According to the report:
“This study was tasked with the purpose of conducting a thorough literature and program search to carry out and document a technical assessment of the latest concepts in science and engineering that show promise of leading to a major advance in Earth-to-orbit (ETO) propulsion. The study also reviewed and evaluated a select number of credible far-term breakthrough propulsion physics concepts pertaining to R&D work done on or related to gravity/inertia modification, spacetime metric modification, and the extraction of energy from the space vacuum environment. The results of the study are presented and summarized in this report. A combined bibliography of advanced propulsion references was assembled and is presented.
The report includes an overview of the recent history and present state-of-the-art of ETO launch vehicle and propulsion concepts. Also included is an outline and summary of the criteria and operative guidelines that the author used to examine, select and recommend advanced propulsion concepts. The author identified and selected five promising advanced propulsion concepts, and provides a detailed technical evaluation of their breakthrough potential for ETO propulsion.”