A supercomputer simulation by LLNL physicist Mike Owen illustrates how a 1 megaton nuclear detonation could impart enough energy onto the surface of the massive asteroid 101955 Bennu to nudge it off course, if it were to be on an Earthbound trajectory. The black dot is the simulated detonation location, around 100 meters from the surface at the equator. The colors show where X-rays would heat a thin layer of surface material. Blue areas would be heated, but not enough to eject material. All other colored areas would deposit enough energy to eject surface material and alter the asteroid’s velocity and trajectory.
Credit: LLNL

 

The first-ever, in-depth investigation into how an asteroid would respond to a nuclear deflection attempt has been completed.

The research was published by Acta Astronautica online Oct. 15 and will appear in print in early 2020.

The focus of the investigation was 101955 Bennu, a massive asteroid that has a remote chance of crossing paths with Earth more than a century from now.

It is the second examination of deflection technologies using Bennu as a test case.

Nuclear impulse

The first Bennu case study found that a kinetic impactor – similar to using a spacecraft as a battering ram – would not be effective at deflecting a Bennu-class asteroid. This second case study, however, found that a standoff nuclear impulse would be effective in deflecting Bennu.

An interagency team of researchers led by Lawrence Livermore National Laboratory (LLNL) completed the appraisal. NASA’s Goddard Space Flight Center, Los Alamos National Laboratory and the National Nuclear Security Administration (NNSA) collaborated on the research.

NASA’s Origins, Spectral Interpretation, Resource Identification, Security-Regolith Explorer (OSIRIS-REx) spacecraft.
Credit: NASA/Goddard/University of Arizona

Research highlights

If space rock Bennu sounds familiar, it should – it is now being investigated by NASA’s Origins, Spectral Interpretation, Resource Identification, Security-Regolith Explorer (OSIRIS-REx) spacecraft.

Highlights of the new research:

— Asteroid Bennu can be successfully deflected by extant nuclear devices.

— Kinetic impact, even with large momentum enhancement, is unlikely to deflect  Bennu.

— Nuclear deflection efficacy depends upon the x-ray source spectrum.

— Nuclear deflection efficacy is enhanced by near-surface, unbound volatiles.

Final option

“The nuclear option would be the key to deflecting large asteroids,” said Dave Dearborn, an LLNL physicist and lead author on the paper. “It also offers flexibility that impactors don’t. For instance, the amount of energy deposited into an asteroid with a nuclear device can be tuned by adjusting how far it is from the asteroid when detonated,” he said in a LLNL press statement.

As explained in the research paper, though rare, asteroid impacts are inevitable, and with the current state of technology, kinetic impactors are the preferred but not the complete solution. If the time to impact is short, or the threatening body too large, nuclear deflection serves as a final option.

To view the new paper – “Options and uncertainties in planetary defense: Impulse-dependent response and the physical properties of asteroids” – go to:

https://www.sciencedirect.com/science/article/abs/pii/S0094576519313323

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