Neutron Energy Effects on Asteroid Deflection
Technical Report,01 Oct 2018,01 Mar 2020
AIR FORCE INSTITUTE OF TECHNOLOGY WRIGHT-PATTERSON AFB OH WRIGHT-PATTERSON AFB United States
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In the future, a hazardous asteroid will nd itself on a collision course with Earth. It is an inevitability the question is not if, but when. For asteroids of moderate size or larger, a nuclear device is one of humanitys only technologies capable of mitigating this threat via deflection on a timescale of less than a decade. This work examined how changing the output neutron energy from a nuclear device detonation affects asteroid deflection. The notional asteroid target was 300 meters in diameter and composed of silicon dioxide at 1.855 gcm3.To calculate the energy deposition in the asteroid that results from a neutron source, the Monte Carlo radiation-transport code, MCNP6.2, was applied. MCNP6.2 simulations were performed for neutrons of various energies radiating towards the asteroid surface. The neutron energy was found to have an impact in terms of 1 the spatial distribution of energy deposition, and 2 the energy coupling efficiency. To model the mechanical response of the asteroid due to a spatially-varying energy deposition, the hydrodynamics code, ALE3D, was employed. The energy deposition outputs from MCNP6.2 served as inputs into the model representation of the asteroid in ALE3D. The momentum impulse imparted onto the asteroid body due to rapidly-evolving melted andor vaporized blow-o ejecta was quantified. From this, the asteroid velocity change, or V , was determined for two different neutron yields 50 kt and 1 Mt and for two different source neutron energies 14.1 MeV from fusion and 1 MeV from fission. Underexplored in literature, the distribution of deposited energy and the energy coupling were both found to affect the asteroid deflection. The magnitude of energy deposition, as determined by the neutron energy and the coupling, generally appears to be the more significant factor.
- Nuclear Physics and Elementary Particle Physics