"Robert Briggs" wrote in message
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[...]
I simply think that your wording about "the scramjet [being] the
*entire* source of the speed", rather than its being "sufficiently
powerful to complete the acceleration to Mach 10" (or something to that
effect) is a tad loose.

It is the entire source of the speed. Had the scramjet not been operating
when it disconnected from the rocket, it would have quickly slowed to
subsonic speed and of course would eventually have come to a complete stop.
The speed of the rocket simply ensured proper operation of the scramjet
engine...in the end, it's contribution to the final speed of the scramjet
vehicle is irrelevant.

An engine sufficiently powerful to accelerate the test vehicle from Mach 9
to Mach 10 is sufficiently powerful to accelerate the test vehicle from 0
mph to Mach 10. There's nothing loose about that statement at all, and it's
perfectly correct. The rocket used to launch the scramjet has nothing to do
with how powerful the scramjet is, or its final speed. Only the scramjet
itself does.

Pete