China plans mass rocket launch to divert asteroid that could wipe out life on Earth

The 78 billion kilogram Bennu has a 1-in-2700 chance of hitting the Earth

Adam Smith
Tuesday 20 July 2021 08:14 BST
Nasa spacecraft arrives at asteroid Bennu
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Chinese researchers want to send more than 20 rockets from the country to practise diverting asteroids away from Earth.

Scientists at China’s National Space Science Centre found in simulations that 23 Long March 5 rockets, which weigh 900 tonnes when they leave the planet, hitting simultaneously could divert an asteroid from its original path by nearly 9,000 kilometres – 1.4 times the Earth’s radius.

The Long March 5B rocket was also the type that was infamously left free-falling by China in May this year, traveling around the world every 90 minutes – too fast for space agencies to tell where it is going to land. Fortunately, it disintegrated over the Indian Ocean.

The probability of an asteroid colliding with Earth is low but one, the 78 billion kilogram Bennu, has been targeted for investigation.

Bennu is classified as a B-type asteroid, which means it contains a lot of carbon along with various other minerals, formed over 4.5 billion years ago. As a primordial artefact that has been preserved by the vacuum of space, the asteroid could contain molecules that developed when life was first evolving on Earth. It might also, ironically, be the end of life on Earth.

Between 2175 and 2199, Bennu will come within 7.5 million kilometres of Earth’s orbit and will be classified as potentially hazardous. Although the chance that Bennu will impact Earth is only 1-in-2700, that risk is still enough to concern scientists due to the amount of destruction the asteroid could cause.

A huge amount of kinetic energy would be needed in order to divert the asteroid, but nuclear power risks breaking an asteroid like Bennu apart into chunks that could still hit the Earth. This makes sending multiple rockets, which would have to travel for three years before reaching their target, a more practical option.

“[It is] possible to defend against large asteroids with a nuclear-free technique within 10 years,” said researcher Li Mingtao, quoted in the South China Morning Post.

Fuel that is not used during the rocket launch could give extra thrust, as well as increasing the total mass of the rocket – making deflection more efficient. The researchers suggest that existing rockets would only require a few minor modifications, such as adding thrusters, to be ready for the mission.

The United States is planning a similar endeavour called HAMMER (Hypervelocity Asteroid Mitigation Mission for Emergency Response), which would send more material - 400 tonnes of rocket material - to Bennu; it would also make the trip faster, only taking two years to reach the asteroid.

However, that plan is more expensive, and would take longer to prepare. The United States would need to discover the asteroid 25 years before a potential collision, while the Chinese plan would only need a decade’s warning.

Nasa also sent a spacecraft chasing after Bennu in order to collect samples from the asteroid. Osiris-Rex hovered above the asteroid before its three meter-long arm descended and collects loose particles from the rock.

Nasa expects Osiris-Rex to return to Earth, with its samples, in 2023.

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