Momentum Coupling to NEOs

Annals of the New York Academy of Sciences

2004

Section: Uncertainties In Using CMmentioning

confidence: 92%

Section: The Hazard Awareness Level and Hazard Mitigation Energymentioning

confidence: 99%

Section: Uncertainties In Using CMmentioning

confidence: 99%

See 1 more Smart Citation

A Dynamic Metric for NEO Hazard Mitigation

Annals of the New York Academy of Sciences

2004

“…Generally speaking, to achieve a NEO threat reduction to Earth an amount of energy Δ E payload must be expended to change (perturb) the threatening NEO velocity by Δ V NEO ; that is, to deflect the NEO. The relationship8,10,11 may be written where M is the NEO mass and C (sec/m) is the so‐called momentum coupling coefficient, which depends on NEO material properties,21–24 that must be empirically determined for a range of targets, power, and interaction mechanisms 25. Delivery of the Δ V NEO can be carried out as a high energy density (power) interaction, where the momentum M Δ V NEO is impulsively coupled at the beginning of the mitigation operation or coupled slowly over a longer period of time.…”

Section: Neo Interception and Mitigation Mission Energy Requirementsmentioning

confidence: 99%

Assessing NEO Hazard Mitigation in Terms of Astrodynamics and Propulsion Systems Requirements

Annals of the New York Academy of Sciences

2004

Uncertainties associated with assessing valid near-Earth object (NEO) threats and carrying out interception missions place unique and stringent burdens on designing mission architecture, astrodynamics, and spacecraft propulsion systems. A prime uncertainty is associated with the meaning of NEO orbit predictability regarding Earth impact. Analyses of past NEO orbits and impact probabilities indicate uncertainties in determining if a projected NEO threat will actually materialize within a given time frame. Other uncertainties regard estimated mass, composition, and structural integrity of the NEO body. At issue is if one can reliably estimate a NEO threat and its magnitude. Parameters that determine NEO deflection requirements within various time frames, including the terminal orbital pass before impact, and necessary energy payloads, are quantitatively discussed. Propulsion system requirements for extending space capabilities to rapidly interact with NEOs at ranges of up to about 1 AU (astronomical unit) from Earth are outlined. Such missions, without gravitational boosts, are deemed critical for a practical and effective response to mitigation. If an impact threat is confirmed on an immediate orbital pass, the option for interactive reconnaissance, and interception, and subsequent NEO orbit deflection must be promptly carried out. There also must be an option to abort the mitigation mission if the NEO is subsequently found not to be Earth threatening. These options require optimal decision latitude and operational possibilities for NEO threat removal while minimizing alarm. Acting too far in advance of the projected impact could induce perturbations that ultimately exacerbate the threat. Given the dilemmas, uncertainties, and limited options associated with timely NEO mitigation within a decision making framework, currently available propulsion technologies that appear most viable to carry out a NEO interception/mitigation mission within the greatest margin of control and reliability are those based on a combined (bimodal) nuclear thermal/nuclear electric propulsion platform. Elements of required and currently available performance characteristics for nuclear and electric propulsion systems are also discussed.

“…Surprisingly, the C M concept has not been well developed even though it is helpful for HED planetary, astronomical, and astrodynamic phenomena (inelastic) collisions where dissipative radiative and mechanical energy processes dominate. Up till recent work 4,8 applying C M to near-Earth object hazard mitigation was primarily relegated to the nuclear weapons testing community. We now apply the C M concept to HED physics, astrophysics and planetary science.…”

Section: Introductionmentioning

confidence: 99%

Laser radiation plasma dynamics and momentum coupling

High-Power Laser Ablation VII

2008

The concept of high energy density (HED) radiation driven momentum coupling (momentum transfer), C M , to a targets in a vacuum is analytically developed and applied via successive plasma, ablative, and hydrodynamic interfaces undergoing both weak and strong shocks. C M are derived from equations of state (EOS) variables and serve as figures of merit to determine energy efficiency conversion into target momentum. Generally, C M are proportional to the inverse of the interaction speed and related variables for each interaction regime. This approach provides a formalism allowing computation of hitherto intractable HED radiation and mechanical momentum coupling interactions encountered in astrophysics, planetary physics, inertial confinement fusion, near-Earth object hazard mitigation, and HED explosives modeling. C M is generally not scale invariant as are the hydrodynamic Euler equations. This analytic procedure supports interpretation of experiments using EOS response of material targets to HED interactions on the meso -and macro-scales to describe C M . IntroductionMomentum transfer and associated equations of state (EOS) derived from high energy density (HED) interactions encountered in astrophysics and planetary physics may profoundly affect astrodynamic and geochemical outcomes in terms of momentum coupling, zone vaporization and melting, and turbulent mixing and species migration via Richtmyer-Meshkov (R-M) and Rayleigh-Taylor (R-T) instabilities 1 . By HED is meant an energy density more than an order of magnitude greater than required to vaporize and eject matter from a target at a velocity sufficient to impart a substantial momentum transfer to the remaining target mass. The dynamics analyzed in this research is that of HED laser radiation generating a high temperature and pressure plasma on a target surface in a vacuum. While (mechanical) astrodynamic collision processes are driven by gravitational interactions at planetary velocities (10's km/s), the interface energy densities are so large that transonic interaction interface conditions using conservation equations must be carried out in plasma, ablative, and hydrodynamic shock wave (discontinuity) regions that are similar to those used by the internal confinement fusion (ICF) and nuclear explosives (NE) communities. A radiation driven process on a given target (material) establishes a HED interactive region characterized by a specific momentum coupling coefficient (C M ) that determines the mechanical momentum transfer between a plasma region and the solid target. C M is not a constant or linear scale invariant within a specific material with non-zero density, but is a derived and parametrically (inverse interaction velocity, i. e. plasma isothermal sound speed) dependent figure of merit originally intended to interpret HED momentum coupling from NE tests.An objective of this work is to extend the application of C M and associated thermodynamic processes to laboratory astrophysical, planetary, and ICF problems in order to estimate the momentum exchange...