Hypervelocity impact experiments on aerogel dust collector

Abstract

Abstract. Laboratory hypervelocity impact experiments were conducted to verify the performance of aerogel dust collectors used for gathering meteorolds and space debris in the near-Earth environment and to derive the relationships of various parameters characterizing the projectile with morphology of tracks left by t•he penetrating projectile in the aerogel collector pad. Silica aerogel collectors of 0.03 g/cm -• density were impacted at velocities ranging from 1 to 14 km/s with projectiles of aluminum oxide, olivine, or sodalime glass, with diameters ranging from 10 to 400/xm. At impact velocities below 6 km/s the projectiles were captured without fragmentation by the aerogel collector and, in many instances, without complete ablation even at 12 km/s. The shapes and dimensions of the penetration tracks left in the aerogel collector were correlated with the impact parameters, and the results permitted derivation of a series of equations relating the track dimensions to incoming projectile size, impact energy, and other projectile parameters. A simplified model, similar to meteor-entry phenomena, was used to predict the trends in experimental penetration track lengths and the diameters of captured projectiles. IntroductionSolid particles present in the near-Earth environment derive from either natural or artificial origin and are termed "meteoroids" and "space debris", respectively. Meteoroids are considered to be supplied from comets, asteroids, and planets, and some known as interstellar dust particles or interstellar grains are from outside the solar system [Griin et al., 1993]. Since meteoroids are thought to be closely related with the evolution of the solar system, study of these materials provides us with crucial information on the source materials for the solar system. In situ sampling of meteoroids in space can avoid contamination by terrestrial sources, which is unavoidable in sampling on Earth.Space debris is the product of normal satellite operations, the deterioration of satellites, and the fragmentation or breakup of satellites [Johnson and McKnight, 1991]. It is important to investigate micrometer-to-millimeter-sized debris, the range within which the majority of debris particles lie, because this changes the characteristics of the materials of spacecraft or of the on-board parts after colliding with them. The distribution and composition of small-sized debris are not well known, as these particles are too small to be observed with ground-based telescopes or radars. In situ sampling of dust particles is useful for getting material information on the de- The authors developed a dust collector made from silica aerogel to take the Manipulator Flight Demonstration (MFD) flight opportunity aboard the Space Shuttle (STS-85),

Bulbous tracks arising from hypervelocity capture in aerogel

“…For comparison, the estimated crushing pressure of 20 mg/cc aerogel is shown which is obtained from Equation 18 in Domínguez et al (2004). (17) respectively (Kitazawa et al 1999;Domínguez et al 2004). These expressions, while derived for spherical grains, are adequate representations of the deceleration profiles for irregular objects and are accurate to within a factor of 2.…”

Characteristics of cometary dust tracks in Stardust aerogel and laboratory calibrations

“…At potentially higher, albeit unknown, impact speeds, Hörz et al (2000) also observed similar track morphologies in aerogel exposed on the Mir Space Station. Separately, Kitazawa et al (1999) proposed a scheme for track categorization. For impacts at >4 km s −1 , they found three track types (similar to those here) from impacts into aerogel of density 30 kg m −3 .…”

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

“…In general, the length of impact tracks is observed to be several hundred times the radius (r g ) of the projectile, and scale as r g , where ρ g and ρ 0 are the densities of the captured projectile and aerogel respectively. Several authors have provided theoretical explanations for this scaling as being the result of hydrodynamic-like slowing in aerogel (Westphal et al 1998;Kitazawa et al 1999;Dominguez et al 2004b). The connection between slowing in aerogel and so-called "ideal compressible solids" was made by Dominguez et al (2004) following the work of (Trucano and Grady 1995).…”

“…The direct observation of melting and ablation of spherical Al 2 O 3 projectiles fired into 20 mg/cc aerogel by Hörz et al implies that capture at 6.1 km s -1 produces shock-heated aerogel >2034 °C (Hörz et al 2009). Theoretical calculations on the shock conditions experienced by captured projectile have been presented previously (Anderson and Ahrens 1994;Dominguez et al 2004b;Kitazawa et al 1999) and the amount of shock heating resulting from capture has been found to be small (Trigo-Rodríguez et al 2008). Yet despite their importance and proven utility as a scientific tool, a theoretical understanding of the conditions experienced by particles and fragments during all phases of capture in aerogel is lacking.…”