Analysis and simulation of nominal mission scenarios of suborbital vehicles

In the recent years, the commercial space transportation has gained considerable attention. The inaugural suborbital launch with horizontal take-off and landing of Virgin Galactic’s WhiteKnight Two (WK2) / SpaceShipTwo (SS2)”Unity” system occurred in September 2016. Following this first flight test, a series of further tests were conducted until the first commercial suborbital launch occurred in June 2023 at Spaceport America in New Mexico (USA). This marks the advent of a new era in commercial space transportation in the context of the New Space Economy. This thesis was conducted in collaboration with ENAC (the Italian National Civil Aviation Authority) with the aim of conducting preliminary investigations into the potential operations of future suborbital vehicles within the Italian territory. In particular, this work aims at identifying few feasible mission options from the representative environment of Grottaglie Airport, in southern Italy, during nominal conditions. To achieve this goal, it is important to simulate the nominal situation within a proper mission analysis, characterising the aerodynamic and propulsive performance of a suborbital vehicle system. A multi-fidelity approach is adopted to allow a fast and agile assessment of these characteristics, followed by more accurate analyses. In accordance with this rationale, a preliminary aerodynamic database is constructed, without having access to a three-dimensional computer-aided design (CAD) model of the vehicles, through the application of analytical semi-empirical models. These models, which are already available in the literature and specifically address high-speed vehicles, are compared and properly customised in order to more accurately capture the peculiarities of the specific case study. In particular, the preliminary aerodynamic model that were investigated included: a model that implemented Raymer’s method; a model that implemented the Prandtl’s Lifting-line Theory; the use of Digital DATCOM Software. These three models provided three outputs, which were suitably compared to each other, and finally only one of these models was adopted. Four distinct aerodynamic databases are generated with the objective of capturing the full range of configurations of a vehicle’s system, representative of the WhiteKnightTwo/SpaceShipTwo configuration: the mated configuration, where the carrier aircraft and suborbital spaceship are mechanically joined; the carrier aircraft standalone; the suborbital spaceship un-feathered; the suborbital spaceship feathered (to decelerate the aircraft during the re-entry phase). In addition, the propulsion database for the carrier aircraft is generated using a propulsion model based on the Mattingly approach, which is specific to separate exhaust-stream turbofan engine. On the other hand, for the hybrid rocket motor of the suborbital spaceship, the data found in literature were sufficient for our simulations. The final aerodynamics and propulsive databases capture the variation of aero-propulsive characteristics of the reference vehicles at different speeds, angles of attack and altitude conditions. These databases are then used to run multiple mission studies using the commercial software ASTOS. In order to identify possible trajectories for the mission, it was necessary to conduct a survey of the area surrounding the airport. By studying the population density, it was possible to identify potential overland corridors for the take-off and re-entry of the suborbital vehicle system.