Analysis of Active Rubidium Photo-Ionization Concept for Spacecraft Shielding from High Energy Neutral Beams
Abstract
Recently, a new beamed propulsion concept based on self-guiding of combined laser and particles beams has been proposed for interstellar travel. By firing high velocity neutral rubidium atoms at the spacecraft, speeds up to 7.5\% the speed of light could be achieved. One hurdle this project must overcome is how to protect the spacecraft from damage caused by collisions with the high speed particles. A proposed solution is to have the spacecraft generate a magnetic field and have the particles interact with this field rather than the spacecraft directly. Before the particles can be stopped and redirected by the magnetic field, however, they must first be ionized. This thesis details a modeling study of a two-step photo-ionization process as a means to ionize the incoming flow. To analyze this approach, radiative processes, beam divergence, beam attenuation, and laser/absorption lineshapes were all considered. Additionally, an iterative method was developed to overcome a boundary condition problem that arose due to the unique layout of this mission concept. The final model predicts the percentage of particles that will be ionized before impacting the spacecraft given various mission input parameters. The initial results showed that with realistic mission parameters the percentage of particles that would be ionized before reaching the spacecraft was too low to adequately protect the spacecraft. The cause for the low ionization percentage was found to be low efficiency ionization using the proposed two-step photo-ionization process. A subsequent study was conducted on alternative ionization schemes using the high energy Rydberg states of the rubidium atom. The results of this study showed that using the Rydberg states could lead to a much more efficient ionization process which in turn could lead to the majority of particles being ionized and stopped by the magnetic field.
Citation
Jillapalli, Rohan David (2021). Analysis of Active Rubidium Photo-Ionization Concept for Spacecraft Shielding from High Energy Neutral Beams. Undergraduate Research Scholars Program. Available electronically from https : / /hdl .handle .net /1969 .1 /194399.