LIVERMORE (CBS SF) — It sounds like a scene from a Hollywood sci-fi thriller, but researchers from Lawrence Livermore National lab have joined with an Air Force team of technologists to test if a nuclear blast could be used to deflect an earth-threatening asteroid.
Whether it be Bruce Willis and his crew of oil drillers taking on an asteroid as it approaches earth in ‘Armageddon’ or Tia Leoni and her father awaiting a massive tidal wave from an asteroid strike in ‘Deep Impact,’ Hollywood has been fascinated by the threat from space.
Lansing Horan IV, a member of the team, said the research was focused on the neutron radiation from a nuclear detonation since neutrons can be more penetrative than X-rays.
“This means that a neutron yield can potentially heat greater amounts of asteroid surface material, and therefore be more effective for deflecting asteroids than an X-ray yield,” he said.
Horan said there are two basic options in defeating an asteroid: disruption or deflection.
Disruption is the approach of imparting so much energy to the asteroid that it is robustly shattered into many fragments moving at extreme speeds.
“Past work found that more than 99.5 percent of the original asteroid’s mass would miss the Earth,” he said. “This disruption path would likely be considered if the warning time before an asteroid impact is short and/or the asteroid is relatively small.”
Deflection is the gentler approach that involves imparting a smaller amount of energy to the asteroid, keeping the object intact, and pushing it onto a slightly different orbit with a slightly changed speed.
“Over time, with many years prior to impact, even a minuscule velocity change could add up to an Earth-missing distance,” Horan said. “Deflection might generally be preferred as the safer and more ‘elegant’ option, if we have sufficient warning time to enact this sort of response. This is why our work focused on deflection.”
Horan said the work was one small step forward for nuclear deflection simulations.
“One ultimate goal would be to determine the optimal neutron energy spectrum, the spread of neutron energy outputs that deposit their energies in the most ideal way to maximize the resulting velocity change or deflection,” he said.
Horan said the research showed that precision and accuracy in the energy deposition data is important.
“If the energy deposition input is incorrect, we should not have much confidence in the asteroid deflection output,” he said. “We now know that the energy deposition profile is most important for large yields that would be used to deflect large asteroids.”
He said if there were to be a plan to mitigate a large incoming asteroid, the energy deposition spatial profile should be accounted for to correctly model the expected asteroid velocity change.
“On the other hand, the energy coupling efficiency is always important to consider, even for low yields against small asteroids,” he said. “We found that the energy deposition magnitude is the factor that most strongly predicts the overall asteroid deflection, influencing the final velocity change more than the spatial distribution does.”
For planning an asteroid mitigation mission, it will be necessary to account for these energy parameters in order to have correct simulations and expectations.
“It is important that we further research and understand all asteroid mitigation technologies in order to maximize the tools in our toolkit,” Horan said. “In certain scenarios, using a nuclear device to deflect an asteroid would come with several advantages over non-nuclear alternatives. In fact, if the warning time is short and/or the incident asteroid is large, a nuclear explosive might be our only practical option for deflection and/or disruption.”