Time evolution and temperatures of hypervelocity impact‐generated tracks in aerogel

Abstract

available online at http://meteoritics.org Time evolution and temperatures of hypervelocity impact-generated tracks in aerogelGerardo DOMINGUEZ Here, a general model of track formation that allows for the existence of partially and completely vaporized aerogel material in tracks is developed. It is shown that under certain conditions, this general track model reduces to the kinetic "snowplow" model that has previously been proposed. It is also shown, based on energetic considerations, that track formation is dominated by an expansion that is snowplow-like in the later stages of track formation. The equation of motion for this snowplow-like stage can be solved analytically, thus placing constraints on the amount of heating experienced by cometary dust fragments embedded in track walls. It is found that the heating of these fragments, for a given impact velocity, is expected to be greater for those embedded in larger tracks. Given the expected future use of aerogels for sample return missions, the results presented here imply that the choice of aerogel compositions can have a significant effect on the modification of samples captured and retrieved by these collectors.

Penetration into low-density media: In situ observation of penetration process of various projectiles

“…This enlargement of the entrance hole probably occurs due to thermal effects. Thus, though in this paper the energy partitioning is not considered, thermal effects play probably important roles in track-formation process particularly near the entrance even for silica aerogel targets, as suggested by Domínguez (2009). The detailed observation of light emission around the impact point would provide important information on the energy partitioning.…”

“…3a) is probably caused by this high temperature). Hence, the thermal effects due to such high temperature may play important roles in track formation process as indicated by Domínguez (2009). In fact, the entrance diameter is often 2-3 times R p even for aerogel targets.…”

“…Various excavation mechanisms have been considered by several authors such as shock waves (Domín-guez et al, 2004;Coulson, 2009b;Iida et al, 2010), fragmentation of projectiles (Kadono, 1999;Kadono and Fujiwara, 2005;TrigoRodríguez et al, 2008), and thermal effects (Kadono, 1999;TrigoRodríguez et al, 2008;Domínguez, 2009;Coulson, 2009b). In this paper, we focus on the roles of shock waves to reproduce the feature about the track shape, particularly the characteristic common feature of any track that the track diameter is small at the entrance, and then becomes the maximum.…”

“…Several models have been proposed on the penetration depth (e.g., Anderson and Ahrens, 1994;Trucano and Grady, 1995;Westphal et al, 1998;Kadono, 1999;Domínguez et al, 2004;Kadono and Fujiwara, 2005;Trigo-Rodríguez et al, 2008;Domínguez, 2009;Coulson, 2009a,b;Niimi et al, 2011). Most models suggest that projectiles receive the hydrodynamic force (C d /2)q t v 2 S, where v 0 , then at a critical v 0 , the breakup of projectiles occurs, and, as v 0 increases, the largest fragment becomes smaller and L/D p decreases).…”

“…Most models suggest that projectiles receive the hydrodynamic force (C d /2)q t v 2 S, where v 0 , then at a critical v 0 , the breakup of projectiles occurs, and, as v 0 increases, the largest fragment becomes smaller and L/D p decreases). On the other hand, there are a relatively small number of researches on the growth of track diameter (Westphal et al, 1998;Kadono, 1999;Domínguez et al, 2004;Trigo-Rodríguez et al, 2008;Coulson, 2009b;Domínguez, 2009). As the mechanisms of the expansion of the track diameter, shock waves (Domínguez et al, 2004), thermal effects (Kadono, 1999;Coulson, 2009b;Domínguez, 2009), and fragmentation of projectiles (Kadono, 1999;Trigo-Rodríguez et al, 2008) have been considered.…”