#### Document Type

Article

#### Publication Date

10-2014

#### Department

Department of Physics and Computer Science

#### Abstract

Fractals are defined as geometric shapes that exhibit symmetry of scale. This simply implies that fractal is a shape that it would still look the same even if somebody could zoom in on one of its parts an infinite number of times. This property is also called self-similarity with several applications including nano-pharmacology and drug nanocarriers. We are interested in the study of the properties of fractal aggregates in a microgravity environment above an orbiting spacecraft. To model the effect we use a complete expression for the gravitational acceleration. In particular on the surface of the Earth the acceleration is corrected for the effect of oblateness and rotation. In the gravitational acceleration the effect of oblateness can be modeled with the inclusion of a term that contains the J_{2} harmonic coefficient, as well as a term that depends on the square of angular velocity of the Earth. In orbit the acceleration of gravity at the point of the spacecraft is a function of the orbital elements and includes only in our case the J_{2} harmonic since no Coriolis force is felt by the spacecraft. Using the fitting parameter *d* = 3.0 we have found that the aggregate monomer number *N* is not significantly affected and exhibits a minute 0.0001% difference between the geocentric and areocentric latitudes of 90° and 0°. Finally for circular and elliptical orbits around Earth and Mars of various inclinations and eccentricities the aggregate monomer number it’s not affected at all at the orbital altitude of 300 km.

#### Recommended Citation

Haranas, I., Gkigkitzis, I., Alexiou, A. Fractal Growth on the Surface of a Planet and in Orbit around it. Microgravity Sci. Technol. (2014) 26:313–325. DOI: 10.1007/s12217-014-9397-6

## Comments

This is a post-peer-review, pre-copyedit version of an article published in

Microgravity Science and Technology. The final authenticated version is available online at: http://dx.doi.org/10.1007/s12217-014-9397-6.