The purpose of this activity was to develop a roadmap for the next phase of SABRE development, focused on flight testing of SABRE propulsion elements, leading to the potential to flight test an integrated SABRE engine, and to assess the potential competitive position of SABRE powered systems in the future transportation segment.

The Synergetic Air-Breathing Rocket Engine (SABRE) has the potential to allow the development of space launch systems which provide a step change in reusability, reliability and cost-per-kg to orbit. Whilst ground based development of SABRE core engine and rocket elements is progressing, flight testing of the SABRE nacelle elements is seen as most appropriate approach to raising their TRL to allow acceptable risk flight testing of an entire SABRE propulsion unit.

A range of concept options to provide a staged approach to flight testing of SABRE propulsion elements up to a target condition of Mach 5/25 km have been generated and their advantages/disadvantages defined with consideration of aspects including safety, reliability and control.  Significant commonality in design, development and verification steps between options has been recognised and most options also allow for associated airframe technology advancement.

An analysis of the future space transportation market 2030+ and potential for SABRE-based systems within this been performed.  This has indicated that transportation to orbit of small satellites is likely to be the most significant sector to target with a SABRE-based system but there are opportunities in other sectors.

SABRE propulsion would allow the development of fully re-usable, horizontal take-off and landing, Single- or Two Stage To Orbit launch vehicles powered by a single engine, operating in air breathing mode up to 25 km/Mach 5 and only requiring an on-board oxidizer for operation in rocket mode beyond that point. 

A quantitative assessment of options for flight testing SABRE propulsion is being planned. This will allow concept selection and development to a stage where funding for flight testing to Mach 5/25 km can be sanctioned and allow target TRL achievement towards a SABRE-based space transportation system.