Space Debris 101.
Space debris re-entry 101 aims to share the rudiments of space debris, its' consequences and the challenges that we are facing.
Space debris, a.k.a. space junks or space waste, are objects in space, principally in earth orbit. There are currently over 20000 tracked junks tracked by the Department of Defense's global Space Surveillance Network sensors (SSN). These tracked objects are mostly larger than 10cm of diameters where over 13000 of them are in Low Earth Orbit (LEO).
Space debris comes in two types :
Natural debris - Natural debris consists of cometary and asteroidal material called meteoroids. These are seen as meteors when they travel through Earth's atmosphere.
Artificial debris - Artificial debris consists of man-made objects. This includes dead or failed spacecrafts, rocket boosters, lost equipments, weapons, fragments from explosion or collisions etc.
For instance, the first piece of artificial space debris created was on 4th October 1957, when the last stage of the rocket that launched Sputnik-1 remained in orbit.
"The density of space junk peaks around 620 miles up, in the middle of so-called low-Earth orbit. That's bad, because many weather, scientific and reconnaissance satellites circle in various low-Earth orbits. " - Sam Kean.
Space debris re-entry problem
Space junks poses risks to space exploration efforts. Collisions may occur between debris and satellites or spacecrafts. In 1996, Cerise, a french military satellite was hit by space debris object from a French Arian rocket, marking the first known case of space accident between two artificial objects.
Another huge concern of space debris is the atmospheric re-entry. Re-entry of larger, uncontrolled objects can be a hazard to people and properties. Around 40 large debris objects that weigh up to 800kg re-enters randomly annually. Many large objects in LEO lack capability to control re-entry location and this may be due to a mission that ended prematurely. Most debris burns up in the atmosphere, however, this does not exclude larger debris objects that can reach the ground intact. Statistics drawn shows that in average, one or two pieces of debris re-enters Earth's atmosphere daily. To list down a few events :
May 1966, Brazil
1. May 1966, Brazil : Spacecraft debris was spotted in the Rio Negro District of Brazil and was identified as the metal parts from a stage of the Saturn development test that was launched in 1964.
Jan 2001, Saudi Arabia
2. Jan 2001, Saudi Arabia : A motor casing from the Payload Assist module that weight around 70kg, re-entered the atmosphere and slammed down in Saudi Arabia.
Fortunately for mankind and as far as we are aware, apart from a woman in the southern USA who was injured by a piece of US military satellite, no one has been killed by re-entry debris. The Aerospace Corporation compiled a list of relative risks and showed that once in 100 years, someone may be injured or killed by space debris somewhere in the world.
Dealing with space debris
A number of solutions have been put on the table to this problem. Most existing solutions require expensive use of technologies. For example, space tugs could be employed to catch large space debris and lower their altitudes for natural decay. NASA carries out re-entry survivability analysis for all large spacecraft and indicates if the object may survive the re-entry process and attempt to control the objects to a safe area.
There are currently no international treaty on minimising space debris. However, voluntary guides are published and space agencies are putting in efforts regarding this matter.
In Re CAE..
The FAST software proposed by Re CAE will be a tool that allows a quick and precise re-entry trajectory prediction and survivability of debris.
Stay tuned to learn about space debris re-entry breakup step-by-step in our upcoming blog!
