The objectives of the GTX ( Vertical Take - off/ Horizontal Landing reusable single - stage - to - orbit system ) project this viewgraph presentation summarizes include the following : ( 1 ) Determine whether or not air - breathing propulsion can enable reusable single stage to orbit vehicles ; ( 2 ) Provide validated system performance data , and a baseline system design ; and ( 3 ) Develop technologies applicable to high - speed airbreathing propulsion