Feasible options for point-to-point passenger transport with rocket propelled reusable launch vehicles

Abstract

For the first time in spaceflight history the flight of a fully reusable launch system with rocket propulsion appears possible within the next couple of years. Apart from the implications for the orbital launch market, a fully reusable system could also enable an entirely new class of commercial point-to-point transport on Earth. Rocket propelled point-to-point systems promise the ability to transport passengers or cargo to any suitable landing site on Earth with extremely short travel times (typically less than 90 min). In this study the primary focus is on DLR-SART's SpaceLiner 7 vehicle concept with an initial comparison to Starship, currently being developed by SpaceX.The trajectories are identified using multi-objective optimization with evolutionary algorithms. These allow the identification of a solution space with regard to multiple objectives, in this case minimal overflight of populated areas and minimal peak heat flux, while still respecting other constraints (e.g. structural loads). The population disturbance is computed by using a global population density database and integrating the number of people along the flight track. Ideally, the solution space consists of a pareto-front which correlates to the most optimal solutions possible for all objectives.The mission analysis identifies various feasible trajectories around the world. Primarily, these routes are going along less populated areas such as the oceans and the polar regions. Especially the latter enable large longitudinal changes during the flight and consequently connecting distant places on Earth. The critical routes are large longitudinal crossings around the equator where land masses must be overflown. These shall be reconsidered and/or improved in the future.Comparing SpaceLiner to Starship, it is found that the mission profiles vary significantly. While SpaceLiner uses its high lift-to-drag ratio in the higher atmosphere to manoeuvre around large land masses, Starship can only follow the direct route. In contrast, Starship flies higher into space and thereby might avoid having large population disturbances on ground. Only the re-entry and landing are critical as it does not have significant cross range capability. As a design option for the next iteration of the SpaceLiner development, SpaceLiner 8, it is planned to assess the possibility of using a smaller wing to follow a similar coast through space like Starship and have a steep re-entry at the end of the flight instead of a prolonged glide.