Space Shuttle stronauts never experience more than 3 g's. The Falcon HTV-2 used a Minotaur IV Lite rocket in order to reach Mach 20 and the altitude needed for the test. This rocket is a modified Peacekeeper ICBM. The number of g's a person would be subjected to depends on the acceleration provided to the vehicle by the rocket. I wasn't able to find the average acceleration rate for the Minotaur IV Lite specifically, nor any benchmarks I could use to calculate it, but I did find benchmarks for the regular Minotaur IV rocket with a 1022 kg payload - I'm not going to bother deducting the effect this has. (
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The first three stages (the rocket is divided into separable parts that are removed as they empty of fuel - the Lite-version only has three stages, where the regular version has four) of the rocket provided an average acceleration rate of 39,56 m/s^2. This is equal to 4 g's. The peak g-force exposure takes place in the 3rd. stage where the rocket reaches an average rate of acceleration of approximately 48,77 m/s^2 over 55 seconds - this is roughly equal being exposed to 5 g's for 55 seconds. This means that with the right suit a human could be placed on the HTV-2 and not be injured - given that it doesn't crash into the ocean again.