China’s Long March 5B rocket fell out of orbit last weekend during an uncontrolled re-entry to Earth. It landed in the ocean without incident, where most experts believed it would. However, this oceanic destination was the product of chance and not of a goal. As the world watched with anticipation, valid questions were asked. What are the chances of it falling to earth? And would the pieces touch the ground? How big would they be? Finally, why the confusion and uncertainty as to when and where the rocket would fall?
NASA officials, like others, have twice criticized China’s handling of the descent of their used rockets as irresponsible. International standards for the management of end-of-life space assets have been in place for decades. When a space asset is launched, it must return to Earth in a controlled manner at the end of its mission. While this is certainly the goal, it doesn’t always happen.
On March 26, a SpaceX Falcon 9 booster rocket suffered a similar fate. The Falcon 9 rocket’s Merlin engine failed to reignite at the appropriate time, leaving the reentry of the second stage unchecked. There was no media coverage, no anticipation, no warning and no condemnation. The second stage returned with fireworks spilling debris on the northwest. Four 200-pound fuel tanks hit the ground when the first video messages aired on Twitter. A tank landed 20 feet from a house. Debris from the Falcon 9 booster fell on farmland, orchards and rural communities. The odds are still in favor of sparsely populated areas. If the booster rocket had entered 30 seconds earlier, the debris would have fallen near a large coastal town.
Following the event, a 300 km long linear cloud appeared over Oregon. Reflecting the rocket’s reentry trajectory, it lingered in the air and slowly rushed for more than three hours. While large objects obviously grab the headlines, all sizes and types of debris material enter the atmosphere and slowly fall to the ground and have the potential to come into contact with humans and nature. Could these finer particles of space debris pose a health risk?
The chances of a person being struck by space debris of any size are slim. Quite simply given that 71% of the globe is made up of water and that urban areas encompass 3% of the territory. Agricultural fields occupy 40 percent and the remainder is surrounded by nature. In addition, most rockets and space assets descend in a managed and controlled manner. An uncontrolled rocket entry has a 29% chance to land. If this happens, then there is a 3% chance of hitting a populated area.
Using these numbers, the Chinese Long March 5B had a 0.87% chance of hitting an urban area. These are small chances, but not impossible. The question is not whether space debris will strike a house and / or a populated area, as it has already happened, more than once. The question is, given the rapid race to commercialize space, how often will this happen and what can we do – if anything – about it. Do we have the systems in place to finely monitor the space and identify re-entry events that may impact land and populated areas?
The commercial space race reminds most of us of the 1960s, the Apollo missions and the first satellites. These Cold War developments created the aerospace industry that we have today. Although historic and incredible, the Cold War space race is pale in comparison to what is happening now.
As a perspective, this graph shows the annual satellites launched according to the Union of Concerned Scientists satellite database.
Plot of satellites launched into space by year according to the UCS Satellite database.
source data: https://t.co/nVAArVlpNj pic.twitter.com/43h44Y0sgQ
– Mike Hankey (@meteormanmd) May 12, 2021
Since 1957, more than 6,000 rocket launches have taken place, deploying 11,370 satellites in space. About 6,900 of them are still there. Currently, 1,500 Starlink satellites are in space, 12,000 are planned and another 30,000 are reserved. SpaceX is leading the way in satellite launches and commissioning, but it is one of many space flight service companies, nationally and internationally.
As the exploitation of space increases, the more likely it is that debris will fall, some uncontrolled and some reaching the ground. Of growing concern is the collision between satellites and satellites with space debris.
This has also happened before. In 2009, an Iridium satellite and a former defunct Russian military satellite collided. Spraying at 26,000 mph, the impact created thousands of smaller objects. Accidental and intentional incidents have contributed to an estimated 129 million man-made fragments larger than 1mm currently in orbit. Over 900,000 are 1-10cm fragments with over 34,000 objects larger than 10cm. However, only 28,000 of these assets are tracked by military and civilian entities to varying degrees.
NASA scientist Donald Kessler in 1978 described the potential for a cascading impact scenario. He said if or when the space becomes too crowded, a collision incident could result in a chain of impacts. This domino effect would produce so much debris that the space would become unusable for any purpose. Space debris would potentially rain into Earth’s atmosphere for decades.
As the density of objects increases, the chances of achieving this effect also increase. The start of this new commercial space race demands that we be more responsible, not less. To raise the standard, not lower it.
International collaboration and communication are essential to combat space debris. Automated avoidance systems are needed in newer satellites, as are open trackers and tracking protocols. In addition, an improved observing infrastructure could better monitor space debris and its reentry, regardless of the destination. The commercialization of space has provided and will continue to provide incredible opportunities for humanity. However, it must move forward with the utmost caution, ingenuity, collaboration and transparency.
Mike Hankey is an entrepreneur, software developer and director of operations for the American Meteor Society. In 2010, Hankey and his company rebuilt the AMS online fireball tracker and since then have collected over 200,000 testimonials about bright lights and fireballs in the sky. Sometimes these systems receive and track re-entry events of space debris.