Radio Waves for Space-Based Construction

This paper follows up on the idea of using potential fields for automatic construction of massive objects of desired shape in Space. In STAIF03, we showed the commonality between the theories for acoustic and optical positioning/shaping methods. Using this theoretical framework, we developed a simple engineering estimation scheme to predict the acceleration per unit intensity. The radiation pressure is achieved by interaction of electromagnetic waves and particles of a given dielectric material and size. The theory was limited to the Rayleigh domain, where particle size is much less than the wavelength, and isotropic scattering could be assumed. With this theoretical framework in hand, we now consider how electromagnetic waves could be utilized in a Space-based construction project. In the test case project, the question of how to construct a safe radiation shelter for humans, in the Near-Earth Object (NEO) region is considered. NEO material, pulverized to an average particle size of 0.1m radius, is formed into desired shapes using the radiation pressure and gradient forces experienced by dielectric objects in a standing-wave field of radio waves. The force field is produced by solar-powered transmitter/antenna carrying spacecraft, which are positioned in formation around the particle cloud to set up a resonant field of the desired mode. As a test case, formation of cylindrical shells is considered. The field level is set to induce an average particle acceleration of a millionth of an Earth-surface gravitational acceleration. Once in position, the particles are fused by solar-powered energy beams through a sintering process. Results show that 50m diameter, 50m-tall cylinders can be formed in the course of 12 to 13 hours per cylinder. Order-of-magnitude arguments show that the selected acceleration level is adequate to overcome noise from all other forces in this region. The paper also begins the consideration of tradeoffs between solar collector area, number of resonators, and capacitive storage-discharge of energy in the fabrication process.