that in 2009, “a defunct Russian satellite collided with and destroyed a U.S. commercial satellite, scattering more than 2000 pieces of debris into orbit. And in 2010 and 2011, the crew of the International Space Station (ISS) was forced to evacuate when a large piece of space debris came perilously close. On both occasions, the object was detected too late for the crew to perform an avoidance maneuver.”

The report also highlights the insurance industry’s pivotal role in supporting the aerospace industry. Allianz said “about a quarter of all satellites in the Earth’s orbit are insured against losses from physical damage, as well as service interruption.”

There are now more than 35 million objects in orbit, which have been launched there since 1957 when the first exploratory vehicles rose above the earth. They range from used rocket boosters and defunct satellites to space exploration equipment that has been lost or exploded.

“The space around our planet is becoming increasingly congested,” stated Thierry Colliot, managing director of space insurance at AGCS. “The number of objects is now so high that it won’t decay on its own through atmospheric drag. Instead, it’s actually increasing as objects collide and produce fragments, which in turn collide in a runaway chain reaction.”

Close to 800 satellites orbiting the earth’s atmosphere are under permanent fire by space debris. An estimated 16,000 objects larger than 10cm (app. 4 inches) have been catalogued so far. However, the report points out that “the projected amount of un-catalogued objects dwarfs this number. Estimates place the number of small objects between 1cm [app. 3/8 of an inch] and 10cm at around 300,000 and at 35 million for objects smaller than 1cm.

“These objects travel at very high velocities of 10 km [6.25 miles] per second, which is more than 10 times faster than a bullet. At these speeds, even tiny fragments can have a devastating impact. They can penetrate the surfaces of satellites and can severely damage the electronics, causing total loss in a worst-case scenario.”

The study asks the question as to how can satellites be better protected? It explained that in order to “avoid collisions or mitigate collision effects, avoidance maneuvers can be initiated, though trajectories of larger objects cannot always be predicted reliably or early enough. Furthermore, multi-layer insulation shields or impact absorption systems can limit damage in minor collisions.”

As the Space Risks report indicates, besides protecting satellites, “space authorities and scientists work hard to reduce overall space debris congestion. Today, satellite operators are obligated to de-orbit satellites within 25 years of their mission’s end, though only the latest generation of satellites has such functionality.

“End-of-life de-orbiting in Low-Earth Orbits is usually achieved through a destructive re-entry into earth’s atmosphere. Most of the structure burns up, owing to the drag and intense heat it generates. The remaining unburned fragments fall into uninhabited parts of the world or into the sea. The 140-ton Russian MIR Space Station was destroyed in this way after a series of de-orbiting maneuvers in March 2001.”

Colliot, however, noted that “systematic de-orbiting of new satellites at the end of their lives won’t suffice.” According to experts, an additional 10 major objects would need to be eliminated each year to reduce the debris population to a stable and sustainable level.

Another de-orbiting maneuver involves raising a satellite to a new, higher “graveyard” orbit, about 36,000 km [22,500 miles] above the Earth. However, this requires fuel and, as a result, effectively shortens the satellite’s operational lifespan. Nonetheless, it is now standard practice and may become law in the future.

“New technologies to eliminate or remove debris encourage hope,” the report indicated. “For example, laser tools that destroy larger objects or space tethers could enable a controlled de-orbiting of entire systems.”

Colliot described the new technologies as “exciting concepts of active debris removal.” However, he added, “at this stage, because of the high cost involved and technological restraints, we have not yet seen a real breakthrough.”

One alternative approach is to extend the life of existing satellites by refueling them. Mobile repair stations could bring faulty or old satellites back into service either by refueling or making use of their own thrusters to maintain the satellite’s orbiting altitude.

One of those breakdown services currently envisaged is called a Mission Extension Vehicle (MEV). MEV is a small satellite-refueling vehicle capable of docking with virtually any satellite while avoiding interruptions to the satellite’s operations.

Source: Allianz

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