New technique may help divert Earth-bound asteroids

A new approach that uses a spacecraft to crash at high speeds into an asteroid headed for a collision with the Earth may prevent the potentially devastating consequences of an impact, scientists say.
Asteroids headed for Earth, if found early enough, can be acted upon to prevent the impact, researchers said.
One technique to divert an asteroid, called kinetic impact, uses a spacecraft to crash into the body at high speeds, they said.
This approach delivers the momentum of the spacecraft, while also providing an additional boost of momentum through the production of impact crater ejecta exceeding the asteroid's escape velocity.

Researchers at Lawrence Livermore National Laboratory (LLNL) have been studying the effectiveness of the kinetic-impactor strategy by carrying out 3D simulations of the process.
They have found that asteroid deflection by kinetic impact is sensitive to a range of asteroid characteristics, including strength, porosity, rotation and shape.

These and other asteroid properties may not be well constrained before an actual deflection mission is staged, leading to variability in the deflection outcome.
By simulating a range of initial conditions for the target asteroids, researchers were able to quantify, for example, how greater target strength decreases the delivered momentum impulse and how, for an asteroid of constant size, added porosity can result in more effective deflections, despite the dampening of the shock waves produced during an impact.

In this model, asteroid Golevka (approximately 500 meters across) is impacted by a 10,000 kilogramme mass travelling at 10 kilometres per second along a principal axis of the asteroid.
The final change in asteroid velocity for this example is approximately one millimetre per second.
The kinetic-impact approach is one of the most mature technologies for deflecting a hazardous asteroid, researchers said.
For cases where the warning time is known well in advance and the asteroid is not too large, it is the preferred deflection mechanism, they said.
"Asteroids are naturally diverse, and researchers have little direct information about their mechanical properties," said Megan Bruck Syal, lead author on the paper published in the journal Icarus.

"This study emphasises the important role of asteroid characterisation research, which is needed to constrain the different types of conditions that could be encountered at potential deflection targets," said Syal.