Phase 4 - A full-scale, modified X-24A shape with active vehicle controls and a parachute recovery system. This vehicle will be accelerated to the target altitude and speed with either a rocket booster or a high-altitude balloon. Space-qualified hardware in the eventual spacecraft layout will be used to the maximum extent possible.

1. Demonstrate free-flight vehicle stability and control characteristics in the supersonic, transonic, and subsonic flight regimes.

2. Demonstrate free-flight vehicle energy management and positioning capabilities.

3. Demonstrate the operation of space-qualified systems in the vehicle.

4. Continue the assessment of system reliability.

5. Refine landing flare techniques.