Rocketdyne are revealing a little more information.
Lockheed and Aerojet Rocketdyne have developed a proprietary method to use an off the shelf F100 or F110 fighter engine, and accelerate it for short periods beyond M2.2 at which point the Scramjet lights (not surprisingly they won't reveal the ignition speed). They say they're ready to go, and all they have to counter now is the perception that hypersonics are unfeasibly expensive or too technically hard.
My boy met Rich Graham at Duxford next to the SR71 when he launched his book. It's still a spooky, alien looking jet in the flesh, even now.
Have devoured Ben Rich's and Bill Sweetman's books and followed hypersonic efforts for years, this is a very significant announcement.
Optionally manned, and optionally armed.
Imagine the challenges of weapon release travelling at 2kms a second.