The Conversation contributed the article to Space.com's expert voices.
There is a senior research fellow in the University of Southern QUEENS.
There have been two separate incidents of space debris hurtling back to Earth.
There was a rocket re-entry over Malaysia on Saturday. The parts that turned up in New South Wales were from the Crew-1 mission.
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It's safe to say that such incidents will only become more frequent as the space industry continues to grow. How much of a risk?
The leftover parts of a space system are referred to as space debris. It could be a satellite that has reached the end of its life, or a piece of a rocket system that has fulfilled its purpose.
Three Long March 5B rockets have been launched by China, and each has been left in an uncontrollable circle. It's not possible to know where they would land.
When it comes to the debris found in the Snowy Mountains, the company de-orbits its rocket parts in a controlled fashion and designs other components to burn up. These things don't always go to plan.
How dangerous is space debris?
Only one person has ever been struck by it. The piece struck Williams in 1997. It looked like it came from a Delta II rocket. She reported it to authorities after picking it up.
With more objects going into space and coming back down, the chance of someone being struck is increasing. The Long March 5B is an example of this.
Three times this model has been launched.
The one-in-10,000 range is the most accurate estimate of the chances of space debris hitting someone. The chance of someone being hit in the world is very high. The chance of someone being hit is in the order of one in a trillion.
There are many factors behind the estimates, but let's just focus on one. The image below shows the path of the recent Long March 5B-Y3 rocket, as well as its re-entry location.
The rocket flies above the ground for a long time.
About 20% of the vehicle's time is spent over land. There is a 4% chance that the Long March 5B re-entry will happen over an inhabited area.
This might seem high. The chance of injury or death decreases when you consider how much of the land is actually occupied by people.
There is a higher chance of damage to property. For every re-entry of the Long March 5B, it could be as much as 1%.
The risk of space debris will increase with the number of objects being launched and re-entries. Many more launches are involved in the current plans of companies and space agencies.
The space station is expected to be finished by the end of the year. South Korea recently became (opens in new tab) the seventh country to launch a satellite that was heavier than one tonne with plans to expand its space sector.
It is highly likely that the chances of being hit are only going to increase.
There are two questions to think about.
Predicts are the first thing we'll start with. It can be difficult to predict where an object will come back to Earth. Uncertainty of the estimated re-entry time will be between 10% and 20%, according to the general rule of thumb.
An object with a predicted re-entry time in ten hours will have an uncertainty margin of less than an hour. If an object is in the air for 60-90 minutes a day, it could enter most places.
It will take a lot of research to improve the uncertainty margin. We won't be able to predict an object's re-entry location more accurately than within a 1000 km range.
Latest update on the Chinese rocket booster from @AerospaceCorpThe current tracking has it crashing in about 6 hours, at 5:15 pm UT 30 July / 31 July at 3:15 am AEST / 10:15am 30 July US Pacific Time. pic.twitter.com/FTSgiWKg6FJuly 30, 2022
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There are options to reduce risk.
All objects should have a plan to de-orbit into an unpopulated area. This is usually the South Pacific Ocean Uninhabited Area.
The option to design components so they are completely destroyed upon re-entries is also available. There won't be a significant risk if everything burns up.
The mechanisms for these aren't specified, but there are already some guidelines requiring space debris risk minimization.
How do these guidelines apply outside of the country? Questions are still unanswered.
Should you be worried about being hit by space debris? Is further research important for the future? It's absolutely true.
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