SpaceX Now Valued at $350 Billion Facing Space Debris Problem(Ⅲ)

By Yibai, Jointing.Media, in Shanghai, 2024-12-27

Space debris – a threat to the sustainability of the space industry

On 21 October, SpaceNews reported that a 6,600-kilogram US communications satellite, Intelsat 33e, had suddenly disintegrated. Astronomer Jonathan McDowell said the disintegration could have been caused by a collision with other space debris or an explosion in the satellite’s internal propulsion system.

Space debris is a product of human space activities and consists mainly of non-functional man-made objects in orbit or re-entering the atmosphere, and their debris and components, also known as space junk, mainly distributed in the airspace between 2,000 kilometres and 36,000 kilometres above the ground. Mission debris accounted for 13 per cent, rocket debris for 17 per cent, failed spacecraft for 22 per cent and disintegrated debris, i.e. debris from spacecraft explosions or collisions, for 43 per cent. In terms of orbital distribution, space debris is mainly distributed in three regions, namely the LEO (low earth orbit) region below 2,000 km, the medium and high orbit region at 20,000 km and the geosynchronous orbit region at 36,000 km, with the most intensive distribution in the region between 600 and 1,000 km.

According to the European Space Agency (ESA), between 1957 and January 2021, more than 10,000 satellites were put into orbit by mankind. Of these, about 6,250 satellites are still in orbit, of which about 3,600 are still operational. By January 2020, more than 28,000 pieces of debris will be regularly tracked and catalogued by the Space Debris Monitoring Network (SDMN), and the total mass of man-made objects in near-Earth orbit will exceed 9,200 tonnes. ESA is currently tracking more than 34,000 objects larger than 10 centimetres, but in reality there are millions more smaller pieces of debris. It is estimated that there are more than 130 million pieces of debris smaller than 0.4 inches (1 cm) in Earth’s orbit, many of which are undetected by current monitoring systems.

The number and variety of objects in space posed a major challenge to the safety and sustainability of future space missions. Since 1999, the ISS has changed course more than 25 times to avoid space debris. However, some debris continues to collide with the ISS. By 2019, more than 1,400 meteoroids and orbital debris have been recorded as hitting the ISS. In particular, in low Earth orbit (LEO), there are thousands of objects travelling at speeds in excess of 28,000 kilometres per hour1 (17,500 miles per hour). Extremely fast, active satellites and spacecraft colliding with debris as small as 1 centimetre can cause catastrophic damage. The average impact speed of space debris is 10 kilometres per second, so the kinetic energy generated by centimetre-sized debris is equivalent to that of a small car hitting a satellite at 50 or 60 kilometres per hour.

One of the most significant space debris events in history was the 2007 Chinese anti-satellite missile test, which deliberately destroyed the Fengyun-1 weather satellite and created thousands of pieces of debris. In 2009, two satellites, Cosmos 2251, which had been abandoned for 14 years, and Iridium 33, which was in service, collided in orbit. This was the first time that two satellites had collided in orbit. The collision occurred at a relative speed of about 11 kilometres per second (25,000 miles per hour) and resulted in the total destruction of both satellites and the creation of more than 2,200 new pieces of space debris.

These events have raised awareness of the growing threat of the Kessler Syndrome. The threat of the Kessler Syndrome is becoming more real as the number of objects in space increases, particularly with the proliferation of satellite constellations such as SpaceX’s Starlink and OneWeb. While these constellations provide vital global communications services, they also exacerbate already crowded orbits and increase the likelihood of collisions. The growing number of space missions being undertaken by commercial enterprises, government programmes and private companies may exacerbate this problem.

(To be continued)

Notes:

1. The speed at which an object moves in a circular motion just above the Earth’s surface is the first cosmic velocity, 7.9 km per second, and is also the minimum launch speed for artificial Earth satellites and the maximum orbital speed.

2. In 1978, NASA Johnson Space Center scientist Donald Kessler and colleagues made some points about the future development of space debris predictions, known as the Kessler Syndrome. It predicts that when the density of objects in a given orbit reaches a certain threshold, a chain reaction will occur. In this case, each collision creates more debris, which leads to more collisions, creating a self-perpetuating cycle. Over time, this could render certain regions of space unusable for new missions, severely hampering space exploration and satellite operations.

Edited by Wind and DeepL

Image:Starlink Satellites over Carson National Forest M Lewinsky | M Lewinsky/CC BY 4.0

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