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Series solution to describe hydrodynamic phase flow field during hypervelocity impact of compressible penetrating particle into ideal fluid - Hugoniot equation of state
Three-dimensional numerical simulations of the impact of Comet Shoemaker - Levy 9 on Jupiter and the resulting vapor plume expansion were conducted using the Smoothed Particle Hydrodynamics (SPH) method. An icy body with a diameter of 2 km can penetrate to an altitude of -350 km (0 km = 1 bar) and most of the incident kinetic energy is transferred to the atmosphere between -100 km to -250 km. This energy is converted to potential energy of the resulting gas plume. The unconfined plume expands vertically and has a peak radiative power approximately equal to the total radiation from Jupiter's disk. The plume rises a few tens of atmospheric scale heights in approximately 10(exp 2) seconds. The rising plume reaches the altitude of approximately 3000 km, but no atmospheric gas is accelerated to the escape velocity (approximately 60 km/s).
We have employed three-dimensional numerical simulations of the impact of Comet Shoemaker-Levy 9 (SL9) on Jupiter and the resulting vapor plume expansion using the smoothed particle hydrodynamics (SPH) method. An icy body with a diameter of 2 km can penetrate to an altitude of -350 km (0 km = 1 bar) and most of the incident kinetic energy is transferred to the atmosphere between -100 to -250 km. This energy is converted to potential energy of the resulting gas plume. The unconfined plume expands vertically and has a peak radiative power approximately equal to the total radiation from Jupiter's disc. The plume rises a few tens of atmospheric scale heights in approximately 10(exp 2) seconds. The rising plume reaches the altitude of approximately 3000 km; however, no atmospheric gas is accelerated to the escape velocity (approximately 60 km/s).
Interplanetary spacecraft are exposed to meteoroid fluxes that range in speeds from 10 to 72 km/sec, far above the capability of today’s test facilities to provide predictions for the likelihood of spacecraft critical penetration. Of special interest are sample return missions, which (though protected by shielding) must often survive years of exposure to the meteoroid environment in order to re-enter Earth’s atmosphere with their scientific cargo. This paper describes the simulation of meteoric material damage to thermal protection systems (TPS) housed beneath protective “garage” (shielding) enclosures using the Smooth Particle Hydrodynamics Code (SPHC) operated by the Institute for Defense Analyses and Stellingwerf Consulting in support of ongoing NASA tasks. The study outlined in this paper considered the impact effect of both meteoric materials such as iron, ice, and chondrites (dunnite), and non-meteoric materials such as aluminum and nylon against both external shielding materials (single and dual aluminum bumpers) and Heat shield for Extreme Entry Environments Technology (HEEET) TPS materials, used alone and in conjunction with shielding. A general predictive damage equation to HEEET TPS is developed from these SPHC simulations for velocities up to 70 km/sec.
Interplanetary spacecraft are exposed to meteoroid fluxes with characteristics far exceeding the physical simulation capabilities of test facilities for predicting the likelihood that a meteoroid will penetrate a spacecraft’s critical systems. Accurate risk predictions are crucial to ensuring that important interplanetary missions, such as sample returns, can survive years of exposure to the meteoroid environment and safely reenter the Earth’s atmosphere with their scientific cargo. In this paper, we summarize a series of meteoroid impact damage computational simulations into two types of spacecraft composite protective structures using the Smooth Particle Hydrodynamics Code. We consider the effects of both meteoric materials and non-meteoric materials on a shielded forebody thermal protection system (TPS) for an extreme entry environment and on an unshielded aftbody TPS that is similar to the material covering the space shuttle’s external tank.
The SPHC hydrodynamic code was used to evaluate the effects of orbital debris particle shape and orientation on penetration of a typical spacecraft dual-wall shield. Impacts were simulated at near-normal obliquity at 12 km/sec. Debris cloud characteristics and damage potential are compared with those from impacts by spherical projectiles. Results of these simulations indicate the uncertainties in the predicted ballistic limits due to modeling uncertainty and to uncertainty in the impactor orientation.
The impact of fragments of Comet Shoemaker-Levy 9 on Jupiter and the resulting vapor plume expansion are investigated by conducting three-dimensional numerical simulations using the smoothed particle hydrodynamics (SPH) method. An icy body, representing the cometary fragments, with a velocity of 60 km/sec and a diameter of 2 km can penetrate to 350 km below the 1-bar pressure level in the atmosphere. Most of the initial kinetic energy of the fragment is transferred to the atmosphere between 50 km and 300 km below the 1-bar pressure level. The shock-heated atmospheric gas in the wake is totally dissociated and partially ionized. Scaling our SPH results to other sizes indicates that fragments larger than approximately 100 m in diameter can penetrate to below the visible cloud decks. The energy deposited in the atmosphere is explosively released in the upward expansion of the resulting plume. The plume preferentially expands upward rather than horizontally due to the density gradient of the ambient atmosphere. It rises greater than or equal to 10(exp 2) km in approximately 10(exp 2) sec. Eventually the total atmospheric mass ejected to above 1 bar is greater than or equal to 40 times the initial mass of the impactor. The plume temperature at a radius approximately 10(exp 3) km is greater than 10(exp 3) K for 10(exp 3) sec for a 2-km fragment. We predict that impact-induced plumes will be observable with the remote sensing instruments of the Galileo spacecraft. As the impact site rotates into the view of Earth some 20 min after the impact, the plume expansion will be observable using the Hubble Space Telescope (HST) and from visible and infrared instruments on groundbased telescopes. The rising plume reaches approximately 3000 km altitude in approximately 10 min and will be visible from Earth.
Hydrodynamic and semi-kinetic treatments of plasma flow along closed geomagnetic field lines are compared. The hydrodynamic treatment is based on a simplified 16-moment set of transport equations as the equations for the heat flows are not solved; the heat flows are treated heuristically. The semi-kinetic treatment is based on a particle code. The comparison deals with the distributions of the plasma density, flow velocity, and parallel and perpendicular temperatures as obtained from the two treatments during the various stages of the flow. In the kinetic treatment, the appropriate boundary condition is the prescription of the velocity distribution functions for the particles entering the flux tubes at the ionospheric boundaries; those particles leaving the system are determined by the processes occurring in the flux tube. The prescribed distributions are half-Maxwellian with temperature T(sub 0) and density n(sub 0). In the hydrodynamic model, the prescribed boundary conditions are on density (n(sub 0)), flow velocity (V(sub 0)) and temperature (T(sub 0). It was found that results from the hydrodynamic treatment critically depend on V(sub 0); for early stages of the flow this treatment yields results in good agreement with those from the kinetic treatment, when V(sub 0) = square root of (kT(sub 0)/2 (pi)m), which is the average velocity of particles moving in a given direction for a Maxwellian distribution. During this early stage, the flows developing form the conjugate ionospheres show some distinct transitions. For the first hour or so, the flows are highly supersonic and penetrate deep into the opposite hemispheres, and both hydrodynamics and kinetic treatments yield almost similar features. It is found that during this period heatflow effects are negligibly small. When a flow penetrates deep into the opposite hemisphere, the kinetic treatment predicts reflection and setting up of counterstreaming. In contrast, the hydrodynamic treatment yields a shock in the flow. The reasons for this difference in the two treatments is discussed, showing that in view of the relatively warm ions, the coupling of ion beams and the consequent shock formation in the offequatorial region are not likely due to the enhancements in the beam temperatures. The counterstreaming in the kinetic treatment and the shock in the hydrodynamic treatment first advance upward to the equator and then downward to the ionospheric boundary from where the flow originated. The transit time for this advancement is found to be about 1 hour for the respective models. After 2 hours or so, both models predict that the flows from the ionospheric boundaries are generally subsonic with respect to the local ion-sound speed. At late stages of the flow, when a substantial fraction of ions entering the flux tube begin to return back in the kinetic treatment, the hydrodynamic treatment with the boundary condition V(sub 0) = square root of (kT(sub 0)/2(pi)m) yields an over-refilling, and the choice of V(sub 0) becomes uncertain.
This paper presents results from an analysis to assess the fluence of meteoroids on the Mars Sample Return Campaign Micrometeoroid Protection System (MMPS) and probability of damage to the Earth Entry System Thermal Protection System (TPS). Results are presented for the mission Outbound trajectory from Earth to Mars. The MEM3 meteoroid environment model was used for the assessment. Results are presented showing the reduction in fluence on cube faces and on the MMPS that can be achieved by selection of an anti-velocity orientation of the MMPS. A methodology is presented that determines the cumulative fluence on the MMPS using the MEM3 meteoroid fluxes and the spacecraft attitude profile over the trajectory. Resulting distributions of fluence over impact velocity, angle, and mass are presented. The fluence results are used to establish velocity-angle scenarios for hydrocode simulation and to assess net damage fluence to the TPS. Example tables containing Smooth Particle Hydrodynamics Code (SPHC) simulation scenarios as well as hypothetical hydrocode simulation scenarios for illustration purposes are presented. The tables present the resulting net damaging fluence to the TPS for each scenario and the total across the scenarios. Additionally, examples of CTH hydrocode simulation are included, demonstrating their use for determining critical impactor across the impactor parameter space, and damage of impactors that penetrate the MMPS.
The modulation of galactic cosmic rays and other energetic particles by the solar wind produces a gradient in their pressure, which in turn influences the wind dynamics. The basic equations describing this interaction are presented in the 'hydrodynamic' approximation. A perturbation solution of the equations is presented for the case in which both the galactic cosmic ray pressure, and the pressure of the anomalous cosmic ray component accelerated at the wind termination shock, are small compared with the wind ram pressure. Analytical expressions for the deceleration of the wind and the modification of the shock and its location are derived in this case. These effects are estimated to have a relative magnitude of several percent in the solar wind. The interstellar neutral gas which penetrates the heliosphere is ionized, predominantly by photoionization and charge exchange with the wind, and may also have a significant dynamical effect on the wind. The basic equations describing this interaction are also presented, A perturbation solution is presented under the assumption that the mass loading and momentum-loading of the wind by the interstellar pickup ions is small compared with the wind ram pressure. Analytical expressions for the deceleration of the wind, the contribution of the pickup ions to the wind pressure, and the modification of the termination shock location are derived. Again, with the exception of pickup ion pressure which is large compared with solar wind thermal pressure, the effects are estimated to be several percent in relative magnitude in the solar wind.