Feasibility Study of a Technological Demonstrator of Reduced Size for Sub-Orbital Flight

The Unmanned Space Vehicles program (USV), managed by the Italian Aerospace Research Centre (CIRA), is a science and technology knowledge development program, oriented towards future generations of Reusable Launch Vehicles, capable of performing frequent, and affordable launches into space. The USV program has been defined based on the belief that future space access and re-entry will be guaranteed by aviation-like vehicles. The USV program therefore aims at the development of innovative technologies for future space vehicles. The program pursues an approach characterized by increasing mission complexity: three Flying Test Beds (FTBs) will be designed and built to perform four experimental flight tests. The planned missions are: Dropped Transonic Flight Test (DTFT), Sub-orbital Re-entry Test (SRT), Hypersonic Flight Test (HFT) and Orbital Re-entry Test (ORT). As these FTBs are thought as vehicles of considerable size, about 7.5 meters long, the study and development of smaller technological demonstrators, conceived to lead to the realization of bigger ones, appear attractive thanks to their high benefit-to-cost ratio. The aerospace system research group at Politecnico di Torino has been working at the design of small and affordable technological demonstrators for many years now and different configurations have been developed. In collaboration with CIRA, Università di Napoli “Federico II” and Università di Roma “La Sapienza”, our research group has carried out the feasibility study of a small vehicle oriented towards the execution of the SRT mission. The vehicle has been called “Mini-FTB” and its mission “Mini-SRT“. The CIRA demonstrator for the original SRT mission (FTB_2) is powered by one solid rocket engine. It will be dropped from a stratospheric balloon at an altitude of about 35 km. After that, the rocket is ignited to accelerate the vehicle along a sub-orbital trajectory up to a maximum altitude of about 120 km. Then the vehicle starts the re-entry phase along a trajectory designed to maximize heat fluxes, that remain higher than 650 kW/sqm for about 15 seconds, achieving the maximum value at about 25 km. A parachute system allows the recovery of the vehicle. Main target of the Mini-SRT mission is to improve technological and scientific knowledge useful to reduce risks connected to the SRT mission by means of a low cost and thus low risk system. The paper starts with an overview of the design process and the proceeds with the description of requirements, mission profile and system configuration. The paper then focuses on subsystems sizing and investigate the aerothermodynamics issue. Eventually preliminary cost estimations are show and main conclusions are drawn. Results are encouraging as the feasibility study has shown that the Mini-FTB can be built and tested.