It’s a sci-fi concept that’s at the center of a 25-year exploratory project: building a hypersonic aircraft that takes off from the runway and doesn’t need a rest, inspection or repair after it lands — unlike the space shuttle — but can zip back around the world within an hour’s landing. Researchers are developing the validation metrics that could help predict the success or failure of such a model before it is even built, as test data becomes available from component, to sub-system, to the completely assembled air vehicle.