HypervelocityFragmentationexperiments

Priscilla Cerroni

INTERNATIONAL WORKSHOP ON PAOLO FARINELLA (1953-2000):THE SCIENTIST AND THE MAN

Dipartimento di Matematica, Università di Pisa June, 14-16, 2010

Giuseppe Martelli in 1980 came back to Italy to start a program of hypervelocity experiments

At first the experiments were devoted to the study of cratering in basalt blocks

To study em transient phenomena associated to the impact

The experiments were carried out at the proving grounds of the Italian firm SNIA Viscosa in Colleferro using an explosive accelerating technique, the shaped charge

Hypervelocity cratering experiments at SNIA

Shaped charge technique

The Planetology Group in Rome wasinvolved in this project and experimentalcampaigns were carried out in Colleferro

The experimental group would transfer from Sussex to Colleferro with the oldvan, diagnostic instruments, targets and shaped charge liners which were filledwith explosive at SNIA

But Pisa was an important part ofMartelli’s life, and there he met Paolo and the idea of devoting the experiments tosimulating asteroid fragmentation

Hypervelocity cratering experiments at SNIA

Hypervelocity cratering experiments at SNIA

Hypervelocity cratering experiments at SNIA

Shapes of asteroids compared with fragments from hypervelocity impact experiments

F. Capaccioni*, P. Cerroni*, M. Coradini*, P. Farinella†, E. Flamini‡, G. Martelli*, ‡, P. Paolicchi§, P. N. Smith‡ & V. Zappala

*Istituto di Astrofisica Spaziale, Reparto planetologia, Roma, Italy

†Scuola Normale Superiore, Dipartimento Matematico dell'Università Pisa, Italy

‡Space and Plasma Physics Group, University of Sussex, Brighton BN1 9QH, UK

§Osservatorio Astronomico di Brera, Merate, ItalyOsservatorio Astronomico di Torino, Pino Torinese, Italy

Nature 308, 832-834 (26 April 1984)

Light-curve observations have shown that most asteroids are non-axially symmetrical in shape, probably as a result of fragmentation undergone by objects with negligible gravitational binding1.

Some earlier laboratory simulations of catastrophic collisions at velocities not exceeding 4 km s-1 against cubic and parallelepipedal targets showed that the fragment shapes have a nearly gaussian distribution around the mean value of the axes' ratio 2:√2:1.

We report here results from hypervelocity experiments performed at 10 km s-1 against free-falling bodies.

We found that, regardless of the very different experimental conditions, the shape distribution obtained is closely similar to that obtained2–4 using targets of different shapes and materials and in good agreement with that of the main-belt asteroids of diameter smaller than 100 km. This distribution is not consistent with either the symmetrical shapes of the gravity-dominated asteroids, or the elongated Apollo–Amor objects.

Hypervelocity impact experiments: the quarry

Hypervelocity impact experiments: the quarry

Hypervelocity impact experiments: the quarry

Hypervelocity impact experiments: the quarry

Beograd Catastrophic Workshop

Pisa 1985