Subsurface momentum coupling analysis for near-earth-object orbital management

• Published in: Acta astronautica 1995, Vol.35 (1), p.27-33
• Main Authors: Remo, J.L., Sforza, P.M.
• Format: Article
• Language: English
• ISSN: 0094-5765; 1879-2030
• DOI: 10.1016/0094-5765(94)00130-E

Momentum coupling methods are analyzed for near-Earth object (NEO) orbit modification that can use either conventional explosives (HE) or nuclear explosives (NE) effectively. Enhancing momentum coupling reduces the explosive yield needed to achieve a particular orbital alteration, which, in turn, reduces the number of launch vehicles needed while also eliminating (for the HE case) or minimizing radioactive contamination and associated problems. A disadvantage is the additional mass required for the penetrator payload used to bury the explosive in the initial NEO interaction. In computing the momentum coupling necessary to provide reliable estimates of momentum coupling for various target materials (asteroids and comets) three analytic methods are presented for determining the position and yield of buried explosives that can produce a given NEO velocity change, Δ V The first method makes use of experimental data on crater ejecta characteristics and relates the momentum of the ejected mass to the yield and placement of the explosive. Ejecta velocities are strongly dependent on target density and scale depth. The second method is based on kinetic energy transfer and determines the change in NEO kinetic energy based on the energy partition from HE or NE detonations. Computational results from this method depend on NEO material properties such as the equation-of-state and mechanical structure. The third method relies on impulse momentum transfer and analyzes the impulsive force generated by the shock and ejecta formation process. Conditions behind the explosively generated shock are exploited to produce accurate computations yielding results comparable to those of the first two methods. Computational results for all three methods are presented to estimate the energy requirement needed to produce in a given NEO the velocity increment Δ V as a function of asteroid density, radius, ejecta velocity, and explosive depth. All three analytical methods yield consistent numerical results over the range of parameters selected, which includes asteroids with radii from 0.01 to 1 km, densities from 2.2 to 8 g/cm 3, and explosive yields from 0.01 to 10 4kt of TNT. These energy requirements are considerably less than those required to obtain the equivalent Δ V from stand-off NE devices and, in some cases, eliminate the need for NE entirely.