Engineering topics

Farinella, Paolo

Publications and source records attributed to Farinella, Paolo.

7 records

NASA NTRS1992

Collision rates and impact velocities in the Main Asteroid Belt

Wetherill's (1967) algorithm is presently used to compute the mutual collision probabilities and impact velocities of a set of 682 asteroids with large-than-50-km radius representative of a bias-free sample of asteroid orbits. While collision probabilities are nearly independent of eccentricities, a significant decrease is associated with larger inclinations. Collisional velocities grow steeply with orbital eccentricity and inclination, but with curiously small variation across the asteroid belt. Family asteroids are noted to undergo collisions with other family members 2-3 times more often than with nonmembers.

Farinella, Paolo↗

NASA NTRS1992

Lifetime of binary asteroids versus gravitational encounters and collisions

We investigate the effect on the dynamics of a binary asteroid in the case of a near encounter with a third body. The dynamics of the binary is modeled as a two-body problem perturbed by an approaching body in the following ways: near encounters and collisions with a component of the system. In each case, the typical value of the two-body energy variation is estimated, and a random walk for the cumulative effect is assumed. Results are applied to some binary asteroid candidates. The main conclusion is that the collisional disruption is the dominant effect, giving lifetimes comparable to or larger than the age of the solar system.

Chauvineau, Bertrand↗

NASA NTRS1992

From asteroid clusters to families: A proposal for a new nomenclature

Some confusion on the number, reliability, and characteristics of asteroid families is the result of using the single word 'family' for naming asteroid groupings identified in very different ways. Here we propose a new terminology which in our opinion would alleviate this problem.

Farinella, Paolo↗

NASA NTRS1992

Injecting asteroid fragments into resonances

We have quantitatively modeled the chance insertion of asteroid collisional fragments into the 3:1 and g = g(sub 6) resonances, through which they can achieve Earth-approaching orbits. Although the results depend on some poorly known parameters, they indicate that most meteorites and near-earth asteroids probably come from a small and non-representative sample of asteroids, located in the neighborhood of the two resonances.

Farinella, Paolo↗

NASA NTRS1992

A comparison between families obtained from different proper elements

Using the hierarchical method of family identification developed by Zappala et al., the results coming from the data set of proper elements computed by Williams (about 2100 numbered + about 1200 PLS 2 asteroids) and by Milani and Knezevic (5.7 version, about 4200 asteroids) are compared. Apart from some expected discrepancies due to the different data sets and/or low accuracy of proper elements computed in peculiar dynamical zones, a good agreement was found in several cases. It follows that these high reliability families represent a sample which can be considered independent on the methods used for their proper elements computation. Therefore, they should be considered as the best candidates for detailed physical studies.

Zappala, Vincenzo↗

NASA NTRS1989

Asteroid rotation rates - Distributions and statistics

An analysis of asteroid rotation rates and light-curve amplitudes disclosed many significant correlations between these rotation parameters and asteroid diameter, with distinct changes occurring near 125 km, a diameter above which self-gravity may become important. It is suggested that this size range may represent a division between surviving primordial asteroids and collisional fragments. A comparison of rotational parameters between family and nonfamily asteroids showed that the Koronis and Eos families exhibit noticeable differences, considered to be due to different impact conditions and/or to a relatively younger age for the Koronis family.

Binzel, Richard P.↗

NASA NTRS1989

Asteroid collisional history - Effects on sizes and spins

The effects of asteroid collisional history on sizes and spins of present-day objects are discussed. Collisional evolution studies indicate that collisions have altered the spin-rates of small bodies, but that the largest asteroids may have retained their primordial rotation rates. Most asteroids larger than 100 km diam have probably been shattered, but have gravitationally recaptured their fragments to form a rubble-pile structure. Large angular momentum asteroids appear to have Maclaurian spheroidal or Jacobi-ellipsoid-like shapes; some of them may have fissioned into binaries. An integrated size and spin collisional evolution model is presented, with two critical parameters: one which determines the spin rates for small fragments resulting from a shattering collision, and the other determines the fraction of impact angular momentum that is retained by the target.

Davis, Donald R.↗