speed record set by scramjet - fair?

Peter Duniho wrote:
Robert Briggs wrote:

Peter, your grasp of the physics of the matter seems to be substantially
better than Don's (not that that is difficult), but I don't buy the bit
about "the scramjet [being] the *entire* source of the speed".

Todd's interpretation of my statement was exactly correct. This particular
scramjet had limited fuel available, and all scramjets have the limitation
that they only operate in supersonic flight. These limitations forced the
use of a bomber and support rocket. But the thrust generated *exceeded*
that provided by the rocket, which is why the scramjet was able to
accelerate after being released from the rocket.

Right.

The flight is a *proof-of-concept* for something which would require at
least one non-scramjet engine type to make a self-contained system.

Yes, it has always been understood that a scramjet by itself is not very
useful, since it can't be used from a standing start.

Agreed.

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.

"Robert Briggs" wrote in message
...
[...]
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

Peter Duniho wrote:
Robert Briggs wrote:

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.

I'm not convinced, but we seem to be disagreeing about semantics,
rather than about aeronautics.

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.

Sufficiently powerful to accelerate the test vehicle from 0 mph to
Mach 10, yes; actually capable of doing it, no because of the nature
of the beast.

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.

The scramjet (with the aerodynamics and structural integrity of the
test vehicle) sets the *possible* final speed, but the bomber and
the rocket make an essential contribution to getting there.