Given the exceptionally integrated nature of hypersonic vehicles, ground tests are VERY close to the full system operation

• Many (to all) subsystem included: cooling, transition, control, etc.
• Flow conditions close to reality: Mach, Re number, etc.
• Mockup size and materials are typically the same as in the real device
• Advantage: unstart can be triggered and controlled

However ground tests cannot reproduce all flight conditions

• Flight trajectory uncertainty: i.e. angle of attack
• Environment: altitude effects, etc.
• Disadvantage: in-flight unstart might be recorded without evidence of the causes

The classic “prediction” problem

• Predictions are requested outside of the domain of validation
• Crucial role of UQ procedures
• Use two independent approaches for building confidence in the predictions     (see UQ session)